JP7445859B2 - Pitch control agent made of amphoteric water-soluble polymer - Google Patents

Description

The present invention relates to a pitch control agent for suppressing pitch troubles in the paper manufacturing process and a pitch reduction method using the same. Specifically, the present invention relates to a pitch control agent made of an amphoteric water-soluble polymer having a specific composition and physical properties. and a pitch reduction method in which it is added in a papermaking process before papermaking.

In the paper manufacturing process, anion trash (anionic impurities), micro pitch, and turbidity components are present in large amounts in papermaking raw materials due to an increase in the proportion of used paper, neutral papermaking, and closed papermaking water. . As long as these anion trash, micro pitch, and turbidity components exist in the papermaking raw materials in a fine state, they rarely occur as defects in papermaking, but they can become agglomerated due to stirring, aeration, pH changes, and the addition of chemicals. This may cause product stains and defects. Pitch that is not fixed to the pulp fibers and has progressed to agglomeration becomes a coarse sticky substance that involves fine fibers and fillers and simply adheres to fan pumps, inside piping, and to papermaking equipment and tools such as wires, felt, and rolls. Instead, it is presumed that these deposits peel off and get on the wet paper, causing papermaking defects. Usually, anion trash and micro pitch have anionically charged surfaces, so before they grow and become coarse (become pitch), a cationic water-soluble polymer called a coagulant or pitch control agent is added. However, methods for treating anion trash and micropitch by neutralizing charges are widely used. In addition, colloidal particles present in papermaking raw materials have a low surface charge, and may be weakly anionic and may be dissociated or not dissociated, so amphoteric water-soluble polymers with anionic groups introduced have also been proposed. ing.
In the application of amphoteric water-soluble polymers, especially when targeting highly hydrophobic pitch, it is being considered to introduce highly hydrophobic monomers into the polymer and process it by hydrophobic interaction. . For example, in Patent Document 1, an amphoteric monomer consisting of 5 to 95 mol% of two selected from specific cationic monomers, 5 to 50 mol% of anionic monomers, and 0 to 90 mol% of nonionic monomers is disclosed. It is described that a quaternary ammonium base-containing monomer that uses a water-soluble polymer and has a benzyl group as a cationic monomer is easily adsorbed to lipophilic pitch particles because it has a hydrophobic group.
In Patent Document 2, a water-soluble polymer having two specific cationic monomers, itaconic acid, (meth)acrylic acid, and (meth)acrylamide constitutional units, is used, and as the cationic monomer, The application of quaternized products with benzyl chloride such as dialkylaminoethyl (meth)acrylate and dialkylaminopropyl (meth)acrylamide has been described.
There is a demand for further pitch reduction effects than the application of these amphoteric water-soluble polymers as pitch control agents.

Japanese Patent Application Publication No. 2003-155688 Japanese Patent Application Publication No. 2010-077567

The object of the present invention is to develop a pitch control agent made of an amphoteric water-soluble polymer that reduces the dirt generated in the paper manufacturing process and the pitch generated in paper forming to ensure stable operation, and a pitch reduction method using the same. It is.

In order to solve the above problems, the inventors of the present invention have made extensive studies and have arrived at the invention described below. That is, it is a pitch control agent made of an amphoteric water-soluble polymer having a specific structure, composition, and physical properties, and a pitch reduction method in which the agent is added in the papermaking process before papermaking.

By applying the water-soluble polymer of the present invention to reduce dirt and pitch in the paper manufacturing process, it is possible to reduce turbidity components, micro pitch, and sticky pitch compared to conventional coagulants or pitch control agents. This reduces pitch problems in the papermaking process, enables stable operations, and achieves the production of high-quality paper products.

The amphoteric water-soluble polymer constituting the pitch control agent in the present invention has a specific structure and composition. That is, the amphoteric water-soluble polymer in the present invention contains 10 to 30 mol % of a cationic monomer represented by the following general formula (1) and 0.0 mol % of a cationic monomer represented by the following general formula (2). The structural units are 5 to 15 mol%, 0.5 to 10 mol% of an anionic monomer represented by the following general formula (3), and 45 to 89 mol% of a nonionic monomer.
General formula (1)
R ₁ is hydrogen or a methyl group, R ₂ and R ₃ are an alkyl group or alkoxy group having 1 to 3 carbon atoms, and R ₄ is an alkyl group or alkoxy group having 1 to 3 carbon atoms, and they may be the same or different. A represents oxygen or NH, B represents an alkylene group or alkoxylene group having 2 to 4 carbon atoms, and X ₁ represents an anion.
General formula (2)
R ₅ is hydrogen or a methyl group, and R ₆ and R ₇ are an alkyl group or an alkoxy group having 1 to 3 carbon atoms, and they may be the same or different. A represents oxygen or NH, B represents an alkylene group or alkoxylene group having 2 to 4 carbon atoms, and X ₁ represents an anion.
General formula (3)
R ₈ is hydrogen, Q is SO ₃ , C ₆ H ₄ SO ₃ , CONHC(CH ₃ ) ₂ CH ₂ SO ₃ , C ₆ H ₄ COO or COO, R ₉ is hydrogen or COOY ₂ , Y ₁ or Y ₂ is Represents hydrogen or a cation, respectively.

Specifically, the cationic monomer represented by the general formula (1) is a quaternized product using methyl chloride, such as dimethylaminoethyl (meth)acrylate or dimethylaminopropyl (meth)acrylamide. Examples include (meth)acryloyloxyethyltrimethylammonium chloride, (meth)acryloyloxy-2-hydroxypropyltrimethylammonium chloride, (meth)acryloylaminopropyltrimethylammonium chloride, (meth)acryloyloxyethyltriethylammonium chloride. (meth)acryloyloxy-2-hydroxypropyltriethylammonium chloride, (meth)acryloylaminopropyltriethylammonium chloride, and the like. It is also possible to combine two or more of these. The number of moles of the cationic monomer represented by general formula (1) is in the range of 10 to 30 mol%.

The cationic monomer represented by general formula (2) is a hydrophobic monomer, and specifically, quaternary monomers with benzyl chloride such as dimethylaminoethyl (meth)acrylate and dimethylaminopropyl (meth)acrylamide are used. It's a monster. Examples include (meth)acryloyloxyethyldimethylbenzylammonium chloride, (meth)acryloyloxy-2-hydroxypropyldimethylbenzylammonium chloride, (meth)acryloylaminopropyldimethylbenzylammonium chloride, (meth)acryloyloxyethyl These include diethylbenzylammonium chloride, (meth)acryloyloxy-2-hydroxypropyldiethylbenzylammonium chloride, (meth)acryloylaminopropyldiethylbenzylammonium chloride, and the like. It is also possible to combine two or more of these. The number of moles of the cationic monomer represented by general formula (2) is in the range of 0.5 to 15 mol%, preferably 1 to 10 mol%, and more preferably 1 to 5 mol%. This is because it is difficult to increase the molecular weight if there is a large amount of general formula (2). Also, this is to optimize the ionic balance between the cationic monomer and the anionic monomer.

Examples of the anionic monomer represented by the general formula (3) include vinylsulfonic acid, vinylbenzenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, methacrylic acid, acrylic acid, maleic acid, phthalic acid, and -Carboxystyrenic acid or salts thereof. Among these, acrylic acid or a salt thereof is preferred. When using dicarboxylic acids, a combination of two or more dicarboxylic acids is not preferred because the molecular weight does not improve and the pitch reduction effect tends to be suppressed. The number of moles of the anionic monomer represented by general formula (3) is in the range of 0.5 to 10 mol%, preferably 1 to 10 mol%, and even more preferably 1 to 5 mol%. .

Nonionic monomers used in the present invention include (meth)acrylamide, N,N'-dimethylacrylamide, acrylonitrile, 2-hydroxyethyl (meth)acrylate, diacetone acrylamide, N-vinylpyrrolidone, N- -Vinylformamide, N-vinylacetamide, acryloylmorpholine and the like. There is no problem even if two or more of these are combined. The number of moles of the nonionic monomer is in the range of 45 to 89 mol%.

The amphoteric water-soluble polymer in the present invention can be produced by copolymerizing a monomer mixture consisting of a cationic monomer, an anionic monomer, and a nonionic monomer. Polymerization is carried out by a conventional polymerization method after preparing an aqueous solution containing a mixture of these monomers. Polymerization is carried out by aqueous solution polymerization, water-in-oil emulsion polymerization, water-in-oil dispersion polymerization, salt water dispersion polymerization, etc. After polymerization, it is formed into any product form such as an aqueous solution, water-in-oil emulsion, salt water dispersion, or powder. can do. Among these, water-in-oil emulsion polymerization is preferred because the molecular weight can be easily adjusted and the dispersibility of the solution is relatively good.

As a method for producing a water-in-oil emulsion, known methods are applied, such as those disclosed in JP-A-55-137147, JP-A-59-130397, JP-A-10-140496, and JP-A-2011-99076. It can be manufactured as appropriate according to the method listed in the above publication. That is, a monomer mixture consisting of a cationic monomer, an anionic monomer, and a nonionic monomer is mixed with water and an oily substance consisting of a hydrocarbon immiscible with water to form a water-in-oil emulsion. An effective amount of at least one surfactant having an HLB is mixed, vigorously stirred to form a water-in-oil emulsion, and then polymerized.

In addition to the amphoteric water-soluble polymer used in the present invention, general organic coagulants and pitch control agents may be used. Examples of general organic coagulants and pitch control agents include (meth)acrylic cationic or amphoteric polymers, diallyldimethylammonium salt polymers, polyvinylamine and water-soluble polymers having polyvinylamine repeating units, and polycondensation polymers. Examples include cationic substances, ethyleneimine polymers, dicyandiamide polymers, and the like.

The molecular weight of the amphoteric water-soluble polymer in the present invention is determined by the viscosity of a 0.5% by mass salt aqueous solution, which is an indicator of molecular weight, that is, when the polymer is dissolved in a 4% by mass salt solution at a concentration of 0.5% by mass. It is defined by the viscosity measured at 25°C. The viscosity of the 0.5% by mass aqueous salt solution of the amphoteric water-soluble polymer in the present invention is in the range of 20 to 50 mPa·s, preferably 30 to 50 mPa·s. If it is lower than 20 mPa·s, no great pitch reduction effect can be obtained, and if it is higher than 50 mPa·s, the flocs will be excessive and the formation will be poor, which is not preferable. The weight average molecular weight is in the range of 3 million to 6 million.

The addition rate of the amphoteric water-soluble polymer in the present invention is 0.0001 to 0.1% by mass, preferably 0.001 to 0.1% by mass, and most preferably 0.005 to 0.1% by mass, based on the dry solid content of the pulp. It is 1% by mass. If it is less than 0.0001% by mass, it is difficult to obtain the effect of reducing turbidity and pitch, and if it exceeds 0.1% by mass, it is excessive addition and may result in excessive flocs, resulting in poor paper formation. This is not preferable since the water-soluble polymer itself may act as anion trash. Further, it may be used in combination with other papermaking chemicals such as inorganic coagulants such as PAC and sulfuric acid, sizing agents, paper strength enhancers, retention improvers, and freeness improvers. In particular, the combined effect with cationic or amphoteric retention aids or freeness improvers added downstream of the amphoteric water-soluble polymer of the present invention is promoted, which not only improves the pitch reduction effect but also improves the retention of papermaking raw materials in the wire part. In some cases, the effect of improving retention, the effect of improving freeness, and the effect of improving water extraction in the press part and dryer part can be obtained.

Next, the effect of preventing pitch trouble will be explained. Pitch, anionic substances, and turbidity components derived from waste paper, coated paper, and resin cause various pitch problems such as paper stains, defects, paper breakage, and paper machine stains. In particular, the combined involvement and growth of turbidity components and micropitch is considered to be a major cause of pitch trouble, and it is necessary to treat these. In this case, it is preferable to add the amphoteric water-soluble polymer of the present invention to the papermaking raw material before papermaking, which has a pulp dry solid content concentration of 2.0% by mass or more upstream of the papermaking process. Examples of places where it is added include machine chests, mixing chests, seed boxes, etc. where various pulps are mixed, and individual raw material pulps such as deinked waste paper raw material, coated broken paper, used magazine paper, used cardboard paper, and broken pulp may be used. . Moreover, it may not only be added directly to each raw material pulp chest, but also at the piping inlet or outlet of the raw material pulp chest.
The papermaking raw material that has been transferred from the upstream of the papermaking process with a pulp dry solids concentration of 2.0% by mass or more becomes a papermaking raw material with a pulp dry solids concentration lower than 2.0% by mass due to white water, fresh water, etc. just before the paper machine. Diluted. Generally, it is diluted to 0.5 to 1.5% by mass, and these are called inlet raw materials or headbox raw materials. It is also possible to reduce the stickiness of the sticky pitch by adding the amphoteric water-soluble polymer of the present invention to these raw materials and white water, and this is an effective addition site.

Usually, the pulp fiber surface is anionically charged, and a cationic or amphoteric coagulant or pitch control agent is used to coagulate turbidity components and pitch components together with the pulp fibers. These cationic or amphoteric coagulants or pitch control agents have relatively low molecular weight and high cation density. These weight average molecular weights are usually in the range of 100,000 to 2,000,000, and their coagulation action causes turbidity and pitch components to coagulate, disperse on the paper as fine flocs, and be discharged from the papermaking system. This is the technology.
In contrast, when the amphoteric water-soluble polymer of the present invention is added, the anionic groups in the amphoteric water-soluble polymer and hydrophobic groups are adsorbed on the pitch particle surface. Furthermore, due to the ionic balance of cationic monomers, hydrophobic monomers, and anionic monomers, and having a molecular weight within a certain range, turbidity components and pitch components are coagulated, forming fine flocs, and pitch. It is presumed that the pitch control effect is exerted by lowering the tackiness.

The turbidity component and pitch component treated with the pitch control agent ride on the wire during the papermaking process to form paper and are discharged from the papermaking system. There are no particular restrictions on the target papermaking raw materials, and they can be applied to newsprint, high-quality paper, PPC paper, coated base paper, slightly coated paper, paperboard, etc., but they contain a high proportion of various papermaking chemicals and waste paper, and contain anionic substances. The effect is particularly remarkable in paperboard raw materials such as liner and core base paper, which have low properties and a high proportion of hydrophobic pitch particle components.

EXAMPLES The present invention will be explained in detail with reference to Examples below, but the present invention is not limited to these Examples.

(Example 1)
Samples 1 to 3 were prepared as a pitch control agent comprising an amphoteric water-soluble polymer according to the present invention by a conventional method of water-in-oil emulsion polymerization. Their compositions and physical properties are shown in Table 1.

(Comparative example 1)
As comparative samples outside the scope of the amphoteric water-soluble polymer in the present invention, Samples 4 to 12 were prepared by a conventional method. Their compositions and physical properties are shown in Table 1. In addition, various organic coagulant samples A and B were prepared. The organic coagulant sample B was produced by a known method such as JP-A No. 2004-26859 and JP-A No. 2009-24125, in which a monomer mixture was added to a polymer dispersion medium of polyethyleneimine. It was obtained by dispersion polymerization. Their compositions and physical properties are shown in Table 2.

(Table 1)
Product form; EM: water-in-oil emulsion, AQ: aqueous polymer monomer; DMQ: acryloyloxyethyltrimethylammonium chloride,
DMABC: acryloyloxyethyldimethylbenzylammonium chloride,
AAC: acrylic acid, IA: itaconic acid, AAM: acrylamide

(Table 2)
Product form; AQ: aqueous solution polymer, DR: salt water dispersion polymer

(Execution test example 1)
Paperboard liner manufacturing seed raw material (pH 6.8, dry solids concentration 4.0% by mass, ash 0.80% by mass/dry solids concentration, Whatman No. 41 filter paper filtrate, Mutec PCD-03 type was used) An effect test of the pitch control agent in the present invention was conducted using a cation requirement of 41 μeq/L and a turbidity of 647 NTU.
(Turbidity measurement test)
100 mL of the raw material was collected in a beaker, and after adding 400 ppm of sample 1 in Table 1 according to the present invention in terms of dry solid content, the mixture was stirred at 200 rpm for 60 seconds. After that, Whatman No. The raw material was filtered using No. 41 filter paper, and the turbidity of the filtrate was measured using HACH Co., Ltd. Model 2100P. The same test was carried out for Sample 2 or 3 as well. The results are shown in Table 3.
(Adhesive substance measurement test)
A certain amount of the raw material was taken, and after adding 400 ppm of sample 1 in Table 1 according to the present invention in terms of dry solid content, the mixture was stirred at 200 rpm for 60 seconds. Thereafter, the raw materials were collected to have a basis weight of 150 g/m ² , and after adjusting with distilled water, they were mixed into Whatman No. Filtration was performed using No. 41 filter paper.
In the sample remaining on the wet sheet after filtration, the side not facing the filter paper was used as the measurement surface, and the sample was laminated onto a SUS board, and then the sticky substance on the wet sheet was transferred to a medium. At this time, thick filter paper was placed on the opposite side of the wet sheet to the SUS plate (thickness: 0.1 mm), and the sheet was set in a press and pressurized at 410 KPa for 5 minutes. After heating, 20 arbitrary locations on the surface to which the wet sheet was attached on the SUS board were selected, photographed with a digital camera using a stereomicroscope, and saved as images on a computer. Thereafter, target particles were extracted by adjusting the RGB value range settings using image processing software (Media Cybernetics, inc. IMAGE-PRO PLUS Ver. 5.0). The extracted deposits are extracted again under the optimal conditions of size, major/minor axis ratio, number of holes, and hole area, and fibers, other deposits, and sticky pitch are distinguished.
Regarding the extracted particles, the total area and total number of sticky pitches were measured, and the amount was calculated per 1 m ² to measure the amount of sticky material (adhesive material area). The same test was carried out for Sample 2 or 3 as well. The results are shown in Table 3.

(Comparative test example 1)
A similar test was conducted using the sample of Comparative Example 1 in Table 1 using the same papermaking raw material as in Test Example 1. The results are shown in Table 3.

(Table 3)

It can be seen that in the examples in which the pitch control agent made of the amphoteric water-soluble polymer according to the present invention was added, the turbidity and the amount of sticky substances were reduced compared to the comparative examples in which the pitch control agent outside the scope of the present invention was used. . Sample 10, in which acrylic acid and itaconic acid were used together as anionic monomers, had poorer effects than the practical test examples. It was confirmed that the pitch control effect of the amphoteric water-soluble polymer in the present invention is excellent.

(Execution test example 2)
Paperboard liner manufacturing seed raw material (pH 6.4, dry solids concentration 3.5% by mass, ash 0.83% by mass/dry solids concentration, Whatman No. 41 filter paper filtrate, Mutec PCD-03 type used) An effect test of the pitch control agent in the present invention was conducted using a cation requirement of 25 μeq/L and a turbidity of 280 NTU.
(Turbidity measurement test)
100 mL of the raw material was collected in a beaker, and after adding 400 ppm or 600 ppm of sample 1 of the present invention in terms of dry solid content, the mixture was stirred at 200 rpm for 60 seconds. After that, Whatman No. The raw material was filtered using No. 41 filter paper, and the turbidity of the filtrate was measured using HACH Co., Ltd. Model 2100P. In addition, the cation requirement of the filtrate was measured using PCD-03 model manufactured by Mutech. The results are shown in Table 4.
(Adhesive substance measurement test)
A certain amount of raw material was taken, and after adding 400 ppm or 600 ppm of dry solid content to Sample 1 of Table 1 according to the present invention, the mixture was stirred at 200 rpm for 60 seconds. Thereafter, the raw materials were collected to have a basis weight of 150 g/m ² , and after adjusting with distilled water, they were mixed into Whatman No. Filtration was performed using No. 41 filter paper.
In the sample remaining on the wet sheet after filtration, the side not facing the filter paper was used as the measurement surface, and the sample was laminated onto a SUS board, and then the sticky substance on the wet sheet was transferred to a medium. At this time, thick filter paper was placed on the opposite side of the wet sheet to the SUS plate (thickness: 0.1 mm), and the sheet was set in a press and pressurized at 410 KPa for 5 minutes. After heating, 20 arbitrary locations on the surface to which the wet sheet was attached on the SUS board were selected, photographed with a digital camera using a stereomicroscope, and saved as images on a computer. Thereafter, target particles were extracted by adjusting the RGB value range settings using image processing software (Media Cybernetics, inc. IMAGE-PRO PLUS Ver. 5.0). The extracted deposits are extracted again under the optimal conditions of size, major/minor axis ratio, number of holes, and hole area, and fibers, other deposits, and sticky pitch are distinguished.
Regarding the extracted particles, the total area and total number of sticky pitches were measured, and the amount was calculated per 1 m ² to measure the amount of sticky material (adhesive material area). The results are shown in Table 4.

(Comparative test example 2)
A similar test was conducted using the same papermaking raw material as in Test Example 2, and Comparative Example 1 in Table 1 and the sample in Table 2. The results are shown in Table 4.

(Table 4)

In the practical test examples in which the pitch control agent made of an amphoteric water-soluble polymer according to the present invention was added, turbidity and the amount of sticky substance were lower than in the comparative examples in which a pitch control agent outside the scope of the present invention was used. I understand. In particular, it was confirmed that the amphoteric water-soluble polymer of the present invention is effective against adhesive pitch, as the degree of reduction in adhesive substances is large. In comparative test examples, even when the turbidity was relatively low, the amount of sticky matter did not decrease.

(Execution test example 3)
Paperboard liner manufacturing seed material (pH 6.5, dry solids concentration 4.3% by mass, ash 0.6% by mass/dry solids concentration, Whatman No. 41 filter paper filtrate, Mutec PCD-03 type was used) An effect test of the pitch control agent in the present invention was conducted using a cation requirement of 105 μeq/L and a turbidity of 660 NTU.
(turbidity, cation requirement measurement test)
100 mL of the raw material was collected in a beaker, and after adding 50 or 100 ppm of sample 1 in Table 1 in terms of solid content to the paper sample, the mixture was stirred at 200 rpm for 60 seconds. After that, Whatman No. The sample was filtered using No. 41 filter paper, and the turbidity of the filtrate was measured using HACH Co., Ltd. Model 2100P. In addition, the cation requirement of the filtrate was measured using PCD-03 model manufactured by Mutech. The results are shown in Table 5.

(Comparative test example 3)
A similar test was conducted using the same papermaking raw material as in Test Example 3, and Comparative Example 1 in Table 1 and the sample in Table 2. The results are shown in Table 5.

(Table 5)

In the examples in which the pitch control agent made of an amphoteric water-soluble polymer according to the present invention was added, the turbidity and the amount of cations required were lower than in the comparative examples in which a pitch control agent outside the scope of the present invention was used. I understand. In comparative test examples, the turbidity value did not show any decrease even when the cation requirement was relatively low.

By adding the pitch control agent made of the amphoteric water-soluble polymer of the present invention to papermaking raw materials, the effect of reducing turbidity components, sticky pitch, and anion trash was obtained, and it was confirmed that it is effective as a pitch control agent. .

Claims (4)

10 to 30 mol% of a cationic monomer represented by the following general formula (1), 0.5 to 15 mol% of a cationic monomer represented by the following general formula (2), and the following general formula (3) It is an amphoteric water-soluble polymer whose constituent units are 0.5 to 10 mol% of an anionic monomer and 45 to 89 mol% of a nonionic monomer, and the 4 mass of the amphoteric water-soluble polymer is A pitch control agent comprising an amphoteric water-soluble polymer having a viscosity measured at 25° C. in the range of 30 to 50 mPa·s when dissolved in saline solution at a polymer concentration of 0.5% by mass.
General formula (1)
R ₁ is hydrogen or a methyl group, R ₂ and R ₃ are an alkyl group or alkoxy group having 1 to 3 carbon atoms, and R ₄ is an alkyl group or alkoxy group having 1 to 3 carbon atoms, and they may be the same or different. A represents oxygen or NH, B represents an alkylene group or alkoxylene group having 2 to 4 carbon atoms, and X ₁ represents an anion.
General formula (2)
R ₅ is hydrogen or a methyl group, and R ₆ and R ₇ are an alkyl group or an alkoxy group having 1 to 3 carbon atoms, and they may be the same or different. A represents oxygen or NH, B represents an alkylene group or alkoxylene group having 2 to 4 carbon atoms, and X ₁ represents an anion.
General formula (3)
R ₈ is hydrogen, Q is SO ₃ , C ₆ H ₄ SO ₃ , CONHC(CH ₃ ) ₂ CH ₂ SO ₃ , C ₆ H ₄ COO or COO, R ₉ is hydrogen or COOY ₂ , Y ₁ or Y ₂ is Represents hydrogen or a cation, respectively. The pitch control agent according to claim 1, wherein the form of the amphoteric water-soluble polymer is a water-in-oil emulsion. 10 to 30 mol% of a cationic monomer represented by the following general formula (1), 0.5 to 15 mol% of a cationic monomer represented by the following general formula (2), and the following general formula (3) It is an amphoteric water-soluble polymer whose constituent units are 0.5 to 10 mol% of an anionic monomer and 45 to 89 mol% of a nonionic monomer, and the 4 mass of the amphoteric water-soluble polymer is An amphoteric water-soluble polymer having a viscosity in the range of 30 to 50 mPa·s measured at 25°C when dissolved in saline solution at a polymer concentration of 0.5% by mass is used in the papermaking process before papermaking. A pitch reduction method characterized by adding to.
General formula (1)
R ₁ is hydrogen or a methyl group, R ₂ and R ₃ are an alkyl group or alkoxy group having 1 to 3 carbon atoms, and R ₄ is an alkyl group or alkoxy group having 1 to 3 carbon atoms, and they may be the same or different. A represents oxygen or NH, B represents an alkylene group or alkoxylene group having 2 to 4 carbon atoms, and X ₁ represents an anion.
General formula (2)
R ₅ is hydrogen or a methyl group, and R ₆ and R ₇ are an alkyl group or an alkoxy group having 1 to 3 carbon atoms, and they may be the same or different. A represents oxygen or NH, B represents an alkylene group or alkoxylene group having 2 to 4 carbon atoms, and X ₁ represents an anion.
General formula (3)
R ₈ is hydrogen, Q is SO ₃ , C ₆ H ₄ SO ₃ , CONHC(CH ₃ ) ₂ CH ₂ SO ₃ , C ₆ H ₄ COO or COO, R ₉ is hydrogen or COOY ₂ , Y ₁ or Y ₂ is Represents hydrogen or a cation, respectively. 4. The pitch reduction method according to claim 3 , wherein the pitch is a sticky pitch.