JP2007186821A - Method for producing paperboard and paperboard - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing paperboard, which is capable of avoiding scale trouble and pitch trouble in a paper making system. <P>SOLUTION: The method for producing paperboard comprises using a slurry of (1) pH 6.6 to 8.5, (2) 50-400 ppm alkalinity, and (3) 50-250 mS/m electric conductivity and making paper without adding (4) an internal sizing agent to the pulp slurry. When applying the method for producing paperboard, a paper-strengthening agent is preferably added, and an acrylic polymer and/or a starch is more preferably added as the paper-strengthening agent. And addition of a pitch control agent and/or a retention aid is also preferable. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a paperboard manufacturing method and a paperboard obtained by the manufacturing method, and more particularly to a paperboard manufacturing method and a paperboard capable of avoiding a scale trouble and a pitch trouble in a papermaking system.

  In general, when paperboard is made from used paper, the papermaking pH is made acidic with a sulfuric acid band. This is because the effect of a rosin sizing agent generally used can be obtained efficiently.

  However, in recent years, papermaking systems have been closed due to environmental problems, and machine corrosion due to accumulation of sulfate ions derived from sulfate bands has become a problem. In addition, the calcium carbonate content in waste paper has increased in recent years, and the pH of the papermaking system is unlikely to decrease, so the amount of sulfuric acid band used has increased. Due to this increase in sulfate ion and calcium carbonate content due to the closure, calcium sulfate (gypsum), which is the reaction product of the sulfate band and calcium carbonate, increases in the system, which causes scale trouble due to precipitation in the papermaking process. Has occurred frequently.

More recently, troubles due to synthetic pitches have increased in the papermaking process. Synthetic pitches are derived from ink vehicles carried from used paper, latexes used as binders for coated paper, adhesive materials used for gum tapes and labels, hot melt adhesives used as back glue for books and magazines, etc. It is a substance. The pitch adheres to the inside of the paper making apparatus and tools and causes water squeezing failure, paper breakage, and the like, thereby reducing paper productivity. In addition, the agglomerated pitch not only causes pinholes and picking on the paper surface, but also causes troubles during coating and printing, causing the paper quality to be significantly impaired.

  Currently, the papermaking pH generally used in the production of paperboard is 5 to 6.5. This is because the amount of sulfuric acid band added was reduced from the conventional acidic papermaking to avoid the above problem, and the papermaking pH was increased due to the increase in the content of calcium carbonate.

In order to avoid the above-described problems, use of a pitch control agent has been proposed. However, it has been insufficient to solve with only the pitch control agent.
U.S. Pat. No. 4,765,867

An object of the present invention is to provide a paperboard manufacturing method capable of avoiding scale troubles and pitch troubles in a papermaking system, and a paperboard obtained by the manufacturing method.

That is, the present invention
<1> (1) pH 6.5 to 8.5
(2) Alkalinity 50-400ppm
(3) Conductivity 50-250mS / m
Using pulp slurry of
(4) A method for producing paperboard, wherein papermaking is performed without adding an internally added sizing agent to the pulp slurry;
<2> A method for producing a paperboard of <1>, wherein a paper strength agent is added,
<3> The method for producing a paperboard according to <1> or <2>, wherein acrylamide polymers and / or starches are added,
<4> A method for producing a paperboard according to any one of <1> to <3>, wherein a pitch control agent is added,
<5> A method for producing a paperboard according to any one of <1> to <4>, wherein a yield agent is added,
<6> The method for producing a paperboard according to the above <1> to <5>, wherein no aluminum compound is used or 1% by weight or less based on the solid content of the pulp slurry;
<7> A method for producing a paperboard according to any one of <1> to <6>, wherein a surface paper strength agent and / or a surface sizing agent is used.
<8> An object of the present invention is to provide a paperboard obtained using the paperboard manufacturing method according to the above items <1> to <7>.

By the method of the present invention, it is possible to avoid scale trouble and pitch trouble in the papermaking system.

The invention is described in detail below.
<Paperboard>
Examples of the paperboard of the present invention include liner base paper, core base paper, paper tube base paper, gypsum board base paper, coated white board, uncoated white board, chip ball and the like. Among these, a core base paper and a liner base paper are preferable, and a core base paper is particularly preferable. The paperboard may be multi-layered, but in this case, at least one layer is also included in the present invention.

The method for producing the paperboard of the present invention comprises:
(1) pH 6.5-8.5
(2) Alkalinity 50-400ppm
(3) Conductivity 50-250mS / m
A paperboard manufacturing method characterized in that papermaking is performed using a pulp slurry of, and if it is in a range that satisfies all of these, it is possible to avoid scale troubles and pitch troubles in the papermaking system, but even if one is missing It becomes difficult to avoid scale trouble and pitch trouble. Further, (4) by not adding the internally added sizing agent to the pulp slurry, it is possible to reduce the pitch and foaming of the pulp slurry. The paperboard of the present invention may be made in a single layer or in two or more layers, but at least one layer needs to satisfy the above conditions.

The values of pH, alkalinity, and conductivity of the present invention are those measured with a pulp slurry immediately before forming a sheet. Specifically, for example, the values of pH, alkalinity, and electrical conductivity measured for pulp slurry in an ultraformer or a long net inlet or a pulp slurry in a round net vat.

The pH of the pulp slurry for papermaking is preferably pH 6.6 to 8.2, and more preferably 6.7 to 8.0. The pH as used in the field of this invention says what was measured on 25 degreeC conditions. In order to achieve the pH, a pH adjusting agent, for example, an alkaline substance such as sodium hydroxide or sodium carbonate, or an acidic substance such as sulfuric acid can be used. It is preferable to avoid the use that increases these fluctuations.

The alkalinity of the pulp slurry for papermaking is preferably 70 to 400 ppm, more preferably 80 to 300 ppm. The alkalinity referred to in the present invention refers to a part of the pulp slurry immediately before paper making, No. An indicator of ethanol solvent mixed with methyl red and bromocresol green is added to the filtrate obtained by suction filtration with 5A filter paper (manufactured by Toyo Filter Paper Co., Ltd.), and the filtrate is stirred while gently stirring the liquid. Titration is performed using 1 / 50N sulfuric acid until the color changes from blue to red, and the alkalinity amount in the filtrate is converted to calcium carbonate to determine the alkalinity (mg CaCO ₃ / l). The value obtained by the formula of titration (ml) × 1000 / filtrate (ml). For adjusting the alkalinity, carbonates such as sodium hydrogen carbonate and calcium carbonate, and alkaline substances such as sodium hydroxide and potassium hydroxide can be mentioned. However, it is necessary to adjust the pH and alkalinity to the above ranges. It is preferable to avoid the use in which the fluctuation of is large.

The electric conductivity of the pulp slurry for papermaking is 50 to 200 mS / m, more preferably 50 to 150 mS / m. The electric conductivity referred to in the present invention means a value measured at 25 ° C.

<Pulp slurry>
The pulp slurry is a slurry obtained by using a pulp raw material as a main raw material. As raw materials for pulp, bleached or unbleached chemical pulp such as kraft pulp or sulfite pulp, ground pulp, bleached or unbleached high-yield pulp such as mechanical pulp or thermomechanical pulp, upper white waste paper, newspaper waste paper, magazine waste paper, cardboard Any waste paper pulp such as waste paper or deinked waste paper can be used, and it is preferable to use 50% or more of waste paper pulp. Moreover, as said pulp raw material, the mixture of the said pulp raw material and polyamide, polyester, polyolefin, etc. can also be used. Furthermore, a filler is a main raw material used for pulp slurry. Examples of the filler include calcium carbonate, clay, talc, chalk, titanium oxide, and white carbon.

<Paper strength agent>
Examples of the paper strength agent added to the pulp slurry that can be used in the present invention include acrylamide polymers, starches, polyvinyl alcohols, and celluloses. Among these, acrylamide polymers and / or starches are preferably used.

  Examples of acrylamide polymers include (meth) acrylamide polymers obtained by polymerizing (meth) acrylamide and ionic vinyl monomers, and (meth) acrylamide polymers obtained by adding other monomers as necessary. Mention may be made of starch-grafted polyacrylamide polymers obtained by polymerizing acrylamide monomers in the presence of starch, acrylamide polymers by Hoffman modification, and acrylamide polymers by Mannich modification.

  (Meth) acrylamide is acrylamide or methacrylamide, and these can be used in a powder or an aqueous solution.

  The ionic vinyl monomer is a cationic vinyl monomer and / or an anionic vinyl monomer.

  Examples of the cationic vinyl monomer include a vinyl monomer having a primary amino group, a vinyl monomer having a secondary amino group, a vinyl monomer having a tertiary amino group, and a vinyl monomer having a quaternary ammonium salt.

  Examples of the vinyl monomer having a primary amino group include allylamine, methallylamine, and salts thereof. These salts include inorganic acid salts such as hydrochloride and sulfate, and organic acid salts such as formate and acetate.

  Examples of the vinyl monomer having a secondary amino group include diallylamine, dimethallylamine, and salts thereof. These salts include inorganic acid salts such as hydrochloride and sulfate, and organic acid salts such as formate and acetate.

  Further, as the vinyl monomer having a secondary amino group, vinyl monomers having the primary amino group such as allylamine and methallylamine, and alkyl halides such as methyl chloride and methyl bromide, benzyl chloride, and benzyl bromide are used. Examples thereof include monomers converted into secondary amine acid salts by reaction with aralkyl halides, dimethyl sulfate, dialkyl sulfates such as diethyl sulfate, epichlorohydrin and the like.

  Examples of the vinyl monomer having a tertiary amino group include dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethylaminopropyl acrylate, dimethylaminopropyl methacrylate, diethylaminopropyl acrylate, and diethylaminopropyl methacrylate. And dialkylaminoalkyl (meth) acrylamides such as dialkylaminoalkyl (meth) acrylates, dimethylaminopropyl acrylamide, dimethylaminopropyl methacrylamide, diethylaminopropyl acrylamide, and diethylaminopropyl methacrylamide, and salts thereof. it can. These salts include inorganic acid salts such as hydrochloride and sulfate, and organic acid salts such as formate and acetate.

  Further, as the vinyl monomer having a tertiary amino group, vinyl monomers having the secondary amino group such as diallylamine and dimethallylamine, and alkyl halides such as methyl chloride and methyl bromide, aralkyl such as benzyl chloride and benzyl bromide. Examples thereof include monomers converted into acid salts of tertiary amines by reaction with any one of halides, alkyl sulfates such as dimethyl sulfate and diethyl sulfate, and epichlorohydrin.

  Examples of the vinyl monomer having a quaternary ammonium salt include diallyldimethylammonium chloride, dimethallyldimethylammonium chloride, diallyldiethylammonium chloride, and diethyldimethallylammonium chloride.

  Examples of the vinyl monomer having a quaternary ammonium salt include a vinyl monomer obtained by reacting the vinyl monomer having a tertiary amino group with a quaternizing agent. Examples of the quaternizing agent include alkyl halides such as methyl chloride and methyl bromide, aralkyl halides such as benzyl chloride and benzyl bromide, alkyl sulfates such as dimethyl sulfate and diethyl sulfate, epichlorohydrin, 3-chloro- Examples include 2-hydroxypropyltrimethylammonium chloride and glycidyltrialkylammonium chloride.

  Specifically, acryloyloxyethyltrimethylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, acryloyloxyethyldimethylbenzylammonium chloride, methacryloyloxyethyldimethylbenzylammonium chloride, acryloyloxypropyldimethylbenzylammonium chloride, and methacryloyloxypropyldimethylbenzylammonium chloride Examples include chloride.

  These vinyl monomers having a primary amino group, a secondary amino group, a tertiary amino group, or a quaternary ammonium salt may be used alone or in combination of two or more.

  Examples of the anionic vinyl monomer include a carboxyl group-containing monomer (which means a polymerizable vinyl monomer containing a carboxyl group), and a sulfonic acid group-containing monomer (which is a polymerizable vinyl containing a sulfonic acid group. And a phosphoric acid group-containing monomer (which means a polymerizable vinyl monomer containing a phosphoric acid group).

  Examples of the carboxyl group-containing monomer include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, cinnamic acid, and crotonic acid, glyoxylic acid such as 2-acrylamide glycolic acid, and 2-methacrylamide glycolic acid, and fumaric acid. Unsaturated dicarboxylic acids such as acid, maleic acid, itaconic acid, citraconic acid and muconic acid, aconitic acid, 3-butene-1,2,3-tricarboxylic acid, and 4-pentene-1,2,4-tricarboxylic acid Unsaturated tricarboxylic acids such as 1-pentene-1,1,4,4-tetracarboxylic acid, 4-pentene-1,2,3,4-tetracarboxylic acid, and 3-hexene-1,1,6, Examples thereof include unsaturated tetracarboxylic acids such as 6-tetracarboxylic acid.

  Examples of the sulfonic acid group-containing monomer include vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, and 2-acrylamido-2-methylpropane sulfonic acid.

  Examples of the phosphoric acid group-containing monomer include vinylphosphonic acid and 1-phenylvinylphosphonic acid.

  Also, salts of carboxyl group-containing monomers, sulfonic acid group-containing monomers, and phosphoric acid group-containing monomers can be used. Examples of the carboxyl group-containing monomer, the sulfonic acid group-containing monomer, or the salt of the phosphoric acid group-containing monomer include alkali metal salts, alkaline earth metal salts, and ammonium salts.

  These may be used alone or in combination of two or more.

  Among the anionic monomers, a suitable anionic monomer is an unsaturated dicarboxylic acid, more preferably itaconic acid.

  It is preferable to use a vinyl monomer represented by the following general formula 1.

In General Formula 1, R ¹ represents an alkylene group having 1 to 4 carbon atoms, and R ^{2 to} R ⁴ represent a hydrogen atom or an alkyl group having 22 or less carbon atoms which may have a substituent (provided that R ² any two or three kinds of to R ⁴ excluding a case where the hydrogen atom.). X ⁻ represents an anion of an inorganic acid or an organic acid.

R ¹ is an alkylene group having 1 to 4 carbon atoms, specifically, a methylene group (—CH ₂ —), an ethylene group (—CH ₂ CH ₂ —), a propylene group (—CH ₂ CH ₂ CH ₂ —). ) And a butylene group (—CH ₂ CH ₂ CH ₂ CH ₂ —), and a methylene group is preferred. R ^{2 to} R ⁴ are each a hydrogen atom or an alkyl group having 22 or less carbon atoms which may have a substituent (except when any two or three of R ^{2 to} R ⁴ are hydrogen atoms). Preferably an alkyl group having 22 or less carbon atoms, a hydroxyalkyl group, an alkylamine group, an alkyl ether group, an alkyl ester group, an alkylamide group, an aryl group, or any two of R ^{2 to} R ⁴ bonded to each other to form a cyclic structure It is the group that became. Specifically, R ^{2 to} R ⁴ are a methyl group, an ethyl group, a butyl group, a stearyl group, a hydroxyethyl group, and a benzyl group, which may be the same substituent or a combination of different substituents. It may be. Specific examples of the cyclic structure include a morpholine skeleton structure composed of a nitrogen atom, R ³ , and R ⁴ . Also any one of R ² to R ^4, two or three types is a hydroxyethyl group, and more preferably remains R ² to R ⁴ is a hydrogen atom or a methyl group.

X ⁻ is an anion in inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, and nitric acid, or organic acids such as carboxylic acids such as formic acid, acetic acid, oxalic acid, and propionic acid, and Cl ^{-, Br} -, I ^- is preferably, Cl ^- is more preferable.

  Examples of the vinyl monomer represented by the general formula 1 include 2-propene-1-aminium, N, N, N, 2-tetramethyl, chloride, 2-propene-1-aminium, N, N-diethyl- 2-methyl, hydrochloride, 2-propene-1-aminium, N, N, N-triethyl-2-methyl, chloride, 2-propene-1-aminium, N, N, N-tributyl-2-methyl, chloride 2-propene-1-aminium, N, N, 2-trimethyl-N-octadecyl, chloride, benzenemethanaminium, N, N-dimethyl-N- (2-methyl-2-propenyl), chloride, N- Methyl-N- (2-methyl-2-propenyl) morpholinium chloride, 2-propene-1-aminium, N-hydroxyethyl- , N, 2-trimethyl, chloride, 2-propene-1-aminium, N, N-dihydroxyethyl-N, 2-dimethyl, chloride, 2-propene-1-aminium, N-hydroxyethyl-N, 2-dimethyl , Hydrochloride.

  Crosslinkable monomers and crosslinkable compounds that are one of the other monomers include monomers having multiple vinyl groups, N-substituted (meth) acrylamide, monomers having a chain transfer point with vinyl groups, silicon monomers , Water-soluble aziridinyl compounds, water-soluble polyfunctional epoxy compounds, and the like. These may be used alone or in combination of two or more.

  Examples of the monomer having a plurality of vinyl groups include trifunctional vinyl monomers, tetrafunctional vinyl monomers and the like in addition to bifunctional monomers such as di (meth) acrylates, bis (meth) acrylamides, and divinyl esters. Can be mentioned.

  Examples of the di (meth) acrylates include ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol diacrylate. A methacrylate, glycerol diacrylate, glycerol dimethacrylate, etc. can be mentioned, These may be used individually by 1 type and may use 2 or more types together.

  Examples of the bis (meth) acrylamides include N, N-methylenebisacrylamide, N, N-methylenebismethacrylamide, ethylenebisacrylamide, ethylenebismethacrylamide, hexamethylenebisacrylamide, hexamethylenebismethacrylamide, N, N-bisacrylamide acetic acid, N, N-bisacrylamide methyl acetate, N, N-benzylidenebisacrylamide, N, N-bis (acrylamidomethylene) urea and the like can be mentioned, and these may be used alone. Two or more kinds may be used in combination.

  Examples of the divinyl esters include divinyl adipate, divinyl sebacate, diallyl phthalate, diallyl malate, and diallyl succinate. These may be used alone or in combination of two or more. You may use together.

  Examples of other bifunctional monomers include allyl acrylate, allyl methacrylate, divinylbenzene, and diisopropenylbenzene. These may be used alone or in combination of two or more. May be.

  Examples of the trifunctional vinyl monomer include triacryl formal, triallyl isocyanurate, N, N-diallylacrylamide, N, N-diallylmethacrylamide, triallylamine, and triallyl pyromellitate. These may be used alone or in combination of two or more.

  Examples of the tetrafunctional vinyl monomer include tetramethylolmethane tetraacrylate, tetraallyl pyromellitate, N, N, N ′, N′-tetraallyl-1,4-diaminobutane, tetraallylamine (salt), and tetra An allyloxyethane etc. can be mentioned, These may be used individually by 1 type and may use 2 or more types together.

  Examples of the N-substituted (meth) acrylamide include N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-isopropyl ( Mention may be made of (meth) acrylamide and Nt-octyl (meth) acrylamide.

  Examples of the monomer having a crosslinking action by having a vinyl group and a chain transfer point include N-methylolacrylamide, glycidyl acrylate, and glycidyl methacrylate, and these may be used alone. Two or more kinds may be used in combination.

  Examples of the silicon monomer include 3-acryloyloxymethyltrimethoxysilane, 3-methacryloyloxymethyltrimethoxysilane, 3-acryloyloxypropyldimethoxymethylsilane, 3-methacryloyloxypropyldimethoxymethylsilane, 3 -Acryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-acryloyloxypropylmethyldichlorosilane, 3-methacryloyloxypropylmethyldichlorosilane, 3-acryloyloxyoctadecyltriacetoxysilane, 3 -Methacryloyloxyoctadecyltriacetoxysilane, 3-acryloyloxy-2,5-dimethylhexyldiacetoxymethylsilane, 3-methacryloyloxy-2,5-dimethylhex Luzia Seto carboxymethyl silane, and it can be exemplified vinyl dimethylacetoxysilane like, which may be used singly or in combination of two or more.

  Examples of the water-soluble aziridinyl compound include tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, and 4,4′-bis (ethyleneimine). And carbonylamino) diphenylmethane. These may be used alone or in combination of two or more.

  Examples of the water-soluble polyfunctional epoxy compound include (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, (poly) glycerin diglycidyl ether, and (poly) glycerin triglycidyl ether. These may be used alone or in combination of two or more.

  Examples of other monomers that can be used in the present invention include nonionic vinyl monomers. Examples of nonionic vinyl monomers include (meth) acrylic acid esters, (meth) acrylonitrile, styrene, styrene derivatives, vinyl acetate, vinyl propionate, methyl vinyl ether, N- (2-hydroxyethyl) acrylamide, and the like. These may be used alone or in combination of two or more.

  The amount of each monomer constituting the (meth) acrylamide polymer is determined by the internal bond strength and burst strength of the paper when the paper strength agent containing the resulting (meth) acrylamide polymer is used. It can be determined by sufficiently considering the paper strength such as the paper strength, the drainage at the time of papermaking, the performance of fine fibers, fillers, and the like.

(Meth) acrylamide and ionic vinyl monomer are essential for a total of 100 mol%,
(Meth) acrylamide is usually 100 to 45 mol%, preferably 98 to 74 mol%,
An ionic vinyl monomer is 0-55 mol% normally, Preferably it is 2-26 mol%.
As for other copolymerizable monomers, it is preferable to use a part of the number of moles of the above (meth) acrylamide in the range of usually 0 to 20 mol%, preferably 0.01 to 10 mol%.

  In addition, the usage-amount of a cationic vinyl monomer and an anionic vinyl monomer in an ionic vinyl monomer is 0.05-20 mol% normally, respectively.

  In carrying out the polymerization of the monomer, a conventionally known polymerization initiator can be used. Specifically, persulfates such as sodium persulfate, potassium persulfate and ammonium persulfate, peroxides such as benzoyl peroxide, hydrogen peroxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, bromine Bromate such as sodium acid, potassium bromate, perborate such as sodium perborate, ammonium perborate, percarbonate such as sodium percarbonate, potassium percarbonate, ammonium percarbonate, sodium perphosphate, Perphosphates such as potassium perphosphate and ammonium perphosphate can be used. In this case, one kind can be used alone, but two or more kinds may be used in combination, and a redox polymerization initiator may be used in combination with a reducing agent. Examples of the reducing agent include sulfites such as sodium sulfite, bisulfites such as sodium bisulfite, organic amines such as N, N, N ′, N′-tetramethylethylenediamine, and reducing sugars such as aldose. it can. Moreover, these reducing agents may be used individually by 1 type, and may be used together 2 or more types. Other than the above, azobisisobutyronitrile, 2,2′-azobis-2-amidinopropane hydrochloride, 2,2′-azobis-2,4′-dimethylvaleronitrile, 4,4′-azobis- Azo polymerization initiators such as 4-cyanovaleric acid and its salts can also be used.

  Moreover, a conventionally well-known chain transfer agent can be used suitably as needed. Conventionally known chain transfer agents include compounds having one or more hydroxyl groups in the molecule, such as oligomers and polymers such as isopropyl alcohol, butanol, ethylene glycol, glycerine alcohols, polyethylene oxide, polyglycerin, glucose, and the like. And saccharides and vitamins such as ascorbic acid and sucrose. Examples of the compound containing one or more mercapto groups in the molecule include butyl mercaptan, mercaptoethanol, thioglycolic acid and its ester, mercaptopropionic acid and its ester, thioglycerin, cysteamine and its salt. be able to. Examples of compounds having one or more carbon-carbon unsaturated bonds in the molecule include (meth) allyl alcohol and its ester derivatives, (meth) allylamine, diallylamine, dimethallylamine and its amide derivatives, triallylamine, Examples include methallylamine, (meth) allylsulfonic acid and salts thereof, allyl sulfides, and allyl mercaptans. Furthermore, mention may be made of hypophosphorous acid.

  The synthesis of the (meth) acrylamide polymer that can be used in the present invention may be performed by using a monomer and a solvent water (an organic solvent) in a predetermined reaction vessel under an inert gas atmosphere such as nitrogen. ) And the chain transfer agent as necessary, and the polymerization initiator is added under stirring to start the polymerization, whereby the (meth) acrylamide polymer of the present invention is obtained.

<Cation-modified (meth) acrylamide polymer by Hoffmann decomposition>
The cation-modified (meth) acrylamide polymer by the Hofmann decomposition reaction may be any (meth) acrylamide polymer that has been cation-modified by the Hoffman decomposition reaction, and the (meth) acrylamide polymer before the modification is (meth) It may be a copolymer of a nonionic monomer, a cationic monomer or an anionic monomer copolymerizable with acrylamide, or a combination of a crosslinkable monomer and a chain transfer agent.

Examples of the nonionic monomer copolymerizable with the (meth) acrylamide include acrylonitrile, (meth) acrylic acid ester, vinyl acetate and the like.

  Examples of the cationic monomer copolymerizable with (meth) acrylamide include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide, allylamine, diallylamine and the like. Vinyl monomers having amino groups or salts of inorganic or organic acids thereof or tertiary amino group-containing vinyl monomers and methyl chloride, benzyl chloride, dimethyl sulfate, epichlorohydrin, glycidyl trimethyl ammonium chloride, 3-chloro-2 -Vinyl monomers having a quaternary ammonium group obtained by a reaction with a quaternizing agent such as hydroxypropyltrimethylammonium chloride.

Examples of the anionic monomer copolymerizable with (meth) acrylamide include acrylic acid, methacrylic acid, itaconic acid, maleic anhydride, fumaric acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, (meth) Examples thereof include vinyl monomers such as allylsulfonic acid or sodium, potassium and ammonium salts thereof.

Examples of the crosslinkable vinyl monomer copolymerizable with (meth) acrylamide include bis (meth) acrylamides such as methylolacrylamide, methylenebis (meth) acrylamide, and ethylenebis (meth) acrylamide, ethylene glycol di (meth) acrylate, and diethylene glycol. Di (meth) acrylates such as di (meth) acrylate and polyethylene glycol di (meth) acrylate, divinyl esters such as divinyl adipate and divinyl sebacate, epoxy acrylates, urethane acrylates, divinylbenzene, 1,3,3 5-triacryloylhexahydro-S-triazine, triallyl isocyanurate, triallyl trimellitate, triallylamine, N, N-diallylacrylamide, tetramethylol Tan tetraacrylate, tetraallyl pyromellitate acrylate, N with N-substituted amido group, N- dimethyl acrylamide, N- hydroxyethyl acrylamide.

The (meth) acrylamide polymer that is cationically modified by the Hofmann decomposition reaction may be copolymerized with one or a plurality of monomers copolymerizable with the (meth) acrylamide. % Is 60% or more.

As a method for producing the (meth) acrylamide polymer, various conventionally known methods can be employed. For example, in a reaction vessel equipped with a stirrer and a nitrogen gas introduction tube, the aforementioned monomer and water are charged, and as a polymerization initiator, peroxides such as hydrogen peroxide, ammonium persulfate, potassium persulfate, ammonium hydroperoxide, Or a redox initiator that combines a peroxide and a reducing agent such as bisulfite, or a water-soluble azo polymerization initiator such as 2,2-azobis- (2-amidinopropane) hydrochloride, If necessary, a polymerization regulator or chain transfer agent such as isopropyl alcohol, allyl alcohol, sodium hypophosphite, mercaptoethanol, thioglycolic acid or the like is appropriately used, and the reaction is carried out at a reaction temperature of 20 to 90 ° C. for 1 to 5 hours. The desired (meth) acrylamide polymer can be obtained.

The cation modification by the Hofmann decomposition reaction may be the same as the conventional method. For example, by adding a hypohalite and an alkali catalyst to the aqueous solution of the aforementioned (meth) acrylamide polymer, the (meth) acrylamide polymer and the hypochlorite are reacted in the alkaline region, Thereafter, an acid is added to adjust the pH to 3.5 to 5.5, or a poly (meth) acrylamide is adjusted by Hofmann decomposition reaction in the presence of choline chloride (for example, JP-A-53-109545). ), A method of adjusting by adding a quaternary reaction product of a tertiary amine having a hydroxyl group and benzyl chloride or a derivative thereof in the Hofmann decomposition reaction (for example, Japanese Patent Publication No. 58-8682), as a stabilizer in the Hoffman decomposition reaction In the method of adjusting by adding an organic polyvalent amine (for example, Japanese Examined Patent Publication No. 60-17322), or in the Hofmann decomposition reaction A method of adjusting by adding a specific cationic compounds as stabilizers Te (e.g., JP-B 62-45884 Publication) can be given.

<Starch>
As starches, raw starch, which is starch itself, cationized starch obtained by performing various modifications using starch as a raw material, oxidized starch, amphoteric starch, and the like, and these starches and the above-mentioned chemically modified starches are enzymatically modified. Enzyme-modified starch and the like can be used. Examples of the starch include starches obtained from various plants such as potato, sweet potato, tapioca, wheat, rice, corn, etc., and derivatives thereof include acetylation, phosphate ester of the starch. Examples thereof include modified starch such as modified starch and the like. These can be used in the form of powder or solution.

The cationized starch means a starch having a cationic group and having no anionic group, the oxidized starch means a starch having an anionic group and having no cationic group, and the amphoteric starch is cationic. A starch having both a group and an anionic group is meant.

In introducing a cationic group of starch, for example, starch or a derivative thereof is a known cationizing agent such as 3-chloro-2-hydroxypropyl, trimethylammonium chloride, glycidyltrimethylammonium chloride, dimethylaminoethyl chloride, or the like. It can be obtained by reacting in the presence of

As the starch having a cationic group, one having a reduced viscosity can be used. Examples of the viscosity reduction method include oxidant treatment or enzymatic degradation as enzyme modification.

As the oxidizing agent, a conventionally known and commonly used oxidizing agent can be used. Specifically, hypochlorites such as sodium hypochlorite, potassium hypochlorite, ammonium hypochlorite, persulfates such as sodium persulfate, potassium persulfate, ammonium persulfate, benzoyl peroxide, Peroxides such as hydrogen peroxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, bromates such as sodium bromate and potassium bromate, sodium perborate and ammonium perborate Percarbonates such as acid salts, sodium percarbonate, potassium percarbonate and ammonium percarbonate, and perphosphates such as sodium perphosphate, potassium perphosphate and ammonium perphosphate can be used. In this case, one kind can be used alone, or two or more kinds may be used in combination.

Examples of starch degrading enzymes used for enzymatic degradation include α-amylase, β-amylase, γ-amylase, and isoamylase produced by various bacteria, yeasts, animals and plants. Among these, α-amylase is most preferable in that it does not cause excessive low molecular weight substances or monosaccharides.

The starch used after cooking preferably has a viscosity of a 1% solid content aqueous solution at 25 ° C. of 5 to 10,000 mPa · s, more preferably 5 to 1,000 mPa · s.

<Pitch control agent>
Pitch control agents preferably used in the present invention include organic pitch control agents and inorganic pitch control agents. Cationic compounds obtained by polymerization containing at least one or more cationic monomers as the organic pitch control agent, amine-epihalohydrin resins, polyethyleneimine, polyethyleneimine modified products, cationic compounds such as polyvinylamine, Nonionic dispersants and anionic surfactants may be mentioned.

Examples of the cationic monomer used in the cationic polymer include compounds represented by the following general formulas 2 to 4, diallylamines, and the like. These may be used alone or in combination of two or more.

（但し、式中、Ａは酸素又はＮＨ、ｎは２〜４の整数、Ｒ^１はＨ又はメチル基、Ｒ^２、Ｒ^３、Ｒ^４、Ｒ^５、Ｒ^６は同一又は異なる炭素数１〜３の低級アルキル基、Ｘ⁻、Ｙ⁻は同一又は異なるアニオン性基を示す。）

(In the formula, A is oxygen or NH, n is an integer of 2 to 4, R ¹ is H or a methyl group, R ² , R ³ , R ⁴ , R ⁵ , R ⁶ are the same or different from 1 to 3 lower alkyl groups, X ⁻ and Y ⁻ are the same or different anionic groups.)

  Specific cationic monomers of the general formula 2 include 2-hydroxy-N, N, N, N ′, N′-pentamethyl-N ′-(3- (meth) acryloylaminopropyl) -1,3. -Propanediammonium dichloride, 2-hydroxy-N-benzyl-N, N-diethyl-N ', N'-dimethyl-N'-(2- (meth) acryloyloxyethyl) -1,3-propanediammonium di- Examples include bromide.

（但し、一般式化３中、Ａは酸素又はＮＨ、ｎは２〜４の整数、Ｒ^７はＨ又はメチル基、Ｒ^８、Ｒ^９は同一又は異なる炭素数１〜３の低級アルキル基を示す。）

(However, in General Formula 3, A is oxygen or NH, n is an integer of 2 to 4, R ⁷ is H or a methyl group, and R ⁸ and R ⁹ are the same or different lower alkyl groups having 1 to 3 carbon atoms. Show.)

Specific cationic monomers of the above general formula 3 include N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide and the like.

（但し、一般式化４中、Ａは酸素又はＮＨ、ｎは２〜４の整数、Ｒ^１０はＨ又はメチル基、Ｒ^１１ 、Ｒ^１２は同一又は異なる炭素数１〜３の低級アルキル基、Ｒ^１３は低級アルキル基又はベンジル基、Ｚ⁻はアニオン性基を示す。）

(However, in General Formula 4, A is oxygen or NH, n is an integer of 2 to 4, R ¹⁰ is H or a methyl group, R ¹¹ and R ¹² are the same or different lower alkyl groups having 1 to 3 carbon atoms, R ¹³ represents a lower alkyl group or a benzyl group, and Z ⁻ represents an anionic group.)

    As a specific cationic monomer of the above general formula 4, the cationic monomer represented by the above general formula 3 is converted to an appropriate quaternizing agent such as an alkyl halide, dialkyl carbonate, alkyl tosylate, alkyl mesylate, dialkyl. It is obtained by quaternization with sulfuric acid, benzyl halide, etc., for example, N-ethyl-N, N-dimethyl- (2- (meth) acryloyloxyethyl) ammonium bromide, N-benzyl-N, N-dimethyl- ( 3- (meth) acryloylaminopropyl) ammonium chloride and the like.

Examples of diallylamines include diallylamine, diallylmethylamine, and diallyldimethylammonium chloride.

    The cationic monomer may be used in an amount of 10 mol% or more, and other copolymerizable monomers include nonionic monomers such as acrylonitrile, (meth) acrylamide, (meth) acrylic acid methyl ester, (meth) acrylic acid ethyl ester, Α, β-unsaturated monocarboxylic acid such as acrylic acid and methacrylic acid, α, β-unsaturated dicarboxylic acid such as maleic acid, fumaric acid, itaconic acid, citraconic acid, styrene sulfonic acid, vinyl sulfonic acid, etc. Anionic monomers such as sulfonic acids and their salts, such as sodium salts, potassium salts, and ammonium salts, conventionally known chain transfer agents, and crosslinking agents may be used.

There is no restriction | limiting in particular as a polymerization method of the said cationic polymer, A conventionally well-known method is employable.

  Furthermore, as described above, the cationic monomer of the general formula 3 is not only subjected to the polymerization reaction after quaternization with the quaternizing agent, but also the cationic monomer belonging to the general formula 3 and the like. Can be quaternized with the above quaternizing agent during or after the polymerization reaction. In this case, all may be quaternized, but some may be quaternized.

  The amine-epihalohydrin resin can be obtained by reacting amines with epihalohydrin. The amine that can be used as the amine is not particularly limited as long as it is an amine having an amino group capable of reacting with at least one epihalohydrin in the molecule, but is not limited to primary amine, secondary amine, tertiary amine. One or more amines selected from the group consisting of amines, alkylene diamines, polyalkylene polyamines, and alkanol amines are preferred.

Examples of amines include methylamine, ethylamine, propylamine, isopropylamine, allylamine, n-butylamine, sec-butylamine, tert-butylamine, cyclohexylamine, cyclooctylamine, dimethylamine, diethylamine, dipropylamine, methylethylamine, methylpropylamine , Trimethylamine, triethylamine, tripropylamine, triisopropylamine, ethylenediamine, trimethylenediamine, and propylenediamine, N, N dimethylaminopropylamine, 1,3-diaminocyclohexyl, 1,4-diaminocyclohexyl, diethylenetriamine, triethylenetetramine , Tetraethylenepentamine, pentaethylenehexamine, monoethanolamine, di Ethanolamine, N - methylethanolamine, triethanolamine, N, N - diethylethanolamine, N, N - dimethylethanolamine, and the like.

As epihalohydrin, epichlorohydrin, epibromohydrin and the like can be used, and these can be used alone or in admixture of two or more. Epichlorohydrin is preferable as the epihalohydrin.

  There is no restriction | limiting in particular as a polymerization method of the said amine epihalohydrin resin, A conventionally well-known method is employable.

Examples of the inorganic pitch control agent include polyaluminum compounds such as polyaluminum chloride, polyaluminum silicate sulfate, polyaluminum hydroxide, polyiron sulfate, zirconium carbonate, bentonite, and talc (fine powder).

<Yield agent>
Examples of the retention agent include an organic retention agent and an inorganic retention agent.

Examples of the organic retention agent include acrylamide polymers, starches, polyvinyl alcohols, and celluloses. Some of these also function as a paper strength agent, but those having the purpose of improving the yield have a higher molecular weight and a larger cohesive ability than those of the paper strength agent. The ionicity of the retention agent may be any of cationic, anionic, amphoteric, and nonionic, and two or more kinds can be appropriately combined. Moreover, the structure of the polymer constituting the organic retention agent may have any of a linear structure, a branched structure, and a crosslinked structure.

Examples of the inorganic retention agent include bentonite, colloidal silicic acid, and aluminum compounds.

Examples of the aluminum compound to be added to the present invention as needed include water-soluble aluminum compounds such as aluminum sulfate (sulfuric acid band), polyaluminum chloride, alumina sol, polysulfuric acid aluminum silicate, aluminum silicate sol, and polyaluminum hydroxide. When added, a sulfuric acid band and polyaluminum chloride are preferred. These aluminum compounds can be used alone or in combination of two or more. The aluminum compound is preferably not used or used in an amount of 1% by weight or less based on the solid content of the pulp slurry. When used, 0.1 to 0.5% by weight is preferably used.

<Sizing agent>
In the present invention, no sizing agent is added to the pulp slurry. By not adding the internal sizing agent to the pulp slurry, it is possible to reduce the pitch and foaming of the pulp slurry.

<Chemical addition location and amount>
When adding a paper strength agent in the present invention, the addition location is not particularly limited, but it is preferably added between the beating machine outlet and the inlet inlet of the paper making process. Moreover, it can also be divided and added to not only one place but several places.

The addition ratio of the solid content of the paper strength agent to the pulp is 0.02 to 3% by weight, preferably 0.05 to 1% by weight. If it is less than 0.02% by weight, the paper strength effect may be insufficient, and even if it exceeds 3% by weight, the effect may reach its peak.

<Location and amount of yield agent added>
When the retention agent is added to the pulp slurry, the place of addition is not particularly limited, but it is preferably added at a place with good mixing between the beater outlet and the inlet outlet. Moreover, it is not limited to one place but may be added separately in a plurality of places, or one or more retention agents may be used.

The ratio of the solid content of the retention agent to the pulp is 0.005 to 2% by weight, preferably 0.01 to 1% by weight.

<Pitch control agent addition location and amount>
When the pitch control agent is added to the pulp slurry, the addition location is not particularly limited, but it is preferably added at a location with good mixing between the beater outlet and the inlet outlet. Moreover, it is sufficient to divide and add not only to one place but to several places, and 1 type, or 2 or more types of pitch control agents may be used.

When the pitch control agent is added to the pulp slurry, the addition ratio of the solid content to the pulp is preferably 0.005 to 1% by weight, more preferably 0.01 to 0.5% by weight. If the addition rate is less than 0.005% by weight, the antifouling effect may be poor, and if the addition rate exceeds 1% by weight, fixing of paper strength agents and the like may be reduced.

In addition to the above additives, the pulp slurry contains wet paper strength agents such as polyamide polyamine epichlorohydrin resin, and fillers such as calcium carbonate such as light calcium carbonate and heavy calcium carbonate, clay, and titanium oxide. There is no problem in using them together as appropriate.

After producing the paperboard base as described above, the coating liquid can be applied to the surface of the paperboard base as necessary. In particular, when no internal sizing agent is used, it is preferable to use a surface sizing agent.

The coating amount of the coating liquid in the case of surface paper strength agent, 0.05-5 g / ^{m 2} typically with solids, preferably 0.1-2 g / ^{m 2.} Moreover, the coating amount when using the surface sizing agent is usually 0. 01-1 g / m ² , preferably 0. 02 to 0.1 g / m ² .

The coating liquid can be applied to paper by a known method, for example, coating using a size press, film press, gate roll coater, blade coater, calendar, bar coater, knife coater, air knife coater. Is possible. Moreover, spray coating can also be performed.

For coating liquid, surface paper strength agent, surface sizing agent, anti-slip agent, antiseptic, antifoaming agent, viscosity modifier, rust inhibitor, mold release agent, flame retardant, dye, water repellent, ruler However, it is preferable that the coating liquid contains a surface paper strength agent and / or a surface sizing agent.

<Surface paper strength agent>
Examples of the surface paper strength agent that can be used in the present invention include synthetic polymers such as acrylamide resins and polyvinyl alcohols, and natural polymers of polysaccharides such as starches, celluloses, chitosan, alginic acid, and carrageenan. . Among these, acrylamide resins are preferably used.

  Acrylamide resins may be anionic, cationic, or nonionic, and include at least acrylamides and, if necessary, a copolymerizable monomer such as an ionic monomer or a crosslinking agent. Can be obtained by copolymerization.

  As the acrylamides, acrylamide and methacrylamide are preferable, and N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N- Any one or more of N-substituted (meth) acrylamides such as t-octyl (meth) acrylamide can be used in combination with acrylamide and methacrylamide.

Examples of the ionic monomer include an anionic monomer and a cationic monomer.

Examples of the anionic vinyl monomer include α, β-unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid, and salts such as alkali metal salts and ammonium salts such as sodium salts and potassium salts, maleic acid, and fumaric acid. Α, β-unsaturated dicarboxylic acids such as acid, itaconic acid, citraconic acid and the like, salts such as alkali metal salts and ammonium salts such as sodium salt and potassium salt, aconitic acid, 3-butene-1,2,3- Α, β-unsaturated tricarboxylic acids such as tricarboxylic acid and 4-pentene-1,2,4-tricarboxylic acid, and salts such as alkali metal salts and ammonium salts such as sodium salt and potassium salt thereof, (meth) allylsulfone Organic sulfone such as acid, vinyl sulfonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid Acids and salts thereof such as alkali metal salts and ammonium salts such as sodium and potassium salts, phosphonic acids such as vinylphosphonic acid and α-phenylvinylphosphonic acid, and alkali metal salts and ammonium salts such as sodium and potassium salts thereof Etc., and one or more of these can be used.

Examples of the cationic vinyl monomer include a vinyl monomer having a primary amino group, a vinyl monomer having a secondary amino group, a vinyl monomer having a tertiary amino group, and a vinyl monomer having a quaternary ammonium salt.

  Examples of the vinyl monomer having a primary amino group include allylamine, methallylamine, and salts thereof. These salts include inorganic acid salts such as hydrochloride and sulfate, and organic acid salts such as formate and acetate.

  Examples of the vinyl monomer having a secondary amino group include diallylamine, dimethallylamine, and salts thereof. These salts include inorganic acid salts such as hydrochloride and sulfate, and organic acid salts such as formate and acetate.

  Further, as the vinyl monomer having a secondary amino group, vinyl monomers having the primary amino group such as allylamine and methallylamine, and alkyl halides such as methyl chloride and methyl bromide, benzyl chloride, and benzyl bromide are used. Examples thereof include monomers converted into secondary amine acid salts by reaction with aralkyl halides, dimethyl sulfate, dialkyl sulfates such as diethyl sulfate, epichlorohydrin and the like.

  Examples of the vinyl monomer having a tertiary amino group include dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethylaminopropyl acrylate, dimethylaminopropyl methacrylate, diethylaminopropyl acrylate, and diethylaminopropyl methacrylate. And dialkylaminoalkyl (meth) acrylamides such as dialkylaminoalkyl (meth) acrylates, dimethylaminopropyl acrylamide, dimethylaminopropyl methacrylamide, diethylaminopropyl acrylamide, and diethylaminopropyl methacrylamide, and salts thereof. it can. These salts include inorganic acid salts such as hydrochloride and sulfate, and organic acid salts such as formate and acetate.

  Further, as the vinyl monomer having a tertiary amino group, vinyl monomers having the secondary amino group such as diallylamine and dimethallylamine, and alkyl halides such as methyl chloride and methyl bromide, aralkyl such as benzyl chloride and benzyl bromide. Examples thereof include monomers converted into acid salts of tertiary amines by reaction with any one of halides, alkyl sulfates such as dimethyl sulfate and diethyl sulfate, and epichlorohydrin.

  Examples of the vinyl monomer having a quaternary ammonium salt include diallyldimethylammonium chloride, dimethallyldimethylammonium chloride, diallyldiethylammonium chloride, and diethyldimethallylammonium chloride.

  Examples of the vinyl monomer having a quaternary ammonium salt include a vinyl monomer obtained by reacting the vinyl monomer having a tertiary amino group with a quaternizing agent. Examples of the quaternizing agent include alkyl halides such as methyl chloride and methyl bromide, aralkyl halides such as benzyl chloride and benzyl bromide, alkyl sulfates such as dimethyl sulfate and diethyl sulfate, epichlorohydrin, 3-chloro- Examples include 2-hydroxypropyltrimethylammonium chloride and glycidyltrialkylammonium chloride.

  Specifically, acryloyloxyethyltrimethylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, acryloyloxyethyldimethylbenzylammonium chloride, methacryloyloxyethyldimethylbenzylammonium chloride, acryloyloxypropyldimethylbenzylammonium chloride, and methacryloyloxypropyldimethylbenzylammonium chloride Examples include chloride.

  Furthermore, the vinyl monomer represented by following General formula 5 can be mentioned as cationic vinyl monomers.

In General Formula 5, R ¹ represents an alkylene group having 1 to 4 carbon atoms, R ^{2 to} R ⁴ represent a hydrogen atom or an alkyl group having 22 or less carbon atoms which may have a substituent (provided that R ² any two or three kinds of to R ⁴ excluding a case where the hydrogen atom.). X ⁻ represents an anion of an inorganic acid or an organic acid.

R ¹ is an alkylene group having 1 to 4 carbon atoms, specifically, a methylene group (—CH ₂ —), an ethylene group (—CH ₂ CH ₂ —), a propylene group (—CH ₂ CH ₂ CH ₂ —). ) And a butylene group (—CH ₂ CH ₂ CH ₂ CH ₂ —), and a methylene group is preferred. R ^{2 to} R ⁴ are each a hydrogen atom or an alkyl group having 22 or less carbon atoms which may have a substituent (except when any two or three of R ^{2 to} R ⁴ are hydrogen atoms). Preferably an alkyl group having 22 or less carbon atoms, a hydroxyalkyl group, an alkylamine group, an alkyl ether group, an alkyl ester group, an alkylamide group, an aryl group, or any two of R ^{2 to} R ⁴ bonded to each other to form a cyclic structure It is the group that became. Specifically, R ^{2 to} R ⁴ are a methyl group, an ethyl group, a butyl group, a stearyl group, a hydroxyethyl group, and a benzyl group, which may be the same substituent or a combination of different substituents. It may be. Specific examples of the cyclic structure include a morpholine skeleton structure composed of a nitrogen atom, R ³ , and R ⁴ . Also any one of R ² to R ^4, two or three types is a hydroxyethyl group, and more preferably remains R ² to R ⁴ is a hydrogen atom or a methyl group.

X ⁻ is an anion in inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, and nitric acid, or organic acids such as carboxylic acids such as formic acid, acetic acid, oxalic acid, and propionic acid, and Cl ^{-, Br} -, I ^- is preferably, Cl ^- is more preferable.

  Examples of the vinyl monomer represented by the general formula 5 include 2-propene-1-aminium, N, N, N, 2-tetramethyl, chloride, 2-propene-1-aminium, N, N-diethyl- 2-methyl, hydrochloride, 2-propene-1-aminium, N, N, N-triethyl-2-methyl, chloride, 2-propene-1-aminium, N, N, N-tributyl-2-methyl, chloride 2-propene-1-aminium, N, N, 2-trimethyl-N-octadecyl, chloride, benzenemethanaminium, N, N-dimethyl-N- (2-methyl-2-propenyl), chloride, N- Methyl-N- (2-methyl-2-propenyl) morpholinium chloride, 2-propene-1-aminium, N-hydroxyethyl- , N, 2-trimethyl, chloride, 2-propene-1-aminium, N, N-dihydroxyethyl-N, 2-dimethyl, chloride, 2-propene-1-aminium, N-hydroxyethyl-N, 2-dimethyl , Hydrochloride.

  These vinyl monomers having a primary amino group, a secondary amino group, a tertiary amino group, or a quaternary ammonium salt may be used alone or in combination of two or more.

Examples of the nonionic vinyl monomer include esters of alcohol and (meth) acrylic acid, styrene, styrene derivatives, (meth) acrylonitrile, vinyl acetate, vinyl propionate, methyl vinyl ether, and the like, one or two of these. It can be used above.

Examples of the crosslinking agent include di (meth) acrylates such as ethylene glycol di (meth) acrylate and diethylene glycol di (meth) acrylate, and bis (meta) such as methylene bis (meth) acrylamide and N, N-bisacrylamide acetic acid. ) Bifunctional vinyl monomers such as acrylamides, divinyl adipate, diallyl malate, N-methylolacrylamide, diallyldimethylammonium, glycidyl (meth) acrylate, 1,3,5-triacryloylhexahydro-S-triazine, Trifunctional amine monomers such as triallylamine, triallyl isocyanurate, triallyl trimellitate, tetramethylolmethane tetraacrylate, tetraallyl pyromellilate, tetraallylamine salt, tetraallyloxy Tetrafunctional vinyl monomers such as ethane.

In addition, water-soluble aziridinyl compounds such as tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, (poly) ethylene glycol diglycidyl ether, (poly) Water-soluble polyfunctional epoxy compounds such as glycerin diglycidyl ether, 3- (meth) acryloxymethyltrimethoxysilane, 2- (meth) acrylamide-2-methylpropyltrimethoxysilane, vinyldimethylmethoxysilane, vinyltrichlorosilane, Examples thereof include silicon compounds such as vinyltriphenoxysilane and 2- (meth) acrylamide-2-methylpropyltriacetoxysilane, and these can be used alone or in combination.

In order to obtain acrylamide resins for use in the present invention, ureas and ammonium salts can be added before and after the monomers are polymerized, and it is particularly preferable to add ureas before the reaction. Examples of ureas include urea, thiourea, ethylene urea, and ethylene thiourea. Examples of ammonium salts include ammonium sulfate and ammonium phosphate. These can be used alone or in combination. . Among these, it is particularly preferable economically to use urea or ammonium sulfate. The amount of urea used is preferably 5 to 30% by weight based on the total amount of monomers such as acrylamides.

  The weight ratio of the acrylamide component and the ionic monomer component used in the acrylamide resin is 100 to 50% / 0 to 50%, preferably 98 to 80% / 2 to 20%.

The reaction for obtaining acrylamide resins is charged in a predetermined reaction vessel so that the total concentration of monomers as constituents of acrylamide resins is 5 to 50% by weight, preferably 10 to 40% by weight. The polymerization initiator is used and the reaction temperature is 40 to 100 ° C. and the reaction is performed for 1 to 10 hours. Of course, according to the characteristics of the monomer component to be used, the reaction can be carried out by continuously dropping the monomer or adding the monomer in portions.

The polymerization initiator used for the reaction of acrylamide-based resins is not particularly limited, and known and conventional ones are used. Examples of radical polymerization initiators include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate, peroxides such as benzoyl peroxide, tert-butyl hydroperoxide, and di-tert-butyl peroxide, and bromic acid. Bromate such as sodium and potassium bromate, perborate such as sodium perborate, potassium perborate and ammonium perborate, percarbonate such as sodium percarbonate, potassium percarbonate and ammonium percarbonate, percarbonate Examples thereof include perphosphates such as sodium phosphate, potassium perphosphate, and ammonium perphosphate.

These polymerization initiators can be used alone, but can also be used as a redox polymerization initiator in combination with a reducing agent. Examples of the reducing agent include sulfites, hydrogen sulfites, organic amines such as N, N, N ′, N′-tetramethylethylenediamine, 2,2′-azobis-2-amidinopropane hydrochloride, azobisisobutyronitrile. 2,2′-azobis-2,4-dimethylvaleronitrile, azo compounds such as 4,4′-azobis-4-cyanovaleric acid, and reducing sugars such as aldose. Two or more of these initiators may be used in combination. The usage-amount of a polymerization initiator is 0.01 to 5 weight% normally with respect to the total amount of the monomer used for acrylamide resin.

Acrylamide resins are aqueous solutions having a solid content of 5 to 50% by weight, preferably 10 to 40% by weight, and a viscosity at 25 ° C. (Brookfield rotational viscometer) of 500 to 15,000 mPa · s, preferably 1,000 to 10,000 mPa · s. If it exceeds 15,000 mPa · s, the coating workability may deteriorate, and if it is less than 500 mPa · s, the effect of improving the specific burst strength and surface strength may be inferior.

The pH of acrylamide resins can be adjusted as appropriate using an acid or alkali after the reaction is completed. Acids and alkalis include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid, organic acids such as formic acid, acetic acid and propionic acid, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, sodium carbonate and potassium carbonate Alkali metal carbonates such as ammonia, amine bases such as ammonia, methylamine and dimethylamine can be used.

<Polyvinyl alcohols>
Examples of polyvinyl alcohols that can be used in the present invention include cationic polyvinyl alcohol, anionic polyvinyl alcohol, amphoteric polyvinyl alcohol, and nonionic polyvinyl alcohol.

Examples of the cationic polyvinyl alcohol include polyvinyl alcohol having a tertiary amino group and polyvinyl alcohol having a quaternary ammonium salt. Examples of the anionic polyvinyl alcohol include polyvinyl alcohol having a carboxyl group. Amphoteric polyvinyl alcohol refers to those having a cationic group such as a tertiary amino group and an anionic group simultaneously.

  Although the said polyvinyl alcohol can use what was manufactured by various methods, Usually, what was manufactured by hydrolysis or alcoholysis (alcohololysis) of polyvinyl ester can be used. The polyvinyl ester includes a homopolymer of vinyl ester, a copolymer of two or more vinyl esters, a copolymer of vinyl ester and other ethylenically unsaturated monomers, and the like. Here, vinyl formate, vinyl acetate, vinyl propionate, vinyl versatate, vinyl pivalate and the like can be used as the vinyl ester. Among these, industrially manufactured and inexpensive vinyl acetate can be preferably used. There are various other ethylenically unsaturated monomers copolymerizable with the vinyl ester, and there is no particular limitation. For example, α-olefin, halogen-containing monomer, carboxylic acid-containing monomer, (Meth) acrylic acid ester, vinyl ether, sulfonic acid-containing monomer, amide group-containing monomer, amino group-containing monomer, quaternary ammonium salt-containing monomer, silyl group-containing monomer, hydroxyl group-containing monomer Examples thereof include monomers and acetyl group-containing monomers.

  The polyvinyl alcohols are not particularly limited as to the degree of polymerization, but usually the degree of polymerization is preferably 300 to 4000. The saponification degree of polyvinyl alcohols is not particularly limited, but is usually 60 to 100 mol%, preferably 80 to 100 mol%, and more preferably 95 to 100 mol%.

<Starch>
As starches, raw starch, which is starch itself, oxidized starch obtained by performing various modifications using starch as a raw material, cationized starch, amphoteric starch, and the like, and these starches and the above-mentioned chemically modified starches are enzyme-modified. Enzyme-modified starch and the like can be used. Examples of the starch include starch obtained from various plants such as potato, sweet potato, tapioca, wheat, rice, corn, etc., and derivatives thereof include acetylation, phosphate esterification and the like of the starch. Examples thereof include modified or treated starch. These can be used in the form of powder or solution.

Oxidized starch means starch having an anionic group and no cationic group, cationized starch means a starch having a cationic group and no anionic group, and amphoteric starch is cationic. A starch having both a group and an anionic group is meant.

As the oxidizing agent for starches, a conventionally known and commonly used oxidizing agent can be used. Specifically, hypochlorites such as sodium hypochlorite, potassium hypochlorite, ammonium hypochlorite, persulfates such as sodium persulfate, potassium persulfate, ammonium persulfate, benzoyl peroxide, Peroxides such as hydrogen peroxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, bromates such as sodium bromate and potassium bromate, sodium perborate and ammonium perborate Percarbonates such as acid salts, sodium percarbonate, potassium percarbonate and ammonium percarbonate, and perphosphates such as sodium perphosphate, potassium perphosphate and ammonium perphosphate can be used. In this case, one kind can be used alone, or two or more kinds may be used in combination.

In introducing a cationic group of starch, for example, starch or a derivative thereof is a known cationizing agent such as 3-chloro-2-hydroxypropyl, trimethylammonium chloride, glycidyltrimethylammonium chloride, dimethylaminoethyl chloride, or the like. It can be obtained by reacting in the presence of

Examples of starch degrading enzymes used for enzymatic degradation include α-amylase, β-amylase, γ-amylase, and isoamylase produced by various bacteria, yeasts, animals and plants. Among these, α-amylase is most preferable in that it does not cause excessive low molecular weight substances or monosaccharides.

  The aqueous solution viscosity of the above-mentioned starch is not particularly limited, but usually the viscosity of an aqueous solution having a solid content of 10% at 25 ° C. is 1 to 1000 mPa · s, preferably 5 to 500 mPa · s in a Brookfield viscometer. Preferably, it is 10 to 100 mPa · s.

  Examples of celluloses include carboxymethyl cellulose, hydroxymethyl cellulose, and hydroxyethyl cellulose. These can be used in the form of powder or solution.

In addition, it is preferable that the coating liquid density | concentration at the time of coating the surface paper strength agent of this invention is 0.1 to 15 weight%. Coating weight sizing degree of the base paper, it can appropriately be set considering the other, 0.05-5 g / ^{m 2} typically with solids, preferably 0.1-2 g / ^{m 2.}

<Surface sizing agent>
As the surface sizing agent, a known and commonly used anionic surface sizing agent or cationic surface sizing agent can be used. By using these when a size effect is required, the size effect can be imparted while preventing a papermaking pitch trouble due to the use of an internally added sizing agent.

Representative examples of anionic surface sizing agents include styrene- (meth) acrylic acid copolymers, alkyl (meth) acrylates, which are copolymers of hydrophobic monomers and unsaturated monomers containing carboxyl groups. Alkali saponified products such as (meth) acrylic acid copolymers, styrene-maleic acid copolymers, α-olefin-maleic acid copolymers, or anions such as styrene-alkyl (meth) acrylate copolymers Emulsifiable emulsions. The anionization degree is preferably 0.1 to 6.0 meq / g. More preferably, it is 0.3-4.0 meq / g. Among these anionic surface sizing agents, one kind may be used alone, or two or more kinds may be used in combination. Furthermore, you may use together alkenyl succinic anhydride and its salt, and 2-oxetanone type compounds.

A typical example of the cationic surface sizing agent is a styrene-dimethylaminoethyl (meth) acrylate copolymer that is a copolymer of a hydrophobic monomer and an unsaturated monomer containing a tertiary and / or quaternary amino group. Examples thereof include a polymer, a quaternized product such as an alkyl (meth) acrylate-dimethylaminoethyl (meth) acrylate copolymer, or a cationic emulsion of a styrene-alkyl (meth) acrylate copolymer. The degree of cationization is preferably 0.3 to 2.0 meq / g. More preferably, it is 0.5-1.5 meq / g. Among these cationic surface sizing agents, one kind may be used alone, or two or more kinds may be used in combination. Furthermore, fatty acid amides and 2-oxetanone compounds may be used in combination.

In terms of size effect, a styrene- (meth) acrylic acid copolymer is used as the anionic surface sizing agent, and a quaternized product of styrene-dimethylaminoethyl (meth) acrylate copolymer is used as the cationic surface sizing agent. It is preferable to use it.

The hydrophobic monomer includes a water-insoluble monomer. Examples of the hydrophobic monomer include styrene and styrene derivatives such as α-methylstyrene, vinyltoluene, divinylbenzene, alkyl (meth) acrylate, cyclic alkyl (meth) acrylate, maleic acid and dialkyl diesters of fumaric acid, carbon Examples thereof include vinyl esters such as tertiary vinyl carboxylate and vinyl propionate, N alkyl (meth) acrylamides, α-olefins, and methyl vinyl ether. One of these various hydrophobic monomers can be used alone, or two or more of them can be mixed and used.

Examples of the unsaturated monomer containing a carboxyl group include monocarboxylic acids such as acrylic acid, methacrylic acid, maleic acid monoester, fumaric acid monoester, itaconic acid monoester, and maleic acid, fumaric acid. Examples thereof include polyvalent carboxylic acids such as acid, itaconic acid, citraconic acid and crotonic acid. One of these unsaturated monomers containing various carboxyl groups can be used alone, or two or more of them can be used in combination.

  Examples of the unsaturated monomer containing a tertiary amino group include dialkyl such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, and diethylaminopropyl (meth) acrylate. Examples include aminoalkyl (meth) acrylates, dialkylaminoalkyl (meth) acrylamides such as dimethylaminopropyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide, and salts thereof. These salts include inorganic acid salts such as hydrochloride and sulfate, and organic acid salts such as formate and acetate.

  Further, as the unsaturated monomer having a tertiary amino group, vinyl monomers having the secondary amino group such as diallylamine and dimethallylamine, alkyl halides such as methyl chloride and methyl bromide, benzyl chloride, and benzyl bromide And monomers such as aralkyl halides such as dimethylsulfate, alkylsulfuric acid such as diethylsulfuric acid, epichlorohydrin, and the like to form tertiary amine acid salts.

  Examples of the unsaturated monomer having a quaternary ammonium salt include di (meth) allyldimethylammonium chloride and di (meth) allyldiethylammonium chloride.

  Examples of the unsaturated monomer having a quaternary ammonium salt include unsaturated monomers obtained by reacting the unsaturated monomer having a tertiary amino group with a quaternizing agent. Examples of the quaternizing agent include alkyl halides such as methyl chloride and methyl bromide, aralkyl halides such as benzyl chloride and benzyl bromide, alkyl sulfates such as dimethyl sulfate and diethyl sulfate, epichlorohydrin, 3-chloro- Examples include 2-hydroxypropyltrimethylammonium chloride and glycidyltrialkylammonium chloride.

  Specific examples include (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloyloxypropyldimethylbenzylammonium chloride, and the like.

  These unsaturated monomers having a tertiary amino group or a quaternary ammonium salt may be used alone or in combination of two or more.

  The concentration of the surface sizing agent in the coating solution used when applying the surface sizing agent is usually 0.1 to 5% by weight, preferably 0.2 to 1% by weight.

Also, usually, the coating weight is, 0.01 to 1 g / ^{m 2} in solids, preferably 0.02~0.1g / ^{m 2.} Within the above range, the size effect is particularly good.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In addition, when there is no notice in particular, it is a basis of weight.

<Stain adhesion test>
Example 1-1A
Place a weighed 250 mesh wire inside a 500 cc beaker, and add 400 cc of Canadian standard freeness 340, 9.9% ash content, 2.4% density cardboard waste paper pulp. A THF solution prepared by leaching the adhesive sheet of a courier label as tetrahydrofuran (hereinafter abbreviated as THF) as a model pitch of an adhesive while eluting the adhesive component while stirring at 400 rpm with a three-one motor. Is used as a model pitch in the soil adhesion test, and THF solution is used as a solid component of the sticky substance and 0.8% dry to pulp (hereinafter, the same applies when added to pulp slurry, and the indication may be omitted) Is added) and stirred at 40 ° C. for 30 minutes. After completion of the stirring, the pH of the pulp slurry (measured using HM-20P manufactured by Toa KDD Corporation, hereinafter omitted) was measured. An indicator of ethanol solvent mixed with methyl red and bromocresol green is added to the filtrate obtained by suction filtration with 5A filter paper (manufactured by Toyo Filter Paper Co., Ltd.), and the filtrate is stirred while gently stirring the liquid. Titrate with 1 / 50N sulfuric acid until the color changes from blue to red, and the amount of alkali components in the filtrate is converted to calcium carbonate for alkalinity (mg CaCO ₃ / l) (this value is expressed in ppm below) The alkalinity was determined by the formula: titration (ml) × 1000 / filtrate (ml). Further, the removed wire was lightly washed with water, dried at 110 ° C. for 30 minutes, and weighed to measure the amount of dirt attached to the wire. These measurement results are shown in Table 1.

Example 1-2A to Example 1-9A
In the soil adhesion test of Example 1-1A, THF solution was added as an adhesive component solid content to 0.8% dry pulp, and then the chemicals shown in Table 1 were added to the pulp slurry and 40 minutes at 40 ° C. Except for stirring, in the same manner as in Example 1-1A, the values of dirt adhesion amount and alkalinity were obtained. The results are shown in Table 1.

Example 1-10A
In the soil adhesion test of Example 1-1A, soil adhesion amount and alkalinity values were obtained in the same manner as in Example 1-1A, except that the pH of the pulp slurry was adjusted to 8.0 using an aqueous sodium hydroxide solution. . The results are shown in Table 1.

Example 1-11A
In the dirt adhesion test of Example 1-1A, dirt was used in the same manner as in Example 1-1A, except that the amount of sulfuric acid band used was 0.5% and the pulp slurry was adjusted to pH 7.4 with an aqueous sodium hydroxide solution. The amount of adhesion and the value of alkalinity were obtained. The results are shown in Table 1.

Comparative Example 1-1A
In the soil adhesion test of Example 1-1A, the soil adhesion amount and the alkalinity values were obtained in the same manner as in Example 1-1A, except that the sulfuric acid band was used and the pulp slurry was adjusted to pH 5.7. The results are shown in Table 1.

Comparative Example 1-2A
In the soil adhesion test of Example 1-1A, values of soil adhesion and alkalinity were obtained in the same manner as in Example 1-1A, except that the sulfuric acid aqueous solution was used and the pulp slurry was adjusted to pH 6.0. The results are shown in Table 1.

Comparative Example 1-3A
Example 1-1 In the soil adhesion test of A, it was considered that after adding 0.8% to pulp absolute dryness with THF solution as a solid component of the sticky substance, it significantly affects the soiling of the alkenyl succinic anhydride sizing agent. A component obtained by extracting THF from a sizing agent as a solid content was added to 0.8% dry pulp, and the amount of dirt adhered was the same as in Example 1-1A except that the mixture was stirred at 40 ° C. for 30 minutes. The alkalinity value was obtained. The results are shown in Table 1.

  From these results, it can be seen that if the sizing agent is not used, the amount of dirt attached is reduced, and further, the amount of dirt attached is reduced by adjusting the pH of the pulp slurry to 6.5 to 8.5. It was also found that the amount of dirt adhered decreased by using a paper strength agent, a yield agent, and a pitch control agent.

<Recycling experiment>
In order to reproduce the increase in electrical conductivity due to accumulation of chemicals in white water, a recycling experiment was conducted by the following method.
Canadian standard freeness 340, 9.1% ash content corrugated waste paper pulp was dehydrated to produce a 20% concentration dehydrated pulp. After adding 25 g of this dehydrated pulp and industrial water (conductivity 25 mS / m (measured using CM-14P manufactured by Toa KDD Corporation, hereinafter omitted)) into a household mixer, after adding 3% sulfuric acid band , And stirred at 70V for 30 seconds. The obtained pulp slurry was dehydrated under reduced pressure with a 60 mesh wire to obtain white water.

  In a series of experiments using the above dehydrated pulp, an experiment was performed under the same conditions except that white water obtained instead of industrial water was used, and this experiment was repeated 30 times. The obtained white water was used for the next repeated experiment, and 3% sulfuric acid band was added for each repetition. The conductivity of white water obtained after repeating 30 times was measured and found to be 270 mS / m. Although the electrical conductivity of white water of the actual paper machine using the sulfuric acid band varies depending on the sulfuric acid band addition rate, closed rate, etc., it is usually 260 to 400 mS / m. It is thought that the chemical accumulation in white water could be reproduced. This is designated as Comparative Example 1-1B.

Example 1-1B
In Comparative Example 1-1B, the same procedure was performed except that the sulfuric acid band was not used. The measurement results are shown in Table 1.

Examples 1-2B to 1-9B
The recycling experiment of Example 1-1B was performed in the same manner except that the chemicals shown in Table 1 were used. The measurement results are shown in Table 1.

Example 1-10B
In Example 1-1B, the same procedure as in Example 1-1 was performed except that the pH of the pulp slurry was adjusted to 8.0 using an aqueous sodium hydroxide solution. The measurement results are shown in Table 1.

Example 1-11B
In Example 1-1B, the same procedure as in Example 1-1 was performed, except that the amount of sulfuric acid band used was 0.5% and the pulp slurry was adjusted to pH 7.4 with a sodium hydroxide aqueous solution. The measurement results are shown in Table 1.

Comparative Example 1-2B
Comparative Example 1-1B was carried out in the same manner except that the pH was adjusted to 6.0 using sulfuric acid. The measurement results are shown in Table 1.

  It was shown that the electrical conductivity after the recycling experiment was greatly influenced by the addition rate of sulfuric acid band. However, the electrical conductivity of most chemicals such as paper strength agents, retention agents, and pitch control agents was higher than that when no chemicals were added. It was found that there was not much difference between the two.

  In the case of an actual paper machine having an electric conductivity exceeding 260 mS / m, it is preferable to keep the electric conductivity of white water at 250 mS / m or less in order to prevent the scale in consideration of the scale trouble of calcium sulfate. it is conceivable that. For this purpose, it is considered preferable not to use a sulfuric acid band or to suppress it to 1% or less even if it is used.

Explanation of abbreviations in Table 1 Cato304 (glue): Nippon NSC Co., Ltd. Cationic starch was cooked and used as a paste.
Cato 3210 (glue): manufactured by Nippon NSC Co., Ltd. Amphoteric starch was cooked and used as a paste.
DH4160: Hoffman modified acrylamide paper strength agent DS4404 made by Seiko PMC Co., Ltd. Amphoteric acrylamide paper strength agent made by Seiko PMC Co., Ltd. (having an anionic group and a cationic group, and the cationic group is compared with the anionic group) Many polyacrylamide paper strength agents)
AC7314: Organic cationic pitch control agent PC7407 manufactured by Seiko PMC Co., Ltd. Inorganic (bentonite) pitch control agent RD7153 manufactured by Seiko PMC Co., Ltd. Organic cationic retention agent ASA: alkenyl succinic anhydride manufactured by Seiko PMC Co., Ltd. System sizing agent in THF solution Note: Regarding the experiment using ASA, the recycling experiment was not performed because THF was used.

Example 2-1
Canadian Standard Freeness 360 mixed with 20 unbleached kraft pulp and 80 cardboard waste paper pulp, 5.9% ash pulp, amphoteric acrylamide paper strength agent (with anionic and cationic groups, Also, 0.2% each of polyacrylamide-based paper strength agent DS4404 (manufactured by Seiko PMC Co., Ltd.) and Hoffman modified acrylamide-based paper strength agent DH4160 (manufactured by Seiko PMC Co., Ltd.) is added. And diluted to 0.8% with water having an electric conductivity of 110 mS / m. The pulp slurry had a pH of 7.1 and an alkalinity of 196 ppm. Further, the pulp slurry was hand-made with a noble and wood sheet machine so as to have a basis weight of 70 g / m ² and dried under conditions of a drum dryer at 110 ° C. for 90 seconds. The obtained paper was conditioned in a constant temperature and humidity chamber at 23 ° C. and 50 RH% for 24 hours, and then the specific burst strength was measured. The results are shown in Table 2. The specific burst strength is a result of measurement according to JIS P 8131. Hereinafter, when the specific burst strength is simply referred to, it is obtained in the same manner. In addition, for adjusting the electric conductivity of the service water, calcium sulfate was used up to 150 mS / m, and sodium sulfate was further used in the case of 150 mS / m or more. Hereinafter, the conductivity was adjusted in the same manner.

Comparative Example 2-1
Papermaking was carried out under the same conditions as in Example 2-1, except that 3% of a sulfuric acid band was added to the pulp and the conductivity of the water shown in Table 2 was changed. The measurement results of pH, alkalinity, and specific burst strength are shown in Table 2 in the same manner as in Example 2-1.

Comparative Example 2-2
Papermaking was performed under the same conditions except that an aqueous sodium hydroxide solution was used so as to adjust the pH to 9.0 in Example 2-1, and the conductivity of the water was changed as shown in Table 2. The measurement results of alkalinity and specific burst strength are shown in Table 2 in the same manner as in Example 2-1.

Examples 2-2 to 2-8
Papermaking was carried out under the same conditions as in Example 2-1, except that the type of paper strength agent, the addition ratio to the pulp, and the electric conductivity of water were changed as shown in Examples 2-2 to 2-8 in Table 3. Table 3 shows the measurement results of pH, alkalinity, and specific burst strength in the same manner as in Example 2-1.

Example 2-9
Papermaking was performed under the same conditions except that 0.5% of a sulfuric acid band was added to the pulp in Example 2-2 and the electric conductivity of the water was changed as shown in Example 2-9 in Table 3. Table 3 shows the measurement results of pH, alkalinity, and specific burst strength in the same manner as in Example 2-1.

Example 2-10
Papermaking was performed under the same conditions except that 0.5% of a sulfuric acid band was added to the pulp in Example 2-3 and the electric conductivity of the water was changed as shown in Example 2-10 of Table 3. Table 3 shows the measurement results of pH, alkalinity, and specific burst strength in the same manner as in Example 2-1.

Example 2-11
Papermaking was carried out under the same conditions as in Example 2-1, except that a 0.5% sulfuric acid band was added to the pulp and an aqueous sodium hydroxide solution was used so as to adjust the pH to 7.1. Table 3 shows the measurement results of alkalinity and specific burst strength in the same manner as in Example 2-1.

Explanation of abbreviations in Table 3 DH4160: Hoffman modified acrylamide paper strength agent DS4404 made by Seiko PMC Co., Ltd. Amphoteric acrylamide paper strength agent made by Seiko PMC Co., Ltd. (having an anionic group and a cationic group, and a cationic group Is a polyacrylamide type paper strength agent with more anionic groups)
DA4119: Anionic acrylamide paper strength agent manufactured by Seiko PMC Co., Ltd. DS4405: Amphoteric acrylamide system paper strength agent manufactured by Seiko PMC Co., Ltd. (having an anionic group and a cationic group, and the anionic group is compared with the cationic group) Many polyacrylamide paper strength agents)

Example 3-1.
Canadian Standard Freeness 380, corrugated waste paper pulp with 10.0% ash content, 0.6% cationized starch Cato304 (made by Nippon NSC Co., Ltd.) cooked and pasted as a paper strength agent, Hoffman modified acrylamide paper 0.1% strength agent DH4160 (manufactured by Seiko PMC Co., Ltd.) was added and diluted to 0.8% with water having an electric conductivity of 170 mS / m. The pulp slurry had a pH of 7.3 and an alkalinity of 301 ppm. Further, the pulp slurry was hand-made with a noble and wood sheet machine to a basis weight of 80 g / m ² and dried under conditions of a drum dryer at 110 ° C. for 90 seconds. The resulting paper was conditioned for 24 hours in a constant temperature and humidity chamber at 23 ° C. and 50 RH%, and then the specific burst strength was measured. The results are shown in Table 4.

Comparative Example 3-1
Papermaking was performed under the same conditions except that 3% of a sulfuric acid band was added in Example 3-1 and the conductivity of the water shown in Table 4 was changed. The measurement results of pH, alkalinity, and specific burst strength are shown in Table 4 in the same manner as in Example 3-1.

Comparative Example 3-2
Papermaking was performed under the same conditions except that an aqueous sodium hydroxide solution was used so as to adjust the pH to 9.0 in Example 3-1, and that the conductivity of water was changed as shown in Table 4. Table 4 shows the measurement results of alkalinity and specific burst strength in the same manner as in Example 3-1.

Examples 3-2 to 3-10
Papermaking was carried out under the same conditions as in Example 3-1, except that the type and addition rate of the paper strength agent and the electric conductivity of water were changed as shown in Examples 3-2 to 3-10 in Table 5. The measurement results of pH, alkalinity, and specific burst strength are shown in Table 5 in the same manner as in Example 3-1.

Explanation of abbreviations in Table 5 Raw starch (powder): Raw corn starch was used as it was.
Cato 304 (powder): Cationic starch produced by Nippon NSC Co., Ltd. was used as it was.
Cato304 (glue): manufactured by Nippon NSC Co., Ltd. Cationic starch was cooked and used as a paste.
Cato 3210 (glue): manufactured by Nippon NSC Co., Ltd. Amphoteric starch was cooked and used as a paste.
Phosphate starch (powder): Urea phosphate corn starch was used as it was.
DS4404: Amphoteric acrylamide paper strength agent manufactured by Seiko PMC Co., Ltd. (polyacrylamide paper strength agent having an anionic group and a cationic group and having more cationic groups than anionic groups)
DS4405: Amphoteric acrylamide paper strength agent manufactured by Seiko PMC Co., Ltd. (polyacrylamide paper strength agent having an anionic group and a cationic group, and having more anionic groups than cationic groups)
DH4160: Hoffman modified acrylamide paper strength agent manufactured by Seiko PMC Co., Ltd.

Example 4-1
Cationic standard freeness 355 mixed with 50 corrugated waste paper pulp and magazine waste paper pulp at a ratio of 50%, pulp with an ash content of 14.2%, sulfuric acid band 0.5%, cations cooked and pasted as a paper strength agent 0.6% of modified starch Cato304 (manufactured by NSC Japan, Inc.) and 0.1% of Hoffman modified acrylamide paper strength agent DH4160 (manufactured by Seiko PMC Co., Ltd.) were added, and 0.8 water was added with water having a conductivity of 150 mS / m. Diluted to%. The pulp slurry had a pH of 7.0 and an alkalinity of 279 ppm. Further, the pulp slurry was hand-made with a noble and wood sheet machine to a basis weight of 80 g / m ² and dried under conditions of a drum dryer at 110 ° C. for 90 seconds. The resulting paper was conditioned for 24 hours in a constant temperature and humidity chamber at 23 ° C. and 50 RH%, and then the specific burst strength was measured. The results are shown in Table 6.

Comparative Example 4-1
In Example 4-1, 4% of a sulfuric acid band was added, and papermaking was performed under the same conditions except that the conductivity of water was changed as shown in Table 6. Table 6 shows the measurement results of pH, alkalinity, and specific burst strength in the same manner as in Example 4-1.

Comparative Example 4-2
Papermaking was performed under the same conditions except that an aqueous sodium hydroxide solution was used so as to adjust the pH to 9.0 in Example 4-1, and that the conductivity of water was changed as shown in Table 6. Table 6 shows the measurement results of alkalinity and specific burst strength in the same manner as in Example 4-1.

Examples 4-2 to 4-10
Papermaking was performed under the same conditions as in Example 4-1, except that the type and addition rate of the paper strength agent and the conductivity of water were changed as shown in Examples 4-2 to 4-10 in Table 7. Table 7 shows the measurement results of pH, alkalinity, and specific burst strength in the same manner as in Example 4-1.

Explanation of abbreviations in Table 7 Raw starch (powder): Raw corn starch was used as a powder.
Cato 304 (powder): Cationic starch produced by Nippon NSC Co., Ltd. was used as it was.
Cato304 (glue): manufactured by Nippon NSC Co., Ltd. Cationic starch was cooked and used as a paste.
Cato 3210 (glue): manufactured by Nippon NSC Co., Ltd. Amphoteric starch was cooked and used as a paste.
Phosphate starch (powder): Urea phosphate corn starch was used as it was.
DS4404: Amphoteric acrylamide paper strength agent manufactured by Seiko PMC Co., Ltd. (polyacrylamide paper strength agent having an anionic group and a cationic group and having more cationic groups than anionic groups)
DS4405: Amphoteric acrylamide paper strength agent manufactured by Seiko PMC Co., Ltd. (polyacrylamide paper strength agent having an anionic group and a cationic group, and having more anionic groups than cationic groups)
DH4160: Hoffman modified acrylamide paper strength agent manufactured by Seiko PMC Co., Ltd.

Example 5-1
Canadian standard freeness 270, corrugated used paper pulp with ash content of 10.2%, amphoteric acrylamide paper strength agent (polyacrylamide type having both anionic groups and cationic groups and more cationic groups than anionic groups) Paper strength agent) DS4404 (manufactured by Seiko PMC Co., Ltd.) 0.1%, Hoffman modified acrylamide paper strength agent DH4160 (manufactured by Seiko PMC Co., Ltd.) 0.2% are added, and 0 with water of electric conductivity 150 mS / m. Dilute to 8%. The pulp slurry had a pH of 7.2 and an alkalinity of 303 ppm. Further, the pulp slurry was hand-made with a noble and wood sheet machine to a basis weight of 65.0 g / m ² and dried under conditions of a drum dryer at 110 ° C. for 90 seconds. The resulting paper was conditioned for 24 hours in a constant temperature and humidity chamber at 23 ° C. and 50 RH%, and then the specific burst strength was measured. The results are shown in Table 8.

Comparative Example 5-1
In Example 5-1, a 3% sulfuric acid band was added, and papermaking was performed under the same conditions except that the electric conductivity of water was changed as shown in Table 8. Table 8 shows the measurement results of pH, alkalinity, and specific burst strength in the same manner as in Example 5-1.

Comparative Example 5-2
Papermaking was performed under the same conditions except that an aqueous sodium hydroxide solution was used so as to adjust the pH to 9.0 in Example 5-1, and the electric conductivity of the water was changed as shown in Table 8. Table 8 shows the measurement results of alkalinity and specific burst strength in the same manner as in Example 5-1.

Examples 5-2 to 5-6
Papermaking was performed under the same conditions as in Example 5-1, except that the types and addition ratios of the pitch control agent and the retention agent were changed as shown in Examples 5-2 to 5-6 in Table 9. Table 9 shows the measurement results of pH, alkalinity, and specific burst strength in the same manner as in Example 5-1.

Explanation of abbreviations in Table 9 AC7314: Organic cationic pitch control agent PC7407 manufactured by Seiko PMC Co., Ltd. Inorganic (bentonite) pitch control agent RD7153 manufactured by Seiko PMC Co., Ltd. Organic cationic retention agent manufactured by Seiko PMC Co., Ltd. RD7160: manufactured by Seiko PMC Co., Ltd. Inorganic (silica) retention agent: not used.

Example 6-1
Using Canadian Standard Freeness 300, Kakohaku old paper pulp with an ash content of 17.3%, amphoteric acrylamide paper strength agent (having an anionic group and a cationic group, and the cationic group is compared to the anionic group) Many polyacrylamide-based paper strength agents) DS4404 and 0.1% strength strength paper DH4160 were added and diluted to 0.8% with water with a conductivity of 100 mS / m. The pulp slurry had a pH of 7.5 and an alkalinity of 396 ppm. Further, the pulp slurry was hand-made with a noble and wood sheet machine so as to have a basis weight of 70 g / m ² and dried under conditions of a drum dryer at 110 ° C. for 90 seconds. The resulting paper was conditioned for 24 hours in a constant temperature and humidity chamber at 23 ° C. and 50 RH%, and then the specific burst strength was measured. The results are shown in Table 10.

Comparative Example 6-1
In Example 6-1, papermaking was performed under the same conditions except that 5% sulfuric acid band was added to the upper white waste paper pulp and the electric conductivity of water was changed as shown in Table 10. Table 10 shows the measurement results of pH, alkalinity, and specific burst strength in the same manner as in Example 6-1.

Comparative Example 6-2
Papermaking was performed under the same conditions except that an aqueous sodium hydroxide solution was used so that the pH was adjusted to 9.0 in Example 6-1 and the electrical conductivity of the water was changed as shown in Table 10. Table 10 shows the measurement results of alkalinity and specific burst strength in the same manner as in Example 6-1.

Examples 6-2 to 6-6
Papermaking was performed under the same conditions except that the types and addition ratios of the pitch control agent and the retention agent in Example 6-1 were changed as shown in Examples 6-2 to 6-6 in Table 11. Table 11 shows the measurement results of pH, alkalinity, and specific burst strength in the same manner as in Example 6-1.

Explanation of abbreviations in Table 11 AC7314: Organic cationic pitch control agent PC7407 manufactured by Seiko PMC Co., Ltd. Inorganic (bentonite) pitch control agent RD7153 manufactured by Seiko PMC Co., Ltd. Organic cationic retention agent manufactured by Seiko PMC Co., Ltd. RD7160: manufactured by Seiko PMC Co., Ltd. Inorganic (silica) retention agent: not used.

Examples of surface coating will be described below.

Synthesis Example 1 Production of Anionic Surface Sizing Agent (S-1) In a 1 liter four-necked flask equipped with a stirrer, thermometer, reflux condenser and nitrogen inlet tube, 29.1 parts of water, isopropyl alcohol 93 2 parts, 76.9 parts (42 mol%) of styrene, 64.8 parts (20 mol%) of 2-ethylhexyl acrylate, and 60.2 parts (38 mol%) of 80% aqueous acrylic acid solution were added under a nitrogen stream. The temperature was raised to 60 ° C. with mixing and stirring.

At 60 ° C, 3.3 parts of azobisisobutyronitrile and 2.3 parts of ammonium persulfate were added, and the temperature was raised to 80 ° C. Hold for 5 hours. An additional 2.3 parts of ammonium persulfate was added and held for 1 hour to complete the polymerization reaction. Subsequently, 38.3 parts of 48% caustic potash aqueous solution and 320 parts of water were added, isopropyl alcohol was distilled off, 22.5 parts of 25% aqueous ammonia solution and 119.7 parts of water were added, and the anionization degree at a concentration of 25% was 3.2 meq / An aqueous solution of an anionic surface sizing agent (S-1) as g was obtained.

(Synthesis Example 2) Production of Cationic Surface Sizing Agent (S-2) In the same container as in Synthesis Example 1, 137.3 parts (85 mol%) of styrene and 36.6 parts (15 mol%) of dimethylaminoethyl methacrylate , Dimethyl-2,2-azobis (2-methylpropionate) (manufactured by Wako Pure Chemical Industries, Ltd. V601, azo catalyst) and 59.5 parts of toluene, and maintained at 80 ° C. for 3 hours, then V601 Was added at 0.5 parts and held at the same temperature for 2 hours.

Next, 14 parts of acetic acid was added, 368 parts of water was added to obtain an emulsion, and then the temperature was further raised to distill off toluene.
Next, 76 parts of water was added, 21.5 parts of epichlorohydrin was added and reacted at 80 ° C. for 1.5 hours, and 365 parts of water was added to give a cationization degree of 21.2% solids of 0.9 meq / g. A cationic surface sizing agent (S-2) was obtained.

(Synthesis Example 3) Production of anionic surface paper strength agent (ST-1) In a 1 liter four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, 394 parts of water, 50% acrylamide 398 parts (93.4 mol%), itaconic acid 23.4 parts (6.0 mol%), sodium methallylsulfonate 2.9 parts (0.6 mol%) and urea 45 parts were charged. Next, the temperature was raised to 50 ° C. in a nitrogen gas atmosphere, and 6.9 parts of 5% ammonium persulfate aqueous solution and 3.6 parts of 2% sodium metabisulfite aqueous solution were added to start the reaction. The temperature was raised to 0 ° C., and then the reaction was carried out for 2 hours while maintaining 80 ° C. 29 parts of water was added to the obtained product, and the pH was adjusted to 7.0 with a 30% aqueous sodium hydroxide solution. The solid content was 30.1% and the viscosity was 4,500 mPa · s (25 ° C., using Brookfield rotary viscometer). ) Polyacrylimide anionic surface strength agent (ST-1).

(Synthesis Example 4) Production of cationic surface strength agent (ST-2) In the same apparatus as in Synthesis Example 1, 550 parts of water, 13.5 parts of 65% diallyldimethylammonium chloride aqueous solution (2.0 mol%), 377 parts (97.6 mol%) of 50% aqueous acrylamide solution, 2.6 parts (0.4 mol%) of 75% 2-propen-1-aminium, N-hydroxyethyl-N, N, 2-trimethyl chloride solution ). Next, the temperature was raised to 50 ° C. under a nitrogen gas atmosphere, and 3.1 parts of a 20% aqueous ammonium persulfate solution and 6.5 parts of a 2% aqueous sodium metabisulfite solution were added to start the reaction, followed by 90 minutes in 30 minutes. The temperature was raised to 0 ° C., and then reacted for 2 hours while maintaining 85 ° C. 47 parts of water was added to the obtained product, pH was adjusted to 7.0 with a 20% aqueous sodium hydroxide solution, the solid content was 20.2%, and the viscosity was 4,200 mPa · s (25 ° C., Brookfield). A polyacrylamide-based cationic surface strength agent (ST-2) was obtained.

Example 7-1
The anionic surface sizing agent (S-1) obtained in Synthesis Example 1 was diluted with warm water to the base paper prepared in Example 5-6 and Example 6-6, and the anionic surface sizing agent (S-1 The coating liquid adjusted so that the solid content concentration is 0.25% and the temperature is 50 ° C. is applied using a 2-roll size press and dried with a drum dryer (80 ° C., 30 seconds). Thus, a coated paper was obtained. The solid content coating amount of the anionic surface sizing agent (S-1) of this coated paper was 0.05 g / m ² . After the humidity was adjusted for 24 hours in a constant temperature and humidity room at 23 ° C. and 50 RH%, the coated paper was subjected to various evaluation tests. The evaluation results of the paper coated on the base paper prepared in Example 5-6 are shown in Table 12, and the evaluation results of the paper coated on the base paper prepared in Example 6-6 are shown in Table 13. Also in the following examples, after coating in the same manner, the evaluation results of the paper applied to various evaluation tests and coated on the base paper prepared in Example 5-6 were prepared in Table 12 and in Example 6-6. The evaluation results of the paper coated on the base paper are shown in Table 13.

Example 7-2
The same method as in Example 7-1 was used except that the anionic surface sizing agent (S-1) of Example 7-1 was changed to the cationic surface sizing agent (S-2) obtained in Synthesis Example 2. Coating and testing. The coated amount of the cationic surface sizing agent (S-2) in this coated paper was 0.05 g / m ² .

Example 7-3
The anionic surface sizing agent (ST-1) obtained in Synthesis Example 3 was used as the anionic surface sizing agent (S-1) of Example 7-1, and the anionic surface sizing agent (ST-1) was applied. Coating and testing were performed using the same method as in Example 1 except that the solid content concentration to be worked was changed to 1.0%. The solid content coating amount of the anionic surface strength agent (ST-1) of this coated paper was 0.2 g / m ² .

Example 7-4
The same method as in Example 7-3 except that the anionic surface paper strength agent (ST-1) of Example 7-3 was changed to the cationic surface paper strength agent (ST-2) obtained in Synthesis Example 4. Coating and testing were conducted using The solid content coating amount of the cationic surface strength agent (ST-2) of this coated paper was 0.2 g / m ² .

Example 7-5
Coating was carried out in the same manner as in Example 7-3, except that the anionic surface strength agent (ST-1) of Example 7-3 was changed to a cooked oxidized starch (MS3800: manufactured by Nippon Shokuhin Kako Co., Ltd.). Work and test were conducted. The solid content of oxidized starch in this coated paper was 0.2 g / m ² .

Example 7-6
Coating was performed using the same method as in Example 7-3, except that the anionic surface strength agent (ST-1) in Example 7-3 was changed to cooked polyvinyl alcohol (PVA117: manufactured by Kuraray Co., Ltd.). A test was conducted. The solid content of polyvinyl alcohol in this coated paper was 0.2 g / m ² .

Example 7-7
The coating liquid was prepared so that the solid content concentration of the anionic surface strength agent (ST-1) was 1.0% and the solid content concentration of the anionic surface sizing agent (S-1) was 0.25%. Except for the above, coating and testing were performed using the same methods as in Example 7-1. The solid content coating amount of the anionic surface strength agent (ST-1) of this coated paper is 0.2 g / m ^2, and the solid content coating amount of ^the anionic surface sizing agent (S-1) is 0. 0.05 g / m ² .

Example 7-8
The coating liquid was prepared so that the solid content concentration of the cationic surface strength agent (ST-2) was 1.0% and the solid content concentration of the cationic surface sizing agent (S-2) was 0.25%. Except for the above, coating and testing were performed using the same methods as in Example 7-1. The solid content of the cationic surface strength agent (ST-2) of this coated paper is 0.2 g / m ^2, and the solid content of ^the cationic surface sizing agent (S-2) is 0. 0.05 g / m ² .

Example 7-9
Except that the coating liquid was prepared so that the solid content concentration of the cooked oxidized starch (MS3800) was 1.0% and the solid content concentration of the anionic surface sizing agent (S-1) was 0.25%. Coating and testing were performed using the same method as in Example 7-1. The solid content of oxidized starch (MS3800) of this coated paper is 0.2 g / m ² , and the solid content of the anionic surface sizing agent (S-1) is 0.05 g / m ² . there were.

Example 7-10
Except that the coating liquid was prepared so that the solid content concentration of the cooked polyvinyl alcohol (PVA117) was 1.0% and the solid content concentration of the anionic surface sizing agent (S-1) was 0.25%. Coating and testing were performed using the same method as in Example 7-1. The solid coating amount of polyvinyl alcohol (PVA117) of this coated paper is 0.2 g / m ^2, and the solid coating amount of ^the anionic surface sizing agent (S-1) is 0.05 g / m ² . there were.

<Evaluation method>
Cobb sizing degree: compliant with JIS P 8140.
Specific burst strength: Conforms to JIS P 8131.
Surface strength:
Dry pick: RI printing tester, nip width 10mm
Ink: FINE INK. (Dainippon Ink and Chemicals, IGT printing aptitude) V. = 20
The paper peeled state after printing was observed with the naked eye, and 5 was evaluated as excellent and 1 was evaluated as inferior.

Explanation of Abbreviations in Table 12 S-1: Anionic surface sizing agent of Synthesis Example 1 S-2: Cationic surface sizing agent of Synthesis Example 2 ST-1: Anionic surface strength agent ST-2 of Synthesis Example 3 : Cationic surface strength agent MS3800 of Synthesis Example 4: Oxidized starch PVA117 manufactured by Nippon Shokuhin Kako Co., Ltd .: Polyvinyl alcohol manufactured by Kuraray Co., Ltd.
-: Not used.

Explanation of Abbreviations in Table 13 S-1: Anionic surface sizing agent of Synthesis Example 1 S-2: Cationic surface sizing agent of Synthesis Example 2 ST-1: Anionic surface paper strength agent ST-2 of Synthesis Example 3 : Cationic surface strength agent MS3800 of Synthesis Example 4: Oxidized starch PVA117 manufactured by Nippon Shokuhin Kako Co., Ltd .: Polyvinyl alcohol manufactured by Kuraray Co., Ltd.
-: Not used.

Claims (8)

(1) pH 6.5-8.5
(2) Alkalinity 50-400ppm
(3) Conductivity 50-250mS / m
Using pulp slurry of
(4) A method for producing paperboard, wherein papermaking is performed without adding an internally added sizing agent to the pulp slurry. A paperboard manufacturing method according to claim 1, wherein a paper strength agent is added. The method for producing a paperboard according to claim 1 or 2, wherein acrylamide polymers and / or starches are added. A method for producing paperboard according to any one of claims 1 to 3, wherein a pitch control agent is added. A method for producing paperboard according to any one of claims 1 to 4, wherein a yield agent is added. The method for producing paperboard according to any one of claims 1 to 5, wherein an aluminum compound is not used or 1% by weight or less based on the solid content of the pulp slurry. The method for producing a paperboard according to any one of claims 1 to 6, wherein a surface paper strength agent and / or a surface sizing agent is used. Paperboard obtained using the method for producing paperboard according to claim 1.