Paper density adjuster

Abstract

To provide a paper density controlling agent capable of controlling paper density without using epichlorohydrin as a raw material and further imparting excellent size property.SOLUTION: A paper density controlling agent of the present invention is a paper density controlling agent containing an amide ammonium salt obtained by reacting a dialkyl sulfate with an amide amine obtained by reacting a polyamine with a fatty acid, wherein the fatty acid has a carbon number of 14-22, a reaction molar ratio of the fatty acid is 0.3-0.8 to an active amino group in the polyamine, a reaction molar ratio of the dialkyl sulfate to an active amino group in the amide amine is 0.1 mole or over and under 1 mole, the amide ammonium salt is an ammonium salt of tertiary or under, and the paper density controlling agent does not substantially contain epichlorohydrin and a compound having a chemical structure derived from epichlorohydrin.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a paper density adjuster used for paper.

Background Art

[0002] The paper manufacturing industry is an equipment industry, and basically all manufacturing is carried out through a paper machine. Since usually only one type of paper can be manufactured from one paper machine, it is often difficult to finely change the paper quality according to customer requirements only by mechanical adjustment. Therefore, a method of controlling the quality such as water repellency, coloring, softness, and strength by adding a chemical during the process is used.

[0003] In recent years, against the background of the shortage of pulp resources, the soaring pulp price, and the need for global environmental protection, in order to suppress the use of pulp as much as possible, in order to increase the bulk (thickness) and reduce the use of pulp as a raw material, a paper density adjuster is added as a chemical. The main component of paper, cellulose (β-1,4-glucose), is bonded by intermolecular hydrogen bonds. By adsorbing the paper density adjuster to this part and weakening the intermolecular binding force, a space is created between the fibers to increase the bulk and lower the density.

[0004] Conventionally, amidoamines obtained by reacting polyamines and fatty acids and their salts have been proposed as paper density adjusters, which are chemicals added for the purpose of reducing the density of paper and increasing the volume (Patent Documents 1 to 4).

[0005] Patent Document 1 discloses a paper density adjuster using amidoamine, Patent Document 2 discloses a quaternary ammonium salt obtained by quaternizing amidoamine using a bifunctional alkyl halide or the like as an alkylating agent, and Patent Documents 3 and 4 disclose amidoamine and its acid salts, and a quaternary ammonium salt obtained by quaternizing amidoamine using an excessive amount of a quaternizing agent such as methyl chloride as an alkylating agent with respect to the active amino group.

[0006] Conventionally, paper density regulators have been used in printing paper and the like. However, the use of paper density regulators may impair the effect of sizing agents that control the water absorbency of paper to prevent bleeding of water-based inks and impart high writing and printing properties to the paper. In addition to adjusting the paper density, performance that contributes to the sizing effect is also required. However, in the technologies of Patent Documents 1 to 4, the reaction molar ratio of fatty acids to active amino groups in polyamines, the reaction molar ratio of alkylating agents to active amino groups in amidoamines, which are amidated products of polyamines and fatty acids, and the types of alkylating agents were not sufficiently studied, and none of them had excellent sizing performance. In particular, quaternary amine compounds had a problem of significantly inhibiting sizing performance and poor printing quality.

[0007] There are various types of paper density regulators, such as non-ionic ester type and polymer compound type. However, many of them use epichlorohydrin as a raw material. For example, compounds obtained by reacting epihalohydrin with fatty acid polyamidoamine, or compounds obtained by reacting epihalohydrin and alkyl halide with aminoacrylamide of (meth)acrylic acid also use epichlorohydrin as a raw material, and a trace amount of epichlorohydrin is also contained in the preparation. Since the wastewater discharged through the papermaking process containing this epichlorohydrin is released into rivers, leading to environmental pollution, epichlorohydrin has been designated as a substance subject to monitoring in Japan, and there is a possibility that wastewater standards will be established in the future. Therefore, a paper density regulator that does not use epichlorohydrin has been demanded.

[0008] Patent Document 5 proposes a mixture of a first amino compound obtained by reacting a dialkyl sulfate with a compound obtained by reacting a polyamine compound and a fatty acid, and a second amino compound obtained by reacting an epihalohydrin, for the purpose of obtaining low-density paper with less strength reduction, or a third amino compound obtained by reacting an epihalohydrin and a dialkyl sulfate.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0010] However, since epichlorohydrin is used, there are concerns about its impact on the environment in industrial wastewater and the like. Also, although the aim is to reduce strength degradation, sufficient consideration has not been given to sizing performance. In particular, the first amino compound is a quaternary compound using an excessive amount of dialkyl sulfate. As described above, amine quaternary compounds significantly inhibit sizing performance and have the problem of poor printing quality. Furthermore, when a mixture of the first amino compound and the second amino compound is emulsified at a high concentration, it becomes a paste or gel-like state, and there are difficulties in handling during actual use.

[0011] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a paper density adjuster that can adjust paper density without using epichlorohydrin as a raw material and has excellent sizing performance.

Means for Solving the Problems

[0012] As a result of intensive studies to solve the above problems, the inventors of the present invention found that by reacting a polyamine with a fatty acid having a specific number of carbon atoms to obtain an amidoamine, using dialkyl sulfate as an alkylating agent, and setting the reaction molar ratio of the fatty acid to the active amino groups (-NH2, -NH-) in the polyamine and the reaction molar ratio of dialkyl sulfate to the active amino groups in the amidoamine within specific ranges, and forming an amidoammonium salt which is a quaternary ammonium salt or lower, it is possible to adjust the paper density without using epichlorohydrin as a raw material and to exhibit further excellent sizing performance, thus completing the present invention.

[0013] That is, in order to solve the above problems, the paper density regulator of the present invention is a paper density regulator containing an amidoammonium salt obtained by reacting an amidoamine obtained by reacting a polyamine with a fatty acid with dialkyl sulfate, wherein the fatty acid has 14 to 22 carbon atoms, the reaction molar ratio of the fatty acid is 0.3 to 0.8 with respect to the active amino groups in the polyamine, the reaction molar ratio of the dialkyl sulfate is 0.1 mole or more and less than 1 mole with respect to the active amino groups in the amidoamine, the amidoammonium salt is a quaternary ammonium salt or lower, and the paper density regulator is substantially free of epichlorohydrin and compounds having a chemical structure derived from epichlorohydrin.

Effects of the Invention

[0014] According to the paper density regulator of the present invention, it is possible to adjust the paper density without using epichlorohydrin as a raw material, and it is further excellent in sizing performance.

Modes for Carrying Out the Invention

[0015] Specific embodiments of the present invention will be described below. In this specification, "~" defining a numerical range indicates above and below.

[0016] The paper density regulator of the present invention contains an amidoammonium salt obtained by reacting an amidoamine obtained by reacting a polyamine and a fatty acid with dialkyl sulfate.

[0017] In the paper density regulator of the present invention, the polyamine is not particularly limited, but has a plurality of amino groups. Each amino group may be primary, secondary, or tertiary, but is preferably primary or secondary. For example, the plurality of amino groups may be linked via a divalent hydrocarbon group, and the amino groups at both ends may be primary amino groups or secondary amino groups to which a monovalent hydrocarbon group is bonded. Among these, the amino groups at both ends are preferably primary amino groups.

[0018] The number of amino groups in the polyamine is preferably 3 to 8, more preferably 3 to 5. The divalent hydrocarbon group is preferably an aliphatic hydrocarbon group, more preferably an alkylene group. When there are a plurality of divalent hydrocarbon groups, they may be the same or different, and the number of carbon atoms thereof is preferably 1 to 4, more preferably 2 or 3, and still more preferably 2. When having a monovalent hydrocarbon group at the end, the monovalent hydrocarbon group is preferably an aliphatic hydrocarbon group, more preferably an alkyl group. When there are a plurality of monovalent hydrocarbon groups, they may be the same or different, and the number of carbon atoms thereof is preferably 1 to 22, more preferably 1 to 10, and still more preferably 1 to 4. The polyamine may contain a branched structure or a cyclic structure, but a straight chain is preferred. The polyamine may be used alone or in combination of two or more.

[0019] The polyamine is preferably a polyalkylene polyamine represented by the following formula (I). This polyalkylene polyamine is excellent in the effect of adjusting the paper density by the amidoammonium salt and the handleability of the paper density regulator prepared by emulsification.

[0020]

Chemical formula

[0021] As the alkylene group R, specifically, a methylene group, an ethylene group, a trimethylene group, and a tetramethylene group can be mentioned. Preferably, R is an ethylene group. As the polyalkylene polyamine represented by the formula (I), specifically, for example, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, etc. can be mentioned.

[0022] In the paper density regulator of the present invention, the fatty acid has 14 to 22 carbon atoms. The lower limit of the carbon number is preferably 16 or more. The upper limit of the carbon number is preferably 20 or less. When the carbon number is within this range, the paper density adjustment effect and sizing performance by the amidoammonium salt are excellent.

[0023] The fatty acid may be either linear or branched. Preferably, it is linear. The fatty acid may be either saturated or unsaturated. Preferably, it is a saturated fatty acid. The fatty acid may be used alone or in combination of two or more.

[0024] Specific examples of the fatty acid include, for example, myristic acid, isomyristic acid, myristoleic acid, pentadecanoic acid, palmitic acid, isopalmitic acid, palmitoleic acid, margaric acid, stearic acid, isostearic acid, oleic acid, linoleic acid, linolenic acid, arachidic acid, behenic acid, erucic acid, etc. Also, mixed fatty acids derived from natural oils and fats and their hydrogenated products, etc. can be mentioned.

[0025] In the paper density regulator of the present invention, the reaction molar ratio of the fatty acid is 0.3 to 0.8 with respect to the active amino groups in the polyamine. Preferably, it is 0.4 to 0.8, and more preferably 0.5 to 0.8. When the molar ratio is within this range, the paper density adjustment effect and sizing performance by the amidoammonium salt are excellent. Also, the handleability of the paper density regulator prepared by emulsification is excellent.

[0026] The reaction between polyamine and fatty acid is carried out, for example, in a solvent such as water, optionally using a catalyst, and amidation is carried out by dehydration to produce amidoamine. The reaction temperature is not particularly limited, but considering the efficiency of the reaction, etc., 180 to 210 °C is preferable. In this reaction, a part of the amidoamine may cyclize to form a cyclic compound by imidazolinization of the amide and the amine adjacent thereto, but it is preferable to ring-open by means such as cooling, adding water, and stirring for a predetermined time. The amidoamine used in the reaction with dialkyl sulfate preferably has a ratio of tertiary amine value to total amine value of 0.8 or less, more preferably 0.5 or less, still more preferably 0.3 or less, and most preferably 0.1 or less.

[0027] In the paper density regulator of the present invention, dialkyl sulfate cationizes the amino group of amidoamine to a tertiary or lower level. The dialkyl sulfate preferably has 1 to 5 carbon atoms in the alkyl group, more preferably 1 to 3 carbon atoms. When the carbon number is in this range, the paper density adjustment effect, sizing performance, and handleability by the amidoammonium salt are excellent. The dialkyl sulfate may be used alone or in combination of two or more.

[0028] The dialkyl sulfate is not particularly limited, and examples thereof include dimethyl sulfate, diethyl sulfate, dipropyl sulfate, diisopropyl sulfate, etc. Among these, dimethyl sulfate and diethyl sulfate are preferable.

[0029] The paper density regulator of the present invention has a reaction molar ratio of dialkyl sulfate of 0.1 mol or more and less than 1 mol with respect to the active amino groups in the amidoamine. Preferably, it is 0.1 to 0.8, more preferably 0.15 to 0.75. When the molar ratio is within this range, the paper density adjustment effect and sizing performance by the amidoammonium salt are excellent. Also, the handleability of the paper density regulator prepared by emulsification is excellent. When the reaction molar ratio of dialkyl sulfate is 0.1 mol or more, the cationicity of the amidoammonium salt increases, and the effect of reducing the density is improved by electrostatic adsorption to the pulp. When the reaction molar ratio of dialkyl sulfate is less than 1 mol, it is not quaternized and an appropriate hydrophobicity is imparted, and the sizing performance by the amidoammonium salt is excellent.

[0030] The reaction between the amidoamine and dialkyl sulfate is carried out, for example, using a solvent such as water as necessary, alkylating the amine to form a tertiary or lower salt, thereby generating an amidoammonium salt. Dialkyl sulfate may be added dropwise to the solution of the amidoamine. The reaction temperature is not particularly limited, but considering the efficiency of the reaction, etc., 110 to 130 °C is preferable.

[0031] The paper density regulator of the present invention has an amidoammonium salt that is a tertiary or lower ammonium salt. When it is a tertiary or lower ammonium salt, an appropriate hydrophobicity is imparted, and the sizing performance by the amidoammonium salt is excellent. Also, by cationization, electrostatic adsorption to the pulp is promoted and the effect of adjusting the paper density is improved.

[0032] In the present invention, the amidoammonium salts that are tertiary or lower ammonium salts include the following (1) to (4). (1) An amidoammonium salt in which all the salt structures in the molecule are tertiary ammonium salts (2) An amidoammonium salt in which all the salt structures in the molecule are tertiary ammonium salts and secondary ammonium salts (3) A mixture of (1) and (2) above (4) A mixture of an amidoammonium salt of either (1) or (2) above and an amidoammonium salt in which all the salt structures in the molecule are secondary ammonium salts (5) An amide ammonium salt in which all salt structures within the molecule are secondary ammonium salts

[0033] The paper density regulator of the present invention substantially does not contain epichlorohydrin and compounds having a chemical structure derived from epichlorohydrin. The paper density regulator of this embodiment is excellent in the effect of adjusting paper density by the amide ammonium salt and further excellent in sizing performance without using epichlorohydrin as a raw material. Conventional paper density regulators using epichlorohydrin as a raw material contained trace amounts of epichlorohydrin in the formulation. Since the wastewater discharged through the papermaking process containing this epichlorohydrin is released into rivers, leading to environmental pollution, epichlorohydrin has been designated as a substance subject to monitoring in our country. However, according to the paper density regulator of this embodiment, even if future wastewater standards are established, it can meet the standards and provide a paper density regulator capable of addressing environmental problems.

[0034] Here, substantially not containing means the following. For epichlorohydrin, the content in the paper density regulator is 3 ppm or less, preferably 0.3 ppm or less, more preferably 0.03 ppm or less, and even more preferably does not contain epichlorohydrin. For compounds having a chemical structure derived from epichlorohydrin, the content in the paper density regulator is 110 ppm or less, preferably 10 ppm or less, more preferably 1 ppm or less, and even more preferably does not contain the compound. Compounds having a chemical structure derived from epichlorohydrin are not particularly limited. For example, amide ammonium salts obtained by reacting at least epichlorohydrin with amide amines obtained by reacting polyamines and fatty acids, compounds obtained by reacting epihalohydrins and alkyl halides with aminoacrylamides of (meth)acrylic acid, etc. can be mentioned.

[0035] In a preferred embodiment, the total amine value of the amide ammonium salt in the paper density regulator of the present invention is 5 to 120. Preferably, the total amine value is 7 to 100, more preferably 10 to 90. The total amine value can be measured by the method described in the Examples section below.

[0036] When the total amine value of the amide ammonium salt is 1 or more, it is a salt of tertiary or lower and does not quaternize. When the total amine value is 5 or more, appropriate hydrophobicity is imparted, and the size performance by the amide ammonium salt is excellent. When the total amine value is 120 or less, the cationicity of the amide ammonium salt increases, and the effect of adjusting the paper density by electrostatic adsorption to the pulp is improved.

[0037] The dosage form of the paper density regulator of the present invention is not particularly limited. For example, the amide ammonium salt can be used as a solid or liquid as it is, or it can be emulsified, dispersed or dissolved in water or an organic solvent and used.

[0038] The paper density regulator may contain other components as long as the effects of the present invention are not impaired. Other components are not particularly limited, and examples include solvents, pH adjusters, surfactants, defoamers, preservatives, and the like.

[0039] The solvent is not particularly limited, and examples include water, organic solvents, and the like. Examples of the organic solvent include lower alcohols, glycols, dimethylformamide, acetonitrile, and the like. When emulsifying, the solvent is preferably water or a mixed solvent of water and an organic solvent compatible therewith, and more preferably water.

[0040] The pH adjuster is not particularly limited, and examples include inorganic acids, organic acids, inorganic bases, organic bases, and the like. Examples of the inorganic acid include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and the like. Examples of the organic acid include formic acid, acetic acid, lactic acid, and the like. Examples of the inorganic base include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and the like. Examples of the organic base include ammonia, diethylamine, ethanolamine, diethanolamine, and the like.

[0041] The surfactant is not particularly limited, and examples thereof include nonionic surfactants, anionic surfactants, amphoteric surfactants, etc. Examples of nonionic surfactants include polyoxyalkylene alkyl ethers, polyoxyalkylene alkyl aryl ethers, polyoxyalkylene sorbitan fatty acid esters, polyoxyalkylene fatty acid esters, etc. Examples of anionic surfactants include alkyl sulfates, dialkyl sulfosuccinates, alkyl sulfate esters, polyoxyalkylene alkyl sulfate esters, etc. Examples of amphoteric surfactants include alkyl carbobetaines, alkyl amidoalkyl betaines, alkyl hydroxysulfobetaines, etc. When emulsifying, a nonionic surfactant is preferred as the surfactant.

[0042] In a preferred embodiment, the paper density regulator of the present invention has a pH of 3 to 8. When the pH is within this range, even if it contains a high concentration of amide ammonium salt, the paper density regulator prepared by emulsification can be in a low-viscosity liquid state at room temperature, and has excellent handleability compared to paste-like or gel-like ones. If the pH is less than 3, the paper may easily discolor or deteriorate. Also, since the prepared paper density regulator is likely to thicken and become paste-like or gel-like at room temperature, the handleability may also deteriorate. If the pH exceeds 8, the density reduction effect and sizing performance of the paper density regulator may not be fully exhibited.

[0043] In order to make the pH within the above range, it is preferable to use a base. The base is not particularly limited, and examples thereof include alkali metal carbonates such as sodium carbonate, and alkali metal hydroxides such as sodium hydroxide.

[0044] The content of the amidoammonium salt in the paper density regulator is preferably 10 to 40% by mass, more preferably 15 to 35% by mass. When the content is 10% by mass or more, the effect of adjusting the paper density and the sizing performance by the amidoammonium salt can be obtained without adding a large amount. When the content is 40% by mass or less, the paper density regulator prepared by emulsification can be made into a liquid with low viscosity at normal temperature, and it has excellent handleability compared with paste-like or gel-like ones.

[0045] A method for manufacturing paper using the paper density regulator of the present invention will be described. The raw materials of the paper and the papermaking method are not particularly limited. Examples of the raw material pulp include chemical pulp (bleached or unbleached kraft pulp of coniferous trees, bleached or unbleached kraft pulp of broad-leaved trees, etc.), mechanical pulp (groundwood pulp, thermomechanical pulp, chemithermomechanical pulp, etc.), deinked pulp, etc., which are used alone or mixed at an arbitrary ratio. Also, the pH of the paper may be acidic, neutral, or alkaline.

[0046] The paper is not particularly limited, but examples include printing papers such as uncoated printing paper, coated printing paper (art paper, coated paper, lightweight coated paper, etc.), lightly coated printing paper, special printing paper, etc.; information papers such as copy paper, inkjet paper, carbonless paper, photosensitive paper, thermal paper, etc.; newsprint; packaging papers such as unbleached wrapping paper, bleached wrapping paper, etc.; sanitary papers such as tissue paper, toilet paper, etc.; miscellaneous papers; corrugated papers such as cardboard, liner, core, etc.; wallpaper, base paper for fusuma paper and its backing paper, etc. Among these, it can be suitably used for printing papers and information papers that require sizing performance.

[0047] When manufacturing paper, the paper density regulator of the present invention is added to the raw material pulp. In particular, the internal addition method is preferably applied. The paper density regulator and, if necessary, other additives are added to a mixture containing pulp and water (for example, pulp slurry), and paper is obtained by performing papermaking by a normal method using the obtained mixture.

[0048] The manufacturing process of pulp and paper generally includes a pulp manufacturing process of treating wood and chips with mechanical force or chemical agents to obtain pulp, a waste paper deinking pulping process of dissociating, deinking, washing, and bleaching recycled waste paper to obtain deinked pulp, a washing and screening process of the obtained pulp, a bleaching process, a preparation process of adding various chemicals to prepare paper stock, a papermaking process, a pressing process of removing moisture from wet paper, and a drying process, etc. It may be at any location before the papermaking process. The chemical agent can be added as it is or after being diluted in advance into each chest or the pipe connecting them. For example, it can be added to facilities such as pipes, pumps, and storage tanks attached to each process in contact with the process water containing pulp. For example, in equipment such as pulpers, refiners, raw material chests, mixing chests, machine chests, seed boxes, and fan pumps, which are equipment for imparting properties according to the purpose to paper products in the papermaking process, the chemical agent can be added. The addition location of each chemical agent is not particularly limited as long as it is a location where the pulp slurry before the papermaking process is stirred. However, when added to a mixing chest, a machine chest, etc., it can be sufficiently mixed with the stirrer provided therein. Also, not only can it be added directly to the chest, but the chemical agent can also be added from the pipe inlet or outlet of the chest, etc.

[0049] The addition amount of the paper density regulator of the present invention to the pulp used in the manufacture of paper is not particularly limited, but based on 100 parts by mass of pulp, 0.3 to 1.0 parts by mass is preferable.

[0050] In the papermaking process, other chemicals can be added to such an extent that the performance of reducing the density is not impaired. Examples of other chemicals include, for example, dyes, pigments, fluorescent brightening agents; deinking agents such as polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers; polymers such as aluminum sulfate and polyacrylamide, and yield improvers such as starches; drainage improvers such as polyethyleneimine, polyacrylamide, and cationized starch; paper strength improvers such as dry paper strength enhancers and wet paper strength enhancers; adhesives such as polyacrylamide; sizing agents such as rosin soap, alkyl ketene dimer, alkenyl succinic anhydride, and polyvinyl alcohol; fillers such as talc, kaolin, calcium carbonate, titanium oxide, and barium sulfate; slime control agents such as chlorine, organic bromine compounds, and organic sulfur compounds; pitch control agents such as surfactants, chelating agents, and sulfuric acid bands; defoaming agents such as silicone-based agents; and coagulants that suppress the accumulation of salts with anions, etc. in the papermaking system.

[0051] Also, the purpose of density reduction is not particularly limited, and in addition to cost reduction and reduction of pulp usage, for example, it may be flexibility such as printability, volume feeling, texture, and touch.

[0052] The present invention has been described based on the embodiments above, but the present invention is not limited to these embodiments, and various modifications are possible without departing from the gist thereof.

[0053] Note that since the amide ammonium salt can have a plurality of structures depending on the molar ratio of the raw materials and is usually an unspecified mixture, it is difficult or requires an excessive burden to directly specify the features of the present invention by the structure or properties of the substance, and there is no other language that clearly and concisely specifies the features in terms of structure or properties. Therefore, the present invention is specified by the manufacturing method.

Examples

[0054] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. (1) Synthesis of compound (Synthesis of Compound A) Diethylenetriamine and stearic acid were charged into a reaction vessel, and the temperature was gradually increased while heating under a nitrogen atmosphere, followed by a dehydration reaction at 180 - 210 °C for 4 hours. After the reaction, it was cooled to 120 °C, water was added, and it was stirred for 1 hour to ring - open the cyclized product that had been imidazolinized. Then, dimethyl sulfate or diethyl sulfate was added dropwise while maintaining the temperature around 120 °C. After the addition was completed, the reaction was carried out for 1.5 hours to obtain compound A, an amide ammonium salt compound.

[0055] (Synthesis of Compounds B - P) The fatty acid, polyamine, and dialkyl sulfate shown in Table 1 were used in a predetermined molar ratio, and the same operations as in the synthesis of the above - mentioned compound A were carried out to obtain compounds B - P. Compounds B - O are amide ammonium salts, and compound P is an amide amine that does not react with dialkyl sulfate.

[0056] The total amine value of compounds A - P was measured using an automatic titrator set with N / 10 hydrochloric acid (alcoholic) after dissolving compounds A - P in 100 mL of anhydrous neutral ethanol. The results are shown in Table 1.

[0057] (2) Preparation of Paper Density Regulator 20 g of compound A was charged into a reaction vessel, heated to 80 °C and melted, water was added so that the total amount of amide compound A was 15% by mass, and Na2CO3 was added for pH adjustment to obtain an emulsified paper density regulator. Paper density regulators were also obtained for amide compounds B - P under the same conditions. Their pH values are shown in Table 2.

[0058] (3) Papermaking Hardwood sun - dried kraft pulp was stirred in a juice mixer for 1 minute to prepare a 0.75% pulp slurry (freeness 560 ml). While stirring this pulp slurry with a motor stirrer with adjustable rotation speed, a paper density regulator was added so that the amount of amide compound in the paper density regulator was 0.5% by mass relative to the pulp, and it was stirred for 1 minute. Next, papermaking was carried out using a square sheet machine [manufactured by Kumagai Riki Kogyo Co., Ltd.] to obtain a basis weight of 60 g / m 2 and then it was pressed at 14.7 kMPa for 3 minutes with a press and dried at 105 °C for 2 minutes using a drum - type dryer to obtain low - density paper.

[0059] (4) Evaluation of the bulkiness effect The thickness of the wetted hand-drying sheet was measured at 10 different locations using a JIS paper thickness measuring machine TM-600 (Kumagai Riki Kogyo Co., Ltd.), and the average value was obtained. The bulkiness effect was evaluated based on the density calculated from the basis weight and thickness of the hand-drying sheet. The bulkiness effect was evaluated according to the following criteria using the bulkiness ratio, which is the ratio of the density of the sample to the density of the blank. Density = basis weight of the hand-drying sheet (g / m 2 ) / thickness of the hand-drying sheet (μm) Bulkiness ratio = (density of the hand-drying sheet / density of the blank) × 100 Evaluation criteria ×: Bulkiness ratio is 100% or less, no bulkiness effect △: Bulkiness ratio is 101 - 103%, weak bulkiness effect 〇: Bulkiness ratio is 104 - 106%, bulkiness effect present ◎: Bulkiness ratio is 107% or more, good bulkiness effect

[0060] (5) Evaluation of sizing property The Stoke's sizing degree of the wetted hand-drying sheet was measured according to JIS P 8122:2007, and the value was rounded to the first decimal place. The sizing property was evaluated according to the following criteria. ×: Stoke's sizing degree is 0s, no sizing property △: Stoke's sizing degree is 1 - 3s, weak sizing property 〇: Stoke's sizing degree is 4 - 9s, sizing property present ◎: Stoke's sizing degree is 10s or more, good sizing property

[0061] The results of the evaluation are shown in Table 2.

[0062]

Table 1

[0063]

Table 2

[0064] From Tables 1 and 2, the low-density papers of Examples 1 to 11 in which papermaking was carried out using the paper density regulator of the present invention containing an amidoammonium salt in which dialkyl sulfate was reacted with an amidoamine obtained by reacting a polyamine with a fatty acid, with the number of carbon atoms of the fatty acid, the reaction molar ratio of the fatty acid to the active amino groups in the polyamine, and the reaction molar ratio of dialkyl sulfate to the active amino groups in the amidoamine being within a predetermined range, have a better bulk ratio and sizing performance compared to the low-density papers of Comparative Examples 1 to 5. That is, a paper density regulator capable of adjusting the paper density and having excellent sizing performance was obtained without using epichlorohydrin as a raw material. On the other hand, in Comparative Examples 1 and 2, the reaction molar ratio of dialkyl sulfate to the active amino groups in the amidoamine was high, in Comparative Example 3, the reaction molar ratio of the fatty acid to the active amino groups in the polyamine was low, in Comparative Example 4, the number of carbon atoms of the fatty acid was small, and in Comparative Example 5, the amidoamine was one that did not react with dialkyl sulfate, but all of these were inferior in sizing performance compared to Examples 1 to 11. Regarding the properties of the paper density regulator, all of the paper density regulators of Examples 1 to 11 with adjusted pH were liquid with low viscosity at room temperature, and had good handleability even when containing a high concentration of amidoammonium salt. A precipitate that did not dissolve in water was generated in the amidoamine of Comparative Example 5 at 10% by mass.

Claims

1. A paper density adjuster containing an ammonium amide salt obtained by reacting a dialkyl sulfate with an amidoamine obtained by reacting a polyamine with a fatty acid, wherein the fatty acid has 14 to 22 carbon atoms, the reaction molar ratio of the fatty acid is 0.3 to 0.8 with respect to the active amino groups in the polyamine, the reaction molar ratio of the dialkyl sulfate is 0.1 mole or more and less than 1 mole with respect to the active amino groups in the amidoamine, the ammonium amide salt is a tertiary or lower ammonium salt, and the paper density adjuster substantially does not contain epichlorohydrin and compounds having a chemical structure derived from epichlorohydrin.

2. The paper density adjuster according to claim 1, wherein the ammonium amide salt has a total amine value of 5 to 120.

3. The paper density adjuster according to claim 1 or 2, wherein the paper density adjuster has a pH of 3 to 8.

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