Dye fixing method

Abstract

The objective of the present invention is to provide a dye fixing method that uses a water-soluble polymer in papermaking raw materials before papermaking in the papermaking process, fixes a dye to pulp fibers, obtains an excellent dye fixing effect, and enables stable operation. [Solution] By adding a dye fixing agent containing a cationic water-soluble polymer with specific composition and physical properties, it is possible to obtain an excellent dye fixing effect, reduce the dye addition rate, and reduce the wastewater load caused by unfixed dye. It is more preferable to add the dye fixing agent to papermaking raw materials with a pulp dry solids concentration of 2.0 mass% or more, and it is also preferable to add it after the addition of the dye.

Description

[Technical Field]

[0001] The present invention relates to a method for fixing dyes to paper in the papermaking process, and more particularly to a method for fixing dyes to pulp fibers using a water-soluble polymer. [Background technology]

[0002] Dyes used in the papermaking process to impart color to paper are essential papermaking chemicals for producing high-quality paper. Among dyes, basic dyes and direct dyes are particularly commonly used in the papermaking process. It is known that aluminum sulfate is added before the dye to improve its fixation. However, due to the change in the papermaking environment from acidic to neutral papermaking and the possibility of scale formation due to calcium sulfate formation during the papermaking process, aluminum sulfate is increasingly being replaced. Therefore, various water-soluble polymer fixing agents have been devised as a substitute for or in addition to aluminum sulfate, which has traditionally been used as a dye fixing agent. For example, Patent Document 1 discloses the use of a paper dye fixing agent consisting of a specific cationic polymer having an amidine structure, which has a reduced viscosity of 0.1 to 10 dl / g when measured as a 0.1 g / dl solution in 1N saline at 25° C. However, in this case, the main focus of the study was on water resistance and light fastness as a dye fixing agent, rather than on further improving the vividness of the hue. In addition, fixing agents are often ineffective, and increasing the dye addition rate to improve dye fixation results in increased costs. Furthermore, unfixed dye ultimately causes a load on the drainage side, so there is a demand for a method of fixing dyes with even higher efficiency, and as a result, the desired vivid color (color difference) of paper due to dye fixation, which is the subject of this invention.

[0003] [Patent Document 1] JP 8-49190 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention aims to provide a dye fixing method that uses a dye fixing agent containing a water-soluble polymer in papermaking raw materials before papermaking in the papermaking process, fixes dyes to pulp fibers, obtains excellent coloring effects, and enables stable operation. [Means for solving the problem]

[0005] As a result of intensive research to solve the above problems, we have arrived at the invention described below. Specifically, we have discovered that dye fixation can be improved by adding a dye fixative containing a water-soluble polymer having specific composition and physical properties. [Effects of the Invention]

[0006] In the papermaking process, by adding a dye fixing agent containing a cationic water-soluble polymer with specific composition and physical properties to the papermaking raw material before papermaking, excellent dye fixing effects can be achieved and unfixed dye can be reduced, thereby reducing the amount of dye used and the load on the wastewater side. DETAILED DESCRIPTION OF THE INVENTION

[0007] The dye fixing agent containing a cationic water-soluble polymer in the present invention is produced by polymerizing an aqueous monomer mixture solution containing 10 to 80 mol % of a cationic monomer represented by the following general formula (1) and 20 to 90 mol % of a nonionic monomer. The content of the cationic monomer represented by general formula (1) is preferably 10 to 70 mol %, more preferably 15 to 60 mol %. This is because when the cationic monomer is in this range, the dye fixing effect is more easily obtained. JPEG2026040829000001.jpg2871 General formula (1) R1 is hydrogen or a methyl group, R2 and R3 are alkyl groups or alkoxy groups having 1 to 3 carbon atoms, and R4 is an alkyl group, alkoxy group, or aryl group having 7 to 20 carbon atoms, which may be the same or different. A represents oxygen or NH, B represents an alkylene group or alkoxy group having 2 to 4 carbon atoms, and X1 represents an anion.

[0008] The cationic monomer represented by general formula (1) is specifically a quaternized product of dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, or the like, with methyl chloride. Examples include (meth)acryloyloxyethyl trimethylammonium chloride, (meth)acryloyloxy-2-hydroxypropyl trimethylammonium chloride, (meth)acryloylaminopropyl trimethylammonium chloride, (meth)acryloyloxyethyl triethylammonium chloride, (meth)acryloyloxy-2-hydroxypropyl triethylammonium chloride, (meth)acryloylaminopropyl triethylammonium chloride, and (meth)acryloyloxyethyl dimethylbenzylammonium chloride. Two or more of these can also be used in combination. The molar amount of the cationic monomer represented by general formula (1) is in the range of 10 to 80 mol%.

[0009] Examples of nonionic monomers used in the present invention include (meth)acrylamide, N,N'-dimethylacrylamide, acrylonitrile, 2-hydroxyethyl (meth)acrylate, diacetone acrylamide, N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, acryloylmorpholine, etc. Two or more of these may be used in combination.

[0010] The cationic water-soluble polymer of the present invention may contain an anionic monomer during polymerization. However, since a large amount of anionic monomer inhibits the effect of the cationic water-soluble polymer, the amount of anionic monomer is preferably 10 mol % or less, more preferably 5 mol % or less, based on the total monomers. Examples of anionic monomers include one or more selected from vinyl sulfonic acid, vinylbenzenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, methacrylic acid, acrylic acid, itaconic acid, maleic acid, and salts thereof. Among these, acrylic acid or its salts are preferred. When using dicarboxylic acids, combining two or more types may result in poor molecular weight improvement.

[0011] The dye fixative of the present invention may be produced in any form by any known method. Specifically, it can be produced by copolymerizing a monomer mixture containing a cationic monomer and a nonionic monomer. Polymerization involves preparing an aqueous solution of the monomers, followed by dispersion polymerization, such as aqueous solution polymerization, water-in-oil emulsion polymerization, water-in-oil dispersion polymerization, or dispersion polymerization in saltwater. The product can then be produced in any form, such as an aqueous solution, water-in-oil emulsion, dispersion, saltwater dispersion, or powder. Among these polymerization methods, water-in-oil emulsion polymerization and dispersion polymerization are preferred, as they facilitate molecular weight control.

[0012] The water-in-oil emulsion can be produced appropriately by a polymerization method according to JP-A-59-130397, JP-A-10-140496, JP-A-2011-99076, etc. That is, a monomer mixture containing a cationic monomer and a nonionic monomer is mixed with water, an oily substance made of a hydrocarbon immiscible with water, and at least one surfactant having an HLB in an amount effective to form a water-in-oil emulsion, and the mixture is vigorously stirred to form a water-in-oil emulsion, followed by polymerization.

[0013] When the cationic water-soluble polymer of the present invention is prepared by dispersion polymerization in salt water, it can be appropriately produced in accordance with JP-A Nos. 62-20511, 61-123610, 62-15251, 2004-231822, etc. That is, the polymer is produced by dispersion polymerizing a mixture of cationic monomers and nonionic monomers in a salt water solution in the presence of a polymer dispersant soluble in the salt water solution.

[0014] The cationic water-soluble polymer of the present invention can be produced by dispersion polymerization in the presence of polyalkyleneimine and / or modified polyalkyleneimine. The production method can be a known method such as that described in JP-A No. 2004-044015 or JP-A No. 2004-26860. First, a 20-50% by mass aqueous solution of polyethyleneimine and / or modified polyethyleneimine is prepared, and 50-100% of the amine equivalent is neutralized with an organic or inorganic acid. The pH of the aqueous solution is adjusted to 2-12, and a monomer is added to the aqueous solution and mixed. The monomer concentration is 10-40% by mass, preferably 15-30% by mass. The amount of polyethyleneimine and / or modified polyethyleneimine relative to the monomer is 30-300% by mass, preferably 30-200% by mass, and more preferably 30-150% by mass. Modified polyalkyleneimine can also be used. Cationic water-soluble polymers produced by dispersion polymerization in the presence of polyalkyleneimine and / or modified polyalkyleneimine are particularly preferred as dye fixing agents because they have a high cationic degree, an excellent coagulation effect, a high molecular weight, and an excellent flocculation effect.

[0015] The cationic water-soluble polymer of the present invention may contain a crosslinkable monomer such as N,N'-methylenebis(meth)acrylamide or triallylamine as a structural modifier during or after polymerization.

[0016] The dye fixing agent containing a cationic water-soluble polymer of the present invention must have a predetermined cationic degree and mol % range to achieve a high dye fixing effect. The cationic degree of the dye fixing agent containing a cationic water-soluble polymer is measured using colloid titration. The dye fixing agent containing a cationic water-soluble polymer is dissolved in pure water, such as distilled water, to a concentration of 1% by mass based on the product concentration. After dissolution, the pH is adjusted to 3 with acetic acid, a drop of toluidine blue is added, and titration is performed with N / 400 potassium polyvinyl sulfate (PVSK). Titration is continued until the color change of the solution is complete, and the cationic degree per gram of polymer is calculated from the titrated amount of potassium polyvinyl sulfate. To enhance the coagulation effect of the dye fixing agent containing a cationic water-soluble polymer of the present invention, the cationic degree must be at least 1.3 (meq / g). To achieve a cationic degree of 1.3 (meq / g) or more, at least 10 mol % of the cationic monomer represented by general formula (1) in paragraph 0007 must constitute the structural unit. On the other hand, if the cationic degree exceeds 80 mol %, it becomes difficult to achieve a certain level of intrinsic viscosity during production. Therefore, the predetermined mol % is 10 mol % to 80 mol %, preferably 10 mol % to 70 mol %, and more preferably 15 mol % to 60 mol %.

[0017] The dye fixing agent containing a cationic water-soluble polymer in the present invention must have a certain molecular weight range to achieve a high dye fixing effect. In the present invention, molecular weight is expressed in terms of intrinsic viscosity. The dye fixing agent containing a cationic water-soluble polymer has an intrinsic viscosity in a 1N saline solution measured at 25°C ranging from 3 to 30 dL / g, preferably from 4 to 30 dL / g, and more preferably from 5 to 30 dL / g. An intrinsic viscosity below 3 dL / g significantly reduces the dye fixing effect, while an intrinsic viscosity above 30 dL / g tends to degrade paper quality, particularly formation, and is therefore undesirable. The weight-average molecular weight measured by the intrinsic viscosity method ranges from 1 million to 30 million, with 2 million to 30 million being preferred. Intrinsic viscosity is measured using a common device such as the Shibayama Scientific Machinery Works' Automatic Viscometer SS-120-L1. First, three solutions with different concentrations of 0.1% by mass or less are prepared by diluting the product concentration with 1N saline solution, for example, three solutions of 0.02%, 0.04%, and 0.06% by mass, and the reduced viscosity is measured at 25°C using a capillary viscometer. The reduced viscosity obtained is plotted on the vertical axis against the solution concentration on the horizontal axis to obtain an approximate line, and the value when the aqueous solution concentration is extrapolated to zero, that is, the intercept of the approximate line, is determined as the intrinsic viscosity.

[0018] Known dyes can be used in the method of the present invention, including water-soluble dyes such as direct dyes, basic dyes, acid dyes, and fluorescent dyes. Direct dyes and basic dyes are particularly preferred. Conventionally, dyes have been added to various locations in the papermaking process where the pulp dry solids concentration is 2.0% by mass or higher, such as refiners, raw material blending chests, mixing chests, machine chests, and seed boxes. A common method is to add a cationic water-soluble polymer as a dye fixative before aluminum sulfate to complement the effects of aluminum sulfate. In contrast, the dye fixative used in the present invention is preferably added after aluminum sulfate and the dye. This is because the dye is first fixed to the pulp fibers by aluminum sulfate. While the fixed dye gradually peels off in downstream processes, aqueous solutions of direct dyes, which generally contain azo dyes, are negatively charged. The coagulation and flocculation effects of the dye fixative added later promote the fixation of the dye to the pulp fibers, resulting in excellent dye fixation. In addition, aqueous solutions of basic dyes are generally cationic due to the presence of amines or quaternary ammonium salts, and it is believed that the fixing effect is achieved through electrostatic interactions such as hydrogen bonding with the nonionic moieties contained in the dye fixing agent. In the case of the dye fixing agent of the present invention, the specific composition and a certain range of physical properties improve the coagulation action, while the enhanced flocculation action makes the dye less likely to peel off and also improves the fixation of dyes attached to fine particles. Furthermore, even when aluminum sulfate is not added, adding the dye fixing agent of the present invention after adding the dye is more effective.

[0019] The dyes used in the papermaking process come in a variety of colors, including black, red, and yellow, but regardless of the type of color, the dye fixing mechanism using the dye fixing agent is thought to be as described in paragraph 0018.

[0020] The aluminum sulfate and dye may be added at the same location as the cationic water-soluble polymer, such as a seed box having a pulp dry solids concentration of 2.0% by mass or more, or at an upstream location such as a refiner, raw material blending chest, mixing chest, machine chest, etc. There are no particular restrictions on the order in which aluminum sulfate and dye are added, and they may be added simultaneously or in the order of dye and aluminum sulfate, preferably aluminum sulfate first.

[0021] Papermaking stock transported from upstream in the papermaking process with a pulp dry solids concentration of 2.0% by mass or more is diluted with white water or fresh water downstream just before the papermaking machine to a pulp dry solids concentration of less than 2.0% by mass. Typically, the stock is diluted to 0.5 to 1.5% by mass and passes through a fan pump and a screen before being transported to the papermaking machine and used for papermaking. The diluted papermaking stock just before being transported to the papermaking machine is called inlet stock or headbox stock, and these stocks can also be used in the present invention. In this case, the dye fixing agent is added after passing through the fan pump (the shearing process) and before or after passing through the screen. When the dye fixing agent of the present invention is added to papermaking stock diluted to a pulp dry solids concentration of 0.5 to 1.5% by mass, the paper texture may deteriorate depending on the papermaking conditions. Therefore, it is preferable to add the dye fixing agent to papermaking stock with a pulp dry solids concentration of 2.0% by mass or more.

[0022] The papermaking raw materials to which the method of the present invention can be applied are not particularly limited, and examples include newsprint, wood-free printing paper, medium-quality printing paper, gravure printing paper, PPC paper, coated base paper, lightly coated paper, packaging paper, and liner and core base paper boards. The method is particularly effective for paperboard raw materials, which are most required to be colored with dyes. In recent years, the flow rates of various dyes are sometimes automatically adjusted online in the papermaking process, but by using the dye fixative of the present invention, the flow rate of dyes can be reduced by automatic adjustment.

[0023] The dye fixing agent of the present invention is added in an amount of 5 to 2000 ppm, preferably 10 to 1000 ppm, expressed as pure polymer content relative to the dry solids content of the pulp. A concentration below 5 ppm makes it difficult to achieve dye fixing effects, while a concentration above 2000 ppm is undesirable because excessive amounts of dye fixing agent, which does not contribute to the dye fixing effect, can cause pitch problems during the papermaking process. The dye fixing agent of the present invention can also be used in combination with paper strength agents, sizing agents, coagulants, and other papermaking chemicals. In addition to the dye fixing effect, the dye fixing agent of the present invention may also exhibit pitch control effects, improved paper strength due to the paper strength agent fixing effect, improved sizing due to the sizing agent fixing effect, improved yield, and improved drainage. In recent years, the papermaking process has become increasingly automated and online, and this dye fixing agent can be incorporated into the automated process, which combines common analysis items for papermaking raw materials, such as pH, EC (electrical conductivity), turbidity, cation demand, anion demand, SS, Ash, SZP, etc., with paper quality information from the papermaking process, such as formation, basis weight, thickness, density, strength value, sizing value, and air permeability. The addition rate and flow rate of this dye fixing agent can also be incorporated into the automated process and adjustments, allowing for optimization. The dye fixing agent in the present invention is used by diluting and dissolving it in water to a concentration of 0.01 to 1.0% by mass, and any water such as distilled water, ion-exchanged water, tap water, or industrial water can be used. The addition rate of aluminum sulfate is in the range of 0.5 to 10 mass % as solids based on the papermaking raw material, and the addition rate of dyes is in the range of 0.0001 to 10 mass % as solids based on the papermaking raw material. [Example]

[0024] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0025] (Dye fixative sample) Dye fixing agent samples 1 to 7 of the present invention and comparative dye fixing agent samples 8 to 12 were prepared by standard methods such as aqueous solution polymerization, dispersion polymerization such as dispersion polymerization in salt water, and water-in-oil emulsion polymerization. Samples 1 and 2 were obtained by dispersion polymerization of a monomer mixture in a polyethyleneimine dispersion medium, and can be produced by known methods such as those described in JP-A Nos. 2004-044015 and 2004-26860. Their compositions and physical properties are shown in Table 1.

[0026] (Table 1) TIFF2026040829000002.tif72137 Product form: DR: Dispersion polymerization method such as dispersion polymerization in salt water, EM: Water-in-oil emulsion, P: Powder, AQ: Aqueous solution polymer Monomer composition: DMQ: acryloyloxyethyltrimethylammonium chloride, DMC: methacryloyloxyethyltrimethylammonium chloride, DMABC: acryloyloxyethyldimethylbenzylammonium chloride, DADMAC: diallyldimethylammonium chloride, AAM: acrylamide, AAC: acrylic acid Intrinsic viscosity: Intrinsic viscosity measured in 1N saline solution at 25°C. Cationicity: Colloid titration method (pH 3), cationicity per 1g of polymer Anionic degree: Colloid titration method (pH 10), anionic degree per 1g of polymer

[0027] Example 1 A dye fixation effect confirmation test was conducted on recycled cardboard raw material (pH 7.5, electrical conductivity 42 mS / m, cation demand measured with a BTG PCD05 model 32 μeq / L, dry solids concentration 2.09 mass%, beating degree 314 mL). Each sample listed in Table 1 was dissolved in pure water to 0.1 mass%. Aluminum sulfate and dyes were 100 mass% as they were, and were dissolved at 1 mass% for use in the test. These aqueous solutions were used in the tests. Approximately 300 mL of recycled cardboard raw material was placed in a 1-L plastic container and placed in a Britt-type dynamic jar tester. The following sequence was added: 2% by mass of aluminum sulfate (commercially available) was added and stirred at 300 rpm for 20 seconds; 0.7% by mass of a typical anionic direct dye (yellow: commercially available) used in the papermaking process was added and stirred at 300 rpm for 20 seconds; and 600 ppm of dye fixative sample 1 was added and stirred at 300 rpm for 10 seconds (all assuming addition to the container, with the addition rate based on the solid content of the papermaking raw material). 300 mL of clean water was then added to the plastic container, and after stirring at 300 rpm for 30 seconds, paper was made on a TAPPI standard paper machine (using an 80-mesh wire). The resulting wet paper was subjected to a pressure of 4.1 kgf / cm. 2 The paper was dewatered in a press for 5 minutes at 105°C, dried in a rotary drum dryer for 3 minutes, and then conditioned at 25°C and 65% RH for 18 hours, after which the color of the paper was measured. 2 The color of the paper was measured using a Technidyne ColorTouch PC (color difference meter). Similar tests were also carried out on Samples 2 and 3. These are Examples 1-1 to 1-3. The results are shown in Table 2.

[0028] Regarding the color of finished paper, L* indicates lightness, while a* and b* indicate chromaticity. Generally, a high b* indicates yellowish finished paper, a high a* indicates reddish finished paper, and a low L* indicates blackish finished paper. During the papermaking process, various dyes such as yellow, red, and black are added depending on the desired color of the finished paper. By using a dye fixative, it is possible to produce more vibrantly colored finished paper and reduce the amount of each dye used.

[0029] (Comparative Example 1) Using the same raw materials as in Example 1, tests similar to those in Example 1 were carried out using Samples 8 to 10 and Sample 12 in Table 1. These are designated Comparative Examples 1-1 to 1-4. The results are shown in Table 2.

[0030] (Table 2) TIFF2026040829000003.tif43131

[0031] As shown in Table 2, when Samples 1 to 3 of Example 1 were used, b* was higher and the degree of yellow dye fixation was higher than those of Samples 8 to 10 and Sample 12 of Comparative Example 1. From the physical properties perspective, it can be seen that a certain range of intrinsic viscosity and cationic degree is required to further improve the fixation of anionic yellow direct dyes. Sample 8 of Comparative Example 1 is a nonionic polymer sample, and although it has a higher intrinsic viscosity than Samples 1 and 2 of Example 1, if the cationic degree is 0, b* does not improve and the dye fixing effect is low. Additionally, Sample 12 of Comparative Example 1 is an anionic polymer sample, and since b* does not improve compared to Sample 1 of Example 1, the dye fixing effect of the anionic polymer sample is low.

[0032] Example 2 Approximately 300 mL of the same seed material as in Example 1-1 was collected in a 1-L plastic container and placed in a Britt-type dynamic jar tester. The dissolution method for various chemicals was the same as in Example 1-1. Then, 0.7 mass% of a common anionic direct dye (yellow: commercially available) used in the papermaking process was added, followed by stirring at 300 rpm for 20 seconds, 600 ppm of dye fixative sample 1 was added, followed by stirring at 300 rpm for 20 seconds, and 2 mass% of aluminum sulfate (commercially available) was added and stirred at 300 rpm for 10 seconds (all assuming addition to the seed box, with the addition rate relative to the solid content of the papermaking raw material). Then, 300 mL of clean water was added to the plastic container, and after stirring at 300 rpm for 30 seconds, paper was made on a TAPPI standard paper machine (using 80-mesh wire). The wet paper made was subjected to a pressure of 4.1 kgf / cm. 2 The paper was dewatered in a press for 5 minutes at 105°C, dried in a rotary drum dryer for 3 minutes, and then conditioned at 25°C and 65% RH for 18 hours, after which the color of the paper was measured. 2 The color of the paper was measured using a Technidyne ColorTouch PC (color difference meter). This is Example 2. The results are shown in Table 3.

[0033] Example 3 Approximately 300 mL of the same seed material as in Example 1 was collected in a 1-L plastic container and placed in a Britt-type dynamic jar tester. The dissolution method for various chemicals was the same as in Example 1-1. Then, 0.7% by mass of a common anionic direct dye (yellow: commercially available) used in the papermaking process was added and stirred at 300 rpm for 20 seconds, 2% by mass of aluminum sulfate (commercially available) was added and stirred at 300 rpm for 20 seconds, and 600 ppm of dye fixative Sample 1 was added and stirred at 300 rpm for 10 seconds (all assuming addition to the seed box, with the addition rate relative to the solid content of the papermaking raw material). Then, 300 mL of clean water was added to the plastic container, and after stirring at 300 rpm for 30 seconds, paper was made on a TAPPI standard paper machine (using 80-mesh wire). The wet paper made was subjected to a pressure of 4.1 kgf / cm. 2 The paper was dewatered in a press for 5 minutes at 105°C, dried in a rotary drum dryer for 3 minutes, and then conditioned at 25°C and 65% RH for 18 hours, after which the color of the paper was measured. 2 The color of the paper was measured using a Technidyne ColorTouch PC (color difference meter). This is Example 3. The results are shown in Table 3.

[0034] Example 4 Approximately 300 mL of the same seed material as in Example 1 was placed in a 1-L plastic container and placed in a Britt-type dynamic jar tester. The dissolution method for various chemicals was the same as in Example 1-1. Then, 600 ppm of dye fixative sample 1 was added, stirred at 300 rpm for 20 seconds, 2% by mass of aluminum sulfate (commercially available) was added, stirred at 300 rpm for 20 seconds, and 0.7% by mass of a common anionic direct dye (yellow: commercially available) used in the papermaking process was added, stirred at 300 rpm for 10 seconds (all assumed to be added in a seed box, with the addition rate relative to the solid content of the papermaking material). Then, 300 mL of clean water was added to the plastic container, stirred at 300 rpm for 30 seconds, and paper was made on a TAPPI standard paper machine (using 80-mesh wire). The wet paper made was subjected to a pressure of 4.1 kgf / cm. 2 The paper was dewatered in a press for 5 minutes at 105°C, dried in a rotary drum dryer for 3 minutes, and then conditioned at 25°C and 65% RH for 18 hours, after which the color of the paper was measured.2 The color of the paper was measured using a Technidyne ColorTouch PC (color difference meter). This is Example 4. The results are shown in Table 3.

[0035] (Comparative Example 2) Approximately 300 mL of the same seed material as in Example 1 was collected in a 1 L plastic container and placed in a Britt-type dynamic jar tester. The dissolution method for various chemicals was the same as in Example 1-1. The mixture was then stirred at 300 rpm for 20 seconds, 0.7 mass% of a common anionic direct dye (yellow: commercially available product) used in the papermaking process was added, stirred at 300 rpm for 20 seconds, and then stirred at 300 rpm for 10 seconds (all assuming addition to the seed box, with the addition rate based on the solid content of the papermaking raw material). 300 mL of fresh water was then added to the plastic container, and after stirring at 300 rpm for 30 seconds, paper was made on a TAPPI standard paper machine (using 80 mesh wire). The wet paper thus made was subjected to a pressure of 4.1 kgf / cm 2 The paper was dewatered in a press for 5 minutes at 105°C, dried in a rotary drum dryer for 3 minutes, and then conditioned at 25°C and 65% RH for 18 hours, after which the color of the paper was measured. 2 The color of the paper was measured using a Technidyne ColorTouch PC (color difference meter). This is Comparative Example 2. The results are shown in Table 3.

[0036] (Comparative Example 3) Approximately 300 mL of the same seed material as in Example 1 was collected in a 1 L plastic container and placed in a Britt-type dynamic jar tester. The dissolution method for various chemicals was the same as in Example 1-1. Then, 2% by mass of aluminum sulfate (commercially available) was added and stirred at 300 rpm for 20 seconds, followed by 0.7% by mass of a common anionic direct dye (yellow: commercially available) used in the papermaking process, and stirring at 300 rpm for 20 seconds, and stirring at 300 rpm for 10 seconds (all assuming addition to the seed box, with the addition rate based on the solid content of the papermaking raw material). Then, 300 mL of fresh water was added to the plastic container, and after stirring at 300 rpm for 30 seconds, paper was made on a TAPPI standard paper machine (using 80 mesh wire). The wet paper made was subjected to a pressure of 4.1 kgf / cm. 2The paper was dewatered in a press for 5 minutes at 105°C, dried in a rotary drum dryer for 3 minutes, and then conditioned at 25°C and 65% RH for 18 hours, after which the color of the paper was measured. 2 The color of the paper was measured using a Technidyne ColorTouch PC (color difference meter). This is Comparative Example 3. The results are shown in Table 3.

[0037] (Table 3) TIFF2026040829000004.tif40130

[0038] As shown in Table 3, Examples 1-1 and 2-4 show that the b* values ​​are higher and the degree of yellow dye fixation is higher than those of Comparative Examples 2-3. These results demonstrate that adding the dye fixative of the present invention is effective in improving the fixation of anionic yellow direct dyes. A comparison of Examples 1-1 and 2-3 with Example 4 also shows that a more preferred addition method is to add the dye fixative of the present invention after adding the yellow direct dye.

[0039] Example 5 A dye fixation effect confirmation test was conducted on paperboard raw material (pH 6.6, electrical conductivity 200mS / m, cation demand 70μeq / L measured with BTG PCD05, dry solids concentration 3.6% by mass). The sample was dissolved in pure water at 0.1% by mass. The dye was 100% by mass as is, and dissolved at 1% by mass for use in the test. These aqueous solutions were used in the test. Approximately 170 mL of the seed material was collected in a 1 L plastic container and placed in a Britt-type dynamic jar tester. Then, 0.7 mass% of a common cationic basic dye (yellow: commercially available) used in the papermaking process was added, followed by stirring at 400 rpm for 10 seconds, and then 600 ppm of dye fixative sample 1 was added and stirred at 400 rpm for 30 seconds (all assuming addition to the seed box, with the addition rate relative to the solid content of the papermaking raw material). Then, 510 mL of clean water was added to the plastic container, and after stirring at 300 rpm for 30 seconds, paper was made on a TAPPI standard paper machine (using 80 mesh wire). The wet paper made was subjected to a pressure of 4.1 kgf / cm. 2The paper was dewatered in a press for 5 minutes at 105°C, dried in a rotary drum dryer for 3 minutes, and then conditioned at 25°C and 65% RH for 18 hours, after which the color of the paper was measured. The basis weight of the paper was 96 g / m 2 The color of the paper was measured using a Technidyne ColorTouch PC (color difference meter). This is Example 5. The results are shown in Table 4.

[0040] Comparative Example 4 Approximately 170 mL of the same seed material as in Example 5 was collected in a 1 L plastic container and placed in a Britt-type dynamic jar tester. Then, 0.7 mass% of a common cationic basic dye (yellow: commercially available product) used in the papermaking process was added (assuming addition to a seed box, the addition rate is based on the solid content of the papermaking raw material), and the mixture was stirred at 400 rpm for 40 seconds. Then, 510 mL of fresh water was added to the plastic container, and after stirring at 300 rpm for 30 seconds, paper was made on a TAPPI standard paper machine (using 80 mesh wire). The wet paper made was subjected to a pressure of 4.1 kgf / cm. 2 The paper was dewatered in a press for 5 minutes at 105°C, dried in a rotary drum dryer for 3 minutes, and then conditioned at 25°C and 65% RH for 18 hours, after which the color of the paper was measured. The basis weight of the paper was 96 g / m 2 The color of the paper was measured using a Technidyne ColorTouch PC (color difference meter). This is Comparative Example 4. The results are shown in Table 4.

[0041] (Table 4) TIFF2026040829000005.tif21116

[0042] As shown in Example 5 of Table 4, the addition of Sample 1 resulted in a higher b* value and a higher dye fixation degree of the yellow basic dye than in Comparative Example 4 where no sample 1 was added.

[0043] Example 6 Approximately 170 mL of the same seed material as in Example 5 was collected in a 1 L plastic container and placed in a Britt-type dynamic jar tester. Then, 0.7 mass% of a common anionic direct dye (black: commercially available product) used in the papermaking process was added, stirred for 10 seconds at 400 rpm, and 600 ppm of dye fixative Sample 1 was added and stirred for 30 seconds at 400 rpm (assuming addition to a seed box, addition rate relative to the solid content of the papermaking raw material). Then, 510 mL of clean water was added to the plastic container, stirred for 30 seconds at 300 rpm, and paper was made on a TAPPI standard paper machine (using 80 mesh wire). The wet paper made was subjected to a pressure of 4.1 kgf / cm. 2 The paper was dewatered in a press for 5 minutes at 105°C, dried in a rotary drum dryer for 3 minutes, and then conditioned at 25°C and 65% RH for 18 hours, after which the color of the paper was measured. The basis weight of the paper was 94 g / m 2 The color of the paper was measured using a Technidyne ColorTouch PC (color difference meter). This is Example 6. The results are shown in Table 5.

[0044] (Comparative Examples 5-1 and 5-2) Approximately 170 mL of the same seed material as in Example 5 was collected in a 1 L plastic container and placed in a Britt-type dynamic jar tester. Then, 0.7 mass% of a common anionic direct dye (black: commercially available product) used in the papermaking process was added, stirred for 10 seconds at 400 rpm, and 600 ppm of dye fixative Sample 11 was added and stirred for 30 seconds at 400 rpm (assuming addition to a seed box, addition rate relative to the solid content of the papermaking raw material). Then, 510 mL of clean water was added to the plastic container, stirred for 30 seconds at 300 rpm, and paper was made on a TAPPI standard paper machine (using 80 mesh wire). The wet paper made was subjected to a pressure of 4.1 kgf / cm. 2 The paper was dewatered in a press for 5 minutes at 105°C, dried in a rotary drum dryer for 3 minutes, and then conditioned at 25°C and 65% RH for 18 hours, after which the color of the paper was measured. The basis weight of the paper was 94 g / m 2 The color of the paper was measured using a Technidyne ColorTouch PC (color difference meter). This is Comparative Example 5-1. Comparative Example 5-2 was carried out in the same manner, but without adding Sample 11. The results are shown in Table 5.

[0045] (Table 5) TIFF2026040829000006.tif21102

[0046] As shown in Example 6 of Table 5, the addition of Sample 1 resulted in a lower L* and a higher dye fixation degree of the anionic black dye than Comparative Examples 5-1 and 5-2.

[0047] Example 7 A dye fixing effect confirmation test was conducted on LBKP seed raw material (pH 7.9, electrical conductivity 12 mS / m, cation demand 40 μeq / L measured by BTG PCD05, dry solids concentration 2.1% by mass). The sample was dissolved in pure water at 0.1% by mass. The dye was 100% by mass as is, and dissolved at 1% by mass for use in the test. These aqueous solutions were used in the test. Approximately 300 mL of the seed material was collected in a 1 L plastic container and placed in a Britt-type dynamic jar tester. Then, 0.35 mass% of a common anionic direct dye (red: commercially available) used in the papermaking process was added, followed by stirring at 400 rpm for 10 seconds, and then 300 ppm of dye fixative sample 1 was added and stirred at 400 rpm for 30 seconds (all assuming addition to the seed box, with the addition rate relative to the solid content of the papermaking raw material). Then, 500 mL of clean water was added to the plastic container, and after stirring at 300 rpm for 30 seconds, paper was made on a TAPPI standard paper machine (using 80 mesh wire). The wet paper made was subjected to a pressure of 4.1 kgf / cm. 2 The paper was dewatered in a press for 5 minutes at 105°C, dried in a rotary drum dryer for 3 minutes, and then conditioned at 25°C and 65% RH for 18 hours, after which the color of the paper was measured. The basis weight of the paper was 116 g / m 2 The color of the paper was measured using a Technidyne ColorTouch PC (color difference meter). This is Example 7. The results are shown in Table 6.

[0048] (Comparative Example 6) Approximately 300 mL of the same seed material as in Example 7 was placed in a 1 L plastic container and placed in a Britt-type dynamic jar tester. The dye was 100% by mass as is and dissolved to 1% by mass for use in the test. Next, 0.35% by mass of a common anionic direct dye (red: commercially available product) used in the papermaking process was added (assuming addition to a seed box, the addition rate was based on the solid content of the papermaking raw material), and the mixture was stirred at 400 rpm for 40 seconds. 500 mL of clean water was then added to the plastic container, and the mixture was stirred at 300 rpm for 30 seconds, after which paper was made on a TAPPI standard paper machine (using an 80 mesh wire). The wet paper was subjected to a pressure of 4.1 kgf / cm. 2 The paper was dewatered in a press for 5 minutes at 105°C, dried in a rotary drum dryer for 3 minutes, and then conditioned at 25°C and 65% RH for 18 hours, after which the color of the paper was measured. The basis weight of the paper was 116 g / m 2 The color of the paper was measured using a Technidyne ColorTouch PC (color difference meter). This is Comparative Example 6. The results are shown in Table 6.

[0049] (Table 6) TIFF2026040829000007.tif1899

[0050] As shown in Example 7 of Table 6, the addition of Sample 1 resulted in a higher a* value and a higher degree of dye fixation of the red dye compared to Comparative Example 6 where no sample 1 was added.

[0051] Example 8 A dye fixing effect confirmation test was conducted using the same LBKP seed raw material as in Example 7. The sample was dissolved in pure water at 0.1% by mass. The dye was 100% by mass as is and dissolved at 1% by mass for use in the test. These aqueous solutions were used in the test. Approximately 300 mL of the seed material was collected in a 1 L plastic container and placed in a Britt-type dynamic jar tester. Then, 0.35 mass% of a common anionic direct dye (red: commercially available) used in the papermaking process was added, followed by stirring at 400 rpm for 10 seconds, and then 600 ppm of dye fixative sample 1 was added and stirred at 400 rpm for 30 seconds (both assumed to be added in a seed box, with the addition rate based on the solid content of the papermaking raw material). Then, 500 mL of clean water was added to the plastic container, and after stirring at 300 rpm for 30 seconds, paper was made on a TAPPI standard paper machine (using 80 mesh wire). The wet paper made was subjected to a pressure of 4.1 kgf / cm. 2The paper was dewatered in a press for 5 minutes at 105°C, dried in a rotary drum dryer for 3 minutes, and then conditioned at 25°C and 65% RH for 18 hours, after which the texture and color of the finished paper were measured. The basis weight of the finished paper was 120 g / m 2 The formation was measured using a formation tester FMT-4 manufactured by Nomura Shoji Co., Ltd. A lower measured value for the formation is better when using the FMT-4. The color of the paper was measured using a ColorTouch PC (color difference meter) manufactured by Technidyne. This is Example 8. The results are shown in Table 7.

[0052] Example 9 A dye fixing effect confirmation test was conducted using the same LBKP seed raw material as in Example 7. The sample was dissolved in pure water at 0.1% by mass. The dye was 100% by mass as is and dissolved at 1% by mass for use in the test. These aqueous solutions were used in the test. Approximately 300 mL of the seed material was placed in a 1 L plastic container and placed in a Britt-type dynamic jar tester. Next, 0.35% by mass of a common anionic direct dye (red: commercially available) used in the papermaking process was added, followed by stirring at 400 rpm for 40 seconds. 500 mL of clean water was then added to the plastic container, and after stirring at 300 rpm for 20 seconds, 600 ppm of Sample 1 dye fixative was added, followed by stirring at 300 rpm for 10 seconds (assuming the S / C outlet, the addition rate is relative to the solid content of the papermaking raw material). Paper was made on a TAPPI standard paper machine (using an 80 mesh wire). The wet paper was subjected to a pressure of 4.1 kgf / cm. 2 The paper was dewatered in a press for 5 minutes at 105°C, dried in a rotary drum dryer for 3 minutes, and then conditioned at 25°C and 65% RH for 18 hours, after which the texture and color of the finished paper were measured. The basis weight of the finished paper was 120 g / m 2 The formation was measured using a formation tester FMT-4 manufactured by Nomura Shoji Co., Ltd. A lower measured value for the formation is better when using the FMT-4. The color of the paper was measured using a ColorTouch PC (color difference meter) manufactured by Technidyne. This is Example 9. The results are shown in Table 7.

[0053] (Comparative Example 7) A dye fixing effect confirmation test was conducted using the same LBKP seed raw material as in Example 7. The sample was dissolved in pure water at 0.1% by mass. The dye was 100% by mass as is and dissolved at 1% by mass for use in the test. These aqueous solutions were used in the test. Approximately 300 mL of the seed material was collected in a 1 L plastic container and placed in a Britt-type dynamic jar tester. Then, 0.35 mass% of a common anionic direct dye (red: commercially available) used in the papermaking process was added, and the mixture was stirred at 400 rpm for 40 seconds (all figures are assumed to be added in a seed box, and the addition rate is based on the solid content of the papermaking raw material). Then, 500 mL of fresh water was added to the plastic container, and the mixture was stirred at 300 rpm for 30 seconds, after which papermaking was carried out on a TAPPI standard papermaking machine (using an 80 mesh wire). The wet paper thus produced was subjected to a pressure of 4.1 kgf / cm. 2 The paper was dewatered in a press for 5 minutes at 105°C, dried in a rotary drum dryer for 3 minutes, and then conditioned at 25°C and 65% RH for 18 hours, after which the texture and color of the finished paper were measured. The basis weight of the finished paper was 120 g / m 2 The formation was measured using a formation tester FMT-4 manufactured by Nomura Shoji Co., Ltd. A lower measured value for the formation is better when using the FMT-4. The color of the paper was measured using a ColorTouch PC (color difference meter) manufactured by Technidyne. This is Comparative Example 7. The results are shown in Table 7.

[0054] (Table 7) TIFF2026040829000008.tif31129

[0055] As shown in Examples 8 to 9 in Table 7, adding Sample 1 resulted in a higher a* value and a higher degree of red dye fixation compared to Comparative Example 7. Regarding a more preferable addition method, Example 9 worsened the paper texture more than Example 8. This deterioration in texture can lead to a decrease in paper strength or sizing effect in terms of paper quality. Therefore, when considering a formulation that is less likely to deteriorate the texture, it is preferable to add the dye fixative of the present invention to a papermaking raw material with a pulp dry solids concentration of 2.0% by mass or more.

[0056] Example 10 A dye fixation effect confirmation test was conducted on recycled cardboard raw material (pH 7.9, electrical conductivity 30 mS / m, cation demand measured with BTG PCD05 59 μeq / L, dry solids concentration 2.29 mass%, beating degree 312 mL). Each sample listed in Table 1 was dissolved in pure water to 0.1 mass%. The dye was 100 mass% as is, and was dissolved at 1 mass% for use in the test. These aqueous solutions were used in the tests. Approximately 280 mL of the seed material was collected in a 1 L plastic container and placed in a Britt-type dynamic jar tester. Then, 0.4 mass% of a common cationic basic dye (yellow: commercially available) used in the papermaking process was added, and the mixture was stirred at 300 rpm for 20 seconds. Then, 250 ppm of dye fixative sample 1 was added, and the mixture was stirred at 300 rpm for 10 seconds (all assuming addition to the seed box, with the addition rate relative to the solid content of the papermaking raw material). Then, 400 mL of clean water was added to the plastic container, and the mixture was stirred at 300 rpm for 30 seconds. Then, papermaking was performed on a TAPPI standard papermaking machine (using 80 mesh wire). The wet paper thus made was subjected to a pressure of 4.1 kgf / cm. 2 The paper was dewatered in a press for 5 minutes at 105°C, dried in a rotary drum dryer for 3 minutes, and then conditioned at 25°C and 65% RH for 18 hours, after which the color of the paper was measured. 2 The color of the paper was measured using a Technidyne ColorTouch PC (color difference meter). Similar tests were also carried out on Samples 4 to 7. These are Examples 10-1 to 10-5. The results are shown in Table 8.

[0057] (Comparative Example 8) Using the same raw materials as in Example 10, tests similar to those in Example 10 were carried out using Samples 9 and 11 in Table 1. These were designated Comparative Examples 8-1 and 8-2. The results are shown in Table 8.

[0058] (Table 8) TIFF2026040829000009.tif31110

[0059] As shown in Table 8, when Sample 1 and Samples 4 to 7 of Example 10 were used, b* was higher and the degree of yellow dye fixation was higher than those of Sample 9 and Sample 11 of Comparative Example 8. From the physical properties perspective, it can be seen that a certain range of intrinsic viscosity and cationicity is required to further improve the fixation of cationic yellow basic dyes.

[0060] From these results, it was found that the dye fixing effect was improved when the dye fixing agent of the present invention was added.

[0061] The dye fixing method of the present invention provides an excellent dye fixing effect, which allows the dye addition rate to be reduced and makes it possible to reduce the wastewater load caused by unfixed dye.

Claims

1. A method for fixing a dye, comprising adding a dye fixing agent to a papermaking raw material before papermaking in a papermaking process, the dye fixing agent comprising a cationic water-soluble polymer having constituent units of 10 to 80 mol % of a cationic monomer represented by the following general formula (1) and 20 to 90 mol % of a nonionic monomer, the cationic water-soluble polymer having an intrinsic viscosity in a 1 N saline solution measured at 25°C in the range of 3 to 30 dL / g: General formula (1) R １ is hydrogen or a methyl group, R ２ , R ３ is an alkyl group or alkoxy group having 1 to 3 carbon atoms, R ４ are alkyl groups or alkoxy groups having 1 to 3 carbon atoms, or aryl groups having 7 to 20 carbon atoms, and may be the same or different. A is oxygen or NH, B is an alkylene group or alkoxylene group having 2 to 4 carbon atoms, and X １ represents an anion, respectively.

2. 2. The method for fixing a dye according to claim 1, wherein the dye fixing agent is added to a papermaking raw material having a pulp dry solids concentration of 2.0% by mass or more.

3. 2. The method for fixing a dye according to claim 1, wherein the dye fixing agent is added after the dye is added.

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