JP2005248384A - Method for producing paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing paper, capable of maintaining a high yield based on a paper-making raw material and a high value of durability of the produced paper, even when the paper is made by using a paper-making raw material in which a mixed ratio of mechanical pulp or waste paper is increased, and further capable of bringing about a remarkable effect, even in an acidic paper-making system in which aluminum sulfate especially exists. <P>SOLUTION: This method for producing the paper comprises adding an anionic water-soluble polymer to the paper-making raw material in which an amphoteric paper strengthening agent is contained and which is in a state prior to paper making, for the purpose of increasing the durability of the paper. The remarkable effect is brought about by making the anionic water-soluble polymer contain sulfonic acid groups. The method brings about the remarkable effect in the paper-making system in which the paper making is conducted by especially adding the aluminum sulfate thereto. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a papermaking method, and more specifically, an anionic water-soluble polymer is added to a papermaking raw material before papermaking containing an amphoteric paper strength enhancer for the purpose of improving paper strength, and papermaking is characterized. The present invention relates to a paper manufacturing method.

  In recent years, the ratio of waste paper and mechanical pulp as papermaking raw materials has been increasing from the viewpoint of resource saving and environmental consideration. Although chemical pulp has the advantages of having a beautiful appearance and excellent strength and printing suitability, there is a concern about the impact on the environment because it uses a large amount of chemicals. In that respect, mechanical pulp has the advantage that the amount of chemical used is relatively small and the yield relative to the raw material is high. However, a large amount of resin contained in the raw material wood and anionic substances generated during pulping remain in the pulp dispersion. In addition, the used paper is also mixed with the coating agent used during surface processing, which causes pitch trouble due to agglomerates of water-insoluble fine particles during papermaking. In addition, adhesives and gums caused by coating agents used in leaflets and paperboard in used paper also have a great influence on papermaking. Therefore, even if an amphoteric paper strength enhancer that is currently used generally is added, the effect is hardly exhibited.

  An anionic polyacrylamide was initially used as a synthetic paper strength enhancer, but it was replaced by amphoteric polyacrylamide to improve performance depending on the papermaking raw materials as described above. Has come to occupy. However, as the blending ratio of waste paper and mechanical pulp increases, the effect expression tends to decrease, and there is a demand for a prescription for improving the effect. It is conceivable to add a cationic polymer afterwards to promote the fixing of the amphoteric polyacrylamide paper strength enhancer. However, a relatively large amount of the amphoteric polyacrylamide paper strength enhancer is already present in the papermaking system. In this situation, the effect cannot be expected, and as a result, the paper strength value cannot be improved. Formulations combining a cationic polymer and an anionic polymer for the purpose of improving paper strength are known. For example, Patent Document 1 combines a polyvinylamine polymer, which is a cationic polymer, with an anionic polyacrylamide, and performs papermaking while maintaining a low cation requirement in papermaking system (abundance of soluble anionic substances in papermaking system). It is an object. However, this method is not necessarily an efficient formulation such as using an expensive polyvinylamine polymer and using an anionic polyacrylamide paper strength enhancer.

JP-A-11-140787

  An object of the present invention is to provide a paper manufacturing method capable of maintaining a high papermaking raw material yield ratio and high strength of papermaking even when papermaking is performed using a papermaking raw material having an increased blending ratio of mechanical pulp and waste paper. . It is another object of the present invention to provide a method for producing paper that exhibits a remarkable effect even in acidic papermaking in which a sulfate band is present.

  As a result of intensive studies to solve the above problems, the following inventions have been achieved. That is, the invention according to claim 1 is a paper manufacturing method characterized in that an anionic water-soluble polymer is added to a papermaking raw material before papermaking containing an amphoteric paper strength enhancer for the purpose of improving paper strength. About.

The invention according to claim 2 is characterized in that the anionic water-soluble polymer is one or more anionic monomers in which a sulfonic acid group-containing monomer is essential, and (meth) acrylamide as appropriate and other nonionics that can be copolymerized. A water-soluble monomer mixture containing a water-soluble monomer from a dispersion having a particle diameter of 100 mμ or less produced by a dispersion polymerization method in the presence of a dispersant composed of a polymer soluble in the aqueous salt solution in an aqueous salt solution The paper manufacturing method according to claim 1, wherein:

The invention according to claim 3 is characterized in that the anionic water-soluble polymer is one or more anionic monomers in which a sulfonic acid group-containing monomer is essential, and (meth) acrylamide as appropriate and other nonionics capable of copolymerization. A water-soluble monomer mixture containing a water-soluble monomer and water, an oil immiscible oil comprising at least one hydrocarbon and an amount effective to form a water-in-oil emulsion and at least an HLB 2. A water-in-oil polymer emulsion produced by mixing each of one kind of surfactants and forming a water-in-oil emulsion by vigorous stirring to form a polymer, followed by polymerization. The method for producing paper as described in 1. above.

The invention according to claim 4 is characterized in that a monomer having a plurality of vinyl groups coexists in an amount of 0.001 to 0.5 mol% with respect to the water-soluble monomer mixture. This is a paper manufacturing method.

The invention according to claim 5 is the paper manufacturing method according to claim 1, wherein the amphoteric paper strength enhancer has a weight average molecular weight of 500,000 to 5,000,000.

The invention according to claim 6 is the paper manufacturing method according to claim 1, wherein a sulfuric acid band is present in the papermaking raw material and the papermaking pH is 3-7.

The invention according to claim 7 is the paper manufacturing method according to claim 1 or 6, characterized in that the paper is paperboard.

The paper production method of the present invention is characterized in that an anionic water-soluble polymer is added to a papermaking raw material before papermaking containing an amphoteric paper strength enhancer for the purpose of improving paper strength. An anionic water-soluble polymer is added to promote the fixing improvement of the amphoteric polyacrylamide type paper strength enhancer, so that even when a relatively large amount of the amphoteric polyacrylamide type paper strength enhancer is present in the papermaking system, Various types of polymers can be easily adsorbed, and as a result, it is possible to achieve a high yield of papermaking raw material and a high strength of papermaking.

  The anionic water-soluble polymer used in the present invention is a copolymer of a water-soluble monomer such as (meth) acrylic acid or a nonionic water-soluble monomer such as (meth) acrylamide. Is preferably a sulfonic acid group-containing anionic water-soluble polymer such as acrylamide 2-methylpropanesulfonic acid. The reason is that paper using a paper strength enhancer is often a paperboard, and therefore, paper is often made by adding a sulfuric acid band. As a result, the papermaking pH becomes acidic and the carboxyl group is difficult to dissociate, and a sulfonic acid group-containing water-soluble polymer is advantageous.

  The anionic water-soluble polymer can be used in any form of product, but a product obtained by a dispersion polymerization method in a salt solution or a water-in-oil emulsion polymerization method, which has a high solubility in water, is preferable. A product obtained by the dispersion polymerization method in an aqueous salt solution is prepared by neutralizing 10 to 100 mol% of a water-soluble monomer containing an anionic group, and then appropriately mixing with a nonionic monomer or the like in the aqueous salt solution. It is produced by a dispersion polymerization method with stirring in the presence of a dispersant composed of a polymer soluble in an aqueous salt solution. The polymerization conditions are usually appropriately determined according to the monomer used and the copolymerization mol%, and the temperature is 0 to 100 ° C., preferably 20 to 50 ° C. For the initiation of polymerization, a radical polymerization initiator is used.

  Examples of radical polymerization initiators include redox systems such as ammonium and potassium peroxodisulfates and sodium bisulfite, or water-soluble azo initiators such as 2,2-azobisamidinopropane dihydrochloride, 2, 2, -Azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, oil-soluble azobisisobutyronitrile, and peroxides include lauryl peroxide. When an oil-soluble initiator is used, it is once dissolved in a water-miscible solvent and added to the polymerization solution.

Examples of the anionic water-soluble monomer include methacrylic acid, acrylic acid, maleic acid, itaconic acid, and acrylamide 2-methylpropanesulfonic acid. Moreover, the copolymer with another nonionic monomer may be sufficient. For example, nonionic monomers include (meth) acrylamide, N, N-dimethylacrylamide, vinyl acetate, acrylonitrile, methyl acrylate, 2-hydroxyethyl (meth) acrylate, diacetone acrylamide, N-vinyl pyrrolidone, N-vinylformamide, N-vinylacetamide and the like can be mentioned, and one or two or more of these acid monomers or nonionic monomers can be copolymerized. The most preferred combination is acrylamide 2-methylpropanesulfonic acid and acrylamide, and then a polymer obtained by copolymerizing acrylic acid with these. The proportion of these anionic water-soluble monomers in the (co) polymer is 5 to 100 mol%, preferably 10 to 100 mol%.

  The molecular weight of the polymer constituting the dispersion is 1 million to 20 million, but preferably 5 million to 20 million. If it is 1 million or less, the cohesive force is insufficient and the yield rate is lowered, and if it is 20 million or more, the cohesive force is too high and the formation collapses after papermaking. In addition, the solution viscosity becomes too high, dispersibility is deteriorated, and handling of the aqueous solution is also deteriorated.

  When producing a dispersion composed of fine polymer particles used in the present invention, any anionic or cationic polymer can be used as the dispersant, but anionic is more preferred. 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 nonionic monomers include acrylamide, N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, N, N-dimethylacrylamide, acrylonitrile, diacetone acrylamide, 2-hydroxyethyl (meth) acrylate And so on. The anionic monomer is acrylamide 2-methylpropane sulfonic acid, styrene sulfonic acid, (meth) acrylic acid, etc., but the most preferable combination is acrylamide 2-methylpropane sulfonic acid (salt) and methacrylic acid (salt). And a copolymer. In addition, as the cationic polymer, homopolymers such as (meth) acryloyloxyethyltrimethylammonium chloride, dimethyldiallylammonium chloride, (meth) acryloylaminopropyltrimethylammonium chloride, these cationic monomers and the above It is a copolymer with a nonionic monomer. The addition amount with respect to the monomer is 1 to 30% by mass, but preferably 5 to 10%.

  Salts used at the time of polymerization are salts of alkali metal ions such as sodium and potassium, ammonium ions, halide ions, sulfate ions, nitrate ions, phosphate ions, etc., but salts with polyvalent anions. More preferred. The concentration of the salt solution is 5% by weight or more and the saturation concentration or less.

The method for producing a water-in-oil polymer emulsion comprises the step of mixing an anionic monomer or a monomer mixture comprising an anionic monomer and a copolymerizable nonionic monomer with water, at least water. An oily substance composed of immiscible hydrocarbons, an amount effective to form a water-in-oil emulsion and at least one surfactant having HLB were mixed and stirred vigorously to form a water-in-oil emulsion. Then, it synthesize | combines by superposing | polymerizing. The polymerization concentration of the monomer is in the range of 20 to 50% by weight, preferably in the range of 25 to 40% by weight. The concentration and temperature of the polymerization are appropriately determined depending on the monomer composition, the polymerization method, and the selection of the initiator. Set. The polymerization temperature is usually 20 to 80 ° C, preferably 20 to 40 ° C. For initiation of polymerization, the same radical polymerization initiator as in the above-mentioned dispersion polymerization in brine is used. The molecular weight of the anionic water-soluble polymer obtained by polymerizing the monomer is 1,000,000 to 20,000,000, preferably 5,000,000 to 20,000,000, similarly to the dispersion polymerization in brine.

The anionic water-soluble polymer used in the present invention uses an anionic water-soluble cross-linked copolymer obtained by copolymerizing an anionic monomer as an essential component in the presence of a monomer having a plurality of vinyl groups. You can also. In other words, the yield improver in papermaking has been pursued to improve the cohesive strength in order to cope with the increase in papermaking speed and the increase in impurities in the papermaking raw material, so the viewpoint of application of crosslinkable polymers is considered. I did not come. The crosslinkable water-soluble polymer has a relatively small molecular spread in water as compared with a linear polymer, so that the cohesive force is suppressed and is suitable as a process chemical in the paper industry. Examples of the monomer having a plurality of vinyl groups used for such a purpose include methylenebisacrylamide and ethylene glycol di (meth) acrylate. As a compounding ratio in a water-soluble monomer mixture, it is 0.001-0.1 mol%, Preferably it is 0.001-0.05 mol%.

  The amphoteric paper strength enhancer used in the present invention comprises an amphoteric water-soluble polymer obtained by copolymerizing a cationic monomer, an anionic monomer and a nonionic monomer. The copolymerization ratio of the cationic monomer is 1 to 30 mol%, preferably 2 to 20 mol%, and the copolymerization ratio of the anionic monomer is 1 to 50 mol%, preferably 2 to 30 mol%. The copolymerization ratio of the nonionic monomer is 20 to 98 mol%, preferably 50 to 96 mol%. Examples of cationic monomers include inorganic and organic acid salts such as dimethylaminoethyl (meth) acrylate and dimethylaminopropyl (meth) acrylamide, or quaternary ammonium salts such as methyl chloride and benzyl chloride with acrylamide. It is a copolymer. For example, as a monomer, (meth) acryloyloxyethyl trimethylammonium chloride, (meth) acryloyloxy 2-hydroxypropyltrimethylammonium chloride, (meth) acryloylaminopropyltrimethylammonium chloride, (meth) acryloyloxyethyldimethylbenzyl Examples include ammonium chloride, (meth) acryloyloxy 2-hydroxypropyldimethylbenzylammonium chloride, (meth) acryloylaminopropyldimethylbenzylammonium chloride, and the like. Most preferred are dimethylaminoethyl methacrylate, dimethylaminopropyl (meth) acrylamide, and acryloyloxyethyldimethylbenzylammonium chloride.

  Examples of anionic monomers are (meth) acrylic acid, itaconic acid, maleic acid, acrylamide 2-methylpropane sulfonic acid (salt), vinyl sulfonic acid, etc., with acrylic acid and itaconic acid being most preferred. is there. Examples of nonionic monomers include acrylamide, N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, N, N-dimethylacrylamide, acrylonitrile, diacetone acrylamide, and 2-hydroxyethyl (meth) acrylate. Most preferred is acrylamide.

  The molecular weight of the paper strength enhancer comprising these amphoteric water-soluble polymers is 500,000 to 5,000,000, preferably 1,000,000 to 3,000,000. If it is 500,000 or less, the paper strength enhancing effect is insufficient, and if it is 5 million or more, the cohesive force is increased and the formation of the paper after papermaking collapses. In addition, the solution viscosity becomes too high, dispersibility is deteriorated, and handling of the aqueous solution is also deteriorated. Although any product form can be used, it is generally supplied as a viscous aqueous solution.

  The addition amount of the anionic water-soluble polymer is 50 ppm to 5000 ppm, preferably 100 ppm to 1000 ppm, based on the solid content of the papermaking raw material. The addition amount of the paper strength enhancer made of an amphoteric polymer is 1000 ppm to 30000 ppm, preferably 1000 ppm to 5000 ppm.

  As the place where the anionic water-soluble polymer is added, a fan pump inlet, a screen inlet, a screen outlet or the like where the papermaking raw material is diluted with white water can be considered. Further, as a place for adding the paper strength enhancer composed of amphoteric polymers, there may be a raw material chest before blending the papermaking raw material and a machine chest after blending.

The papermaking pH applicable to the papermaking method relating to the yield improvement of the present invention is not particularly limited, but a remarkable effect is exhibited in acidic papermaking to which a sulfuric acid band is added.
Accordingly, the papermaking pH is applicable in the range of 3 to 9, but preferably 3 to 7. The target paper products are high-quality, medium-quality, or paperboard core base paper, white balls, liner base paper, etc., preferably paperboard core base paper, white balls, liner base paper, and the like.

(Synthesis Example 1) In a four-neck 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen introduction tube, deionized water: 167.9 g, ammonium sulfate 50 g, acrylamide 2-methylpropanesulfonic acid 22.1 g, 50% acrylamide: 86.2 g was added, and 25 mol% of acrylamide 2-methylpropanesulfonic acid was neutralized with 3.6 g of 30 wt% sodium hydroxide. Further, 18.9 g of a 15 wt% aqueous solution of acrylamide 2-methylpropanesulfonic acid polymer (neutralized 90 mol% of sulfonic acid group, solution viscosity 31,000 mPa · s) was added. Thereafter, nitrogen is introduced from the nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ° C. using a constant temperature water bath. 30 minutes after the introduction of nitrogen, 0.6 g of 0.1 wt% ammonium peroxodisulfate and 0.1 wt% aqueous solution of ammonium hydrogen sulfite were added in this order to initiate polymerization. After 3 hours from the start of polymerization, the same amount of each initiator was added, and after 6 hours, 3.0 g was added, and the reaction was completed in 15 hours. Let this prototype be prototype-1. The molar ratio of acrylamide 2-methylpropanesulfonic acid and acrylamide in Sample-1 was 30:70, and the viscosity was 620 mPa · s. As a result of microscopic observation, the particles were found to be 1 to 10 μm. After the reaction, the weight average molecular weight of this polymer was measured by a light scattering method. The results are shown in Table 1.

(Synthesis Examples 2-3) By the same operation as in Synthesis Example-1, dispersion (sample-2) composed of acrylamide 2-methylpropanesulfonic acid / acrylic acid / acrylamide = 30/15/55 (molar ratio), acrylic A dispersion (sample-3) consisting of acid / acrylamide = 30/70 (molar ratio) was synthesized. The results are shown in Table 1.

Synthesis Example 4 A reaction vessel equipped with a stirrer and a temperature controller was charged with 126.0 g of isoparaffin having a boiling point of 190 ° C. to 230 ° C. and 12.0 g of sorbitan monooleate. After adding 227.6 g of deionized water, 176.4 g of 80% aqueous acrylic acid (AAC), and 278.4 g of 50% aqueous acrylamide (AAM), 224.0 g of 35% aqueous sodium hydroxide solution (equivalent to acrylic acid) ) Was added while cooling so that the liquid temperature did not exceed 30 ° C. The molar ratio of acrylamide to acrylic acid after monomer incorporation is 50:50. Thereafter, the mixture was emulsified with stirring at 1000 rpm with a homogenizer for 60 minutes. To the obtained emulsion, 0.84 g (0.03% by weight of monomer) of isopropyl alcohol was added, and after nitrogen substitution, 2,2′-azobis [2- (5-methyl-2-imidazoline-2) was used as an initiator. -Yl) propane] 2.8 g of a 10% aqueous solution of dihydrochloride was added, and the polymerization reaction was started while controlling the temperature at 33 ± 1 ° C. After 5 o'clock, 0.56 g of the initiator was added, and The reaction was continued for 5 hours to complete the polymerization. After polymerization, 6.0 g of polyoxyethylene tridecyl ether (1.2% by weight with respect to the liquid) was added to and mixed with the resulting water-in-oil emulsion as a phase inversion agent to prepare a sample for use in the test (Sample 4). . The results are shown in Table 1.

(Synthesis Examples 5-6) By the same operation as in Synthesis Example-4, a water-in-oil emulsion consisting of acrylamide 2-methylpropanesulfonic acid / acrylic acid / acrylamide = 15/5/80 (molar ratio) (Sample-5) ), Acrylamide 2-methylpropanesulfonic acid / acrylic acid / acrylamide = 30/10/60 (molar ratio) water-in-oil emulsions (sample-6) were synthesized, respectively, and the results are shown in Table 1.

(Synthesis Examples 7-9) N, N-dimethylaminoethyl methacrylate / acrylic acid / acrylamide = 8/7/85 (molar ratio) (paper power -1), N, N-dimethylaminoethyl methacrylate / acryloyloxy by a conventional method Ethyldimethylbenzylammonium chloride / acrylic acid / acrylamide = 6/3/9/82 (molar ratio) (paper strength-2), N, N-dimethylaminoethyl methacrylate / itaconic acid / acrylic acid / acrylamide = 5/2 / Polymer aqueous solutions of amphoteric paper strength enhancer-1, amphoteric paper strength enhancer-2 and amphoteric paper strength enhancer-3 comprising 5/88 (molar ratio) (paper strength-3) were synthesized, and the results are shown in Table 1. Shown in

(Comparative Synthesis Example 1) In a five-neck separable flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube, 21.0 g of a dimethyldiallylammonium chloride polymer (30% aqueous solution, molecular weight 200,000) ( A total monomer of 5.0%), ion-exchanged water 178.1 g, ammonium sulfate 115.0 g, acrylamide 50% aqueous solution 67.4 g and acryloyloxyethyltrimethylammonium chloride, 80% aqueous solution 115.0 g were completely dissolved. I let you. 10% of 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride as an initiator after maintaining the internal temperature at 33 to 35 ° C. and replacing with nitrogen for 30 minutes. 2.5 g of aqueous solution (0.04% monomer) was added to initiate polymerization. After 2.5 hours from the start, a slight increase in viscosity of the reaction product was observed, but it quickly settled and transferred to the dispersion. 8 hours after the start, 1.3 g of the initiator solution was added, and polymerization was further performed for 8 hours. The resulting dispersion had a squeeze monomer concentration of 25.0%, a molar ratio of acrylamide to acryloyloxyethyltrimethylammonium chloride of 50:50, and a polymer particle size of 10 μm or less. This sample is referred to as Comparative-1 and the results are shown in Table 1.

(Comparative Synthesis Example 2) Comparative-2 consisting of acryloyloxyethyltrimethylammonium chloride / acrylamide / acrylic acid = 50/30/20 was synthesized by the same operation as Comparative Synthesis Example 1. The results are shown in Table 1.

製品形態；Ｄは塩水溶液中分散液、ＥＭは油中水型エマルション、Ａｑは水溶液、ＤＭＱ；アクリロイルオキシエチルトリメチルアンモニウム塩化物、ＤＭＢＣ；アクリロイルオキシエチルベンジルジメチルアンモニウム塩化物、ＡＡＣ；アクリル酸、ＡＡＭＳ；アクリルアミド２−メチルプロパンスルホン酸、ＡＡＭ；アクリルアミド、ＩＡ；イタコン酸、ＤＭＭ；メタクリル酸ジメチルアミノエチル、製品粘度；ｍＰａ・ｓ、分子量；重量平均分子量、紙力-１、紙力-２及び紙力-３は両性紙力増強剤−１、両性紙力増強剤−２及び両性紙力増強剤−３をそれぞれ表わす、 (Table 1)

Product form: D is a dispersion in a salt solution, EM is a water-in-oil emulsion, Aq is an aqueous solution, DMQ: acryloyloxyethyltrimethylammonium chloride, DMBC; acryloyloxyethylbenzyldimethylammonium chloride, AAC; acrylic acid, AAMS Acrylamide 2-methylpropanesulfonic acid, AAM; acrylamide, IA; itaconic acid, DMM; dimethylaminoethyl methacrylate, product viscosity; mPa · s, molecular weight; weight average molecular weight, paper power-1, paper power-2, and paper Force-3 represents the amphoteric paper strength enhancer-1, the amphoteric paper strength enhancer-2 and the amphoteric paper strength enhancer-3, respectively.

Corrugated waste paper was adjusted to a 405 ml beating degree with a Niagara type beater. While making this adjusted slurry 1.0% concentration and stirring at 300 rpm, commercially available emulsion sizing agent was 0.15% for pulp, aluminum sulfate (8.0% for Al2O3) and 3.0% for pulp. After adding to pH 5.2, the amphoteric paper strength enhancer-1 and the amphoteric paper strength enhancer-2 obtained in Synthesis Examples 7 to 8 were added to 0.2% of pulp and stirred for 10 seconds, and then synthesized. After adding anionic water-soluble polymer sample-1 to sample-2 and sample-4 to sample-5 obtained in Examples 1-2 and Synthesis Examples 4-5 to 0.05% pulp and stirring for 10 seconds, The pulp slurry was diluted to a concentration of 0.1%, and paper was made with a Tappi standard sheet machine to a basis weight of 125 g / m ² . The obtained wet paper was pressed at 5 kg / cm ² for 2 minutes and then dried with a 105 ° C. rotary dryer for 3 minutes to obtain a handmade paper. The handmade paper was conditioned at 20 ° C. and 65% HR for 24 hours, and then the specific burst strength was measured according to JIS: P8112 and the specific compressive strength was measured according to JIS: P8126. The results are shown in Table 2.

As a comparative test, the cationic water-soluble polymer and the amphoteric water-soluble polymer Comparative-1 and Comparative-2 obtained in Comparative Synthesis Examples 1 and 2 were used instead of the anionic water-soluble polymer. Papermaking, drying, and paper quality measurement were performed by various operations. The results are shown in Table 2.

  The test was conducted using liner raw materials (SS content 2.54%, pH 5.52 and ash content 0.20%) at the papermaking site. After making this papermaking raw material into a concentration of 0.7%, a commercially available emulsion sizing agent was added to 0.10% pulp, aluminum sulfate (8.0% as Al2O3) and 2.5% pulp to pH 5.31. After adding 0.25% of the amphoteric paper strength enhancer-2 and the amphoteric paper strength enhancer-3 obtained in Synthesis Examples 8 to 9 and stirring for 10 seconds, Synthesis Examples 2-3 and Synthesis were performed. After adding 0.035% of the anionic water-soluble polymer sample-3 to sample-4 and sample-5 to sample-6 obtained in Examples 5 to 6 and stirring for 10 seconds, the same manner as in Example 1 was performed. Papermaking was performed, and then paper quality was measured. The results are shown in Table 3.

As a comparative test, the cationic water-soluble polymer and the amphoteric water-soluble polymer Comparative-1 and Comparative-2 obtained in Comparative Synthesis Examples 1 and 2 were used instead of the anionic water-soluble polymer, and the same as in Example 2. Papermaking, drying, and paper quality measurement were performed by various operations. The results are shown in Table 3.

比破裂強度及び比圧縮強度；単位：無次元




(Table 2)

Specific burst strength and specific compressive strength; unit: dimensionless

比破裂強度及び比圧縮強度；単位：無次元 (Table 3)

Specific burst strength and specific compressive strength; unit: dimensionless

The paper production method of the present invention is characterized in that an anionic water-soluble polymer is added to a papermaking raw material before papermaking containing an amphoteric paper strength enhancer for the purpose of improving paper strength. An anionic water-soluble polymer is added to promote the fixing improvement of the amphoteric polyacrylamide type paper strength enhancer, so that even when a relatively large amount of the amphoteric polyacrylamide type paper strength enhancer is present in the papermaking system, Various types of polymers can be easily adsorbed, and as a result, it is possible to achieve a high yield of papermaking raw material and a high strength of papermaking. Therefore, industrial applicability is high.

Claims (7)

A paper manufacturing method comprising adding an anionic water-soluble polymer to a papermaking raw material before papermaking containing an amphoteric paper strength enhancer for the purpose of improving paper strength. The anionic water-soluble polymer contains one or more anionic monomers essential for the sulfonic acid group-containing monomer and optionally (meth) acrylamide and other nonionic monomers that can be copolymerized. The water-soluble monomer mixture is composed of a dispersion having a particle size of 100 mμ or less produced by a dispersion polymerization method in the presence of a dispersant composed of a polymer soluble in the aqueous salt solution in an aqueous salt solution. Item 2. A method for producing paper according to Item 1. The anionic water-soluble polymer contains one or more anionic monomers essential for the sulfonic acid group-containing monomer and optionally (meth) acrylamide and other nonionic monomers that can be copolymerized. A water-soluble monomer mixture and water, an at least one hydrocarbon water-immiscible oily substance, and an amount effective to form a water-in-oil emulsion and at least one surfactant having an HLB. 2. The method for producing paper according to claim 1, comprising a water-in-oil polymer emulsion produced by polymerizing each of them after mixing and vigorously stirring to form a water-in-oil emulsion. . The method for producing paper according to claim 2 or 3, wherein a monomer having a plurality of vinyl groups coexists in an amount of 0.001 to 0.5 mol% with respect to the water-soluble monomer mixture. The paper manufacturing method according to claim 1, wherein the amphoteric paper strength enhancer has a weight average molecular weight of 500,000 to 5,000,000. The paper manufacturing method according to claim 1, wherein a sulfate band is present in the papermaking raw material, and the papermaking pH is 3-7. The paper manufacturing method according to claim 1 or 6, wherein the paper is paperboard.