JP5704448B2 - Paperboard manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing paperboard.

  As the neutral sizing agent for papermaking, rosin type, alkenyl succinic anhydride type (hereinafter referred to as ASA type), alkyl or alkenyl ketene dimer type (AKD type) are usually used. In particular, in the paperboard system, a rosin-based so-called neutral rosin sizing agent is generally used. This is because the alkenyl succinic anhydride sizing agent has a serious problem in operability due to soiling of paper making tools, and the AKD system does not exhibit the desired sizing effect immediately after paper making, especially in the paperboard system, so-called sizing effect rises. Rosin sizing agents are frequently used because of the slow problem. However, in recent years, the neutralization of papermaking pH has advanced and the price fluctuation of rosin, which is a natural product, has been large. Therefore, ASA-based sizing agents and AKD-based sizing agents are also used in paperboard systems, and no aluminum sulfate is added. Alternatively, only a very small amount has been proposed, and a production method using an ASA-based sizing agent that reduces the contamination of papermaking tools has been proposed (see Patent Documents 1 to 3).

However, the ASA sizing agent still has the problem of soiling of the paper making tool because it volatilizes in the dryer part and produces a calcium salt of alkenyl succinic acid having strong adhesiveness in the paper making system. Further, when the amount of aluminum sulfate used is reduced, there is a problem that the effect of the polyacrylamide-based paper strength agent cannot be sufficiently obtained in a paperboard that requires high strength even though a lot of used paper is used. On the other hand, basic polymers having bicarbonate ions and amino groups derived from calcium carbonate are effective for improving the start-up property of AKD sizing agents. Especially, polyamidoamine epichlorohydrin modified products and diallyldimethylammonium chloride and acrylamide are effective. It is known that the improvement effect of such a copolymer is high (Non-patent Document 1).

Further, an alkyl ketene dimer sizing agent using a copolymer (A) of (meth) acrylamide and diallylamine or a salt thereof as a dispersant has been proposed (see Patent Document 4), but (meth) acrylamide and diallylamine or a salt thereof is proposed. When a copolymer with the above was used as a dispersant, there was a problem that a stable dispersant could not be obtained. In addition, when the AKD sizing agent contains waste paper and further contains a certain amount or more of aluminum, or in the case of a paperboard to which calcium carbonate that promotes size development is not added, the size development is weakened, and the polyamidoamine epithelium is reduced. Even when a chlorohydrin modified product or the like is used, there is a problem that the start-up is slow.

JP 2006-052506 A JP 2007-113126 A JP 2007-186822 A Japanese Patent Laid-Open No. 06-299494

Nordic Pull and PaperResearch Journal P.202 Vol23No.2 (2008)

An object of this invention is to provide the method of manufacturing the paperboard which has a favorable sizing property and favorable standup property, even when using the pulp which contains many aluminum components, or when calcium carbonate is not added.

As a result of intensive studies, the present inventor has found that the above problem can be solved by using a specific acrylamide compound and a ketene dimer sizing agent.

That is, the present invention relates to a (meth) acrylamide copolymer (A) and a ketene obtained by polymerizing a polymerization component (a) containing at least (meth) acrylamide (a1) and a diallylamine compound or a salt thereof (a2). Using a dimer sizing agent (B), a paperboard for making a raw material pulp containing aluminum atom at 1 wt% or more in terms of aluminum sulfate and 16 hydrate with respect to the dry weight of the raw material pulp including waste paper pulp at pH 6-8 It relates to a manufacturing method.

According to the present invention, it is possible to produce a paperboard having a good rising property even when a pulp containing a large amount of aluminum is used or when calcium carbonate is not added.

The present invention provides a polymerization component (a) containing at least (meth) acrylamide (a1) (hereinafter referred to as component (a1)) and a diallylamine compound or a salt thereof (a2) (hereinafter referred to as component (a2)). (Meth) acrylamide copolymer (A) (hereinafter referred to as component (A)) obtained by polymerizing (hereinafter referred to as component (a)) and ketene dimer sizing agent (B) (hereinafter referred to as (B). ) Component)) (however, a cation-modified acrylamide polymer by Hofmann decomposition reaction is not used) , and the aluminum atom is converted to aluminum sulfate / 16 hydrate by 1 weight with respect to the dry weight of raw pulp including waste paper pulp. The raw material pulp containing at least% is made at pH 6-8. In addition to component (A) and component (B), raw material pulp includes aluminum sulfate 16 hydrate (C) (hereinafter referred to as component (C)), and an amphoteric polyacrylamide paper strength enhancer having a branched structure ( In addition to D) (hereinafter referred to as component (D)), known additives may be used.

  The raw material pulp used in the present invention contains waste paper pulp, and contains aluminum atoms in an amount of 1% by weight or more in terms of aluminum sulfate · 16 hydrate based on the dry weight of the raw material pulp. Used paper pulp includes corrugated paper, magazine waste, bookbinding, printing factories, cutting offices, cutting papers, stripped paper, widened waste paper, and unprinted waste paper such as white, white, medium white, and white loss. Used paper pulp, high-quality paper, high-quality coated paper, medium-quality paper, medium-quality coated paper, reprinted paper, etc. Oil-based ink, waste paper written with a pencil, pulp that has been deinked after disaggregation of waste newspaper, and the like can be used. In addition to waste paper pulp, various mechanical pulps and / or chemical pulps can be used alone or in admixture of two or more. The content of waste paper pulp is not particularly limited, but is usually about 60 to 100% by weight.

As the component (a1), acrylamide and methacrylamide can be used.

As the component (a2), diallylamine or a salt thereof can be used. Diallylamine is a compound represented by the general formula (1): R ¹ R ² NR ³ , wherein R ¹ and R ² are allyl groups (CH ₂ ═CHCH ₂ —) or methallyl groups (CH ₂ ═C (CH ₃ )). CH ₂ —), and R ³ is a compound having 1 to 4 carbon atoms or a hydrogen atom. R ¹ and R ² may be the same or different. Specific examples of the component (a2) include diallylamine, diallylmethylamine, diallylethylamine, diallylbutylamine, and dimethallylamine. Examples of the diallylamine salts include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid, and organic acid salts such as formic acid, acetic acid, and propionic acid. In addition, these may be used individually by 1 type, or 2 or more types may be mixed and used for them.

The component (a) includes an anionic monomer (a3) (hereinafter referred to as component (a3)), a cationic monomer (a4) (hereinafter referred to as component (a4)), a nonionic monomer (as required). a5) (hereinafter referred to as component (a5)) or the like.

The component (a3) is not particularly limited as long as it is a monomer having an anionic functional group and one radical polymerizable functional group, and a known one can be used. Examples of the anionic functional group include a carboxyl group, a sulfonic acid group (—SO ₃ H), and a phosphoric acid group (—O—P (═O) (OH) ₂ ). Specifically, examples of the carboxyl group-containing monomer include (meth) acrylic acid, crotonic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, muconic acid, and citraconic acid. Examples of the sulfonic acid group-containing monomer include vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, and 2-acrylamido-2-methylpropane sulfonic acid. As the phosphoric acid group-containing monomer, mono (2-acryloyloxyethyl) acid phosphate, mono (2-methacryloyloxyethyl) acid phosphate, diphenyl (2-acryloyloxyethyl) phosphate, diphenyl (2-methacryloyloxyethyl) phosphate, Phenyl (2-acryloyloxyethyl) phosphate, acid phosphooxyethyl methacrylate, methacryloyl oxyethyl acid phosphate monoethanolamine salt, 3-chloro-2-acid phosphooxypropyl methacrylate, acid phosphooxypolyoxyethylene glycol Monomethacrylate, acid phosphooxypolyoxypropylene glycol methacrylate, (meth) acryloyloxyethyl acetate Phosphate, (meth) acryloyloxypropyl acid phosphate, (meth) acryloyloxy-2-hydroxypropyl acid phosphate, (meth) acryloyloxy-3-hydroxypropyl acid phosphate, (meth) acryloyloxy-3-chloro-2-hydroxy Examples thereof include propyl acid phosphate and allyl alcohol acid phosphate. These anionic functional groups may be alkali metal salts such as sodium salt and potassium salt, and ammonium salts with ammonia and amines. These monomers may be used alone or in combination of two or more.

The component (a4) is a monomer having a cationic functional group and one radical polymerizable functional group, and is not particularly limited as long as it is other than the component (a2), and a known one is used. be able to. Examples of the cationic functional group include a primary amino group, a secondary amino group, and a tertiary amino group. Specific examples thereof include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminopropyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, and diethylaminopropyl (meth). Examples include acrylamide and allylamine. In addition, these cationic functional groups may be salts of inorganic acids or organic acids such as hydrochloric acid, sulfuric acid, formic acid, and acetic acid. Further, a part or all of the tertiary amino group may be converted to a quaternary ammonium ion with a quaternizing agent. Examples of the quaternizing agent include alkyl halides such as methyl chloride and methyl bromide, arylalkyl halides such as benzyl chloride and benzyl bromide, dimethyl sulfate, diethyl sulfate, epichlorohydrin, 3-chloro-2-hydroxypropyltrimethyl. Ammonium chloride, glycidyl trialkyl ammonium chloride, etc. are mentioned. These monomers may be used alone or in combination of two or more.

The component (a5) is not particularly limited as long as it is a monomer having one radical polymerizable functional group other than the component (a3) and the component (a4), and a known component can be used. Specific examples include esters of alcohols such as alcohols having 1 to 8 carbon atoms with acrylic acid or methacrylic acid, (meth) acrylonitrile, styrene, styrene derivatives, vinyl acetate, vinyl propionate, methyl vinyl ether, and the like. It is done. These monomers may be used alone or in combination of two or more.

  Moreover, a crosslinkable monomer (a6) (henceforth (a6) component) can also be used for (a) component as needed. The component (a6) is not particularly limited as long as it has at least two radically polymerizable functional groups, and known components can be used. Specifically, for example, di (meth) acrylates such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, glycerin di ( (Meth) acrylate, trimethylolpropane / ethylene oxide adduct triacrylate, methylenebis (meth) acrylamide, ethylenebis (meth) acrylamide, hexamethylenebis (meth) acrylamide, N, N'-bisacrylamideacetic acid, N, N'- Bis (meth) acrylamides such as methyl bisacrylamide, N, N-benzylidenebisacrylamide, divinyl esters such as divinyl adipate and divinyl sebacate, epoxy acrylate , Urethane acrylates, allyl (meth) acrylate, diallyl phthalate, diallyl malate, diallyl succinate, diallylacrylamide, divinylbenzene, diisopropylbenzene, N, N-diallylmethacrylamide, N-methylolacrylamide, diallyldimethylammonium, diallyl Bifunctional monomers such as chlorendate, glycidyl (meth) acrylate, 1,3,5-triacryloylhexahydro-S-triazine, triallyl isocyanurate, N, N-diallylacrylamide, triallylamine, triallyl trimellitate Trifunctional monomers such as tetramethylol methane tetraacrylate, tetraallyl pyromellitate, N, N, N ′, N′-tetraallyl-1,4-diaminobutane, tetra Riruamin salts, tetrafunctional monomers such as tetraallyloxyethane and the like.

  The component (A) is obtained by polymerizing polymerization components having the components (a1) and (a2) as essential components. The amount of component (a1) and component (a2) used is usually 60 to 95 mol% for component (a1) and 5 to 40 mol% for component (a2).

The components (a3) to (a6) are optional components, and the amount used is not particularly limited. Usually, the component (a3) is 0 to 10 mol%, the component (a4) is 0 to 10 mol%, ( Component a5) can be used in an amount of 0 to 30 mol%, and component (a6) in an amount of 0 to 1 mol%. In addition, it is preferable to use the component (a1), the component (a2), and the component (a3) from the viewpoint of high fixability, the component (a1) is 65 to 89.5 mol%, and the component (a2) is 10 to 30. It is preferable to make a mol% and (a3) component into 0.5-5 mol%.

  The component (A) can be obtained by polymerizing the component (a). (A) The polymerization method of a component is not specifically limited, A well-known radical polymerization method is employable.

As the component (B) used in the present invention, alkyl ketene dimers and alkenyl ketene dimers can be used. Specifically, for example, the general formula (2):

(In the formula, R ⁴ and R ⁵ are a C8-C30 saturated hydrocarbon group or a C8-C30 unsaturated hydrocarbon group, and R ⁴ and R ⁵ may be the same or different.) The compound represented by these can be used. In the general formula (1), the hydrocarbon group of R ⁴ or R ⁵ is, for example, an alkyl group such as octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, octenyl, decenyl, dodecenyl, tetradecenyl, hexadecenyl, octadecenyl, An alkenyl group such as eicosenyl, a substituted phenyl group such as octylphenyl, nonylphenyl, and dodecylphenyl; a substituted cycloalkyl group such as nonylcyclohexyl; and an aralkyl group such as phenylethyl. Among these, a C10 to C25 saturated hydrocarbon group and a C10 to C25 unsaturated hydrocarbon group are preferable, and a C14 to C22 saturated hydrocarbon group and a C14 to C22 unsaturated hydrocarbon group are particularly preferable. R ⁴ and R ⁵ are not limited to linear hydrocarbons, and may be branched or cyclic. Examples include octadecyl ketene dimer, hexadecyl ketene dimer, tetradecyl ketene dimer, and dodecyl ketene dimer. The ketene dimer may be a dimerized mixture of different fatty acids. Usually, the component (B) may be emulsified by a known method to obtain an emulsion. In emulsification, for example, cationized starch, sodium lignin sulfonate, or a formalin condensate of sodium naphthalene sulfonate can be used as an emulsifying dispersant. Although the usage-amount of an emulsification dispersing agent is not specifically limited, About 5 to 50 weight% is normally used by solid content with respect to 100 weight part of ketene dimers which are emulsification objects. The emulsification method is not particularly limited and may be a known method, but a forced emulsification method using a high-pressure homogenizer is preferable.

Although the usage-amount in the case of using (C) component is not specifically limited, Usually, it is preferable to add 0.5 to 2.0 weight% to raw material pulp (dry weight). This range is preferable because the effect of the paper strength enhancer is improved, and as a result, the drainage, yield, and dry paper strength enhancing effects are improved.

(D) It does not specifically limit as a component, A well-known thing can be used. The component (D) may be a commercially available product, but can also be obtained by copolymerizing (meth) acrylamide, an anionic monomer, a cationic monomer, a crosslinkable monomer, and if necessary, a nonionic monomer. The anionic monomer is the same as the component (a3), the cationic monomer is the same as the component (a4), the crosslinkable monomer is the same as the component (a6), and the nonionic monomer As, the same thing as said (a5) component can be used. Although the usage-amount of (meth) acrylamide, anionic monomer, a cationic monomer, and a crosslinking monomer is not specifically limited, Usually, (meth) acrylamide is 59-98 mol%, anionic monomer is 1-20 mol%, and it is cationic. The monomer may be used in an amount of 1 to 20 mol%, and the crosslinkable monomer may be used in an amount of 0 to 1 mol%. Moreover, what is necessary is just to use 0-30 mol%, when using a nonionic monomer. In particular, 86.9 to 97 mol% (meth) acrylamide, 1 to 5 mol% anionic monomer, 2 to 10 mol% cationic monomer, and 0 to 0.1 mol% crosslinkable monomer were copolymerized. It is preferable to use one. The copolymerization may be performed by a known method. Although the molecular weight of (D) component is not specifically limited, Usually, it is preferable that a weight average molecular weight (by the light-scattering method) shall be 500,000-5 million.

Although the addition method of (A) component and (B) component is not specifically limited, It is preferable to add (A) component simultaneously after adding (A) component and (B) component, or (B) component. It is preferable to add the component (A) and the component (B) at the same time because the yield of the component (A) and the component (B) is improved. Moreover, since the yield of (B) component improves by adding (A) component after addition of (B) component, it is preferable.

Although the usage-amount of (A) component and (B) component is not specifically limited, Usually, (A) component is 0.01-0.2 weight% with respect to the dry weight of raw material pulp, respectively, B) 0.05 component The use of ˜0.3% by weight is preferable because the intended effect can be obtained without excessive use of chemicals.

In the case of using the component (C) and the component (D), the addition method and the addition amount are not particularly limited. Usually, after the component (C) is added to the raw pulp, the component (D), (B) It is preferable to add the component and the component (A) in this order. By adding in this order, the paper strength, the size effect, and the rising speed of the size effect can be improved. In addition, although calcium carbonate may be added to the raw material pulp, it is preferable not to use calcium carbonate from the viewpoint of improving paper strength.

  Further, in the present invention, in addition to these, other additive chemicals such as cationic starch, amphoteric starch, carboxymethylcellulose and other polysaccharides, polyamide polyamine epichlorohydrin modified products, etc. A molecular weight polyacrylamide-based filtrate retention agent or the like can be used in combination as appropriate.

In the present invention, if necessary, it is possible to apply a liquid containing a surface sizing agent on the same paper machine on a paper sheet, and by carrying out the present invention, the drying property and the paper making speed after application can be improved. Paper with a modified surface can be produced without dropping. It does not specifically limit as a surface sizing agent to be used, A well-known thing can be used. Specifically, starch, polyacrylamide, polyvinyl alcohol and the like that improve paper strength, styrene / acrylic acid (methacrylic acid) copolymer, styrene / acrylic acid ester copolymer, or copolymers of these with other monomers. Aqueous solutions and emulsions made of polymers, styrene / maleic acid copolymers, olefin / maleic acid copolymers, vinyl acetate / maleic acid copolymers, copolymers with styrene / cationic monomers, and quaternized them. The thing which can improve water resistance, such as a thing, or can control the sliding of a surface can be mentioned, Each can be apply | coated individually or in combination of 2 or more types.

Examples of the paperboard obtained by the present invention include a linerboard obtained by combining two or more layers for corrugated paper, a water resistant core, a paper tube base paper, a coated white paperboard, a non-coated white paperboard, a chipboard paper, and the like. In the case of laminated paper, it is preferable to apply the present invention to the surface layer or the lower layer.

The paperboard suitably obtained by the present invention has a Cobb water absorption of 60 g / m ² or less within 1 hour from papermaking, and a Cobb water absorption of 2 after heat treating the paper at 125 ° C. for 15 minutes. Is less than double.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the examples and comparative examples, “parts” and “%” are based on mass unless otherwise specified.

Synthesis Example 1 (Production of diallylamine / acrylamide copolymer)
After charging 1330.0 parts of ion-exchanged water and 19.4 parts of diallylamine (0.2 mol) into a reactor equipped with a stirrer, thermometer, reflux condenser, nitrogen gas inlet tube and dropping funnel, 35% diluted The pH was adjusted to 7 with sulfuric acid. After removing oxygen in the reaction system through nitrogen gas, the mixture was heated to 70 ° C. and ion exchange water and 3.5 parts of ammonium persulfate were added. Next, 540.4 parts (3.8 mol) of a 50% aqueous acrylamide solution was added at 70 ° C. over 2 hours, and kept at 70 ° C. for 2 hours. After completion of the polymerization, ion-exchanged water was added to obtain an acrylamide copolymer (A) having a nonvolatile content of 15.5%, pH 3.7, and a viscosity (25 ° C.) of 2500 mPa · s.

Synthesis Examples 2 to 5 and Comparative Synthesis Example 1
In Synthesis Example 1, a polymer (A) was obtained in the same manner as in Synthesis Example 1, except that the types and usage ratios of the components were changed as shown in Table 1. In addition, when using together acrylic acid and itaconic acid, after adding to 50% acrylamide aqueous solution, 10% sodium hydroxide aqueous solution was added and it adjusted and used for pH7. The results are shown in Table 1.

* In the table, AM represents acrylic acid, DAA represents diallylamine, AA represents acrylic acid, ITA represents itaconic acid, and DADMAC represents N, N diallyldimethylammonium chloride.

Preparation Example 1 (Preparation of ketene dimer sizing agent)
80 parts of alkyl ketene dimer (derived from a mixture of 65% stearic acid and 35% palmitic acid) and 10% cationized starch paste (nitrogen content 0.50-0. 60%, 185 parts of oxidized starch cation-modified with glycidyltrimethylammonium chloride), 3.75 parts of 40% aqueous solution of anionic dispersant (naphthalenesulfonic acid formalin condensate, manufactured by Kao Corporation) and water 131. 25 parts were charged, heated to 80 ° C., predispersed with a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), and then added to a high-pressure homogenizer (APV.GAULIN) under the condition of 25 MPa at the same temperature. Dispersed through circulation. Immediately cool to 25 ° C., add water for concentration adjustment, 20% non-volatile content, viscosity 15 mPa · s (25 ° C.), pH 3.5 (25 ° C.), average particle size 0.8 μm ketene dimer system size Agent (B) was obtained.

Example 1
Corrugated waste paper (aluminum sulfate content: 2.8%) was added with tap water in an amount to make the pulp concentration 2.0%, and beaten to 380 ml Canadian Standard Freeness using a beater. The beaten pulp slurry was further diluted with tap water to adjust the pulp concentration to 1.5%. Aluminum sulfate (C), branched paper strength enhancer (Arakawa Chemical Industries, Ltd., Polystron 1222) (D), ketene dimer type sizing agent with respect to the solid content of the pulp slurry (pH = 7.5) (B) The polymers (A) obtained in Synthesis Examples 1 to 10 were added in the order and addition ratio (weight) shown in Table 2, and the paper machine (TAPPI) was added.
The paper was made with a Standard Sheet Machine (square type) so as to have a basis weight of 120 g / m ² . The hand-wetted wet paper was dehydrated with a roll press machine under conditions of a linear pressure of 5.5 kg / cm and a feed speed of 2 m / min. The wet paper was dried at 80 ° C. for 150 seconds using a rotary dryer. Cobb water absorption immediately after drying of the obtained test paper and after being cured for 15 minutes in a circulating dryer at 125 ° C. and conditioned for 24 hours in a constant temperature and humidity (23 ° C., 50% relative humidity) environment Was measured. The results are shown in Table 2. In addition, all the display of the addition rate displayed the solid content of each chemical | medical agent with respect to pulp solid content in percentage. For aluminum sulfate, 14-18 hydrate of the reagent was added as a solid content.

Examples 2-12, Comparative Examples 1-7
Paper was manufactured in the same manner as in Example 1 except that the order of use and the amount of each additive were changed as shown in Table 2. Table 2 shows the measurement results of ring crush strength and Cobb water absorption of the obtained paper.

(Test method)
(Water absorption test [Cobb method])
Cobb water absorption (g / m ² ) was measured in accordance with JIS P-8140. The contact time with water was 2 minutes.

(Quantitative determination of aluminum sulfate in pulp)
After diluting 50 g of 2% strength pulp slurry to 200 g with distilled water, the pH was adjusted to 1 with hydrochloric acid and stirred at 30 ° C. for 12 hours. After cooling, the pulp solids are allowed to settle through a centrifuge, and the aluminum ion concentration in the supernatant is measured with a fluorescent X-ray (wavelength dispersive X-ray fluorescence analyzer ZSX-100e (manufactured by Rigaku Corporation)). . From the obtained results, the amount of aluminum relative to the solid content of the pulp slurry was converted to the weight of aluminum sulfate · 16 hydrate and displayed.

(Ring crush strength)
In accordance with JIS P8126 paperboard compressive strength test method, indicated by specific compressive strength (ratio RC)

表中、Ａｌｕｍは硫酸アルミニウム、ＰＳは分岐型紙力増強剤（荒川化学工業（株）製、ポリストロン１２２２）、ＡＫＤは調製例1で得られたケテンダイマー系サイズ剤、ＰＡＥはポリアミドポリアミンエピクロロヒドリン樹脂（荒川化学工業（株）製 アラフィックス２５５）
、ＰＥＩはポリエチレンイミン（ＢＡＳＦ社製 ポリミンＳＫ）、ＰＶＡｍはポリビニルアミン（ＢＡＳＦ社製 カチオファストＶＦＨ）を表す。

In the table, Alum is aluminum sulfate, PS is a branched paper strength enhancer (manufactured by Arakawa Chemical Co., Ltd., Polystron 1222), AKD is the ketene dimer sizing agent obtained in Preparation Example 1, and PAE is polyamide polyamine epichloro Hydrin resin (Arakawa Chemical Industries, Ltd. Arafix 255)
, PEI represents polyethyleneimine (Polymine SK manufactured by BASF), and PVAm represents polyvinylamine (Cathiofast VFH manufactured by BASF).

Claims (10)

A (meth) acrylamide copolymer (A) obtained by polymerizing a polymerization component (a) containing at least (meth) acrylamide (a1) and a diallylamine compound or a salt thereof (a2) and a ketene dimer sizing agent (B ) (However, a cation-modified acrylamide polymer by Hofmann decomposition reaction is not used) containing 1% by weight or more of aluminum atoms in terms of aluminum sulfate / 16 hydrate based on the dry weight of raw pulp including waste paper pulp A method for producing paperboard, in which the raw material pulp is made at pH 6-8.   The method for producing paperboard according to claim 1, wherein 0.5 to 2.0% by weight of aluminum sulfate · 16 hydrate (C) is added to the dry weight of the raw material pulp containing waste paper pulp containing aluminum.   A (meth) acrylamide copolymer (A) obtained by polymerizing a polymerization component (a) containing at least (meth) acrylamide (a1) and a diallylamine compound or a salt thereof (a2) is converted into a ketene dimer sizing agent ( The method for producing a paperboard according to claim 1 or 2, which is added simultaneously with B) or after the addition of the ketene dimer sizing agent (B).   The paperboard according to any one of claims 1 to 3, wherein the polymerization component (a) containing at least (meth) acrylamide (a1) and a diallylamine compound or a salt thereof (a2) contains an anionic monomer (a3). Production method.   The board | substrate manufacturing method of Claim 4 in which anionic monomer (a3) contains a carboxyl group-containing monomer.   A (meth) acrylamide copolymer (A) and a ketene dimer sizing agent (B) obtained by polymerizing a polymerization component (a) containing at least (meth) acrylamide (a1) and a diallylamine compound or a salt thereof (a2) ) Is used in an amount of 0.01 to 0.2% by weight and 0.05 to 0.3% by weight, respectively, based on the dry weight of the raw pulp.   The method for producing paperboard according to any one of claims 1 to 6, wherein the amphoteric polyacrylamide-based paper strength enhancer (D) having a branched structure is used.   Raw material pulp aluminum sulfate 16 hydrate (C), amphoteric polyacrylamide paper strength enhancer (D) having a branched structure, ketene dimer sizing agent (B) and at least (meth) acrylamide (a1) and diallylamine type The method for producing a paperboard according to claim 7, wherein the (meth) acrylamide copolymer (A) obtained by polymerizing the polymerization component (a) containing the compound or a salt thereof (a2) is added in this order.   The manufacturing method of the paperboard in any one of Claims 1-8 which does not add calcium carbonate to raw material pulp. The obtained paperboard has a Cobb water absorption of 60 g / m ² or less within 1 hour from papermaking, and 2 times or less of the Cobb water absorption after the paperboard is heat-treated at 125 ° C. for 15 minutes. method for producing a paperboard according to any one of 1-9.