JP2002294595A - Method for producing paperboard - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing combination paper by which both a sufficient improvement in ply bond strength and an improvement in strength (internal strength) in the Z direction of a paper sheet itself are achieved without increasing chemical cost when the surface of a wet paper web ply before combination is coated or sprayed with a ply adhesive to improve the ply bond strength in the method for producing the >=2-ply combination paper comprising steps of combining each wet paper web ply after forming the paper ply, then pressing the combined ply and further drying the pressed ply. SOLUTION: This method for producing a paperboard comprises spray-adding a mixture dispersion containing anionic water-soluble polymer fine particles produced by dispersing and polymerizing monomers consisting essentially of (meth)acylic acid in the coexistence of a dispersing agent composed of an ionic polymer in an aqueous solution of a salt and having <=100 μm particle diameter and starch particles before gelatinization to the surface of the wet paper web ply before combination.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a laminated paper, and more particularly, to a two-layer method comprising the steps of laminating a wet paper layer after forming the paper layer, pressing the laminated paper layer, and then drying. In the above method for producing a laminated paper, the (meth) acrylic acid is mainly applied to the surface of the wet paper layer before the lamination containing the internally added amphoteric paper strength enhancer, cationic and / or anionic polymer. Anionic water-soluble polymer fine particles having a particle size of 1 to 100 μm produced by dispersing and polymerizing a water-soluble monomer made of an ionic polymer in the presence of an ionic polymer, and starch before gelatinization. The present invention relates to a method for producing a laminated paper, which comprises spray-adding a mixture dispersion of particles.

[0002]

2. Description of the Related Art Conventionally, raw starch or phosphate starch has been used as an interlayer strength improver for paper.
Is generally used. JP-A-11-36
No. 195 proposes a method of dissolving an amphoteric polymer electrolyte in water to form a polyion complex and spraying it as an interlayer strength improver. Japanese Patent Application Laid-Open No. 10-331100 proposes a method of spraying a dispersion containing polymer fine particles containing (meth) acrylic acid. As a method for improving paper quality, an anionic or amphoteric acrylamide polymer is added to a wet end to improve paper quality. This internally-added paper quality improver has a disadvantage that the yield rate becomes poor in the high addition region, and the desired paper quality cannot be obtained. In addition, Tokuhei 8-330
No. 00 discloses a water-soluble and / or aqueous dispersion of an anionic polymer substance applied to the surface of a wet paper layer before lamination containing an anionic paper strength enhancer and a cationic paper strength enhancer. After that, there is disclosed a method for producing a paperboard which is made by a conventional method.

[0003] However, when an anionic paper strength enhancer and a cationic paper strength enhancer are internally added as in the method for producing a laminated paper described in Japanese Patent Publication No. 8-33000, it is later applied or sprayed. It is not efficient in the reaction with the interlayer adhesive to be added, and the interlayer strength is not sufficiently exhibited. The reason is that if the anionic paper strength agent and the cationic paper strength agent are separately added, the paper strength enhancer is distributed "thinly" uniformly evenly, and the sheet itself is pulled or ruptured. No strength developed. Paper strength is developed by the contact hydrogen bonding force between pulp fibers. It is considered that the paper strength enhancer improves the strength by reinforcing the strength of the contact and increasing the number of contacts. However, the size of the polymer fine particles generated by the addition of the paper strength enhancer is extremely small as compared with the inter-fiber distance and the contact area. In order to make this difference in scale even closer, ion complex type paper strength enhancers (amphoteric or mixed type) and dispersion type paper strength enhancers have been developed.

[0004] The interlayer adhesive to be applied (sprayed) at the time of laminating has a very low effect when it is soluble in water. Most of them desorb with water during press dewatering. To compensate for this, a method of adding internally before lamination has been devised, but this is not sufficient. Further, in the method of adding the water-dispersible fine particles, if the internal additive at the previous stage is “thinly” uniformly distributed on average, even if the water-dispersible fine particles are added at the later stage, the internal additive and the water are not added. The reaction with the dispersible fine particles hardly occurs and the efficiency is low. Particularly, the water-dispersible fine particles described in JP-B-8-33000 are styrene / monoalkyl maleate / methyl methacrylate terpolymer or 60 mol% of styrene / 25 mol% of acrylate / acrylamide. It is a copolymer consisting of 10 mol% / ammonium acrylate 5 mol%, is not a polymer having strong hydrogen bonding ability like a polymer mainly composed of acrylamide, and has a weak adhesive effect.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing two or more layers of laminated paper, which comprises the steps of laminating a wet paper layer after forming the paper layer, pressing the laminated paper layer, and then drying. When applying or spraying an interlayer adhesive on the surface of the wet paper layer before laminating to improve the interlayer strength, it is possible to sufficiently increase the interlayer strength and increase the Z-direction strength of the paper sheet itself without increasing the chemical cost. (Internal strength) It is an object of the present invention to provide a method for producing a laminated paper which can also achieve an improvement in (internal strength).

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the following invention has been achieved. That is,
The invention of claim 1 of the present invention relates to a method for producing a two- or more-layer laminated paper including a step of pressing after mixing the wet paper layer after forming the paper layer and further drying, A particle system 100 μm produced by dispersing and polymerizing a monomer mainly composed of (meth) acrylic acid on the surface of a wet paper layer and a dispersant comprising an ionic polymer in an aqueous salt solution.
The present invention relates to a method for producing a laminated paper, comprising spray-adding a mixture dispersion containing the following anionic water-soluble polymer fine particles and starch particles before gelatinization.

[0007] The invention of claim 2 is that the water-soluble monomer mainly composed of (meth) acrylic acid is composed of 30- (meth) acrylic acid.
2. The method for producing paperboard according to claim 1, comprising 100 mol%, 0 to 70 mol% of acrylamide and 0 to 20 mol% of another copolymerizable monomer.

A third aspect of the present invention is the method for producing paperboard according to the first aspect, wherein the ionic equivalent of the dispersant comprising an ionic polymer is 1.5 to 15 meq / g.

According to a fourth aspect of the present invention, the weight percentage of the anionic water-soluble polymer particles in the mixture dispersion is represented by a, and the weight percentage of the starch particles before gelatinization is represented by b: a: b
= 5: 95 to 60:40. The method for producing paperboard according to claim 1, wherein:

The invention according to claim 5 is the method for producing paperboard according to claim 1, characterized in that the wet paper layer before lamination contains an amphoteric paper strength enhancer.

The invention according to claim 6 is that the amphoteric paper strength enhancer comprises 2 to 20 mol% of a cationic vinyl monomer, 2 to 20 mol% of an α, β-unsaturated mono- and / or dicarboxylic acid and 60 to 60% of acrylamide. The method for producing a laminated paper according to claim 5, wherein the polymer is a polymer produced by copolymerizing a monomer mixture consisting of 96 mol%.

The invention according to claim 7 is characterized in that the wet paper layer before the lamination contains a cationic water-soluble polymer and / or an anionic water-soluble polymer. Is a method for producing paperboard.

The invention according to claim 8 is characterized in that the cationic water-soluble polymer is produced by copolymerizing a monomer mixture comprising 2 to 20 mol% of a cationic vinyl monomer and 80 to 98 mol% of acrylamide. And an anionic water-soluble polymer containing 2 to 20 mol% of an α, β-unsaturated mono- and / or dicarboxylic acid and acrylamide 80 to 9
8. The method for producing paperboard according to claim 7, wherein the polymer is a polymer produced by copolymerizing a monomer mixture consisting of 8 mol%.

According to a ninth aspect of the present invention, the dispersion containing the anionic water-soluble polymer fine particles at the time of spray addition and the starch particles before gelatinization is 0.01% in total concentration of both components.
The method for producing paperboard according to claim 1, wherein the amount is from 5.0 to 5.0% by weight.

A tenth aspect of the present invention is a method for producing two or more layers of laminated paper, comprising the steps of combining the wet paper layers after forming the paper layers, then pressing and drying. 0.025 to the wet paper layer before lamination
2. The method for producing paperboard according to claim 1, wherein 1.5 g / m <2> spray is added.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The anionic water-soluble polymer comprising a dispersion produced by the dispersion polymerization method used in the present invention is obtained by mixing a water-soluble monomer containing (meth) acrylic acid with an aqueous salt solution. This is a polymer dispersion produced by a dispersion polymerization method in the presence of a dispersant comprising a polymer soluble in the salt aqueous solution. As the acid monomer used, methacrylic acid or acrylic acid is used, and in some cases, itaconic acid or maleic acid is used in combination with these acids. Further, the dispersion liquid composed of the polymer fine particles 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,
Examples thereof include N-vinylacetamide, and copolymerization with one or more of these acid monomers or nonionic monomers is possible. The most preferred combination is acrylic acid and acrylamide. The proportion of these acid monomers in the (co) polymer is from 20 to 100 mol%, preferably from 30 to 100 mol%.

The molecular weight of the polymer constituting the dispersion is from 500,000 to 5,000,000, preferably from 1,000,000 to 5,000,000.
5 million. If it is less than 500,000, the interlayer adhesion effect is not sufficient, and if it is 5,000,000 or more, the solubility in the dryer-drying decreases, resulting in a decrease in the adhesive effect.

In preparing the dispersion comprising the polymer fine particles used in the present invention, any of anionic and cationic polymers can be used as a dispersant. As the anionic polymer, a homopolymer of an anionic monomer or a copolymer of an anionic monomer and a nonionic monomer can be used. Examples of non-ionic monomers include:
Acrylamide, N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, N, N-dimethylacrylamide, acrylonitrile, diacetoneacrylamide, 2-hydroxyethyl (meth) acryle
And so on. Examples of the anionic monomer include 2-acrylamide 2-methylpropanesulfonic acid, styrenesulfonic acid, (meth) acrylic acid, and the like.

Examples of the cationic polymer include homopolymers such as (meth) acryloyloxyethyltrimethylammonium chloride, dimethyldiallylammonium chloride, and (meth) acryloylaminopropyltrimethylammonium chloride; And a non-ionic monomer. A homopolymer of acryloyloxyethyltrimethylammonium chloride or dimethyldiallylammonium chloride is preferably used. The cationic polymer used as a dispersant has a cation equivalent of 1.5 to 15
meq / g, preferably 4.0 to 15 meq / g
It is. The proportion added to the monomer is 1% to 10%, preferably 2% to 5%.

The salts used at the time of polymerization include salts of alkali metal ions such as sodium and potassium or ammonium ions with halide ions, sulfate ions, nitrate ions and phosphate ions. Are more preferred. The concentration of the salt solution is not less than 5% by weight and not more than the saturation concentration.

Next, a method for producing a dispersion composed of polymer fine particles used in the present invention will be described. An aqueous solution of an inorganic salt used as a dispersion medium is prepared, an ionic polymer serving as a dispersant is added to the aqueous salt solution, and (meth) acrylic acid used as a raw material and a nonionic monomer are mixed and mixed. After forming the solution, polymerization is carried out with stirring. At this time, the acid monomer is not neutralized. Therefore, in the polymer of the present invention, the polymer particles do not dissolve in the acidic to weakly acidic region, and the particles start dissolving only when the pH reaches around 7. Usually, the polymerization conditions are appropriately determined depending on the monomers used and the molar percentage of copolymer, and the temperature is in the range of 0 to 100 ° C.

The polymerization is initiated using a radical polymerization initiator,
It may be either oil-soluble or water-soluble, and can be polymerized by any of azo, peroxide and redox systems. Examples of the oil-soluble azo initiator include 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexanecarbonitrile), and 2,2′-azobis (2
-Methylbutyronitrile), 2,2'-azobis (2-
Methyl propionate), 4,4-azobis (4-methoxy-2,4dimethyl) valeronitrile, etc., which are dissolved in a water-miscible solvent and added.

Examples of the water-soluble azo initiator include 2,
2′-azobis (amidinopropane) dichloride,
2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 4, 4 ′
-Azobis (4-cyanovaleric acid) and the like. Examples of the redox system include a combination of ammonium peroxodisulfate with sodium sulfite, sodium bisulfite, trimethylamine, tetramethylethylenediamine, and the like. Further examples of peroxides are ammonium or potassium peroxodisulfate,
Examples include hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, t-butylperoxy 2-ethylhexanoate and the like. Most preferred among these initiators are water-soluble azo initiators2,
2′-azobis (amidinopropane) dichloride,
2,2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride.

The starch to be mixed with the anionic water-soluble polymer fine particles is a raw starch or a modified starch which is usually used for laminating. For example, cones,
Raw starch such as potato and tapioca, or phosphorylated starch, acetylated starch, and cationized starch obtained by modifying these.

The mixing ratio of the anionic water-soluble polymer fine particles to the starch particles before gelatinization is represented by a:% by weight of the anionic water-soluble polymer fine particles in the mixture dispersion, and the weight of the starch particles before gelatinization. %: B: a: b = 5: 9
5:60:40, preferably a: b = 8: 92-
50:50, more preferably 10: 90-5.
0:50.

When the mixture dispersion comprising the anionic water-soluble polymer fine particles used in the present invention and starch particles before gelatinization is spray-coated, the mixture is diluted to a desired concentration and spray-coated. The magnification can be freely selected. In general, conventional starch is spray-coated after being diluted and dispersed to a concentration of about 0.5 to 5% by weight, whereas the product of the present invention is
A method of spray-coating at a concentration of about 0.01 to 5% by weight, preferably 0.1 to 5% by weight can be used. If it is desired to spray-coat more polymer as a paper quality improver, spray-coating is possible even at a concentration of about 0.5 to 5% by weight. 0.025 to 1.5 g / m
2, preferably 0.1 to 0.5 g / m2.

The dispersion of the mixture of the anionic water-soluble polymer fine particles and the starch particles before gelatinization used in the present invention, when sprayed on a wet paper layer made of neutral or weakly alkaline paper, undergoes a drying process. The polymer particles hardly dissolve until heated, and the polymer fine particles do not penetrate into the wet paper layer and remain on the surface of the paper layer. After paper making, wet paper layers are combined and
In the dehydrated state, the polymer particles stay between the paper layers. After that, the polymer particles are melted by the moisture remaining in the paper layer only after being heated by a dryer part, and the polymer is diffused only around the particles, thereby bonding the pulp fibers.

[0028] In general, starch is inexpensive and is one tenth to one fifteenth in comparison with anionic water-soluble polymer fine particles. Therefore, it is not possible to spray a large amount of anionic water-soluble polymer fine particles in terms of cost. For this reason, the addition amount is inevitably low, such as 0.05 to 0.2 g / m 2, so that the interlayer strength may not be increased to a target value. At this time, the amount of addition can be supplemented by spraying the mixture dispersion. Further, in the case of starch, even if the addition amount is increased to 1.0 to 2.0 g / m2, Z
The strength in the direction (internal strength) does not easily improve. On the other hand, the strength of anionic water-soluble polymer fine particles, which is an acrylic polymer, is more easily expressed than that of starch, and it is preferable to use a mixture dispersion.

As a further disclosure of the present invention, an amphoteric paper strength enhancer used in combination in the present invention will be described. That is, the amphoteric paper strength enhancer is a cationic vinyl monomer 2
Weight average molecular weight of 100,000 to 5 prepared by copolymerizing a monomer mixture consisting of 2 to 20 mol% of α, β-unsaturated mono- and / or dicarboxylic acid and 60 to 96 mol% of acrylamide. , 000 000 copolymer. The copolymer can be produced by using a known polymerization method, but one obtained by an aqueous solution polymerization method is convenient. As the polymerization initiator, any of an azo type, a persulfate type and a redox type can be used. When a polyunsaturated bond crosslinking agent such as methylenebisacrylamide is used, any of an azo type, a persulfate type, or a redox type may be used, but a crosslinkable or branched polymer using a thermally crosslinkable monomer such as N-substituted acrylamide may be used. When synthesizing a union,
It is better to use persulfate or redox.

The cationic vinyl monomer is generally a vinyl-based water-soluble monomer having a tertiary amino group, such as dimethylaminoethyl acrylate, dimethylaminopropyl acrylate and the corresponding methacrylate, acrylamide, N- (dimethylaminopropyl) acrylamide which is a derivative of methacrylamide,
N- (diethylaminopropyl) acrylamide and the corresponding methacrylamide. The molar ratio of copolymerization of these cationic vinyl monomers is 2 to 20 mol%, preferably 3 to 10 mol%.

On the other hand, the α, β-unsaturated mono- and / or dicarboxylic acids include acrylic acid and methacrylic acid as examples of α, β-unsaturated monocarboxylic acids, and α, β-unsaturated dicarboxylic acids as examples of α, β-unsaturated dicarboxylic acids. Maleic acid, fumaric acid, itaconic acid and citraconic acid can be mentioned. These can also be used as alkali metal salts or ammonium salts. The copolymer mol% is 2 to 20 mol%, preferably 2 to 15 mol%.

In addition to the essential components, the monomer mixture may contain other copolymerizable monomers such as acrylonitrile, methacrylonitrile, alkyl acrylate, alkyl methacrylate, and acetic acid, as long as the object of the present invention is not impaired. Vinyl, styrene and the like can also be contained.

The cationic water-soluble polymer is a polymer produced by copolymerizing a monomer mixture comprising 2 to 20 mol% of a cationic vinyl monomer and 80 to 98 mol% of acrylamide. Examples of cationic vinyl monomers are vinyl-based water-soluble monomers having a tertiary amino group, such as dimethylaminoethyl acrylate, dimethylaminopropyl acrylate and the corresponding methacrylate, or acrylamide or methacrylamide. Derivatives such as N- (dimethylaminopropyl) acrylamide, N- (diethylaminopropyl) acrylamide and the corresponding methacrylamide. The copolymer mol% of these cationic vinyl monomers is 2 to 20.
Mol%, preferably 3 to 10 mol%. On the other hand, the anionic water-soluble polymer is a polymer produced by copolymerizing a monomer mixture consisting of 2 to 20 mol% of α, β-unsaturated mono- and / or dicarboxylic acid and 80 to 98 mol% of acrylamide. is there. α, β-unsaturated mono- or dicarboxylic acids include acrylic acid, methacrylic acid, etc. as examples of α, β-unsaturated monocarboxylic acids, and maleic acid, fumaric acid, itacone as examples of α, β-unsaturated dicarboxylic acids. Acid and citraconic acid. These can also be used as alkali metal salts or ammonium salts. The copolymer mol% is 2 to 20 mol%, preferably 2 to 15 mol%.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. Further,% in each example is% by weight.

(Synthesis Example 1) In a four-necked 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube, deionized water: 182 g, 80% acrylic acid:
38.1 g, 50% acrylamide: 72 g, 40% dimethyldiallylammonium chloride polymer (intrinsic viscosity: 0.8) 7.5 g, sodium sulfate: 12 g, nitrogen was introduced from a nitrogen introduction tube with stirring and dissolved oxygen was introduced. Perform removal. During this time, the internal temperature is adjusted to 45 ° C. by a constant temperature water bath. 30 minutes after nitrogen introduction, 2 g of an aqueous solution of 2% 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride: 1 g is added to start a polymerization reaction. The polymerization reaction was continued at 45 ° C. for 10 hours and then stopped. This reaction product is designated as prototype-1.

Prototype-1 was a copolymer having a polymer concentration of 21.3% excluding a dispersant, acrylic acid: 40 mol%, and acrylamide: 60 mol%.
It was 80 mPa · s. As a result of microscopic observation, 5
It was found to be particles of ２０20 μm. The dispersion obtained by diluting the prototype-1 with distilled water 20-fold was dissolved at 73 ° C. Table 1 shows the results. In addition, the weight average molecular weight was measured by a molecular weight measuring device (Otsuka Electronics DLS-7000) by a static light scattering method.

(Synthesis Example 2) In a four-necked 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube, 112 g of deionized water and 80% acrylic acid:
16.88 g, 50% acrylamide: 108 g, 20% acryloyloxyethyltrimethylammonium chloride polymer (intrinsic viscosity 1.0) 15 as a dispersant
g, sodium sulfate: 15 g, and nitrogen is introduced from a nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 40 ° C. by a constant temperature water bath. 30 minutes after nitrogen introduction, 22.5 g of acrylonitrile was charged, followed by 2% aqueous 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride aqueous solution:
1.6 g are added to initiate the polymerization reaction. 1 at 45 ° C
After the polymerization reaction was continued for 6 hours, 9 g of sodium sulfate was added to obtain Prototype-2.

Prototype-2 was a copolymer having a polymer concentration of 30% excluding the dispersant, acrylic acid: 15 mol%, acrylonitrile: 25 mol%, and acrylamide: 60 mol%. The dispersion viscosity was 960 mPa · s. s.
In addition, as a result of microscopic observation, the particle diameter was 10 to 80 μm. The dispersion containing the heat-soluble polymer obtained by diluting Prototype-2 with distilled water 30-fold was dissolved at 68 ° C. The results are shown in Table 1.

(Synthesis Example 3) Deionized water: 175 g, 80% acrylic acid was placed in a four-necked 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube.
18.0 g, 50% acrylamide: 85.2 g, 20% methacryloyloxyethyltrimethylammonium chloride polymer (intrinsic viscosity 1.1) 15 as a dispersant
g, sodium sulfate: 27 g, and nitrogen is introduced from a nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 45 ° C. by a constant temperature water bath. 30 minutes after nitrogen introduction, acrylonitrile: 10.6 g was charged, followed by 2% aqueous 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride aqueous solution:
The polymerization reaction is started by adding 1.0 g. 1 at 45 ° C
After the polymerization reaction was continued for 0 hours, sodium sulfate: 12 g was added to obtain Prototype-3. Prototype-3 had a polymer concentration excluding the dispersant of 20.1%, acrylic acid: 20 mol%,
Acrylamide: a copolymer of 60 mol% and acrylonitrile 20 mol%, and a dispersion viscosity of 670 mPa ·
s. As a result of microscopic observation, the particle size was 5 to 15
μm. The dispersion containing the heat-soluble polymer obtained by diluting the prototype-3 with distilled water 20-fold was dissolved at 75 ° C. Table 1 shows the results.

(Synthesis example of amphoteric paper strength enhancer) In a four-necked flask equipped with a stirrer, thermometer, reflux condenser and nitrogen gas tube, 319 parts of 50% acrylamide, 22 parts of 60% acrylic acid, dimethylaminoethyl Methacrylate 2
4.6 parts, 3.4 parts of N, N-dimethylacrylamide and 631 parts of ion-exchanged water were charged. The pH of the reaction solution was adjusted to 4.0 using hydrochloric acid, and then dissolved oxygen in the system was removed by passing nitrogen gas. did. Set the temperature of the monomer aqueous solution to 40 ° C
After adding 1 part of ammonium persulfate and 0.1 part of sodium hydrogen sulfite as a polymerization initiator under stirring conditions, the temperature was raised to 80 ° C., and the reaction solution was kept for 5 hours. After completion of the polymerization, ion-exchanged water was added to make the total amount of the polymer 1333 parts, and the solid content was 15%.
A 7,800 cps copolymer was obtained. This is designated as prototype-4. Table 1 shows the results.

(Synthesis example of cationic water-soluble polymer and anionic water-soluble polymer) As in the synthesis example of the amphoteric paper strength enhancer, dimethylaminoethyl methacrylate / acrylamide = 20/80 (molar ratio), acrylic Cationic water-soluble polymer and anionic water-soluble polymer having composition of acid / acrylamide = 15/85 (molar ratio), Prototype-5
And Prototype-6 were synthesized. Similarly, the weight average molecular weight was measured. Table 1 shows the results.

[0042]

Examples 1-6 Papermaking raw materials for liners (pH 5.9, total ss 2.83%, ash content 0.11%), Canadian standard doughness (CFS) 430ML, diluted to 1% Then, after adding 1% of the liquid band, the pH of the pulp slurry was adjusted to pH 6.5 with a 5.0% aqueous sodium carbonate solution.
Was adjusted. 500 ml of this stock was collected, 0.2% of the amphoteric paper strength enhancer of Prototype-4 was added to the pulp, and the mixture was stirred for 20 seconds, and a tappi standard sheet machine (1/16 m
2) and a paper having a dry basis weight of 80 g / m2 was formed. A filter paper and a cut plate were placed on the wet sheet on the wire, and the wet paper was transferred to the filter paper by applying cut-roll three times. This is A
Layers. Next, similarly, paper having a dry basis weight of 80 g / m 2 was made, and the wet paper together with the wire was placed on a direct reading balance, and an anionic water-soluble polymer fine particle diluted to a predetermined mixing ratio and dilution concentration described in Table 2 was prepared. The mixed dispersion composed of the raw corn starch was spray-coated from a 10.0 g nozzle at a pressure of 2.5 atm. This was designated as layer B.

The layer A was combined with the layer B with the filter paper attached, and then the filter paper was peeled off. This was returned to the sheet machine together with the wire, and the sheet machine was filled with water and drained of water filled under the wire to dehydrate under reduced pressure. A new filter paper was placed on the sheet machine, and cuticle roll was applied three times. Transferred to filter paper. The transferred wet paper is sandwiched between two pieces of filter paper, and pressed at a pressure of 3 kg / m2 for 5 minutes.
After pressing for 1 minute, it was dried with a rotary drier to obtain a laminated paper. After conditioning the obtained laminated paper, J-T
APPI paper pulp test method NO. According to 19-77, T
The character peel strength (gf / 5 cm) was measured. Table 2 shows the results.

[0044]

COMPARATIVE EXAMPLES 1 AND 2 By the same operation as in Examples 1 to 6, the preparation of a laminated paper was carried out in the case where a fresh dispersion alone or an anionic water-soluble polymer alone was spray-coated. went. After drying and humidity control, the same measurement was performed. Table 2 shows the results.

From Table 2, it can be seen that in the case of Examples 1 to 6 using the mixed dispersion composed of the raw constarch and the anionic water-soluble polymer, It can be seen from a cost comparison that a paper having high T-peel strength and not only improved interlayer strength but also improved internal strength can be obtained.

[0046]

Examples 7 to 12 By using the same papermaking raw materials as in Examples 1 to 6, an anionic water-soluble polymer, Prototype-6, was used as a papermaking agent internally added to the layer A sheet. Raw material for paper making 0.2%, cationic water-soluble polymer, prototype -5
Was performed when 0.06% was added. The subsequent spray coating, pressing, and drying are the same as in Examples 1 to 6. Table 3 shows the paper quality measurement results.

[0047]

Comparative Examples 3 and 4 The same operations as in Examples 7 to 12 were carried out on the case where the dispersion of the raw constarch alone or the dispersion of the anionic water-soluble polymer alone was spray-coated.

From Table 3, it can be seen that Examples 7 to 12 in which a mixed dispersion composed of a raw constarch and an anionic water-soluble polymer were used.
In the case of (1), compared with the raw dispersion of Comparative Example 1 alone, the T-shaped peel strength is higher even in terms of cost, and not only the interlayer strength is improved but also the internal strength is improved. It can be seen that paper is obtained.

[0049]

[Table 1] AAC: acrylic acid, AAM: acrylamide, AN:
Acrylonitrile DMM: dimethylaminoethyl methacrylate, DAA: dimethylacrylamide Composition represents mole%

[0050]

[Table 2] Mixing ratio: (anionic water-soluble polymer / raw constarch) Dispersion dilution concentration: (%) Coating amount: g / m2 T-shaped peel strength: gf / 5 cm Breaking length: Km Internal strength: Kgf / in2

[0051]

[Table 3] Mixing ratio: (anionic water-soluble polymer / raw constarch) Dispersion dilution concentration: (%) Coating amount: g / m2 T-shaped peel strength: gf / 5 cm Breaking length: Km Internal strength: Kgf / in2

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) D21H 17/43 D21H 17/43 17/45 17/45 19/10 19/10 B 19/20 19/20 A 21 / 10 21/10 21/18 21/18 23/50 23/50 27/00 27/00 EF term (reference) 4J002 AB04X BG01W GK04 HA06 4J100 AJ02R AJ08R AJ09R AK03R AK08R AK19R AK20R AL08Q AM15P AM21Q BA31Q CA04 CA06 DA01 JA13 4L0 AG47 AG71 AG72 AG74 AG89 AG96 AH16 AH18 AH37 AH50 BD03 BD10 BD17 EA14 EA16 EA29 EA32 FA10 FA13 GA05 GA06 GA50

Claims (10)

[Claims] 1. A method for producing a laminated paper having two or more layers, comprising the steps of laminating a wet paper layer after forming a paper layer, pressing the laminated paper, and drying the paper. And an anionic water-soluble polymer fine particle having a particle size of 100 μm or less produced by dispersing and polymerizing a monomer mainly composed of (meth) acrylic acid in the presence of an ionic polymer in an aqueous salt solution. A method for producing a laminated paper, comprising spray-adding a mixture dispersion containing starch particles before gelatinization. 2. A water-soluble monomer mainly composed of (meth) acrylic acid contains 20 to 100 mol% of (meth) acrylic acid, 0 to 80 mol% of acrylamide and 0 to 80 2. The composition according to claim 1, comprising 20 mol%.
3. The method for producing paperboard according to item 1. 3. The paperboard manufacturing method according to claim 1, wherein the dispersant comprising the ionic polymer has an ion equivalent of 1.5 to 15 meq / g. 4. When the weight% of the anionic water-soluble polymer particles in the mixture dispersion is a and the weight% of the starch particles before gelatinization is b, a: b = 5: 95-6.
The method of claim 1, wherein the ratio is 0:40. 5. The method for producing paperboard according to claim 1, wherein an amphoteric paper strength enhancer is contained in the wet paper layer before the lamination. 6. An amphoteric paper strength enhancer comprising 2 to 20% by mole of a cationic vinyl monomer, 2 to 20% by mole of an α, β-unsaturated mono- and / or dicarboxylic acid and 60 to acrylamide.
The method for producing laminated paper according to claim 5, wherein the polymer is a polymer produced by copolymerizing a monomer mixture consisting of 96 mol%. 7. The method for producing paperboard according to claim 1, wherein the wet paper layer before lamination contains a cationic water-soluble polymer and / or an anionic water-soluble polymer. . 8. The polymer produced by copolymerizing a monomer mixture comprising 2 to 20 mol% of a cationic vinyl monomer and 80 to 98 mol% of acrylamide, wherein the cationic water-soluble polymer is used. And the anionic water-soluble polymer is an α, β-unsaturated mono- and / or dicarboxylic acid 2 to 2
The method for producing paperboard according to claim 7, wherein the polymer is a polymer produced by copolymerizing a monomer mixture comprising 20 mol% and 80 to 98 mol% of acrylamide. 9. The dispersion containing the anionic water-soluble polymer fine particles at the time of spray addition and the starch particles before gelatinization is 0.01 to 5.0% by weight in total concentration of both components. The method for producing paperboard according to claim 1, wherein: 10. A method for producing two or more layers of laminated paper, comprising the steps of laminating a wet paper layer after forming a paper layer, pressing and drying the wet paper layer. 2. The method for producing paperboard according to claim 1, wherein 0.025 to 1.5 g / m <2> spray is added to the previous wet paper layer.