JP2009041158A - Softener for paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a softener for paper, which gives flexibility and a good touch feeling to the paper while suppressing the reduction of strength of the paper, and further inhibiting the reduction of yield of the paper in its production processes. <P>SOLUTION: This softener for the paper contains (A) an amideamine compound expressed by formula (1) [wherein, R<SP>1</SP>CO is a 10-24C acyl; R<SP>2</SP>is a 2-4C alkylene; and R<SP>3</SP>, R<SP>4</SP>are each a 1-4C alkyl], and (B) a polyacrylamide having a viscosity of 10% aqueous solution at 25°C of 3,000 to 20,000 mPa s, and having a weight ratio (A)/(B) of the amideamine compound (A) to the polyacrylamide (B) of (70/30) to (95/5). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a paper softener.

  Paper is used for various purposes in daily life as sanitary paper such as printing paper used for comic books and paperbacks, toilet paper, and tissue paper. In recent years, regardless of whether it is printing paper or sanitary paper, there has been a demand for paper that is flexible, easy to turn and comfortable to touch. Therefore, many paper softeners have been developed so far.

Examples of paper softeners for obtaining flexible paper include paper softeners containing a quaternary ammonium salt having a long-chain alkyl, a fatty acid and a fatty acid ester of pentaerythritol (for example, see Patent Document 1), alkylene A softener for paper containing a nonionic surfactant having an oxide and a cationic surfactant having a long-chain alkyl (for example, see Patent Document 2), amorphous silica or silicate, and a water-resistant agent are included. A method of applying a surface treatment agent (for example, see Patent Document 3) is known. Furthermore, a method of producing a paper with a good texture while maintaining paper strength by using a water-soluble polysaccharide and an acrylamide polymer as a paper strength enhancer in combination with machine control in the papermaking process has been attempted (for example, (See Patent Document 4). When this method is used, paper strength is improved and flexibility is also improved.
JP 7-189171 A JP 2004-44058 A Japanese Patent Laid-Open No. 10-226982 JP 2002-201587 A

  However, the paper softeners disclosed in the aforementioned Patent Documents 1 and 2 improve the flexibility of the paper, but reduce the strength of the paper. In addition, the paper softener containing an ammonium salt disclosed in Patent Document 3 is insufficient in both the effect of imparting paper flexibility and the effect of suppressing strength reduction. In addition, the paper softener disclosed in Patent Document 4 significantly disturbs the texture and surface uniformity of the paper, so that high-quality paper cannot be obtained. In addition, when the paper softener shown in Patent Document 4 is added to the pulp slurry, which is a papermaking raw material, in the papermaking process, the drainage of the pulp slurry is reduced, so the operability of the papermaking process is reduced, and the fine fibers are reduced. The yield of manufactured paper is reduced due to the outflow.

  In view of such circumstances, the present invention gives the paper flexibility and touch comfort while suppressing a decrease in the strength of the paper, and has good operability when added to the pulp slurry in the production process, and the yield of the paper. An object of the present invention is to provide a paper softener that suppresses the decrease.

  As a result of intensive studies to solve the above-described conventional problems, the present inventors have found that a paper softener combining a specific amidoamine compound and a specific polyacrylamide can achieve the above object, and has completed the present invention. It came to do.

  The paper softener according to the present invention includes an amidoamine compound (A) represented by the formula (1), a polyacrylamide (B) having a 10% aqueous solution viscosity of 3,000 to 20,000 mPa · s at 25 ° C. The weight ratio (A) / (B) of the amidoamine compound (A) to the polyacrylamide (B) is 70/30 to 95/5.

In the formula, R ¹ CO is an acyl group having 10 to 24 carbon atoms, R ² is an alkylene group having 2 to 4 carbon atoms, and R ³ and R ⁴ are alkyl groups having 1 to ⁴ carbon atoms.

  The paper softener according to the present invention may have a salt obtained by neutralizing the amidoamine compound (A) with an acid instead of all or part of the amidoamine compound (A).

  By neutralizing all or part of the above to form a salt, it becomes easy to prepare a paper softener dispersion.

  The softening agent for paper of the present invention can impart a soft hand feeling to the paper while suppressing a decrease in the strength of the paper by adding to the material in the paper making process or to the paper after production. Further, when the paper softener according to the present invention is used, productivity in the paper making process is improved, and the product yield is increased, so that the manufacturing cost of paper can be reduced.

  The paper softener of the present invention comprises an amidoamine compound (A) represented by the formula (1) and a polyacrylamide (B) whose viscosity of a 10% aqueous solution at 25 ° C. is 3,000 to 20,000 mPa · s. Have. Accordingly, each compound will be described first, and then a paper softener embodying the present invention and a paper example containing the paper softener will be described.

  1. Amidoamine compound (A)

（式中Ｒ^１ＣＯは炭素数１０〜２４のアシル基であり、Ｒ^２は炭素数２〜４のアルキレン基であり、Ｒ^３およびＲ^４は炭素数１〜４のアルキル基である。） The amidoamine compound (A) is represented by the formula (1).

(Wherein R ¹ CO is an acyl group having 10 to 24 carbon atoms, R ² is an alkylene group having 2 to 4 carbon atoms, and R ³ and R ⁴ are alkyl groups having 1 to ⁴ carbon atoms.)

R ¹ CO in the formula (1) is an acyl group derived from a fatty acid having 10 to 24 carbon atoms. If the carbon number is less than 10, the “soft feel” imparted to the paper by the paper softener becomes insufficient. Moreover, even if the number of carbons exceeds 24, a “supple feel” can be imparted to the paper, but an effect commensurate with the increase in the number of carbons cannot be obtained and it is difficult to obtain. Therefore, R ¹ CO preferably has 10 to 24 carbon atoms. Examples of such fatty acids include saturated fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, and lignoceric acid, and branched fatty acids such as isopalmitic acid and isostearic acid. Examples include unsaturated fatty acids such as palmitoleic acid, oleic acid, linoleic acid, linolenic acid, elaidic acid, and erucic acid.

R ² in the formula (1) is an alkylene group having 2 to 4 carbon atoms. This compound having 1 carbon atom has an insufficient “supple feel”. Even if the number of carbons exceeds 5, a “supple feel” can be imparted to the paper, but an effect commensurate with the increase in the number of carbons cannot be obtained and it is difficult to obtain. Examples of the alkylene group having 2 to 4 carbon atoms include an ethylene group, a propylene group, and a butylene group. A propylene group is preferred.

R ³ and R ^{4 in} Formula (1) are alkyl groups having 1 to 4 carbon atoms. Even if the number of carbon atoms in the alkyl group exceeds 4, a “soft feel” can be imparted to paper, but an effect commensurate with the increase in the number of carbon atoms cannot be obtained and it is difficult to obtain. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, and an isobutyl group.

  The amidoamine compound (A) can be used as it is, but in order to facilitate the preparation of a paper softener dispersion, it is preferably neutralized with an inorganic acid or an organic acid to form a salt. Examples of the inorganic acid include hydrochloric acid, sulfuric acid, carbonic acid, nitric acid, phosphoric acid and the like. Examples of the organic acid include formic acid, acetic acid, propionic acid, butyric acid, glycolic acid, lactic acid, gluconic acid, salicylic acid, hydroxyvaleric acid, astraginic acid, glutamic acid, taurine, sulfamic acid and the like.

  2. Polyacrylamide (B)

  The polyacrylamide (B) may be any of anionic polyacrylamide, cationic polyacrylamide, and amphoteric polyacrylamide. However, in any polyacrylamide, the viscosity of a 10% aqueous solution at 25 ° C. is preferably 3,000 to 20,000 mPa · s. When this viscosity is less than 3,000 mPa · s, the effect of agglomeration of fine fibers by polyacrylamide (B) becomes insufficient, and the drainage when paper softener is added to the material in the papermaking process, and the manufactured paper Yield decreases. On the other hand, when the viscosity is greater than 20,000 mPa · s, the effect of agglomeration of the fine fibers becomes too great and the uniformity of the paper surface is lowered. Therefore, the viscosity of a 10% aqueous solution of polyacrylamide (B) at 25 ° C. is preferably 3,000 to 20,000 mPa · s. The viscosity was measured with a 10% aqueous solution of polyacrylamide (B) at 25 ° C. using a B-type viscometer (rotor No. 4, 30 rpm).

  Among the polyacrylamides satisfying such requirements, examples of the anionic polyacrylamide include a copolymer of acrylamide and an anionic monomer such as acrylic acid and methacrylic acid, and a partial hydrolyzate of polyacrylamide. Examples of the cationic polyacrylamide include a Mannich modified product of polyacrylamide, a Hofmann degradation product, or a copolymer of acrylamide and a cationic monomer. Here, as the cationic monomer, dimethylaminoethyl methacrylate, diallyldimethylammonium chloride, diallyldiethylammonium chloride, methacryloyloxyethyltrimethylammoniummethylammonium methylsulfate, methacryloyloxyethylammonium methylchloride, methacrylamidopropyltrimethylammonium chloride, etc. Is used. Examples of the amphoteric polyacrylamide include a copolymer of acrylamide and the above anionic monomer and cationic monomer, a Mannich modified product of a copolymer of acrylamide and the above anionic monomer, and a Hoffman degradation product. Among these, cationic polyacrylamide or amphoteric polyacrylamide is preferable from the viewpoint of improving the supple feel and suppressing the reduction in paper strength.

  3. Softener for paper

  The softening agent for paper consists of an amidoamine compound (A) and a polyacrylamide compound (B). At this time, if the weight ratio (A) / (B) between the ester compound (A) and the compound (B) exceeds 95/5, the decrease in strength of the paper using the paper softener cannot be sufficiently suppressed. In addition, the drainage when the paper softener is added in the paper making process and the yield of the manufactured paper are reduced. When the weight ratio is less than 70/30, the paper cannot be sufficiently supple. Therefore, the weight ratio (A) / (B) needs to be 70/30 to 95/5. Further, the paper softener may be dispersed in a dispersion medium and used as a dispersion of the paper softener. Note that water is preferable as the dispersion medium. The amidoamine compound (A) is preferably neutralized with an inorganic acid or an organic acid to form a salt in order to facilitate the preparation of a paper softener dispersion.

  4). Manufacture of paper containing paper softener

  Paper containing a paper softener is produced by adding the paper softener to the papermaking raw material at any stage of the papermaking process.

  The paper softener is preferably added in an amount of 0.03 to 8 parts by weight, more preferably 0.10 to 4 parts by weight, based on 100 parts by weight of the pulp. If the amount is less than 0.03 parts by weight, the paper is not sufficiently soft to the touch, and if it is added in an amount of 8 parts by weight or more, the effect of improving the softness of the paper becomes dull.

  The kind of pulp to be used is not particularly limited. For example, chemical pulp (such as bleached or unbleached kraft pulp of softwood or hardwood), mechanical pulp (such as ground pulp, thermomechanical pulp, chemithermomechanical pulp), deinked pulp (such as newspaper and magazine waste paper) can be used. These may be used alone or in combination.

  The paper softener may be added at any stage of the papermaking process. For example, a method of internally adding a paper softener in a process such as a mixing chest, a machine chest, or a seed box can be used. By adding this paper softener and other additives as described later to a mixture containing pulp and water (for example, pulp slurry) and making paper using the obtained mixture by a normal method. Thus, a paper containing a paper softener can be produced without complicating the production process. The paper making method is not particularly limited, and any paper machine such as a long paper machine, a twin wire machine, and a Yankee machine can be used.

  On the other hand, an external addition method in which the paper softener is applied to the surface of the pulp sheet obtained by the paper making process can also be employed. Examples of the external addition method include a size press, a gate roll, and a spray method.

  In addition, it is also possible to use various additives generally used in the paper making process in combination with the paper softener according to this embodiment. These additives include various enhancers and sizing agents, drainage, yield improvers, and other internal additives.

The present invention will be described more specifically with reference to examples and comparative examples.
The sheet strength was evaluated based on the tear length. The breaking length is the length when the paper is cut by its own weight when one end of the paper is fixedly suspended. The strength of the paper increases as the tear length increases.

[Production example of paper softener]
First, a synthesis example of an amidoamine compound (A) and a paper production example using a paper softener are shown.

  (Synthesis Method of Amidoamine Compound (A))

  As examples of the amidoamine compound (A) constituting the present invention, compounds a-1 to a-4 and a compound a-5 to be compared were synthesized. Details of these compounds are shown in Table 1.

  ・ Synthesis of a-1

Using the fatty acid and dialkylaminoalkyleneamine shown in Table 1, compound a-1 was synthesized by the synthesis method shown below. This compound a-1 has a methyl group formula (1) oleic acid-derived product as ^R 1 CO in the propylene group as the alkylene group ^{R 2,} the alkyl group of ^{R 3} and ^{R 4.}

  A 500 ml four-necked flask equipped with a stirrer, condenser, thermometer and nitrogen inlet tube was charged with 252.0 g (0.9 mol) of oleic acid and 91.8 g (0.9 mol) of dimethylaminopropylamine, While stirring in a nitrogen gas atmosphere, the temperature was raised to 180 to 190 ° C., and the reaction was carried out for 15 hours while removing the generated water from the reaction system to obtain amidoamine compound a-1 having an amine value of 149.

  ・ Synthesis of a-2

Compound a-2 was synthesized in the same manner as compound a-1 using the fatty acid and dialkylaminoalkyleneamine shown in Table 1. This compound a-1 has a methyl group formula (1) ^R 1 CO as myristic acid-derived compound in an ethylene group as the alkylene group according to ^{R 2,} the alkyl group according to ^{R 3} and ^{R 4.}

  ・ Synthesis of a-3

Compound a-3 was synthesized in the same manner as compound a-1 using the fatty acid and dialkylaminoalkyleneamine shown in Table 1. In addition, the mixed fatty acid used as a derivative of R ¹ CO in the formula (1) was mixed with myristyl acid, palmitic acid, stearic acid, and arachidic acid at a weight ratio of 2%, 31%, 66%, and 1%, respectively. Is.

  ・ A-4

  Compound a-4 was synthesized in the same manner as Compound a-1 using the fatty acid and dialkylaminoalkyleneamine shown in Table 1.

  ・ A-5

Compound a-5 was synthesized in the same manner as for compound a-1, using the fatty acid and dialkylaminoalkyleneamine shown in Table 1. In addition, the 2-ethylhexanoic acid origin used as an origin of R < ¹ > CO in Formula (1) is C8, and does not satisfy | fill the requirement of R < ¹ > CO of this invention.

(Compound (B))

  As examples of the polyacrylamide compound (B) constituting the paper softener of the present invention, compounds b-1 to b-3 and compounds b-4 and b-5 to be compared are shown in Table 2 below. Show. Here, b-4 (manufactured by Seiko PMC Co., Ltd .; Stargum KX-12) has a viscosity of 1200 mPa · s at 25 ° C. in a 10% aqueous solution, and is 3000 mPa · s or less, and therefore constitutes polyacrylamide constituting the present invention. The requirements for compound (B) are not satisfied. Further, b-5 (manufactured by Miki Co., Ltd .; Emco Gum CSAA) is mainly composed of guar gum and is not a polyacrylamide compound (B) constituting the present invention.

(Example of paper softener production)

  Paper softeners 1 to 5 were produced as examples of the paper softener, and paper softeners 6 to 10 were produced as comparative examples. Details of these softeners for paper are shown in Table 3.

  -Production of softener for paper of Example 1

  Compound a-1 was used as the amidoamine compound (A), and b-1 was used as the polyacrylamide compound (B).

  In a 200 ml beaker equipped with a stirrer, 141.5 g of ion-exchanged water, 16.0 g of amidoamine compound a-1 and 2.5 g of acetic acid (corresponding to 1.0 equivalent to the amine value of a-1) were quantified. The mixture was stirred for 30 minutes while raising the temperature to 70 ° C. to obtain a 10% dispersion of amidoamine compound a-1. Further, 17.8 g of polyamide compound b-1 was added in a mass ratio as shown in Table 3, the temperature was raised to 70 ° C. while stirring, and the mixture was stirred for 30 minutes to obtain a dispersion of paper softener 1.

  Production of paper softeners of Examples 2-5 and paper softeners of Comparative Examples 6-10

  The amidoamine compound (A) and the polyacrylamide compound (B) were charged at a mass ratio shown in Table 3, and in the same manner as in the production of the dispersion liquid of the paper softener 1 in Example 1, the examples 2 to 5 were used. Dispersions of paper softeners 2-5 and dispersions of paper softeners 6-10 of Comparative Examples 6-10 were obtained. Note that acetic acid is not used in the dispersion of the paper softener 4 of Example 4 and the dispersion of the paper softener 6 of Comparative Example 6, and the paper softeners 8 and 9 of Comparative Examples 8 and 9 are used. Formic acid (corresponding to 1.0 equivalent to the amine value of a-1 and a-2) was used in place of acetic acid. Further, the amidoamine compound (A) was not used in the dispersion of the paper softener 6 of Comparative Example 6.

(Paper production example)

  Paper using the paper softeners of Examples 1 to 5 and paper using the paper softeners of Comparative Examples 6 to 10 were produced.

LBKP (hardwood bleached pulp) having a freeness of 430 ml was disaggregated with a disaggregator (manufactured by Kumagaya Riken Co., Ltd.) to prepare a pulp slurry containing 1 mass percent of pulp. 400 g of this pulp slurry is put into a beaker having a capacity of 500 ml (pulp quality 4 g), and 2.0 g of softener for paper 1 to 10 (0.5% by mass as an active ingredient) is added, and the outer diameter is 4.5 cm. The mixture was stirred for 1 minute at 250 rpm by a turbine blade. 105 g of the slurry after stirring is made with a TAPPI standard machine (manufactured by Yasuda Seiki Co., Ltd.), pressed with a hydraulic press machine (manufactured by Yasuda Seiki Co., Ltd.) at 0.35 MPa for 5 minutes, and then a drum dryer (Yasuda Seiki Co., Ltd.) The product was dried at 105 ° C. for 2 minutes to produce a paper having a basis weight of 60 g / m ² . This paper was placed in a constant temperature and humidity chamber adjusted to a temperature of 23 ° C. and a humidity of 50% for 17 hours to adjust the humidity.

  Hereinafter, the paper after humidity control is simply referred to as a sheet, and the sheets manufactured using the dispersion liquid of the paper softeners 1 to 10 in the above process are referred to as sheets 1 to 10, respectively.

[Evaluation method and evaluation results]

  Then, the evaluation method and evaluation result of the paper containing a paper softening agent are demonstrated.

  (Evaluation methods)

・ Evaluation of supple touch feeling About the touch feeling of sheets 1 to 10, 10 evaluators touched each sheet, and scored according to the following criteria, respectively, and the total score was 30 points or higher (◯), 30 points Less than was evaluated as insufficient (x). However, when 3 or more out of 10 evaluators gave 1 point, it was evaluated as insufficient (x) regardless of the total score.
Score Supple feel 5 Very supple feel.
4 Good supple feel.
3 There is a supple feel.
2 Equivalent to the case of no paper softener added.
1 The supple feel is worse than when no paper softener is added.

・ Sheet strength Three 120 × 15 mm test pieces are cut from each sheet. The tensile strength until the specimen was broken by pulling from both ends was measured with a tensile / compression tester (SV-201-0-SH manufactured by Imada Manufacturing Co., Ltd.) and measured according to JIS P 8113. The tear length was calculated.
Breaking length (km) = (Tensile strength x 1000) / (9.81 x Specimen width (mm) x Specimen basis weight (g / m ² ))
The same operation was performed on the three test pieces, and the average value was obtained.
Further, the ratio of the tear length of each sheet was divided by the tear length of the sheet 6, and the ratio was determined.
90% or more Good strength: ○
Less than 90% Insufficient strength: ×

・ Evaluation of drainage In the same manner as in the paper production example described above, LBKP (hardwood bleached pulp) having a freeness of 430 ml was disaggregated with a disaggregator (manufactured by Kumagaya Riken Co., Ltd.), and pulp containing 0.5% by mass of pulp A slurry was prepared. 500 g of this pulp slurry is incorporated into a jar of an inner diameter of 10.1 cm, a height of 15.2 cm, and a 50 mesh dynamic drainer (manufactured by Paper Research Materials inc.) For 0.5% by weight paper based on the active component of the pulp. Softener was added. After stirring for 1 minute at a rotation speed of 1000 rpm in the jar, the faucet at the drainage sampling port was opened for 30 seconds while stirring in the jar, the filtrate was collected, and its weight was measured and evaluated according to the following criteria.
Drainage amount 450g or more Good drainage: ○
Less than 450 g of drainage Insufficient drainage: ×

・ Evaluation of yield The filtered water collected in the drainage evaluation was filtered through a filter paper (5 types A as defined in JIS P 3801) whose weight was measured in advance, and the filter paper was dried at 105 ° C. for 2 hours. The weight was measured again. The solid content weight in the filtrate was determined from the difference in weight of the filter paper before and after filtration.
Weight of solid content in filtrate is less than 300 mg Good yield: ○
Weight of solid content in filtered water is 300mg or more. Insufficient yield: ×

  (Evaluation analysis)

  Table 3 shows the results of evaluation using the above evaluation method. Table 3 shows the following.

  -Confirmation of the effect of the softener for paper according to the present invention

  The sheets 1 to 5 of the examples using the paper softener according to the present invention have good supple feel, paper strength, drainage, and yield.

-About the weight ratio (A) / (B) of an amidoamine compound (A) and the said polyacrylamide (B).

  The weight ratio (A) / (B) between the amidoamine compound (A) and the polyacrylamide (B) increases in the order of the sheet 9, the sheet 4, the sheet 5, the sheet 2, the sheet 1, and the sheet 3 with the sheet 6 as a minimum. ing. Further, the strength of the sheet decreases almost in this order. From this, it can be seen that as the amount of the amidoamine compound (A) increases, the supple feel becomes larger while the strength of the sheet decreases. In particular, the strength at the same weight ratio (A) / (B) 95/5 (sheet 3) is 92.5% relative to the blank (sheet 6), and the weight ratio (A) / (B) exceeds 95/5. It is estimated that the strength of the paper is insufficient (x). Therefore, the weight ratio (A) / (B) is preferably 95/5 or less. On the other hand, it can be seen that the examples (sheet 9 and sheet 6) in which the weight ratio (A) / (B) is 70/30 or less are insufficient in the supple feel. Therefore, the weight ratio (A) / (B) is preferably 70/30 or more.

- formula (1) acyl group ^(R 1 CO) for in.

Acyl group (a-2) derived from myristic acid, which is a linear saturated fatty acid having 14 carbon atoms, acyl group (a-1) derived from oleic acid, which is an unsaturated fatty acid having 18 carbon atoms, straight-chain unsaturated group having 22 carbon atoms An acyl group (a-4) derived from erucic acid, which is a saturated fatty acid, and an acyl group (a-3) derived from a mixed fatty acid of myristic acid, palmitic acid, stearic acid, and arachidic acid, ^{If the} number of carbon atoms of ¹ CO) is within the range of 10 to 24, it can be used for the amidoamine compound used in the paper softener according to the present invention. It is understood from satisfying. On the other hand, the “flexible touch” of the sheet 7 using the acyl group (a-5) derived from 2-ethylhexanoic acid, which is an aliphatic group having less than 10 carbon atoms, that is, 8 carbon atoms, of the acyl group (R ¹ CO). Since the evaluation is insufficient (x), the acyl group (R ¹ CO) in the amidoamine compound (A) used in the paper softener according to the present invention preferably has 10 to 24 carbon atoms.

-About R < ² >, R < ³ >, R < ⁴ > in Formula (1).

An ethylene group or a propylene group is used for the alkylene group R ² having 2 to 4 carbon atoms, an ethyl group or a methyl group is used for the alkyl groups R ³ and R ⁴ having 1 to 4 carbon atoms, and the acyl group R ¹ CO is as described above. Each of the evaluations of the sheets 1 to 4 can be used for the amidoamine compound used in the paper softener according to the present invention using the fatty acid-derived product of It can be seen from the result that both evaluation items are satisfied.

  -About polyacrylamide compound (B).

  The compounds b-1 to b-3 that satisfy the requirements for the polyacrylamide compound (B) according to the present invention can be used for the amidoamine compound used in the paper softener according to the present invention. It can be seen that each evaluation result satisfies all evaluation items.

  On the other hand, if a compound whose main component is guar gum and does not satisfy the requirements of the polyacrylamide compound (B) according to the present invention is used, the sheet strength of the sheet 10 cannot be sufficiently suppressed. It can be seen from the evaluation. Even when a polyacrylamide compound is used, a 10% aqueous solution having a viscosity at 25 ° C. of 1200 mPa · s and having a viscosity of 3000 mPa · s or less can sufficiently suppress a decrease in paper strength. It cannot be seen from the evaluation of the sheet strength of the sheet 8. Conversely, if the viscosity under the same conditions is 20,000 mPa · s or more, the uniformity of the paper surface may be impaired. Therefore, the viscosity of the polyacrylamide compound according to the present invention at 25 ° C. in a 10% aqueous solution must be 3000 mPa · s to 20,000 mPa · s.

  ・ About acid for neutralization

  The paper softener added to the sheet 4 does not use neutralizing acid. Even in this case, each evaluation criterion is satisfied, and it can be seen that there is no problem in terms of sheet quality during use. Therefore, it is presumed that the presence or absence of the neutralizing acid does not affect the efficacy of the paper softener. That is, if the compound (A) is a salt neutralized with an acid or the compound (A) itself, any amount of the compound (A) is contained in the paper softener according to the present invention. It is presumed to have efficacy as an agent.

  However, the compound (A) can be easily neutralized with an acid and converted into a salt when preparing a paper softener dispersion.

  ADVANTAGE OF THE INVENTION According to this invention, the softening agent for paper which can provide a touch feeling softly to paper is provided, adding to the paper manufacturing process or the paper after manufacture, suppressing the fall of the intensity | strength of paper. . In addition, when the softening agent is used, the yield increases in the paper making process, and the paper manufacturing cost can be reduced.

Claims (2)

An amidoamine compound (A) represented by the formula (1) and a polyacrylamide (B) having a viscosity of 3,000 to 20,000 mPa · s in a 10% aqueous solution at 25 ° C.,
A softener for paper, wherein the weight ratio (A) / (B) of the amidoamine compound (A) to the polyacrylamide (B) is 70/30 to 95/5.

(Wherein R ¹ CO is an acyl group having 10 to 24 carbon atoms, R ² is an alkylene group having 2 to 4 carbon atoms, and R ³ and R ⁴ are alkyl groups having 1 to ⁴ carbon atoms.)   A softener for paper having a salt obtained by neutralizing the amidoamine compound (A) with an acid instead of all or part of the amidoamine compound (A) according to claim 1.