JP2007107116A - Softening agent for paper and method for producing paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a softening agent for paper which is capable of giving a paper having excellent softness and sufficient sizing property. <P>SOLUTION: The softening agent for paper contains an acid salt of a specific condensation product of an amide amine compound and urea, and a specific tertiary amine compound. The mass ratio of the acid salt of the condensation product to the tertiary amine compound is 95/5 to 60/40. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a paper softener and a method for producing a soft paper using the same. More particularly, the present invention relates to a paper softener capable of improving flexibility and size.

  With the progress of visualization and colorization of printed materials, there is a demand for printing paper with good flexibility in terms of printability. In addition, more flexible printing paper has been demanded from the viewpoint of easy turning of pages of printed materials such as books.

  Until now, as a method for imparting flexibility to paper, it is known to use a softening agent in the field of sanitary paper, where flexibility is strongly demanded. Examples of such softeners include softeners containing lanolin and lanolin derivatives (for example, Patent Document 1), softeners containing dilong chain alkyl type quaternary ammonium salts (for example, Patent Document 2), Examples thereof include a softening agent containing pyrrolidone carboxylate and / or betaine (for example, Patent Document 3). However, in the papermaking industry, it is known that when softness is imparted to paper, the size is reduced. Paper using these softeners is improved to some extent, but the size is reduced. There is a problem of doing.

On the other hand, as softeners for printing paper, aminoammonium salts (for example, Patent Document 4), ester compounds of polyhydric alcohols and higher unsaturated fatty acids (for example, Patent Document 5), and the like have been studied. However, all of these are not sufficient, although the flexibility is improved to some extent, and there is a problem that the size is lowered.
JP-A-53-147803 JP 63-165597 A JP-A-7-189170 JP 2001-355197 A JP 2002-155494 A

  An object of the present invention is to provide a softener for paper capable of obtaining paper having excellent flexibility and sufficient size. Another object of the present invention is to provide a method for efficiently producing paper using the paper softener.

  As a result of diligent research to solve the above-mentioned problems, the present inventors can achieve the above object by combining a specific amidoamine and urea condensate acid salt and a specific tertiary amine compound in a specific ratio. It has been found that a paper softener can be obtained. The inventors have found a paper manufacturing method using the paper softener and have completed the present invention.

The paper softener of the present invention comprises an acid salt (A) of a condensate of an amidoamine compound and urea and a tertiary amine compound (B). The amidoamine compound has the following formula (1):
R ¹ NH— (R ² —NH) _n —R ³ (1)
(R ¹ and R ³ are a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R ² is an alkylene group having 1 to 4 carbon atoms, and n is 2 to 4) The polyamine compound (1) and a carboxylic acid having 10 to 24 carbon atoms and containing 35% by mass or more of a saturated carboxylic acid are mixed with the carboxyl of the carboxylic acid with respect to 1 mol of the amino group of the polyamine compound (1). The group is obtained by reacting at a ratio of 0.4 to 0.8 mol, the condensation rate of the condensate is 10 to 50%, and the tertiary amine compound (B) is represented by the following formula: (2):

(R ⁴ is an alkyl or alkenyl group having 8 to 20 carbon atoms, M ¹ and M ² are each a hydrogen atom or an alkali metal, and x and y are each 1 to 3), And mass ratio A / B of the acid salt (A) of this condensate and this tertiary amine compound (B) is 95 / 5-60 / 40.

  The paper manufacturing method of the present invention includes a step of adding the paper softening agent to 0.03 to 8 parts by mass with respect to 100 parts by mass of pulp.

  The paper softener of the present invention can impart excellent flexibility without reducing the size of the paper.

  The paper softener of the present invention includes an acid salt (A) of a condensate of an amidoamine compound and urea (hereinafter sometimes referred to as component A) and a tertiary amine compound (B) (hereinafter sometimes referred to as component B). ). Hereinafter, each component, a paper softening agent, and a method for producing paper using the same will be sequentially described.

(I) Acid salt of condensate of amidoamine compound and urea (A)
The acid salt (A) of the condensate used in the paper softener of the present invention is an acid salt of a condensate obtained by reacting an amidoamine compound and urea. Hereinafter, a method for preparing an amidoamine compound, urea, a condensate using them, and a method for preparing an acid salt of the condensate will be described.

(A-1) Amidoamine Compound The polyamine compound used for the production of the above amidoamine compound is represented by the following general formula (1):
R ¹ NH— (R ² —NH) _n —R ³ (1)
(R ¹ and R ³ are a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R ² is an alkylene group having 1 to 4 carbon atoms, and n is 2 to 4).

In the general formula (1), examples of the alkyl group having 1 to 3 carbon atoms in R ¹ and R ³ include a methyl group, an ethyl group, a propyl group, and an isopropyl group. When the number of carbon atoms exceeds 3, the paper softener using this has the effect of imparting flexibility and size properties to the paper, but the resulting amidoamine compound has a high melting point and may be inferior in handleability. .

In the general formula (1), the alkylene group having 1 to 4 carbon atoms R ² can take, for example, methylene group, ethylene group, trimethylene group, tetramethylene group, and butylene group.

  In the said General formula (1), n is 2-4. When n exceeds 4, the paper softener using this has the effect of imparting flexibility and sizing properties to the paper, but the melting point of the resulting amidoamine compound is high and the handleability may be poor.

    The carboxylic acid used in the production of the amidoamine compound is a carboxylic acid having 10 to 24 carbon atoms, preferably 12 to 18 carbon atoms, and contains 35% by mass or more, preferably 60% by mass or more of a saturated carboxylic acid. When the number of carbon atoms is less than 10, the resulting paper has insufficient flexibility and size. When the number of carbon atoms exceeds 24, the paper softener using this has the effect of imparting flexibility and size properties to the paper, but the resulting amidoamine compound has a high melting point and may be inferior in handleability. . Moreover, when content of saturated carboxylic acid is less than 35 weight%, the size property of the paper obtained becomes inadequate.

  Specific examples of the carboxylic acid having 10 to 24 carbon atoms include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, tetracosanoic acid and other saturated carboxylic acids and palmitoleic acid, olein Examples thereof include unsaturated carboxylic acids such as acid, linoleic acid, linolenic acid, and erucic acid. As described above, these carboxylic acids are used so as to contain 35% by mass or more of a saturated carboxylic acid.

  In the amidoamine compound, the polyamine compound (1) and the carboxylic acid are mixed in an amount of 0.4 to 0.8 mol, preferably 0. It is obtained by reacting at a ratio of 45 to 0.7 mol. When the carboxyl group ratio is less than 0.4 mol, the resulting paper has insufficient flexibility and size. When it exceeds 0.8 mol, sufficient flexibility cannot be given to the paper. The reaction is carried out, for example, by charging the polyamine compound (1) and the carboxylic acid in a reactor, heating the mixture with stirring in a nitrogen gas atmosphere, and heating for several hours while removing the generated water. .

(A-2) Urea Commercially available products can be used as appropriate for urea, which is a raw material for the condensate used in the paper softener of the present invention.

(A-3) Preparation of condensate The condensate used in the paper softener of the present invention is a condensation reaction product obtained by reacting the above amidoamine compound with urea. This condensate is prepared by a normal condensation reaction.

  The urea condensation rate of the condensate is 10 to 50%, preferably 15 to 40%. This urea condensation rate is represented by the following formula (I). If the urea condensation rate is less than 10%, the size of the paper obtained is insufficient. When the urea condensation rate exceeds 50%, the flexibility of the resulting paper, particularly the bending stiffness, becomes insufficient.

(A-4) Preparation of acid salt of condensate The acid salt (A) of the urea condensate used in the present invention is obtained by reacting the above condensate with an acid (such as an organic acid or an inorganic acid). .

  Examples of the inorganic acid include hydrochloric acid, sulfuric acid, carbonic acid, nitric acid, phosphoric acid and the like. Organic acids include formic acid, acetic acid, propionic acid, octylic acid, butyric acid, oxalic acid, malonic acid, itaconic acid, adipic acid, succinic acid, sebacic acid, citric acid, hydroxybenzoic acid, malic acid, hydroxymalonic acid, lactic acid , Gluconic acid, salicylic acid, hydroxyvaleric acid, aspartic acid, glutamic acid, taurine, sulfamic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid and the like. Of these, organic acids are preferred, and formic acid, acetic acid, and propionic acid are particularly preferred.

(II) Tertiary amine compound (B)
The tertiary amine compound (B) used in the paper softener of the present invention is represented by the following general formula (2) (hereinafter sometimes referred to as tertiary amine compound (2)):

(R ⁴ is an alkyl group or alkenyl group having 8 to 20 carbon atoms, M ¹ and M ² are each a hydrogen atom or an alkali metal, and x and y are each 1 to 3).

In the general formula (2), R ⁴ is an alkyl group or an alkenyl group having 8 to 20 carbon atoms, preferably 10 to 14 carbon atoms, as described above. When the number of carbon atoms is less than 8, sufficient size cannot be imparted to the paper. When the number of carbon atoms exceeds 20, such a compound is difficult to obtain industrially, although it has the effect of imparting flexibility and size properties to the paper.

  Examples of the alkyl group having 8 to 20 carbon atoms include octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, isooctadecyl group, nonadecyl group And eicosyl group. Examples of the alkenyl group having 8 to 20 carbon atoms include a tetradecenyl group, a hexadecenyl group, an octadecenyl group, an isooctadecenyl group, and an eicocenyl group.

In the general formula (2), M ¹ and M ² may be the same or different. Examples of the alkali metal include potassium and sodium.

  In the general formula (2), x and y are preferably both x and y. When x and y are 0 or exceeds 3, the resulting paper has insufficient flexibility.

  The said tertiary amine compound (2) may be used independently and may be used in combination of 2 or more type.

(III) Paper Softener The paper softener of the present invention comprises the acid salt (component A) of the condensate and the tertiary amine compound (component B).

  The mass ratio (A / B) of the A component and the B component in the paper softener of the present invention is 95/5 to 60/40, preferably 92/8 to 75/25. When the ratio of the acid salt (component A) of the condensate is less than 60 parts by mass, the flexibility and size properties of the paper obtained using this softening agent are insufficient. When the ratio of the acid salt (component A) of the condensate exceeds 95 parts by mass, the flexibility of the resulting paper, particularly the bending stiffness, becomes insufficient.

  The paper softener of the present invention may be used as it is, but may also be used as a dispersion. The dispersion is prepared by, for example, charging water or a water-soluble organic solvent, charging the acid salt of the condensate and a tertiary amine compound, and stirring the mixture. As the water-soluble organic solvent, 1 to 3 water-soluble alcohols are preferable, and propylene glycol is more preferable.

(IV) Paper Manufacturing Method The paper manufacturing method of the present invention is characterized in that the paper softener is used in a normal paper manufacturing process. The amount of the paper softening agent is 0.03 to 8 parts by mass, preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the pulp. When the amount of the paper softener is less than 0.03 parts by mass, sufficient flexibility cannot be imparted to the paper. When the amount of the paper softener exceeds 8 parts by mass, the flexibility and size improvement effect corresponding to the amount of use cannot be obtained, but rather the cost of the paper is increased, which is economically disadvantageous.

  The above pulp includes chemical pulp (such as bleached or unbleached kraft pulp of conifer or hardwood), mechanical pulp (such as ground pulp, thermomechanical pulp, chemithermomechanical pulp), deinked pulp (such as newspaper and magazine wastepaper), etc. A single substance or a mixture of them at an arbitrary ratio can be selected. In particular, mechanical pulp or deinked pulp is suitable.

  The paper softener of the present invention can be used in various processes in the production of paper. That is, it can be added to the papermaking system at any stage of the papermaking process (internal addition method), and can also be applied to the surface of the pulp sheet obtained by the papermaking process (external addition method). For example, the internal addition method that is added to the pulp slurry in the mixing chest, machine chest, seed box, etc. in the paper making process, or the size press, gate roll, spray, etc. that are applied to the pulp sheet surface obtained by paper making The addition method is adopted.

  In particular, the internal addition method is preferably employed. For example, paper can be obtained by adding the paper additive to a mixture containing pulp and water (for example, pulp slurry) by an arbitrary method and making paper by a normal method using the obtained mixture.

  In the production method of the present invention, it is possible to use any paper machine such as a long net paper machine, a twin wire machine, and a Yankee machine that are generally used for paper making.

  Examples of the paper manufactured by the paper manufacturing method of the present invention include newsprint paper, printing paper, recording paper, packaging paper, paperboard, liner, corrugated paper such as a core, wallpaper, base paper, backing paper, and the like. Sanitary paper such as paper products, toilet paper, and tissue paper. Printing paper is particularly suitable.

  The present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to these examples.

(Synthesis Example 1.1: Synthesis of condensate)
In a 500 ml four-necked flask equipped with a stirrer, a condenser, a thermometer, and a nitrogen inlet tube, 284.0 g (1 mol) of stearic acid and the formula (1) shown in the 1.1 column of Table 1 are used. Polyamine compound 51.5 g (0.5 mol) was charged and stirred at 180 to 190 ° C. in a nitrogen atmosphere. The reaction was carried out for 3 hours while removing generated water out of the system to obtain an amidoamine compound having an amine value of 86.8. The amidoamine compound was allowed to cool to 100 ° C. and then charged with 6.6 g (0.11 mol) of urea, stirred at 160 to 170 ° C. in a nitrogen atmosphere, and reacted for 1 hour while removing ammonia out of the system. It was. A condensate a-1 having an amine value of 53.5 and a urea condensation rate of 38.4% was obtained.

(Synthesis Examples 1.2 to 1.7: Synthesis of condensate)
The condensate a- was prepared in the same manner as in Synthesis Example 1.1 except that the carboxylic acid described in Table 1, the polyamine compound represented by the formula (1), and urea were used in the molar ratios described in Table 1. 2 to a-7 were obtained.

(Comparative Synthesis Examples 1.1 to 1.6: Synthesis of Condensate)
The condensate a- was prepared in the same manner as in Synthesis Example 1.1 except that the carboxylic acid described in Table 1, the polyamine compound represented by the formula (1), and urea were used in the molar ratios described in Table 1. 8 to a-13 were obtained.

  Condensates a-1 to a-13 shown in Table 1 were obtained according to Synthesis Examples 1.1 to 1.7 and Comparative Synthesis Examples 1.1 to 1.6. Among these, the condensates a-8 to a-13 of Comparative Synthesis Examples 1.1 to 1.6 do not satisfy the conditions of the condensate of the present invention in the following points. That is, the condensate a-8 has a small carboxylic acid carbon number (caprylic acid). In the condensate a-9, an unsaturated carboxylic acid (oleic acid) is used as the carboxylic acid. Condensates a-10 and a-11 have a high urea condensation rate. And condensate a-12 and a-13 have a high ratio of the carboxyl group with respect to the amino group in an amidoamine compound.

(Synthesis Example 2.1: Synthesis of tertiary amine compound)
A 500 ml four-necked flask equipped with a stirrer, a condenser, and a thermometer was charged with 87.2 g of ion-exchanged water, 87.2 g of ethanol, and 54.6 g (0.30 mol) of laurylamine. While stirring at ℃, 93 g (0.64 mol) of 65% aqueous monochloroacetic acid solution and 106.8 g (1.28 mol) of 48% aqueous sodium hydroxide solution were added dropwise over 2 hours. The reaction was carried out with stirring for 5 hours to obtain an aqueous solution containing 30% of the tertiary amine compound b-1. Table 2 shows the composition of this tertiary amine compound b-1.

(Synthesis Examples 2.2 and 2.3: Synthesis of tertiary amine compound)
The tertiary amine compound b-2 and the synthetic amine 2.1 were prepared in the same manner as in Synthesis Example 2.1 except that myristylamine (Synthesis Example 2.2) or stearylamine (Synthesis Example 2.3) was used instead of laurylamine. b-3 was obtained. Table 2 shows the compositions of these tertiary amine compounds b-2 and b-3.

(Comparative Synthesis Example 2.1: Synthesis of tertiary amine compound)
A tertiary amine compound b-4 was obtained in the same manner as in Synthesis Example 2.1 except that octylamine was used instead of laurylamine. Table 2 shows the composition of the tertiary amine compound b-4.

(Example 1: Preparation of paper softener dispersion and evaluation thereof)
1. Preparation of a paper softener dispersion In a 500 ml four-necked flask equipped with a stirrer, a condenser and a thermometer, 30 g of propylene glycol, 206.6 g of ion-exchanged water, and obtained in Synthesis Example 2.1 22.7 g (containing 6.8 g of b-1) of an aqueous solution containing 30% of the tertiary amine compound b-1 thus obtained was charged. While stirring at 75 to 80 ° C., 2.4 g of acetic acid and 38.3 g of urea condensate A-1 were added thereto, followed by stirring for 1 hour. Then, it cooled and obtained the dispersion liquid X-1 of the softener for paper.

2. Evaluation of Softener for Paper Using the dispersion X-1 obtained above, a handsheet is produced as follows, and the flexibility (bending stiffness and capacity) and size of the obtained handsheet are evaluated. did. These evaluation results are summarized in Table 3.

(1) Manufacture of handsheets LBKP (hardwood bleached pulp) was disaggregated using a disaggregator (manufactured by Kumagaya Riken Co., Ltd.) to prepare a pulp slurry containing 1% by mass of pulp. 800 g of this pulp slurry (pulp amount 8 g) was put in a 1 liter beaker, 0.25 g of dispersion X-1 (0.5 parts by mass of paper softener relative to 100 parts by mass of pulp), aluminum sulfate 0.8 g of an aqueous solution containing 1% by mass (0.1 part by mass with respect to 100 parts by mass of pulp), and cationized starch previously diluted to 1% and gelatinized (Ace K-100, manufactured by Oji Cornstarch Co., Ltd.) 8.0 g (1.0 part by mass of cationized starch with respect to 100 parts by mass of pulp) was added, and the mixture was stirred at 250 rpm for 1 minute by a turbine blade having a diameter of 4.5 cm. Thereafter, 100 g of the obtained mixture is weighed, paper-made with a TAPPI standard sheet machine (manufactured by Yasuda Seiki Co., Ltd.), pressed using a hydraulic press machine (manufactured by Yasuda Seiki Co., Ltd.) at 0.35 MPa for 5 minutes, A hand dryer sheet having a basis weight of about 50 g / m ² was obtained by drying at 105 ° C. for 2 minutes with a type dryer (manufactured by Yasuda Seiki Co., Ltd.) The handsheet was conditioned for 17 hours in a constant temperature and humidity chamber (temperature 23 ° C., humidity 50%).

(2) Flexibility evaluation 1 (bending stiffness)
Using a pure bending tester (KES-FB2 manufactured by Kato Tech Co., Ltd.), the bending stiffness in the vertical direction and the horizontal direction of the moisture-controlled handsheet was measured, and the average value was obtained. The average value obtained was evaluated according to the following criteria.

(Evaluation criteria)
Flexural rigidity is less than 4.41 × 10 ⁻⁵ N · m ² / m: Good flexibility (◯)
Flexural rigidity is 4.41 × 10 ⁻⁵ N · m ² / m or more: Insufficient flexibility (×)

(3) Flexibility evaluation 2 (capacity)
The basis weight of the conditioned handsheet was measured according to JIS P 8124. Further, the thickness was measured with a JIS paper pressure measuring device (MEI-10 manufactured by Citizen Watch Co., Ltd.). The capacity of the handsheet obtained according to the following formula was determined and evaluated according to the following criteria.
Sheet capacity (cm ³ / g) = thickness (μm) / basis weight (g / m ² )

(Evaluation criteria)
Sheet capacity is 1.60 cm ³ / g or more: Good flexibility (◯)
Sheet capacity is less than 1.60 cm ³ / g: insufficient flexibility (×)

(4) Evaluation of sizing property In accordance with JIS P 8122, the steech human sizing degree of the moisture-controlled handsheet was measured, and the sizing property was evaluated according to the following criteria.

(Evaluation criteria)
Sizing degree is 20 seconds or more: Good sizing (○)
Sizing degree is less than 20 seconds: Insufficient sizing (×)

(Examples 2 to 7)
Dispersions X-2 to X of the paper softener were the same as in Example 1, except that the condensate, acid, and tertiary amine compound shown in Table 3 were used in the mass ratio shown in Table 3. -7 was obtained. Using these dispersions, handsheets were produced in the same manner as in Example 1, and the flexibility (bending stiffness and capacity) and size of the obtained handsheets were evaluated. These evaluation results are summarized in Table 3.

(Comparative Examples 1-15)
Dispersions X-8 to X of the paper softener were the same as in Example 1 except that the condensate, acid, and tertiary amine compound shown in Table 4 were used in the mass ratio shown in Table 4. -22 was obtained. Using these dispersions, handsheets were produced in the same manner as in Example 1, and the flexibility (bending stiffness and capacity) and size of the obtained handsheets were evaluated. These evaluation results are summarized in Table 4.

  From the results in Table 3, it can be seen that when a paper softener having a specific composition is used as in Examples 1 to 7, a paper (handsheet) having excellent flexibility and size can be obtained. .

  On the other hand, for Comparative Examples 1 to 15 in Table 4, either the acid salt of the condensate or the tertiary amine compound constituting the softener for paper used does not satisfy the conditions of the present application, or both The ratio does not satisfy the scope of the present application. For this reason, either the flexibility or size of the paper is insufficient. That is, in Comparative Example 1, the softener for paper having a mass ratio (A / B) of the acid salt of the condensate (component A) and the tertiary amine compound (component B) exceeding 95/5 is used. The resulting paper has insufficient flexibility (bending stiffness). In Comparative Example 2, a paper softener having a mass ratio (A / B) of the acid salt of the condensate (component A) to the tertiary amine compound (component B) of less than 60/40 is used. The resulting paper has insufficient flexibility and size. In Comparative Example 3, the softener for paper does not use the acid salt of the condensate, so that the resulting paper has insufficient flexibility. In Comparative Example 4, since the softener for paper having a small number of carbon atoms in the condensate raw material carboxylic acid is used, the resulting paper has insufficient flexibility and size. In Comparative Example 5, since the paper softener in which the raw material carboxylic acid of the condensate is an unsaturated carboxylic acid (oleic acid) is used, the size of the obtained paper is insufficient. In Comparative Example 6, since the paper softener having a high urea condensation rate of the condensate is used, the obtained paper has insufficient flexibility (bending stiffness). In Comparative Example 7, since the paper softening agent having a low urea condensation rate of the condensate is used, the resulting paper has insufficient size properties. In Comparative Example 8, since the paper softener having a large number of moles of carboxylic acid with respect to the amino group of the amidoamine compound constituting the condensate is used, the flexibility of the obtained paper is insufficient. In Comparative Example 9, since the softener for paper having a small number of moles of carboxylic acid with respect to the amino group of the amidoamine compound constituting the condensate is used, the flexibility and size of the obtained paper are insufficient. In Comparative Example 10, since the paper softener having a short alkyl group in the tertiary amine compound is used, the size of the obtained paper is insufficient. In Comparative Examples 11 and 12, since the paper softener having a different structure of the tertiary amine compound is used, the size of the obtained paper is insufficient. In Comparative Example 13, since the paper softener does not contain a tertiary amine compound, the resulting paper has insufficient flexibility (bending stiffness). In Comparative Example 14, in the paper softener, the number of moles of carboxylic acid with respect to the amino group of the amidoamine compound constituting the condensate is large and does not contain a tertiary amine compound, so that the resulting paper has insufficient flexibility. is there. In Comparative Example 15, since the softener for paper does not contain the acid salt of the condensate, the resulting paper has insufficient flexibility and size.

  ADVANTAGE OF THE INVENTION According to this invention, the softener for paper which is excellent in a softness | flexibility and can obtain the paper which has sufficient size property is provided. When this paper softener is used, a paper that is flexible and excellent in size can be obtained. Such paper can be widely used for paper in various fields such as bookbinding paper, newsprint, printing / information paper, cardboard base paper, and paperboard.

Claims (2)

A softener for paper comprising an acid salt (A) of a condensate of an amidoamine compound and urea and a tertiary amine compound (B),
The amidoamine compound has the following formula (1):
R ¹ NH— (R ² —NH) _n —R ³ (1)
^{(R 1} and ^{R 3} is a hydrogen atom or an alkyl group of carbon number 1 to 3, ^{R 2} is an alkylene group having 1 to 4 carbon atoms, and n is 2-4) is represented by A polyamine compound (1);
A carboxylic acid having 10 to 24 carbon atoms and containing 35% by mass or more of a saturated carboxylic acid,
It is obtained by reacting at a ratio such that the carboxyl group of the carboxylic acid is 0.4 to 0.8 mol with respect to 1 mol of the amino group of the polyamine compound (1).
The urea condensation rate of the condensate is 10 to 50%,
The tertiary amine compound (B) is represented by the following formula (2):

(R ⁴ is an alkyl or alkenyl group having 8 to 20 carbon atoms, M ¹ and M ² are each a hydrogen atom or an alkali metal, and x and y are each 1 to 3), And the mass ratio A / B of the acid salt (A) of the condensate and the tertiary amine compound (B) is 95/5 to 60/40.
Softener for paper.   The manufacturing method of paper including the process of adding the softening agent for paper of Claim 1 so that it may become 0.03-8 mass parts with respect to 100 mass parts of pulp.