JP4694367B2 - Method for producing paper quality improver - Google Patents

Description

  The present invention relates to a method for producing a paper quality improver.

  From the viewpoint of protecting the global environment, there is a demand for reducing the amount of pulp used, that is, reducing the weight of paper and increasing the amount of recycled pulp. However, the paper obtained simply by reducing the amount of pulp in the paper and increasing the blending ratio of the used paper pulp reduces the opacity due to the thinner paper and the further disadvantage due to the increase in the used paper pulp that reduces the paper thickness compared to the virgin pulp. Decrease in transparency and whiteness occurs, resulting in poor quality. In addition, simple weight reduction that reduces the amount of pulp in paper results in paper becoming substantially thin, resulting in poor texture required for books and the like.

Conventionally, various methods for improving the bulk have been attempted for the purpose of preventing the thickness from decreasing due to weight reduction. For example, the production method for reducing the press pressure has a problem that the smoothness is lowered and the printability is inferior. In addition, a method using a cross-linked pulp or a method of mixing with synthetic fibers has been proposed, but it is not desirable because the pulp cannot be recycled or the smoothness of the paper is impaired. Therefore, at present, several commercial products have been marketed and frequently used as bulking agents for paper. Specifically, it is widely used as a specific alcohol and / or its polyoxyalkylene adduct (Patent Document 1), an ester compound of a polyhydric alcohol and a fatty acid (Patent Document 2), or a paper softener or sizing agent. There have been amidoamine compounds and the like.
International Publication No. 98/03730 Pamphlet Japanese Patent No. 2971447

  However, although the compounds of Patent Documents 1 and 2 can achieve a certain amount of weight reduction, they are still insufficient for the further demand for weight reduction.

  An object of the present invention is to solve the above-mentioned problems associated with weight reduction of paper and an increase in the amount of waste paper pulp. Specifically, compared with a conventional bulking agent, further weight reduction (bulk improvement), It is an object of the present invention to provide a production method capable of obtaining a paper quality improver that achieves an improvement in whiteness and opacity, or a paper quality improver with less reduction in paper strength even with an equivalent increase in bulk.

  In the present invention, the ratio of the polyhydric alcohol (A) [hereinafter referred to as the component (A)] and the fatty acid (B1) having 8 to 36 carbon atoms having 2 or more unsaturated groups in the molecule is 20 to 95% by weight. And a fatty acid mixture (B) [hereinafter referred to as component (B)] to react to produce a partially substituted ester compound mixture (hereinafter also referred to as the ester mixture of the present invention), a paper quality improver It relates to the manufacturing method.

  The present invention also includes a paper containing the paper quality improver obtained by the production method of the present invention, and a form in which the paper quality improver obtained by the production method of the present invention is dissolved or dispersed in water or an aqueous solvent. It relates to a method for producing a paper to be added to a pulp slurry and made paper.

  According to the present invention, compared with the conventional bulking agent, even higher weight reduction (bulk improvement), whiteness improvement, paper quality improvement agent that can achieve opacity improvement, or even if the bulk improvement is equivalent, There is provided a production method capable of obtaining a paper quality improver with little reduction in paper strength.

  Paper obtained by using the paper quality improver of the present invention produced by such a production method is superior in improving bulk, improving whiteness, and improving opacity compared to paper obtained using a conventional paper quality improver. .

  As for paper strength, paper obtained using the paper quality improver of the present invention is relatively less deteriorated in paper strength than paper obtained using conventional paper quality improvers.

  Similarly, regarding the coefficient of friction, the paper obtained using the paper quality improver of the present invention has a relatively small decrease in the coefficient of friction compared to the paper obtained using the conventional paper quality improver.

  That is, according to the present invention, it is possible to solve various problems associated with lightening paper and increasing the amount of waste paper pulp. Specifically, it is possible to reduce paper weight (increase bulk), improve whiteness, and improve opacity. Furthermore, a paper quality improver with less reduction in paper strength and friction coefficient is provided.

  In the present invention, paper refers to paper in which pulp fibers are widely bound by hydrogen bonds, binders, etc. to form a sheet.

  In the following, if no percentage and dilution ratio are specified, the weight is used.

<(A) component>
The polyhydric alcohol used in the present invention is preferably a compound having 2 to 10 valences, more preferably 3 to 6 valent hydroxyl groups, and a polyhydric alcohol having 2 to 10 total carbon atoms which may contain an ether group. Is preferred. As the dihydric alcohol, those having a total carbon number of 2 to 10 which may contain an ether group, for example, propylene glycol, dipropylene glycol, butylene glycol, dibutylene glycol, ethylene glycol, diethylene glycol, polyethylene glycol are trivalent or more. As the alcohol of the above, an alcohol having 3 to 24 carbon atoms which may have an ether, which has a total hydroxyl number / total carbon number in one molecule = 0.4 to 1, for example, glycerin, poly (n = 2-5) Glycerin, pentaerythritol, dipentaerythritol, arabitol, sorbitol, stachyose, erythritol, arabit, mannitol, glucose, sucrose and the like. Preferably, it is an ethylene glycol, diethylene glycol, propylene glycol, an alcohol having a total number of carbon atoms of 3 to 12 which may have an ether group, and the number of hydroxyl groups in one molecule / total number of carbons is 0.5 to 1 or more. Of alcohol. More preferred are glycerin, poly (n = 2 to 4) glycerin, and pentaerythritol, and most preferred is pentaerythritol.

<(B) component>
The component (B) used in the present invention comprises a fatty acid (B1) having 8 or more unsaturated groups in the molecule (hereinafter referred to as fatty acid (B1)) and other fatty acids, Fatty acid (B2) [hereinafter referred to as fatty acid (B2)] having 0 or 1 unsaturated group in the molecule is used.

  The fatty acid (B1) may be linear or branched. The number of carbon atoms of the fatty acid (B1) is preferably 12 to 28, and more preferably 16 to 24. The number of unsaturated groups in the fatty acid (B1) is preferably 2-4.

  The fatty acid (B2) may be linear or branched. The number of carbon atoms of the fatty acid (B2) is preferably 8 to 36, and more preferably 12 to 24. The number of unsaturated groups in the fatty acid (B2) is preferably 0.

  In order to obtain the ester mixture of this invention, it is preferable to make (A) component and (B) component react. Usually, the composition of the unsaturated group in the component (B) is reflected in the composition of the unsaturated group in the ester mixture substantially as it is. Therefore, the component (B) is a fatty acid mixture containing the fatty acid (B1) and the fatty acid (B2) in a weight ratio of (B1) / (B2) = 20/80 to 95/5.

  When a mixture of partially substituted ester compounds composed of a fatty acid mixture containing a fatty acid (B1) having two or more unsaturated groups in a specific ratio is used, as in this component (B), this weight ratio is deviated. Compared to a partially substituted ester compound composed of a fatty acid mixture or a single fatty acid, it can realize high bulk improvement, whiteness improvement, and opacity improvement even with a relatively small addition amount, and substantially less because the addition amount is small. The decrease in paper strength is also improved. The mechanism of this action is not clear, but the molecular chain is greatly deformed by the unsaturated group, so that the packing property of the molecular arrangement is lowered, and the wetting and spreading on the surface after fixing to the cellulose surface is improved. It is guessed. On the other hand, in the ester composed of a fatty acid mixture containing less than 5% by weight or more than 95% by weight of the fatty acid (B1) in the component (B), the paper quality improving effect tends to be reduced. It is inferred that this is because of an excessive rise. From this, the (B1) / (B2) weight ratio in the component (B) is preferably 30/70 to 80/20, more preferably 40/60 to 70/30.

  (B) As a component, it is preferable to use the fatty acid derived from natural fats and oils as a raw material from a cost viewpoint. The natural fats and oils are terrestrial animal and vegetable oils and marine animal and vegetable oils such as coconut oil, beef tallow, fish oil, linseed oil, rapeseed oil, soybean oil, castor oil, and soybean oil is particularly preferable. And the fatty acid derived from natural fats and oils is obtained by decomposing the natural fats and oils or curing or fractionating after the decomposition. Alternatively, it is obtained by preliminarily curing or fractionating oils and fats and then decomposing them. Alternatively, the oil and fat recovered in the oil and fat refining step can be obtained by decomposing in the same manner. Furthermore, if the fatty acid derived from natural fats and oils satisfies the fatty acid (B1) content [(B1) / (B2) weight ratio] of the present invention, it can be used as it is as the component (B).

<Ester mixture>
The ester mixture of the present invention is a mixture of partially substituted ester compounds and can be obtained by a conventionally known esterification reaction. For example, it can be obtained by adding an esterification catalyst to the mixture of the component (A) and the component (B) and reacting at 150 to 250 ° C. if necessary, or the component (B) with phosphorus trichloride or the like. It can also be obtained by treating to acid chloride, mixing this with component (A), and adding and reacting with an alkali catalyst if necessary. It can also be obtained by a transesterification method.

  When the component (A) is glycerin, the partially substituted ester compound of the present invention may be a partially decomposed ester of oil or fat, or an ester obtained by curing, fractional distillation, or the like.

  Furthermore, you may obtain the ester mixture of this invention by mixing the some partially substituted ester compound prepared separately.

  As described above, the ester mixture of the present invention is a mixture of partially substituted ester compounds, and the average degree of substitution of the mixture (ratio in which the hydrogen of the hydroxyl group of the polyhydric alcohol is substituted with a fatty acid) is the viewpoint of the paper quality improvement effect. 10 to 95 equivalent% is preferable, and 25 to 85 equivalent% is more preferable. In addition, the average degree of substitution of the partially substituted ester compound can be controlled by the ratio of the component (A) and the component (B) used in the reaction.

  Further, the partially substituted ester compound of the present invention can have an oxyalkylene group, particularly an oxyalkylene group having 2 to 4 carbon atoms, and such a structure can be obtained by performing a conventionally known alkylene oxide addition reaction. I can do it. At that time, alkylene oxide can be added during the esterification reaction or in the presence of an alkali catalyst or the like after the reaction, or after addition of alkylene oxide to component (A) or (B), esterification is performed. May be.

  When an ester compound containing an oxyalkylene group having 2 to 4 carbon atoms (hereinafter referred to as OA group) is used as the partially substituted ester compound according to the present invention, the number is more than 0 mol and less than 12 mol on an average per mol of the ester compound. Preferably, 0.1-9 mol is more preferable.

  In addition, when the polyhydric alcohol which can become OA group like ethylene glycol etc. is used, they are also included in OA group.

  The alkylene oxide is preferably ethylene oxide (EO) or propylene oxide (PO). These may be EO, PO, or a mixture of EO and PO.

  In addition, the partially substituted ester compound or ester mixture of the present invention has a melting point of preferably 100 ° C. or less, more preferably −50 ° C. or more and 90 ° C. or less, and still more preferably −20 ° C. from the viewpoint of handleability and performance expression. The temperature is 80 ° C. or lower, more preferably −20 ° C. or higher and 60 ° C. or lower, and still more preferably −20 ° C. or higher and 40 ° C. or lower. The melting point is defined as the temperature at which the amount of heat at which the ester compound cooled in advance is measured with a differential scanning calorimeter (DSC) (temperature increase rate 2 ° C./min) exhibits a peak.

  About the ester mixture of this invention, when (B) component of a structural component is known, the value based on a well-known literature etc. can be employ | adopted as a composition of (B) component. Moreover, about an unknown component, the composition of (B) component can be known by analyzing about the fatty acid which obtained the ester mixture with the following method.

<Method for measuring fatty acid composition of partially substituted ester compound>
[I] An excess of methanol and an inorganic acid such as boron trifluoride are added to the sample, and the mixture is heated to 70 to 80 ° C. for solvolysis to methyl esterify the constituent fatty acid. The reaction mixture is extracted with water-hexane or the like, and purified by removing acid and water-soluble components. Specifically, the following procedure is performed.

(1) Weigh 0.4 to 0.6 g of the sample into a 200 mL conical Erlenmeyer flask and add about 20 mL of methanol to dissolve.
(2) Put about 3 mL of BF ₃ -methyl alcohol complex and boiling stone, attach an air-cooled tube and immerse in a water bath at 73 to 80 ° C. for 5 to 10 minutes. At this time, the temperature is adjusted so that the steam becomes 1/2 or less of the air-cooled tube.
(3) After standing to cool, transfer the methyl esterified product to 400 mL of a separatory funnel, add about 80 mL of 10% sodium chloride solution, and extract with about 80 mL of hexane.
(4) The hexane layer is washed with about 70 mL of 10% sodium chloride solution until neutral. Check with methyl orange indicator solution.
(5) About 10 g of anhydrous sodium sulfate is added to the hexane layer for dehydration, and then filtered through a filter paper into another 300 mL Erlenmeyer flask.
(6) Attach to a hexane distillation apparatus and distill off hexane at about 50 ° C.
(7) About 10 mL of hexane is added to the residue to prepare a sample concentration of about 5%.

[II] The purified mixture is analyzed by gas chromatography. However, for the retention time and strength of each fatty acid methyl ester, it is necessary to obtain reagents and prepare a calibration curve. The gas chromatograph operating conditions are as follows.

Model [Shimadzu Corporation] GC-7AG
Detector FID
Column temperature 180 ± 10 ° C
Detector temperature 270 ± 10 ° C
Inlet temperature 270 ± 20 ℃
Sample injection volume 1μL (5% hexane solution)
Sensitivity 2mV, 100mA 8 × 10 ²
Carrier gas flow rate 60mL / min (helium)
Column 2m / 3mmφ
Data processing device C-R1A

<Paper quality improver>
The paper quality improver of the present invention is added in any of the papermaking processes, and the liquid product may be added as it is, but the solid product is pulverized or heated and melted or diluted with water or the like. It may be added. Further, if necessary, a nonionic, anionic, cationic, polymer, preferably nonionic surfactant may be used as an emulsifier or dispersant, and it may be used in the form of an aqueous dispersion. In this case, the ratio of the paper quality improver of the present invention to the surfactant is [paper quality improver of the present invention] /surfactant=99.5/0.5 to 70/30 (weight ratio), preferably 98. / 2 to 80/20.

  The paper quality improver of the present invention preferably contains 50 to 100% by weight, more preferably 70 to 100% by weight, of the ester mixture of the present invention. The reaction product containing the ester mixture of the present invention obtained by the reaction of the component (A) and the component (B) as described above is used as it is or after appropriately removing unreacted components and the like, and used as a paper quality improver. be able to.

  As the paper quality improver of the present invention, a fatty acid mixture in which the ratio of the polyhydric alcohol (A) and the fatty acid (B1) having 8 to 36 carbon atoms having two or more unsaturated groups in the molecule is 20 to 95% by weight. What contains the mixture of the partially substituted ester compound obtained from (B) is mentioned.

  The pulp raw materials to which the paper quality improver of the present invention can be applied include a wide variety of pulps ranging from mechanical pulps such as TMP (thermomechanical pulp) and chemical pulps such as LBKP (hardwood bleached pulp) to various waste paper pulps. Generally applicable. In addition, the place of addition of the paper quality improver of the present invention is not particularly limited as long as it is a papermaking process until a diluted liquid of pulp raw material is filtered while forming a paper layer while traveling on a wire mesh, For example, in a factory, a place where it can be uniformly blended with a pulp raw material, such as being added by a refiner, a machine chest, or a head box is desirable. Note that the paper quality improver of the present invention is added to the pulp raw material and then made as it is and remains on the paper. The addition amount of the paper quality improver of the present invention, preferably the ester mixture of the present invention is 0.01 to 10% by weight, preferably 0.1 to 5% by weight, based on the pulp raw material. Even if a small amount of 1 to 1% by weight is added, an excellent paper quality improvement effect can be obtained.

  The paper obtained using the paper quality improver of the present invention has a lower degree of tension than the conventional paper quality improver (the measurement method is according to the method described in the Examples below), which is exemplified in the Examples. ing.

  In addition, during paper making, in addition to sizing agents such as rosin, alkyl ketene dimer, alkenyl succinic acid, gelatin, starch, and latex, fillers, retention agents, drainage agents, paper strength agents, and the like may be added.

  In particular, in order for the paper quality improver of the present invention to exhibit its function, it is important that the partially substituted ester compound according to the present invention is fixed to the pulp, and for that purpose, an agent that promotes fixing of the ester compound is used. It is preferable to add. Examples of the agent that promotes fixing include inorganic substances such as aluminum sulfate, amide compounds such as PAM, and cationic compounds such as polyethyleneimine and PDADMAC. The amount of the agent that promotes fixing is preferably 0.001 to 5 parts by weight with respect to 100 parts by mass of the pulp raw material.

  Also, the paper obtained using the paper quality improver of the present invention is a newspaper roll in the item classification described in pages 455 to 460 of “Paper and Pulp Technology Handbook” (issued by the Pulp and Paper Technology Association, 1992), It is suitably used for paper such as printing / information paper and wrapping paper, or paperboard, and particularly suitable for printing / information paper.

  In addition, since deinked pulp tends to deteriorate whiteness, opacity, weight reduction, etc., the paper quality improver of the present invention is preferably used when a pulp raw material containing deinked pulp is used. A good effect is seen when the content of deinked pulp is 10% or more of the whole pulp.

(1) Manufacture of paper quality improver The ester mixture of the composition shown in Table 1 was manufactured using the fatty acid shown below, and it used as a paper quality improver. In addition, all the ester mixtures of Table 1 had a melting point of 100 ° C. or lower.

(1-1) Paper quality improver No. 1. Production of 1 452 g of soybean oil fatty acid (alkyl composition is as follows) and 204 g of pentaerythritol (reagent) were placed in a 1 L four-necked flask, heated to 150 ° C. with stirring under a nitrogen stream, and held for 30 minutes. Then, it heated up to 235 degreeC and dehydration reaction was performed for 4 hours. The acid value at that time was 0.15 KOH mg / g.
The reaction mixture was once cooled to 70 ° C., aged for 1 hour, and filtered under reduced pressure using a filter bed (radiolite # 900) to remove unreacted pentaerythritol, and the ester average substitution degree was 45 equivalent%. Paper quality improver No. 1 (450 g) was obtained.

* Alkyl composition of soybean oil fatty acid (% is mass%, the same applies hereinafter)
C16 5-12%
C18 2-7%
C18: 1 20-35%
C18: 2 50-57%
C18: 33-8%
C20 or more 0 to 2%

  In the above, the number after C is the number of carbon atoms. For example, C18: 2 represents a fatty acid having 18 carbon atoms and two double bonds in the carbon chain (the same applies hereinafter). , "Introduction to fat and oil chemistry from basics to applications" (written by Tomohiro Kurosaki and Kazuhisa Yagi, Sangyo Tosho, published in September 1995) (the same applies hereinafter).

(1-2) Paper quality improver No. 2-3, no. Production of 12-14 According to the production of the paper quality improver 1, an ester mixture having the composition shown in Table 1 was produced using the following fatty acids and used as the paper quality improver.
* Alkyl composition of soybean oil fatty acid (high boiling fraction) C16 29-30%
C18 12-14%
C18: 1 13-15%
C18: 2 33-36%
C18: 3 4-6%
C14 or less 0 to 1%
C20 or more 0 to 2%

* Alkyl composition of linseed oil fatty acid C16 4-9%
C16: 10 to 1%
C18 2-5%
C18: 1 20-35%
C18: 2 5-20%
C18: 3 30-58%
C20 or more 0 to 2%

(1-3) Paper quality improver No. Production of 4 Into a 1L 4-necked flask, 297 g of soybean oil, 6.3 g of glycerin, and 0.96 g of potassium hydroxide were added, and the ester exchange reaction was carried out for 4 hours by raising the temperature to 150 ° C. while stirring under a nitrogen stream. An ester mixture (275 g) having an average degree of substitution of 80 equivalent% was produced. Used as 4.

(1-4) Paper quality improver No. 5-7, no. Production of 15 According to the production of the paper quality improver 4, an ester mixture having the composition shown in Table 1 was produced using the following fatty acids and used as a paper quality improver.

* Alkyl composition of corn oil fatty acid C16 7-13%
C18 2-5%
C18: 1 25-45%
C18: 2 40-60%
C18: 30-3%
C20 or more 0 to 1%

* Alkyl composition of peanut oil fatty acid C16 6-13%
C18 2-7%
C18: 1 35-70%
C18: 2 20-40%
C18: 30 to 1%
C14 or less 0 to 2%
C20 or more 3-14%

* Alkyl composition of palm kernel oil fatty acid C8 3-5%
C10 3-7%
C12 44-55%
C14 10-17%
C16 6-10%
C18 1-7%
C18: 1 1-17%
C18: 20 to 2%

(1-5) Paper quality improver No. Production of 8 A 1.5 L autoclave was charged with 416 g of soybean oil, 8.8 g of glycerin, and 1.34 g of potassium hydroxide, and heated to 120 ° C. with stirring. Next, 101 g of EO was reacted with the above reaction product to produce an ester mixture having an ester average substitution degree of 80 equivalent% and an EO average addition mole number of 4 mol, which was used as the paper quality improver 8. The reaction conditions at this time were a temperature of 145 ° C. and a pressure of 80 to 400 kPa.

(1-6) Paper quality improver No. Production of No. 9-11 Paper quality improver No. According to the production of No. 8, an ester mixture having the composition shown in Table 1 was produced and used as a paper quality improver.

(1-7) Preparation of aqueous dispersion of paper quality improver 1 part by weight, 10 parts by weight of lauryltrimethylammonium chloride (Coatamine 24; Kao Corporation) 0.5 part by weight (in terms of solid content), 0.5 part by weight of lauryl alcohol EO adduct (Emulgen 147; Kao Corporation) The mixture is mixed and made up to 100 parts by weight with ion-exchanged water, and stirred for 1 minute at 6000 rpm with a homomixer made by Tokushu Kika Kogyo Kogyo. 1 aqueous dispersion was obtained. Paper quality improver No. Also about 2-15, the aqueous dispersion was prepared by said method except having heated to 50-70 degreeC as needed (paper quality improvement agent No.2 and No.12).

(2) Evaluation (paper making method)
The LBKP was used after being disaggregated and beaten with a beater at room temperature to make 2.2% LBKP slurry. Canadian Standard Freeness was 420 ml. After the above pulp is weighed so that the basis weight of the sheet after making paper is 80 g / m ² after the papermaking, the cationized starch (CATO308, manufactured by Nippon SC) 0.5% (Weight basis, for pulp, the same applies hereinafter), 1.0% industrial sulfuric acid band and 1% aqueous dispersion of paper quality improver (Table 1) (as ester mixture) were added with stirring, and the pulp concentration was then 0 Diluted with water to 5%, cationic polyacrylamide yield improver (Percoll 47, manufactured by Ciba Specialty Chemicals) 0.015%, after stirring with 150 mesh wire with square tappi paper machine Papermaking and coaching were performed to obtain wet paper. The wet paper after paper making was pressed with a press at 3.5 kg / cm ² for 5 minutes and dried at 105 ° C. for 2 minutes using a drum dryer.

  The obtained paper was conditioned at 23 ° C. and a humidity of 50% RH for 1 day, and various physical properties were measured by the following methods. The results are shown in Table 1.

(Tensity)
The basis weight (g / m ² ) and thickness (mm) of the conditioned paper were measured, and the tightness (g / cm ³ ) was determined by the following formula.
Calculation formula: (tensity) = [(basis weight) / (thickness)] × 0.001
The smaller the absolute value, the higher the bulk, and the 0.02 g / cm ³ difference in the tension is fully recognized as a significant difference.

(Burst strength)
The burst strength was measured according to JIS P8112 as a paper strength measurement item. A difference of 0.01 MPa is well recognized as a significant difference.

(Whiteness)
Based on JIS P 8123, Hunter whiteness (WB) was measured and set as whiteness. Differences of whiteness of 0.5 points or more are recognized as significant differences.

(Opacity)
Opacity was measured based on JIS P 8138A. Differences with an opacity of 0.5 points or more are recognized as significant differences.

(Coefficient of friction)
Based on JIS P 8147, the static friction coefficient and the dynamic friction coefficient were measured. In any friction coefficient, a difference of 50 points or more is recognized as a significant difference.

  In the table, PT is pentaerythritol and GL is glycerin.

  As shown in Table 1, the paper quality improver No. 1 of the present invention. In Examples 1 to 11 using 1 to 11, all of bulk performance, whiteness, opacity, burst strength, static friction coefficient, and dynamic friction coefficient are good results. On the other hand, in Comparative Example 1 using only saturated fatty acids, bulk performance is recognized, but paper strength and friction are reduced. Comparative Example 2 using a fatty acid having only one unsaturated group, Comparative Example 3 using a fatty acid having a fatty acid (B1) ratio of 100% by weight, and a fatty acid mixture having a fatty acid (B2) ratio of 2% by weight or less In Comparative Example 4 using No, the bulk performance is not sufficient. Moreover, the comparative example 5 which does not use a paper quality improver tends to be inferior in bulk performance and inferior in whiteness and opacity.

Claims (7)

  Partially reacting a polyhydric alcohol (A) with a fatty acid mixture (B) in which the ratio of the fatty acid (B1) having 8 to 36 carbon atoms having two or more unsaturated groups in the molecule is 20 to 95% by weight. A method for producing a paper quality improver, comprising a step of producing a mixture of substituted ester compounds.   The method for producing a paper quality improver according to claim 1, wherein the polyhydric alcohol is a dihydric to bivalent polyhydric alcohol.   The method for producing a paper quality improver according to claim 1 or 2, wherein the fatty acid (B1) is a fatty acid derived from natural fats and oils.   The method for producing a paper quality improver according to any one of claims 1 to 3, wherein the fatty acid mixture contains 8 to 36 carbon atoms of fatty acids other than the fatty acid (B1).   The paper quality improvement agent obtained with the manufacturing method of the paper quality improvement agent in any one of Claims 1-4.   A paper containing the paper quality improver according to claim 5.   A method for producing paper, wherein the paper quality improver according to claim 5 is added to a pulp slurry in a form dissolved or dispersed in water or an aqueous solvent to make paper.