JP2007113126A - Method for producing paperboard - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing paperboard equipped with water repellent-processing aptitude, while avoiding scale trouble and pitch trouble in a papermaking process and also having an excellent inter-laminar strength. <P>SOLUTION: This method for producing laminated paperboard is characterized in that (1) its surface layer is prepared by papermaking in the presence of a sizing agent at ≥4 and <6.5 pH, and (2) any of the other layers is prepared by papermaking in the presence of a primary and/or secondary amino group-containing polymer or in the co-presence of the primary and/or secondary amino group-containing polymer and a sizing agent at pH 6.5-8.5. Thereby, it becomes possible to produce the paperboard having the excellent inter-laminar strength and water repellent-processing aptitude, while avoiding the scale trouble and pitch trouble in the papermaking system. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing paperboard, and more particularly to a method for manufacturing paperboard having water repellent processing suitability and excellent interlayer strength while avoiding scale trouble and pitch trouble in papermaking.

  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.

  The sizing agent is a rosin-based sizing agent that is compatible with high pH papermaking, but the effect is not sufficient, and the papermaking pH fluctuates due to fluctuations in the calcium carbonate content in the wastepaper, and the size property is not stable. Have In addition, due to the progress of closure, calcium ions and sulfate ions derived from sulfate bands and calcium carbonate accumulate in the system, and as a result, the fixing rate of rosin-based sizing agents has dropped, and unfixed rosin-based sizing agents Paper-making foaming troubles caused by the problem are also a problem. This accumulation of calcium ions is a cause of reducing the effect of the acrylamide paper strength enhancer.

In order to avoid the above-mentioned problems, a paper slurry is made from a pulp slurry containing calcium carbonate in the presence of a specific rosin emulsion sizing agent, a sulfuric acid band and a chelating agent under neutral conditions at pH 6 to 8 (for example, patents) As a paper strength enhancer used when producing a paperboard having excellent paper strength from a pulp slurry containing calcium ions, the N substituent does not contain an ionic group and exhibits N substitution. An ionic (meth) acrylamide copolymer containing a specific amount of N-substituted (meth) acrylamide having 4 to 20 carbon atoms in the group (see, for example, Patent Document 2), a specific phosphate group (Meth) acrylamide polymer containing (for example, see Patent Document 3), pulp slurry containing waste paper pulp, water-soluble lignin and specific as a paper strength enhancer Meth) acrylamide are added copolymer technology (such as, but see Patent Document 4) have been proposed, the effect was not sufficient yet.
JP 2004-190149 A JP-A-9-209293 Japanese Patent Laid-Open No. 9-324391 JP 2002-194694 A

  Exterior liners (hereinafter sometimes abbreviated as liners) used for cold-corrugated cardboards and vegetable cardboards are made of kraft pulp and water-repellent agents made from wax-based emulsions on paper made from kraft pulp wastepaper. The water-repellent effect has been imparted by coating, and the water resistance strength has been improved. However, due to the increase in used paper raw materials for corrugated cardboard, it has become impossible to obtain a sufficient water repellent effect simply by applying a water repellent.

Conventionally, various papermaking methods have been studied and adopted in the papermaking process of paperboard to improve the quality of paper, and the paper is modified by an internal paper strength agent such as an acrylamide copolymer paper strength agent. Has been proposed (see, for example, Patent Document 5). However, these acrylamide copolymer paper strength agents are susceptible to the effects of anionic substances and suspended colloidal substances contained in waste paper, and there is a drawback that their performance cannot be exhibited when these amounts increase.
JP 2005-273790 A

An object of the present invention is to provide a method for producing a paperboard having water repellent processing suitability and excellent interlaminar strength while avoiding scale trouble and pitch trouble in a papermaking system.

That is, the present invention
(1) (A) The surface layer is made in the presence of a sizing agent at a pH of 4 or more and less than 6.5,
(B) Any of the other layers has a pH of 6.5 to 8.5 in the presence of a primary and / or secondary amino group-containing polymer, or a primary and / or secondary amino group-containing polymer and a sizing agent. A method of producing a laminated paperboard, characterized by papermaking;
(2) (C) The surface layer is made at a pH of 4 or more and less than 6.5 in the presence of a sizing agent,
(D) Any other layer has a pH of 6. in the presence of primary and / or secondary amino group-containing polymer and coagulant, or primary and / or secondary amino group-containing polymer, coagulant and sizing agent. A method for producing a laminated paperboard, wherein the papermaking is performed at 5 to 8.5,
(3) The sizing agent used for any other layer is at least one selected from rosin sizing agents, substituted cyclic dicarboxylic acid anhydride sizing agents, and 2-oxetanone sizing agents. 2) a method for producing paperboard,
(4) The method for producing a paperboard according to any one of (1) to (3), wherein the primary and / or secondary amino group-containing polymer is a cation-modified (meth) acrylamide polymer by Hofmann decomposition reaction,
(5) The method for producing a paperboard according to any one of (1) to (3), wherein the primary and / or secondary amino group-containing polymer is a copolymer of a diallylamine compound and (meth) acrylamide,
(6) The aluminum compound is used in an amount of 0.1 to 10% by weight in the surface layer of (E) based on the solid content of the pulp slurry, and (F) is not used in the other layers or is used in an amount of 1% by weight or less. (1) to (5) a method for producing a paperboard,
(7) The method for producing a paperboard according to (1) to (6), wherein the paperboard is a water-repellent liner base paper,
Is to provide.

By the method of the present invention, it is possible to produce a paperboard having excellent interlayer strength and suitability for water repellency while avoiding scale trouble and pitch trouble in papermaking.

<Paperboard>
The paperboard of the present invention may be a laminated paper having at least two layers of a surface layer and other layers, and the types of paperboard include liner base paper, core base paper, paper tube base paper, gypsum board base paper, coat A white board, an uncoated white board, a chip ball, etc. can be mentioned. Of these, liner base paper is preferable, and water-repellent liner base paper is particularly preferable.

The method for producing the paperboard of the present invention comprises:
The surface layer is essential to make paper in the pulp slurry in the presence of a sizing agent and at a pH of 4 or more and less than 6.5, and is preferably made at a pH of 4 or more and less than 6. In addition, any other layer is required to make paper in the pulp slurry in the presence of a primary and / or secondary amino group-containing polymer at pH 6.5 to 8.5.

<Pulp slurry>
The pulp slurry is a slurry of pulp 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, newspaper waste paper, magazine waste paper, cardboard waste paper or deinking Any used paper pulp such as used paper can be used. Moreover, as said pulp raw material, the mixture of the said pulp raw material and polyamide, polyester, polyolefin, etc. can also be used.

<Sizing agent>
The sizing agent used in the present invention is not particularly limited as long as it exhibits a size effect. Specifically, the rosin sizing agent, the substituted cyclic dicarboxylic acid anhydride sizing agent, the 2-oxetanone sizing agent, and the cationic synthetic size. An agent etc. are mentioned, These can be used individually or in 2 types or more. Among these, rosin-based sizing agents, substituted cyclic dicarboxylic acid anhydride-based sizing agents, and 2-oxetanone-based sizing agents are preferably used. In particular, a substituted cyclic dicarboxylic acid anhydride sizing agent is preferred.

（但し、式（１）中、Ｒ^１は炭素数５以上のアルキル基、アルケニル基、アラルキル基、またはアラルケニル基、ｎは２〜３の整数を表わす。）
の基本構造を有する置換環状ジカルボン酸無水物である。また、本発明においては、前記置換環状ジカルボン酸無水物の加水分解物をサイズ剤とするものも置換環状ジカルボン酸無水物系サイズ剤に含むものとする。 The substituted cyclic dicarboxylic acid anhydride sizing agent is a sizing agent mainly composed of a substituted cyclic dicarboxylic acid anhydride among the active ingredients as a sizing agent.
General formula (1)

(In the formula (1), R ¹ represents an alkyl group having 5 or more carbon atoms, an alkenyl group, an aralkyl group, or an aralkenyl group, and n represents an integer of 2 to 3)
It is a substituted cyclic dicarboxylic acid anhydride having the basic structure: Moreover, in this invention, what uses the hydrolyzate of the said substituted cyclic dicarboxylic acid anhydride as a sizing agent shall also be included in a substituted cyclic dicarboxylic acid anhydride type | system | group sizing agent.

  Specifically, alkyl succinic anhydrides such as hexadecyl succinic anhydride, octadecyl succinic anhydride, alkenyl succinic anhydrides such as hexadecenyl succinic anhydride, octadecenyl succinic anhydride, and Examples thereof include alkyl glutaric anhydrides such as hexadecyl glutaric anhydride, octadecyl glutaric anhydride, hexadecenyl glutaric anhydride, and octadecenyl glutaric anhydride.

  The substituted cyclic dicarboxylic acid anhydride can be emulsified and dispersed by a conventionally known method and used in the form of an emulsion. Moreover, there is no restriction | limiting in particular as the emulsification method, A conventionally well-known method is applicable. For example, a method of emulsifying and dispersing a substituted cyclic dicarboxylic acid anhydride containing a surfactant with water or (ionic) starch paste, a substituted cyclic dicarboxylic acid anhydride not containing a surfactant in the presence of a surfactant or Examples thereof include a method of emulsifying and dispersing a polyacrylamide emulsifier and / or (ionic) starch paste in the absence.

一般式（２）
（但し、式（２）中のＲ^１、Ｒ^２は、８〜２４個の炭素原子を有する同一または異なる飽和又は不飽和のアルキル基又はアルケニル基を示す。）
の基本構造を有するアルキル及び／又はアルケニルケテンダイマー、及び、
一般式（３）

（但し、式（３）中、ｎは自然数であり、通常１〜１０であり、Ｒ^３及びＲ^５は８〜２４個の炭素原子を有する同一または異なる飽和又は不飽和のアルキル基又はアルケニル基であり、Ｒ^４は４〜４０個の炭素原子を有する飽和又は不飽和のアルキル基又はアルケニル基である。）
の基本構造を有するアルキル及び／又はアルケニルケテンマルチマーの総称である。 The 2-oxetanone sizing agent is a sizing agent mainly composed of a 2-oxetanone compound among active ingredients as a sizing agent.

General formula (2)
(However, R ¹ and R ² in the formula (2) represent the same or different saturated or unsaturated alkyl group or alkenyl group having 8 to 24 carbon atoms.)
An alkyl and / or alkenyl ketene dimer having the basic structure:
General formula (3)

(In the formula (3), n is a natural number, usually 1 to 10, and R ³ and R ⁵ are the same or different saturated or unsaturated alkyl or alkenyl groups having 8 to 24 carbon atoms. And R ⁴ is a saturated or unsaturated alkyl or alkenyl group having ⁴ to 40 carbon atoms.)
It is a general term for alkyl and / or alkenyl ketene multimers having the basic structure:

The 2-oxetanone compound is produced using a saturated or unsaturated monocarboxylic acid having 6 to 30 carbon atoms, a saturated or unsaturated dicarboxylic acid having 6 to 44 carbon atoms, a chloride thereof, and a mixture thereof as raw materials. Is done. Specific raw materials include stearic acid, isostearic acid, myristic acid, palmitic acid, pentadecanoic acid, decanoic acid, undecanoic acid, lauric acid, tridecanoic acid, nonadecanoic acid, arachidic acid, and behenic acid as saturated monocarboxylic acids. Selected from the group consisting of acid chlorides of these, and mixtures thereof, and oleic acid, linoleic acid, dodecenoic acid, tetradecenoic acid, hexadecenoic acid, octadecadienoic acid, octadecatrienoic acid, eicosenoic acid as unsaturated monocarboxylic acids, It is selected from the group consisting of eicosatetraenoic acid, docosenic acid and docosapentaenoic acid, and their acid chlorides, and mixtures thereof. The saturated or unsaturated dicarboxylic acid is specifically selected from the group consisting of sebacic acid, azelaic acid, 11,10-dodecanoic acid, Brazilic acid, docosannic acid, and acid chlorides thereof, and mixtures thereof.

  The 2-oxetanone compound can be used in the form of an emulsion by dispersing it using an emulsifier by a conventionally known method. Examples of the dispersant include cationic dispersants such as cationized starch and cationic polymer, and anionic dispersants having a sulfonic acid group or a sulfate group and salts thereof. One or more of these dispersants can be mixed and used. Moreover, there is no restriction | limiting in particular as the emulsification method, A conventionally well-known method can be applied, For example, emulsification methods, such as inversion emulsification, solvent emulsification, forced emulsification, etc. can be used.

There is no restriction | limiting in particular as said rosin type sizing agent, A conventionally well-known thing can be used. For example, as the rosin-based substance, (A) rosins and / or α, β-unsaturated carboxylic acid-modified rosins of rosins, (B) rosin esters obtained by esterification reaction of rosins and / or The α, β-unsaturated carboxylic acid-modified rosin esters of the rosin esters can be used in any combination. A rosin emulsion sizing agent obtained by emulsifying and dispersing these rosin substances in water by a conventionally known method can be used. A solution rosin can also be used.

As other sizing agents, known cationic sizing agents can be used. For example, as described in JP-A-2001-262495, styrene-acrylic acid ester copolymer 4 is used. Grades can be used. This is a cation monomer obtained by polymerizing a styrene monomer, an acrylate monomer containing a tertiary amino group such as dimethylaminoethyl methacrylate, and a monomer copolymerizable with these monomers. It is produced by a method in which a quaternizing agent such as epihalohydrin is reacted.

Examples of the styrenic monomer include styrene, α-methylstyrene, vinyltoluene, and divinylbenzene. These monomers can be used singly or in combination. Among these monomers, styrene is preferable because it is easily available and inexpensive.

Examples of the acrylate monomer containing a tertiary amino group include (monoalkyl or dialkyl) aminoalkyl (meth) acrylate, (monoalkyl or dialkyl) aminohydroxylalkyl (meth) acrylate, and the like. These 1 type (s) or 2 or more types can be used. Among these monomers, diethylaminoethyl methacrylate is preferable because it is easily available and inexpensive.

Examples of the monomer copolymerizable with these monomers used as necessary include hydrophobic monomers other than styrene monomers, and cationic monomers other than acrylic acid ester monomers containing tertiary amino groups. .

Examples of the hydrophobic monomer other than the styrene monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) ) Cyclic alkyl (meth) acrylates such as alkyl (meth) acrylates having 1 to 18 carbon atoms such as acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, maleic acid, and dialkyl diesters of fumaric acid , Vinyl esters such as vinyl acetate and vinyl propionate, N-alkyl (meth) acrylamides, and methyl vinyl ether, and one or more of these monomers can be used.

Examples of the cationic monomer other than the acrylate-based monomer containing a tertiary amino group include (monoalkyl or dialkyl) aminoalkyl (meth) acrylamide, vinylpyridine, vinylimidazole, and the like. 1 type (s) or 2 or more types can be used.

Examples of the quaternizing agent include methyl halide, ethyl chloride, benzyl chloride, epichlorohydrin, glycidyl trimethyl ammonium chloride, and organic halides such as 3-chloro-2-hydroxypropyltrimethyl ammonium chloride, dimethyl sulfate, and Examples thereof include dialkyl sulfuric acid such as diethyl sulfuric acid.

Polymerization of the cationic copolymer may be performed by, for example, mixing a mixture of the styrene monomer and an acrylate ester monomer containing a tertiary amino group and, if necessary, a mixture of other copolymerizable vinyl monomers. In a lower alcohol organic solvent such as methyl alcohol, ethyl alcohol or isopropyl alcohol or an oily organic solvent such as benzene, toluene or xylene, or in a mixture of these lower alcohol organic solvent and water, Can be polymerized in water at 60 to 120 ° C. for 1 to 10 hours using a radical polymerization catalyst.

<Primary and / or secondary amino group-containing polymer>
The primary and / or secondary amino group-containing polymer of the present invention may be a polymer having primary and / or secondary amino groups. Specific examples include cation-modified (meth) acrylamide polymers by Hoffman decomposition reaction, copolymers of diallylamine compounds and (meth) acrylamide, polyvinylamine, etc. Among these, cation modification by Hoffman decomposition reaction A (meth) acrylamide polymer and a copolymer of a diallylamine compound and (meth) acrylamide are preferred.

The cation equivalent of the primary and / or secondary amino group-containing polymer is preferably in the range of 1.0 meq / g to 8.0 meq / g. If the amount is less than 1.0 meq / g, the effect of sizing may be weak, and even if a primary and / or secondary amino group-containing polymer exceeding 8.0 meq / g is used, the effect of the present invention is limited. There is a case.

<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 (meth) acrylamide in the present invention include acrylonitrile, (meth) acrylic acid ester, vinyl acetate and the like.

  As the cationic monomer copolymerizable with (meth) acrylamide in the present invention, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide, allylamine, Vinyl monomers having amino groups such as diallylamine 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 And vinyl monomers having a quaternary ammonium group obtained by reaction with a quaternizing agent such as 2-hydroxypropyltrimethylammonium chloride.

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

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

In the present invention, the (meth) acrylamide polymer that is cationically modified by the Hofmann decomposition reaction may be copolymerized with one or more monomers copolymerizable with the (meth) acrylamide, preferably (meth) acrylamide is It is 60% or more of the total mol%.

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 of the present invention 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, a method of adjusting poly (meth) acrylamide by Hofmann decomposition reaction in the presence of choline chloride (see, for example, Patent Document 6), Hoffman decomposition In the reaction, 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 (for example, refer to Patent Document 7), an organic polyvalent amine is added as a stabilizer in a Hofmann decomposition reaction. A specific cation compound is added as a stabilizer in the Hoffmann decomposition reaction (for example, see Patent Document 8) How adjust it (e.g., Patent Document 9 reference) can be given.
JP-A-53-109545 Japanese Patent Publication No.58-8682 Japanese Patent Publication No. 60-17322 Japanese Examined Patent Publication No. 62-45884

<Copolymer of diallylamine compound and (meth) acrylamide>
A copolymer of a diallylamine compound and (meth) acrylamide is a polymer obtained by copolymerizing at least an inorganic or organic acid salt of a (meth) acrylamide compound and a diallylamine compound.

In the present invention,
(Meth) acrylamide is acrylamide or methacrylamide.

Examples of diallylamine compounds and inorganic or organic acid salts thereof include diallylamine, dimethallylamine, and inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid, or organic acid salts such as formic acid, acetic acid, and propionic acid. Can do. Of these, diallylamine salts are most preferably used.

In the copolymer of the diallylamine compound and (meth) acrylamide of the present invention, components other than the (meth) acrylamide and the diallylamine compound and the inorganic or organic acid salt thereof may be used as necessary. ) Vinyl monomers that can be copolymerized with acrylamide and the diallylamine compound and inorganic or organic acid salts thereof may be used, and any of nonionic, cationic, anionic, and crosslinkable monomers can be used.

Nonionic monomers include (meth) acrylic acid esters such as methyl acrylate, methyl methacrylate, ethyl acrylate and ethyl methacrylate, acrylonitrile, methacrylonitrile, styrene, hydroxyethyl acrylate, hydroxyethyl methacrylate, vinyl acetate, propion Examples include vinyl acid and methyl vinyl ether. These may be used alone or in combination of two or more.

Examples of the cationic vinyl monomer include dialkylaminoalkyl alcohols such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminopropyl (meth) acrylate, and (meth) acrylic acid. Tertiary alkyl groups such as dialkylaminoalkyl (meth) acrylates, dimethylaminopropyl (meth) acrylamide, and dialkylaminoalkyl (meth) acrylamides such as diethylaminopropyl (meth) acrylamide, secondary amino groups Primary amino group-containing vinyl monomers, salts of inorganic acids or organic acids such as hydrochloric acid, sulfuric acid, formic acid and acetic acid of the amino group-containing vinyl monomers, and tertiary amino group-containing vinyl monomers And alkyl halides such as methyl chloride and methyl bromide, aralkyl halides such as benzyl chloride and benzyl bromide, dimethyl sulfate, diethyl sulfate, epichlorohydrin, 3-chloro-2-hydroxypropyltrimethylammonium chloride, glycidyl trialkylammonium chloride, etc. Vinyl monomers containing a quaternary ammonium salt obtained by reaction with a quaternizing agent such as 2-hydroxy N, N, N, N ′, N′-pentamethyl-N ′-[3-{(1-oxo -2-propenyl) amino} propyl] -1,3-propanediaminium dichloride, diallyldimethylammonium chloride, vinyl pyridine, vinyl pyrrolidone, and the like, which may be used alone or in combination of two or more Together with It may be.

Examples of the anionic vinyl monomer include a carboxyl group-containing vinyl monomer, a sulfonic acid group-containing vinyl monomer, and a phosphonic acid group-containing vinyl monomer. Among these, a carboxyl group-containing vinyl monomer and a sulfonic acid group-containing vinyl monomer are preferable. Particularly, a combination of two or more kinds of carboxyl group-containing vinyl monomers, one or more kinds of carboxyl group-containing vinyl monomers, and one or more kinds of sulfonic acid group-containing vinyl monomers. A combination of monomers is preferred. Examples of the carboxyl group-containing vinyl monomer include unsaturated monocarboxylic acid, unsaturated dicarboxylic acid, unsaturated tricarboxylic acid, unsaturated tetracarboxylic acid, and salts thereof, and the sulfonic acid group-containing vinyl monomer. Unsaturated sulfonic acids and the like and salts thereof can be exemplified, and examples of the phosphonic acid group-containing vinyl monomer include unsaturated phosphonic acids and the like and salts thereof.

Examples of the unsaturated monocarboxylic acid include acrylic acid and methacrylic acid. Examples of the unsaturated monocarboxylic acid salt include alkali metal salts such as sodium salt and potassium salt of unsaturated carboxylic acid and ammonium. A salt etc. can be mentioned, These may be used individually by 1 type and may use 2 or more types together.

Specific examples of the unsaturated dicarboxylic acid include maleic acid, fumaric acid, itaconic acid, citraconic acid and the like. Specific examples of the salts of the unsaturated dicarboxylic acid include sodium dicarboxylic acid. Examples thereof include alkali metal salts such as salts and potassium salts, ammonium salts and the like, and these may be used alone or in combination of two or more.

Specific examples of the unsaturated tricarboxylic acid include aconitic acid, 3-butene-1,2,2,3-tricarboxylic acid, 4-pentene-1,2,4-tricarboxylic acid, and the like. Specific examples of the salt of tricarboxylic acid include, for example, alkali metal salts such as sodium salt and potassium salt of unsaturated tricarboxylic acid and ammonium salt, and these may be used alone. Two or more kinds may be used in combination.

Specific examples of the unsaturated tetracarboxylic acid include 1-pentene-1, 1,4,4-tetracarboxylic acid, 4-pentene-1,2,3,4-tetracarboxylic acid, and 3-hexene-1. , 1, 6, 6-tetracarboxylic acid and the like. Specific examples of the salts of the unsaturated tetracarboxylic acid include alkali metal salts such as sodium salt and potassium salt of unsaturated tetracarboxylic acid and ammonium. A salt etc. can be mentioned, These may be used individually by 1 type and may use 2 or more types together.

Specific examples of the unsaturated sulfonic acid include vinyl sulfonic acid, styrene sulfonic acid, (meth) allyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, and the like. Specific examples of the salts include alkali metal salts such as sodium salts and potassium salts of unsaturated sulfonic acids and ammonium salts, and these may be used alone or in combination of two or more. You may use together.

Specific examples of the unsaturated phosphonic acid include vinylphosphonic acid and α-phenylvinylphosphonic acid. Specific examples of the salts of the unsaturated phosphonic acid include sodium phosphonic acid. Examples thereof include alkali metal salts such as salts and potassium salts, and ammonium salts. These may be used alone or in combination of two or more.

Examples of the crosslinkable monomer include di (meth) acrylates such as ethylene glycol di (meth) acrylate and diethylene glycol di (meth) acrylate, bis (methylenebis (meth) acrylamide, and bis (N, N-bisacrylamideacetic acid). Bifunctional vinyl monomers such as (meth) acrylamides, divinyl adipate, diallyl malate, N-methylolacrylamide, diallyldimethylammonium, and glycidyl (meth) acrylate, triacryl formal, triallylamine, triallyl isocyanurate, and tri 4 such as trifunctional vinyl monomers such as allyl trimellitate, tetramethylolmethane tetraacrylate, tetraallyl pyromellilate, tetraallylamine salt, and tetraallyloxyethane Water-soluble aziridinyl compounds such as functional vinyl monomers, tetramethylolmethane-tri-β-aziridinylpropionate, and trimethylolpropane-tri-β-aziridinylpropionate, (poly) ethylene glycol diglycidyl ether, Water-soluble polyfunctional epoxy compounds such as (poly) glycerin diglycidyl ether, and 3- (meth) acryloxymethyltrimethoxysilane, 2- (meth) acrylamido-2-methylpropyltrimethoxysilane, vinyldimethylmethoxysilane , Vinyl trichlorosilane, vinyl triphenoxysilane, and silicon compounds such as 2- (meth) acrylamide-2-methylpropyltriacetoxysilane, and the like. These can be used alone, and two of them. Pair above Together it can also be used.

In the present invention, the preferred ratio of the inorganic or organic acid salt of (meth) acrylamide and diallylamine compound used in the production of a copolymer of a diallylamine compound and (meth) acrylamide is based on the total amount of the monomer (meth) Acrylamide is 40 to 99 mol%, more preferably 50 to 97 mol%, and the diallylamine compound and its inorganic or organic acid salt are 1 to 60 mol%, more preferably 3 to 50 mol%. In addition, other usable monomers can be used within a range that does not impair the effects of the present invention, preferably within a range of 40 mol% or less based on the total amount of the monomers, but the amount used is also somewhat due to its water solubility and ionicity. Be restricted. In the case of a nonionic monomer, it is preferably used within a range that does not impair the water solubility of the polymer to be produced. In the case of a cationic monomer, it is 40 mol% or less, more preferably 30 mol% or less based on the total amount of monomers. In the case of an anionic monomer, it is used in an amount less than that of the diallylamine compound. In addition, when the said (meth) acrylamide compound is less than 40 mol%, or when the said diallylamine compound is less than 1 mol%, the effect of this invention may not fully be exhibited, and other monomers which can be used are 40. The same applies when exceeding mol%.

The copolymer of the diallylamine compound and (meth) acrylamide used in the present invention can be produced by a known method, and the polymerization mode is not particularly limited, but in a water solvent or a mixed solvent of water and a water-soluble solvent. Of these, the polymerization reaction is preferably carried out in the presence of a polymerization initiator. If necessary, a known and commonly used molecular weight regulator such as isopropyl alcohol, allyl alcohol, sodium (meth) allyl sulfonate, sodium hypophosphite, polyethylene glycol, alkyl mercaptan, for example, methyl mercaptan can be used.

As the polymerization initiator, those usually used can be used. For example, persulfates such as ammonium persulfate and potassium persulfate, 2,2'-diamidino-2,2'-azopropane dihydrochloride, azo compounds such as azobisisobutyronitrile, di-t-butyl peroxide , Cumene hydroperoxide, peroxides such as hydrogen peroxide, and the like. A known redox initiator, for example, a combination of potassium persulfate and sodium bisulfite or a tertiary amine can also be used.

The polymerization is usually carried out at 10 to 100 ° C., preferably 40 to 80 ° C. for 1 to 20 hours. This polymerization reaction is possible even in the presence of oxygen, but generally it is preferably carried out in an atmosphere of an inert gas such as nitrogen gas.

The (meth) acrylamide compound and the diallylamine compound, and other monomers that can be used as required may start polymerization after all these components are charged together, or may be a part of certain components or The whole may be added continuously or divided after the start of polymerization of the other components to carry out the polymerization.

In the present invention, a copolymer of a diallylamine compound and (meth) acrylamide can be obtained as described above. The copolymer of the diallylamine compound and (meth) acrylamide preferably has a Brookfield viscosity of about 200 to 10,000 mPa · s at 25 ° C. in a 15 wt% aqueous solution.

<Coagulant>
Examples of the coagulant used in the present invention include organic coagulants and inorganic coagulants. Examples of the organic coagulant include cationic compounds obtained by polymerizing containing at least one or more types of cationic monomers, amine-epihalohydrin resins, polyethyleneimine, polyethyleneimine modified products, and polyvinylamine. .

Examples of the cationic monomer used in the cationic polymer used in the present invention include compounds represented by the following general formulas (4) to (6), diallylamines, and the like. It can also be used together.

（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。） General formula (4)

(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 (4) 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 Examples include dibromide.

（但し、式中、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。） General formula (5)

(In the formula, A represents oxygen or NH, n represents an integer of 2 to 4, R ⁷ represents H or a methyl group, and R ⁸ and R ⁹ represent the same or different lower alkyl groups having 1 to 3 carbon atoms.)

Specific cationic monomers of the general formula (5) include N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide and the like.

（但し、式中、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。） General formula (6)

(In the formula, 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, and R ¹³ is (Lower alkyl group or benzyl group, Z ⁻ represents an anionic group.)

    As a specific cationic monomer of the general formula (6), the cationic monomer represented by the general formula (5) is converted to an appropriate quaternizing agent such as an alkyl halide, a dialkyl carbonate, an alkyl tosylate, or an alkyl mesylate. 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 cationic polymer used for this invention, A conventionally well-known method is employable.

  Furthermore, as described above, the cationic monomer of the general formula (5) is not only subjected to the polymerization reaction after quaternization with the quaternizing agent, but also the cationic monomer belonging to the general formula (5). It can also be quaternized using the quaternizing agent during or after the polymerization of the body or the like. In this case, all may be quaternized, but some may be quaternized.

  The amine-epihalohydrin resin used in the present invention 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 , Diethanolamine, 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 amine epihalohydrin resin used for this invention, A conventionally well-known method is employable.

Examples of inorganic coagulants include polyaluminum compounds such as polyaluminum chloride, polyaluminum silicate sulfate, polyaluminum hydroxide, polyiron sulfate, and zirconium carbonate.

<Chemical addition location and amount>
In the present invention, when the primary and / or secondary amino group-containing polymer is added to the pulp slurry, the addition location is not particularly limited, but it is preferably added between the beating machine outlet and the inlet inlet in 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 primary and / or secondary amino group-containing polymer to the pulp solid content is 0.02 to 3% by weight, preferably 0.05 to 1% by weight. If the amount is less than 0.02% by weight, the size effect may be insufficient, and if the amount exceeds 3% by weight, the effect may reach its peak.

The addition rate of pulp solids to the sizing agent used in the surface layer is 0.01 to 2% by weight, preferably 0.03 to 1% by weight. If the amount is less than 0.01% by weight, the size effect may not be sufficiently exhibited, and if the amount exceeds 2% by weight, the effect may reach its peak.

When used in any of the other layers, the addition ratio of sizing agent to pulp solids is 0.01 to 1% by weight, preferably 0.03 to 0.5% by weight. If the amount is less than 0.01% by weight, the size effect may not be sufficiently exhibited. If the amount exceeds 1% by weight, the effect may reach its peak.

In the present invention, when the coagulant used for any other layer 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 inlet. . Further, it is not limited to one place, and it may be added in multiple places, or one or more coagulants may be used.

In the present invention, the addition ratio of the coagulant to the pulp solid used in any other layer 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, the cationicity in the papermaking system becomes excessive, and fixing of paper strength agents and the like may be reduced. .

<Aluminum compound>
Examples of the aluminum compound used in the present invention 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. Polyaluminum chloride is preferred. These aluminum compounds are used alone or in combination of two or more.

(1) 0.1 to 10% by weight, preferably 1 to 5% by weight, and (2) not used in any other layer, or 1% by weight, based on the solid content of the pulp slurry. It is preferable to use the following.

For pulp slurry, other additive chemicals such as cationic starch, amphoteric starch, dry paper strength agents such as (meth) acrylamide copolymers, wet strength materials such as polyamide polyamine epichlorohydrin resin, etc. It is possible to use a suitable combination of a retention agent or the like, or a filler such as calcium carbonate such as light calcium carbonate or heavy calcium carbonate, clay or titanium oxide.

In order to obtain a predetermined pH, it is possible to use a pH adjuster, for example, an alkaline substance such as sodium hydroxide or sodium carbonate, or an acidic substance such as sulfuric acid.

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.

Example 1
(A) 400 Canadian Standard Freeness self-manufactured corrugated paper is made into a slurry of 2.4%, and to this, 2.0% sulfuric acid band and 0.3% acrylamide-based paper strength agent for each solid content of pulp. DS4388 (manufactured by Seiko PMC) and sizing agent AL1300 (manufactured by Seiko PMC), which is a 0.2% rosin sizing agent, were sequentially added. The obtained pulp slurry was paper-made at a paper-making pH of 5.5 and using a TAPPI standard sheet machine round shape so as to have a basis weight of 30 g / m ² to obtain a wet paper A1.
(B) A self-made corrugated paper containing 370 Canadian Standard Freeness calcium carbonate is made into a slurry of 2.4%, and each of them is further treated with a primary amino group-containing polymer of 0.3% per pulp solid content. Paper strength agent DH4160 (manufactured by Hoshiman Decomposition Reaction) DH4160 (manufactured by Seiko PMC Co., Ltd.), AS1530 (Starlight PMC Co., Ltd.) 0.1% substituted cyclic dicarboxylic acid anhydride sizing agent Manufactured by emulsification with emulsifier SP1800 (manufactured by Seiko PMC Co., Ltd.) was sequentially added. The obtained pulp slurry was paper-made at a pH of 7.5 and using a TAPPI standard sheet machine round shape so that the basis weight was 90 g / m ² to obtain wet paper B1.
(C) The wet paper A1 and the wet paper B1 were bonded together, pressed at 410 kPa for 120 seconds, and then dried at 110 ° C. for 120 seconds using a drum dryer to obtain a laminated paper C1.

Example 2
(A) Wet paper A1 was obtained in the same manner as in Example 1 (a).
(B) The same procedure as in Example 1 (b) except that the coagulant AC7300 (manufactured by Seiko PMC), which is 0.1% amine-epihalohydrin resin (dimethylamine epichlorohydrin), is added first. Thus, wet paper B2 was obtained.
(C) The wet paper A1 and the wet paper B2 were combined in the same manner as in Example 1 (c) to obtain a laminated paper C2.

Example 3
(A) Wet paper A1 was obtained in the same manner as in Example 1 (a).
(B) The same procedure as in Example 1 (b) except that a coagulant AC7304 (manufactured by Seiko PMC Co., Ltd.), which is a 0.1% cationic polymer (polydiallyldimethylammonium chloride), is first added. Wet paper B3 was obtained.
(C) The wet paper A1 and the wet paper B3 were combined in the same manner as in Example 1 (c) to obtain a laminated paper C3.

Example 4
(A) Wet paper A1 was obtained in the same manner as in Example 1 (a).
(B) Instead of the paper strength agent DH4160 (manufactured by Seiko PMC Co., Ltd.), which is a primary amino group-containing polymer (cation-modified acrylamide polymer by Hofmann decomposition reaction), secondary amino group-containing polymers (diallylamine and (meta) ) Copolymer with acrylamide) FX7200 (manufactured by Seiko PMC Co., Ltd.) was used in the same manner as Example 1 (b) except that 0.3% was used to obtain wet paper B4.
(C) The wet paper A1 and the wet paper B4 were combined in the same manner as in Example 1 (c) to obtain a laminated paper C4.

Example 5
(A) Wet paper A1 was obtained in the same manner as in Example 1 (a).
(B) Example except that 0.1% of sizing agent AD1604 (manufactured by Seiko PMC Co., Ltd.), which is a 2-oxetanone sizing agent, was used in place of the sizing agent as a substituted cyclic dicarboxylic acid anhydride sizing agent. Wet paper B5 was obtained in the same manner as 1 (b).
(C) The wet paper A1 and the wet paper B5 were used in the same manner as in Example 1 (c) to obtain a laminated paper C5.

Example 6
(A) Wet paper A1 was obtained in the same manner as in Example 1 (a).
(B) 370 Canadian Standard Freeness calcium carbonate containing self-made corrugated paper is made into a slurry of 2.4%, to which 0.8% sulfate band, 0.3% % Of primary amino group-containing polymer (cation modified acrylamide polymer by Hoffman decomposition reaction) DH4160 (manufactured by Seiko PMC Co., Ltd.), 0.3% neutral rosin sizing agent CC1404 ( Seiko PMC Co., Ltd.) was sequentially added. The obtained pulp slurry was paper-made at a pH of 7.0 and using a TAPPI standard sheet machine round shape so as to have a basis weight of 90 g / m ² , thereby obtaining wet paper B6.
(C) The wet paper A1 and the wet paper B6 were used in the same manner as in Example 1 (c) to obtain a laminated paper C6.

Example 7
(A) Wet paper A1 was obtained in the same manner as in Example 1 (a).
(B) Substituting the neutral rosin sizing agent CC1404 (manufactured by Seiko PMC) with AS1530 (manufactured by Seiko PMC) as an emulsifier SP1800 (Seiko PMC) A wet paper web B7 was obtained in the same manner as in Example 6 (b) except that 0.1% of the product emulsified in (made by Co., Ltd.) was used.
(C) The wet paper A1 and the wet paper B7 were combined in the same manner as in Example 1 (c) to obtain a laminated paper C7.

Example 8
(A) Instead of AL1300 (manufactured by Seiko PMC Co., Ltd.) as a rosin sizing agent, AS1530 (manufactured by Seiko PMC Co., Ltd.) as a substituted cyclic dicarboxylic acid anhydride sizing agent is used as an emulsifier SP1800 (Seiko PMC) Wet paper A2 was obtained in the same manner as in Example 1 (a) except that 0.1% of the product emulsified in (made by Co., Ltd.) was used.
(B) Wet paper B1 was obtained in the same manner as described in Example 1 (b).
(C) The wet paper A2 and the wet paper B1 were used in the same manner as in Example 1 (c) to obtain a laminated paper C8.

Example 9
(A) Example 8 (a ) To obtain wet paper A3.
(B) Wet paper B1 was obtained in the same manner as described in Example 1 (b).
(C) The wet paper A3 and the wet paper B1 were combined in the same manner as in Example 1 (c) to obtain a laminated paper C9.

Comparative Example 1
(A) 400 Canadian Standard Freeness self-made corrugated cardboard was made into a slurry of 2.4%, and each of them was further treated with 0.3% primary amino group-containing polymer (cation modification by Hofmann decomposition reaction) per solids of pulp. Acrylamide polymer) paper strength agent DH4160, 0.1% substituted cyclic dicarboxylic acid anhydride sizing agent AS1530 (manufactured by Seiko PMC Co., Ltd.) is emulsified with emulsifier SP1800 (manufactured by Seiko PMC Co., Ltd.). Were added sequentially. The obtained pulp slurry was paper-made at a pH of 7.5 and using a TAPPI standard sheet machine round shape so that the basis weight was 30 g / m ² to obtain wet paper A4.
(B) Wet paper B1 was obtained in the same manner as described in Example 1 (b).
(C) The wet paper A4 and the wet paper B1 were used in Example 1 (c) to obtain a laminated paper D1.

Comparative Example 2
(A) Wet paper A3 was obtained in the same manner as described in Example 9 (a).
(B) 370 Canadian Standard Freeness calcium carbonate containing self-made corrugated paper is made into a slurry of 2.4%, and this is added to AS1530, a 0.1% substituted cyclic dicarboxylic anhydride sizing agent (Starlight) PMC Co., Ltd.) emulsified with emulsifier SP1800 (Seiko PMC Co., Ltd.) was added. The obtained pulp slurry was paper-made at a pH of 7.5 and using a TAPPI standard sheet machine round shape so that the basis weight was 90 g / m ² to obtain wet paper B8.
(C) The wet paper A3 and the wet paper B8 were used in Example 1 (c) to obtain a laminated paper D2.

(Evaluation of paper quality)
The laminated papers C1 to C9 and D1 to D2 obtained by the above examples and comparative examples were conditioned for 24 hours in a constant temperature and humidity chamber at a temperature of 23 ° C. and a humidity of 50%, and then according to the following measurement method. Various paper quality was evaluated. The obtained results are shown in Table 1.
The measurement was performed with the wet paper webs A1 to A3 side of the laminated paper as the front side.
Interlayer strength: Conforms to JAPAN TAPPI No. 19-1 Cobb water absorption: Conforms to JIS P-8140

About the comparative example, since the interlayer intensity | strength of the laminated paper was largely inferior compared with the Example, size measurement was not implemented.

(Measurement of water repellency)
For the laminated papers C1 to C9 and D1 to D2, the side of A1 to A3 is the front side, and the water repellent WR3922 (manufactured by Seiko PMC Co., Ltd.) is No. on the front side. After applying 0.3 g / m ^{2 with a} 3 bar coater, drying at 70 ° C. for 20 seconds to obtain a water-repellent combined paper, and measuring the water repellency of the combined paper before heat treatment I did it.
Separately, a laminated paper coated with a water repellent was placed in an electric dryer set at 150 ° C., and then heat treated for 10 minutes and taken out. Thereafter, the water repellency was measured after conditioning for 24 hours at a temperature of 23 ° C. and a humidity of 55%. The water repellent finish suitability was compared by comparing the water repellency of the coated paper before and after heat treatment. In addition, it means that a base paper having a small decrease in water repellency before and after the heat treatment is a base paper having a good suitability for water repellent processing.
Water repellency: according to JAPAN TAPPI No.68

(Measurement of turbidity of pulp slurry filtrate)
The turbidity was measured by measuring the pulp slurry immediately before the papermaking of the wet papers B1 to 8 in each example as NO. The filtrate obtained by suction filtration with 5A filter paper was used as a sample using a Hack Turbidimeter 2100P. The obtained results are shown in Table 2. In addition, it is considered that the smaller the value of the turbidity, the smaller the colloidal impurities in the filtrate, and the lower the machine contamination.

"-" In the table indicates that measurement was not performed.
In Examples 1 to 8 (acid papermaking-neutral papermaking), the interlaminar strength was higher than that of Comparative Example 1 (neutral paper-neutral papermaking) and water repellent processing suitability was excellent.

"-" In the table indicates that measurement was not performed.
In Example 9, the interlayer strength was higher than in Comparative Example 2, and the suitability for water repellent processing was excellent.
It has been suggested that the primary and / or / secondary amino group-containing polymer contributes to improvement in interlayer strength and suitability for water repellent processing.

  In the comparison of Examples 1-8, the use of a coagulant in the back layer improved the size of the front layer of the laminated paper and resulted in a decrease in the turbidity of the back layer pulp slurry. It was suggested that the coagulant is effective for size effect and machine stain prevention.

Claims (7)

(1) The surface layer is made in the presence of a sizing agent at a pH of 4 or more and less than 6.5,
(2) Any other layer has a pH of 6.5 to 8.5 in the presence of a primary and / or secondary amino group-containing polymer, or a primary and / or secondary amino group-containing polymer and a sizing agent. A method for producing a laminated paperboard, characterized by papermaking. (3) The surface layer is made in the presence of a sizing agent at a pH of 4 or more and less than 6.5,
(4) Any other layer has a pH of 6. in the presence of a primary and / or secondary amino group-containing polymer and a coagulant, or a primary and / or secondary amino group-containing polymer, a coagulant, and a sizing agent. 5. A method for producing a laminated paperboard, wherein papermaking is performed at 5 to 8.5. The sizing agent used in any other layer is at least one selected from a rosin sizing agent, a substituted cyclic dicarboxylic anhydride sizing agent, and a 2-oxetanone sizing agent. 2. A method for producing a paperboard according to 2. The method for producing a paperboard according to any one of claims 1 to 3, wherein the primary and / or secondary amino group-containing polymer is a cation-modified (meth) acrylamide polymer by Hofmann decomposition reaction. The method for producing paperboard according to any one of claims 1 to 3, wherein the primary and / or secondary amino group-containing polymer is a copolymer of a diallylamine compound and (meth) acrylamide. The aluminum compound is used in the surface layer of 0.1 to 10% by weight with respect to the solid content of the pulp slurry, and (6) not used in the other layers or 1% by weight or less. 6. The method for producing a paperboard according to any one of 5 above. The paperboard production method according to any one of claims 1 to 6, wherein the paperboard is a water-repellent liner base paper.