JP2002294593A - Method for strengthening paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide both a readily handleable paper strengthening agent having quick solubility and a method for strengthening the paper using the same agent. SOLUTION: This method for strengthening the paper is characterized by dissolving a dispersion produced by the coexistence of a cationic polymer dispersing agent in an amount of 0.5-3.0 times based on ionic equivalent of an anionic water-soluble polymer in water, producing a polyionic complex and then adding the resultant polyionic complex into a papermaking raw material before forming into the sheet of paper when a monomer mixture comprising 5-30 mol% of an anionic monomer represented by the following general formula (1) (R1 is hydrogen, methyl group or carboxymethyl group; R2 is hydrogen or carboxy group; A is SO3 , C6 H4 SO3 , CONHC(CH3 )2 CH2 SO3 or COO; and Y is hydrogen or a cation), 70-95 mol% of (meth)acrylamide and 0-20 mol% of other copolymerizable nonionic monomers is polymerized in the coexistence of the dispersing agent composed of a cationic polymer in an aqueous solution of a salt according to a dispersion polymerization method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper-strengthening method, and more particularly, to a method for preparing a mixture of an anionic monomer and a nonionic monomer in the presence of a cationic water-soluble polymer. The present invention relates to a method for enhancing paper strength, comprising dissolving a polymer dispersion liquid produced by medium dispersion polymerization in water to form an ion complex, and then adding it to a papermaking raw material before papermaking.

[0002]

2. Description of the Related Art Paper strength enhancers are usually used in both anionic and amphoteric forms. Among these, the amphoteric paper strength enhancer is generally a copolymer of acrylamide and N, N-dialkylamino (meth) acrylate or N, N-dialkylamino (meth) acrylamide and (meth) acrylic acid. Has been used for Further, as a crosslinking agent, N, N-methylenebisacrylamide or the like (JP-A-63
-50597)), and more recently,
Paper strength enhancers comprising a polymer in which N, N-dimethylacrylamide is copolymerized and exhibiting specific solution properties have been developed (JP-A-5-140893, JP-A-5-287).
693, JP-A-5-272092 or JP-A-7-97790.

[0003] On the other hand, paper strength enhancers that utilize "intermolecular amphoteric" are also being studied. This applies the same action as an amphoteric polymer by an ionic interaction between an anionic polymer and a cationic polymer, and a stronger interaction than an intramolecular amphoteric polymer can be expected. For example, JP-A-7-9079
No. 7, JP-A-10-131086, and JP-A-10-131085 disclose the prescription.

On the other hand, various methods have been disclosed for producing a dispersion composed of a cationic water-soluble polymer by coexisting an ionic polymer dispersant in an aqueous salt solution. For example, Japanese Patent Publication No. 2-38131 discloses that a cationic polymer that is soluble in an aqueous salt solution is used as a dispersant when producing a dispersion in which a monomer is soluble in an aqueous salt solution and a polymer obtained by polymerization is insoluble. Discloses a method for coexisting with the above. In addition,
Japanese Patent No. 39481 discloses a method for producing a dispersion composed of an anionic or cationic water-soluble polymer in the presence of a polyvalent compound such as ethylene glycol, propylene glycol, glycerin or polyethylene glycol. . Japanese Patent Application Laid-Open No. 10-212320 discloses a method for producing an anionic water-soluble polymer dispersion in an aqueous salt solution. The amount of the cationic polymer coexisting during the polymerization is 1 to 10% by weight relative to the monomer.

[0005] As for the paper strength enhancer, it is necessary to dissolve it promptly in order to be added to the papermaking raw material, so that the solution type is mainly used. However, since the intramolecular or intermolecular amphoteric polymer is a solution type, the concentration is increased from 15% to 20%. Highly concentrated solution-type paper-strengthening agents are also being studied, but the effect-related molecular weight-apparent viscosity relationship has not yet been overcome. Although a high-concentration dispersion can be expected as a dispersion, a polymer-dispersion-type paper-strengthening agent has not yet appeared on the market, and its formulation has not yet been disclosed.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to develop a formulation of a paper-strengthening agent of polymer fine particle dispersion type which can be expected to have a high concentration.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the following inventions have been reached. That is, the invention of claim 1 is characterized in that 5 to 30 mol% of an anionic monomer represented by the following general formula (1),
A monomer mixture comprising 70 to 95 mol% of acrylamide and 0 to 20 mol% of another copolymerizable nonionic monomer is dispersed in a salt aqueous solution by a cationic polymer soluble in the salt aqueous solution. When polymerizing an anionic water-soluble polymer composed of polymer fine particles by a dispersion polymerization method in the presence of an agent, the dispersant composed of the cationic polymer is added in an amount of 0.5 to 0.5 to the anionic equivalent of the anionic water-soluble high component. A paper strengthening method characterized by dissolving a dispersion prepared by coexisting 3.0 times in water to form a polyion complex, and then adding it to papermaking raw materials before papermaking.

Embedded image R1 is hydrogen, methyl or carboxymethyl, R2
Is hydrogen or carboxyl group, A is SO3, C6H4S
O3, CONHC (CH3) 2CH2SO3 or C
OO and Y are hydrogen or cation

[0008] The invention of claim 2 is the paper-strengthening method according to claim 1, wherein the dispersant comprising the cationic polymer is a Hoffman reactant of polyacrylamide.

A third aspect of the present invention is the method for enhancing paper strength according to the first aspect, wherein the dispersant comprising the cationic polymer is a vinylamine-based polymer.

According to a fourth aspect of the present invention, the dispersant comprising the cationic polymer is a copolymer of a vinyl-based cationic monomer and acrylamide. Is the way.

[0011] The invention according to claim 5 is that the cation equivalent of the dispersant comprising the cationic polymer soluble in the salt aqueous solution is as follows:
The paper strength increasing method according to any one of claims 1 to 4, wherein the paper strength is 3.0 to 10.0 meq / g.

[0012] The invention of claim 6 is that the dispersant comprising a cationic polymer soluble in the aqueous salt solution has a weight average molecular weight of:
The amount is from 100,000 to 3,000,000.
2. The paper strength enhancing method according to 1.

The invention according to claim 7 is the paper-strengthening method according to claim 1, wherein the anionic water-soluble polymer has a weight average molecular weight of 1,000,000 to 5,000,000.

The invention according to claim 8 is the method for producing an anionic water-soluble polymer dispersion according to claim 1, wherein the salt constituting the aqueous salt solution contains at least one kind of polyvalent anion salt. It is.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer dispersion used in the paper strength enhancing method of the present invention comprises 5 to 30 mol% of an anionic monomer represented by the above general formula (1) and 70 to 95 (meth) acrylamide. A monomer mixture consisting of 0 mol% and 0 to 20 mol% of other copolymerizable nonionic monomers is prepared in a salt aqueous solution in the presence of a dispersant comprising a cationic polymer soluble in the salt aqueous solution. An anionic water-soluble polymer composed of polymer fine particles is polymerized by a dispersion polymerization method. The dispersant comprising the cationic polymer is produced by coexistence in an amount of 0.5 to 3.0 times the ion equivalent of the anionic water-soluble polymer. The ion equivalent of the dispersant composed of a cationic polymer to be coexisted is
3.0 to 10.0 meq / g, preferably 4.0 meq / g.
Ｍｅ10.0 meq / g. If this is expressed in terms of mol% of the cationic group in the cationic polymer, it is expressed as about 25 mol% in the case of Hofmann reactant hydrochloride of polyacrylide or hydrolyzate of N-vinylformamide polymer hydrochloride. ~ 80 mol%, preferably about 30 mol% ~
About 80 mol%. In the case of dimethylaminoethyl methacrylate sulfate / acrylamide copolymer, the amount is about 30 mol% or more, preferably about 50 mol% or more. Or dimethyldiallylammonium chloride /
About 30 mol% or more in the case of acrylamide copolymer,
Preferably, it is at least about 40 mol%.

The weight ratio between the monomer and the cationic polymer is as follows. In the case of acrylic acid / acrylamide = 12/88 (mol%), if Hofmann reaction hydrochloride of polyacrylide or hydrolyzate of N-vinylformamide polymer hydrochloride and a degree of cationization of 60 mol% are used, ion When the cationic polymer is added so that the equivalent ratio becomes 0.5 to 3.0, the weight ratio becomes monomer: cationic polymer = 1: 0.2 to 1: 1.2.

The cationic polymer used in the present invention serves as a dispersant during polymerization, and dissolves the dispersion liquid after the production in water, and adds an anion to the papermaking raw material before papermaking to enhance the paper strength. It also functions as a yield improver that forms a polyion complex with the water-soluble polymer.
Therefore, it is preferable that the amount is larger than the ion equivalent of the anionic water-soluble polymer. Usually, 0.5 to 3.0 times coexist, but preferably 1.0 to 2.0 times.

Specific examples of the cationic polymer used in the present invention include, in addition to the above-mentioned polyacrylide-Hoffmann reactant or N-vinylformamide polymer acid hydrolyzate, dimethylamino (meth) acrylate ethyl,
Examples thereof include diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide or a quaternary compound thereof, or a copolymer of acrylamide with dimethyldiallylammonium chloride. In general, a primary amino group-containing cationic polymer has a high aggregating effect, so that when a Hoffman reactant of polyacrylide or N-vinylformamide polymer acid hydrolysis is used as a dispersant, the drainage of papermaking raw materials increases. preferable. However, when the papermaking pH rises to 6.5 to 8 or the like, the dissociation of these cationic polymers decreases, and the drainage does not increase. In such a case, a cationic polymer obtained by copolymerizing an acrylic or diallylammonium salt monomer containing a tertiary or quaternary ammonium base is used.

Examples of the anionic monomer copolymerized with (meth) acrylamide include acrylic acid, methacrylic acid, itaconic acid, maleic acid, vinylsulfonic acid, vinylbenzenesulfonic acid or 2-acrylamide 2-methylpropanesulfone. Acids and the like.

Further, the paper strength enhancer comprising this polymer dispersion can be copolymerized with other nonionic monomers.
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 the like.

The copolymerization molar ratio of the monomers used in the polymerization is 5 to 30 mol% of anionic monomer, 70 to 95 mol% of acrylamide, and 0 to 0 of other copolymerizable nonionic monomers. 20 mol%, preferably 78 to 95 mol% of anionic monomer, 78 to 95 mol% of acrylamide and 0 to 10 mol% of other copolymerizable nonionic monomer.

The weight average molecular weight of the cationic polymer used as a dispersant is from 100,000 to 3,000,000, preferably from 500,000 to 3,000,000. As described above, since the cationic polymer plays the role of a dispersant and a retention aid, the higher the molecular weight is, the better the drainage is. However, if the molecular weight is too high, the formation is affected, which is not preferable. Further, the function as a dispersant tends to decrease even if the molecular weight is too high, and falls within the above range. The weight-average molecular weight of one anionic water-soluble polymer is 1,000,000 to 5,000,000, preferably 2,000,000 to 3,000,000. Usually, the molecular weight of a commercially available amphoteric paper strength enhancer is about 2,000,000 to 5,000,000, but in the case of the present invention, since a polyion complex is formed with a cationic polymer, the apparent molecular weight increases and the original molecular weight increases. It is preferable that the molecular weight of the polymer is not too high, and it is within the above range.

The polymerization concentration is in the range of about 20 to 40% by weight, preferably 20 to 30% by weight. However, the polymerization concentration referred to here also means a concentration when the supply of all the monomers is completed by adopting a method of dividing and adding the monomers. The higher the polymerization concentration, the better the productivity and the transportability. However, if the polymerization concentration is too high, a stable dispersion cannot be obtained, and the polymerization is in the above range. The monomer concentration at the start is 15 to 25%, and it is also possible to adopt a method in which the monomer is additionally supplied to increase the concentration to finally reach 20 to 40% by weight.

Usually, the polymerization conditions are appropriately determined depending on the monomers used and the molar ratio of copolymerization.
The reaction is carried out at a temperature of 0 ° C, preferably at 20 to 80 ° C. 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 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, etc., which are 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] 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 of these initiators are redox initiators,
It is a combination of ammonium peroxodisulfate or potassium peroxodisulfate with sodium sulfite or sodium bisulfite.

Further, polyfunctional monomers such as N, N-methylenebisacrylamide and ethylene glycol (meth) acrylate, or N, N-dimethyl (meth) acrylamide and N, N-diethyl (meth) ) It is also possible to synthesize and modify a crosslinked or branched polymer by copolymerizing a thermally crosslinkable monomer such as acrylamide.

As the inorganic salt constituting the aqueous salt solution, a polyvalent anion salt such as a sulfate or a phosphate is preferable to a monovalent anion salt such as an alkali metal halide. Examples of the salt used include ammonium sulfate, sodium sulfate, potassium sulfate, sodium monohydrogen phosphate, sodium dihydrogen phosphate and the like. Further, a monovalent anion salt such as the alkali metal halide exhibits an effect when used in combination with a polyvalent anion salt. The concentration of these inorganic salts in the polymerization system ranges from 5% by weight to the saturation concentration.

The method for adding the polymer dispersion of the present invention is as follows. First, dissolve the dispersion in water,
Then, it is added to the papermaking raw material before papermaking. Wet end machine chests and seed boxes are assumed as addition locations.
The addition amount is 0.05 to 2%, preferably 0.1
~ 0.5%. The raw materials for papermaking include raw materials for high-quality paper or paperboard, and the type of pulp is chemical pulp, mechanical pulp, or used paper.

[0029]

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

Synthesis Example 1 Deionized water: 85.0 g, sodium chloride 9 in a four-necked 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube.
0.0g, 60% acrylic acid: 25.3g, 50% acrylamide 220.1g was added to make a uniform mixed solution,
75.0 g (0.7 times the ion equivalent of acrylic acid) of a 25% aqueous solution of poly-N-vinylformamide hydrochloride hydrochloride (weight average molecular weight: 680,000, ion equivalent: 7.88 meq / g) as a dispersant; 10 as polymerization degree regulator
% Isopropyl alcohol 0.75 g (based on monomer 0.0
5% by weight) and completely dissolved. The solution pH at this time was 3.05. Thereafter, nitrogen is introduced from a nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ± 2 ° C. using a thermostatic water bath. 30 minutes after nitrogen introduction, 2.5 g of a 1% aqueous solution of 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dichloride (based on monomer, 200 ppm)
It was added to start polymerization. Eight hours after the start of the polymerization, 0.6 g of the initiator was added, and the polymerization was continued for another 15 hours to complete the reaction. This prototype is referred to as prototype-1. The composition of Prototype-1 is such that the concentration per unit is 25%, acrylic acid / acrylamide = 12/88 (mol%),
The dispersion viscosity was 1630 mPa · s. Molecular weight measuring device by static light scattering method (DLS-7000 manufactured by Otsuka Electronics)
And the weight average molecular weight was measured. Table 1 shows the results.

(Synthesis Example 2) By the same operation as in Example 1, the poly (N-vinylformamide) hydrochloride hydrolyzate of Example 1 was used, and 1.
An anionic water-soluble dispersion was synthesized when added as a 4-fold dispersant. This prototype is referred to as prototype-2. The composition of this trial production-2 was composed of 25% of a monomer per concentration, acrylic acid /
Acrylamide = 12/88 (mol%), and the dispersion viscosity was 1270 mPa · s. Also, the weight average molecular weight was measured in the same manner. Table 1 shows the results.

(Synthesis Example 3) In the same manner as in Example 1, the poly (N-vinylformamide) hydrochloride hydrolyzate of Example 1 was used.
An anionic water-soluble dispersion was synthesized when added as a 0-fold dispersant. This prototype is referred to as prototype-3. The composition of this Prototype-3 is as follows: monomer / concentration: 22%, acrylic acid /
Acrylamide was 12/88 (mol%), and the dispersion viscosity was 1060 mPa · s. Also, the weight average molecular weight was measured in the same manner. Table 1 shows the results.

(Synthesis Example 4) A four-necked 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube was charged with 20.0 g of deionized water, 90.0 g of ammonium sulfate, and 25% of 60% acrylic acid. 0.3 g and 220.1 g of 50% acrylamide were added to form a uniform mixed solution, and a 30% aqueous solution of poly-N, N-dimethylaminoethyl acrylate sulfate (weight average molecular weight: 115
140.0 g (1.4 times the ion equivalent of acrylic acid) and 0.75 g of 10% isopropyl alcohol as a polymerization degree regulator (0.05% by weight of monomer) %) Was added and completely dissolved.
The solution pH at this time was 3.12. Thereafter, nitrogen is introduced from a nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ± 2 ° C. using a thermostatic water bath. 30 minutes after the introduction of nitrogen, 2,2′-azobis [2-
(5-methyl-2-imidazolin-2-yl) propane] 2.5 g of a 1% aqueous solution of hydride dichloride (based on monomer,
(200 ppm) was added to initiate polymerization. 8 after initiation of polymerization
After a lapse of time, 0.6 g of the initiator was added, and the polymerization was continued for another 15 hours to complete the reaction. This prototype is referred to as prototype-4. The composition of Prototype-4 was such that the concentration per unit was 25%, acrylic acid / acrylamide = 12/88 (mol%), and the viscosity of the dispersion was 985 mPa · s. Similarly, the weight average molecular weight was measured. Table 1 shows the results.

Synthesis Example 5 90.0 g of sodium chloride, 25.3 g of 60% acrylic acid, 25.3 g of 50% acrylamide 220 were placed in a four-necked 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube. 0.1 g was added to make a uniform mixed solution, and a 20% aqueous solution of polyacrylamide as a dispersant was used as a Hoffman reaction product of polyacrylamide (weight average molecular weight: 14.5 million, ion equivalent: 9.10 meq / g) 162.7
g (1.4 times the ion equivalent of acrylic acid) and 10% isopropyl alcohol 0.75 as a polymerization degree regulator.
g (based on 0.05% by weight of monomer) was added and completely dissolved. The solution pH at this time was 3.01. Thereafter, nitrogen is introduced from a nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ± 2 ° C. using a thermostatic water bath. 30 minutes after nitrogen introduction, 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl)
Propane] 2.5 g of a 1% aqueous solution of hydrogen dichloride (based on monomer, 200 ppm) was added to initiate polymerization. Eight hours after the start of the polymerization, 0.6 g of the initiator was added, and the polymerization was continued for another 15 hours to complete the reaction. This prototype is referred to as prototype-5. The composition of this prototype -5 is as follows: monomer / concentration 25%, acrylic acid / acrylamide = 12 /
88 (mol%) and the viscosity of the dispersion is 2170 mPa
-It was s. Similarly, the weight average molecular weight was measured. Table 1 shows the results.

Synthesis Example 6 Deionized water: 44.3 g, sodium chloride 9 in a four-necked 500 ml separable flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube.
0.0g, 60% acrylic acid: 25.3 g, 509.4% acrylamide 179.4 g, and 2-hydroxyethyl methacrylate 21.1 g were added to form a uniform mixed solution, and a 25% aqueous solution of poly-N- as a dispersant was added. 137.5 g (1.4 times the ion equivalent of acrylic acid) of hydrochloric acid hydrolyzate of vinyl formamide (weight average molecular weight: 680,000, ion equivalent: 7.88 meq / g) and 10% as a polymerization degree regulator
0.75 g of isopropyl alcohol (0.05 per monomer)
% By weight) and completely dissolved. Solution p at this time
H was 3.05. Thereafter, nitrogen is introduced from a nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ± 2 ° C. using a thermostatic water bath. 30 minutes after the introduction of nitrogen, 2,2′-azobis [2- (5-methyl-
2-imidazolin-2-yl) propane] 2.5 g of a 1% aqueous solution of hydride dichloride (based on monomer, 200 ppm) was added to initiate polymerization. Eight hours after the start of the polymerization, 0.6 g of the initiator was added, and the polymerization was continued for another 15 hours to complete the reaction. This prototype is referred to as prototype-6. The composition of Prototype-6 is such that the concentration per unit is 25%, acrylic acid / acrylamide / 2-hydroxyethyl methacrylate = 12/78/10 (mol%), and the dispersion viscosity is 850 mPa · s. Was. Similarly, the weight average molecular weight was measured. Table 1 shows the results.

(Preparation of Comparative Product) At a monomer concentration of 20% by weight, an anionic water-soluble polymer consisting of acrylic acid / acrylamide = 12/88 (mol%) was polymerized by an aqueous solution polymerization method. When the molecular weight is measured by the same method, 2
430,000. This anionic water-soluble polymer and the cationic water-soluble polymer used as a dispersant in the examples were mixed at an ion equivalent of 0.7 and 1.4, and the pH was adjusted to 3.0 to 3.2. Then, an aqueous solution type paper strength agent comprising 15% of a polymer pure content was prepared. These samples are compared-1 to -5. Table 2 shows the water-soluble polymers used and the mixing ratio.

[0037]

Examples 1 to 6 Papermaking test of a paper strength enhancer comprising the dispersion of the present invention using a raw material for a liner at a papermaking site (SS content 2.54%, pH 5.52, ash content 0.20%) Was done. After making this papermaking raw material a 0.8% concentration, a commercially available emulsion sizing agent was added to pulp at 0.10%, aluminum sulfate (8.0% as Al2 O3 content) to pulp at 1.5%.
Was added to adjust the pH to 5.85, and each of Prototype-1 to Prototype-6 of Synthesis Examples 1 to 6 was diluted with water to obtain a 0.5% polyion complex. The pH of each of the diluents is all 6.5
Adjusted to ~ 7.0. After that, 0.3
%, And the mixture was stirred for 20 seconds. Then, the paper was made using a Tappi standard sheet machine so as to have a basis weight of 100 g / m2.
After pressing the obtained wet paper at 5 kg / cm 2 for 2 minutes,
It was dried with a rotary dryer at 5 ° C. for 3 minutes to obtain a handmade paper. This hand-made paper is subjected to 2 ° C. under the conditions of 20 ° C. and 65% HR.
After humidifying for 4 hours, the specific burst strength was measured according to JIS P8112. The specific compressive strength was measured according to TAPPI JIS P 8126. Table 3 shows the results.

[0038]

Comparative Examples 1 to 5 Tests were conducted on Comparative-1 to Comparative-5 in the same manner as in Examples 1 to 6. Table 3 shows the results.

[0039]

Examples 7 to 12 Papermaking test of a paper-strengthening agent comprising the dispersion of the present invention using a raw material for a liner (SS content 2.54%, pH 5.52, ash content 0.20%) at a papermaking site. Was done. This time, the case where the sulfuric acid band and the emulsion size were not added, and only each of Prototype-1 to Prototype-6 of Synthesis Examples 1 to 6 was added. After diluting to 0.5% to obtain a polyion complex, 0.3% was added, and the mixture was stirred for 20 seconds.
0 g / m <2> papermaking, and the obtained wet paper 5 kg
/ Cm2 for 2 minutes, and dried with a rotary dryer at 105 ° C for 3 minutes to obtain a handmade paper. 20 of this handmade paper
After humidifying for 24 hours at 65 ° C and 65% HR, JI
Specific burst strength according to SP 8112; TAPP
The specific compressive strength was measured according to I JIS P8126. Table 4 shows the results.

[0040]

Comparative Examples 6 to 10 The same operation as in Examples 7 to 12 was carried out to conduct tests on Comparative-1 to Comparative-5. Table 4 shows the results.

[0041]

[Table 1] PVAM: poly-N-vinylformamide hydrochloride hydrolyzate PDMA: poly-N, N-dimethylaminoethyl acrylate sulfate PAMH: polyacrylamide Hoffman reactant hydrochloride AAC: acrylic acid, AAM: acrylamide, HEMA: 2-hydroxyethyl methacrylate dispersion viscosity: mPa · s, molecular weight: 10,000

[0042]

[Table 2] PVAM: Poly-N-vinylformamide hydrochloride hydrolyzate PDMA: Poly-N, N-dimethylaminoethyl acrylate sulfate PAMH: Polyacrylamide Hoffman reactant hydrochloride Equivalent ratio: (cationic polymer ion equivalent) / (Anionic polymer ion equivalent) Viscosity of mixed solution (15% concentration): mPa · s

[0043]

[Table 3] Specific burst degree: dimensionless Specific ring crush: dimensionless

[0044]

[Table 4] Specific burst degree: dimensionless Specific ring crush: dimensionless

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J011 AA05 JA06 JB26 4J100 AB07Q AG04R AJ02Q AJ08Q AJ09Q AL03R AL09R AM02R AM15P AM15R AM19R AM21Q AM21R AN04R AP01Q AQ08R BA13R BA14R BA56Q CA04 FA05 AG01 A06 AG06 BD10 EA29 EA30 EA32 FA13 FA30 GA06

Claims (8)

[Claims] 1. An anionic monomer represented by the following general formula (1): 5 to 30 mol%, (meth) acrylamide 70
~ 95 mol% and other copolymerizable nonionic monomers 0
An anionic water-soluble polymer composed of polymer fine particles is dispersed in a salt aqueous solution by a dispersion polymerization method in the presence of a dispersant composed of a cationic polymer soluble in the salt aqueous solution. In the case of polymerization, a dispersion prepared by coexisting a dispersant composed of the cationic polymer with 0.5 to 3.0 times the ion equivalent of the anionic water-soluble polymer is dissolved in water to obtain a polyion complex. And then adding it to the papermaking raw material before papermaking. Embedded image R1 is hydrogen, methyl or carboxymethyl, R2
Is hydrogen or carboxyl group, A is SO3, C6H4S
O3, CONHC (CH3) 2CH2SO3 or C
OO and Y are hydrogen or cation 2. The method according to claim 1, wherein the dispersant comprising the cationic polymer is a Hoffman reactant of polyacrylamide. 3. The paper-strengthening method according to claim 1, wherein the dispersant comprising the cationic polymer is a vinylamine-based polymer. 4. The paper strength enhancing method according to claim 1, wherein the dispersant comprising the cationic polymer is a copolymer of a vinyl cationic monomer and acrylamide. 5. The dispersant comprising a cationic polymer soluble in an aqueous salt solution has a cation equivalent of 3.0 to 10.0 m.
The paper strength enhancing method according to any one of claims 1 to 4, wherein the value is eq / g. 6. The paper-strengthening method according to claim 1, wherein the weight average molecular weight of the dispersant comprising the cationic polymer soluble in the aqueous salt solution is 100,000 to 3,000,000. . 7. The method according to claim 1, wherein the weight average molecular weight of the anionic water-soluble polymer is 1,000,000 to 5,000,000. 8. The method for producing an anionic water-soluble polymer dispersion according to claim 1, wherein the salt constituting the salt aqueous solution contains at least one kind of polyvalent anion salt.