阅读说明：本技术 纸浆的洗涤 (Washing of pulp ) 是由 榎本幸典 于 2019-11-12 设计创作，主要内容包括：提供能够提高“脱水性”和“洗涤性”的纸浆洗涤剂。在一个方式中,涉及一种纸浆洗涤剂,其含有下述式(1)所示的非离子表面活性剂。R～(1)O-[(EO)-(n)·(PO)-(m)]H···(1)式(1)中,R～(1)为碳原子数10～14的烷基或炔基,EO和PO分别为氧乙烯基和氧丙烯基,n和m为平均加成摩尔数,n和m分别不为0。(Provided is a pulp detergent which can improve the "dewatering property" and the "washing property". In one embodiment, the present invention relates to a pulp detergent containing a nonionic surfactant represented by the following formula (1). R 1 O‑[(EO) n ·(PO) m ]H (1) formula (1) wherein R 1 The carbon atom number of the EO layer is 10-14, the EO and the PO are respectively an oxyethylene group and an oxypropylene group, n and m are average addition mole numbers, and n and m are not 0 respectively.)

1. A pulp detergent containing a nonionic surfactant represented by the following formula (1) and having a weight average molecular weight of 600 to 1300 inclusive,

R¹O-[(EO)_n·(PO)_m]H···(1)

in the formula (1), R¹The carbon atom number of the EO layer is 10-14, the EO and the PO are respectively an oxyethylene group and an oxypropylene group, n and m are average addition mole numbers, and n and m are not 0 respectively.

2. A pulp detergent comprising a nonionic surfactant represented by the following formula (1),

R¹O-[(EO)_n·(PO)_m]H···(1)

in the formula (1), R¹Is an alkyl group or an alkynyl group having 10 to 14 carbon atoms, EO and PO are an oxyethylene group and an oxypropylene group, respectively, n and m are average addition mole numbers, n and m are not 0, respectively, and n + m is 8 to 22.

3. A method for producing pulp, comprising adding the pulp detergent according to claim 1 or 2 to a pulp washing step.

4. The pulp production method according to claim 3, wherein the pulp washing step is a step of washing the pulp before pulp bleaching.

Technical Field

The present invention relates to the washing of pulp and, in one or more embodiments, to pulp detergents and methods of pulp manufacture.

Background

The manufacturing process for kraft pulp typically includes: a digestion step of digesting the wood chips with a mixed solution of caustic soda and sodium sulfide (Japanese text of digestion: digestion); an unbleached pulp washing step of separating a black liquor containing pulp and lignin; an oxygen delignification step for removing lignin from the pulp by using oxygen and alkali; and a bleaching process. If the unbleached pulp is not sufficiently washed, the reaction efficiency in the oxygen delignification step is lowered, the amount of bleaching chemicals used is increased, and foaming and pitch problems occur in the multistage bleaching step, the concentration step and the papermaking step, and therefore, the pulp washing after the unbleached pulp washing step and after the oxygen delignification step, that is, the pulp washing before the bleaching step is very important.

As a pulp washing method, a pulp washing method in which a polyoxyethylene alkylphenyl ether surfactant is added to various washing steps in a pulp production method (patent document 1), a pulp washing method in which a surfactant is added to a washing step after a digestion step (patent documents 2 and 3), and the like have been proposed.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 5-302284

Patent document 2: japanese patent laid-open publication No. 2005-336620

Patent document 3: WO2009/093615

Disclosure of Invention

Problems to be solved by the invention

The pulp has excellent water absorption, and the pulp sent from the digestion step contains about 80 mass% of water. Pulp washing is generally performed by diluting an absolutely dry pulp concentration to about 1 mass% slurry by adding a dilution liquid to the pulp, followed by dewatering. Depending on the type of detergent, a method of replacing the water in the pulp with a washing liquid after dewatering may be used. It is considered that if the dewatering property of pulp is improved, the pulp can be concentrated to a higher concentration, and the washing efficiency is improved.

Further, if the efficiency of removing the dirt contained in the pulp after the pulp washing can be improved, the load of the subsequent oxygen delignification step and bleaching step can be reduced. Therefore, in the present invention, the whiteness of pulp is used as an index for improving the efficiency of removing the stain.

The present invention provides a pulp detergent capable of improving both "dewatering properties" and "washing properties".

Means for solving the problems

The present invention relates to a pulp detergent containing a nonionic surfactant represented by formula (1) and having a weight average molecular weight of 600 to 1300 inclusive.

R¹O-[(EO)_n·(PO)_m]H···(1)

(in the formula (1), R¹Is an alkyl group or an alkynyl group having 10 to 14 carbon atoms, EO and PO are an oxyethylene group (Japanese text: エチレンオキサイド group for oxyethylene group) and an oxypropylene group (Japanese text: プロピレンオキサイド group for oxypropylene group), respectively, n and m are average addition mols, and n and m are not 0, respectively. )

In another aspect, the present invention relates to a pulp detergent containing a nonionic surfactant represented by the following formula (1).

R¹O-[(EO)_n·(PO)_m]H···(1)

(in the formula (1), R¹Is an alkyl group or an alkynyl group having 10 to 14 carbon atoms, EO and PO are an oxyethylene group and an oxypropylene group, respectively, n and m are average addition mole numbers, n and m are not 0, respectively, and n + m is 8 to 22. )

In another aspect, the present invention relates to a method of making pulp comprising adding the pulp detergent of the present invention.

Effects of the invention

According to one or more embodiments of the present invention, a pulp detergent capable of improving both "dewatering properties" and "washing properties" can be provided.

Detailed Description

The invention is based on the following insight: among the surfactants, nonionic surfactants satisfying predetermined requirements can improve the dewatering property and the washing property in pulp washing. The invention is based on the following insight: the nonionic surfactant satisfying the predetermined requirements can increase the oven dry pulp concentration of the pulp after pulp washing and can improve the whiteness of the pulp after pulp washing.

The pulp washing agent of the present invention can improve both "dewatering property" and "washing property" in one embodiment, and therefore, in one or more embodiments, reduction in the amount of washing liquid used, reduction in the amount of bleaching agent used, improvement in the reaction efficiency of oxygen delignification, reduction in the amount of antifoaming agent used, prevention of problems in a papermaking process due to pitch reduction, increase in the solid content concentration of dilute black liquor fed to a recovery boiler, and the like can be expected.

[ nonionic surfactant (a): first embodiment

The nonionic surfactant contained in the pulp detergent of the present invention is a nonionic surfactant (a) represented by formula (1) and having a weight average molecular weight of 600 to 1300 inclusive.

R¹O-[(EO)_n·(PO)_m]H···(1)

(in the formula (1), R¹The carbon atom number of the EO layer is 10-14, the EO and the PO are respectively an oxyethylene group and an oxypropylene group, n and m are average addition mole numbers, and n and m are not 0 respectively. )

The nonionic surfactant (A) is a polyoxyethylene polyoxypropylene alkyl ether represented by the above formula (1).

From the viewpoint of improving the dewatering property and the detergency, the weight average molecular weight of the nonionic surfactant (a) is 600 or more and 1300 or less, preferably 600 or more and 1200 or less, more preferably 600 or more and 1100 or less, further preferably 600 or more and 1000 or less, further preferably 650 or more and 950 or less, further preferably 650 or more and 900 or less, further preferably 650 or more and 800 or less, further preferably 650 or more and 750 or less.

The weight average molecular weight of the nonionic surfactant (a) can be measured by Gel Permeation Chromatography (GPC).

From the viewpoint of improving the dehydration property and the detergency, the number of carbon atoms in the alkyl ether moiety of the nonionic surfactant (A), that is, R in the formula (1)¹Number of carbon atoms ofIt is 10 or more and 14 or less, preferably 10 or more and 13 or less.

As provision of "R¹Examples of the alcohol base material of the O- "portion include decanol, isodecanol, lauryl alcohol, tridecyl alcohol, isotridecyl alcohol, and myristyl alcohol from the viewpoint of improving the dehydration property and the detergency, and isodecanol and tridecyl alcohol are preferable.

The average addition mole number n of oxyethylene (EO) moieties and the average addition mole number m of oxypropylene (PO) moieties of the nonionic surfactant (A) are not zero. From the viewpoint of improving the dewatering property and the cleaning property, the total of n and m (n + m) is preferably 8 or more and 22 or less, more preferably 8 or more and 21 or less, further preferably 8 or more and 20 or less, further preferably 8 or more and 17 or less, and more preferably 9 or more and 15 or less.

[ (EO) of formula (1)_n·(PO)_m]The polymerization order of EO and PO in the moiety is not particularly limited. The EO and PO may be in a random or block form.

N and m of the nonionic surfactant (A) can be measured by NMR and/or mass analysis.

From the viewpoint of improving the dewatering property and the detergency, the EO/PO (ratio of EO to PO) of the nonionic surfactant (a) is preferably 35/75 or more, more preferably 40/60 or more, and still more preferably 50/50 or more. From the same viewpoint, EO/PO (ratio of EO to PO) is preferably 95/5 or less, more preferably 90/10 or less, and further preferably 85/15 or less.

[ nonionic surfactant (B): second embodiment

A second embodiment of the nonionic surfactant contained in the pulp detergent of the present invention is a nonionic surfactant (B) represented by the following formula (1).

R¹O-[(EO)_n·(PO)_m]H···(1)

(in the formula (1), R¹Is an alkyl group or an alkynyl group having 10 to 14 carbon atoms, EO and PO are an oxyethylene group and an oxypropylene group, respectively, n and m are average addition mole numbers, n and m are not 0, respectively, and n + m is 8 to 22. )

The nonionic surfactant (B) is a polyoxyethylene polyoxypropylene alkyl ether represented by the above formula (1).

The average molar number n of addition of the oxyethylene (EO) ("oxyethylene" Japanese text: オキシエチレン) moiety and the average molar number m of addition of the oxypropylene (PO) ("oxypropylene" Japanese text: オキシプロピレン) moiety of the nonionic surfactant (B) are not zero. From the viewpoint of improving the dewatering property and the cleaning property, the total of n and m (n + m) is 8 or more and 22 or less, preferably 8 or more and 21 or less, more preferably 8 or more and 20 or less, still more preferably 8 or more and 17 or less, and still more preferably 9 or more and 15 or less.

[ (EO) of formula (1)_n·(PO)_m]The polymerization order of EO and PO in the moiety is not particularly limited. The EO and PO may be in a random or block form.

N and m of the nonionic surfactant (B) can be measured in the same manner as the method for measuring n and m of the nonionic surfactant (A).

From the viewpoint of improving the dewatering property and the detergency, the EO/PO (ratio of EO to PO) of the nonionic surfactant (B) is preferably 35/75 or more, more preferably 40/60 or more, and still more preferably 50/50 or more. From the same viewpoint, EO/PO (ratio of EO to PO) is preferably 95/5 or less, more preferably 90/10 or less, and further preferably 85/15 or less.

From the viewpoint of improving the dewatering property and the detergency, the weight average molecular weight of the nonionic surfactant (B) is preferably 600 or more and 1300 or less, more preferably 600 or more and 1200 or less, further preferably 600 or more and 1100 or less, further preferably 600 or more and 1000 or less, further preferably 650 or more and 950 or less, further preferably 650 or more and 900 or less, further preferably 650 or more and 800 or less, further preferably 650 or more and 750 or less.

The weight average molecular weight of the nonionic surfactant (B) can be measured in the same manner as the method for measuring the weight average molecular weight of the nonionic surfactant (a).

From the viewpoint of improving the dehydration property and the detergency, the number of carbon atoms in the alkyl ether moiety of the nonionic surfactant (B), that is, R in the formula (1)¹The number of carbon atoms of (b) is 10 to 14, preferably 10 to 13.

As provision of "R¹Examples of the alcohol base material of the O- "portion include decanol, isodecanol, lauryl alcohol, tridecyl alcohol, isotridecyl alcohol, and myristyl alcohol from the viewpoint of improving the dehydration property and the detergency, and isodecanol and tridecyl alcohol are preferable.

[ pulp detergent ]

The pulp detergent of the present invention comprises the above-mentioned nonionic surfactant (a) or (B). The number of the nonionic surfactants may be 1 or more.

The pulp detergent of the present invention may contain a nonionic surfactant, and may also contain water and other components.

Examples of the other components include components that do not substantially impair the dehydrating property and the cleaning property. As other components, in one or more embodiments, defoaming agents, pitch control agents, scale control agents, and the like can be given.

The formulation of the pulp detergent is not particularly limited. Preferably a liquid when used.

The pulp detergent of the present invention can be used as a detergent for pulp washing in a pulp production process. In one or more embodiments, the pulp washing in the pulp production step in the present invention includes washing of the pulp performed before the stage of bleaching in the bleaching step, for example, washing of unbleached pulp. The position of addition of the pulp detergent of the present invention is not particularly limited as long as the pulp washing in the pulp production process is performed in one or more embodiments, and examples thereof include a position where unbleached pulp is washed. In one or more embodiments, the location where the unbleached pulp is washed may be, for example, washing performed after the digestion step and before the oxygen delignification reaction step, washing performed after the oxygen delignification reaction step and/or after the reaction step, or the like.

Accordingly, in another aspect, the present invention relates to a method for washing pulp using the pulp detergent of the present invention, and in yet another aspect, to a method for producing pulp including a step of washing pulp using the pulp detergent of the present invention.

The kind of pulp to be washed or manufactured is not particularly limited, and pulp including a step of washing pulp in the manufacturing process may be included. In one or more embodiments, the raw material pulp may be wood pulp (N wood (coniferous tree) or L wood (broadleaf tree)), or non-wood pulp, or waste paper pulp.

In one or more embodiments, the wood pulp may be chemical pulp such as kraft pulp, sulfide pulp (japanese text: サルファイドパルプ for sulfide pulp), alkali pulp, or mechanical pulp.

[ method of washing pulp ]

In one or more embodiments, the pulp washing method of the present invention includes adding the pulp detergent of the present invention to a diluent or a washing liquid used in a pulp washing step. In one or more other embodiments, the pulp washing method of the present invention comprises adding the pulp detergent of the present invention to the pulp diluted with the diluent and the pulp to which the washing liquid is added in the pulp washing step. The pulp washing method of the present invention in one or more other embodiments includes adding the pulp detergent of the present invention to a pulp washing machine.

In one or more embodiments, the pulp washing step may be performed before the bleaching step.

The washing machine is not particularly limited and may be appropriately selected according to the purpose, and examples thereof include a drum filter, a diffuser, a pressure type diffuser, a pressurized drum filter, a pressurized washer, and a twin-roll press. As the pulp washing step, a multistage washing step in which a plurality of these washing machines are combined is preferable.

The position of addition of the pulp detergent of the present invention to the washing machine is not particularly limited as long as it can be uniformly mixed with the pulp, and examples thereof include a suction port of a pump for feeding the pulp to the washing machine, an inlet port of a dilution liquid for adjusting the pulp concentration, a suction port of a liquid feeding pump for the dilution liquid, and a suction port of a liquid feeding pump for the washing liquid.

In one or more embodiments, the amount of the pulp detergent of the present invention used in the pulp washing method of the present invention is preferably 0.003 to 10% by mass, more preferably 0.005 to 1% by mass, and still more preferably 0.01 to 0.1% by mass, based on the mass of the oven-dried pulp.

The washing temperature in the pulp washing method of the present invention may be a normal washing temperature or a temperature of a washing machine, and may be 65 to 90 ℃ in one or more embodiments.

[ method for producing pulp ]

The pulp production method of the present invention is, in one or more embodiments, a pulp production method including a step of performing the pulp washing method of the present invention.

One or more embodiments of the pulp production method of the present invention include a production method including the steps of: a digestion process; an unbleached pulp washing step (unbleached pulp washing step 1) performed after the digesting step; an oxygen delignification reaction process; and an unbleached pulp washing step (unbleached pulp washing step 2) performed after the oxygen delignification reaction step. In one or more embodiments of the pulp making process of the present invention, the washing of unbleached pulp can use the pulp detergent of the present invention.

Steaming process

The above-mentioned digesting step is a step of digesting the pulp raw material. In the above-described digestion step, for example, the pulp raw material (wood chips) is pressure-digested in a mixed solution of sodium hydroxide and sodium sulfide, and the non-fiber portion such as lignin component, sodium salt of fatty acid, sodium salt of rosin acid, and the like in the pulp raw material is dissolved. Examples of the digestion include a sulfate digestion method and a sulfite digestion method.

Unbleached pulp washing step 1

The pulp raw material after the digestion is separated into pulp slurry and black liquor in unbleached pulp washing step 1 and washed. In unbleached pulp washing step 1, in one or more embodiments, removal of foreign matter (e.g., dissolved organic components, etc.) in the pulp slurry may be included.

Oxygen delignification reaction procedure

The oxygen delignification reaction step is a step of decomposing lignin components contained in the pulp raw material after the above-mentioned digestion by using oxygen, that is, a step of decomposing lignin components which have not been completely removed in the above-mentioned digestion step, and an oxygen delignification method in which oxygen is allowed to act under an alkaline and high-temperature pressure in an initial stage after the digestion treatment has been developed and widely used at present. Since 40% to 50% of lignin remaining in the pulp after the digestion step is decomposed by performing the oxygen delignification reaction, not only can the amount of chlorine-based bleaching agent used in the subsequent stage be reduced, but also the drainage water generated in the oxygen delignification reaction step can be circulated to the digestion step, and therefore, the agent and energy can be recovered, and the load of drainage water can be reduced.

Unbleached pulp washing step 2

In one or more embodiments, the unbleached pulp washing step 2 (washing step after the oxygen delignification reaction step) is a step of removing lignin decomposition products, colored components, and the like generated by the oxygen delignification reaction by washing.

The washing step after the oxygen delignification reaction step may be performed before the bleaching step.

The pulp is washed, for example, by adding a diluent to the pulp (pulp concentration of about 10 mass%) fed from the digestion step to prepare a slurry having a pulp concentration of about 1 mass%. The amount of pulp detergent of the present invention used in the washing of pulp is as described above.

The washing of the pulp is generally carried out by a convection multistage washing method, but the use of the pulp detergent of the present invention and the pulp washing method of the present invention may not be limited to this method.

The convection multistage washing method is generally a method of washing by connecting 2 to 5 washing machines in series. There are cases where clean water is used only for the washing liquid in the final washing machine (warm water recovered from the boiler, i.e., washing warm water). The washing liquid recovered in the washing machine of the final stage is used as the washing liquid in the washing machine of the previous stage, and the washing liquid used in the washing machine of the previous stage is further recovered and used as the washing liquid in the washing machine of the previous stage. The collected washing liquid is also used as the diluent in the previous stage. When such a convection washing method is used, not only the reagents used in the digestion step and the oxygen delignification reaction step can be recovered at high concentration, but also the lignin decomposition product can be recovered at high concentration.

The temperature of the pulp slurry introduced into the washing machine, i.e., the washing temperature, is usually 65 to 90 ℃ and is the temperature of the pulp slurry in the cylinder (vat) (Japanese text: バット) of the washing machine.

Other procedures

The other step is not particularly limited and may be appropriately selected according to the purpose, and examples thereof include a bleaching step and the like.

Bleaching process

The bleaching step is a step of bleaching the pulp after the washing step, and an oxidizing agent such as chlorine, hypochlorite, chlorine dioxide, ozone, or hydrogen peroxide may be used.

The invention also relates to one or more of the following embodiments.

A pulp detergent containing a nonionic surfactant represented by the following formula (1) and having a weight average molecular weight of 600 to 1300 inclusive.

R¹O-[(EO)_n·(PO)_m]H···(1)

(in the formula (1), R¹The carbon atom number of the EO layer is 10-14, the EO and the PO are respectively an oxyethylene group and an oxypropylene group, n and m are average addition mole numbers, and n and m are not 0 respectively. )

A pulp detergent containing a nonionic surfactant represented by the following formula (1).

R¹O-[(EO)_n·(PO)_m]H···(1)

(in the formula (1), R¹Is an alkyl group or an alkynyl group having 10 to 14 carbon atoms, EO and PO are an oxyethylene group and an oxypropylene group, respectively, n and m are average addition mole numbers, n and m are not 0, respectively, and n + m is 8 to 22. )

A process for producing pulp, which comprises adding the pulp detergent of [ 1] or [ 2] to a pulp washing step.

The method of producing pulp according to [ 3 ], wherein the pulp washing step is a step of washing the pulp before bleaching the pulp.

The present invention will be further described with reference to examples. However, the present invention is not to be construed as being limited to the following examples.

Examples

(example 1)

Unbleached pulp (hardwood kraft pulp) from an actual paper mill and chemicals described in table 1 were used to wash the pulp under the following conditions, and the absolute pulp concentration and whiteness after washing were measured.

The results are shown in table 1. Note that the pulp concentration (oven dry pulp concentration) and whiteness in table 1 are expressed as values (difference from blank) obtained by subtracting the results when no chemical agent was added (blank).

Pulp washing

The pulp was defibrated by a defibrator at 2500rpm for 5 minutes to prepare a pulp slurry of 1.5% (weight of the oven-dried pulp), and the slurry was heated at 70 ℃ for 2 hours or more. Next, 500ppm of the chemical (surfactant) shown in Table 1 was added to the oven-dried pulp at 60 ℃ and the mixture was stirred at 700rpm for 1 minute. After completion of the stirring, the total amount of the pulp was suction-filtered, and the absolute pulp concentration and the whiteness of the pulp sheet produced were measured for each of the obtained pulps.

Method for measuring the concentration of oven-dried pulp:

the pulp was dried at 105 ℃ and then measured as dry solid content concentration.

Method for measuring whiteness:

a pulp sheet was produced according to JIS P8222, and measured by using a Spectro photometer (manufactured by Nippon Denshoku industries Co., Ltd., PF 7000).

[ weight average molecular weight ]

The weight average molecular weight of the drug (surfactant) is a value measured by Gel Permeation Chromatography (GPC).

[ Agents ]

Example 1-1: polyoxyethylene polyoxypropylene Monoisodecyl Ether (EO (9.3), PO (2.3), EO/PO ═ 80/20, weight average molecular weight 700)

Examples 1 to 2: polyoxyethylene polyoxypropylene Monoisodecyl Ether (EO (5.7), PO (8.5), EO/PO ═ 40/60, weight average molecular weight 900)

Examples 1 to 3: polyoxyethylene polyoxypropylene Monoisodecyl Ether (EO (12.6), PO (8.4), EO/PO ═ 60/40, weight average molecular weight 1200)

Examples 1 to 4: polyoxyethylene polyoxypropylene monotridecyl ether (EO (7.1), PO (2.4), EO/PO ═ 75/25, weight average molecular weight 650)

Comparative example 1: polyoxyethylene monoisodecyl ether (EO (7), weight average molecular weight 466)

Comparative example 2: polyoxyethylene polyoxypropylene monotridecyl ether (EO (5.1), PO (2.2), EO/PO ═ 70/30, weight average molecular weight 550)

Comparative example 3: pluronic type surfactants (EO (25.5), PO (29), EO/PO ═ 40/60, weight average molecular weight 2800)

Comparative example 4: polyoxyethylene monocetyl ether (EO (2), weight average molecular weight 330)

Comparative example 5: polyoxyethylene laurylamine (EO (10), weight average molecular weight 625)

Comparative example 6: polyoxyethylene polyoxypropylene monostearyl ether (EO (7.2), PO (7.2), EO/PO ═ 50/50, weight average molecular weight 1000)

Comparative example 7: polyoxyethylene polyoxypropylene Mono 2-ethylhexyl Ether (EO (7.7), PO (14.3), EO/PO ═ 35/65, weight average molecular weight 1300)

[ Table 1]

*: difference from blank

As shown in Table 1, in examples 1-1 to 1-4, both the pulp concentration and the whiteness were improved as compared with those in comparative examples 1 to 7.

(example 2)

The oven dry pulp concentration and whiteness after washing were measured in the same manner as in example 1 except that unbleached pulp (softwood kraft pulp) was used instead of unbleached pulp (hardwood kraft pulp) in example 1 and the chemicals shown in table 2 were used. The results are shown in Table 2.

[ Agents ]

Example 2-1: polyoxyethylene polyoxypropylene Monoisodecyl Ether (EO (9.3), PO (2.3), EO/PO ═ 80/20, weight average molecular weight 700)

Example 2-2: polyoxyethylene polyoxypropylene Monoisodecyl Ether (EO (5.7), PO (8.5), EO/PO ═ 40/60, weight average molecular weight 900)

Examples 2 to 3: polyoxyethylene polyoxypropylene monotridecyl ether (EO (7.1), PO (2.4), EO/PO ═ 75/25, weight average molecular weight 650)

Comparative example 8: polyoxyethylene monoisodecyl ether (EO (7), weight average molecular weight 466)

Comparative example 9: polyoxyethylene polyoxypropylene monotridecyl ether (EO (5.1), PO (2.2), EO/PO ═ 70/30, weight average molecular weight 550)

Comparative example 10: pluronic type surfactants (EO (25.5), PO (29), EO/PO ═ 40/60, weight average molecular weight 2800)

Comparative example 11: polyoxyethylene monocetyl ether (EO (2), weight average molecular weight 330)

Comparative example 12: polyoxyethylene laurylamine (EO (10), weight average molecular weight 625)

Comparative example 13: polyoxyethylene polyoxypropylene monostearyl ether (EO (7.2), PO (7.2), EO/PO ═ 50/50, weight average molecular weight 1000)

Comparative example 14: polyoxyethylene polyoxypropylene Mono 2-ethylhexyl Ether (EO (7.7), PO (14.3), EO/PO ═ 35/65, weight average molecular weight 1300)

[ Table 2]

*: difference from blank

As shown in Table 2, in examples 2-1 to 2-3, both the pulp concentration and the whiteness were improved as compared with comparative examples 8 to 14.