JP2005232616A - Interlaminar strength improver and method for interlaminar strength improvement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an interlayer strength improver comprising a dispersion of an ionic polymer fine particle in an aqueous solution of a salt, which prevents release in the vicinity of an interlayer liable to occur due to low strength in the inside of a paper layer, by fixing itself to the surface of a paper layer in the dispersion of the ionic polymer fine particle of the interlayer strength improver for spray and by including a component that develops adhesive strength between a certain layer and another layer and a component that is selectively dissolved in a dryer part, permeates and improves strength in the inside of the paper layer. <P>SOLUTION: In a method for producing combined paper of two or more layers, comprising a process for combining wet paper layers after paper layer formation, pressing and drying, the interlayer strength improver composed of the dispersion of the ionic polymer fine particle is obtained by subjecting a mixture of a water-soluble ionic monomer and, if necessary, a water-soluble nonionic monomer copolymerizable with the monomer to dispersion polymerization with stirring at a temperature lower than gelation temperature in an aqueous solution of a salt in the presence of 1-50 wt.% based on the monomer mixture of at least one kind of a polysaccharide in a dispersed state in the aqueous solution of the salt without causing gelation and a polymer dispersant soluble in the aqueous solution of the salt. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to an interlaminar strength improver and an interlaminar strength improving method. Specifically, the wet paper layer after the paper layer formation is combined, pressed, and further dried. In order to improve the interlaminar strength used in the production of paper, in a salt solution, a mixture of an ionic water-soluble monomer and, if necessary, a nonionic monomer copolymerizable therewith, at least one polysaccharide is added. In the presence of 1 to 50% by weight with respect to the monomer mixture in the state of being dispersed without being gelatinized in the aqueous salt solution, a soluble polymer dispersant is allowed to coexist in the aqueous salt solution, with stirring, The present invention relates to an interlayer strength improver comprising a dispersion of ionic polymer fine particles obtained by dispersion polymerization, and also relates to a method for improving interlayer strength using the same.

Conventional paper interlayer strength improvers include raw starch or phosphate starch, and a method of spraying the slurry is generally used. Patent Document 1 proposes a method of spraying a dispersion liquid containing polymer fine particles containing (meth) acrylic acid. Patent Document 2 proposes a method of spraying a dispersion liquid containing inorganic particle-containing ionic polymer fine particles of 100 μm or less in order to improve fixability. However, these interlaminar strength improvers fix the components on the pulp surface and remain between the layers, but some of them flow out together with water in the suction part, so that the interlaminar strength is improved to a certain level or more. Things were difficult.

JP-A-10-331100 Japanese Patent Laid-Open No. 2003-155561

An object of the present invention is to contain a component that expresses the adhesive force between the layer fixed on the paper layer surface and the other layer in the ionic polymer fine particle dispersion of the interlayer strength improver for spraying, and is selected. In addition, by adding a component that dissolves and permeates in the dryer part and improves the strength inside the paper layer, the strength inside the paper layer is low, so that the ionic weight in the salt solution can be prevented from being peeled off near the layer, which is likely to occur. The purpose is to develop an interlaminar strength improver comprising a dispersion of coalesced fine particles. As a result, the same interlayer strength can be expressed with an addition amount of one fifth to one half of starch.

As a result of intensive studies, the present inventors have reached the following invention. The invention of claim 1 of the present invention is a method for producing two or more layers of combined paper, comprising a step of pressing the wet paper layer after the paper layer formation and then pressing and then drying, in a salt aqueous solution, A water-soluble ionic monomer is essential, and if necessary, a water-soluble nonionic monomer copolymerizable therewith is added, and at least one polysaccharide is dispersed in the aqueous salt solution without gelatinization. In the state, in the presence of 1 to 50% by weight with respect to the monomer (mixture), a soluble polymer dispersant is allowed to coexist in the aqueous salt solution, and the dispersion polymerization is performed at a temperature below the gelatinization temperature of the polysaccharide with stirring. It is an interlayer strength improver comprising a dispersion of ionic polymer fine particles obtained as described above. As a result, it is possible to produce a laminated paper at a lower cost than conventional synthetic interlayer strength improvers.

一般式（１）
ここでＲ１は水素、メチル基またはカルボキシメチル基、ＡはＳＯ３、Ｃ６Ｈ４ＳＯ３、ＣＯＮＨＣ（ＣＨ３）２ＣＨ２ＳＯ３、Ｃ６Ｈ４ＣＯＯあるいはＣＯＯ、Ｒ２は水素またはＣＯＯＹ２、Ｙ１あるいはＹ２は水素または陽イオンをそれぞれ表わす The invention of claim 2 is characterized in that the ionic polymer is composed of 2 to 100 mol% of a monomer of the following general formula (1) and 0 to 98 mol% of a copolymerizable nonionic monomer. The interlayer strength improver according to claim 1.

General formula (1)
Where R1 is hydrogen, methyl group or carboxymethyl group, A is SO3, C6H4SO3, CONHC (CH3) 2CH2SO3, C6H4COO or COO, R2 is hydrogen or COOY2, Y1 or Y2 is hydrogen or cation, respectively

一般式（２）
ここでＲ３は水素又はメチル基、Ｒ４、Ｒ５は炭素数１〜３のアルキルあるいはアルコキシル基、Ｒ６は水素、炭素数１〜３のアルキル基、アルコキシル基あるいはベンジル基であり、同種でも異種でも良い、Ａは酸素またはＮＨ、Ｂは炭素数２〜４のアルキレン基またはアルコキシレン基を表わす、Ｘ１は陰イオンをそれぞれ表わす。

一般式（３）
ここでＲ７は水素又はメチル基、Ｒ８、Ｒ９は炭素数１〜３のアルキル基、アルコキシ基あるいはベンジル基、Ｘ３は陰イオンをそれぞれ表わす。 The invention of claim 3 is characterized in that the ionic polymer is 2 to 70 mol% of the monomer of the following general formula (2) and / or (3), and 0 to 70 mol of the monomer of the general formula (1). The interlayer strength improver according to claim 1, comprising 10% to 98% by mole of copolymerizable nonionic monomer.

General formula (2)
Here, R3 is hydrogen or a methyl group, R4 and R5 are alkyl or alkoxyl groups having 1 to 3 carbon atoms, and R6 is hydrogen, an alkyl group having 1 to 3 carbon atoms, an alkoxyl group or a benzyl group, which may be the same or different. , A represents oxygen or NH, B represents an alkylene group or alkoxylene group having 2 to 4 carbon atoms, and X1 represents an anion.

General formula (3)
Here, R7 represents hydrogen or a methyl group, R8 and R9 each represents an alkyl group having 1 to 3 carbon atoms, an alkoxy group or a benzyl group, and X3 represents an anion.

In the invention of claim 4, the monomer of the general formula (1) is at least one selected from (meth) acrylic acid, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid or salts thereof. The interlayer strength improver according to any one of claims 1 to 3.

The invention according to claim 5 is the interlayer strength improver according to any one of claims 1 to 3, characterized in that the mixture of monomers contains a cross-linkable vinyl monomer at a maximum of 0.5% by weight.

The invention according to claim 6 is the interlayer strength improver according to any one of claims 1 to 3, wherein the polymer dispersant soluble in the aqueous salt solution is an ionic polymer.

The invention according to claim 7 is characterized in that the polysaccharide has at least one type of 5 to 25% by weight with respect to the monomer mixture in order to develop the same interlayer strength with an addition amount of 1/10 or less of starch having high cost merit. The interlayer strength improver according to claim 1, comprising:

The invention according to claim 8 is the interlayer strength improver according to claim 1 or 7, wherein the gelatinization temperature of the polysaccharide is 40 to 100 ° C.

The invention of claim 9 is a method for producing a two or more layered laminated paper comprising a step of pressing a wet paper layer after the paper layer is formed and then pressing and then drying the paper layer. An ionic polymer as described in 1) is used as an interlayer strength improver.

The interlaminar strength improver for spraying of the present invention comprises a dispersion of ionic polymer fine particles in an aqueous salt solution, and expresses the adhesive force between the layer fixed on the paper layer surface and the other layer in the dispersion. In addition, it contains a polysaccharide-acrylamide surface grafting component that selectively dissolves and permeates in the dryer part and improves the internal strength of the paper layer. Can be prevented from peeling. As a result, the same interlaminar strength is exhibited with an addition amount of one-fifth to one-twentieth of starch, and a laminated paper can be produced at a lower cost than in the past.

The interlayer strength improver of the present invention will be specifically described below. The ionic water-soluble polymer dispersion of the present invention is prepared by preparing an aqueous solution of a polyvalent anion salt such as ammonium sulfate, and when synthesizing an anionic polymer, an ungelatinized polysaccharide and a water-soluble anionic Monomers, water-soluble nonionic monomers as needed, and when synthesizing cationic or amphoteric polymers, ungelatinized polysaccharides and water-soluble cationic monomers, water-soluble nonionics A water-soluble anionic monomer if necessary, and a polymer dispersant soluble in the salt aqueous solution as a dispersant in the presence of the monomer, and dispersion polymerization is conducted under stirring. be able to.

As the polysaccharide used in the present invention, various known ones can be used, for example, corn, potato, tapioca, wheat, rice, sago palm, various starches obtained from waxy maize, celluloses, cationization Starch derivatives such as starch, oxidized starch, phosphate-modified starch, carboxymethylated starch, hydroxyethylated starch, carbamylethylated starch, dialdehyde-modified starch, acetic acid-modified starch, etc. Although chitosan etc. are mention | raise | lifted, that whose internal gelatinization temperature is 40-100 degreeC is used, Preferably the thing of 45-80 degreeC is used.

The addition ratio of the polysaccharide to the monomer (mixture) used in the present invention is 1 to 50% by weight, preferably 5 to 25% by weight. If it is less than 1% by weight, it can be dissolved and permeated selectively in the dryer part, and the component that improves the strength inside the paper layer cannot be contained in the dispersion in the required amount. It cannot prevent peeling in the vicinity. On the other hand, when the amount is more than 50% by weight, the ratio of the component grafted with the monomer on the polysaccharide is reduced, so that the number of simple polysaccharide particles is increased and the above effect is hardly exhibited.

Next, the dispersant will be described. As the polymer dispersant, either a nonionic or ionic polymer can be used, but an ionic polymer is more preferable, and if a cationic or amphoteric polymer is synthesized, a cationic is more preferable, If an anionic polymer is synthesized, anionic property is more preferable. Examples of anionic polymers are (co) polymers of anionic monomers such as (meth) acrylic acid, maleic acid, itaconic acid, acrylamide 2-methylpropane sulfonic acid styrene sulfonic acid or salts thereof. . Furthermore, acrylamide, N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, N, N-dimethylacrylamide, acrylonitrile, diacetone acrylamide, 2-hydroxyethyl (meth) acrylate, which are nonionic monomers Copolymers with these can also be used. Other examples include anion-modified polyvinyl alcohol, styrene / maleic anhydride copolymer, butene / maleic anhydride copolymer, or partially amidated products thereof. The most preferred ionic polymer is 2-acrylamido 2-methylpropanesulfonic acid polymer.

Cationic polymers include (meth) acrylic cationic monomers such as inorganic acid and organic acid salts such as dimethylaminoethyl (meth) acrylate and dimethylaminopropyl (meth) acrylamide, methyl chloride, It is a copolymer of quaternary ammonium salt and acrylamide by benzyl chloride. For example, as the cationic monomer, (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acryloyloxy 2-hydroxypropyltrimethylammonium chloride, (meth) acryloylaminopropyltrimethylammonium chloride, (meth) acryloyloxy Ethyldimethylbenzylammonium chloride, (meth) acryloyloxy 2-hydroxypropyldimethylbenzylammonium chloride, (meth) acryloylaminopropyldimethylbenzylammonium chloride, and the like. These monomer polymers or copolymers, or A copolymer with a nonionic monomer may be used. Also, diallylamine-based (co) polymers such as dimethyldiallylammonium chloride polymer can be used.

Examples of nonionic polymers include (co) polymers of the above nonionic monomers, polyvinyl alcohols, styrene / maleic anhydride copolymers and butene / maleic anhydride copolymers, each of which is a complete amide. Such as a monster.

The molecular weight of the ionic polymer is 5,000 to 3 million, preferably 50,000 to 1.5 million. The molecular weight of the nonionic polymer is 1,000 to 1,000,000, preferably 1,000 to 500,000. The addition amount of these polymer dispersants with respect to the monomer is 1/100 to 30/100, preferably 5/100 to 20/100.

The temperature at the time of superposition | polymerization is 5-75 degreeC, Preferably it is 15-45 degreeC. Moreover, it superposes | polymerizes below the gelatinization temperature of the polysaccharide to be used. When the temperature is higher than 75 ° C., it is difficult to control the polymerization, and a rapid temperature rise or agglomeration of the polymerization solution occurs, so that a stable dispersion is not generated.

For the initiation of polymerization, a radical polymerization initiator is used. These initiators may be either oil-soluble or water-soluble, and can be polymerized by any of azo, peroxide, and redox systems. Examples of oil-soluble azo initiators are 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexanecarbonitrile), 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2-methylpropionate), 4,4-azobis (4-methoxy-2,4dimethyl) valeronitrile and the like are mentioned and dissolved in a water-miscible solvent and added.

Examples of water-soluble azo initiators include 2,2′-azobis (amidinopropane) dichloride, 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] And dihydrochloride, 4,4′-azobis (4-cyanovaleric acid), and the like. Examples of redox systems include a combination of ammonium peroxodisulfate and sodium sulfite, sodium hydrogen sulfite, trimethylamine, tetramethylethylenediamine, and the like. Further examples of peroxides include ammonium or potassium peroxodisulfate, hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, t-butylperoxy 2-ethylhexanoate, and the like. I can give you. Most preferred among these initiators are 2,2′-azobis (amidinopropane) dihydrochloride, 2,2′-azobis [2- (5-methyl-2-imidazoline), which is a water-soluble azo initiator. -2-yl) propane] dihydrochloride.

The water-soluble anionic monomer used when polymerizing the anionic polymer may be a sulfonic acid group-containing monomer, but is preferably a carboxyl group-containing monomer or a single monomer mainly composed of a carboxyl group-containing monomer. A monomer mixture is suitable. Examples of the carboxyl group-containing monomer are methacrylic acid, acrylic acid, itaconic acid, maleic acid or p-carboxystyrene. Further, the anionic polymer may be a copolymer with another nonionic monomer. For example, (meth) acrylamide, N, N-dimethylacrylamide, vinyl acetate, acrylonitrile, methyl acrylate, 2-hydroxyethyl (meth) acrylate, diacetone acrylamide, N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide And acryloylmorpholine, which is a copolymer of one or more selected from these water-soluble anionic monomers and one or more selected from nonionic monomers. The most preferred combination is acrylic acid and chloramide.

The copolymerization molar ratio of the water-soluble anionic monomer is 2 to 100 mol%, preferably 5 to 80 mol%. Furthermore, the copolymerization mol% of the water-soluble nonionic monomer that can be copolymerized is 0 to 98 mol%, preferably 20 to 95 mol%.

Next, the cationic or amphoteric polymer will be described. The water-soluble cationic monomer used is a (meth) acrylic cationic monomer such as dimethylaminoethyl (meth) acrylate or dimethylaminopropyl (meth) acrylamide. Or a quaternary ammonium salt with methyl chloride or benzyl chloride, for example, (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acryloyloxy 2-hydroxypropyltrimethylammonium chloride, (meth) acryloylaminopropyltrimethylammonium chloride (Meth) acryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloyloxy 2-hydroxypropyldimethylbenzylammonium chloride, (meth) acryloylaminopropyldimethylbenzylammonium chloride, and the like. Also, diallylamine monomers such as dimethyldiallylammonium chloride can be used.

As the water-soluble anionic monomer or water-soluble nonionic monomer, the same monomer as that used in the synthesis of the anionic polymer is used. Moreover, the dispersing agent used at the time of polymerization uses the above-mentioned cationic polymer, and the addition amount is the same as that at the time of anionic polymer synthesis. The salts constituting the aqueous salt solution are the same as in the synthesis of the anionic polymer.

In the production of the cationic polymer dispersion, the molar ratio of the cationic monomer is 2 to 70 mol%, preferably 5 to 50 mol%, and more preferably 5 to 30 mol%. A nonionic monomer is 30-98 mol%, Preferably it is 50-95 mol%, More preferably, it is 70-95 mol%. In the case of producing an amphoteric polymer dispersion, the amount is 2 to 70 mol%, preferably 5 to 50 mol%, of a water-soluble cationic monomer. Moreover, a water-soluble anionic monomer is 2-70 mol%, Preferably it is 5-50 mol%. The water-soluble nonionic monomer is 0 to 96 mol%, preferably 0 to 90 mol%. The most preferred water-soluble cationic monomers are dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, acryloyloxyethyltrimethylammonium chloride, and methacryloyloxyethyltrimethylammonium chloride, and the water-soluble anionic monomer is ( The meth) acrylic acid, the water-soluble nonionic monomer is acrylamide.

In the present invention, a monomer having a plurality of vinyl groups can be appropriately coexisted to form a crosslinked or branched polymer, and an interlayer strength improver suitable for various purposes can be synthesized. Examples of such polyfunctional monomers having a plurality of vinyl groups include methylenebisacrylamide, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and the like. Thermally crosslinkable monomers such as N, N-dimethylacrylamide or N, N-diethylacrylamide can also be used.

Salts used to form an aqueous salt solution include salts of alkali metal ions such as sodium and potassium, ammonium ions, halide ions, sulfate ions, nitrate ions, phosphate ions, etc. The salt of is more preferable. Particularly preferred are divalent anion salts such as ammonium sulfate, sodium sulfate and aluminum sulfate. The salt concentration of these salts can be used from 7% by weight to a saturated concentration.

The interlayer strength improver for spraying of the present invention is polymerized in a monomer concentration range of about 15 to 40% by weight. If it is less than 15% by weight, the freight cost becomes too expensive, and if it exceeds 40% by weight, the fluidity of the product is insufficient and handling becomes difficult. When spraying and applying the ionic polymer dispersion of the present invention, it is sprayed and diluted to a desired concentration, but the dilution factor can be freely selected. In general, conventional starch is diluted and dispersed at a concentration of about 0.5 to 5% by weight, and sprayed, whereas the ionic polymer dispersion of the present invention is about 0.01 to 5% by weight. A prescription by spraying at a concentration is applicable. When it is desired to spray and apply more polymer as a paper quality improver, spray coating is possible even at a concentration of about 0.5 to 5% by mass.

As the paper to which the interlaminar strength improver of the present invention can be applied, there is a paperboard such as a core base paper, a white board, a liner or a card base paper. The papermaking pH is about 4.0 or more and 9.0 or less. In general, the pH of papermaking is less when it is less than 4.0 even in acidic papermaking, and when papermaking is carried out at less than 4.0, the paper is adversely affected. Further, when the papermaking pH exceeds 9.0, the solubility of the polymer fine particles is gradually promoted, and the polymer fine particles staying on the surface of the wet paper are dissolved before being heated by the dryer. When dehydrated, it flows out with water or penetrates into the wet paper layer, which is not preferable because the adhesion effect between the layers decreases.

Synthesis Example 1 Deionized water: 109.2 g, 60% acrylic acid: 22.7 g, 50% acrylamide: 80 in a four-necked 500 ml separable flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube 0.7 g, ammonium sulfate 64.0 g, phosphate esterified starch powder: 5.4 g (10% by weight of monomer), and 15% by weight aqueous solution of acrylamide 2-methylpropanesulfonic acid sodium salt polymer (molecular weight: about 300,000) ) 18.0 g (5% by weight of monomer) was added. Thereafter, nitrogen is introduced from the nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ° C. using a constant temperature water bath. Thirty minutes after the introduction of nitrogen, 0.275% by weight of an aqueous solution of 0.2% by weight ammonium peroxodisulfate and 0.2% by weight aqueous solution of ammonium hydrogensulfite was added in this order, respectively, to initiate polymerization. 2 hours after the addition of the initiator, the viscosity of the reaction liquid slightly increased but did not increase any more. After 6 hours from the start of polymerization, the same amount of the initiator was added, and the polymerization was continued for another 15 hours. finished. Let this prototype be prototype-1. The molar ratio of the acrylic acid / acrylamide in the trial production-1 was 25/75, and the viscosity was 470 mPa · s. The composition is shown in Table 1, and the polymerization results are shown in Table 2.

(Synthesis Example 2) Deionized water: 118.6 g, 60% acrylic acid: 45.3 g, 50% acrylamide: 53 in a 4-neck 500 ml separable flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube .6 g, ammonium sulfate 59.1 g, phosphate esterified starch powder: 5.4 g (10% by weight of monomer), and 15% by weight aqueous solution of acrylamide 2-methylpropanesulfonic acid sodium salt polymer (molecular weight: about 300,000) ) 18.0 g (5% by weight of monomer) was added. Thereafter, nitrogen is introduced from the nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ° C. using a constant temperature water bath. Thirty minutes after the introduction of nitrogen, 0.275% by weight of an aqueous solution of 0.2% by weight ammonium peroxodisulfate and 0.2% by weight aqueous solution of ammonium hydrogensulfite was added in this order, respectively, to initiate polymerization. 2 hours after the addition of the initiator, the viscosity of the reaction liquid slightly increased but did not increase any more. After 6 hours from the start of polymerization, the same amount of the initiator was added, and the polymerization was continued for another 15 hours. finished. Let this prototype be prototype-2. The molar ratio of acrylic acid / acrylamide in this trial production-2 was 50/50, and the viscosity was 810 mPa · s. The composition is shown in Table 1, and the polymerization results are shown in Table 2.

(Synthesis Example 3) Deionized water: 122.1 g, 60% acrylic acid: 39.2 g, itaconic acid powder: 4 in a four-necked 500 ml separable flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube 0.72 g, 50% acrylamide: 51.5 g, ammonium sulfate 59.1 g, phosphate esterified starch powder: 5.4 g (10% by weight monomer) 1% methylenebisacrylamide: 0.27 g, and 15% by weight aqueous solution Acrylamide 2-methylpropanesulfonic acid sodium salt polymer (molecular weight: about 300,000) 18.0 g (5% by weight of monomer) was added. Thereafter, nitrogen is introduced from the nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ° C. using a constant temperature water bath. Thirty minutes after the introduction of nitrogen, 0.275% by weight of an aqueous solution of 0.2% by weight ammonium peroxodisulfate and 0.2% by weight aqueous solution of ammonium hydrogensulfite was added in this order, respectively, to initiate polymerization. 2 hours after the addition of the initiator, the viscosity of the reaction liquid slightly increased but did not increase any more. After 6 hours from the start of polymerization, the same amount of the initiator was added, and the polymerization was continued for another 15 hours. finished. Let this prototype be prototype-3. In the trial production-3, the molar ratio of acrylic acid / itaconic acid / acrylamide was 45/5/50, and the viscosity was 900 mPa · s. The composition is shown in Table 1, and the polymerization results are shown in Table 2.

(Synthesis Example 4) Deionized water: 111.5 g, 60% acrylic acid: 36.8 g, 50% acrylamide 2-into a four-necked 500 ml separable flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube Methylpropanesulfonic acid: 15.6 g, 50% acrylamide: 48.3 g, ammonium sulfate 59.1 g, phosphate esterified starch powder: 10.8 g (20% by weight of monomer), and 15% by weight aqueous solution of acrylamide 2- Methylpropanesulfonic acid sodium salt polymer (molecular weight: about 300,000) 18.0 g (5% by weight of monomer) was added. Thereafter, nitrogen is introduced from the nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ° C. using a constant temperature water bath. Thirty minutes after the introduction of nitrogen, 0.275% by weight of an aqueous solution of 0.2% by weight ammonium peroxodisulfate and 0.2% by weight aqueous solution of ammonium hydrogensulfite was added in this order, respectively, to initiate polymerization. 2 hours after the addition of the initiator, the viscosity of the reaction liquid slightly increased but did not increase any more. After 6 hours from the start of polymerization, the same amount of the initiator was added, and the polymerization was continued for another 15 hours. finished. This prototype is designated Prototype-4. In this trial production-4, the molar ratio of acrylic acid / acrylamide 2-methylpropanesulfonic acid / acrylamide was 45/5/50, and the viscosity was 930 mPa · s. The composition is shown in Table 1, and the polymerization results are shown in Table 2.

Synthesis Example 5 Deionized water: 116.9 g, 60% acrylic acid: 31.9 g, itaconic acid powder: 4 in a four-necked 500 ml separable flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube .3 g, 80% aqueous solution of methacryloyloxyethyltrimethylammonium chloride: 8.6 g, 50% acrylamide: 47.2 g, ammonium sulfate 59.1 g, phosphate esterified starch powder: 5.4 g (10% by weight monomer) And 27.0 g of acrylamide 2-methylpropanesulfonic acid sodium salt polymer (15% aqueous solution, molecular weight of about 300,000) (10% monomer). Thereafter, nitrogen is introduced from the nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ° C. using a constant temperature water bath. Thirty minutes after the introduction of nitrogen, 0.275% by weight of an aqueous solution of 0.2% by weight ammonium peroxodisulfate and 0.2% by weight aqueous solution of ammonium hydrogensulfite was added in this order, respectively, to initiate polymerization. 2 hours after the addition of the initiator, the viscosity of the reaction liquid slightly increased but did not increase any more. After 6 hours from the start of polymerization, the same amount of the initiator was added, and the polymerization was continued for another 15 hours. finished. This prototype is designated Prototype-5. In this trial production-5, the molar ratio of acrylic acid / itaconic acid / methacryloyloxyethyltrimethylammonium chloride / acrylamide was 40/5/5/50, and the viscosity was 510 mPa · s. The composition is shown in Table 1, and the polymerization results are shown in Table 2.

(Synthesis Example 6) A four-necked separable flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube was charged with an acryloyloxyethyltrimethylammonium chloride 80% aqueous solution: 13.1 g and an acrylamide 50% aqueous solution: 69. 0.1 g, dimethyldiallylammonium chloride polymer (35% aqueous solution, molecular weight about 100,000): 6.4 g (5% monomer), acryloyloxyethyltrimethylammonium chloride polymer (20% aqueous solution, molecular weight 600,000) ): 11.6 g (5% monomer), ion-exchanged water 105.8 g, ammonium sulfate 87.6 g, phosphate esterified starch powder: 4.5 g (10% monomer) and glycerin: 2.3 g Was completely dissolved. After maintaining the internal temperature at 33 to 35 ° C. and replacing with nitrogen for 30 minutes, 1% of 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride as an initiator Polymerization was started by adding 0.9 g of an aqueous solution (0.2% monomer). After 8 hours from the start, 0.9 g of the initiator solution was added and polymerization was further performed for 8 hours. This sample is referred to as trial production-6. In this trial production-6, the molar ratio of methacryloyloxyethyltrimethylammonium chloride / acrylamide was 10/90, and the viscosity was 150 mPa · s. The results are shown in Table 1, and the polymerization results are shown in Table 2.

Synthesis Example 7 Deionized water: 105.7 g, 60% acrylic acid: 45.3 g, 50% acrylamide: 53 in a four-necked 500 ml separable flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube .6 g, ammonium sulfate 59.1 g, phosphate esterified starch powder: 16.2 g (30% by weight of monomer), and 15% by weight aqueous solution of acrylamide 2-methylpropanesulfonic acid sodium salt polymer (molecular weight: about 300,000) ) 18.0 g (5% by weight of monomer) was added. Thereafter, nitrogen is introduced from the nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ° C. using a constant temperature water bath. Thirty minutes after the introduction of nitrogen, 0.275% by weight of an aqueous solution of 0.2% by weight ammonium peroxodisulfate and 0.2% by weight aqueous solution of ammonium hydrogensulfite was added in this order, respectively, to initiate polymerization. 2 hours after the addition of the initiator, the viscosity of the reaction liquid slightly increased but did not increase any more. After 6 hours from the start of polymerization, the same amount of the initiator was added, and the polymerization was continued for another 15 hours. finished. This prototype is designated Prototype-7. The molar ratio of acrylic acid / acrylamide in this trial production-7 was 50/50, and the viscosity was 870 mPa · s. The composition is shown in Table 1, and the polymerization results are shown in Table 2.

(Comparative Synthesis Example 1) Deionized water: 121.9 g, 60% acrylic acid: 45.3 g, 50% acrylamide in a four-necked 500 ml separable flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube: 53.6 g, ammonium sulfate 59.1 g, and 15 wt% aqueous solution of acrylamide 2-methylpropanesulfonic acid sodium salt polymer (molecular weight: about 300,000) 18.0 g (5 wt% monomer) were added. Thereafter, nitrogen is introduced from the nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ° C. using a constant temperature water bath. Thirty minutes after the introduction of nitrogen, 0.275% by weight of an aqueous solution of 0.2% by weight of ammonium peroxodisulfate and 0.2% by weight of an aqueous solution of ammonium bisulfite was added in this order, respectively, to initiate polymerization. 2 hours after the addition of the initiator, the viscosity of the reaction liquid slightly increased but did not increase any more. After 6 hours from the start of polymerization, the same amount of the initiator was added, and the polymerization was continued for another 15 hours. finished. This prototype is referred to as comparison-1. The molar ratio of acrylic acid / acrylamide in Comparative-1 was 50/50, and the viscosity was 540 mPa · s. The composition is shown in Table 1, and the polymerization results are shown in Table 2.

(Comparative Synthesis Example 2) A four-neck 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube was added to deionized water: 84.1 g, 60% acrylic acid: 45.3 g, 50% acrylamide: 53.6 g, ammonium sulfate 59.1 g, phosphate esterified starch powder: 37.8 g (70% by weight of monomer), and 15% by weight aqueous solution of acrylamide 2-methylpropanesulfonic acid sodium salt polymer (molecular weight: about 30) 18.0 g (5% by weight of monomer) was added. Thereafter, nitrogen is introduced from the nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ° C. using a constant temperature water bath. Thirty minutes after the introduction of nitrogen, 0.275% by weight of an aqueous solution of 0.2% by weight ammonium peroxodisulfate and 0.2% by weight aqueous solution of ammonium hydrogensulfite was added in this order, respectively, to initiate polymerization. 2 hours after the addition of the initiator, the viscosity of the reaction liquid slightly increased but did not increase any more. After 6 hours from the start of polymerization, the same amount of the initiator was added, and the polymerization was continued for another 15 hours. finished. This prototype is referred to as Comparison-2. The molar ratio of acrylic acid / acrylamide in Comparative-2 was 50/50, and the viscosity was 1050 mPa · s. The composition is shown in Table 1, and the polymerization results are shown in Table 2.

ＡＡＣ：アクリル酸、ＩＡ：イタコン酸、ＡＭＳ：アクリルアミド２−メチルプ
ロパンスルホン酸、ＡＡＭ：アクリルアミド、ＤＭC：メタクリロイルオキシエチルトリメチルアンモニウム塩化物、多糖類A：燐酸エステル化澱粉 (Table 1)

AAC: Acrylic acid, IA: Itaconic acid, AMS: Acrylamide 2-methylpropanesulfonic acid, AAM: Acrylamide, DMC: Methacryloyloxyethyltrimethylammonium chloride, Polysaccharide A: Phosphate esterified starch

分散液粘度：ｍＰａ・ｓ (Table 2)

Dispersion viscosity: mPa · s

After disassembling the corrugated cardboard with a pulper, beat it with a Niagara-type beater, F. Adjusted to S = 320 ml. A 2% liquid band was added to this dispersion to adjust the pH to 4.9. The obtained pulp slurry was diluted to 0.5%, and the papermaking pH was measured. Then, 1 L was put into a tap stand standard dough machine (1/16 m2) to make paper with a dry basis weight of 80 g / m2. A filter paper and a cup plate were placed on the wet sheet on the wire, and the wet paper was transferred to the filter paper by applying the cupty roll three times. This was designated as A layer. Next, paper with a dry basis weight of 80 g / m 2 was made in the same manner, and the wet paper with the wire was placed on the direct balance, and the predetermined dilution concentrations described in Table 3 were used as prototypes 1 to 7 prepared in each synthesis example. The dispersion was diluted by spraying from a 6.25 g nozzle at a pressure of 2.5 atm. This was designated as layer B.

The A layer was combined with the B layer with the filter paper attached, and then the filter paper was peeled off. Return this to the sheet machine together with the wire, fill the sheet machine with water, drain the water filled to the bottom of the wire, dewater it under reduced pressure, place a new filter paper, and apply the cupolol three times. Transfered to filter paper. The transferred wet paper was sandwiched between two filter papers, pressed at a pressure of 3 Kg / m 2 for 5 minutes, and then dried with a rotary dryer to obtain a laminated paper. After the humidity control of the obtained laminated paper, J-TAPPI paper pulp test method NO. T-peel strength (gf / 5 cm) was measured according to 19-77. The results are shown in Table 3.

As a comparative test, the test was performed using Comparative-1 to Comparative-2 by the same operation as in Example 1. In addition, the comparative sample (Comparative-3) and the potato starch (Comparative-4) prepared by mixing 10% by weight of phosphate esterified starch with the monomer of Comparative-1 to the predetermined dilution concentrations described in Table 3 were used. A test of spraying the diluted dispersion was performed at the same time. The results are shown in Table 3.

After disintegrating LBKP with a pulper, it was beaten with a Niagara type beater. F. Adjusted to S = 430 ml. A 2% liquid band was added to this dispersion to adjust the pH to 4.9. Thereafter, papermaking was performed in the same procedure as in Example 1, and drying and paper quality measurement were performed. The results are shown in Table 4.

As a comparative test, the test was performed using Comparative-1 to Comparative-2 by the same operation as in Example 2. Further, a comparative sample (Comparative-3) and a potato starch (Comparative-4) in which 10% by weight of phosphate esterified starch was mixed with the sample of Comparative-1 were adjusted to the predetermined dilution concentrations described in Table 4. A test of spraying the diluted dispersion was performed at the same time. The results are shown in Table 4.

LBKP was disintegrated with a pulper and beaten with a Niagara type beater. F. Adjusted to S = 430 ml. A liquid band of 0.5% was added to this dispersion to adjust the pH to 6.3. The obtained pulp slurry was diluted to 0.5%, and the papermaking pH was measured. Then, 1 L was put into a tap stand standard dough machine (1/16 m2) to make paper with a dry basis weight of 80 g / m2. Thereafter, papermaking was carried out by the same operation as in Example 1, followed by drying and measurement. The results are shown in Table 5.

As a comparative test, the test was performed using Comparative-1 to Comparative-2 by the same operation as in Example 3. In addition, the comparative sample (Comparative-3) and the potato starch (Comparative-4) in which 10% by weight of phosphate esterified starch was mixed with the sample of Comparative-1 were adjusted to the predetermined dilution concentrations described in Table 5. A test of spraying the diluted dispersion was performed at the same time. The results are shown in Table 5.

塗布濃度：重量％、塗布量：Ｇ／ｍ２Ｔ字剥離強さ：（ｇｆ／５ｃｍ）











(Table 3)

Coating concentration:% by weight, coating amount: G / m2T-shaped peel strength: (gf / 5 cm)

塗布濃度：重量％、塗布量：Ｇ／ｍ２Ｔ字剥離強さ：（ｇｆ／５ｃｍ）










(Table 4)

Coating concentration:% by weight, coating amount: G / m2T-shaped peel strength: (gf / 5 cm)

塗布濃度：重量％、塗布量：Ｇ／ｍ２Ｔ字剥離強さ：（ｇｆ／５ｃｍ） (Table 5)

Coating concentration:% by weight, coating amount: G / m2T-shaped peel strength: (gf / 5 cm)

The interlaminar strength improver for spraying of the present invention comprises a dispersion of ionic polymer fine particles in an aqueous salt solution, and expresses the adhesive force between the layer fixed on the paper layer surface and the other layer in the dispersion. In addition, it contains a polysaccharide-acrylamide surface grafting component that selectively dissolves and permeates in the dryer part and improves the internal strength of the paper layer. Can be prevented from peeling. As a result, the same interlaminar strength is exhibited with an addition amount of one-fifth to one-twentieth of starch, and a laminated paper can be produced at a lower cost than in the past. Therefore, industrial utility value is high.

Claims (9)

In the method for producing two or more layers of combined paper including a step of pressing and then drying the wet paper layer after forming the paper layer, a water-soluble ionic monomer is essential in an aqueous salt solution, If necessary, a water-soluble nonionic monomer copolymerizable therewith is added, and at least one polysaccharide is dispersed in the aqueous salt solution without being gelatinized. From a dispersion of ionic polymer fine particles obtained by coexisting a soluble polymer dispersant in the aqueous salt solution in the presence of 1 to 50% by weight and dispersing and polymerizing at a temperature below the gelatinization temperature with stirring. An interlayer strength improver. The ionic polymer comprises 2 to 100 mol% of a monomer of the following general formula (1) and 0 to 98 mol% of a water-soluble nonionic monomer that can be copolymerized. The interlayer strength improver described in 1.

General formula (1)
Where R1 is hydrogen, methyl group or carboxymethyl group, A is SO3, C6H4SO3, CONHC (CH3) 2CH2SO3, C6H4COO or COO, R2 is hydrogen or COOY2, Y1 or Y2 is hydrogen or cation, respectively The ionic polymer comprises 2 to 70 mol% of the monomer of the following general formula (2) and / or (3), 0 to 70 mol% of the monomer of the general formula (1), and a copolymerizable water solution. The interlayer strength improver according to claim 1, comprising 10 to 98 mol% of a nonionic monomer.

General formula (2)
Here, R3 is hydrogen or a methyl group, R4 and R5 are alkyl or alkoxyl groups having 1 to 3 carbon atoms, and R6 is hydrogen, an alkyl group having 1 to 3 carbon atoms, an alkoxyl group or a benzyl group, which may be the same or different. , A represents oxygen or NH, B represents an alkylene group or alkoxylene group having 2 to 4 carbon atoms, and X1 represents an anion.

General formula (3)
Here, R7 represents hydrogen or a methyl group, R8 and R9 each represent an alkyl group having 1 to 3 carbon atoms, an alkoxy group or a benzyl group, and X3 represents an anion. The monomer of the general formula (1) is one or more selected from (meth) acrylic acid, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, or a salt thereof. The interlayer strength improver according to any one of? The interlayer strength improver according to any one of claims 1 to 3, wherein the mixture of monomers contains at most 0.5 wt% of a crosslinkable vinyl monomer. The interlayer strength improver according to any one of claims 1 to 3, wherein the polymer dispersant soluble in the aqueous salt solution is an ionic polymer. The interlayer strength improver according to claim 1, wherein the polysaccharide comprises 5 to 25% by weight based on the monomer mixture. The interlayer strength improver according to claim 1 or 7, wherein the gelatinization temperature of the polysaccharide is 40 to 100 ° C. The ionic polymer according to any one of claims 1 to 8, wherein the wet paper layer after forming the paper layer is pressed after combining, and further comprising a step of drying and further comprising two or more layers of combined paper. A method for improving interlayer strength, comprising using a dispersion of fine particles as an interlayer strength improver.