JP2003155691A - Interlaminar strength-improving agent and interlaminar strength-improving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interlaminar strength-improving agent which is used on the production of combination paper, has a particle size that is larger than the particle size of a polyion complex or emulsion and is approximately the same as the particle size of starch, does therefore not flow out together with water in a dehydration press part or a suction part, and consequently exhibits the same interlaminar strength in the amount of one-fifth to one-tenth of starch. SOLUTION: This interlaminar strength-improving agent comprises <=100 μm inorganic particle-containing ionic polymer fine particles obtained by dispersing and copolymerizing an ionic water-soluble monomer and a copolymerizable monomer in the presence of inorganic particles and in the coexistence of a polymer dispersant soluble in a salt aqueous solution in the salt aqueous solution with stirring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interlaminar strength improver and an interlaminar strength improving method, and more specifically, it includes a step of pressing a wet paper layer after forming a paper layer, pressing it, and further drying it. In order to improve the interlaminar strength used when producing a laminated paper having two or more layers, an ionic water-soluble monomer and a nonionic monomer copolymerizable therewith in the presence of inorganic particles in an aqueous salt solution are used. 10 obtained by coexisting a soluble polymer dispersant in the salt aqueous solution and carrying out dispersion polymerization with stirring.
The present invention relates to an interlaminar strength improver comprising a dispersion containing ionic polymer fine particles containing an inorganic particle having a size of 0 μm or less, and an interlaminar strength improving method using the same.

[0002]

2. Description of the Related Art Conventionally, as an interlaminar strength improver for paper, there are raw starch and phosphoric acid ester starch.
Is generally used. JP-A-11-36
In 195, a method is proposed in which an amphoteric polymer electrolyte is dissolved in water to form a polyion complex and the polyion complex is sprayed as an interlayer strength improver. Further, JP-A-10-331100 proposes a method of spraying a dispersion liquid containing polymer fine particles containing (meth) acrylic acid. However, since these interlayer strength improvers are sprayed with a polyion complex or emulsion, the particle size of the interlayer strength improvers is too small, and there is a high proportion that they flow out together with water in the dehydration press part or suction part, It is difficult to obtain the desired interlayer strength.

[0003]

DISCLOSURE OF THE INVENTION The object of the present invention is that the interlaminar strength improver to be sprayed is not as fine as the particle size of the polyion complex or emulsion and has the same particle size as that of starch. It is an object to develop an interlaminar strength improver that rarely flows out together with water and, as a result, exhibits the same interlaminar strength with a 1/5 to 1/10 addition amount of starch. Another object of the present invention is to develop a synthetic interlaminar strength improver capable of producing a laminated paper at a lower cost than ever before.

[0004]

Means for Solving the Problems As a result of intensive investigations, the present inventors have arrived at the following invention. The invention of claim 1 of the present invention is a method for producing a laminated paper having two or more layers, which comprises a step of pressing a paper sheet after forming the wet paper layer after forming the paper layer, and further drying, in a salt solution, An ionic water-soluble monomer and a nonionic monomer copolymerizable therewith in the presence of inorganic particles are allowed to coexist with a polymer dispersant soluble in the salt aqueous solution, and dispersion-polymerized under stirring. Obtained 100
It is an interlaminar strength improver composed of a dispersion liquid of ionic polymer fine particles containing an inorganic particle having a size of not more than μm. As a result, the laminated paper can be manufactured at a lower cost than the conventional synthetic interlaminar strength improver.

According to a second aspect of the present invention, the inorganic particle-containing ionic polymer is 2 to 100 mol% of a monomer represented by the following general formula (1), and 0 to 98 mol of a copolymerizable nonionic monomer. % Is the interlayer strength improver according to claim 1.

[Chemical 1] General formula (1) R1 is hydrogen, a methyl group or a carboxymethyl group, A is SO3, C6H4SO3, CONHC (CH3) 2CH
2SO3, C6H4COO or COO, R2 is hydrogen or COOY2, Y1 or Y2 is hydrogen or cation

According to a third aspect of the present invention, the ionic polymer containing inorganic particles comprises 2 to 70 mol% of a monomer represented by the following general formula (2) and / or (3), and a monomer represented by the general formula (1). Quantities 0-7
0 mol% and copolymerizable nonionic monomer 10-98
The interlayer strength improver according to claim 1, wherein the interlayer strength improver is composed of mol%.

[Chemical 2] Formula (2) R3 is hydrogen or a methyl group, R4 and R5 are alkyl or alkoxyl groups having 1 to 3 carbon atoms, R6 is hydrogen, an alkyl group having 1 to 3 carbon atoms, an alkoxyl group, or a benzyl group. May be different, A is oxygen or N
H and B represent an alkylene group having 2 to 4 carbon atoms or an alkoxylene group, and X1 represents an anion.

[Chemical 3] Formula (3) R7 represents hydrogen or a methyl group, R8 and R9 represent an alkyl group having 1 to 3 carbon atoms, an alkoxy group or a benzyl group, and X3 represents an anion.

The invention according to claim 4 is the interlayer strength improver according to claim 1, characterized in that the inorganic particles are one or more selected from bentonite, kaolin, white carbon and talc.

In the invention of claim 5, the monomer of the general formula (1) is one or more selected from (meth) acrylic acid, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid or salts thereof. The interlaminar strength improver according to claim 1, wherein

The sixth aspect of the present invention is the interlaminar strength improver according to the first aspect, wherein the polymer dispersant soluble in the aqueous salt solution is an ionic polymer.

The invention of claim 7 is characterized in that the salt constituting the aqueous salt solution is a divalent anion salt.
The interlayer strength improver described in 1.

The invention of claim 8 includes a step of drying the wet paper layer after forming the paper layer, forming the paper sheet, pressing the paper sheet, and further drying.
A method for producing a laminated paper having more than one layer, wherein:
7. The method for improving interlayer strength, which comprises using the inorganic particle-containing ionic polymer described in 7 as an interlayer strength improver.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The manufacturing method will be specifically described below. The inorganic particle-containing water-soluble polymer dispersion of the present invention is prepared as an aqueous solution of a polyvalent anion salt such as ammonium sulfate,
When synthesizing an anionic polymer, inorganic particles and a water-soluble anionic monomer, a nonionic monomer or a mixture thereof are incorporated therein, and when synthesizing a cationic or amphoteric polymer, an inorganic polymer is used. The particles, water-soluble cationic monomer, nonionic monomer and, if necessary, water-soluble anionic monomer are charged, and a polymeric dispersant soluble in the salt aqueous solution coexists as a dispersant. It can be synthesized by dispersion polymerization under stirring.

The inorganic particles used in the present invention may be any inorganic particles which do not dissolve in an acidic to weakly acidic aqueous solution such as bentonite, talc, clay, kaolin and white carbon, but bentonite, kaolin and talc are more preferred. The fine particles have a particle size of 1 to 100 μm, preferably 1 to 50 μm. Since these particles are usually aggregated as secondary particles or tertiary particles,
Before using for polymerization, it may be used by vigorous stirring with a homogenizer or by swelling with weak stirring for 12 to 24 hours. The mixing ratio of the inorganic particles to the monomer is
The amount is 1 to 300% by mass, preferably 5 to 100% by mass, and more preferably 5 to 50% by mass.

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, the anionic property is more preferable. Examples of anionic polymers include (meth) acrylic acid, maleic acid,
It is a (co) polymer of anionic monomers such as itaconic acid, acrylamido 2-methylpropanesulfonic acid (salt) and styrenesulfonic acid (salt). Furthermore, nonionic monomers such as acrylamide, N-vinylformamide,
N-vinylacetamide, N-vinylpyrrolidone, N,
N-dimethyl acrylamide, acrylonitrile, diacetone acrylamide, 2-hydroxyethyl (meth)
A copolymer with acrylate or the like can also be used. Other, anion-modified polyvinyl alcohol, styrene /
It is a maleic anhydride copolymer, a butene / maleic anhydride copolymer, or a partially amidated product thereof. The most preferred combination is (meth) acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid.

Examples of the cationic polymer include acrylic cationic monomers, for example, salts of inorganic acids and organic acids such as dimethylaminoethyl (meth) acrylate and dimethylaminopropyl (meth) acrylamide, or methyl chloride. It is a copolymer of quaternary ammonium salt and acrylamide with benzyl chloride. For example, (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acryloyloxy 2-hydroxypropyltrimethylammonium chloride, (meth) acryloylaminopropyltrimethylammonium chloride, (meth) acryloyloxyethyldimethylbenzylammonium chloride, ( Examples thereof include (meth) acryloyloxy 2-hydroxypropyldimethylbenzylammonium chloride and (meth) acryloylaminopropyldimethylbenzylammonium chloride. A copolymer of these monomers and a nonionic monomer may be used. It is also possible to use a diallylamine-based polymer such as a dimethyldiallylammonium chloride polymer.

Examples of nonionic polymers include (co) polymers of the above nonionic monomers, polyvinyl alcohol,
Styrene / maleic anhydride copolymers or butene / maleic anhydride copolymers are each completely amidated products.

The molecular weight of the ionic polymer is as follows.
It is 5,000 to 3 million, preferably 50,000 to 1.5 million. Further, as the molecular weight of the nonionic polymer component,
1,000 to 1,000,000, preferably 1,000 to
It is 500,000. The amount of the polymer dispersant added to the monomer is 1/100 to 20/100, preferably 3/100 to 15/100.

The temperature at the time of polymerization is 5 to 50 ° C, preferably 15 to 40 ° C. When the temperature is higher than 50 ° C., it is difficult to control the polymerization, and a rapid temperature rise or agglomeration of the polymerization liquid occurs, so that a stable dispersion liquid having a high polymerization degree is not formed.

A radical polymerization initiator is used to initiate the polymerization. These initiators may be either oil-soluble or water-soluble, and can be polymerized by any of azo type, peroxide type and redox type. Examples of the oil-soluble azo initiator include 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, which are dissolved in a water-miscible solvent and added.

Examples of water-soluble azo initiators include:
2'-azobis (amidinopropane) dihydrochloride,
2,2'-Azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 4,4 '
-Azobis (4-cyanovaleric acid) and the like. Further, examples of the redox system 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,
Examples thereof include hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, t-butylperoxy 2-ethylhexanoate and the like. Most preferred of these initiators are water-soluble azo initiators2,
2'-azobis (amidinopropane) dihydrochloride,
2,2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride.

The anionic monomer used for polymerizing the anionic polymer containing inorganic particles may be a sulfonic acid group-containing monomer, but is preferably a carboxyl group-containing monomer or a carboxyl group-containing monomer. A monomer mixture based on the main component is suitable. Examples of the carboxyl group-containing monomer are methacrylic acid, acrylic acid, itaconic acid, maleic acid, p-carboxystyrene and the like. Further, this polymer dispersion liquid may be a copolymer with another nonionic monomer. For example, (meth) acrylamide, N, N-dimethylacrylamide, vinyl acetate, acrylonitrile,
Examples thereof include methyl acrylate, 2-hydroxyethyl (meth) acrylate, diacetone acrylamide, N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, acryloylmorpholine, and copolymerization with one or more of these. Is possible. The most preferable combination is acrylic acid and acrylamide.

The copolymerization molar ratio of the anionic monomer is 2 to
It is 100 mol%, preferably 5 to 100 mol%. Furthermore, the copolymerization mol% of the non-ionic monomer that can be copolymerized is 0 to 98 mol%, and preferably 0 to 95%.
Mol%.

Next, the polymer containing cationic or amphoteric inorganic particles will be described. The cationic monomer used is an acrylic cationic monomer such as (meth)
Examples include dimethylaminoethyl acrylate and dimethylaminopropyl (meth) acrylamide. Alternatively, it is a quaternary ammonium salt of methyl chloride or benzyl chloride, such as (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acryloyloxy 2
-Hydroxypropyltrimethylammonium chloride,
(Meth) acryloylaminopropyltrimethylammonium chloride, (meth) acryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloyloxy-2-hydroxypropyldimethylbenzylammonium chloride, (meth) acryloylaminopropyldimethylbenzylammonium chloride, etc. Can be given. Further, diallylamine-based monomers such as dimethyldiallylammonium chloride can also be used.

As the anionic monomer or nonionic monomer, the same monomer as used in the synthesis of the anionic inorganic particle-containing polymer is used. In addition, the dispersant used during polymerization is
The above-mentioned cationic polymer is used, and the addition amount is approximately the same as when the anionic inorganic particle-containing polymer is synthesized. The salts constituting the aqueous salt solution are the same as those used in the synthesis of the anionic inorganic particle-containing polymer.

When the cationic polymer dispersion is produced, the molar ratio of the cationic monomer is 2 to 70 mol%,
It is preferably 5 to 50 mol%, more preferably 5
~ 30 mol%. The content of the nonionic monomer is 30 to 98 mol%, preferably 50 to 95 mol%, and more preferably 70 to 95 mol%. In the case of producing an amphoteric polymer dispersion, the content of the cationic monomer is 2 to 70 mol%, preferably 5 to 50 mol%. The anionic monomer content is 2-70 mol%, preferably 5-5.
It is 0 mol%. Non-ionic monomer is 10 to 96 mol%
And preferably 20 to 90 mol%. The most preferred cationic monomer is dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate,
Acryloyloxyethyltrimethylammonium chloride and methacryloyloxyethyltrimethylammonium chloride, the anionic monomer is (meth) acrylic acid, and the nonionic monomer is acrylamide.

The salts used to form the aqueous salt solution are salts of alkali metal ions such as sodium and potassium or ammonium ions with halide ions, sulfate ions, nitrate ions, phosphate ions, etc. More preferred is a salt with a valent anion. The salt concentration of these salts can be from 7% by weight to a saturated concentration.

The polymer concentration of the additive for laminated paper of the present invention is polymerized in the range of about 15 to 35% by mass. If it is less than 15% by weight, the freight cost will be too high and 35% by weight
If it exceeds, the fluidity of the product will be insufficient and it will be difficult to handle.
When the additive for laminated paper of the present invention is spray-coated, it is diluted to a desired concentration and spray-coated, but the dilution ratio can be freely selected. Generally, conventional starch is 0.5
Whereas the product of the present invention is diluted and dispersed to a concentration of about 5 to 5% by mass and spray-coated, a method of spray-coating the product of the present invention at a concentration of about 0.05 to 5% by mass can be used. When it is desired to spray-coat a larger amount of polymer as a paper quality improver, spray-coating is possible even at a concentration of about 0.5 to 5% by mass.

The papermaking pH to which the interlaminar strength improver of the present invention can be applied is about 4.0 or more and 9.0 or less. In general, the pH of papermaking is low even in acidic papermaking in the case of less than 4.0, and if it is less than 4.0, the paper is adversely affected. Also,
When the papermaking pH exceeds 9.0, the solubility of the polymer fine particles is gradually promoted, and the polymer fine particles remaining on the wet paper surface layer are dissolved before being heated by the dryer, so that the press paper is heated.
When it is dehydrated with water, it flows out together with water or penetrates into the wet paper layer, which lowers the adhesive effect, which is not preferable.

[0029]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist.

(Synthesis Example 1) Deionized water: 73.3 g, 60% acrylic acid: 50.0 g, 50% in a four-necked 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube. Acrylamide: 140.3g
66.7 g of bentonite (20% by mass with respect to the monomer) swollen overnight with 30% dispersion with weak stirring, 135.4 g of ammonium sulfate, and 20% by mass.
Acrylamide 2-methylpropanesulfonic acid polymer in aqueous solution (molecular weight: 200,000, 20 equivalent% neutralized product) 25.0
g (5.0% by weight of monomer) was added. Then, while stirring, nitrogen is introduced from the nitrogen introducing pipe to remove dissolved oxygen. During this time, the internal temperature is adjusted to 25 ° C. in a constant temperature water bath. After 30 minutes of introducing nitrogen, 0.2 g by mass of an aqueous solution of 0.2% by mass of ammonium peroxodisulfate and 0.2% by mass of ammonium hydrogen sulfite were respectively added in this order to 2.5 g (to the monomer, 4
0 ppm) was added to initiate polymerization. After 2 hours from the addition of the initiator, the viscosity of the reaction solution slightly increased but did not increase further, and 8 hours after the start of the polymerization, the same amount of each of the above initiators was added, and the polymerization was continued for further 15 hours to carry out the reaction. finished. This prototype is called prototype-1. This prototype-1
The acrylic acid / acrylamide molar ratio was 30/70, and the viscosity was 550 mPa · s. As a result of microscopic observation, it was found that the particles were 2 to 20 μm. After observing this dispersion for 3 months,
No precipitation of inorganic matter was observed, and a stable dispersed state was maintained.
The composition is shown in Table 1 and the polymerization result is shown in Table 2.

(Synthesis Examples 2 to 3) By the same procedure as in Synthesis Example 1, prototypes 2 to 3 composed of acrylic acid / acrylamide = 30/70, bentonite to monomer 40% by mass and 100% by mass were synthesized. The results are shown in Table 1.

(Synthesis Example 4) 18.5 g of deionized water and 60% acrylic acid were placed in a 4-neck 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube.
100.2 g, 50% acrylamide: 80.5 g were further added, and 133.0 g of bentonite (40% by mass of monomer) swollen overnight with 30% dispersion liquid with weak stirring.
135.4 g of ammonium sulfate and 25.0 g of a 20% by weight aqueous solution of acrylamido 2-methylpropanesulfonic acid polymer (molecular weight: 200,000, 20 equivalent% neutralized product) (5.0% by weight of monomer) were added. . Then, while stirring, nitrogen is introduced from the nitrogen introducing pipe to remove dissolved oxygen.
During this time, the internal temperature is adjusted to 25 ° C. in a constant temperature water bath. After 30 minutes of introducing nitrogen, 0.8 g of 2,5'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride 5% by mass aqueous solution was added in this order.
(To monomer, 400 ppm) was added to initiate polymerization.
Two hours after the addition of the initiator, the viscosity of the reaction solution slightly increased, but did not increase any more, and in addition, polymer fine particles began to precipitate and the viscosity also decreased. After 8 hours from the start of the polymerization, the same amount of each of the above initiators was added, and the polymerization was further continued for 15 hours to complete the reaction. This prototype is referred to as prototype-4. The acrylic acid / acrylamide molar ratio of this prototype-4 was 60/40, and the viscosity was 390 mPa · s. As a result of microscopic observation, it was found that the particles were 2 to 20 μm. In the observation after 3 months, no precipitation of inorganic substances was observed and it was stable. The composition is shown in Table 1 and the polymerization result is shown in Table 2.

(Synthesis Example 5) 21.4 g of deionized water and 60% acrylic acid were added to a four-neck 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube.
32.0 g, itaconic acid powder 14.6 g, and 50% acrylamide: 132.2 g were added. Further, 133.0 g of kaolin (40% by weight of monomer) homogenized with a 30% dispersion for 10 minutes at 3000 revolutions / second, 135.4 g of ammonium sulfate, and a 20% by weight aqueous solution of acrylamide 2-methylpropanesulfonic acid polymer ( Molecular weight: 2
25.0 g (versus monomer 5.0)
Mass%) was added. Then, while stirring, nitrogen is introduced from the nitrogen introducing pipe to remove dissolved oxygen. During this time, the internal temperature is adjusted to 25 ° C. in a constant temperature water bath. After 30 minutes of introducing nitrogen, 0.8 g of a 5% by mass aqueous solution of 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride was added in this order (vs. Quantum, 4
00 ppm) to start the polymerization. After 8 hours from the start of the polymerization, the same amount of each of the above initiators was added, and the polymerization was further continued for 15 hours to complete the reaction. This prototype is referred to as prototype-5. The prototype-5 had a molar ratio of acrylic acid / itaconic acid / acrylamide of 20/10/70 and a viscosity of 400 mPa · s. As a result of microscopic observation, it was found that the particles were 2 to 20 μm. In the observation after 3 months, no precipitation of inorganic substances was observed and it was stable. The composition is shown in Table 1 and the polymerization result is shown in Table 2.

(Synthesis example 6) 80.1 g of deionized water and 60% acrylic acid were placed in a four-necked 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube.
61.6 g, acrylamide 2-methylpropanesulfonic acid powder 11.8 g, 50% acrylamide: 81.0
g was added. Further, 100.2 g of talc homogenized with a 30% dispersion liquid at 3000 revolutions / second for 10 minutes (30% by mass of monomer), 135.4 g of ammonium sulfate, and a 20% by mass aqueous solution of acrylamide 2-methylpropanesulfonic acid polymer ( (Molecular weight: 200,000, 20 equivalent% neutralized product) 25.0 g (5.0% by mass of monomer) was added.
Then, while stirring, nitrogen is introduced from the nitrogen introducing pipe to remove dissolved oxygen. During this time, the internal temperature is adjusted to 25 ° C. in a constant temperature water bath. 30 minutes after introduction of nitrogen, 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl)
Propane] A 5 mass% aqueous solution of dihydrochloride was added in this order in an amount of 0.8 g (relative to monomer, 400 ppm) to initiate polymerization. Two hours after the addition of the initiator, the viscosity of the reaction solution slightly increased, but did not increase any more, and in addition, polymer fine particles began to precipitate and the viscosity also decreased. 8 after initiation of polymerization
After a while, add the same amount of each of the initiators,
Polymerization was continued for another 15 hours to complete the reaction. This prototype is called Prototype-6. In this prototype-6, the acrylic acid / acrylamide 2-methylpropanesulfonic acid / acrylamide molar ratio was 45/5/50, and the viscosity was 670.
It was mPa · s. In addition, as a result of the microscope observation, 2 to 2
It was found to be 0 μm particles. In the observation after 3 months, no precipitation of inorganic substances was observed and it was stable. The composition is shown in Table 1.
Table 2 shows the polymerization results.

(Synthesis Example 7) Deionized water: 78.3 g, 60% acrylic acid: 50.0 g, 50% in a 4-neck 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube. Acrylamide: 140.3g
66.7 g of bentonite (20% by mass with respect to the monomer) swollen overnight with 30% dispersion with weak stirring, 135.4 g of ammonium sulfate, and 20% by mass.
20.0 g of dimethyldiallylammonium chloride polymer (molecular weight: 100,000) (4.0% by mass of monomer) was added as an aqueous solution. Then, while stirring, nitrogen is introduced from the nitrogen introducing pipe to remove dissolved oxygen. During this time, the internal temperature is adjusted to 25 ° C. in a constant temperature water bath. 30 minutes after introducing nitrogen,
2.5 g of 0.2 mass% ammonium peroxodisulfate and 0.2 mass% aqueous solution of ammonium hydrogen sulfite were added in this order (to the monomer, 40 ppm) to initiate polymerization. After 8 hours from the start of the polymerization, the same amount of each of the above initiators was added, and the polymerization was further continued for 15 hours to complete the reaction. This prototype is called Prototype-7. This trial-7 had an acrylic acid / acrylamide molar ratio of 30.
It was / 70 and the viscosity was 330 mPa * s. As a result of microscopic observation, it was found that the particles were 2 to 30 μm. In the observation after 3 months, no precipitation of inorganic substances was observed and it was stable. The composition is shown in Table 1 and the polymerization result is shown in Table 2.

Synthesis Example 8 Deionized water: 65.8 g, 60% acrylic acid: 50.0 g, 50% in a 4-neck 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube. Acrylamide: 140.3g
66.7 g of bentonite (20% by mass with respect to the monomer) swollen overnight with 30% dispersion with weak stirring, 135.4 g of ammonium sulfate, and 20% by mass.
Aqueous solution of N-vinylpyrrolidone polymer (Molecular weight: 50,000)
32.5 g (6.5% by weight of monomer) was added. Then, while stirring, nitrogen is introduced from the nitrogen introducing pipe to remove dissolved oxygen. During this time, the internal temperature is adjusted to 25 ° C. in a constant temperature water bath. 30 minutes after introduction of nitrogen, 0.8 g of a 5% by mass solution of 2,2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride (relative to monomer, 400 ppm) Addition started the polymerization. Two hours after the addition of the initiator, the viscosity of the reaction solution slightly increased, but did not increase any more, and in addition, polymer fine particles began to precipitate and the viscosity also decreased. After 8 hours from the start of the polymerization, the same amount of each of the above initiators was added, and the polymerization was further continued for 15 hours to complete the reaction. This prototype is called Prototype-8.
The acrylic acid / acrylamide molar ratio of this prototype-8 was 30/70, and the viscosity was 950 mPa · s.
As a result of microscopic observation, it was found that the particles were 2 to 30 μm. In the observation after 3 months, no precipitation of inorganic substances was observed and it was stable. The composition is shown in Table 1 and the polymerization result is shown in Table 2.

(Synthesis Example 9) A five-necked separable flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube was used.
Dimethyldiallylammonium chloride polymer (30% aqueous solution, molecular weight 200,000) 16.7 g (to monomer 5.0)
%), Ion-exchanged water 48.0 g, 30% dispersion of kaolin homogenized at 3000 rpm, 133.4 g
(40% by mass of monomer), ammonium sulfate 115.0
g, 153.4 g of 50% acrylamide aqueous solution and acryloyloxyethyl trimethyl ammonium chloride,
Then, 29.0 g of 80% aqueous solution was charged and completely dissolved.
The internal temperature was kept at 33 to 35 ° C., and after substituting with nitrogen for 30 minutes, 2,2′-azobis [2- (5-methyl-2-
2.5 g of a 10% aqueous solution of imidazolin-2-yl) propane] dihydrochloride (0.04% based on the monomer) was added to initiate polymerization. 8 hours after the start, the initiator solution was added to 1.
An additional 3 g was added and polymerization was carried out for 8 hours. The obtained dispersion has a swelling monomer concentration of 20.0% and a polymer particle size of 10 μm or less, and this sample is designated as prototype-9. In the observation after 3 months, no precipitation of inorganic substances was observed and it was stable. The composition is shown in Table 1 and the polymerization result is shown in Table 2.

(Synthesis Example 10) A five-necked separable flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube was used.
Bentonite 66.7 was prepared by adding 155.8 g of 50% acrylamide aqueous solution and 15.6 g of 60% acrylic acid aqueous solution, and swelling them with 30% dispersion liquid overnight with mild stirring.
g (20% by weight of monomer), acrylamide 2-methylpropanesulfonic acid polymer (20% aqueous solution, molecular weight 80)
10%, 50% neutralized product) 25.0 g (5.0% of monomer),
Deionized water 100.7 g, ammonium sulfate 115.
0 g, and 15.6 g of 80% aqueous solution of acryloyloxyethyltrimethylammonium chloride were charged and completely dissolved. The internal temperature was maintained at 33 to 35 ° C., and after substituting with nitrogen for 30 minutes, 2,2′-azobis [2- (5
-Methyl-2-imidazolin-2-yl) propane] 1% aqueous solution of dihydrochloride 4.4 g (vs. unit vs. 0.03)
5%) was added to initiate polymerization. After 8 hours from the start, 2.2 g of the above initiator solution was added, and polymerization was further performed for 10 hours. The resulting dispersion had a loading content to concentration of 20%, a polymer particle size in the range of 2 to 20 μm, and a viscosity of the dispersion of 520 mPa · s. The molar ratio of the monomers is acryloyloxyethyltrimethylammonium chloride / acrylic acid / acrylamide = 5/10/85
Is. This sample is referred to as prototype-10. In the observation after 3 months, no precipitation of inorganic substances was observed and it was stable. The composition is shown in Table 1 and the polymerization result is shown in Table 2.

(Comparative Synthesis Example 1) Deionized water: 140.0 g, 60% acrylic acid: 50.0 g, 50 in a 4-neck 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube. % Acrylamide: 140.
3g was added, and further 135.4 g of ammonium sulfate, and 25.0 g of a 20% by weight aqueous solution of an acrylamido 2-methylpropanesulfonic acid polymer (molecular weight: 200,000, 20 equivalent% neutralized product) (5.0% by weight of monomer). %) Was added.
Then, while stirring, nitrogen is introduced from the nitrogen introducing pipe to remove dissolved oxygen. During this time, the internal temperature is adjusted to 25 ° C. in a constant temperature water bath. After 30 minutes of introducing nitrogen, 2.5 g of 0.2 mass% ammonium peroxodisulfate and 0.2 mass% aqueous solution of ammonium hydrogen sulfite were added in this order.
(To monomer, 40 ppm) was added to initiate polymerization. After 2 hours from the addition of the initiator, the viscosity of the reaction solution slightly increased but did not increase further, and 8 hours after the start of the polymerization, the same amount of each of the above initiators was added, and the polymerization was continued for further 15 hours to carry out the reaction. finished. This prototype is referred to as Comparison-1. The acrylic acid / acrylamide molar ratio of this Comparative-1 was 30/70, and the viscosity was 400 mPa · s. As a result of microscopic observation, it was found that the particles were 2 to 20 μm. The composition is shown in Table 1 and the polymerization result is shown in Table 2.

COMPARATIVE SYNTHESIS EXAMPLE 2 A five-necked separable flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube was charged with 155.8 g of 50% acrylamide aqueous solution and 15.6 g of 60% acrylic acid aqueous solution. 25.0 g of acrylamide 2-methylpropane sulfonic acid polymer (20% aqueous solution, molecular weight 800,000, 50% neutralized product) (to 5.0% of monomer), ion-exchanged water 167.4 g, Ammonium sulfate 115.0 g, and acryloyloxyethyl trimethyl ammonium chloride, 80% aqueous solution 15.6
g was charged and completely dissolved. After maintaining the internal temperature at 33 to 35 ° C. and substituting with nitrogen for 30 minutes, 1% of 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride was used as an initiator. Aqueous solution 4.4g
Polymerization was initiated by adding (0.035% to the amount of monomer). After 8 hours from the start, 2.2 g of the above initiator solution was added and further 1
Polymerization was performed for 0 hours. The resulting dispersion had a loading content to concentration of 20%, a polymer particle size in the range of 2 to 20 μm, and a viscosity of the dispersion of 420 mPa · s. The molar ratio of the monomers is acryloyloxyethyltrimethylammonium chloride / acrylic acid / acrylamide = 5.
/ 10/85. This sample is designated as Comparative-2. The composition is shown in Table 1 and the polymerization result is shown in Table 2.

[0041]

[Table 1] AAC: acrylic acid, IA: itaconic acid, AMS: acrylamido-2-methylpropanesulfonic acid, AAM: acrylamide, DMQ: acryloyloxyethyltrimethylammonium chloride a) bentonite, b) kaolin, c) talc.

[0042]

[Table 2] Dispersion viscosity: mPa · s,

[0043]

Embodiments 1 to 10 Cardboard waste paper was disintegrated with a pulper and then beaten with a Niagara type beater to produce Canadian Standard Freeness C.I. F. S was adjusted to 400 ml. A liquid band of 2% was added to this dispersion to adjust the pH to 4.9. Then, a commercially available paper strengthening agent (Polystron 1
No. 17, manufactured by Arakawa Chemical Co., Ltd.) was added to the pulp in an amount of 0.3%, and the mixture was stirred and uniformly mixed. The pulp slurry obtained was diluted to 0.5%, the pH of the paper was measured, and then 1 L was put in a tapstander sheet machine (1/16 m2) to obtain a dry basis weight of 80 g.
/ M2 paper was made. 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 three times of cut tyrol. This was designated as layer A. Similarly, paper with a dry basis weight of 80 g / m2 was made, and the wet paper was put together with the wire on a direct balance, and the trial productions 1 to 1 produced in each synthesis example were carried out.
A dispersion liquid obtained by diluting 10 to a predetermined dilution concentration shown in Table 3 was spray-applied 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 is returned to the sheet machine together with the wire, and the sheet machine is filled with water and the water filled to the bottom of the wire is drained for decompression dehydration, a new filter paper is put on, and the cootrol is applied three times. It was transferred to a filter paper. Insert the transferred wet paper between two pieces of filter paper and apply 5 kg at a pressure of 3 kg / m2.
After pressing for a minute, it was dried with a rotary dryer to obtain a laminated paper. After humidity control of the obtained laminated paper, JT
APPI paper pulp test method NO. 19-77, T
The character peeling strength (gf / 5 cm) was measured. The results are shown in Table 3.

[0045]

Comparative Examples 1 to 3 Comparative Examples 1 to 2 were tested in the same manner as in Examples 1 to 10. A test in which a dispersion liquid of potato starch (Comparative-3) was sprayed was also conducted at the same time. The results are shown in Table 3.

[0046]

Examples 11 to 20 Using the same paper making operation as in Examples 1 to 10, tests were conducted using waste newspaper. After 3% of liquid band was added to adjust the pH to 4.8, 0.15% of a commercially available paper-strengthening agent (Polystron 117, manufactured by Arakawa Chemical Co., Ltd.) was added to pulp and stirred to uniformly mix them. After that, paper making is carried out in the same procedure as in Examples 1 to 10, and drying,
Paper quality was measured. The results are shown in Table 4.

[0047]

Comparative Examples 4 to 6 Comparative Examples 1 to 2 were tested in the same manner as in Examples 11 to 20. A test in which a dispersion of potato starch was sprayed was also conducted at the same time.
The results are shown in Table 4.

[0048]

[Examples 21 to 30] Waste cardboard paper was disintegrated with a pulper and then beaten with a Niagara type beater to produce Canadian standard dullness C.I. F. S was adjusted to 400 ml. The pH of the dispersion was adjusted to 7.1 with a 10% aqueous solution of sodium carbonate. Then, 0.2% of a commercially available amphoteric strength enhancer HYMOLOCK KL-127 (made by HYMO) was added to the pulp, and the mixture was stirred and uniformly mixed. The pulp slurry obtained was diluted to 0.5% and the papermaking pH was measured. Then, the tapstander sheet machine (1/16 m2) was used.
1 L was put in to prepare paper having a dry basis weight of 80 g / m 2. After that, paper making was carried out by the same operation as in Examples 1 to 10, followed by drying and measurement. The results are shown in Table 5.

[0049]

[Comparative Examples 7 to 9] By the same operation as in Examples 11 to 20, tests were conducted using Comparative-1 and Comparative-2. A test in which a dispersion of potato starch was sprayed was also conducted at the same time.
The results are shown in Table 5.

[0050]

[Table 3] Coating density: mass%, coating amount: G / m2 T-shaped peel strength: (gf / 5 cm)

[0051]

[Table 4]

[0052]

[Table 5]

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08F 20/58 C08F 20/58 22/02 22/02 26/04 26/04 D21H 27/00 D21H 27/00 EF term (reference) 4J011 JA03 JA06 JB08 JB26 PA07 PA13 PA29 PB08 PB22 PB39 PB40 PC02 4J100 AG04Q AJ02P AJ08P AK03P AK08P AL03Q AL08R AL09Q AM02Q AM15Q AM19Q AM21P AM21Q AN01Q AN14R AQ08Q BA02Q BA03R BA32R BA56P BC43Q CA01 CA04 CA05 EA06 FA02 FA21 JA13 4L055 AA11 AC09 AG18 AG27 AG71 AH50 AJ01 BD10 BD16 EA16 EA30 EA32 FA13

Claims (8)

[Claims] 1. A method for producing a laminated paper having two or more layers, comprising the steps of forming a wet paper layer after forming a paper layer, pressing the paper, and then drying the paper, in a salt solution in the presence of inorganic particles. 100 μm obtained by dispersing and polymerizing an ionic water-soluble monomer and a nonionic monomer copolymerizable therewith with a polymer dispersant soluble in the salt aqueous solution under stirring.
An interlayer strength improver comprising the following dispersion liquid of inorganic particle-containing ionic polymer particles. 2. The inorganic particle-containing ionic polymer is composed of 2 to 100 mol% of a monomer represented by the following general formula (1) and 0 to 98 mol% of a copolymerizable nonionic monomer. The interlayer strength improver according to claim 1, which is characterized in that. [Chemical 1] General formula (1) R1 is hydrogen, a methyl group or a carboxymethyl group, A is SO3, C6H4SO3, CONHC (CH3) 2CH
2SO3, C6H4COO or COO, R2 is hydrogen or COOY2, Y1 or Y2 is hydrogen or cation 3. The inorganic particle-containing ionic polymer, wherein the monomer of the following general formula (2) and / or (3) is 2 to 70 mol%, and the monomer of the general formula (1) is 0 to 70. The interlayer strength improver according to claim 1, wherein the interlayer strength improver is composed of 10% to 98% by mol of the copolymerizable nonionic monomer. [Chemical 2] Formula (2) R3 is hydrogen or a methyl group, R4 and R5 are alkyl or alkoxyl groups having 1 to 3 carbon atoms, R6 is hydrogen, an alkyl group having 1 to 3 carbon atoms, an alkoxyl group, or a benzyl group. May be different, A is oxygen or N
H and B represent an alkylene group having 2 to 4 carbon atoms or an alkoxylene group, and X1 represents an anion. [Chemical 3] Formula (3) R7 represents hydrogen or a methyl group, R8 and R9 represent an alkyl group having 1 to 3 carbon atoms, an alkoxy group or a benzyl group, and X3 represents an anion. 4. The interlayer strength improver according to claim 1, wherein the inorganic particles are one or more selected from bentonite, kaolin, white carbon and talc. 5. The monomer of the general formula (1) is (meth)
The interlayer strength improver according to claim 1, which is one or more selected from acrylic acid, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, and salts thereof. 6. The interlayer strength improver according to claim 1, wherein the polymer dispersant soluble in the salt aqueous solution is an ionic polymer. 7. The interlaminar strength improver according to claim 1, wherein the salt constituting the aqueous salt solution is a divalent anion salt. 8. The inorganic particles according to claim 1, which is a method for producing a laminated paper having two or more layers, which comprises a step of forming a wet paper layer after forming the paper layer, pressing the paper, and then drying the paper. A method for improving interlayer strength, which comprises using the contained ionic polymer as an interlayer strength improver.