JP7300082B2 - Anionic retention aid and papermaking method using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a retention aid used in a papermaking process and a papermaking method using the same. More specifically, the present invention relates to an anionic retention aid used in a papermaking process to improve the retention of papermaking raw materials on a wire. It relates to a method for improving

In the papermaking process of coating base paper, PPC paper, woodfree paper, paperboard, newsprint, etc., to improve the yield rate on the wire of papermaking chemicals, fine fibers, fillers, etc. At the same time, a drainage improver (or a retention drainage improver) is used with an emphasis on the function of improving drainage. Polyacrylamide-based (PAM-based) polymers are generally used as retention aids, but due to recent diversification of papermaking conditions, effective retention aids and retention systems are different. Mainly cationic PAM or amphoteric PAM, but anionic PAM is effective in some cases. A decrease in the yield of papermaking raw materials on the wire not only lowers productivity, but also lowers the yield of fillers contained in papermaking raw materials and papermaking agents such as strength agents and sizing agents. This is one of the factors that lead to quality deterioration. Therefore, it is necessary to apply an optimum retention aid and retention system, and efforts have been made mainly to improve the performance of cationic or amphoteric PAM. However, compared to cationic or amphoteric PAM, efforts to improve the performance of anionic PAM are comparatively few, and a more effective polymer is desired under papermaking conditions where anionic PAM is effective.
An increase in the molecular weight of the anionic PAM can improve the yield rate, but it greatly affects the paper quality, especially formation, and limits the addition rate. Therefore, as a method for suppressing the influence on formation, for example, Patent Literature 1 describes a yield improvement method of adding an aqueous solution of an anionic water-soluble polymer with a reduced apparent viscosity. In this method, an inorganic salt or an inorganic acid is added to an aqueous solution in which a polymer is dissolved to lower the apparent viscosity, thereby increasing the diffusibility into the paper material and the yield. However, the actual situation is that a large yield improvement cannot be obtained compared to the use of a polymer having a high molecular weight.
Patent Document 2 discloses cross-linked anionic or amphoteric organic polymer microparticles, and Patent Document 3 discloses a water-in-water polymer dispersion containing a crosslinked anionic polymer. is described, and its use for the purpose of yield improvement is also suggested. However, although these crosslinked polymers can relatively suppress the effect on paper quality, they do not provide a high retention effect compared to linear polymers, especially at low addition rates. Therefore, there is a demand for the development of an anionic retention improver capable of obtaining a high retention effect without impairing the formation of paper.

Japanese Patent Application Laid-Open No. 2001-295196 JP-A-4-226102 Japanese translation of PCT publication No. 2013-502502

TECHNICAL FIELD The present invention relates to a retention improver used in a papermaking process and a method for improving the retention of papermaking raw materials using the same. An object is to provide an improvement method.

As a result of intensive studies to solve the above problems, it was found that a water-in-oil emulsion of an anionic water-soluble polymer containing an inorganic salt having a specific composition and physical properties was used as a retention aid for papermaking raw materials before papermaking. It is possible to improve the yield of papermaking raw materials by using it.

By using the water-in-oil emulsion of the anionic water-soluble polymer of the present invention as a retention aid in the papermaking raw material before papermaking, the anionic retention aid is effective for the papermaking raw material, resulting in a higher yield. It is possible to obtain a high efficiency rate and achieve an improvement in productivity and an improvement in paper quality.

一般式（１）
Ｒ_１は水素、メチル基又はカルボキシメチル基、ＱはＳＯ_３、Ｃ_６Ｈ_４ＳＯ_３、ＣＯＮＨＣ（ＣＨ_３）_２ＣＨ_２ＳＯ_３ 、ＣＯＯ、Ｒ_２は水素又はＣＯＯＹ_２、Ｙ_１あるいはＹ_２は水素又は陽イオンをそれぞれ表わす。
The anionic water-soluble polymer in the present invention contains 5 to 80 mol% of a monomer represented by the following general formula (1), 20 to 95 mol% of a copolymerizable nonionic water-soluble monomer, and an inorganic An aqueous solution of a monomer mixture containing a salt is emulsified with a surfactant so that the water-immiscible organic liquid becomes a continuous phase and the aqueous monomer mixture solution becomes a dispersed phase. After polymerization, a phase change agent is added. It is manufactured by

General formula (1)
R ₁ is hydrogen, methyl group or carboxymethyl group, Q is SO ₃ , C ₆ H ₄ SO ₃ , CONHC(CH ₃ ) ₂ CH ₂ SO ₃ , COO, R ₂ is hydrogen or COOY ₂ , Y ₁ or Y ₂ represents hydrogen or a cation, respectively.

The anionic monomer used in producing the anionic water-soluble polymer in the present invention, that is, the monomer represented by the general formula (1) is in the range of 5 to 80 mol %. If the amount is less than 5 mol %, a large retention effect due to the anionic charge of the anionic water-soluble polymer cannot be obtained, and if it exceeds 80 mol %, it becomes difficult to obtain a high molecular weight polymer. It is preferably in the range of 10 to 70 mol %.

Examples of the anionic monomer represented by the general formula (1) include vinylsulfonic acid, vinylbenzenesulfonic acid or 2-acrylamido-2-methylpropanesulfonic acid, methacrylic acid, acrylic acid, itaconic acid, maleic acid , and or salts thereof, and the like. Two or more of these may be used in combination.

When producing the anionic water-soluble polymer in the present invention, a cationic monomer can be used as long as the effect is not impaired. The cationic monomer used at that time is in the range of 0 to 10 mol %. Preferably, it is 5 mol % or less.

When using a cationic monomer in the present invention, there are the following. That is, it is a quaternized product with methyl chloride or benzyl chloride, such as dimethylaminoethyl (meth)acrylate or dimethylaminopropyl (meth)acrylamide. Examples include (meth)acryloyloxyethyltrimethylammonium chloride, (meth)acryloyloxy-2-hydroxypropyltrimethylammonium chloride, (meth)acryloylaminopropyltrimethylammonium chloride, (meth)acryloyloxyethyldimethylbenzylammonium chloride, (meth)acryloyloxy-2-hydroxypropyldimethylbenzylammonium chloride, (meth)acryloylaminopropyldimethylbenzylammonium chloride. It is also possible to combine two or more of these.

The copolymerizable nonionic monomers used in the present invention include (meth)acrylamide, N,N'-dimethylacrylamide, acrylonitrile, 2-hydroxyethyl (meth)acrylate, diacetoneacrylamide, N- vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, acryloylmorpholine and the like. Two or more of these may be used in combination. The number of moles of the nonionic monomer is 20 to 95 mol%, preferably 30 to 90 mol%.

The anionic water-soluble polymer in the present invention can be produced by copolymerizing a monomer mixture consisting of anionic monomers and nonionic monomers. Polymerization is carried out by a conventional water-in-oil emulsion polymerization method after preparing an aqueous solution in which these monomers are mixed.

Methods for producing a water-in-oil emulsion include methods described in JP-A-55-137147, JP-A-59-130397, JP-A-10-140496, JP-A-2011-99076, and the like. It can be manufactured appropriately according to the following. A monomer mixture comprising an anionic monomer and a nonionic monomer, water, an oily substance comprising a water-immiscible hydrocarbon, and an amount and HLB effective to form a water-in-oil emulsion. At least one surfactant is mixed and vigorously stirred to form a water-in-oil emulsion, followed by polymerization.

An inorganic salt is added during the production of the water-in-oil emulsion of the anionic water-soluble polymer in the present invention. The timing of adding the inorganic salt is in the aqueous solution mixed with the monomer mixture consisting of the anionic monomer and the nonionic monomer. Alternatively, a portion of the inorganic salt may be divided into an aqueous solution mixed with the monomer mixture, and the remainder may be added to the water-in-oil emulsion during polymerization or after copolymerization.

The inorganic salt to be added is a salt obtained by combining cations such as alkali metal ions such as sodium and potassium ions, ammonium ions and magnesium ions, and anions such as halide ions, sulfate ions, nitrate ions and phosphate ions. Available. The concentration of these salts is 0.5 to 10% by mass based on the amount of the water-in-oil emulsion. If it is 0.5% by mass or more, it is difficult to exhibit the effect, and if it is added in excess of 10% by mass, it is difficult in terms of the manufacturing process due to the solubility of the inorganic salt.

Examples of oily substances composed of hydrocarbons used as a dispersion medium include paraffins, mineral oils such as kerosene, light oil, and medium oil, and hydrocarbon-based oils having properties such as boiling points and viscosities in substantially the same ranges as these. Synthetic oils or mixtures thereof may be mentioned. The content is in the range of 20% by mass to 50% by mass, preferably in the range of 20% by mass to 35% by mass, based on the total weight of the water-in-oil emulsion.

Examples of the at least one surfactant having an effective amount and HLB to form a water-in-oil emulsion are nonionic surfactants with an HLB of 3-11, specific examples of which include sorbitan monooleate, Sorbitan monostearate, sorbitan monopalmitate, polyoxyethylene nonylphenyl ether and the like. The amount of these surfactants to be added is 0.5 to 10% by mass, preferably 1 to 5% by mass, based on the total amount of the water-in-oil emulsion.

After polymerization, a hydrophilic surfactant called a phase-inverting agent is added to make the emulsion particles covered with a film of oil more compatible with water, and the water-soluble polymer inside is more easily dissolved in water. Dilute with Examples of hydrophilic surfactants include cationic surfactants and nonionic surfactants with an HLB of 9 to 15, such as polyoxyethylene polyoxypropylene alkyl ethers and polyoxyethylene alcohol ethers.

The polymerization conditions are usually appropriately determined depending on the monomers used and copolymerization mole %, and the temperature is in the range of 20 to 80°C, preferably 20 to 60°C. A radical polymerization initiator is used for polymerization initiation. These initiators may be either oil-soluble or water-soluble, and can polymerize any of azo, redox, and peroxide initiators. Examples of oil-soluble azo initiators include 2,2'-azobisisobutyronitrile, dimethyl-2,2'-azobisisobutyrate, 1,1'-azobiscyclohexanecarbonitrile, 2,2 '-azobis-2-methylbutyronitrile, 2,2'-azobis-2-methylpropionate, 4,4'-azobis-(4-methoxy-2,4-dimethyl)valeronitrile and the like.

Examples of water-soluble azo initiators include 2,2′-azobis(amidinopropane) dihydrochloride, 2,2′-azobis[2-(5-methyl-imidazolin-2-yl)propane]hydrogen dichloride compound, 4,4'-azobis(4-cyanovaleric acid) and the like. Examples of redox systems include combinations of ammonium peroxodisulfate with sodium sulfite, sodium hydrogen sulfite, trimethylamine, tetramethylethylenediamine, and the like. Further examples of peroxides include ammonium or potassium peroxodisulfate, hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, t-butylperoxy-2-ethylhexanoate, etc. can be mentioned.

In order to adjust the degree of polymerization, it is effective to use 0.1 to 5 mass % of isopropyl alcohol or 0.02 to 0.5 mass % of sodium formate to the monomer.

The polymerization concentration of the monomer is in the range of 20 to 50% by mass, and the polymerization concentration and temperature are appropriately set according to the composition of the monomer and the selection of the initiator.

Polyacrylamide-based (PAM-based) polymers, which are widely used as retention aids, are designed to increase the molecular weight of PAM-based polymers in order to further improve the retention of papermaking raw materials in the wire part of the papermaking process. Studies have been conducted on methods for enhancing the cross-linking adsorption action with pulp fibers and fillers in the raw material to improve the flocculation effect. However, increasing the molecular weight causes excessive entanglement between polymers, resulting in a decrease in the charge neutralization action and a significant improvement in the yield effect may not be obtained. It is presumed that the anionic water-soluble polymer in the present invention maintains a high molecular weight and suppresses excessive entanglement between polymers, thereby obtaining a high retention effect. It is considered that the addition of the inorganic salt suppresses the entanglement, and as a result, both the cross-linking adsorption action and the charge neutralization action are achieved, resulting in a high yield effect.

The polymer structure of the anionic water-soluble polymer in the present invention can be indexed by the charge inclusion rate. The charge inclusion rate used in the present invention is defined as follows.
Definition (A): Charge inclusion rate (%) = (1-α/β) x 100
α is a 0.025% by mass aqueous solution of an anionic water-soluble polymer adjusted to pH 10.0 with ammonia using a PCD titrator (PCD-500, AT-510) manufactured by Kyoto Electronics Industry Co., Ltd., dropping liquid: 1/ It is a titration amount obtained by titration with a 1000N polydiallyldimethylammonium chloride aqueous solution, dropping rate: 0.1 ml/5 sec, end point determination: 0 mV. β is a 0.0025% by mass aqueous solution of an anionic water-soluble polymer adjusted to pH 10.0 with ammonia using an Ace homogenizer (AM-11) manufactured by Nippon Seiki Seisakusho Co., Ltd. under the conditions of 10000 rpm and 5 minutes. In addition, titration was similarly performed using a PCD titrator with a dropping liquid: 1/1000N polydiallyldimethylammonium chloride aqueous solution, dropping rate: automatic control, and endpoint determination: 0 mV.
In addition, the PCD titration device is not limited to the above device as long as it can perform similar measurements. The error must be within ±0.5%.

The titration amount α value is obtained by dropping an aqueous solution of polydiallyldimethylammonium chloride having an opposite charge to the anionic water-soluble polymer sample, and measuring the "surface" (particulate surface portion) of the anionic water-soluble polymer. means an operation to cause an ionic group present in to undergo an ionic electrostatic reaction.
The titer β value is considered to correspond to the theoretical charge amount calculated from the chemical composition of the water-soluble polymer. That is, since there are a large amount of opposite charges generated by shearing the water-soluble polymer, it is considered that not only surface charges but also internal charges are electrostatically neutralized. The higher the degree of cross-linking, the smaller the value of α relative to β, the larger the (1−α/β) value, and the higher the charge inclusion rate (ie, the higher the degree of cross-linking).

That is, it can be said that a water-soluble polymer with a high charge inclusion rate is a water-soluble polymer with increased cross-linking, and a water-soluble polymer with a low charge inclusion rate is a water-soluble polymer with less cross-linking. The reason for this is explained as follows. In a dilute solution, a straight-chain water-soluble polymer has a nearly "extended" shape. On the other hand, a crosslinked water-soluble polymer has a rounded particle shape in a solution, and the ionic groups present inside the particles are difficult to appear on the outside, and the reaction with the opposite charge is slow. thought to occur.

The anionic water-soluble polymer in the present invention preferably has a charge inclusion rate of 15.0% or less. In the case of normal linear or cross-linked polymers, shrinkage of the polymer and entanglement between polymers occur, reducing the charge existing on the surface of the polymer, suppressing the charge neutralization action, and reducing the yield effect. There is
In the case of having a branched structure or a crosslinked structure, it is considered that branching progresses to intermolecular crosslinking and strong entanglement occurs, resulting in a high charge encapsulation rate, and this value exceeds 15.0%. In addition, the linear polymer also exceeds 15.0% if it has a high molecular weight. When the charge inclusion rate is 15.0% or less, a high yield effect can be obtained even with a high molecular weight. The charge inclusion rate is preferably 10.0% or less, and more preferably 8.0% or less.
In linear polymers, entanglement occurs due to shrinkage of the polymer, resulting in a high charge inclusion rate. When branching progresses or in the crosslinked polymer region, intermolecular crosslinks cause even stronger entanglement and increase the charge inclusion rate. It is thought that On the other hand, in the anionic water-soluble polymer of the present invention, it is presumed that steric hindrance and charge repulsion occur due to the addition of an inorganic salt, making it difficult for entanglement between polymers to occur. In the anionic water-soluble polymer of the present invention, entanglement or the like between polymers is less likely to occur when the charge encapsulation rate is in the range of 15.0% or less. , and it is considered that a high yield effect is exhibited. In addition, the value of the charge encapsulation rate specified in the present invention may be - (minus), but if it is 15.0% or less, it is within the range of the structure of the water-soluble polymer of the present invention and is negative in measurement. Even if it is, it is acceptable. Experimentally, a water-soluble polymer with a minimum charge encapsulation rate of -3.0 was obtained, confirming the effect of the present invention.

In the anionic water-soluble polymer of the present invention, a crosslinkable monomer may be used as a structural modifier during or after polymerization. When used, it is preferably 0.002% by mass or less relative to the total amount of monomers, because the higher the addition rate, the higher the charge encapsulation rate. Examples of crosslinkable monomers include N,N'-methylenebis(meth)acrylamide, triallylamine, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, di 1,3-butylene glycol methacrylate, polyethylene glycol di(meth)acrylate, N-vinyl(meth)acrylamide, N-methylallylacrylamide, glycidyl acrylate, polyethylene glycol diglycidyl ether, acrolein, glyoxal, vinyltrimethoxy Examples include silane, and among these, N,N'-methylenebis(meth)acrylamide is preferred.

The anionic water-soluble polymer in the present invention requires a high molecular weight in order to obtain high cohesive strength. When the molecular weight is expressed in terms of intrinsic viscosity, the intrinsic viscosity of 0.5% by mass of the water-soluble polymer constituting the water-in-oil emulsion measured at 25° C. in a 4% by mass saline solution is 15 to 30 dl/g. However, it is preferably in the range of 18 to 30 dl/g, more preferably 20 to 30 dl/g. If the intrinsic viscosity is lower than 15 dl/g, the effect of improving the yield is significantly reduced, and if it is higher than 30 dl/g, the quality of paper, especially formation, may deteriorate. The weight average molecular weight determined by the intrinsic viscosity method is preferably in the range of 10 million to 30 million. In addition, the viscosity measured at 25° C. (viscosity of 0.5% by mass aqueous solution of salt solution) when dissolved in 4% by mass saline solution at a polymer concentration of 0.5% by mass can also be used as an index of molecular weight. , the viscosity of a 0.5% by mass salt aqueous solution is preferably in the range of 150 to 350 mPa·s, more preferably 200 to 300 mPa·s.

The retention aid comprising a water-in-oil emulsion of an anionic water-soluble polymer according to the present invention has a reduced viscosity when dissolved in water due to the inclusion of an inorganic salt, and increases dispersibility when added to papermaking raw materials. It is speculated that this also contributes to the improvement of performance. High-molecular-weight anionic polyacrylamide-based polymers, which are commonly used as anionic retention aids, have high aqueous solution viscosities. (Aqueous solution viscosity of 0.2% by mass) is 1000 mPa s or more, but the water-in-oil emulsion of the anionic water-soluble polymer in the present invention adjusts the addition rate of the inorganic salt even if it has a high molecular weight. By doing so, one having a low aqueous solution viscosity can be produced. For example, even if the intrinsic viscosity is 25 dl/g or more, it is possible to produce a 0.2% by mass aqueous solution of 800 mPa·s or less.

The retention aid comprising a water-in-oil emulsion of an anionic water-soluble polymer in the present invention is added to papermaking raw materials before papermaking. Normally, in the papermaking process, the pulp dry solids concentration is lower than 2.0% by mass due to white water, fresh water, etc. immediately before the paper machine, when the papermaking raw material has been transferred from the upstream with a pulp dry solids concentration of 2.0% by mass or more. Diluted in paper stock. Generally, it is diluted to 0.5 to 1.5% by mass, and these are called inlet raw materials and headbox raw materials, and the yield of these raw materials (hereinafter referred to as inlet raw materials) is improved. Agents are added and paper is made. The retention aid of the present invention is also applied to inlet raw materials.

The water-in-oil emulsion of the anionic water-soluble polymer in the present invention is generally added in the papermaking process before and after the fan pump or screen, which is the shearing process, as a conventional retention aid. Similar addition sites apply to water-in-oil emulsions of anionic water-soluble polymers. It is preferable to add before and after the screen, which is the final shearing step, in order to maximize the yield rate with a small addition rate. Since it has little effect on formation even after screening, it is possible to increase the addition rate compared to conventional anionic retention aids. Moreover, you may divide|segment and may add.

The types of paper for which the retention aid comprising a water-in-oil emulsion of an anionic water-soluble polymer is used in the present invention include newsprint, high-quality printing paper, medium-quality printing paper, gravure printing paper, PPC paper, and coated paper. Examples include base paper, lightly coated paper, packaging paper, paperboard such as liner and core base paper. It is effective for papermaking raw materials with a relatively low amount of anions in papermaking raw materials, that is, with a relatively low cationic demand. Specifically, the anionic water-soluble polymer in the present invention works effectively if the cationic demand is 0.01 meq/L or less. Preferably, it is 0.008 meq/L or less. Also, the effect is exhibited even if the papermaking raw material exhibits cationic properties (=anion required amount). It is effective when applied to paperboard such as liner and corrugating medium containing a relatively large amount of a paper strength agent such as cationic or amphoteric starch or aluminum sulfate. Cation demand is determined according to Whatman No. It is expressed as a value (meq/L) measured by a commercially available particle charge meter (Mutek PCD-04 type, etc.).

The retention aid comprising a water-in-oil emulsion of an anionic water-soluble polymer in the present invention can be added at the same time as paper strength agents, sizing agents, aluminum sulfate, coagulants and other papermaking chemicals. Other cationic water-soluble polymers, amphoteric water-soluble polymers, anionic water-soluble polymers, nonionic water-soluble polymers, bentonite, colloidal silica, and the like can also be used in combination as retention-enhancing formulations.

The retention improver comprising a water-in-oil emulsion of an anionic water-soluble polymer and the method for improving the retention of papermaking raw materials using the same according to the present invention will be specifically described below. is not limited to

(Example 1)
Samples 1 to 8 were prepared as a retention aid comprising a water-in-oil emulsion of an anionic water-soluble polymer according to the present invention. Production was carried out by adding an inorganic salt to an aqueous solution in which the monomer mixture was mixed during polymerization, and by a conventional water-in-oil emulsion polymerization method. These compositions and physical properties are shown in Table 1.

(Comparative Example 1) Retention improver samples 9 to 12 comprising water-in-oil emulsions of anionic water-soluble polymers outside the scope of the present invention were prepared by a conventional water-in-oil emulsion polymerization method. These compositions and physical properties are shown in Table 1. In addition, commercially available yield improver samples A to C were prepared. These compositions and physical properties are shown in Table 2.

ＡＡＣ：アクリル酸
ＡＡＭ：アクリルアミド
無機塩；ＳＣ：塩化ナトリウム、ＭＳ：硫酸マグネシウム
０．２質量％水溶液粘度：高分子濃度が０．２質量％になるように水で溶解したときの２５℃において測定した粘度（ｍＰａ・ｓ）。 (Table 1)

AAC: acrylic acid AAM: acrylamide inorganic salt; SC: sodium chloride, MS: magnesium sulfate 0.2% by mass aqueous solution Viscosity: measured at 25°C when dissolved in water so that the polymer concentration becomes 0.2% by mass viscosity (mPa·s).

製品形態；Ｄ：塩水液中分散重合液、Ｅ：油中水型エマルジョン
０．２質量％水溶液粘度：高分子濃度が０．２質量％になるように水で溶解したときの２５℃において測定した粘度（ｍＰａ・ｓ）。
０．５質量％塩水溶液粘度：４質量％食塩水中に高分子濃度が０．５質量％になるように溶解したときの２５℃において測定した粘度（ｍＰａ・ｓ）。 (Table 2)

Product form; D: Dispersed polymer solution in salt water solution, E: Water-in-oil emulsion 0.2% by mass aqueous solution Viscosity: Measured at 25°C when dissolved in water so that the polymer concentration becomes 0.2% by mass viscosity (mPa·s).
Viscosity of 0.5% by weight aqueous salt solution: Viscosity (mPa·s) measured at 25° C. when the polymer concentration is 0.5% by weight in 4% by weight saline solution.

(Example 2) Using LBKP prepared to have a beating degree of 360 mL, a yield rate measurement test was conducted using a Bullitt type dynamic jar tester (using a 30-mesh wire). The LBKP stock was diluted with clear water, and light calcium carbonate was added to prepare the adjusted stock. The physical properties of the adjusted paper stock are: solid content concentration 9649 ppm, Ash content such as light calcium carbonate 41.1% by mass relative to paper stock solid content concentration, pH 8.9, electrical conductivity 18 mS/m, Whatman No. The cation demand was 0.0045 meq/L and the turbidity was 34 NTU (measured by HACH Model 2100P) using Mutec PCD-04 model of 41 filter paper filtrate. A predetermined amount of the adjusted stock was sampled in a Bullitt type dynamic jar tester, 1% by mass of cationic starch (commercially available) was added to the solid content of the stock, and the mixture was stirred at 1000 rpm for 20 seconds. A 1% by mass aqueous solution was added at 200 ppm (pure polymer content) relative to the solid content of the paper material, and after stirring at a stirring speed of 1000 rpm for 10 seconds (assuming addition of screen outlet in the papermaking process), the filtrate was collected and filtered. After filtration with No. 41 filter paper, SS was measured, and after measuring the total retention rate, the filter paper was incinerated at 525° C. for 2 hours to measure the ash retention rate. Similar tests were also conducted on samples 2-7. These results are shown in Table 3.

(Comparative Example 2) Using the same conditioned stock as in Example 2, the same test as in Example 2 was conducted using the samples in Tables 1 and 2 outside the scope of the present invention. In addition, a sample (Sample 10-1 ) was used to conduct the test. These results are shown in Table 3.

(Table 3)

Examples using a water-in-oil emulsion of an anionic water-soluble polymer produced by adding an inorganic salt during polymerization showed a higher retention effect than a sample without adding an inorganic salt during polymerization. rice field. It was confirmed that, when the number of moles of the anionic monomer was the same, the inclusion of the inorganic salt improved the retention effect compared to the polymer containing no inorganic salt. Also, from a comparison of Sample 10 and Sample 10-1, it was confirmed that addition of an inorganic salt to the aqueous solution did not significantly improve the yield, and performance was improved by including an inorganic salt during production. In this paper stock, the retention effect of Sample C was lower than that of the other samples, and the anionic retention aid was more effective than the cationic retention aid.

(Example 3) Using LBKP prepared to have a beating degree of 360 mL, a yield rate measurement test was conducted using a Bullitt type dynamic jar tester (using a 30-mesh wire). The LBKP stock was diluted with clear water, and light calcium carbonate was added to prepare the adjusted stock. The physical properties of the adjusted paper stock are: solid content concentration 10000 ppm, Ash content such as light calcium carbonate 41% by mass relative to paper stock solid content concentration, pH 8.8, electrical conductivity 17 mS/m, Whatman No. The cation demand was 0.0061 meq/L and the turbidity was 154 NTU (measured by HACH Model 2100P) using Mutech PCD-04 model of 41 filter paper filtrate. A predetermined amount of the adjusted stock was collected in a Bullitt type dynamic jar tester, 1% by mass of cationic starch (commercially available) was added to the solid content of the stock, and the mixture was stirred at 700 rpm for 20 seconds. Add 200 ppm or 300 ppm of a 1% by mass aqueous solution to the solid content of the paper material (polymer pure content), stir at a stirring speed of 700 rpm for 10 seconds (assuming addition to the screen outlet in the papermaking process), collect the filtrate, and measure Whatman No. . After filtration with No. 41 filter paper, SS was measured, the total retention rate was measured, the filter paper was incinerated at 525° C. for 2 hours, and the ash retention rate was measured. Table 4 shows the results.

(Comparative Example 3) Using the same conditioned stock as in Example 3, the same test as in Example 3 was performed using Sample 12 in Table 1. Table 4 shows the results.

(Table 4)

In the example using the polymer sample 8 having 10 mol % of the anionic monomer as the structural unit, the yield effect was improved compared to the polymer sample 12 having the same number of moles as the structural unit. It was confirmed that, when the number of moles of the anionic monomer was the same, the inclusion of the inorganic salt improved the retention effect compared to the polymer containing no inorganic salt. This means that, in the anionic water-soluble polymer of the present invention, the retention effect is improved by applying a polymer sample having the number of moles of the anionic monomer effective for the properties of the paper stock as a structural unit. .

(Embodiment 4) A yield rate measurement test was conducted using a bullet type dynamic jar tester (using a 30-mesh wire). As a raw material, an inlet raw material (pH 8.0, electrical conductivity 112 mS/m, cationic demand 0.0024 meq/L, turbidity 10 NTU, SS 3000 ppm, Ash 990 ppm), which is a paperboard liner paper stock obtained from a certain paper manufacturing company, was used. . A predetermined amount of the inlet raw material was collected in a Bullitt type dynamic jar tester, 1% by mass of cationic starch (commercially available) was added to the solid content of the paper stock, and the mixture was stirred at 600 rpm for 30 seconds. A 1% by mass aqueous solution was added at 320 ppm (pure polymer content) relative to the solid content of the paper stock, and after stirring at a stirring speed of 600 rpm for 30 seconds (assuming addition to the screen entrance in the papermaking process), the filtrate was collected and filtered using Whatman No. After filtration with No. 41 filter paper, SS was measured, the total retention rate was measured, the filter paper was incinerated at 525° C. for 2 hours, and the ash retention rate was measured. A similar test was also conducted on Sample 4. Table 5 shows the results.

(Comparative Example 4) Sample 9 was subjected to the same test as in Example 4 using the same raw materials as in Example 4. Table 5 shows the results.

(Table 5)

(Example 5) Using the same raw material as in Example 4, a freeness test was carried out using a DDA (Dynamic Drainage Analyzer, Matsubo Co.). A predetermined amount of raw material was charged into a DDA stirred tank with a 62 mesh wire at the bottom. After stirring at a stirring speed of 600 rpm for 5 seconds, 1% by mass of cationic starch (commercial product) based on the solid content of the paper stock was added. Add 320 ppm (pure polymer content) to raw material solid content, stir for 30 seconds at a stirring speed of 600 rpm (assuming addition to screen inlet), then suck paper material under reduced pressure of 300 mBar to form a sheet on the wire. Drainage time and sheet moisture content after 35 seconds of suction were measured. A similar test was also conducted on Sample 4. Table 6 shows the results.

(Comparative Example 5) Sample 9 was subjected to the same test as in Example 5 using the same raw materials as in Example 4. Table 6 shows the results.

(Table 6)

The retention aid comprising a water-in-oil emulsion of an anionic water-soluble polymer according to the present invention has an improved retention effect as compared with conventional anionic retention aids, and the results of the drainage test show that the retention aid is effective. It was confirmed that the drainage time was shortened and the water content of the sheet was lowered, so that the drainage effect was excellent.

The retention aid of the present invention comprising a water-in-oil emulsion of an anionic water-soluble polymer exhibits high retention and drainage effects even at a low addition rate compared to conventional anionic retention aids. was confirmed. By applying the retention improver of the present invention, it is possible to suppress the addition rate compared to conventional anionic retention improvers and reduce the influence on formation, improving productivity and paper quality. improvement can be achieved.

Claims (4)

As the monomer represented by the following general formula (1), vinylsulfonic acid, vinylbenzenesulfonic acid or 2-acrylamido-2-methylpropanesulfonic acid, methacrylic acid, acrylic acid, itaconic acid, maleic acid, or their 5 to 80 mol % of one or more selected from salts , 20 to 95 mol % of copolymerizable nonionic water-soluble monomers and 0.5 to 10 mol % of inorganic salts based on the liquid volume of the water-in-oil emulsion An aqueous monomer mixture containing % by mass is emulsified with a surfactant so that the water-immiscible organic liquid becomes a continuous phase and the monomer mixture aqueous solution becomes a dispersed phase, and after polymerization, a phase change agent is added. A method for producing a retention aid comprising a water-in-oil emulsion of an anionic water-soluble polymer produced by

General formula (1)
R ₁ is hydrogen, methyl group or carboxymethyl group, Q is SO ₃ , C ₆ H ₄ SO ₃ , CONHC(CH ₃ ) ₂ CH ₂ SO ₃ , COO, R ₂ is hydrogen or COOY ₂ , Y ₁ or Y ₂ represents hydrogen or a cation, respectively. 2. The anionic according to claim 1, wherein the anionic water-soluble polymer has an intrinsic viscosity of 15 to 30 dl/g in a 4% by mass saline solution at 0.5% by mass measured at 25°C. A method for producing a retention aid comprising a water-in-oil emulsion of a water-soluble polymer. 2. The water-in-oil type of an anionic water-soluble polymer according to claim 1, wherein the anionic water-soluble polymer has a charge inclusion rate of 15.0% or less as measured by the definition (A) below. A method for producing a retention aid comprising an emulsion.
Definition (A): Charge inclusion rate (%) = (1-α/β) x 100
α is the titration amount obtained by titrating an anionic water-soluble polymer aqueous solution adjusted to pH 10.0 with ammonia with an aqueous polydiallyldimethylammonium chloride solution. β is a titration amount obtained by adding shear to an anionic water-soluble polymer aqueous solution adjusted to pH 10.0 with ammonia and titrating with an aqueous solution of polydiallyldimethylammonium chloride. As the monomer represented by the following general formula (1), vinylsulfonic acid, vinylbenzenesulfonic acid or 2-acrylamido-2-methylpropanesulfonic acid, methacrylic acid, acrylic acid, itaconic acid, maleic acid, or their 5 to 80 mol % of one or more selected from salts , 20 to 95 mol % of copolymerizable nonionic water-soluble monomers and 0.5 to 10 mol % of inorganic salts based on the liquid volume of the water-in-oil emulsion An aqueous monomer mixture containing % by mass is emulsified with a surfactant so that the water-immiscible organic liquid becomes a continuous phase and the monomer mixture aqueous solution becomes a dispersed phase, and after polymerization, a phase change agent is added. A papermaking method characterized by adding a water-in-oil emulsion of an anionic water-soluble polymer produced as described above to a papermaking raw material before papermaking.

General formula (1)
R ₁ is hydrogen, methyl group or carboxymethyl group, Q is SO ₃ , C ₆ H ₄ SO ₃ , CONHC(CH ₃ ) ₂ CH ₂ SO ₃ , COO, R ₂ is hydrogen or COOY ₂ , Y ₁ or Y ₂ represents hydrogen or a cation, respectively.