Pitch trouble suppression method

Abstract

To provide a pitch trouble suppression method, that is useful for suppressing / preventing pitch stains in the papermaking process.SOLUTION: The pitch trouble suppression method is a pitch trouble suppression method for controlling the size of a pitch contained in the pulp slurry in the pulping step and / or the preparation step to suppress the occurrence of pitch trouble in the papermaking process, including an oxidizing agent addition step in which an oxidizing agent is added to at least one location pulp slurry in the pulping step and the preparation step so that the average particle size of the pitch contained in the pulp slurry is less than 150 μm, and / or a pitch dispersing agent addition step in which a pitch dispersing agent is added to at least one location pulp slurry in the pulping step and the preparation step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for suppressing pitch problems in a papermaking process. [Background technology]

[0002] Conventionally, problems caused by pitch have occurred in the papermaking process (particularly the papermaking process), and various chemicals have been developed to suppress and prevent this. Pitch is a water-insoluble adhesive substance that is primarily composed of organic matter derived from natural resins and gums liberated from wood, pulp, and paper, as well as additives used in the paper and pulp manufacturing process.

[0003] Generally, pitch is dispersed in a colloidal state in the process water (pulp slurry or white water) used in the paper and pulp manufacturing process. However, it is thought that some external action, such as a large shear force, a sudden change in pH, or the addition of excessive amounts of aluminum sulfate (aluminum sulfate), can destroy this colloidal state, causing the particles to aggregate and grow larger. Due to its adhesiveness, this agglomerated and enlarged pitch not only adheres to paper and pulp, but also to manufacturing equipment such as fan pumps, pipes, chests, wires, felts, and rolls, but also peels off and re-adheres to the paper and pulp.The resulting stains and defects on the paper reduce the quality of paper products, and the resulting paper breaks cause problems such as reduced productivity and workability.

[0004] In recent years, the diversification of paper has led to an increase in the types of additives and their amounts used, and the proportion of recycled paper used has also increased. As a result, the water used in the papermaking process has become more closed, and the occurrence of pitch problems has become more frequent than ever before, and the forms in which they occur have become more complex. For example, problems are increasing not only with pitch derived from conventional mechanical pulps such as ground pulp (GP) and thermomechanical pulp (TMP), or pitch derived from chemical pulps such as kraft pulp (KP), but also with pitch derived from recycled paper. Examples of pitch derived from recycled paper include synthetic resins such as magazine spine glue (polyvinyl acetate) and labels (acrylic adhesive). In addition, in order to improve productivity, the size of equipment has increased and papermaking speeds have increased, which, combined with other factors, has resulted in the problem of pitch contamination of the wire part, press part rolls, blankets, and blanket suction boxes.

[0005] As methods for suppressing such pitch problems, methods such as adsorbing pitch components onto inorganic compounds such as fine talc, fixing pitch particles to pulp fibers before they aggregate, dispersing pitch particles, and combinations of these methods have been proposed and put to practical use.

[0006] For example, Patent Document 1 discloses a pitch disorder inhibitor for use in paper and pulp manufacturing processes, which contains as active ingredients a cationic polymer selected from polydiallyldimethylammonium salts having a molecular weight of 20,000 to 100,000 and epichlorohydrin-dialkylamine condensates having a molecular weight of 20,000 to 100,000, and a nonionic surfactant in which ethylene oxide or ethylene oxide and propylene oxide are added to a higher aliphatic amine. However, conventional additives and methods are not sufficient in preventing pitch problems, and more effective agents and methods are desired.

[0007] Furthermore, Patent Document 2 describes a method for suppressing pitch damage in a paper manufacturing system in which paper is made from paper raw materials, and discloses that pitch adhesion can be suppressed by performing a process to suppress an increase in calcium ion concentration in the water system of the paper manufacturing system.

[0008] Patent Document 3 describes a method for controlling pitch in a papermaking process using a combination of lipase and an oxidizing agent, thereby controlling deposit-forming pollutants including pitch or other fiber components. It also describes that contacting fibers with a combination of lipase and at least one peroxide-free oxidizing agent liberates organic pollutants from the fibers, thereby controlling deposit-forming pollutants.

[0009] As described above, methods for suppressing pitch damage in the papermaking process for producing paper have been studied in the past, but little research has been done on pulp slurries in which pitch damage is suppressed in the papermaking process, i.e., pulp slurries containing pitch controlled to such an extent that pitch damage does not occur in the papermaking process. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-044067 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-226032 [Patent Document 3] Patent No. 6084689 [Non-patent literature]

[0011] [Non-Patent Document 1] "Pitch Reduction Methods in Paperboard Systems," Journal of the Japan Paper and Pulp Technology Association, Vol. 58, No. 4, pp. 468-477, April 2004 Summary of the Invention [Problem to be solved by the invention]

[0012] Therefore, an object of the present invention is to provide a method for suppressing pitch problems that is useful for suppressing and preventing pitch staining in the papermaking process. [Means for solving the problem]

[0013] Generally, the papermaking process is divided into 1) a pulping process, 2) a preparation process in which chemicals are blended, 3) a papermaking process, and 4) a finishing process. Conventional methods for suppressing pitch damage have been proposed, in which a pitch control agent is added to the pulp slurry in the preparation process and the papermaking process to suppress pitch damage that occurs mainly in the papermaking process. However, such methods are not sufficiently effective in preventing pitch damage in the papermaking process, and a more effective method for suppressing pitch damage is desired.

[0014] As a result of extensive research to solve the above problems, the present inventors have found that the occurrence of pitch problems in the papermaking process can be suppressed by controlling the particle size of pitch in the pulp slurry before it is introduced into the papermaking process so that it does not exceed a specific size.The present inventors have also found that adding a specific oxidizing agent to the pulp slurry in at least one of the pulping and preparation processes, and / or adding a pitch dispersant to the pulp slurry in at least one of the pulping and preparation processes, can suppress the pitch from growing larger than a specific size, thereby achieving an excellent effect in suppressing and preventing pitch contamination in the papermaking process, and have completed the present invention. The inventors also discovered that the occurrence of pitch problems during the papermaking process can be suppressed by controlling the particle size of the pitch in the pulp slurry after it is introduced into the papermaking process so that it is below a specific size. They then discovered that adding a specific oxidizing agent and a pitch dispersant to the pulp slurry at at least one point during the papermaking process reduces the pitch to a specific size or below, thereby demonstrating an excellent effect of suppressing and preventing pitch contamination during the papermaking process, and thus completed the present invention. The present inventors have also found that the occurrence of pitch problems in the papermaking process can be suppressed by controlling the particle size of pitch in the pulp slurry before and / or after its introduction into the papermaking process to be equal to or less than a specific size. They have discovered that adding a specific oxidizing agent and / or pitch dispersant to the pulp slurry in at least one of the pulping and / or preparation processes, and further adding a specific oxidizing agent and / or pitch dispersant to the pulp slurry in at least one of the papermaking processes, reduces the pitch in the pulp slurry in the papermaking process to a specific size or less, thereby achieving an excellent effect in suppressing and preventing pitch contamination in the papermaking process, and have completed the present invention.

[0015] The present invention is a pitch damage suppression method for suppressing the occurrence of pitch damage in a papermaking process by controlling the size of pitch contained in a pulp slurry in a pulping process and / or a paper preparation process, and is characterized by comprising an oxidant addition step of adding an oxidant to pulp slurry at least in one of the pulping process and the paper preparation process so that the average particle size of the pitch contained in the pulp slurry is less than 150 μm, and / or a pitch dispersant addition step of adding a pitch dispersant to pulp slurry at least in one of the pulping process and the paper preparation process. The present invention also provides a pitch damage suppression method for controlling the size of pitch contained in a pulp slurry in a papermaking process and suppressing the occurrence of pitch damage in the papermaking process, the pitch damage suppression method comprising: an oxidant addition step of adding an oxidant to the pulp slurry at least at one location in the papermaking process so that the average particle size of the pitch contained in the pulp slurry is less than 150 μm; and a pitch dispersant addition step of adding a pitch dispersant to the pulp slurry at least at one location in the papermaking process. The present invention also provides a pitch damage suppression method for controlling the size of pitch contained in pulp slurry in the pulping process and / or the preparation process and the papermaking process, thereby suppressing the occurrence of pitch damage in the papermaking process, the pitch damage suppression method comprising: a first oxidant addition step of adding a first oxidant to pulp slurry in at least one of the pulping process and the preparation process, and / or a first pitch dispersant addition step of adding a first pitch dispersant to pulp slurry in at least one of the pulping process and the preparation process, so that the average particle size of the pitch contained in the pulp slurry in the papermaking process is less than 150 μm; and further comprising a second oxidant addition step of adding a second oxidant to pulp slurry in at least one of the papermaking process and the preparation process, and / or a second pitch dispersant addition step of adding a second pitch dispersant to pulp slurry in at least one of the papermaking process. The oxidizing agent is preferably at least one selected from the group consisting of hypochlorite, chlorite, chlorine dioxide, hydrogen peroxide, and bound halogen. Furthermore, the first oxidizing agent and the second oxidizing agent are preferably at least one selected from the group consisting of hypochlorite, chlorite, chlorine dioxide, hydrogen peroxide, and bound halogen. In the pitch dispersant addition step, the pitch dispersant is preferably added to a pulp slurry having a residual chlorine concentration of 0.5 mg / L or more and 30 mg / L or less. In the first pitch dispersant addition step and the second pitch dispersant addition step, the pitch dispersant is preferably added to a pulp slurry having a residual chlorine concentration of 0.5 mg / L or more and 30 mg / L or less. Furthermore, the pitch disorder suppression method of the present invention preferably includes the oxidizing agent addition step and the pitch dispersant addition step, and the oxidizing agent is at least one selected from the group consisting of hypochlorite, chlorite, chlorine dioxide, and bound halogen. The pitch dispersant is preferably at least one selected from the group consisting of surfactants, cationic polymers, and organic solvents. The first and second pitch dispersants are preferably at least one selected from the group consisting of surfactants, cationic polymers, and organic solvents. The present invention will be described in detail below.

[0016] The present invention is a pitch damage suppression method for controlling the size of pitch contained in pulp slurry in the pulping process and / or the preparation process, and suppressing the occurrence of pitch damage in the papermaking process, and the pitch damage suppression method includes an oxidant addition step of adding an oxidant to pulp slurry at least at one point in the pulping process and the preparation process, and / or a pitch dispersant addition step of adding a pitch dispersant to pulp slurry at least at one point in the pulping process and the preparation process, so that the average particle size of the pitch contained in the pulp slurry is less than 150 μm. By providing an oxidant addition step in which an oxidant is added to the pulp slurry at at least one of the pulping process and the preparation process, the pitch size in the pulp slurry can be reduced, thereby suppressing pitch enlargement and the occurrence of pitch problems in the papermaking process. Furthermore, by providing a pitch dispersant addition step in which a pitch dispersant is added to the pulp slurry at at least one of the pulping process and the preparation process, the dispersibility of the pitch in the pulp slurry can be improved before the pitch size in the pulp slurry increases, and pitch aggregation is suppressed, so that the pitch can be maintained at a small size without increasing in size, thereby suppressing the occurrence of pitch problems in the papermaking process.

[0017] The present invention also provides a pitch damage suppression method for controlling the size of pitch contained in a pulp slurry in a papermaking process and suppressing the occurrence of pitch damage in the papermaking process, the pitch damage suppression method comprising: an oxidant addition step of adding an oxidant to the pulp slurry at least at one location in the papermaking process so that the average particle size of the pitch contained in the pulp slurry is less than 150 μm; and a pitch dispersant addition step of adding a pitch dispersant to the pulp slurry at least at one location in the papermaking process. By providing an oxidant addition step of adding an oxidant to the pulp slurry at at least one location in the papermaking process, the pitch size in the pulp slurry in the papermaking process can be reduced, thereby suppressing pitch enlargement and promoting pitch reduction, thereby suppressing the occurrence of pitch problems in the papermaking process. Furthermore, by providing a pitch dispersant addition step in which a pitch dispersant is added to the pulp slurry at at least one location in the papermaking process, the dispersibility of the pitch in the pulp slurry in the papermaking process can be improved before the pitch size in the pulp slurry increases, and pitch aggregation is suppressed, so that the pitch can be maintained at a small size without increasing in size, thereby suppressing the occurrence of pitch problems in the papermaking process.

[0018] The present invention also provides a pitch damage suppression method for controlling the size of pitch contained in pulp slurry in the pulping process and / or the preparation process and the papermaking process, thereby suppressing the occurrence of pitch damage in the papermaking process, the pitch damage suppression method comprising: a first oxidant addition step of adding a first oxidant to pulp slurry in at least one of the pulping process and the preparation process, and / or a first pitch dispersant addition step of adding a first pitch dispersant to pulp slurry in at least one of the pulping process and the preparation process, so that the average particle size of the pitch contained in the pulp slurry in the papermaking process is less than 150 μm; and further comprising a second oxidant addition step of adding a second oxidant to pulp slurry in at least one of the papermaking process and the preparation process, and / or a second pitch dispersant addition step of adding a second pitch dispersant to pulp slurry in at least one of the papermaking process. By providing a first oxidant addition step of adding an oxidant to the pulp slurry at at least one location in the pulping process and / or the preparation process, the pitch size in the pulp slurry can be reduced, and pitch enlargement can be suppressed. Furthermore, by providing a first pitch dispersant addition step of adding a pitch dispersant to the pulp slurry at at least one location in the pulping process and / or the preparation process, the dispersibility of the pitch in the pulp slurry can be improved before the pitch size in the pulp slurry increases, pitch aggregation is suppressed, and the pitch can be maintained at a small size without increasing in size. Furthermore, by providing a second oxidant addition step of adding an oxidant to the pulp slurry at at least one location in the papermaking process and / or a second pitch dispersant addition step of adding a pitch dispersant to the pulp slurry at at least one location in the papermaking process, the pitch size in the pulp slurry in the papermaking process can be reduced and / or the dispersibility of the pitch can be improved before the pitch size increases. This suppresses the aggregation of pitch in the pulp slurry during the papermaking process, and allows the pitch to be maintained at a small size without becoming enlarged.

[0019] The pitch disorder suppression method of the present invention may be either a method for controlling the pitch size contained in a pulp slurry in a pulping process and / or a preparation process, or a method for controlling the pitch size contained in a pulp slurry in a papermaking process, or a combination thereof. The terms used in the pitch disorder suppression method of the present invention are common to the method for controlling the pitch size contained in a pulp slurry in a pulping process and / or a preparation process, and / or the method for controlling the pitch size contained in a pulp slurry in a papermaking process. Note that, in this specification, the compounds, addition methods, and preferred embodiments used in the oxidant addition step, the first oxidant addition step, and the second oxidant addition step are common. Therefore, in the following description, the term "oxidant addition step" will be used, and the oxidant, first oxidant, and second oxidant used herein will be referred to as "oxidants." Furthermore, the compounds, addition methods, and preferred embodiments used in the pitch dispersant addition step, the first pitch dispersant addition step, and the second pitch dispersant addition step are common. Therefore, in the following description, all steps will be expressed as a pitch dispersant addition step, and the pitch dispersant, first pitch dispersant, and second pitch dispersant used here will be expressed as pitch dispersants. In this specification, the papermaking process includes a pulping process, a preparation process, and a papermaking process.

[0020] In the method for suppressing pitch problems of the present invention, the raw material for pulping may be either wood or waste paper.

[0021] For example, when waste paper is used as the raw material, the waste paper pulping process primarily consists of a disintegration process, a rough screening and refining process, and a dewatering and washing process. It may also include a deinking process, which removes ink from the waste paper, and a bleaching process, which chemically bleaches the pulp. Specifically, each process is: disintegration (pulpering), in which the raw material waste paper is mixed with water and mechanically turned into pulp slurry; rough screening (dust removal), in which foreign matter is removed from the waste paper; deinking, in which ink components are removed by adding a deinking agent; refining, in which foreign matter is separated from the pulp using a screen; washing, in which the pulp slurry is washed with water; dewatering, in which the pulp is dewatered; and bleaching, in which a bleaching agent is added to bleach the pulp. The water used in each of the above processes and the wastewater discharged are called white water. Furthermore, the mixture of the raw material waste paper and white water in the pulpering process is called pulp slurry.

[0022] Furthermore, when wood is used as the raw material, for example, the pulping process for chemical pulp mainly comprises a wood-cutting process, a cooking process, a screening and washing process, and a dewatering process. It may also include a bleaching process, in which the pulp is chemically bleached. In the cooking process, chemicals are added to the chips, and the chips are boiled at high temperature and pressure to dissolve the resin (lignin), extract the fiber, and turn the chips into pulp. In other words, the pulp raw material goes through a cooking process to become pulp slurry. The pulping process for mechanical pulp also comprises a wood-breaking process, a dust removal process, and a concentration process. It may also include a bleaching process, in which the pulp is chemically bleached. In the above process, the pulp is mechanically broken down into fibers to become pulp slurry.

[0023] In the pitch defect suppression method of the present invention, the oxidizing agent addition step and / or pitch dispersant addition step preferably include adding the oxidizing agent and / or pitch dispersant to the pulp slurry in at least one of the devices that apply mechanical shear to the pulp slurry and / or to the pulp slurry upstream of the device. By adding the oxidizing agent and / or pitch dispersant to at least one of the devices that apply mechanical shear and / or upstream thereof, the oxidizing agent and / or pitch dispersant and the pulp slurry are thoroughly stirred and mixed, and the pitch component contained in the pulp slurry is thoroughly contacted with the oxidizing agent and / or pitch dispersant, promoting the micronization and / or dispersibility of the pitch component, and maintaining the pitch component in a state where it remains stably dispersed at a microscopic size. This further suppresses the occurrence of pitch defects in the papermaking process. In the present invention, the terms "upstream" and "downstream" are determined by the flow direction of the pulp slurry or white water in the piping or equipment, with the direction in which the pulp slurry or white water flows being downstream and the opposite direction being upstream. For example, in a pulping raw material line, the side closer to the pulping raw material is upstream. Also, in a white water supply line for supplying white water, the side closer to the white water pit is upstream.

[0024] In the present invention, equipment that applies mechanical shear refers to equipment that agitates pulp slurry at a rotational speed of 50 rpm or more and 3000 rpm or less, and refers to a location where the stress acting on the pulp slurry inside the equipment is greater than the stress acting on the pulp slurry flowing through the piping. Specific examples include pulpers, refiners, screw presses, double separators, selection screens, rotary screens, washers, thickeners, and fan pumps. Specific preferred examples of equipment include pulpers, refiners, and fan pumps.

[0025] Furthermore, in the present invention, the oxidizing agent addition step and / or pitch dispersant addition step are preferably located upstream of the drainage line. As described above, adding an oxidizing agent and / or pitch dispersant to the pulp slurry upstream of at least one of the mechanical shearing devices promotes the micronization and / or dispersion of the pitch component in the pulp slurry. The dispersed pitch component is then discharged together with white water through the drainage line from the raw material line for the pulping process and the preparation process, thereby reducing the amount of pitch component in the pulp slurry. This allows for more effective prevention of pitch problems in the papermaking process.

[0026] The drainage line refers to a line that discharges white water from the raw material line through which the pulp slurry flows to the outside of the pulping process, preparation process, and papermaking process, and does not include a line that recovers white water for reuse. Furthermore, as a method for discharging the pitch component from the pulping process and the preparation process to the outside of the system, in addition to the method of discharging the pitch component together with white water from the raw material line via a drainage line as described above, there is also a method of transferring the pitch component together with pulp slurry from the pulping process and the preparation process to the papermaking process that follows, but the above-mentioned "drainage line" corresponds to the line that discharges the pitch component together with white water from the raw material line.

[0027] The specific oxidizing agent used in the present invention is preferably at least one selected from the group consisting of hypochlorite, chlorite, chlorine dioxide, hydrogen peroxide, and bound halogen.

[0028] Specific examples of the hypochlorite salt include sodium hypochlorite, potassium hypochlorite, and calcium hypochlorite, and in the present invention, these salts can be used alone or in combination of two or more.

[0029] Specific examples of the chlorite salt include sodium chlorite, potassium chlorite, and calcium chlorite, and in the present invention, these salts can be used alone or in combination of two or more.

[0030] Chlorine dioxide is an extremely unstable chemical substance, making its storage and transportation extremely difficult. Therefore, it is preferable to produce (generate) chlorine dioxide on-site by a known method and adjust the concentration to the desired level before use. For example, chlorine dioxide can be produced by the following reaction, and a commercially available chlorine dioxide generator (device) can also be used. (1) Reaction of sodium hypochlorite with hydrochloric acid and sodium chlorite NaOCl+2HCl+2NaClO2→ 2ClO2+3NaCl+H2O (2) Reaction of sodium chlorite with hydrochloric acid 5NaClO2+4HCl → 4ClO2+5NaCl+2H2O (3) Reaction with sodium chlorate, hydrogen peroxide, and sulfuric acid 2NaClO3+H2O2+H2SO4→ 2ClO2+Na2SO4+O2+2H2O

[0031] The bound halogen includes bound chlorine and bound bromine, and specifically, monochloramine and / or monobromamine are preferred. The monochloramine and monobromamine are mild oxidizing agents that are produced by a reaction such as OCl-(Br-) + NH4 + → NH2Cl(Br) + HO. For example, monochloramine can be produced by mixing sodium hypochlorite with an ammonium compound, and specific examples of the ammonium compound include ammonium sulfate, ammonium bromide, ammonium chloride, and ammonium sulfamate, which can be used alone or in combination of two or more. In one or more embodiments, the molar ratio of sodium hypochlorite to the ammonium compound is preferably 1:1 to 1:2, calculated as the molar ratio of the residual chlorine amount to nitrogen.

[0032] In the present invention, the amount of oxidizing agent added may be appropriately determined depending on the state of the pulp slurry, etc., but it is generally preferable to add the oxidizing agent to the pulp slurry at a location where mechanical shear is applied, such as a pulper in the pulping process in the case of recycled paper pulp, or at a location where mechanical shear is applied, such as the stage before the washing process in the case of chemical pulp or mechanical pulp, so that the oxidizing agent concentration in the pulp slurry is 5 ppm or more and 100 ppm or less, more preferably 10 ppm or more and 80 ppm or less, and even more preferably 50 ppm or less from an economical standpoint. In addition, the oxidizing agent is preferably added so that the residual chlorine content in the pulp slurry (in the case of monobromamine, the residual chlorine content is converted to a value) is 0.5 mg / L or more and 30 mg / L or less, more preferably 1 mg / L or more and 30 mg / L or less, and from an economical standpoint, it is even more preferable to add it so that the residual chlorine content is 1 mg / L or more and 10 mg / L or less, or 1 mg / L or more and 5 mg / L or less.

[0033] Furthermore, it is particularly preferable that the oxidizing agent used in the pitch disorder suppression method of the present invention contains a bound halogen, because this maintains the amount of residual chlorine in the pulp slurry and thus maintains the pitch disorder suppression effect.

[0034] In the present invention, the term "residual chlorine amount" means "equivalent residual chlorine amount value" in the case of monobromamine.

[0035] The pitch dispersant used in the present invention is preferably at least one selected from the group consisting of surfactants, cationic polymers, and organic solvents, and more preferably two or more selected from the group consisting of surfactants, cationic polymers, and organic solvents, in order to reduce aggregation and adhesion of the pitch components.

[0036] The surfactant is preferably at least one selected from the group consisting of cationic surfactants, nonionic surfactants, and amphoteric surfactants.

[0037] Examples of the cationic surfactant include quaternary ammonium compounds such as alkyldimethylbenzylammonium salts and dialkyldimethylammonium salts having an alkyl group with 10 to 18 carbon atoms, and dihydroxyethylalkylamines having 10 to 18 carbon atoms. Specific examples include decyldimethylbenzyl ammonium chloride, decyldimethylbenzyl ammonium bromide, dodecyldimethylbenzyl ammonium chloride, dodecyldimethylbenzyl ammonium bromide, tetradecyldimethylbenzyl ammonium chloride, tetradecyldimethylbenzyl ammonium bromide, hexadecyldimethylbenzyl ammonium chloride, hexadecyldimethylbenzyl ammonium bromide, octadecyldimethylbenzyl ammonium chloride, octadecyldimethylbenzyl ammonium bromide, lauryldimethylbenzyl ammonium chloride, lauryldimethylbenzyl ammonium bromide, dihydroxyethylstearylamine, and dihydroxyethyloleylamine. In the present invention, these may be used alone or in combination of two or more. Among these, alkyldimethylbenzylammonium salts having an alkyl group with 12 to 18 carbon atoms and dihydroxyethylalkylamines having 12 to 18 carbon atoms are preferred in terms of the effect of improving the dispersibility of the pitch component in the pulp slurry, and alkyldimethylbenzylammonium chlorides having an alkyl group with 12 to 18 carbon atoms and dihydroxyethylstearylamine are particularly preferred.

[0038] Examples of the nonionic surfactant include an adduct of higher aliphatic amine with ethylene oxide or an adduct of ethylene oxide and propylene oxide, and an adduct of higher alcohol ether with ethylene oxide or an adduct of ethylene oxide and propylene oxide.

[0039] As the adduct of ethylene oxide or ethylene oxide and propylene oxide with a higher aliphatic amine, an adduct in which 10 to 30 moles of ethylene oxide or 0 to 15 moles of propylene oxide is added to a saturated or unsaturated aliphatic amine having 10 to 20 carbon atoms is preferred in terms of the effect of improving the dispersibility of pitch components, and an adduct in which 10 to 20 moles of ethylene oxide or 0 to 5 moles of propylene oxide is added is more preferred.

[0040] Examples of saturated or unsaturated aliphatic amines having 10 to 20 carbon atoms include decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, oleylamine, tallow alkylamine, and coconut alkylamine. Here, tallow alkylamine and coconut alkylamine mean a mixture of amines (mixed alkylamines) whose main component is a linear or branched, saturated or unsaturated aliphatic hydrocarbon group having 12 to 20 carbon atoms, produced by known means from coconut oil, coconut fat, tallow, etc.

[0041] Particularly preferred adducts of higher aliphatic amines with ethylene oxide or ethylene oxide and propylene oxide are stearylamine-ethylene oxide 20 mole adduct and beef tallowamine-ethylene oxide-propylene oxide adduct in an adduct ratio of 85 / 15 (ethylene oxide 31 moles propylene oxide 4 moles).

[0042] As the adduct of ethylene oxide or ethylene oxide and propylene oxide with a higher alcohol ether, an adduct in which 4 to 50 moles of ethylene oxide or 0 to 15 moles of propylene oxide is added to a saturated or unsaturated fatty acid having 12 to 18 carbon atoms is preferred in terms of improving the dispersibility of pitch components, and examples thereof include polyoxyethylene alkyl phenol ethers, polyoxyethylene alkyl ethers, and fatty acid esters of polyoxyethylene glycol.

[0043] Specific examples of the adduct of ethylene oxide or ethylene oxide and propylene oxide with higher alcohol ether include polyoxyethylene lauryl ether, polyoxyethylene tetradecyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene octyldodecyl ether, polyoxyethylene lauryl phenyl ether, polyoxyethylene tetradecyl phenyl ether, polyoxyethylene cetyl phenyl ether, polyoxyethylene stearyl phenyl ether, polyoxyethylene oleyl phenyl ether, and polyoxyethylene octyldodecyl phenyl ether. Among these, the use of polyoxyethylene alkyl phenol ether is preferred, and polyoxyethylene nonyl phenol ether with 10 to 16 moles of ethylene oxide added is particularly preferred.

[0044] Examples of the amphoteric surfactant include alkyldimethylaminoacetic acid betaine having a saturated or unsaturated alkyl group having 10 to 18 carbon atoms. Specific examples include decyldimethylaminoacetic acid betaine, dodecyldimethylaminoacetic acid betaine, tetradecyldimethylaminoacetic acid betaine, hexadecyldimethylaminoacetic acid betaine, octadecyldimethylaminoacetic acid betaine, lauryldimethylaminoacetic acid betaine, and stearyldimethylaminoacetic acid betaine, and in the present invention, these can be used alone or in combination of two or more. Among these, lauryldimethylaminoacetic acid betaine is preferred in terms of its effect of improving the dispersibility of pitch components in the pulp slurry.

[0045] Examples of the cationic polymer include water-soluble aluminum compounds, polydiallyldimethylammonium salts, and epichlorohydrin-dialkylamine condensates. Specific examples of the water-soluble aluminum compound include polyaluminum chloride and polyhydroxyammonium chloride. Specific examples of the polydiallyldimethylammonium salt include polydiallyldimethylammonium chloride, polydiallyldimethylammonium bromide, polydiallyldimethylammonium nitrate, polydiallyldimethylammonium sulfate, and polydiallyldimethylammonium phosphate, each having a molecular weight of 20,000 to 100,000. Of these, polydiallyldimethylammonium chloride is particularly preferred. Specific examples of the epichlorohydrin-dialkylamine condensate include epichlorohydrin dimethylamine condensates and epichlorohydrin diethylamine condensates having a molecular weight of 10,000 to 200,000. In the present invention, these can be used alone or in combination of two or more. Among these, polyaluminum chloride and / or polydiallyldimethylammonium chloride having a molecular weight of 20,000 to 100,000 are more preferred in terms of the effect of improving the dispersibility of the pitch component in the pulp slurry.

[0046] Examples of the organic solvent include higher fatty acid alkylamides, glycols, glycol ethers, dimethyl sulfoxide, and tetrahydrofuran. Specific examples of the higher fatty acid alkylamides include tall oil fatty acid dimethylamides. Specific examples of the glycol include ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol. Specific examples of the glycol ether include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, ethylene glycol monohexyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propoxypropanol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, and tripropylene glycol methyl ether. In the present invention, these may be used alone or in combination of two or more. Among these, tall oil fatty acid dimethylamide, ethylene glycol, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, etc. are preferred in terms of the effect of improving the dispersibility of the pitch component in the pulp slurry.

[0047] The oxidizing agent and / or pitch dispersant used in the present invention is preferably at least two selected from the group consisting of the above-mentioned oxidizing agents, surfactants, cationic polymers, and organic solvents. While preferred combinations vary depending on the type of pitch and the composition of the pulp slurry, a combination of an oxidizing agent and a nonionic surfactant, a combination of an oxidizing agent, a nonionic surfactant, and a cationic polymer, or a combination of an oxidizing agent and a cationic polymer is more preferred. Specifically, the oxidizing agent is preferably at least one selected from the group consisting of hypochlorite, chlorine dioxide, and monochloramine, and the cationic surfactant is preferably lauryl dimethyl benzyl ammonium chloride and / or dihydroxyethyl stearylamine. The nonionic surfactant is preferably polyoxyethylene stearylamine with 10 to 30 moles of ethylene oxide added and / or polyoxyethylene nonylphenol ether with 10 to 16 moles of ethylene oxide added. The amphoteric surfactant is preferably lauryl dimethyl amino acetate betaine. The cationic polymer is preferably polyaluminum chloride and / or polydiallyl dimethyl ammonium chloride with a molecular weight of 20,000 to 100,000. The organic solvent is preferably at least one selected from tall oil fatty acid dimethylamide, ethylene glycol, ethylene glycol monobutyl ether, and diethylene glycol monobutyl ether.

[0048] Particularly preferred combinations of at least two pitch dispersants include a combination of polyoxyethylene stearylamine and polyaluminum chloride, a combination of polyoxyethylene stearylamine and tall oil fatty acid dimethylamide, a combination of polyoxyethylene stearylamine, tall oil fatty acid dimethylamide, and polyaluminum chloride, a combination of polyoxyethylene stearylamine and polydiallyldimethylammonium chloride, a combination of polyaluminum chloride and ethylene glycol monobutyl ether, a combination of polyaluminum chloride and tall oil fatty acid dimethylamide, and a combination of polyoxyethylene stearylamine, tall oil fatty acid dimethylamide, and polydiallyldimethylammonium chloride. Preferred combinations of oxidizing agents and pitch dispersants include a combination of monochloramine and polyaluminum chloride, a combination of monochloramine, tall oil fatty acid dimethylamide, and polyaluminum chloride, a combination of monochloramine and polyoxyethylenestearylamine, a combination of monochloramine, tall oil fatty acid dimethylamide, and polyoxyethylenestearylamine, a combination of sodium hypochlorite and polyaluminum chloride, a combination of sodium hypochlorite, tall oil fatty acid dimethylamide, and polyaluminum chloride, a combination of sodium hypochlorite and polyoxyethylenestearylamine, a combination of sodium hypochlorite, tall oil fatty acid dimethylamide, and polyoxyethylenestearylamine, a combination of hydrogen peroxide and polyoxyethylenestearylamine, a combination of hydrogen peroxide, sodium hypochlorite, and polyoxyethylenestearylamine, a combination of monochloramine and diethylene glycol monobutyl ether, a combination of monochloramine, polyoxyethylenestearylamine, and polyaluminum chloride, and a combination of chlorine dioxide, tall oil fatty acid dimethylamide, and polyaluminum chloride.

[0049] When the pitch dispersant is a surfactant and / or an organic solvent, the total amount of the pitch dispersant added to the pulp slurry in at least one of the pulping process and the preparation process is preferably 1.5 kg / t, more preferably 1.0 kg / t, and even more preferably 0.5 kg / t from an economical standpoint. The lower limit is preferably 0.1 kg / t, more preferably 0.25 kg / t. When the pitch dispersant is a cationic polymer, the total amount added is preferably 3.0 kg / t, more preferably 1.5 kg / t, and even more preferably 1.0 kg / t from an economical standpoint. The lower limit is preferably 0.1 kg / t, more preferably 0.25 kg / t. Adding the pitch dispersant to the pulp slurry in the above amounts maintains the dispersibility of the pitch component in the pulp slurry and prevents pitch from flocculating and becoming thicker.

[0050] In the method for suppressing pitch defects of the present invention, the occurrence of pitch defects in the papermaking process is suppressed by controlling the average particle size of the pitch in the pulp slurry in the papermaking process to be less than 150 μm. As mentioned above, pitch not only adheres to manufacturing equipment such as fan pumps, piping, chests, wires, felts, and rolls during the papermaking process, but also peels off and re-adheres to the paper and pulp. This causes blemishes and defects on the paper, reducing the quality of the paper product and causing breaks that reduce productivity and workability. The average particle size of pitch, 150 μm, is the size that appears on the paper surface. Particles larger than this have a significantly higher probability of being detected as defects, so this value is used as a benchmark. Therefore, one method of pitch analysis during the papermaking process is to pass pulp slurry through a 150 μm mesh wire screen. Therefore, by controlling the size (particle size) of the pitch in the pulp slurry and maintaining the pitch in a dispersed state with an average particle size of less than 150 μm in the pulp slurry before introduction into the papermaking process, and / or by maintaining the pitch in a dispersed state with an average particle size of less than 150 μm in the pulp slurry after introduction into the papermaking process, pitch adhesion during the papermaking process is suppressed. Furthermore, since the pitch is stably dispersed and comes into contact with the pulp fibers, pitch in a specific fine state is uniformly incorporated into the paper and discharged outside the papermaking process. This prevents pitch contamination and suppresses various pitch problems that occur during the papermaking process, such as the occurrence of defective products and paper breaks due to the adhesion of large pitch to paper products. Furthermore, by incorporating the pitch component into the paper and discharging it outside the papermaking process, the amount of pitch component in the white water recycled throughout the papermaking process is reduced. In other words, the total amount of pitch in the papermaking system can be reduced, effectively suppressing pitch problems. Therefore, the pitch disorder suppression method of the present invention is preferably used for a pulp slurry in the pulping process and / or the preparation process in which the average particle size of the pitch contained in the pulp slurry introduced into the papermaking process is 150 μm or more. It is also preferably used for a pulp slurry in the papermaking process in which the average particle size of the pitch contained in the pulp slurry after introduction into the papermaking process is 150 μm or more. This is because, as described above, pitch components with large particle sizes cause pitch disorders in the papermaking process. Furthermore, the pitch disorder suppression method of the present invention preferably includes a pitch size measurement step of measuring the average particle size of the pitch in the pulp slurry introduced into the papermaking process. When the average particle size of the pitch in the pulp slurry introduced into the papermaking process is 150 μm or more, the oxidizing agent addition step and / or the pitch dispersant addition step are preferably carried out at least at one point in the pulping process and / or the preparation process. The pitch size measurement step may be carried out at least at one point in the pulping process and the preparation process, but is preferably carried out in the preparation process. Furthermore, the pitch disorder suppression method of the present invention preferably includes a pitch size measurement step of measuring the average particle size of the pitch in the pulp slurry introduced into the papermaking process, and when the average particle size of the pitch in the pulp slurry introduced into the papermaking process is 150 μm or more, the oxidizing agent addition step and / or the pitch dispersant addition step are preferably carried out at least at one point in the papermaking process. Note that the pitch size measurement step may be carried out at least at one point in the papermaking process, but is preferably carried out upstream of the inlet.

[0051] By the oxidizing agent addition step and / or the pitch dispersant addition step, the pitch component has an average particle size of less than 150 μm in the pulp slurry before being introduced into the papermaking process, but the average particle size of the pitch is preferably less than 120 μm, more preferably less than 77 μm, and even more preferably less than 23 μm. Furthermore, when the oxidizing agent addition step and / or the pitch dispersant addition step are carried out in a papermaking process, the average particle size of the pitch in the pulp slurry introduced into the papermaking process is less than 150 μm, preferably less than 120 μm, more preferably less than 77 μm, and even more preferably less than 23 μm.

[0052] The average particle size of the pitch in the pulp slurry can be measured based on the common technical knowledge commonly used by those skilled in the art in the technical field to which the present invention pertains. For example, the average particle size of the pitch can be calculated using image analysis as follows.

[0053] The method for measuring the average particle size of the pitch using image analysis is described below.

[0054] (Image acquisition of pitch particles in aqueous solution) White water is collected from the pulp slurry in a beaker or the like, taking care not to include pulp fibers. For example, a dropper may be used to visually check the white water to ensure that no pulp fibers are included, or the water may be collected using centrifugation. The resulting white water is then diluted to an appropriate concentration with pure water, and images of the pitch particles are recorded using a microscope or other device capable of acquiring images (e.g., an Olympus fluorescent microscope). In this case, if the pitch particles are difficult to see, a hydrophobic dye solution may be added to stain the pitch components, and then a color image of the pitch particles is recorded using a microscope or the like.

[0055] (Method for calculating the average particle size of pitch using image analysis) Using analytical software (Image J / provided by the National Institutes of Health), the pitch is isolated so that the particles are clearly visible to the naked eye, and the average particle size and number of the pitch are calculated by image analysis.

[0056] The oxidizing agent addition step is carried out at least at one location in the pulping process and the preparation process, and the pitch dispersant addition step is carried out at least at one location in the pulping process and the preparation process, but is preferably carried out on the pulp slurry upstream of at least one device that applies mechanical shear to the pulp slurry. Furthermore, it is preferably carried out on the pulp slurry downstream of the pulper process (defibration process) and / or the deinking process. Adding an oxidizing agent promotes the micronization of the pitch component contained in the pulp slurry. Adding a pitch dispersant also inhibits the aggregation of the pitch component and improves its dispersibility. Therefore, the pitch component in the pulp slurry is stably dispersed in a micronized state.

[0057] The pulper process is the most upstream process in the pulping process, and adding an oxidizing agent in this process can promote the micronization of pitch, further reducing the average particle size of the pitch. Furthermore, adding a pitch dispersant in the pulping process can stably disperse the micronized pitch, preventing pitch aggregation and suppressing pitch enlargement. Furthermore, although some pitch components are discharged outside the pulping process during the deinking process, a certain amount of pitch components remains in the pulp slurry after the deinking process. Therefore, by carrying out an oxidizing agent addition step and / or a pitch dispersant addition step on the pulp slurry downstream of the deinking process, it is possible to again miniaturize the pitch components and / or stably disperse the pitch components, thereby suppressing aggregation and enlargement. By carrying out an oxidizing agent addition step and / or a pitch dispersant addition step in such processes, pitch problems in the papermaking process can be more effectively prevented. Furthermore, the oxidizing agent addition step and / or pitch dispersant addition step are preferably performed at least once in the pulping process and at least once in the preparation process. By performing the oxidizing agent addition step and / or pitch dispersant addition step in the pulping process, the pitch component contained in the pulp slurry is micronized upstream of the papermaking process, and by performing the steps in the preparation process as well, it is possible to suppress enlargement of the micronized pitch component and promote further micronization.

[0058] Furthermore, when the oxidizing agent addition step and / or the pitch dispersant addition step are performed at least at one location in the papermaking process, they are preferably performed on the pulp slurry upstream of at least one device among devices that apply mechanical shear to the pulp slurry in the papermaking process. Specifically, they are preferably performed on the pulp slurry upstream of a fan pump. Adding an oxidizing agent promotes the micronization of the pitch component contained in the pulp slurry. Adding a pitch dispersant also inhibits aggregation of the pitch component and improves dispersibility. Therefore, the pitch component in the pulp slurry is stably dispersed in a micronized state.

[0059] One example of adding an oxidizing agent and pitch dispersant to the papermaking process is to add the oxidizing agent to the pulp slurry upstream of the fan pump, and then add the pitch dispersant to the white water circulated from the under-wire white water pit and used as inlet concentration adjustment water. The pitch component, which passes through the preparation process from the pulping process and is brought to the papermaking process, is broken down into fine particles by the addition of an oxidizing agent and agitation with the fan pump. The fine pitch components then come into contact with the pitch dispersant at the inlet. When paper is made in the wire part, the fine pitch components that come into contact with the pitch dispersant are carried along with the white water, pass through the under-wire white water pit, and circulate through the system from the collection tank. However, the pitch dispersant keeps the pitch size small, preventing pitch problems within the system.

[0060] The pitch dispersant addition step is preferably performed on a pulp slurry having a residual chlorine concentration of 0.5 to 30 mg / L, and more preferably on a pulp slurry having a residual chlorine concentration of 1 to 10 mg / L. By adding a pitch dispersant to a pulp slurry having a specific residual chlorine concentration, aggregation of the finely divided pitch can be suppressed and the finely divided pitch can be uniformly dispersed in the pulp slurry. This can suppress pitch problems during the papermaking process.

[0061] Furthermore, when the pitch disorder suppression method of the present invention comprises the oxidizer addition step and the pitch dispersant addition step, and the pitch dispersant is added to a pulp slurry having a residual chlorine concentration of 0.5 to 30 mg / L, the oxidant is preferably at least one selected from the group consisting of hypochlorite, chlorite, chlorine dioxide, and bound halogen. Bonded halogen is more preferred. Furthermore, the pitch dispersant addition step is preferably downstream of the oxidizer addition step.

[0062] Furthermore, when the pitch disorder suppression method of the present invention comprises the oxidant addition step and the pitch dispersant addition step, and uses at least one oxidant selected from the group consisting of hydrogen peroxide, hypochlorite, chlorite, and chlorine dioxide, the oxidant addition step and the pitch dispersant addition step are preferably carried out at the same location in at least one of the pulping process and the preparation process. This is because hydrogen peroxide, hypochlorite, chlorite, and chlorine dioxide are consumed when added to the pulp slurry, promoting pitch micronization, and by simultaneously adding a pitch dispersant, the micronized pitch can be effectively dispersed, thereby maintaining the pitch in a micronized state.

[0063] Furthermore, the oxidizing agent addition step and / or the pitch dispersant addition step may be carried out by continuous addition or by intermittent addition, but is preferably carried out by continuous addition.

[0064] In addition, in the present invention, continuous addition means continuous supply, and refers to the continuous supply of the pitch dispersant and / or oxidant to the pulp slurry, and even if the supply is repeatedly stopped, it is considered continuous supply as long as the stop time is less than 30 minutes.

[0065] In the pitch damage suppression method of the present invention, the oxidizing agent addition step and / or the pitch dispersant addition step are preferably carried out on a pulp slurry having a pulp concentration of 0.5 to 50%, and more preferably on a pulp slurry having a pulp concentration of 2.0 to 20%.

[0066] FIG. 1 is a block diagram illustrating a waste paper pulping process illustrating one embodiment of the present invention. Waste paper raw material is made into pulp slurry in pulper 1, dewatered in screw press 2, and stored in aging tower 3. Next, the pulp slurry sent from aging tower 3 passes through double separator 4, is deinked in fall washer 5 and rotary screen 6, and is stored in stock chest 7a. The pulp slurry is then bleached in hydrogen peroxide bleaching tower 8, washed and dewatered in washer 9 and thickener 10, and stored in finishing chest 7b. White water discharged from each process is recovered by white water recovery line 12 and collected in white water pit 11. The white water collected in the white water pit 11 is supplied to the waste paper pulp manufacturing process and reused via a white water supply line 13, which supplies white water to the pulper 1, the flow path connecting the pulper 1 and the maturing tower 3, the flow path connecting the bleaching tower 8 and the washer 9, etc.

[0067] As such, the pulping process generally involves multiple washing and dewatering steps, and the pulp slurry is agitated in various equipment such as pulpers, refiners, screw presses, double separators, selection screens, rotary screens, washers, thickeners, and fan pumps. In the pitch disorder suppression method of the present invention, it is preferable to carry out the oxidizing agent addition step and / or pitch dispersant addition step on the pulp slurry upstream of the stirring step, which is upstream of the drainage line. This is because the pitch components in the pulp slurry are micronized by the oxidizing agent, and aggregation is suppressed by the pitch dispersant, improving dispersibility, so that the pitch components are discharged together with the white water in the subsequent drainage line.

[0068] Furthermore, in the pitch damage suppression method of the present invention, it is preferable to further perform the above-mentioned oxidizing agent addition step and / or pitch dispersant addition step on the pulp slurry downstream of the discharge line. This is because by further miniaturizing the pitch components remaining in the pulp slurry and / or suppressing aggregation, the pitch components become stably dispersed in a miniaturized state, and pitch damage in the subsequent papermaking process can be more effectively prevented.

[0069] It is further preferred that the oxidant addition step and / or pitch dispersant addition step be performed in at least one location for each white water loop. Here, the term "white water loop" refers to a white water recirculation system formed by collecting white water discharged from the raw material lines in a white water pit and supplying the collected white water to the raw material lines, with one white water loop being formed for each white water pit. When multiple white water supply lines are connected to one white water pit, the white water recirculation system formed by the most upstream white water supply line that supplies white water from the white water pit to the most upstream side of the raw material lines is referred to as the "white water loop," and the white water supply lines branching off from the most upstream white water supply line are also included as part of the white water loop.

[0070] In another aspect of the pitch damage suppression method of the present invention, instead of including the oxidizing agent addition step and / or the dispersing agent addition step so that the average particle size of the pitch contained in the pulp slurry is less than 150 μm, the oxidizing agent addition step and / or the pitch dispersing agent addition step may be included so that the content of pitch having a particle size of less than 150 μm is 50% or more of the total amount of pitch contained in the pulp slurry. As described above, when the particle size of the pitch is 150 μm or more, pitch damage is likely to occur in the papermaking process and throughout the entire papermaking process, so the effects of the present invention can be obtained even when the pitch components having a particle size of less than 150 μm are 50% or more of the total amount of pitch.

[0071] The amount of pitch components having a particle size of less than 150 μm can be measured based on the common technical knowledge commonly used by those skilled in the art to which the present invention pertains. For example, the amount and proportion of pitch components having a particle size of less than 150 μm can be calculated by taking a sample of the pulp slurry before it is introduced into the papermaking process and / or the pulp slurry after it has been introduced into the papermaking process, and measuring the pitch in the white water collected in a manner that does not include pulp fibers using image analysis.

[0072] In this case, the pitch components having a particle size of less than 150 μm preferably account for 60% or more, more preferably 70% or more, of the total amount of pitch components in the pulp slurry, and the particle size of 50% or more of the total amount of pitch is preferably less than 120 μm, more preferably less than 77 μm, and even more preferably less than 23 μm. [Effects of the Invention]

[0073] The pitch damage suppression method of the present invention can prevent pitch damage in the papermaking process. [Brief explanation of the drawings]

[0074] [Figure 1] FIG. 1 is a block diagram illustrating a waste paper pulping process illustrating one embodiment of the present invention. [Figure 2] FIG. 2 is a graph showing the amount of hydrophobic substance (pitch) contained in the pulp slurry in the seed box during the papermaking process in Examples 31 and 32 and Reference Example 7. [Figure 3] FIG. 3 is a graph showing the amount of hydrophobic substance (pitch) in white water in the papermaking process in Examples 31 and 32 and Reference Example 7. [Figure 4] FIG. 4 is a flow diagram illustrating the pulping step and the preparation step of the papermaking process in Test Example 8.

[0075] The present invention will be described based on the following examples, comparative examples, and reference examples, but the present invention is not limited thereto. In the following examples, miniaturization of the pitch size may be expressed as "fine pitch size" or "fine pitch." [Example]

[0076] [Test Example 1] (Examples 1 to 7 and Comparative Example 1) One liter of waste paper pulp slurry, mainly composed of ethylene vinyl acetate copolymer as the pitch component, was weighed out and used as the sample. Each agent was added to the obtained sample at the concentration shown in Table 1 below, and the mixture was stirred at room temperature for 3 minutes (2000 rpm) using a tabletop pulper (manufactured by Kumagai Riki Kogyo Co., Ltd.) to obtain a sample containing the agent. Next, the obtained sample containing the agent was kept warm in a hot bath at 35°C and gently stirred for 72 hours using a three-one motor, simulating a pulp slurry flowing through a pipe. Next, after 72 hours of stirring, the average particle size of the pitch in the sample was measured using an automatic cell counter (Countess II FL) manufactured by Thermo Fisher Scientific. The measurement conditions for the cell counter were a particle count of 10^6 or more and a fluorescence intensity of 100%. The measurement conditions for the cell counter were the same for all of the following test examples. The measurement results are shown in Table 1 below. Note that when the unit of chemical addition amount in the table below is (kg / T), it indicates the amount added relative to the pulp, and when the unit of addition amount is (ppm), it indicates the amount added relative to the pulp slurry. The classification of the chemicals added in the test is indicated as A for pitch dispersants and B for oxidizing agents.

[0077] The liquid concentrations of each drug used in the following Examples 1 to 12 and Reference Examples 1 to 6 are as follows: In each test, the drug was added so that the concentration of the active ingredient indicated in the table was the same as the active ingredient concentration. Monochloramine was produced by a known method (for example, the method described in JP 2017-53054 A), and then diluted appropriately with pure water to adjust the drug concentration to the one shown in Table 1 below, and then added. Polyoxyethylene stearylamine-ethylene oxide 20 mole adduct (30% aqueous solution) Tall oil fatty acid dimethylamide (95% aqueous solution) Polyaluminum chloride (32% aqueous solution) Hydrogen peroxide (35% aqueous solution)

[0078] [Table 1]

[0079] From Examples 1 to 4, it was confirmed that the pitch size could be reduced when a surfactant, cationic polymer, or organic solvent, which is a pitch dispersant, was used alone for the sample, and when an oxidizing agent was used alone. Furthermore, from Examples 5 to 7, it was confirmed that a more excellent pitch refinement effect was achieved by using a combination of an oxidizing agent and a pitch dispersant, and a combination of a cationic polymer as a pitch dispersant and a surfactant.

[0080] [Test Example 2] (Examples 8 to 10, Comparative Example 2, and Reference Examples 1 to 4) As the pitch content, waste paper pulp slurry mainly composed of acrylic ester polymer was used, with a basis weight of 100 g / m 2 This was weighed out and used as a sample. Each drug was added to the obtained sample at the concentration shown in Table 2 below, kept warm in a warm bath at 40°C, and stirred for 1 hour using a stirrer to obtain samples containing the drugs according to Examples 8 to 10 and Reference Examples 1 to 4, and a drug-free sample according to Comparative Example 2. Next, each sample was stored in a cool, dark room at 4°C for one week, after which the pitch size was measured using an automatic cell counter (Countess II FL) manufactured by Thermo Fisher Scientific. The measurement results of the pitch refinement rate after one week, based on the pitch size without any additives, are shown in Table 2 below.

[0081] [Table 2]

[0082] When the pitch size was checked one week after treatment, it was confirmed that the pitch size had increased due to pitch aggregation when only the surfactant or oxidizing agent was used. This is thought to be because aggregation occurred due to the influence of inorganic components present in the waste paper pulp slurry after leaving it still for one week, resulting in a larger pitch size than when no chemicals were added. In an actual machine, the pulp slurry is not left still for one week, so the pitch does not increase to the extent that pitch problems occur as in this test, and the test results are obtained under more severe conditions. On the other hand, Examples 8 to 10 confirmed that an excellent pitch refinement effect can be continuously obtained by using a pitch dispersant (surfactant) and an oxidizing agent in combination.

[0083] [Test Example 3] (Examples 11 and 12, Reference Examples 5 and 6, and Comparative Example 3) The same procedure as in Test Example 2 was performed, except that the concentrations of each chemical listed in Table 3 below were used, to obtain chemical-containing samples according to Examples 11 and 12 and Reference Examples 5 and 6, and a chemical-free sample according to Comparative Example 3. Next, papermaking was performed using each of the obtained samples to produce sheets. The obtained sheets were subjected to organic solvent extraction, and the amount of pitch contained in the sheets was measured. The pitch removal rate on the sheets was determined by the percentage of pitch reduction due to the addition of chemicals, based on the pitch amount in sheets produced from the chemical-free sample according to Comparative Example 3. Furthermore, the pitch reduction rate was measured by storing each of the above samples in a cool, dark room at 4°C for one week, as in Test Example 2, and then measuring the pitch size using an automatic cell counter. The measurement results are shown in Table 3 below.

[0084] [Table 3]

[0085] When the pitch size was checked one week after treatment, it was confirmed that the use of surfactant alone caused the pitch to become larger due to pitch aggregation, similar to the results in Test Example 2. On the other hand, Examples 11 and 12 confirmed that the combined use of a pitch dispersant (surfactant) and an oxidizing agent continuously achieved an excellent pitch refinement effect. It was also confirmed that, with respect to the amount of pitch contained in the obtained sheet, excellent cleaning effects could be obtained by using a pitch dispersant and an oxidizing agent in combination.

[0086] [Test Example 4] (Examples 13 to 22 and Comparative Example 4) One liter of waste paper pulp slurry containing ethylene vinyl acetate copolymer as the main component of pitch was weighed out and used as a sample. The same test procedures as in Test Example 1 were carried out, except that instead of adding the chemicals in the concentrations shown in Table 1 above, the chemicals in the concentrations shown in Table 4 below were added to the obtained sample, and the average particle size of the pitch in the sample was measured using an automatic cell counter. The measurement results are shown in Table 4 below.

[0087] The liquid concentrations of each drug used in the following examples are as follows. In each test, the drug was added at the concentration shown in the table so that the active ingredient concentration was the same. Chlorine dioxide was generated by a known method (for example, the method described in Japanese Patent No. 5879596), and then diluted appropriately with pure water to adjust the chemical concentration to that shown in Table 4 below, and added. Polyoxyethylene stearylamine / ethylene oxide 10 mole adduct (100% purity) Polyoxyethylene stearyl ether / ethylene oxide 20 mole adduct (100% purity) Sodium hypochlorite (12% aqueous solution) Chlorine dioxide Ethylene glycol monobutyl ether (purity 99% or more) Ethylene glycol (purity 99% or more)

[0088] [Table 4]

[0089] From Examples 13 to 18, it was confirmed that the pitch size could be reduced even when a surfactant, cationic polymer, or organic solvent, which is a pitch dispersant, was used alone for the sample. Furthermore, Examples 19 to 22 confirmed that a more excellent pitch refinement effect was achieved by using a combination of an organic solvent as a pitch dispersant and a cationic polymer, and a combination of an oxidizing agent, a cationic polymer and a surfactant.

[0090] [Test Example 5] (Examples 23 to 27 and Comparative Example 5) Unbleached kraft pulp, whose pitch content was primarily natural rosin, was diluted with tap water to 0.3% to prepare a pulp slurry. The pH of the pulp slurry was adjusted to 4 using hydrochloric acid, and this was used as a sample. Each chemical agent was added to 1 L of the resulting sample at the concentrations shown in Table 5 below, and the mixture was stirred at 150 rpm using a Three-One motor for 72 hours while being kept warm in a 40°C hot bath. Next, after stirring for 72 hours, the average particle size of the pitch in each sample was measured using an automatic cell counter (Countess II FL) manufactured by Thermo Fisher Scientific, in the same manner as in Test Example 1. The measurement results are shown in Table 5 below.

[0091] [Table 5]

[0092] Examples 23 to 25 confirmed that natural pitch can be refined even when a pitch dispersant or an oxidizing agent is used alone. Furthermore, Examples 26 and 27 confirmed that a combination of a pitch dispersant and an oxidizing agent also had a more excellent effect on pitch refinement.

[0093] [Test Example 6] (Example 28 and Comparative Example 6) A paperboard raw material containing ethylene-vinyl acetate copolymer as the main pitch component was diluted with tap water to 0.3% to prepare a pulp slurry, which was used as the sample. Monochloramine was added to 300 mL of the resulting sample at 15 ppm relative to the slurry to prepare a sample related to Example 28. A sample without monochloramine was used as the sample related to Comparative Example 6. Each sample was stirred at 600 rpm for 3 minutes using a Three-One motor, then placed in a 100 mL plastic bottle, sealed, and incubated at 150 rpm at 30°C in a rotary incubator for 1 week. The average particle size of the pitch was then measured using an automatic cell counter. The measurement results are shown in Table 6 below.

[0094] [Table 6]

[0095] From Example 28, it was confirmed that even if the pitch size is large, the pitch can be made fine by adding an oxidizing agent.

[0096] [Test Example 7] (Examples 29 and 30 and Comparative Example 7) Used corrugated cardboard containing ethylene-vinyl acetate copolymer as the main component of pitch was diluted with tap water to 0.3% to prepare a pulp slurry. Two samples were prepared by adding monochloramine to 300 mL of the resulting sample at 15 ppm relative to the slurry, and these samples were designated Examples 29 and 30. A sample without monochloramine was designated Comparative Example 7. Each sample was gently stirred for 15 minutes, and then a dispersant was added to the sample of Example 30 at 0.5 kg / t relative to the pulp. Each sample was gently stirred for an additional 30 minutes, after which the average particle size of the pitch was measured using an automatic cell counter. The measurement results are shown in Table 7 below.

[0097] [Table 7]

[0098] From Example 29, it was confirmed that the pitch size can be reduced by using an oxidizing agent alone, but from the results of Example 30, it was confirmed that when an oxidizing agent and a surfactant are used in combination, the pitch size can be further reduced, even in a test assuming that the two agents are added at locations farther apart.

[0099] [Test Example 8] (Examples 31 and 32 and Reference Example 7) In the papermaking process for toilet paper production at a certain paper mill shown in Figure 4, pitch size was measured during the papermaking process when a pitch dispersant (surfactant-based or cationic polymer-based) was added to either the pulping process or the preparation process. This test was conducted with the aim of confirming in an actual papermaking process how the amount of pitch of a specific size during the papermaking process changes depending on the location of the agent addition. The test conducted up to the 5th day after the start of the test was designated Reference Example 7, the test conducted 13 to 24 days after the start of the test was designated Example 31, and the test conducted 36 to 62 days after the start of the test was designated Example 32.

[0100] (Reference example 7) From the start of the test until the fifth day, a cationic polymer-based pitch dispersant was added to the integrated chest 51 in the papermaking process at a rate of 1.0 kg / t of pulp. Example 31 On the 13th to 24th day after the start of the test, a surfactant-based pitch dispersant was added to the tank 43 installed at the outlet of the maturation tower 42 in the papermaking process at a rate of 0.5 kg / t of pulp, and a cationic polymer-based pitch dispersant was added to the general chest 51 at a rate of 0.5 kg / t of pulp. Example 32 From the 36th to 62nd day after the start of the test, a surfactant-based pitch dispersant was added to the tank 43 installed at the outlet of the maturation tower 42 in the papermaking process at a rate of 0.5 kg / t of pulp, and a cationic polymer-based pitch dispersant was added to the general chest 51 at a rate of 0.3 kg / t.

[0101] (Measurement of the amount of hydrophobic substances (pitch) of a specific size during the papermaking process) Circulating white water and pulp slurry from the seed box were collected from the papermaking process of toilet paper manufacturing at a certain paper mill. This was fractionated using a 150 μm or 23 μm mesh, and the filtrate was collected. 6 μL of 0.01% dye was added to 3 mL of the filtrate and stirred for 30 seconds to stain the hydrophobic substance (pitch). The fluorescence intensity was measured using a hydrophobicity tester (Turner Designs, Handheld Fluorometer) to determine the amount of hydrophobic substance (pitch). The seed box is a chest located downstream of the integrated chest 51, where water for adjusting pulp concentration is added before the pulp slurry is sent to the inlet. For example, it is located before the fan pump (not shown in FIG. 4). The changes over the days in the amount of hydrophobic substances less than 150 μm and less than 23 μm in the filtrate of the pulp slurry in the white water and seed box are shown in FIGS. 2 and 3.

[0102] 2 and 3 , we confirmed that the amount of hydrophobic substances (pitch) with a pitch size of less than 150 μm in the pulp slurry and white water during the papermaking process increased when pitch dispersant was added to both the comprehensive chest 51 and the tank 43 at the outlet of the aging tower 42, compared with Reference Example 7, in which pitch dispersant was added only to the comprehensive chest 51. Furthermore, we confirmed that the amount of hydrophobic substances (pitch) with a pitch size of less than 23 μm increased. These results confirm that adding pitch dispersant to both the pulping and preparation processes results in more finely divided hydrophobic substances (pitch) during the papermaking process than adding pitch dispersant only to the comprehensive chest in the preparation process. This is thought to be because adding pitch dispersant upstream of the separator 44 during the pulping process effectively finely divided the hydrophobic substances (pitch) in the pulp slurry, where mechanical shear is applied. Furthermore, adding pitch dispersant to the comprehensive chest in the preparation process maintains the finely divided hydrophobic substances (pitch). This effect significantly reduced the number of times the paper machine had to be stopped for cleaning, as pitch adhesion in the system was reduced. In addition, the pitch was refined, which weakened its adhesiveness, reducing the transfer of pitch to felt and other materials in the system, and thus reducing the number of defects. [Explanation of symbols]

[0103] 1 Pulper 2. Screw press 3. Aged Tower 4 Double Separator 5 Fall Washer 6 Rotary Screen 7a Stock Chest 7b Completed Chest 7c Chest 8 Hydrogen Peroxide Bleaching Tower 9 Washer 10 Thickener 11 Shiramizu Pit 12 White water recovery line 13 White water supply line 41 Pulper 42 Aged Tower 43 Tank 44 Separator 45 Fall Washer 46 screens 47 Screw Press 48 Fine Screen 49 Washer 50a Tank a 50b Tank B 51 General Chest

Claims

1. A pitch damage suppression method for suppressing the occurrence of pitch damage in a papermaking process by controlling the size of pitch contained in a pulp slurry in a pulping process and / or a papermaking process, The method includes an oxidizing agent adding step of adding an oxidizing agent to the pulp slurry at least at one of the pulping step and the preparation step so that the average particle size of the pitch contained in the pulp slurry is less than 150 μm, and / or a pitch dispersant adding step of adding a pitch dispersant to the pulp slurry at least at one of the pulping step and the preparation step. A pitch disturbance suppression method characterized by the above.

2. A method for suppressing pitch damage by controlling the size of pitch contained in a pulp slurry in a papermaking process and suppressing the occurrence of pitch damage in the papermaking process, The method includes an oxidizing agent adding step of adding an oxidizing agent to the pulp slurry at least at one location in the papermaking process so that the average particle size of the pitch contained in the pulp slurry is less than 150 μm, and a pitch dispersant adding step of adding a pitch dispersant to the pulp slurry at least at one location in the papermaking process. A pitch disturbance suppression method characterized by the above.

3. A pitch damage suppression method for controlling the size of pitch contained in a pulp slurry in a pulping process and / or a papermaking process and suppressing the occurrence of pitch damage in the papermaking process, A pitch disturbance suppression method comprising: a first oxidant addition step of adding a first oxidant to pulp slurry at least in one of the pulping process and the preparation process, and / or a first pitch dispersant addition step of adding a first pitch dispersant to pulp slurry at least in one of the pulping process and the preparation process, so that the average particle size of the pitch contained in the pulp slurry in the papermaking process is less than 150 μm; and further comprising a second oxidant addition step of adding a second oxidant to pulp slurry at least in one of the papermaking process and the preparation process, and / or a second pitch dispersant addition step of adding a second pitch dispersant to pulp slurry at least in one of the papermaking process.

4. 3. The method for suppressing pitch problems according to claim 1, wherein the oxidizing agent is at least one selected from the group consisting of hypochlorite, chlorite, chlorine dioxide, hydrogen peroxide, and bound halogen.

5. 4. The pitch disorder suppression method according to claim 3, wherein the first oxidizing agent and the second oxidizing agent are at least one selected from the group consisting of hypochlorite, chlorite, chlorine dioxide, hydrogen peroxide, and bound halogen.

6. 5. The method for suppressing pitch disorders according to claim 1, 2 or 4, wherein in the pitch dispersant adding step, the pitch dispersant is added to a pulp slurry having a residual chlorine concentration of 0.5 mg / L or more and 30 mg / L or less.

7. 6. The pitch disorder suppression method according to claim 3 or 5, wherein the first pitch dispersant addition step and the second pitch dispersant addition step add the pitch dispersant to a pulp slurry having a residual chlorine concentration of 0.5 mg / L or more and 30 mg / L or less.

8. 7. The pitch disorder suppression method according to claim 1, 2, 4 or 6, comprising an oxidant addition step and a pitch dispersant addition step, wherein the oxidant is at least one selected from the group consisting of hypochlorite, chlorite, chlorine dioxide and bound halogen.

9. 9. The method for suppressing pitch problems according to claim 1, 2, 4, 6 or 8, wherein the pitch dispersant is at least one selected from the group consisting of surfactants, cationic polymers and organic solvents.

10. 8. The method for suppressing pitch problems according to claim 3, 5 or 7, wherein the first and second pitch dispersants are at least one selected from the group consisting of surfactants, cationic polymers and organic solvents.

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