JP7705295B2 - Paper density regulator - Google Patents

Description

The present invention relates to a paper density regulator used in paper products.

The paper industry is an equipment-based industry, and all manufacturing is basically done through papermaking machines. One papermaking machine can usually only produce one type of paper, so when it is necessary to finely change the quality of the paper to meet customer requests, it is often difficult to do so through mechanical adjustments alone. For this reason, a method is used in which chemicals are added during the process to control qualities such as water repellency, coloring, flexibility, and strength.

In recent years, in light of a shortage of pulp resources, rising pulp prices, and the need to protect the global environment, paper density regulators have been added as chemicals to increase bulk (thickness) and reduce the amount of pulp used as a raw material in order to minimize the amount of pulp used. Cellulose (β-1,4-glucose), the main component of paper, is bonded by intermolecular hydrogen bonds, but by adsorbing paper density regulators to these parts and weakening the bonding strength between the molecules, spaces are created between the fibers, increasing bulk and lowering density.

As paper density regulators, which are chemicals added to reduce paper density and increase its volume, amidoamines and their salts obtained by reacting polyamines with fatty acids have been proposed (Patent Documents 1 to 4).

Patent Document 1 discloses a paper density regulator using amidoamine, Patent Document 2 discloses a quaternary ammonium salt obtained by quaternizing amidoamine using a bifunctional alkyl halide as an alkylating agent, and Patent Documents 3 and 4 disclose amidoamine and its acid salt, and a quaternary ammonium salt obtained by quaternizing amidoamine using an excess amount of a quaternizing agent such as methyl chloride as an alkylating agent relative to the active amino group.

Conventionally, paper density regulators have been used for printing paper and the like, but the use of paper density regulators can impair the effect of sizing agents, which control the water absorption of paper to prevent water-based ink bleeding and impart high writability and printability to paper, and so in addition to adjusting 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 acid to active amino groups in polyamine, the reaction molar ratio of alkylating agent to active amino groups in amidoamine, which is an amidation product of polyamine and fatty acid, and the type of alkylating agent are not sufficiently examined, and none of them have excellent sizing performance. In particular, there is a problem that quaternary amines significantly inhibit sizing performance and deteriorate printing quality.

There are various types of paper density regulators, such as non-ionic ester type and polymer blend type, but many of them use epichlorohydrin as a raw material, such as compounds obtained by reacting fatty acid polyamide amine with epihalohydrin, and compounds obtained by reacting aminoacrylamide of (meth)acrylic acid with epihalohydrin and alkyl halide, and trace amounts of epichlorohydrin are also contained in the formulation. This epichlorohydrin is discharged into rivers through the papermaking process, which leads to environmental pollution. Therefore, epichlorohydrin is designated as a monitoring item in Japan, and there is a possibility that wastewater standards will be established in the future. For this reason, there has been a demand for paper density regulators that do not use epichlorohydrin.

Patent Document 5 proposes a mixture of a first amino compound obtained by reacting a compound obtained by reacting a polyamine compound with a fatty acid with dialkyl sulfuric acid, and a second amino compound obtained by reacting epihalohydrin, or a third amino compound obtained by reacting epihalohydrin with dialkyl sulfuric acid, with the aim of obtaining low-density paper with little loss in strength.

JP 2005-068592 A Japanese Unexamined Patent Publication No. 47-008263 JP 2004-285521 A JP 2004-308095 A JP 2008-285774 A

However, because epichlorohydrin is used, there are concerns about the environmental impact of factory wastewater, etc. In addition, although the aim is to minimize the decrease in strength, sufficient consideration has not been given to sizing performance. In particular, the first amino compound is a quaternary product made using an excess of dialkyl sulfate, but as mentioned above, quaternary amine compounds significantly impair sizing performance, resulting in poor print 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, which makes it difficult to handle in actual use.

The present invention was made in consideration of the above circumstances, and aims to provide a paper density adjuster that can adjust paper density without using epichlorohydrin as a raw material and also has excellent sizing performance.

In order to solve the above-mentioned problems, the inventors conducted extensive research and discovered that by using an amidoamine obtained by reacting a polyamine with a fatty acid having a carbon number within a specific range, and a dialkyl sulfate as an alkylating agent, and by setting the reaction molar ratio of fatty acid to active amino groups ( _-NH2 , -NH-) in the polyamine and the reaction molar ratio of dialkyl sulfate to active amino groups in the amidoamine within specific ranges, and forming an amido ammonium salt which is a tertiary or lower ammonium salt, it is possible to adjust paper density and also to exhibit excellent sizing performance without using epichlorohydrin as a raw material, thereby completing the present invention.

That is, in order to solve the above-mentioned problems, the paper density regulator of the present invention is a paper density regulator containing an amido ammonium salt obtained by reacting an amido amine obtained by reacting a polyamine with a fatty acid with a dialkyl sulfuric acid,
The fatty acid has 14 to 22 carbon atoms,
the reacting molar ratio of the fatty acid is 0.3 to 0.8 relative to the active amino group in the polyamine;
a reacting molar ratio of the dialkyl sulfuric acid is 0.1 mol or more and less than 1 mol based on the active amino group in the amidoamine,
The amide ammonium salt is a tertiary or lower ammonium salt,
The paper density adjuster is characterized by being substantially free of epichlorohydrin and compounds having a chemical structure derived from epichlorohydrin.

The paper density adjuster of the present invention allows you to adjust paper density without using epichlorohydrin as a raw material, and also provides excellent sizing performance.

Specific embodiments of the present invention will be described below.
In this specification, the term "to" specifying a numerical range indicates greater than or equal to or less than the range.

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

In the paper density regulator of the present invention, the polyamine has, but is not particularly limited to, multiple amino groups. Each amino group may be primary, secondary, or tertiary, but is preferably primary or secondary. For example, the multiple amino groups are 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. Of these, it is preferable that the amino groups at both ends are primary amino groups.

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 multiple divalent hydrocarbon groups, they may be the same or different, and the number of carbon atoms is preferably 1 to 4, more preferably 2 or 3, and even more preferably 2. When there is 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 multiple monovalent hydrocarbon groups, they may be the same or different, and the number of carbon atoms is preferably 1 to 22, more preferably 1 to 10, and even more preferably 1 to 4. The polyamine may have a branched structure or a cyclic structure, but is preferably linear. The polyamine may be used alone or in combination of two or more types.

The polyamine is preferably a polyalkylene polyamine represented by the following formula (I). This polyalkylene polyamine has excellent paper density adjusting effect by the amide ammonium salt, and excellent handling properties of the paper density adjusting agent prepared by emulsification.

式中、Ｒは炭素数１～４のアルキレン基を示し、ｎは１～３の整数を示す。Ｒが２つ以上の場合、これらは同一でもよく異なる種類であってもよい。

In the formula, R represents an alkylene group having 1 to 4 carbon atoms, and n represents an integer of 1 to 3. When there are two or more R's, they may be the same or different.

Specific examples of the alkylene group R include a methylene group, an ethylene group, a trimethylene group, and a tetramethylene group. Preferably, R is an ethylene group. Specific examples of the polyalkylene polyamine represented by formula (I) include diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

In the paper density adjuster of the present invention, the fatty acid has a carbon number of 14 to 22. 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 amide ammonium salt has excellent paper density adjustment effect and sizing performance.

The fatty acid may be either linear or branched. It is preferably linear. The fatty acid may be either saturated or unsaturated. It is preferably a saturated fatty acid. The fatty acid may be used alone or in combination of two or more.

Specific examples of fatty acids include 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, and erucic acid. Other examples include mixed fatty acids derived from natural fats and oils and their hydrogenated products.

The paper density regulator of the present invention has a reactive molar ratio of fatty acid to active amino groups in the polyamine of 0.3 to 0.8. It is preferably 0.4 to 0.8, and more preferably 0.5 to 0.8. When the molar ratio is within this range, the paper density adjusting effect and sizing performance of the amide ammonium salt are excellent. In addition, the paper density regulator prepared by emulsification has excellent handleability.

The reaction between polyamine and fatty acid is carried out, for example, in a solvent such as water, using a catalyst as necessary, and amidation is performed by dehydration to produce amidoamine. The reaction temperature is not particularly limited, but considering the efficiency of the reaction, 180 to 210°C is preferable. In this reaction, some of the amidoamine may be cyclized by imidazolination of the amide and the amine adjacent to it, but it is preferable to open the ring by cooling, adding water, stirring for a predetermined time, or other means. The amidoamine used in the reaction with dialkyl sulfuric acid preferably has a ratio of tertiary amine value to total amine value of 0.8 or less, more preferably 0.5 or less, even more preferably 0.3 or less, and most preferably 0.1 or less.

In the paper density adjuster of the present invention, the dialkyl sulfate cationizes the amino group of the amidoamine with a tertiary or lower carbon number. 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 within this range, the amido ammonium salt has excellent paper density adjustment effect, sizing performance, and handling properties. The dialkyl sulfate may be used alone or in combination of two or more types.

The dialkyl sulfate is not particularly limited, but examples thereof include dimethyl sulfate, diethyl sulfate, dipropyl sulfate, diisopropyl sulfate, etc. Among these, dimethyl sulfate and diethyl sulfate are preferred.

In the paper density regulator of the present invention, the reaction molar ratio of dialkyl sulfuric acid is 0.1 mol or more and less than 1 mol relative to the active amino group in the amidoamine. It is preferably 0.1 to 0.8, and 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 amido ammonium salt are excellent. In addition, the paper density regulator prepared by emulsification has excellent handleability. When the reaction molar ratio of dialkyl sulfuric acid is 0.1 mol or more, the cationic nature of the amido ammonium salt increases, and the density reduction effect is improved by electrostatic adsorption to the pulp. When the reaction molar ratio of dialkyl sulfuric acid is less than 1 mol, moderate hydrophobicity is imparted without quaternization, and the sizing performance by the amido ammonium salt is excellent.

The reaction between amidoamine and dialkylsulfuric acid is carried out, for example, using a solvent such as water as necessary, and the amine is alkylated to form a tertiary or lower salt, thereby producing an amidoammonium salt. Dialkylsulfuric acid may be added dropwise to the amidoamine solution. There are no particular limitations on the reaction temperature, but a temperature of 110 to 130°C is preferable in consideration of reaction efficiency, etc.

In the paper density adjusting agent of the present invention, the amide ammonium salt is a tertiary or lower ammonium salt. Tertiary or lower ammonium salts impart moderate hydrophobicity, and the sizing performance of the amide ammonium salt is excellent. In addition, cationization promotes electrostatic adsorption to the pulp, improving the effect of adjusting the paper density.

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

The paper density regulator of the present invention does not substantially contain epichlorohydrin or a compound having a chemical structure derived from epichlorohydrin. The paper density regulator of this embodiment has an excellent paper density adjusting effect by amide ammonium salt and also has excellent sizing performance, even 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. This epichlorohydrin is discharged into rivers through the papermaking process, which leads to environmental pollution, so epichlorohydrin is designated as a monitoring item in Japan. However, the paper density regulator of this embodiment can provide a paper density regulator that meets future wastewater standards and can address environmental issues.

Here, "substantially free" refers to the following.
The content of epichlorohydrin in the paper density adjuster is 3 ppm or less, preferably 0.3 ppm or less, more preferably 0.03 ppm or less, and further preferably the paper density adjuster is free of epichlorohydrin.
The content of the compound having a chemical structure derived from epichlorohydrin 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 the compound is not contained. The compound having a chemical structure derived from epichlorohydrin is not particularly limited, but examples thereof include an amidoammonium salt obtained by reacting at least epichlorohydrin with an amidoamine obtained by reacting a polyamine with a fatty acid, and a compound obtained by reacting an aminoacrylamide of (meth)acrylic acid with epihalohydrin and an alkyl halide.

In a preferred embodiment, the paper density modifier of the present invention has a total amine value of the amide ammonium salt of 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.

When the total amine value of the amide ammonium salt is 1 or more, it is a tertiary or lower salt and is not quaternized. When the total amine value is 5 or more, it is given moderate hydrophobicity and the sizing performance of the amide ammonium salt is excellent. When the total amine value is 120 or less, the cationic nature of the amide ammonium salt increases, and the paper density adjustment effect is improved by electrostatic adsorption to the pulp.

The formulation of the paper density regulator of the present invention is not particularly limited; for example, the amide ammonium salt can be used as is in solid or liquid form, or it can be emulsified, dispersed or dissolved in water or an organic solvent.

The paper density adjuster may contain other components as long as the effects of the present invention are not impaired. Examples of other components include, but are not limited to, solvents, pH adjusters, surfactants, defoamers, preservatives, etc.

The solvent is not particularly limited, but examples thereof include water and organic solvents. Examples of organic solvents include lower alcohols, glycols, dimethylformamide, acetonitrile, etc. When emulsifying, the solvent is preferably water or a mixed solvent of water and an organic solvent compatible with water, and more preferably water.

Examples of pH adjusters include, but are not limited to, inorganic acids, organic acids, inorganic bases, and organic bases. Examples of inorganic acids include hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid. Examples of organic acids include formic acid, acetic acid, and lactic acid. Examples of inorganic bases include sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate. Examples of organic bases include ammonia, diethylamine, ethanolamine, and diethanolamine.

The surfactant is not particularly limited, but examples thereof include nonionic surfactants, anionic surfactants, and amphoteric surfactants. Examples of nonionic surfactants include polyoxyalkylene alkyl ethers, polyoxyalkylene alkylaryl ethers, polyoxyalkylene sorbitan fatty acid esters, and polyoxyalkylene fatty acid esters. Examples of anionic surfactants include alkyl sulfates, dialkyl sulfosuccinates, alkyl sulfate ester salts, and polyoxyalkylene alkyl sulfate ester salts. Examples of amphoteric surfactants include alkyl carbobetaines, alkyl amido alkyl betaines, and alkyl hydroxy sulfobetaines. When emulsifying, the surfactant is preferably a nonionic surfactant.

In a preferred embodiment, the paper density regulator of the present invention has a pH of 3 to 8. When the pH is in this range, even if the amide ammonium salt is contained at a high concentration, the paper density regulator prepared by emulsification can be made into a low-viscosity liquid at room temperature, and is easier to handle than a paste or gel. If the pH is less than 3, the paper may be more susceptible to discoloration or deterioration. In addition, the prepared paper density regulator may tend to thicken at room temperature and become a paste or gel, which may result in poor handling. If the pH exceeds 8, the density reducing effect and sizing performance of the paper density regulator may not be fully exhibited.

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

The content of the amide ammonium salt in the paper density adjuster is preferably 10 to 40% by mass, more preferably 15 to 35% by mass. If the content is 10% by mass or more, the paper density adjustment effect and sizing performance due to the amide ammonium salt can be obtained without adding a large amount. If the content is 40% by mass or less, the paper density adjuster prepared by emulsification can be made into a low-viscosity liquid at room temperature, and is easier to handle than paste-like or gel-like ones.

A method for producing paper using the paper density regulator of the present invention will now be described.
The raw materials and papermaking methods of the paper are not particularly limited. Examples of raw pulp include chemical pulp (bleached or unbleached softwood kraft pulp, bleached or unbleached hardwood kraft pulp, etc.), mechanical pulp (groundwood pulp, thermomechanical pulp, chemithermomechanical pulp, etc.), and deinked pulp, either alone or in any mixture in any ratio. The pH of the paper may be acidic, neutral, or alkaline.

The papers include, but are not limited to, printing paper such as uncoated printing paper, coated printing paper (art paper, coated paper, lightly coated paper, etc.), lightly coated printing paper, special printing paper, etc.; information paper such as copy paper, inkjet paper, carbonless paper, photosensitive paper, thermal paper, etc.; newsprint; wrapping paper such as unbleached wrapping paper and bleached wrapping paper; sanitary paper such as tissue paper and toilet paper; miscellaneous paper; cardboard paper such as cardboard, liner, and core; wallpaper, sliding door paper base paper and its backing paper, etc.
Among these, it can be suitably used for printing paper and information paper, which require sizing performance.

When producing paper, the paper density regulator of the present invention is added to the raw pulp. In particular, the internal addition method is preferably applied, in which the paper density regulator and, if necessary, other additives are added to a mixture containing pulp and water (e.g., pulp slurry), and the resulting mixture is used to make paper by a conventional method to obtain paper.

Pulp and paper manufacturing processes generally include the pulp manufacturing process, in which wood and chips are treated with mechanical force and chemicals to obtain pulp, the waste paper deinking pulp process, in which recovered waste paper is disintegrated, deinked, washed, and bleached to obtain deinked pulp, the washing and refining process of the obtained pulp, the bleaching process, the preparation process, in which various chemicals are added to prepare paper stock, the papermaking process, the pressing process, in which water from the wet paper is removed, and the drying process. However, the chemicals can be added at any point before the papermaking process, either directly or after being diluted, to each chest or the piping connecting them. For example, they can be added to equipment such as piping, pumps, and storage tanks associated with each process that comes into contact with process water containing pulp. For example, chemicals can be added to pulpers, refiners, raw material chests, mixing chests, machine chests, seed boxes, fan pumps, etc., which are equipment used in the papermaking process to give paper products properties according to their purpose. The location where each chemical is added is not particularly limited as long as it is a location where the pulp slurry is stirred before the papermaking process, but if the chemicals are added to a mixing chest, machine chest, etc., they can be mixed thoroughly by the agitator installed in the chest. In addition to adding the chemicals directly to the chest, they may also be added through the piping inlet or outlet of the chest.

The amount of the paper density regulator of the present invention added to the pulp used in paper production is not particularly limited, but is preferably 0.3 to 1.0 parts by mass based on 100 parts by mass of pulp.

In the papermaking process, other chemicals can be added to the extent that the low density performance is not impaired.
Examples of other chemicals include dyes, pigments, and fluorescent whitening agents; deinking agents such as polyoxyethylene alkyl ethers and polyoxyethylene alkylphenyl ethers; retention aids such as aluminum sulfate, polymers such as polyacrylamide, and starches; drainage improvers such as polyethyleneimine, polyacrylamide, and cationized starch; paper strength agents such as dry strength agents and wet strength agents; thickeners such as polyacrylamide; sizing agents such as rosin soap, alkyl ketene dimers, alkenyl succinic anhydrides, 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 aluminum sulfate; silicone-based defoamers; and coagulants that suppress the accumulation of anionic salts in the papermaking system.

The purpose of reducing density is not particularly limited, and may be to reduce costs and the amount of pulp used, as well as to improve printability, volume, texture, and flexibility, etc.

The present invention has been described above based on an embodiment, but the present invention is not limited to this embodiment, and various modifications are possible without departing from the spirit of the invention.

In addition, since amide ammonium salts can have multiple structures depending on the molar ratio of the raw materials and are usually unspecified mixtures, it is difficult or too burdensome to directly specify the characteristics of the present invention based on the structure or properties of the product, and there are no other terms that clearly and concisely specify the characteristics in terms of the structure or properties. Therefore, the present invention was specified by the manufacturing method.

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 mixture was gradually heated under a nitrogen atmosphere to carry out a dehydration reaction for 4 hours at 180 to 210° C. After the reaction was completed, the mixture was cooled to 120° C., water was added, and the mixture was stirred for 1 hour to open the imidazoline cyclized product, and dimethyl sulfate or diethyl sulfate was added dropwise while maintaining the temperature at around 120° C. After the completion of the dropwise addition, the mixture was reacted for 1.5 hours to obtain compound A, which is an amide ammonium salt.

(Synthesis of Compounds B to P)
The fatty acids, polyamines, and dialkyl sulfates shown in Table 1 were used in the prescribed molar ratios, and the same operations as in the synthesis of compound A were carried out to obtain compounds B to P. Compounds B to O are amide ammonium salts, and compound P is an amide amine that does not react with dialkyl sulfate.

The total amine value of compounds A to P was measured by dissolving compounds A to P in 100 mL of anhydrous neutral ethanol and then using an automatic titrator equipped with N/10 hydrochloric acid (alcoholic). The results are shown in Table 1.

(2) Preparation of paper density regulator 20 g of compound A was charged into a reaction vessel, and melted by heating to 80°C. Water was added so that the total amount of amide compound A was ₁₅ mass%, and _Na2CO3 was added to adjust the pH, obtaining an emulsified paper density regulator. Paper density regulators for amide compounds B to P were obtained under similar conditions. Their pHs are shown in Table 2.

(3) Papermaking The bleached hardwood kraft pulp was stirred for 1 minute in a juice mixer to prepare a 0.75% pulp slurry (freeness 560 ml). While stirring this pulp slurry with a motor stirrer with adjustable 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 the mixture was stirred for 1 minute. Next, the paper was made into a paper with a basis weight of 60 g/ ^m2 using a square sheet machine [manufactured by Kumagai Riki Kogyo Co., Ltd.], pressed for 3 minutes at 14.7 kMPa, and then dried for 2 minutes at 105°C in a drum dryer to obtain a low-density paper.

(4) Evaluation of bulkiness The thickness of the conditioned hand-made sheet was measured at 10 different locations using a JIS paper thickness measuring instrument TM-600 (Kumagaya Riki Kogyo Co., Ltd.) and the average value was calculated. The bulkiness effect was evaluated based on the density calculated from the basis weight and thickness of the hand-made sheet. The bulkiness effect was evaluated based on the bulkiness ratio, which is the ratio of density to the blank, according to the following criteria.
Density = hand-made sheet basis weight (g/ ^m2 ) / hand-made sheet thickness (μm)
Bulkiness ratio=(density of handmade sheet/density of blank)×100
Evaluation criteria: ×: Bulking rate is 100% or less, no bulking effect; △: Bulking rate is 101-103%, the bulking effect is weak; ◯: Bulking rate is 104-106%, the bulking effect is good; ◎: Bulking rate is 107% or more, the bulking effect is good

(5) Evaluation of sizing property The Stockigt sizing degree of the conditioned handmade sheet was measured in accordance with JIS P 8122:2007, rounded off to the first decimal place, and evaluated according to the following criteria.
×: Stockigt sizing degree is 0s, no sizing ability △: Stockigt sizing degree is 1-3s, weak sizing ability 〇: Stockigt sizing degree is 4-9s, good sizing ability ◎: Stockigt sizing degree is 10s or more, good sizing ability

The evaluation results are shown in Table 2.

From Tables 1 and 2, the low-density papers of Examples 1 to 11, which were made using the paper density regulator of the present invention containing an amidoammonium salt in which the number of carbon atoms of the fatty acid, the reaction molar ratio of the fatty acid to the active amino group in the polyamine, and the reaction molar ratio of the dialkyl sulfuric acid to the active amino group in the amidoamine are within a predetermined range, have better bulkiness and sizing performance than the low-density papers of Comparative Examples 1 to 5. That is, a paper density regulator was obtained that can adjust the paper density without using epichlorohydrin as a raw material and has excellent sizing performance. In contrast, Comparative Examples 1 and 2 have a high reaction molar ratio of the dialkyl sulfuric acid to the active amino group in the amidoamine, Comparative Example 3 has a low reaction molar ratio of the fatty acid to the active amino group in the polyamine, Comparative Example 4 has a small number of carbon atoms of the fatty acid, and Comparative Example 5 is an amidoamine that is not reacted with dialkyl sulfuric acid, but all of these have inferior sizing performance compared to Examples 1 to 11.
Regarding the properties of the paper density regulator, the pH-adjusted paper density regulators of Examples 1 to 11 were all in the form of a low-viscosity liquid at room temperature, and had good handleability even when containing a high concentration of amide ammonium salt. The amide amine of Comparative Example 5 produced a precipitate that was insoluble in water at 10% by mass.

Claims (3)

A paper density regulator comprising an amido ammonium salt obtained by reacting a dialkyl sulfuric acid with an amido amine obtained by reacting a polyamine with a fatty acid,
The fatty acid has 14 to 22 carbon atoms,
the reacting molar ratio of the fatty acid is 0.3 to 0.8 relative to the active amino group in the polyamine;
a reacting molar ratio of the dialkyl sulfuric acid is 0.1 mol or more and less than 1 mol based on the active amino group in the amidoamine,
The amide ammonium salt is a tertiary or lower ammonium salt,
The paper density adjuster is substantially free of epichlorohydrin and compounds having a chemical structure derived from epichlorohydrin. The paper density adjuster according to claim 1, wherein the amide ammonium salt has a total amine value of 5 to 120. The paper density adjuster according to claim 1 or 2, wherein the pH of the paper density adjuster is 3 to 8.