Paper manufacturing method and medicament

Abstract

A paper manufacturing method using a pulp slurry prepared by reusing, as a paper raw material, a portion of a low-quality raw material discharged in a papermaking step, in which the low-quality raw material to be reutilized as the paper raw material is a modified raw material treated with a specific chemical agent, and the paper pulp containing the modified raw material has better drainability and turbidity than the paper pulp containing the untreated low-quality raw material which is not treated with the specific agent.

Description

TECHNICAL FIELD

[0001] The present application relates to a paper manufacturing method and an agent, and more particularly to a technology for reusing a part of low-quality raw material discharged in a papermaking process as a paper raw material. BACKGROUND

[0002] For example, the demand for paper-based packaging materials such as corrugated board has increased with the increase in e-commerce. From the viewpoint of environmental protection and efficient resource recycling, these packaging materials are recycled as much as possible and reused as paper. However, as the recycling of these packaging materials proceeds, the fibers as raw materials deteriorate, and there is a tendency for productivity (e.g., drainage) to decrease and white water concentration (turbidity) to increase during production, which often leads to problems. In addition, even if waste discharged in a conventional papermaking process is returned to the papermaking process as it is and used, similar problems occur.

[0003] For example, Patent Literature 1 discloses a method for treating papermaking sludge, characterized in that the papermaking sludge is subjected to a deodorization treatment and a modification treatment with one or more inorganic oxidizing agents selected from a specific oxidizing agent group, and then a non-ionic water-soluble polymer containing acrylamide as a main component and a vinyl polymer-based cationic water-soluble polymer and / or a vinyl polymer-based amphoteric water-soluble polymer are sequentially added to perform a coagulation treatment, and then dewatering is performed by a dewatering machine.

[0004] Patent Literature 2 discloses a method in which lime or quicklime is added to papermaking sludge to adjust the pH of the sludge to greater than 9.5 and equal to or less than 11.0, whereby the generation of hydrogen sulfide and mercaptans can be suppressed for a long period of time, and the papermaking sludge can be used without any problems at the time of firing in a cement plant.

[0005] However, these methods are completely different from the present application since they do not mention at all the reuse of papermaking sludge as paper. Therefore, a paper manufacturing method in which waste discharged in a conventional papermaking process is used without any problems in manufacturing is not known.

[0006] List of citations

[0007] Patent literature

[0008] PTL 1: Japanese Unexamined Patent Application Publication No. 2010-149033

[0009] PTL 2: Japanese Unexamined Patent Application Publication No. 2005-161165 SUMMARY

[0010] Technical problem

[0011] The present application has been made in view of the above circumstances, and it is an object of the present application to provide a paper manufacturing method which is capable of maintaining or improving the properties of a pulp slurry by modifying low-quality material to be reused as a paper raw material in a papermaking step so as to be suitable for reuse, and also to provide a medicament for modifying low-quality material so as to be suitable for reuse.

[0012] Solution to the problem

[0013] The present inventors have conducted intensive studies to solve the above problems. As a result, the present inventors have found that, in a paper manufacturing method using a pulp slurry prepared by reusing a part of low-quality raw material discharged in a papermaking step as a paper raw material, if low-quality raw material to be reused as a paper raw material is converted into modified raw material by treatment with a specific medicament, and the modified raw material is added to the pulp slurry, the pulp slurry containing the modified raw material has properties of drainage and turbidity superior to those of a pulp slurry containing untreated low-quality raw material which has not been treated with the specific medicament, and it is possible to stably manufacture paper of good quality, thereby completing the present application. Specifically, the present application provides the following.

[0014] A first aspect of the present application relates to a paper manufacturing method including use of a pulp slurry prepared by reusing a part of low-quality raw material discharged in a papermaking step as a paper raw material, in which the low-quality raw material to be reused as a paper raw material is modified raw material treated with a specific medicament, and the pulp slurry containing the modified raw material has properties of drainage and turbidity superior to those of a pulp slurry containing untreated low-quality raw material which has not been treated with the specific medicament.

[0015] A second aspect of the present application relates to the paper manufacturing method according to the first aspect, in which the pulp slurry containing the modified raw material has properties of drainage and turbidity which are the same as or higher than those of a pulp slurry without reuse of low-quality raw material.

[0016] A third aspect of the present application relates to the paper manufacturing method according to the first aspect or the second aspect, in which the specific medicament is any one of the following (1), (2), or (3):

[0017] (1) a reaction product obtained by subjecting an acrylamide-based polymer to Hofmann degradation;

[0018] (2) a copolymer of (meth)acrylic acid, (meth)acrylamide, and dimethylaminoethyl acrylate quaternary adduct, the copolymer having an intrinsic viscosity of 8.0 to 28.0 dl / g, a cationization degree of 0.6 to 2.0 meq / g, an anionization degree of 0.20 meq / g or less, and a ratio of cationic charge density / anionic charge density of 5 to 20; and

[0019] (3) a copolymer of (meth)acrylamide and a compound represented by the following chemical formula (I) having an intrinsic viscosity of 8.0 to 28.0 dl / g and a cationization degree of 0.6 to 3.0 meq / g,

[0020] Chemical formula (I): R 1 -COO-C2H4-N(CH3)2-R 2 ,

[0021] wherein R 1 is CH2=CH- or CH2=C(CH3)-, R 2 is an alkyl group having 1 to 3 carbon atoms or a benzyl group, and they can be the same kind or different kinds.

[0022] The fourth aspect of the present application relates to the paper manufacturing method according to the third aspect, wherein the benzyl group of the medicament (3) has a cationization degree of 0.1 to 1.2 meq / g, and R 2 is a benzyl group.

[0023] The fifth aspect of the present application relates to the paper manufacturing method according to any one of the first to fourth aspects, wherein the paper stock is waste paper, paperboard, or kraft paper.

[0024] The sixth aspect of the present application relates to the paper manufacturing method according to any one of the first to fifth aspects, wherein a modified stock obtained by treating a low-quality stock with a specific medicament is mixed with the pulp slurry.

[0025] The seventh aspect of the present application relates to the paper manufacturing method according to the sixth aspect, wherein the specific medicament is further added to the pulp slurry even after the modified stock is mixed with the pulp slurry.

[0026] The eighth aspect of the present application relates to a medicament for treating a low-quality stock to be reused as a paper stock of a pulp slurry, wherein the medicament converts the low-quality stock to be reused into a modified stock so that the properties of the drainage and the turbidity of the pulp slurry are improved.

[0027] The ninth aspect of the present application relates to the medicament according to the eighth aspect, wherein the medicament is any one of the following (1), (2), or (3):

[0028] (1) a reaction product obtained by subjecting an acrylamide-based polymer to Hofmann degradation;

[0029] (2) a copolymer of (meth)acrylic acid, (meth)acrylamide and dimethylaminoethyl acrylate quaternary ammonium adduct, the copolymer having an intrinsic viscosity of 8.0 to 28.0 dl / g, a cationization degree of 0.6 to 2.0 meq / g, an anionization degree of 0.20 meq / g or less, and a ratio of cationic charge density / anionic charge density of 5 to 20; and

[0030] (3) a copolymer of (meth)acrylamide and a compound represented by the following Chemical Formula (I), the copolymer having an intrinsic viscosity of 8.0 to 28.0 dl / g and a cationization degree of 0.6 to 3.0 meq / g:

[0031] Chemical Formula (I): R 1 -COO-C2H4-N(CH3)2-R 2 ,

[0032] wherein R 1 is CH2=CH- or CH2=C(CH3)-, R 2 is an alkyl group having 1 to 3 carbon atoms or a benzyl group, and they can be the same kind or different kinds.

[0033] The tenth aspect of the present application relates to the agent as described in the ninth aspect, wherein the benzyl moiety of the agent (3) has a cationization degree of 0.1 to 1.2 meq / g, and R 2 is a benzyl group.

[0034] Advantages of the invention

[0035] According to the present application, it is possible to provide a paper manufacturing method which can maintain or improve the properties of a pulp slurry by treating a part of low-quality raw material discharged in a papermaking step with a specific agent to convert the part of the low-quality raw material into a modified raw material which can be reused as a paper raw material and adding the modified raw material to the pulp slurry, and an agent for converting a low-quality raw material into a modified raw material. DETAILED DESCRIPTION

[0036] Hereinafter, specific embodiments of the present application will be described in detail. It should be noted that the present application is not limited to the following embodiments, and appropriate modifications can be made within the scope of the object of the present application to implement.

[0037] The paper manufacturing method of the present application is a method of manufacturing paper, the method including using a pulp slurry prepared by reusing a part of low-quality raw material discharged in a papermaking step as a paper raw material, wherein the low-quality raw material to be reused as a paper raw material is a modified raw material treated with a specific agent, and the pulp slurry containing the modified raw material has properties of drainage and turbidity superior to those of a pulp slurry containing an untreated low-quality raw material which has not been treated with the specific agent.

[0038] In the above paper manufacturing method, the pulp slurry containing the modified raw material has the same or higher properties of drainage and turbidity as the pulp slurry without the recycled low-quality raw material.

[0039] Further, the agent of the present application is an agent for treating a low-quality raw material to be recycled as a paper raw material, and the agent treats the low-quality raw material to be recycled and converts it into a modified raw material, so that the properties of drainage and turbidity of the pulp slurry are improved.

[0040] In the above paper manufacturing method and the above agent, waste paper, paperboard, or kraft paper is suitable as a paper raw material.

[0041] <Low-quality raw material>

[0042] In the present application, the low-quality raw material to be treated means a raw material having an anionic trash (i.e., PCD (Cationic Demand)) of -200 μeq / L or less and a value of 10 seconds drainage amount in the following drainage test of 10 ml or more compared to a papermaking raw material used in a papermaking step.

[0043] Examples of the low-quality raw material include, for example, low-quality waste paper, DIP floss, coat broke, recycled raw material in a manufacturing process, drainage scum, paper sludge, sewage treatment plant sludge, excess sludge of biological treatment, pressurized float sludge before drainage treatment, and a raw material containing drainage sludge, and the like.

[0044] <Cationic demand>

[0045] The sample was filtered through a filter cloth having a pore size of 150 μm, and the filtrate was collected. The obtained filtrate was loaded into a flow potentiometer (PCD (Particle Change Detector)-03, manufactured by Mutec Corporation), and the cationic demand was measured from the amount of titrant (manufactured by Poly-DADMAC Kishida Chemical Co., Ltd.).

[0046] <Drainage test>

[0047] By using a drainage tester including a tube having a diameter of 60 mm with an 80 mesh screen wire attached to the bottom of the tube and a tube through which water is discharged, the sample (180 ml) accumulated in the tube was dropped downward through the screen wire by opening and closing the valve. The 10 seconds drainage amount at this time was measured by a graduated cylinder. The greater the drainage amount, the faster the dewatering speed during the papermaking process, which means that the productivity is improved.

[0048] <Specific agent>

[0049] As the (specific) agent of the present application, any cationic substance is satisfactory as long as it can neutralize anionic substances contained in, for example, low-quality raw materials. A cationic polymer is particularly preferable. The cationic polymer can adjust the charge of the pulp slurry to the optimum state by neutralizing the anionic substances. In addition, the agent is a polymer, whereby impurities such as pitch can be fixed to the fibers.

[0050] < Cationic polymer >

[0051] The cationic polymer is not particularly limited as long as it is a cationic polymer, and, in particular, any one of the cationic polymers described in (1), (2), or (3) below is preferable because the effect is achieved with a smaller addition amount:

[0052] (1) a reaction product obtained by subjecting an acrylamide-based polymer to Hofmann degradation,

[0053] Hereinafter, the reaction product is also referred to as agent (1);

[0054] (2) a copolymer of (meth)acrylic acid, (meth)acrylamide, and dimethylaminoethyl acrylate quaternary ammonium adduct, the copolymer having an intrinsic viscosity of 8.0 to 28.0 dl / g, a cationization degree of 0.6 to 2.0 meq / g, an anionization degree of 0.20 meq / g or less, and a ratio of cationic charge density / anionic charge density of 5 to 20,

[0055] Hereinafter, the copolymer is also referred to as agent (2); and

[0056] (3) a copolymer of (meth)acrylamide and a compound represented by the following Chemical Formula (I), the copolymer having an intrinsic viscosity of 8.0 to 28.0 dl / g and a cationization degree of 0.6 to 3.0 meq / g,

[0057] Hereinafter, the copolymer is also referred to as agent (3):

[0058] Chemical Formula (I): R 1 -COO-C2H4-N(CH3)2-R 2 ,

[0059] wherein R 1 is CH2=CH- or CH2=C(CH3)-, R 2 is an alkyl group having 1 to 3 carbon atoms or a benzyl group, and they can be the same kind or different kinds.

[0060] < Agent (1) >

[0061] The intrinsic viscosity and the molecular weight of the acrylamide-based polymer are generally correlated with each other. That is, as the intrinsic viscosity decreases, the molecular weight can decrease, and the drainage and the yield can decrease. Therefore, in order to improve the drainage and the yield, the intrinsic viscosity of the acrylamide-based polymer is preferably 10.0 dl / g or more, more preferably 12.5 dl / g or more. The intrinsic viscosity of the acrylamide-based polymer is more preferably 13.0 dl / g or more, more preferably 14.0 dl / g or more, most preferably 14.5 dl / g or more. If the intrinsic viscosity of the acrylamide-based polymer is too high, the molecular weight becomes too large, and when the agent (1) is added in the papermaking step, the agent (1) can function as a coagulant, which can cause a destruction of the balance of papermaking. Therefore, in order to suppress coagulation, the intrinsic viscosity of the acrylamide-based polymer is preferably 40.0 dl / g or less, more preferably 28.0 dl / g or less. The intrinsic viscosity of the acrylamide-based polymer is more preferably 24.0 dl / g or less, more preferably 20.0 dl / g or less, most preferably 16.0 dl / g or less.

[0062] If the degree of anionization of the acrylamide-based polymer is too high, an ionic reaction between the cationic group and the anionic group occurs in the acrylamide-based polymer molecule, and therefore the yield and the drainage can decrease. Therefore, the degree of anionization of the acrylamide-based polymer for improving the yield and the drainage is preferably 0.30 meq / g or less, more preferably 0.10 meq / g or less, more preferably 0.05 meq / g or less, more preferably 0.03 meq / g or less, most preferably 0.01 meq / g or less.

[0063] The intrinsic viscosity is calculated by measuring the flow time using a Cannon Fenske-type viscometer and calculating the intrinsic viscosity from the measured value using the Huggins equation and the Mead-Fuoss equation. The degree of anionization is represented by a colloidal equivalent value, which is measured according to the following method as described in paragraph 0029 of Japanese Unexamined Patent Application Publication No. 2009-228162.

[0064] <Method of measuring colloidal equivalent value of anion>

[0065] An anionic high-molecular compound diluted to a 50 ppm aqueous solution (diluted with pure water) was collected in a 100 ml graduated cylinder and transferred to a 200 ml beaker. While the solution was stirred with a rotor, an N / 10 sodium hydroxide solution (manufactured by Wako Pure Chemical Industries Ltd.) was added by a full-volume pipette, whereby the pH was adjusted to 10.5, then a few drops of toluidine blue indicator (manufactured by Wako Pure Chemical Industries) were added, and titration was performed with an N / 400 polyvinyl alcohol potassium sulfate solution (manufactured by Wako Pure Chemical Industries Ltd.). Before titration, 5 ml of an N / 200 methyl glycol chitosan solution (manufactured by Wako Pure Chemical Industries Ltd.) was added by a full-volume pipette. The point at which the blue color changed to a purplish red color and the purplish red color did not disappear even after a few seconds was determined as the end point. Similarly, a blank test (blank) was performed using pure water.

[0066] Anionic colloidal equivalent value (meq / g) = [measured value of anionic high-molecular compound (ml) - titration amount of blank test (ml)] / 2

[0067] In the present application, an acrylamide-based polymer refers to a polymer obtained by polymerizing acrylamide, and can contain other cationic monomers. Furthermore, the acrylamide polymer can or can not include anionic monomers; however, as described above, it is preferable that the acrylamide-based polymer obtained by polymerization has an intrinsic viscosity of 10.0 to 40.0 dl / g and an anionic degree of 0.3 meq / g or less. However, in order to improve the product yield by reducing the anionic degree and suppressing hydrolytic degradation of the acrylamide polymer during polymerization, it is preferable that the anionic monomers are not included.

[0068] Examples of the cationic monomers that can be included in the acrylamide-based polymer include acrylonitrile, diallyldimethylammonium chloride (DADMAC), and N,N-dimethyl-1,3-propanediamine (DMAPA), and the like.

[0069] The acrylamide-based polymer preferably has a straight chain structure (linear polymer) in order to further improve the drainage and yield of the pulp slurry containing the modified raw material and reduce the moisture content of the wet paper. That is, it is more preferable that a cross-linking monomer is not polymerized as a monomer other than acrylamide to be used for the polymerization reaction of the acrylamide-based polymer.

[0070] Examples of the solvent to be used for the polymerization reaction of the acrylamide-based polymer include water, alcohol, and dimethylformamide. Water is preferable in view of cost.

[0071] The polymerization initiator of the acrylamide-based polymer is not particularly limited, as long as it is soluble in the solvent. Examples include azo compounds such as 2,2'-azobis-2-amidinopropane hydrochloride, azobisisobutyronitrile, and 2,2'-azobis-2,4-dimethylvaleronitrile, and the like. In addition, peroxide compounds such as ammonium persulfate, potassium persulfate, hydrogen peroxide, ammonium persulfate, benzoyl peroxide, lauroyl peroxide, succinyl peroxide, octanoyl peroxide, and tert-butyl peroxy-2-ethylhexanoate are exemplified. Examples include redox systems in which ammonium persulfate is combined with sodium sulfite, sodium bisulfite, tetramethylethylenediamine, or trimethylamine. A chain transfer agent is preferably used in combination in the polymerization reaction. Examples of the chain transfer agent include alkyl mercaptans, mercaptoacetic acid and esters thereof, isopropyl alcohol, and monomers having a (meth)allyl group such as allyl alcohol, allylamine, and (meth)allyl sulfonic acid, and salts thereof.

[0072] The temperature and time of the polymerization reaction of the acrylamide-based polymer can be adjusted so that the resulting acrylamide-based polymer has a desired intrinsic viscosity and a desired degree of anionization. For example, in order for the resulting acrylamide-based polymer to have an intrinsic viscosity of 12.5 to 28.0 dl / g and a degree of anionization of 0.30 meq / g or less, the acrylamide polymer satisfying the above conditions can be polymerized, for example, by setting the initial temperature to a low temperature and gradually increasing the temperature. If the initial temperature is too high, the intrinsic viscosity decreases, and during the reaction, a hydrolysis product of acrylamide is produced, which increases the degree of anionization. Therefore, a low initial temperature is desirable. More specifically, the initial temperature of the polymerization reaction is preferably 10°C to 30°C, more preferably 15°C to 25°C, and most preferably 18°C to 22°C. In addition, from the viewpoint of easily controlling the heat generation during polymerization, the upper limit of the temperature that rises after the start of polymerization is preferably 80°C or less, more preferably 70°C or less, and most preferably 65°C or less.

[0073] <Reaction product generation step>

[0074] In the reaction product generation step, by subjecting the above-described acrylamide-based polymer to Hofmann degradation, an agent with which low-quality raw material to be reused as paper pulp slurry is treated can be produced, and the agent can be used as an agent that treats low-quality raw material to be reused and converts it into modified raw material, so that the properties of the drainage and the turbidity of the paper pulp slurry are improved.

[0075] When Hofmann degradation is performed, the solution obtained by polymerizing the acrylamide-based polymer can be used as is or can be used after dilution. If necessary, the solution can be prepared separately as needed.

[0076] When the concentration of the acrylamide-based polymer to be subjected to Hofmann degradation is set to be high, an uneven reaction occurs, and sufficient yield improvement effect or water drainage property improvement effect cannot be obtained. In order to sufficiently obtain these effects, the concentration of the acrylamide-based polymer is preferably 35% by mass or less, more preferably 10% by mass or less, more preferably 5% by mass or less, and most preferably 2% by mass or less. When the concentration of the acrylamide-based polymer is too low, the efficiency of Hofmann degradation decreases, and thus the concentration of the acrylamide-based polymer is preferably 0.001% by mass or more, more preferably 0.010% by mass or more, and most preferably 0.100% by mass or more.

[0077] Hofmann degradation is preferably performed by allowing a hypohalite to act on the amide group of the acrylamide-based polymer under alkaline conditions. Specifically, Hofmann degradation is preferably performed in a pH range of 8.0 or more, and is preferably performed in a pH range of 11.0 to 14.0. In order to obtain alkaline conditions, for example, an alkali metal hydroxide such as sodium hydroxide, potassium hydroxide, and lithium hydroxide is used. In order to allow the hypohalite to act, for example, a hypohalite such as a hypochlorite, a hypobromite, or a hypoiodite is used.

[0078] Examples of the hypochlorite, the hypobromite, and the hypoiodite include alkali metal salts and alkaline earth metal salts thereof. Examples of the alkali metal salt in the hypochlorite include sodium hypochlorite, potassium hypochlorite, and lithium hypochlorite.

[0079] The amount of the hypohalite to be subjected to Hofmann degradation is not particularly limited, but if the amount of the acrylamide-based polymer is too small or too large relative to the amount of the hypohalite, the amount of the acrylamide-based polymer or the hypohalite that does not participate in the reaction increases, so that the efficiency of the reaction decreases. In order to efficiently perform the reaction, the molar ratio of the hypohalite to the acrylamide-based polymer is preferably 0.1:10 to 10:10, more preferably 1:10 to 10:10, and most preferably 2:10 to 10:10.

[0080] In the Hofmann degradation of the present application, the hypohalite is preferably mixed with the liquid containing the acrylamide-based polymer under conditions of pH 8.0 or more. Thereby, the gelation of the reaction product can be prevented. In the Hofmann degradation, the base is preferably added to the liquid containing the acrylamide-based polymer together with the hypohalite. This also prevents the gelation of the reaction product. As the base, a conventionally known base (an alkali metal hydroxide, for example, the above-mentioned sodium hydroxide, potassium hydroxide, and lithium hydroxide, etc.) can be used.

[0081] The temperature in the Hofmann degradation can be appropriately selected in the range of 0°C to 110°C, but can be selected in combination with the reaction time to obtain the above-mentioned desired cationization degree. For example, when the reaction product is supplied within 24 hours, the Hofmann degradation is preferably performed in the range of 10°C to 50°C and more preferably 10°C to 30°C.

[0082] In the above reaction product producing step, a neutralizing agent can be added before the next step of supplying the reaction product, but it is preferable not to add a neutralizing agent. The addition of a neutralizing agent tends to improve the drainage and the yield, and to reduce the moisture content of the wet paper. Examples of the neutralizing agent include a pH adjuster (e.g., hydrochloric acid) used for neutralizing the conventional well-known Hofmann degradation.

[0083] The cationization degree of the acrylamide-based polymer is preferably 0.01 meq / g or more, more preferably 0.10 meq / g or more, more preferably 0.30 meq / g or more, more preferably 0.50 meq / g or more, and most preferably 1.00 meq / g or more. Furthermore, the higher the cationization degree of the acrylamide-based polymer, the higher the effect, which is preferable, because the amount of addition can be reduced. The cationization degree of the acrylamide-based polymer is usually 2.00 meq / g or less.

[0084] The cationization degree of the reaction product is similarly represented by the colloidal equivalent value, and is measured by the following method.

[0085] <Method of measuring the colloidal equivalent value of cations>

[0086] The reaction product diluted to 50 ppm in an aqueous solution (diluted with pure water) was collected in a 100 ml graduated cylinder and transferred to a 200 ml beaker. While the solution was stirred with a rotor, an N / 10 hydrochloric acid solution was added by a full-volume pipette, whereby the pH was adjusted to 4, and then a few drops of toluidine blue indicator (manufactured by Wako Pure Chemical Industries) were added, and titration was performed with an N / 400 polyvinyl alcohol potassium sulfate solution (manufactured by Wako Pure Chemical Industries Ltd.). Before the titration, 5 ml of an N / 200 methyl glycol chitosan solution (manufactured by Wako Pure Chemical Industries) was added by a full-volume pipette. The point at which the blue color changed to a purplish red color and the purplish red color did not disappear even after a few seconds was determined as the end point. Similarly, a blank test (blank) was performed using pure water. The colloidal equivalent value of cations (meq / g) = [measured value of the reaction product (ml) - titration amount of the blank test (ml)] / 2

[0087] <Medicament (2)>

[0088] The intrinsic viscosity and the molecular weight of the copolymer of (meth)acrylic acid, (meth)acrylamide and dimethylaminoethyl acrylate quaternary ammonium adduct are generally correlated with each other. That is, as the intrinsic viscosity decreases, the molecular weight can decrease, and the drainage and the yield can decrease. Therefore, in order to improve the drainage and the yield, the intrinsic viscosity of the copolymer of (meth)acrylic acid, (meth)acrylamide and dimethylaminoethyl acrylate quaternary ammonium adduct is preferably 8.0 dl / g or more, and more preferably 12.5 dl / g or more. The intrinsic viscosity of the copolymer of (meth)acrylic acid, (meth)acrylamide and dimethylaminoethyl acrylate quaternary ammonium adduct is more preferably 13.0 dl / g or more, more preferably 14.0 dl / g or more, and most preferably 14.5 dl / g or more. If the intrinsic viscosity of the copolymer of (meth)acrylic acid, (meth)acrylamide and dimethylaminoethyl acrylate quaternary ammonium adduct is too high, the molecular weight becomes too large, and when the agent (2) is added in the papermaking step, the agent (2) can function as a coagulant, which can cause a destruction of the balance of papermaking. Therefore, in order to suppress coagulation, the intrinsic viscosity of the copolymer of (meth)acrylic acid, (meth)acrylamide and dimethylaminoethyl acrylate quaternary ammonium adduct is preferably 28.0 dl / g or less, more preferably 24.0 dl / g or less, more preferably 20.0 dl / g or less, and most preferably 16.0 dl / g or less.

[0089] If the degree of anionization of the copolymer of (meth)acrylic acid, (meth)acrylamide and dimethylaminoethyl acrylate quaternary ammonium adduct is too high, an ionic reaction between the cationic group and the anionic group occurs in the copolymer of (meth)acrylic acid, (meth)acrylamide and dimethylaminoethyl acrylate quaternary ammonium adduct, and thus the yield and the drainage can decrease. Therefore, the degree of anionization of the copolymer of (meth)acrylic acid, (meth)acrylamide and dimethylaminoethyl acrylate quaternary ammonium adduct for improving the yield and the drainage is preferably 0.20 meq / g or less, more preferably 0.10 meq / g or less, more preferably 0.05 meq / g or less, more preferably 0.03 meq / g or less, and most preferably 0.01 meq / g or less.

[0090] The intrinsic viscosity and the degree of anionization of the copolymer of (meth)acrylic acid, (meth)acrylamide and dimethylaminoethyl acrylate quaternary ammonium adduct are measured in the same manner as the acrylamide-based polymer described above.

[0091] The degree of cationization of the copolymer of (meth)acrylic acid, (meth)acrylamide and dimethylaminoethyl acrylate quaternary ammonium adduct is preferably 0.6 meq / g or more and 2.0 meq / g or less, and more preferably 0.8 meq / g or more and 1.5 meq / g or less.

[0092] The cationization degree of the copolymer of (meth)acrylic acid, (meth)acrylamide and dimethylaminoethyl acrylate quaternary ammonium adduct is measured in the same manner as the acrylamide-based polymer described above.

[0093] The copolymer of (meth)acrylic acid, (meth)acrylamide and dimethylaminoethyl acrylate quaternary ammonium adduct is preferably cation-rich, and more specifically, the ratio of cationic charge density / anionic charge density is more preferably in the range of 5 to 20.

[0094] The dimethylaminoethyl acrylate quaternary ammonium adduct is obtained by reacting dimethylaminoethyl acrylate with a quaternizing agent. Examples of the quaternizing agent include alkyl halides such as methyl chloride and dialkyl sulfates such as dimethyl sulfate. When these quaternizing agents are reacted with dimethylaminoethyl acrylate, the alkyl group of the quaternizing agent is introduced into the nitrogen atom of dimethylaminoethyl acrylate to form a salt of a quaternary ammonium ion and a halide ion or a monoalkyl sulfate ion. The alkyl group introduced by the quaternizing agent is preferably an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group or an ethyl group, and particularly preferably a methyl group. The quaternization of dimethylaminoethyl acrylate can be performed by a publicly known method.

[0095] Examples of the solvent to be used for the polymerization reaction of the copolymer of (meth)acrylic acid, (meth)acrylamide and dimethylaminoethyl acrylate quaternary ammonium adduct include water, alcohol and dimethylformamide. Water is preferred in view of cost.

[0096] The polymerization initiator of the copolymer of (meth)acrylic acid, (meth)acrylamide and dimethylaminoethyl acrylate quaternary ammonium adduct is not particularly limited as long as it is soluble in the solvent. Examples include azo compounds such as 2,2'-azobis-2-amidinopropane hydrochloride, azobisisobutyronitrile and 2,2'-azobis-2,4-dimethylvaleronitrile, and the like. In addition, peroxide compounds such as ammonium persulfate, potassium persulfate, hydrogen peroxide, ammonium persulfate, benzoyl peroxide, lauroyl peroxide, succinyl peroxide, octanoyl peroxide and tert-butyl peroxy-2-ethylhexanoate are exemplified. A redox system in which ammonium persulfate is combined with sodium sulfite, sodium bisulfite, tetramethylethylenediamine or trimethylamine is also exemplified. A chain transfer agent is preferably used in combination in the polymerization reaction. Examples of the chain transfer agent include alkyl mercaptans, mercaptoacetic acid and esters thereof, isopropyl alcohol and monomers having a (meth)allyl group such as allyl alcohol, allylamine and (meth)allyl sulfonic acid and salts thereof.

[0097] The temperature and time of the polymerization reaction of the copolymer of the (meth)acrylic acid, the (meth)acrylamide, and the dimethylaminoethyl acrylate quaternary ammonium salt adduct can be adjusted so that the copolymer of the (meth)acrylic acid, the (meth)acrylamide, and the dimethylaminoethyl acrylate quaternary ammonium salt adduct obtained has a desired intrinsic viscosity, cationization degree, anionization degree, ratio of cationic charge density / anionic charge density. For example, in order for the copolymer of the (meth)acrylic acid, the (meth)acrylamide, and the dimethylaminoethyl acrylate quaternary ammonium salt adduct to have an intrinsic viscosity of 8.0 to 28.0 dl / g, a cationization degree of 0.6 to 2.0 meq / g, and an anionization degree of 0.20 meq / g or less, a ratio of cationic charge density / anionic charge density of 5 to 20, the copolymer of the (meth)acrylic acid, the (meth)acrylamide, and the dimethylaminoethyl acrylate quaternary ammonium salt adduct satisfying the above conditions can be polymerized, for example, by setting the initial temperature to a low temperature and gradually increasing the temperature. If the initial temperature is too high, the intrinsic viscosity decreases, and during the reaction, a hydrolyzate of the (meth)acrylamide is produced, which increases the anionization degree. Therefore, a low initial temperature is desirable. More specifically, the initial temperature of the polymerization reaction is preferably 10°C to 30°C, more preferably 15°C to 25°C, and most preferably 18°C to 22°C. Furthermore, from the viewpoint of easily controlling the heat generation during the polymerization, the upper limit of the temperature that rises after the start of the polymerization is preferably 80°C or less, more preferably 70°C or less, and most preferably 65°C or less.

[0098] <Agent (3)>

[0099] The intrinsic viscosity and the molecular weight of the copolymer of the (meth)acrylamide and the compound represented by Chemical Formula (I) generally correlate with each other. That is, as the intrinsic viscosity decreases, the molecular weight can decrease, and the drainage and the yield can decrease. Therefore, in order to improve the drainage and the yield, the intrinsic viscosity of the copolymer of the (meth)acrylamide and the compound represented by Chemical Formula (I) is preferably 8.0 dl / g or more, and more preferably 12.5 dl / g or more. The intrinsic viscosity of the copolymer of the (meth)acrylamide and the compound represented by Chemical Formula (I) is more preferably 13.0 dl / g or more, more preferably 14.0 dl / g or more, and most preferably 14.5 dl / g or more. If the intrinsic viscosity of the copolymer of the (meth)acrylamide and the compound represented by Chemical Formula (I) is too high, the molecular weight becomes too large, and when the agent (3) is added in the papermaking step, the agent (3) can function as a coagulant, which can cause a disruption of the balance of the papermaking. Therefore, in order to suppress coagulation, the intrinsic viscosity of the copolymer of the (meth)acrylamide and the compound represented by Chemical Formula (I) is preferably 28.0 dl / g or less, more preferably 24.0 dl / g or less, more preferably 20.0 dl / g or less, and most preferably 16.0 dl / g or less.

[0100] If the anionization degree of the copolymer of (meth)acrylamide and the compound represented by Chemical Formula (I) is too high, an ionic reaction between the cationic group and the anionic group occurs in the molecule of the copolymer of (meth)acrylamide and the compound represented by Chemical Formula (I), and thus the yield and the drainage property can be reduced. Therefore, the anionization degree of the copolymer of (meth)acrylamide and the compound represented by Chemical Formula (I) for improving the yield and the drainage property is preferably 0.20 meq / g or less, more preferably 0.10 meq / g or less, more preferably 0.05 meq / g or less, more preferably 0.03 meq / g or less, and most preferably 0.01 meq / g or less.

[0101] The intrinsic viscosity and the anionization degree of the copolymer of (meth)acrylamide and the compound represented by Chemical Formula (I) are measured in the same manner as the above acrylamide-based polymer.

[0102] The cationization degree of the copolymer of (meth)acrylamide and the compound represented by Chemical Formula (I) is preferably 0.6 meq / g or more and 3.0 meq / g or less, and more preferably 0.8 meq / g or more and 1.5 meq / g or less.

[0103] The cationization degree of the copolymer of (meth)acrylamide and the compound represented by Chemical Formula (I) is measured in the same manner as the above acrylamide-based polymer.

[0104] Specific examples of the compound represented by Chemical Formula (I) include quaternary salts such as hydrochloride and sulfate of (meth)acrylate dialkylaminoalkyl esters such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate; alkyl halide adducts such as chloromethane; benzyl halide adducts such as benzyl chloride; and dialkyl sulfate adducts such as dimethyl sulfate.

[0105] When the benzyl halide adduct containing (meth)acrylate dialkylaminoalkyl ester (hereinafter sometimes referred to as a benzyl moiety) is used as the compound represented by Chemical Formula (I) (i.e., when R 2 of the copolymer of (meth)acrylamide and the compound represented by Chemical Formula (I) is preferably 0.1 meq / g or more, more preferably 0.2 meq / g or more, more preferably 0.2 meq / g or more, more preferably 0.4 meq / g or more, and most preferably 0.6 meq / g or more. The cationization degree of the benzyl moiety of the copolymer of (meth)acrylamide and the compound represented by Chemical Formula (I) is preferably 1.2 meq / g or less, more preferably 1.0 meq / g or less, and most preferably 0.9 meq / g or less.

[0106] The degree of cationization of the benzyl moiety in the copolymer of (meth)acrylamide and the compound represented by Chemical Formula (I) can be determined by C 13 DAB mol% and DAA mol% determined by NMR.

[0107] As the solvent to be used in the polymerization of the copolymer of (meth)acrylamide and the compound represented by Chemical Formula (I), water, alcohol, or dimethylformamide, or the like can be used. Water is preferred in view of cost.

[0108] The polymerization initiator of the copolymer of (meth)acrylamide and the compound represented by Chemical Formula (I) is not particularly limited as long as it is soluble in the solvent. Examples include azo compounds such as 2,2'-azobis-2-imidazolinopropane hydrochloride, azobisisobutyronitrile, and 2,2'-azobis-2,4-dimethylvaleronitrile, and the like. Further, peroxide compounds such as ammonium persulfate, potassium persulfate, hydrogen peroxide, ammonium persulfate, benzoyl peroxide, lauroyl peroxide, succinyl peroxide, octanoyl peroxide, and tert-butyl peroxy-2-ethylhexanoate are exemplified. Examples include redox systems in which ammonium persulfate is combined with sodium sulfite, sodium bisulfite, tetramethylethylenediamine, or trimethylamine. A chain transfer agent is preferably used in combination in the polymerization reaction. Examples of the chain transfer agent include alkyl mercaptans, mercaptoacetic acid and esters thereof, isopropyl alcohol, and monomers having a (meth)allyl group such as allyl alcohol, allylamine, and (meth)allyl sulfonic acid, and salts thereof.

[0109] The temperature and time of the polymerization reaction of the copolymer of (meth)acrylamide and the compound represented by Chemical Formula (I) can be adjusted so that the copolymer of (meth)acrylamide and the compound represented by Chemical Formula (I) has a desired intrinsic viscosity and a desired degree of anionization. For example, in order for the copolymer of (meth)acrylamide and the compound represented by Chemical Formula (I) in which R 2 is a benzyl group to have an intrinsic viscosity of 8.0 to 28.0 dl / g, a degree of cationization of 0.6 to 3.0 meq / g, and a degree of cationization of the benzyl moiety of 0.1 to 1.2 meq / g, for example, the copolymer of (meth)acrylamide and the compound represented by Chemical Formula (I) can be polymerized by setting the initial temperature to a low temperature and gradually increasing the temperature. If the initial temperature is too high, the intrinsic viscosity decreases, and during the reaction, a hydrolyzate of (meth)acrylamide is produced, which increases the degree of anionization. Therefore, a low initial temperature is desired. More specifically, the initial temperature of the polymerization reaction is preferably 10°C to 30°C, more preferably 15°C to 25°C, and most preferably 18°C to 22°C. Further, from the viewpoint of easily controlling the heat generation at the time of polymerization, the upper limit of the temperature that rises after the start of polymerization is preferably 80°C or lower, more preferably 70°C or lower, and most preferably 65°C or lower.

[0110] Note that the respective physical property values of the agents (2) and (3) represented by the intrinsic viscosity, the cationization degree, the anionization degree, and the ratio of the cationic charge density / anionic charge density mean the content with respect to the net content of the polymer.

[0111] The polymerization method of the agents (1) to (3) is not particularly limited, but can be, for example, aqueous solution polymerization, inverse emulsion polymerization, dispersion polymerization, or solution polymerization, etc.

[0112] The form of the agents (1) to (3) is not particularly limited, and examples thereof include an aqueous solution, a dispersion in brine, a water-in-oil emulsion, and a powder, etc.

[0113] <Selection method of agent for low-quality raw material>

[0114] Regarding the combination of the agent and the low-quality raw material to be treated in the selection of the agent of the present application, an agent that has a good reactivity with the low-quality raw material can be selected. That is, a low filtrate turbidity and a large water filtration amount are used as indices of good reactivity. At this time, in order to consider not only the filtrate turbidity and the water filtration amount, but also the cost of the agent, for example, the difference in the unit price of each agent in each supply region should be considered. Therefore, it is preferable to comprehensively evaluate and select after performing the test selected by the method disclosed in the examples, including the economy.

[0115] The addition amount of the above agent can be expected to be effective only by adding a small amount to the low-quality raw material, but is preferably 10 ppm or more, more preferably 100 ppm or more, more preferably 250 ppm or more, more preferably 500 ppm or more, and most preferably 1000 ppm or more. The upper limit of the addition amount of the above agent is not particularly limited, but since the treatment cost increases as the addition amount increases, from the viewpoint of the treatment cost, the upper limit is preferably 10,000 ppm or less, more preferably 8,000 ppm or less, more preferably 6,000 ppm or less, and more preferably 4,000 ppm or less.

[0116] As the method of adding the above agent, a known method can be used, and a method in which the above agent is added to a pulp containing a low-quality raw material to produce a modified raw material, and the modified raw material is added to a pulp slurry of a papermaking raw material to make paper can be mentioned. The order in which the above agent is added to the pulp containing a low-quality raw material is not particularly limited. The method of adding these agents is not particularly limited, and the agent can be diluted with industrial water or the like and added, or the agent can be added as it is.

[0117] After the modified raw material is mixed with the pulp slurry, the agent can be further added to the pulp slurry. The method of adding these agents is not particularly limited, and the agent can be diluted with industrial water or the like and added, or the agent can be added as it is.

[0118] The amount of the modified raw material obtained by chemical treatment of the low-quality raw material added to the paper pulp slurry is preferably 0.01 to 20.00% by weight, more preferably 0.10 to 10.00% by weight, more preferably 0.30 to 5.00% by weight, and most preferably 0.50 to 3.00% by weight.

[0119] Examples

[0120] Hereinafter, the present application will be described more specifically with reference to examples, but the present application is not limited to the following examples.

[0121] <Examples 1 to 6>

[0122] Since paper sludge (hereinafter, it is also referred to as "PS") is a low-quality raw material, if the paper sludge is used as it is as a paper raw material (papermaking raw material) for papermaking, the dewatering speed in the papermaking machine decreases, and the production efficiency decreases. Therefore, in each of Examples 1 to 6, a paper pulp slurry (modified raw material) was prepared by treating 5 mass% of PS with the agent (1) (PD-3820) at the addition amount shown in Table 1. Then, a filter test was performed on each of the prepared paper pulp slurries, and the filtrate turbidity and the amount of water filtered were measured. The preparation conditions and the results of the paper pulp slurries are shown in Table 1 below.

[0123] <Comparative Example 1, Reference Example 1>

[0124] In Comparative Example 1, a paper pulp slurry of untreated 5 mass% PS which was not treated with the agent (1) was prepared. In addition, in Reference Example 1, a paper pulp slurry of 95 mass% papermaking raw material which did not contain PS and the agent (1) was prepared. Then, a filter test was performed on the paper pulp slurries, and the filtrate turbidity and the amount of water filtered were measured. The preparation conditions and the results of the paper pulp slurries are shown in Table 1 below.

[0125] <Filter Test>

[0126] By using a filter test apparatus including a tube having a diameter of 60 mm with a 80 mesh screen wire attached to the bottom of the tube and a tube through which water is discharged, the paper pulp slurry (180 ml) accumulated in the tube was dropped down through the screen wire by opening and closing the valve. The amount of water filtered for 10 seconds at that time was measured by a graduated cylinder.

[0127] <Turbidity>

[0128] The turbidity of the filtrate obtained in the above filter test was measured using a portable turbidimeter (2100Q, manufactured by DKK-TOA CORPORATION). Note that, since the turbidity is lower, dirt in the system decreases, and the risk of defects and paper breakage can be reduced, compared to Comparative Example 1 in which the agent (1) is not added.

[0129] The following agent was used as the agent (1).

[0130] PD-3820: a reaction product obtained by Hofmann degradation of an acrylamide-based polymer at polymer: hypohalous acid = 10:4, manufactured by Kurita Water Industries Ltd.

[0131] [Table 1]

[0132]

[0133] As shown in Table 1, in Comparative Example 1 in which the untreated paper sludge was compounded / contained, the drainage amount was only 2 ml. When the paper pulp slurry prepared in Comparative Example 1 was compounded into another raw material as a raw material in an amount of, for example, 1% by weight or more, the dewatering speed of the paper machine was significantly reduced, resulting in poor paper production efficiency. In contrast, in each of Examples 1 to 6 in which the treatment using the agent (1) was performed, the drainage amount was greater and the filtrate turbidity was lower compared to Comparative Example 1. Among them, Examples 4 to 6 had the same or better properties of drainage and filtrate turbidity as Reference Example 1. As described above, the agent treatment significantly improved the drainage amount and significantly reduced the filtrate turbidity, and thus the treatment effect of the agent could be confirmed.

[0134] The properties of the low-quality raw material other than the paper sludge and the properties of the papermaking raw material as a comparative object are shown in Table 2.

[0135] [Table 2]

[0136]

[0137] As shown in Table 2, it was found that the low-quality raw material was significantly inferior to the papermaking raw material in terms of drainage properties and the like.

[0138] [Examples 7 to 15]

[0139] A predetermined amount of the modified raw material obtained in each of the above-described examples was added to a pulp slurry raw material collected in the production process of a papermaking paperboard factory as shown in Table 3, and then 200 ppm of PD-1230 (manufactured by Kurita Water Industries) was added as a yield and drainage property improver of a cationic polyacrylamide generally used for paper production, to obtain a paper pulp slurry. Then, the paper pulp slurry was subjected to a drainage test in the same manner as in Examples 1 to 6, and the filtrate turbidity and the drainage amount were measured. In Examples 7 to 15, the concentration of the pulp slurry raw material was set to 1% by weight.

[0140] [Comparative Examples 2 to 3, Reference Example 2]

[0141] The paper pulp slurry was obtained in the same manner as in Examples 7 to 15, except that the pulp raw material collected in the production process of a paperboard mill was changed to the modified raw material shown in Table 3. Then, the paper pulp slurry was subjected to a drainage test in the same manner as in the above-described Examples 7 to 15, and the filtrate turbidity and the drainage amount were measured. In Comparative Examples 2 and 3 and Reference Example 2, the concentration of the pulp raw material was set to 1% by weight.

[0142] [Table 3]

[0143]

[0144] As shown in Table 3, in the paper pulp slurry of each of Examples 7 to 15 containing the modified raw material, an improvement in the drainage property and the filtrate turbidity was observed as compared with Comparative Examples 2 and 3. With respect to the case where 5% by weight of the modified raw material was compounded, it was confirmed that Examples 9 to 11 had the same or better effect as Reference Example 2, and it was considered that the addition amount of the agent (1) was more preferably 2,000 ppm or more. In addition, with respect to the case where 10% by weight of the modified raw material was compounded, it was confirmed that Examples 13 to 15 had the same or better effect as Reference Example 2, and, similarly to the case where 5% by weight of the modified raw material was compounded, it was considered that the addition amount of the agent (1) was more preferably 2,000 ppm or more. Note that no influence on the effect of the means for solving the problem of the low-quality raw material was observed regardless of whether or not the yield and drainage improver was added.

[0145] <Examples 16 to 24 and Comparative Examples 4 to 6>

[0146] In the synthesis, the following monomers were used.

[0147] "AM": (Meth)acrylamide

[0148] "DAA": Dimethylaminoethyl acrylate quaternary ammonium adduct (dichloromethane salt)

[0149] "AA": (Meth)acrylic acid

[0150] "DAB": N-(2-acryloyloxyethyl)-N-benzyl-N,N-dimethylammonium chloride

[0151] (Example 16)

[0152] To a 300-ml four-necked flask equipped with a stirrer, a nitrogen inlet tube, a cooler, and a thermometer, AM = 11.2 g, DAA = 9.7 g, AA = 0.14 g, and 164.0 g of demineralized water were added. After nitrogen was bubbled, the temperature was raised to 50°C, 2 g of a 1% aqueous solution of 2,2'-azobis-2-amidinopropane dihydrochloride was added, and the mixture was maintained at 60°C for 6 hours under stirring at 300 rpm. A portion of the resulting polymer was taken out and vacuum freeze-dried to synthesize a solid polymer (Agent (2)). The anionic or cationic colloidal equivalent value and the intrinsic viscosity of Agent (2) were measured by the following methods. Paper pulp slurry treated by adding 2,000 ppm of the solid polymer (Agent (2)) to 5 mass% of paper sludge was prepared, and the drainage test of the paper pulp slurry was performed in the same manner as in Examples 1 to 6, and the filtrate turbidity and the drainage amount were measured.

[0153] (Examples 17 to 24 and Comparative Examples 4 to 6)

[0154] The solid polymers were synthesized in the same manner as in Example 16 and the same measurements were performed except that the monomers shown in Tables 4 and 5 below were added instead of AM = 11.2 g, DAA = 9.7 g, and AA = 0.14 g in Example 16 and each of the solid polymers shown in Tables 4 and 5 below was added to 5 mass% of paper sludge at a content of 2,000 ppm (the polymers of Examples 17 and 18 are Agent (2) and the polymers of Examples 19 to 24 are Agent (3)). The degree of cationization of the benzyl moiety of each of the solid polymers of Examples 19 to 24 was measured by the following method.

[0155] <Colloidal equivalent value of anion>

[0156] A sample diluted to a 50 ppm aqueous solution (diluted with pure water) was collected in a 100 ml graduated cylinder and transferred to a 200 ml beaker. While stirring the solution with a rotor, an N / 10 sodium hydroxide solution (manufactured by Wako Pure Chemical Industries Ltd.) was added by a full volume pipette, whereby the pH was adjusted to 10.5, then a few drops of toluidine blue indicator (manufactured by Wako Pure Chemical Industries) were added, and titration was performed with an N / 400 polyvinyl alcohol potassium sulfate solution (manufactured by Wako Pure Chemical Industries Ltd.). Before titration, 5 ml of an N / 200 methyl glycol chitosan solution (manufactured by Wako Pure Chemical Industries Ltd.) was added by a full volume pipette. The point at which the blue color changed to a purplish red color and the purplish red color did not disappear even after a few seconds was determined as the end point. Similarly, a blank test was performed using pure water (blank). Colloidal equivalent value of anion (meq / g) = [measured value of anionic high molecular compound (ml) - titration amount of blank test (ml)] / 2

[0157] <Colloidal equivalent value of cation>

[0158] A sample diluted to a 50 ppm aqueous solution (diluted with pure water) was collected in a 100 ml graduated cylinder and transferred to a 200 ml beaker. While stirring the solution with a rotor, an N / 10 hydrochloric acid solution was added by a full volume pipette, whereby the pH was adjusted to 4, then a few drops of toluidine blue indicator (manufactured by Wako Pure Chemical Industries) were added, and titration was performed with an N / 400 polyvinyl alcohol potassium sulfate solution (manufactured by Wako Pure Chemical Industries Ltd.). Before titration, 5 ml of an N / 200 methyl glycol chitosan solution (manufactured by Wako Pure Chemical Industries) was added by a full volume pipette. The point at which the blue color changed to a purplish red color and the purplish red color did not disappear even after a few seconds was determined as the end point. In the same manner, a blank test was performed using pure water (blank). Colloidal equivalent value of cation (meq / g) = [measured value of reaction product (ml) - titration amount of blank test (ml)] / 2

[0159] <Intrinsic viscosity>

[0160] The flow time of each sample was measured using a Cannon-Fenske type viscometer, and the intrinsic viscosity was calculated from the measured value using the Huggins equation and the Mead-Fuoss equation.

[0161] <Degree of cationization of benzyl moiety>

[0162] The degree of cationization of the benzyl moiety was calculated from the DAB mol% and the DAA mol% determined by 13 The degree of cationization of the benzyl moiety = DAB mol% x degree of cationization / (DAA mol% DAB mol%)

[0163]

[0164]

[0165] As shown in Tables 4 and 5, it was found that the drainage and filtrate turbidity of the pulp slurry treated with the agent (2) or the agent (3) were significantly improved, similarly to the case of the agent (1).

[0166] Next, using DIP sludge as a low-quality raw material other than paper sludge, the effect when using the agent of the present application was confirmed.

[0167] <Examples 25 to 33, Comparative Example 7, and Reference Example 3>

[0168] DIP sludge generated from a papermaking paperboard plant was used as a low-quality raw material. A pulp slurry used for producing paperboard in the same papermaking paperboard plant was used as a papermaking raw material. In each of Examples 25 to 33, the agent shown in Table 6 was added to the DIP sludge in the content shown therein to obtain a modified raw material, which was compounded with the papermaking raw material to obtain a solution having the DIP sludge content shown in Table 6, and PD-1230 was added to the solution in a content of 200 ppm to prepare a pulp slurry. Then, the pulp slurry was subjected to a drainage test in the same manner as in Examples 1 to 6, and the filtrate turbidity and the drainage amount were measured. In Comparative Example 7, the pulp slurry was prepared in the same manner as in Examples 25 to 33 except that the modified raw material was not compounded and the DIP sludge content was adjusted as shown in Table 6, and the filtrate turbidity and the drainage amount were measured. In Reference Example 3, the pulp slurry was prepared in the same manner as in Examples 25 to 33 except that the modified raw material and the DIP sludge were not compounded, and the filtrate turbidity and the drainage amount were measured.

[0169] [Table 6]

[0170]

[0171] As shown in Table 6, it was found that even when 5 to 10% by weight of DIP float sludge as a low-quality raw material was compounded into the pulp slurry, the drainage and the filtrate turbidity were improved by chemically treating the DIP float sludge with the agents (1) to (3) of the present application. When 5% by weight of DIP float sludge was compounded, a sufficient effect was observed even when the addition amount was 2,000 ppm, and when 10% by weight of DIP float sludge was compounded, the effect was further improved by setting the addition amount to 4,000 ppm. Further, improvement in the drainage with the treatment with the agent (3) was observed, and, although the drainage with the treatment with the agent (1) was slightly inferior, the filtrate turbidity showed the best result.

[0172] <Examples 34 to 42, Comparative Example 8, and Reference Example 4>

[0173] Residual sludge (biologically treated residual sludge) generated from a papermaking paperboard plant was used as a low-quality raw material. Pulp slurry used for production of paperboard in the same papermaking paperboard plant was used as a papermaking raw material. In each of Examples 34 to 42, the agent shown in Table 7 was added to the residual sludge in the content shown therein to obtain a modified raw material, which was compounded with the papermaking raw material to obtain a solution having the residual sludge content shown in Table 7, and PD-1230 was added to the solution in a content of 200 ppm to prepare a pulp slurry. Then, the pulp slurry was subjected to a drainage test in the same manner as in Examples 1 to 6, and the filtrate turbidity and the drainage amount were measured. In Comparative Example 8, a pulp slurry was prepared in the same manner as in Examples 34 to 42 except that the modified raw material was not compounded and the residual sludge content was adjusted as shown in Table 7, and the filtrate turbidity and the drainage amount were measured. In Reference Example 4, a pulp slurry was prepared in the same manner as in Examples 34 to 42 except that the modified raw material and the residual sludge were not compounded, and the filtrate turbidity and the drainage amount were measured.

[0174] [Table 7]

[0175]

[0176] If the recovery and utilization of the excess sludge are promoted, the excess sludge as a low-quality raw material has a large economic benefit. However, the recovery and utilization are known to be the most difficult. As shown in Table 7, it was found from the results of Examples 34 to 42 that even when 5 to 10% by weight of the excess sludge as a low-quality raw material was compounded in the pulp slurry, the drainage and the filtrate turbidity were improved by chemically treating the excess sludge using the agents (1) to (3) of the present application. When 5% by weight of the excess sludge was compounded, a sufficient effect was observed even when the addition amount was 2,000 ppm, and when 10% by weight of the excess sludge was compounded, the effect was further improved by setting the addition amount to 4,000 ppm. Using the agent (1), further improvement was achieved by setting the addition amount to 6,000 ppm. The agent treatment with the agent (2) showed the best results in terms of the drainage.

[0177] From the above results, it was found that the best agent varies depending on the kind of the low-quality raw material. It also became apparent that the higher the concentration of the agent, the more remarkable the effect. The reason is considered to be that the amount and the charge state of the anionic substance vary depending on the kind of the low-quality raw material, and the manifestation of the effect varies depending on the kind of the agent.

[0178] According to the present application, a paper can be manufactured using a pulp slurry prepared by reusing a part of a low-quality raw material, which is usually treated as a waste, as a paper raw material; the low-quality raw material is a modified raw material obtained by treating with a specific agent; and the pulp slurry obtained by reusing the modified raw material has the same or better effect on the characteristics of the drainage and the turbidity as the pulp slurry obtained without reusing the modified raw material.

Claims

1. A papermaking method comprising using a pulp slurry prepared by reusing a portion of low-quality raw materials discharged in a papermaking step as a paper raw material, The low-quality raw material to be reused as paper raw material is a modified raw material treated with a specific agent, and The pulp slurry containing the upgraded raw material has better water filterability and turbidity characteristics than the pulp slurry containing untreated low-quality raw material that has not been treated with the specific agent.

2. The papermaking method according to claim 1, wherein the pulp slurry containing the upgraded raw material has the same or better water filterability and turbidity characteristics as the pulp slurry without reusing the low-quality raw material.

3. The paper manufacturing method according to claim 1 or 2, wherein the specific agent is any one of the following (1), (2) or (3): (1) a reaction product obtained by subjecting an acrylamide-based polymer to Hofmann degradation; (2) a copolymer of (meth)acrylic acid, (meth)acrylamide, and a quaternary ammonium adduct of dimethylaminoethyl acrylate, the copolymer having an intrinsic viscosity of 8.0 to 28.0 dl / g, a degree of cationization of 0.6 to 2.0 meq / g, a degree of anionization of 0.20 meq / g or less, and a cationic charge density / anionic charge density ratio of 5 to 20; and (3) a copolymer of (meth)acrylamide and a compound represented by the following chemical formula (I), the copolymer having an intrinsic viscosity of 8.0 to 28.0 dl / g and a degree of cationization of 0.6 to 3.0 meq / g, Chemical formula (I): R 1 -COO-C2H4-N(CH3)2-R 2 , where R 1 is CH2=CH- or CH2=C(CH3)-, R 2 is an alkyl group having 1 to 3 carbon atoms or a benzyl group, and they may be of the same kind or different kinds.

4. The paper manufacturing method according to claim 3, wherein the benzyl portion of the agent (3) has a cationization degree of 0.1 to 1.2 meq / g, and R 2 It's benzyl.

5. The paper manufacturing method according to claim 1 or 2, wherein the paper raw material is waste paper, cardboard or kraft paper.

6. The paper manufacturing method according to claim 1 or 2, wherein the reformed raw material obtained by treating the low-quality raw material with the specific agent is mixed with the pulp slurry.

7. The paper manufacturing method according to claim 6, wherein the specific agent is further added to the pulp slurry even after the reformed raw material is mixed with the pulp slurry.

8. A reagent for treating low-quality raw materials to be reused as paper raw materials for pulp slurry, The agent converts the low-quality raw material to be reused into an upgraded raw material, so that the water filterability and turbidity characteristics of the pulp slurry are improved.

9. The agent according to claim 8, wherein the agent is any one of the following (1), (2) or (3): (1) a reaction product obtained by subjecting an acrylamide-based polymer to Hofmann degradation; (2) a copolymer of (meth)acrylic acid, (meth)acrylamide, and a quaternary ammonium adduct of dimethylaminoethyl acrylate, the copolymer having an intrinsic viscosity of 8.0 to 28.0 dl / g, a degree of cationization of 0.6 to 2.0 meq / g, a degree of anionization of 0.20 meq / g or less, and a cationic charge density / anionic charge density ratio of 5 to 20; and (3) A copolymer of (meth)acrylamide and a compound represented by the following chemical formula (I), the copolymer having an intrinsic viscosity of 8.0 to 28.0 dl / g and a degree of cationization of 0.6 to 3.0 meq / g: Chemical formula (I): R 1 -COO-C2H4-N(CH3)2-R 2 , where R 1 is CH2=CH- or CH2=C(CH3)-, R 2 is an alkyl group having 1 to 3 carbon atoms or a benzyl group, and they may be of the same kind or different kinds.

10. The agent according to claim 9, wherein the benzyl moiety of the agent (3) has a degree of cationization of 0.1 to 1.2 meq / g, and R 2 It's benzyl.

Images