JP5475469B2 - Production method of kraft pulp using detergent for kraft pulp - Google Patents

Description

  The present invention relates to a detergent for kraft pulp and a method for producing kraft pulp using the detergent.

Kraft pulp is generally produced through a cooking process in which wood chips are digested with a mixed solution of caustic soda and sodium sulfide, and a separation process in which black liquor containing lignin is separated from the pulp slurry produced in the cooking process.
In the latest kraft pulp manufacturing equipment, an oxygen delignification reaction step in which oxygen is allowed to act under alkaline and high temperature pressurization is performed after the separation step for the purpose of reducing the drainage load. After this oxygen delignification reaction step, unbleached pulp (unbleached kraft pulp) is produced by washing the pulp, and this unbleached pulp is used for cardboard (boardboard), etc. Is bleached to produce a bleached pulp with improved whiteness, and this bleached pulp is used for fine paper.
Bleaching is performed by multistage bleaching (multistage bleaching). In this multistage bleaching, chlorine dioxide, hydrogen peroxide and the like are generally used as bleaching agents. Further, as a method for increasing the bleaching efficiency, a method of adding a bleaching assistant to the bleaching process has been proposed. For example, a polyhydric alcohol, a polyhydric phenol, or an alkylene oxide adduct thereof and an aliphatic monohydric alcohol are proposed. A method using an etherified product as a bleaching assistant (see Patent Document 1), a method using a bleaching assistant comprising a combination of a specific water-soluble polymer and / or peroxide and a nonionic surfactant (Patent Document) 2)) and the like have been proposed.
However, when chlorine dioxide is used as a bleaching agent, the organic chlorine compounds contained in the bleaching effluent can be a source of pollution to the environment, so the problem is that the bleaching effluent must be treated with activated sludge, and bleaching agents such as chlorine dioxide. Since there are problems such as an increase in manufacturing cost due to a price increase, there is a demand for reduction of the amount used.
Moreover, as a pulp washing method, a pulp washing method (Patent Document 3) in which a polyoxyethylene alkylphenyl ether surfactant is added to various washing steps of a pulp production method, and a surfactant is added to the washing step after the cooking step. A pulp cleaning method (Patent Document 4) has been proposed.

JP-A-5-186987 JP 2002-180391 A JP-A-5-302284 JP 2005-336620 A

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, the present invention can improve the washing efficiency of the pulp and the energy efficiency in the pulp production. In particular, when bleaching the pulp with a bleaching agent after the oxygen delignification reaction step, the pulp after the oxygen delignification reaction step A cleaning agent for kraft pulp that can improve whiteness, can reduce the amount of bleaching agent added, prevents foaming, and can reduce the amount of antifoaming agent used, and the cleaning agent It aims at providing the kraft pulp manufacturing method.

Means for solving the problems are as follows. That is,
<1> A cleaning agent used for cleaning the pulp raw material after decomposing the lignin component contained in the digested pulp raw material using oxygen, and the following general formulas (1), (2) and ( 3) a nonionic surfactant comprising at least one selected from the compounds represented by 3), which contains a nonionic surfactant having a lower cloud point than the washing temperature in washing the pulp raw material. Is a cleaning agent for kraft pulp.
^{_{R 1 O- (PO) n -}} [(EO) m · (PO) k] H ··· formula (1)
In the general formula (1), R ¹ represents either a linear or branched alkyl and alkenyl groups having 10 to 20 carbon atoms. n, m, and k represent an average added mole number, n represents 0-10, and the sum of m and k is 1-100. EO and PO represent an ethylene oxide unit and a propylene oxide unit, respectively, and the addition form of EO and PO in [(EO) _m · (PO) _k ] may be either random or block.
^{_{R 2 -CO- (AO) y -OR}} 3 ··· general formula (2)
However, In the general formula (2), ^{R 2} represents either a linear alkyl group and alkenyl group, having 10 to 20 carbon atoms. AO represents at least one oxyalkylene group selected from an oxyethylene group, an oxypropylene group, and an oxybutylene group. y represents 1-10. R ³ is a methyl group.
However, In the general formula (3), ^{R 4} represents an alkyl group having 10 to 20 carbon atoms. EO represents an ethylene oxide group. x and z both represent the added mole number of ethylene oxide, and the sum of x and z is 2-10.
In the cleaning agent for kraft pulp according to <1>, a nonionic surfactant composed of at least one selected from the compounds represented by the following general formulas (1), (2) and (3): And since the nonionic surfactant with a cloud point lower than the washing temperature in the washing | cleaning of the said pulp raw material is contained, the washing | cleaning efficiency of a pulp is improved.
<2> The nonionic surfactant is a cleaning agent for kraft pulp according to the above <1>, which has a cloud point of 55 ° C. or lower.
<3> A cooking step of digesting the pulp raw material, an oxygen delignification reaction step of decomposing the lignin component contained in the digested pulp raw material using oxygen, and the pulp delignification reaction step following the oxygen delignification reaction step. A kraft pulp manufacturing method comprising: a washing step for washing, wherein the washing step comprises at least one selected from the compounds represented by the general formulas (1), (2) and (3) A method for producing kraft pulp, comprising adding a detergent for kraft pulp containing an ionic surfactant and a nonionic surfactant having a lower cloud point than the washing temperature in the washing step. .
^{_{R 1 O- (PO) n -}} [(EO) m · (PO) k] H ··· formula (1)
In the general formula (1), R ¹ represents either a linear or branched alkyl and alkenyl groups having 10 to 20 carbon atoms. n, m, and k represent an average added mole number, n represents 0-10, and the sum of m and k is 1-100. EO and PO represent an ethylene oxide unit and a propylene oxide unit, respectively, and the addition form of EO and PO in [(EO) _m · (PO) _k ] may be either random or block.
^{_{R 2 -CO- (AO) y -OR}} 3 ··· general formula (2)
However, In the general formula (2), ^{R 2} represents either a linear alkyl group and alkenyl group, having 10 to 20 carbon atoms. AO represents at least one oxyalkylene group selected from an oxyethylene group, an oxypropylene group, and an oxybutylene group. y represents 1-10. R ³ is a methyl group.
However, In the general formula (3), ^{R 4} represents an alkyl group having 10 to 20 carbon atoms. EO represents an ethylene oxide group. x and z both represent the added mole number of ethylene oxide, and the sum of x and z is 2-10.
In the method for producing kraft pulp according to <3>, the pulp raw material is cooked in the cooking step. In the oxygen delignification reaction step, the lignin component contained in the digested pulp raw material is decomposed using oxygen. In the washing step, the nonionic surfactant is at least one selected from the compounds represented by the general formulas (1), (2) and (3), and is based on the washing temperature in the washing step. A detergent for kraft pulp containing a nonionic surfactant having a low cloud point is added, and the pulp raw material is washed following the oxygen delignification reaction step. As a result, the cleaning efficiency of the pulp is improved.
<4> The method for producing kraft pulp according to <3>, further including a bleaching step of bleaching the pulp raw material after the washing step.
<5> The nonionic surfactant is a method for producing kraft pulp according to any one of <3> to <4>, wherein a cloud point is 55 ° C. or lower.

  According to the present invention, the conventional problems can be solved, the object can be achieved, and the pulp washing efficiency and the energy efficiency in pulp production can be improved. Kraft pulp washing that can improve the whiteness of the pulp after the oxygen delignification reaction step, thus reducing the amount of bleach added, preventing foaming and reducing the amount of antifoam added And a kraft pulp manufacturing method using the cleaning agent.

FIG. 1 is a schematic view for explaining an example of the method for producing kraft pulp of the present invention. FIG. 2 is a schematic view for explaining another example of the method for producing kraft pulp of the present invention. FIG. 3 is a schematic view for explaining the washing machines A and B in FIG.

(Cleaning agent for kraft pulp)
The cleaning agent for kraft pulp of the present invention is used to clean the pulp raw material after decomposing the lignin component contained in the digested pulp raw material with oxygen, and at least a specific nonionic surfactant is used. And other components as necessary.

<Nonionic surfactant>
The nonionic surfactant used in the present invention is a nonionic surfactant consisting of at least one selected from the compounds represented by the general formulas (1), (2) and (3). And as long as it contains the nonionic surfactant whose cloud point is lower than the washing temperature in the washing | cleaning of the said pulp raw material, there is no restriction | limiting in particular, According to the objective, it can select suitably.
In order to obtain a sufficient effect, the nonionic surfactant preferably has a cloud point of 10 ° C. or lower than the washing temperature, and the washing temperature is usually 65 ° C. to 90 ° C. The cloud point of the nonionic surfactant is preferably 55 ° C. or lower.
In general, when the washing temperature is above the cloud point of the nonionic surfactant, the nonionic surfactant cannot form micelles. In this case, the surface activity is hardly exhibited and the nonionic surfactant component is dispersed in white in the wash water in the form of oil droplets. The present invention is characterized in that a nonionic surfactant is used above its cloud point, that is, at a temperature at which it does not function as a natural surfactant.
Here, the cloud point is a property peculiar to a nonionic surfactant and refers to a temperature at which an aqueous solution becomes cloudy when the temperature of the aqueous solution of the nonionic surfactant is increased. This occurs because nonionic surfactants hydrate due to hydrogen bonds between hydrophilic groups and water molecules, but at temperatures above the cloud point, the hydrogen bonds with water are broken and the degree of hydration decreases. It is a phenomenon. In this invention, it is set as the value measured as follows.
(Method for measuring cloud point of nonionic surfactant)
After preparing a 2% by weight nonionic surfactant aqueous solution at 25 ° C., 80 g of the nonionic surfactant aqueous solution was weighed in a transparent glass container having a capacity of 100 ml equipped with a thermometer and a stirring rod, Gently raise the temperature while stirring at. When the aqueous solution starts to become cloudy, the solution is taken out from the warm bath at a temperature 3 to 5 ° C. higher and allowed to cool. Even when a 2% by weight nonionic surfactant aqueous solution was already prepared at 25 ° C., it was allowed to stand in a constant temperature water bath at 25 ° C. for 1 hour for a transparent glass container having a capacity of 100 ml as described above. After confirming by visual inspection, if cloudiness is still confirmed, the cloud point is set to 25 ° C. or lower.
The nonionic surfactant needs to have a certain hydrophobic group in the molecule other than having a cloud point lower than the washing temperature in washing the pulp raw material, and the hydrophobic group has a carbon number as the hydrophobic group. Alkylene oxide (EO / PO) adducts of higher alcohols having 10 to 20 linear or branched aliphatic hydrocarbon groups, alkylene oxide (EO / PO) adducts of fatty acid alkyl esters, alkylene oxides of aliphatic amines ( EO) adducts can be used.

-Alkylene oxide adducts of higher alcohols-
As the alkylene oxide adduct of the higher alcohol, a compound represented by the following general formula (1) can be used.
^{_{R 1 O- (PO) n -}} [(EO) m · (PO) k] H ··· formula (1)
In the general formula (1), R ¹ represents either a linear or branched alkyl and alkenyl groups having 10 to 20 carbon atoms. n, m, and k represent an average added mole number, n represents 0-10, and the sum of m and k is 1-100. EO and PO represent an ethylene oxide unit and a propylene oxide unit, respectively, and the addition form of EO and PO in [(EO) _m · (PO) _k ] may be either random or block.

In the higher alcohol that forms the alcohol residue represented by R ¹ O in the general formula (1), the carbon number of R ¹ is not particularly limited as long as it is 10 to 20, and is appropriately selected depending on the purpose. Although it can select, 12-18 are preferable at the point which can improve the whiteness improvement effect and the handleability at the time of low temperature more. When the number of carbon atoms is less than 10, the affinity with the colored component is lowered, and the whiteness improvement effect may be lowered. On the other hand, when the number of carbon atoms exceeds 20, the melting point becomes too high, handling properties at low temperatures may be impaired, and the affinity with colored components may be reduced and the whiteness improvement effect may be reduced. is there. Moreover, since the higher fatty acid used as a raw material hardly exists in nature, it is economically disadvantageous.

The higher alcohol that forms the alcohol residue represented by R ¹ O is not particularly limited and may be appropriately selected depending on the intended purpose. Even a synthetic alcohol having a branch has a linear distribution. It may be a natural alcohol having, for example, decyl alcohol, lauryl alcohol, tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, stearyl alcohol, oleyl alcohol, nonadecyl alcohol, eicosyl alcohol, Etc. Among these, lauryl alcohol, tridecyl alcohol, cetyl alcohol, and stearyl alcohol are preferable because they can achieve both an effect of improving whiteness and handling at low temperatures. Moreover, as a higher alcohol, the mixture of the said alcohol can also be used.

The number of moles n of propylene oxide added directly to the higher alcohol residue R ¹ O is not particularly limited as long as it is 0 to 10, and can be appropriately selected according to the purpose. 6 is preferred.

As the total number of carbon atoms of R ¹ and propylene oxide added directly to the higher alcohol, that is, as the lower limit value of the carbon number of the (R ¹ O— (PO) _n —) moiety in the general formula (1) As long as it is 10 or more, there is no particular limitation and it can be appropriately selected according to the purpose. When the carbon number of the (R ¹ O— (PO) _n —) moiety in the general formula (1) is less than the lower limit (less than 10), the hydrophobicity necessary for affinity with the colored component is insufficient. The whiteness improvement effect may be reduced.
On the other hand, the upper limit of the carbon number of the (R ¹ O— (PO) _n —) moiety in the general formula (1) is not particularly limited as long as it is 50 or less, and may be appropriately selected according to the purpose. However, 45 or less is preferable, and 40 or less is more preferable. When the carbon number of the (R ¹ O— (PO) _n —) moiety in the general formula (1) exceeds the upper limit (50), the melting point becomes too high and handling at low temperatures may be impaired. is there.

  The sum of m and k in the general formula (1) is not particularly limited as long as it is 1 to 100, and can be appropriately selected according to the purpose. However, the whiteness improving effect can be further improved. In this respect, 2 to 80 is preferable, and 5 to 60 is more preferable. When the sum of m and k is less than 1, the interaction with the colored component becomes weak, and the whiteness improvement effect may be reduced. On the other hand, if the sum of m and k exceeds 100, the penetration rate into the fiber is slowed, the whiteness improving effect is lowered, and at the same time, the production cost is increased, which may be economically disadvantageous.

The number of carbons of the higher alcohol that forms the alcohol residue such that the nonionic surfactant of the general formula (1) has a cloud point lower than the washing temperature, or (R ¹ O— (PO) _n —) The number of moles added is determined according to the number of carbons in the portion. For example, when the number of carbon atoms in the (R ¹ O— (PO) _n —) moiety is the same, the smaller the added mole number of EO, the lower the cloud point, and the same number of added moles of EO ( As the number of carbon atoms in the R ¹ O— (PO) _n —) portion increases, the cloud point decreases. In addition, the number of carbon atoms in the (R ¹ O— (PO) _n —) moiety in the general formula (1) and the number of added EO atoms in the (— [(EO) _m · (PO) _k ] H) moiety are the same. If present, the cloud point can be lowered as the added mole number of PO in the-[(EO) _m · (PO) _k ] H) portion increases. As described above, the number of carbons of the higher alcohol forming the alcohol residue such that the nonionic surfactant in the general formula (1) has a cloud point lower than the washing temperature in accordance with the washing temperature, The number of added moles m and k of EO and PO is determined according to the number of carbon atoms in the R ¹ O— (PO) _n —) moiety.

  As the compound represented by the general formula (1), when n and k are 0, polyoxyethylene (4EO) decyl ether, polyoxyethylene (5EO) decyl ether, polyoxyethylene (6EO) decyl ether, poly Oxyethylene (7EO) decyl ether, polyoxyethylene (8EO) decyl ether, polyoxyethylene (5EO) secondary alkyl (C12-14) ether, polyoxyethylene (7EO) secondary alkyl (C12- 14) Ether, polyoxyethylene (8EO) secondary alkyl (C12-14) ether, polyoxyethylene (9EO) secondary alkyl (C12-14) ether, polyoxyethylene (3EO) isotridecyl ether, poly Oxyethylene (5EO) isotridecyl ether, polio Siethylene (7EO) isotridecyl ether, polyoxyethylene (9EO) isotridecyl ether, polyoxyethylene (3EO) lauryl ether, polyoxyethylene (4EO) lauryl ether, polyoxyethylene (5EO) lauryl ether, polyoxyethylene (6EO) lauryl ether, polyoxyethylene (7EO) lauryl ether, polyoxyethylene (2EO) cetyl ether, polyoxyethylene (3EO) cetyl ether, polyoxyethylene (5EO) cetyl ether, polyoxyethylene (7EO) cetyl ether , Polyoxyethylene (2EO) stearyl ether, polyoxyethylene (3EO) stearyl ether, polyoxyethylene (5EO) stearyl ether, polyoxyethylene 6EO) stearyl ether, polyoxyethylene (8EO) stearyl ether. These are commercially available products, and as commercial products, Neugen XL-40 manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Neugen XL-50 manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Neugen XL manufactured by Daiichi Kogyo Seiyaku Co., Ltd. -60, Daiichi Kogyo Seiyaku Co., Ltd. Neugen XL-70, Daiichi Kogyo Seiyaku Co., Ltd., Neugen XL-80, Lion Co., Ltd. Leo Coal SC-50, Lion Co., Ltd. Leo Coal SC-80, Lion Co., Ltd. Leo Coal SC-90, Lion Co., Ltd. Leo Coal TD-30, Lion Co., Ltd. Leo Coal TD-50, Lion Co., Ltd. Leo Coal TD-70, Lion Co., Ltd. Leo Coal TD-90 , Lion Corporation Leox CC-30, Lion Corporation Leo CC-40, Lion Corporation Leox CC-50, Lion Corporation Leox CC-60, Lion Corporation Leox CC-70, Nippon Emulsion Corporation EMALEX102, Nippon Emulsion Corporation EMALEX103, Japan Emulsion Corporation Examples include EMALEX 105 manufactured by Nippon Emulsion Co., Ltd. EMALEX 107 manufactured by Nippon Emulsion Co., Ltd. EMALEX 602 manufactured by Japan Emulsion Co., Ltd. EMALEX 603 manufactured by Japan Emulsion Co., Ltd. EMALEX 605 manufactured by Japan Emulsion Co., Ltd.

  As the compound represented by the general formula (1), when n is 0 and k is 1 to 10, polyoxyethylene (7EO) polyoxypropylene (3PO) isotridecyl ether, polyoxyethylene (20EO) poly Oxypropylene (7PO) isotridecyl ether, polyoxyethylene (2EO) polyoxypropylene (1PO) isotridecyl ether, polyoxyethylene (3EO) polyoxypropylene (1PO) isotridecyl ether, polyoxyethylene (5EO) Polyoxypropylene (1PO) isotridecyl ether, polyoxyethylene (9EO) polyoxypropylene (2PO) isotridecyl ether, polyoxyethylene (5EO) polyoxypropylene (3.5PO) secondary alkyl (C12-14) )ether, Reoxyethylene (7EO) polyoxypropylene (4.5PO) secondary alkyl (C12-14) ether, polyoxyethylene (7EO) polyoxypropylene (8.5PO) secondary alkyl (C12-14) ether, And polyoxyethylene (9EO) polyoxypropylene (5PO) secondary alkyl (C12-14) ether. These are commercially available products. Examples of commercially available products include Lion Co., Ltd. Lionol TD-730, Lion Co., Ltd. Lionol TD-2007, Lion Co., Ltd. Lionol TDL-20, Lion Co., Ltd. TDL-30, Lion Corp. Lionol TDL-50, Lion Corp. Lionol TDM-90, Lion Corp. Lionol L-535, Lion Corp. Lionol L-745, Lion Corp. Lionol L-785, Lion Examples include Lionol L-950 manufactured by Co., Ltd.

  The cloud point of the compound represented by the general formula (1) needs to be lower than the washing temperature, and in order to obtain a sufficient effect, the cloud point needs to be 10 ° C. or more lower than the washing temperature. is there. When the cloud point is higher than the washing temperature, it becomes difficult to separate the colored substance (lignin degradation product) and the pulp to be washed with the washing hot water.

-Alkylene oxide adducts of fatty acid alkyl esters-
As the alkylene oxide adduct of the fatty acid alkyl ester, a compound represented by the following general formula (2) can be used.
_{^{R 2 -CO- (AO) y -OR}} 3 ··· general formula (2)
However, In the general formula (2), ^{R 2} represents either a linear alkyl group and alkenyl group, having 10 to 20 carbon atoms. AO represents at least one oxyalkylene group selected from an oxyethylene group, an oxypropylene group, and an oxybutylene group. y represents 1-10. R ³ is a methyl group.

(R ² —CO—) in the general formula (2) is a fatty acid ester residue. The number of carbon atoms of the fatty acid ester residue is not particularly limited as long as it is 10 to 20, and can be appropriately selected according to the purpose, but 12 to 18 is preferable. When the number of carbon atoms is less than 10, the affinity with the colored component is lowered, and the whiteness improvement effect may be lowered. On the other hand, when the number of carbon atoms exceeds 20, the melting point becomes too high, and handling properties at low temperatures may be impaired.

  The fatty acid ester is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include methyl caprate, methyl laurate, methyl myristate, methyl palmitate, methyl stearate, and methyl oleate. Can be mentioned.

The addition mole number y of the polyoxyalkylene group in the general formula (2) is not particularly limited as long as it is 1 to 10, and can be appropriately selected according to the purpose, depending on the alkyl chain length of the fatty acid ester. Thus, it is determined to have a cloud point lower than the washing temperature. For example, when the polyoxyalkylene group is a polyoxyethylene group, in order to make the cloud point 55 ° C. or lower, when R ² is a lauric acid ester, y is 1 to 9, and R ² is In the case of oleic acid ester, y is 1-10.

-Alkylene oxide adducts of aliphatic amines-
As the alkylene oxide adduct of the aliphatic amine, a compound represented by the following general formula (3) can be used.
However, In the general formula (3), ^{R 4} represents an alkyl group having 10 to 20 carbon atoms. EO represents an ethylene oxide group. x and z both represent the added mole number of ethylene oxide, and the sum of x and z is 2-10.

R ⁴ in the general formula (3) is not particularly limited as long as it is an alkyl group having 10 to 20 carbon atoms, and can be appropriately selected according to the purpose, but 12 to 18 is preferable. When the number of carbon atoms is less than 10, the affinity with the colored component is lowered, and the whiteness improvement effect may be lowered. On the other hand, when the number of carbon atoms exceeds 20, the melting point becomes too high, and handling properties at low temperatures may be impaired.

  The added mole number x + z of the polyoxyethylene group in the general formula (3) is not particularly limited as long as it is 1 to 10, and can be appropriately selected according to the purpose. According to the alkyl chain length, X + z is determined to have a cloud point below the washing temperature.

  There is no restriction | limiting in particular as a compound represented by the said General formula (3), According to the objective, it can select suitably, For example, polyoxyethylene (EO addition number: 2-10) oleylamine (made by Lion Corporation) , Esomin O / 12, O / 17, O / 20), polyoxyethylene (EO addition number: 2 to 10), C12-14 amine (manufactured by Lion Corporation, Esomin C / 12, O / 15), and the like. It is done.

-Other ingredients-
As other components, other process additives such as an antifoaming agent, a pitch control agent, and a scale control agent may be added as long as the effects of the present invention are not impaired.

-Draft form of detergent for kraft pulp-
The dosage form of the cleaning agent for kraft pulp of the present invention is not particularly limited as long as it is a liquid, and can be appropriately selected according to the purpose. Even if a nonionic surfactant is added directly, Or may be diluted with water and added.

-Amount of active ingredient in detergent for kraft pulp-
The detergent for kraft pulp of the present invention is not particularly limited as long as it contains the nonionic surfactant, and can be appropriately selected according to the purpose, but the handling property can be further improved. It is preferable to contain water at the point which can do. When water is contained, it depends on the number of moles added such as ethylene oxide, but the water content may be gelled in the region where the water content is 30% to 70% by mass. It is preferable to do. As water content, 1 mass%-20 mass% are preferable, and 5 mass%-15 mass% are more preferable.

-Amount of kraft pulp detergent used-
There is no restriction | limiting in particular as the usage-amount of the cleaning agent for kraft pulp of this invention, According to the objective, it can select suitably, It is per dry-dry pulp as a compound represented by the said General formula (1)-(3) 0.003 mass%-10 mass% are preferable, 0.005 mass%-1 mass% are more preferable, 0.01-0.1 mass% is still more preferable. If the amount used is less than 0.003% by mass, the desired whiteness improvement effect may not be obtained. If the amount used exceeds 10% by mass, the foaming property is increased or the whiteness is commensurate with the amount added. The improvement effect may not be recognized, and it may be economically disadvantageous.

  According to the cleaning agent for kraft pulp of the present invention, the whiteness of the pulp can be improved. In particular, when the kraft pulp manufacturing method includes a bleaching step, the whiteness of the pulp before bleaching is improved, and chlorine dioxide. The amount used can be reduced, foaming can be prevented, and the amount of antifoaming agent added can be reduced. The reason why this effect is obtained is not clear, but by using a nonionic surfactant having a cloud point lower than the washing temperature in the washing step, a colored substance on the pulp surface is added to the active agent layer phase-separated by the cloud point. Solubilized and repeated washing and dewatering of the pulp in a multi-stage washing process removes colored substances on the pulp surface, improves whiteness, and contributes to a reduction in the amount of chemicals used in the bleaching process . Therefore, the nonionic surfactant is required to have not only a cloud point but also an appropriate hydrophobic chain in the structure.

(Craft pulp production method)
The method for producing kraft pulp of the present invention includes at least a cooking step, an oxygen delignification reaction step, and a washing step, and further includes other steps appropriately selected as necessary.
In the washing step, the nonionic surfactant is at least one selected from the compounds represented by the general formulas (1), (2) and (3), and is based on the washing temperature in the washing step. A detergent for kraft pulp containing a nonionic surfactant having a low cloud point is added.
In order to obtain a sufficient effect, the nonionic surfactant preferably has a cloud point of 10 ° C. or lower than the washing temperature, and the washing temperature is usually 65 ° C. to 90 ° C. The cloud point of the nonionic surfactant is preferably 55 ° C. or lower.

<Cooking process>
The cooking step is a step of cooking the pulp raw material. In the cooking step, for example, a pulp raw material (wood chip) is pressure-cooked in a mixed solution of sodium hydroxide and sodium sulfide, and non-fiber parts such as lignin component, fatty acid sodium salt, and rosin acid sodium salt in the pulp raw material are present. Dissolved. After the alkali cooking, it is separated into pulp slurry and black liquor and washed.

<Oxygen delignification reaction process>
The oxygen delignification reaction step is a step of decomposing the lignin component contained in the digested pulp raw material using oxygen, that is, a step of decomposing a lignin component that could not be removed in the cooking step. Later, the oxygen delignification method in which oxygen is allowed to act under alkaline and high-temperature pressurization was developed and is now widely used. If only 40% to 50% of the lignin remaining in the pulp after the cooking process is decomposed by carrying out the oxygen delignification reaction, it is only possible to reduce the amount of chlorine bleaching chemicals used in the subsequent stage. In addition, the wastewater generated in the oxygen delignification reaction step can be circulated to the cooking step, so that chemicals and energy can be recovered and the wastewater load can be reduced.

<Washing process>
The washing step is a step of washing the pulp raw material after the oxygen delignification reaction step, that is, a step of removing lignin decomposition products and colored components generated by the oxygen delignification reaction by washing.
When the bleaching process described later is performed, the washing process is performed between the oxygen delignification reaction process and the bleaching process.
The washing of the pulp raw material is performed, for example, by adding washing water to the pulp slurry (pulp concentration is about 10% by mass) sent from the cooking step to make a slurry having a pulp concentration of about 1% by mass. Is called.
The washing step is generally performed by a countercurrent multi-stage washing method.
The counter-flow multi-stage cleaning method is a method of cleaning by connecting 2 to 5 cleaning machines in series. Fresh water (hot water recovered from the boiler = washing hot water) is used only for the washing liquid in the final stage washing machine. Wash water collected by the last-stage washing machine is used as washing water by the previous-stage washing machine, and further washing water used by the previous-stage washing machine is collected and used as washing water for the previous-stage washing machine. . When such a countercurrent washing method is used, not only the chemicals used in the cooking step and the oxygen delignification reaction step, but also lignin degradation products can be recovered at a high concentration.
The temperature of the pulp slurry introduced into the washing machine, that is, the washing temperature is usually 65 ° C. to 90 ° C., which is the temperature of the pulp slurry in the vat of the washing machine.

There is no restriction | limiting in particular as said washing machine, According to the objective, it can select suitably, For example, a drum type filter, a diffuser, a pressure type diffuser, a pressure type drum filter, a press type washer, etc. are mentioned. The washing step is preferably a multi-stage washing step in which a plurality of these washing machines are combined.
In order to remove the added kraft pulp cleaning agent, the cleaning step for adding the kraft pulp cleaning agent is followed by a multi-stage cleaning step having at least one rinsing cleaning step, more preferably two or more rinsing cleaning steps. Is desirable. When the washing machine is used alone, the added kraft pulp detergent may not be sufficiently removed, and the whiteness may not be sufficiently improved due to redeposition of coloring components.
In order to improve the cleaning effect, it is preferable to use a multi-stage cleaning machine having two or more stages and add the cleaning agent for kraft pulp to the first-stage cleaning machine immediately after the oxygen delignification reaction step.
The addition position of the detergent for kraft pulp in the washing machine is not particularly limited as long as it is a place where it can be uniformly mixed with the pulp slurry after the oxygen delignification reaction step before being processed in the washing machine, depending on the purpose. The suction port of the pump for feeding the pulp slurry to the washing machine, the inlet of the dilution water for adjusting the concentration of the pulp slurry, the suction port of the dilution water feeding pump, etc. are suitable. is there. Compared to these addition positions, for example, when a kraft pulp cleaning agent is added directly to the bat of a drum-type filter, the kraft pulp cleaning agent does not sufficiently diffuse into the pulp slurry and exhibits a sufficient effect. It may not be done. Moreover, when the cleaning agent for kraft pulp is added to the shower used in the washer, there is a possibility of causing foaming trouble.
The addition of the cleaning agent for kraft pulp of the present invention to the washer is preferably a washer immediately after the oxygen delignification reaction step. For example, after the oxygen delignification reaction step, in a washing step having a counter-current type two-stage vacuum drum type washing machine, it is preferable to add to the pulp slurry fed to the first stage washing machine. It is thought that this is because the kraft pulp detergent sufficiently takes in the colored components in the pulp by adding to the first stage washer and the removal of the kraft pulp detergent proceeds sufficiently with the second stage washer. . When added to the second stage washing machine, the effect of removing the detergent for kraft pulp may not be sufficiently obtained.

<Other processes>
There is no restriction | limiting in particular as said other process, According to the objective, it can select suitably, For example, a bleaching process etc. are mentioned.

-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 is used.
In recent years, environmental problems have been highlighted and so-called ECF (Elemental Chlorine Free) bleaching method that does not use chlorine or hypochlorite has been adopted as a method for preventing the generation of organic chlorine compounds and chloroform. In place of chlorine, ozone and chlorine dioxide are used, and in place of hypochlorite, hydrogen peroxide and chlorine dioxide are used.

In the kraft pulp manufacturing method of the present invention, for example, as shown in FIG. 1, the pulp slurry 1 is first charged into the oxygen delignification reaction tower 2 to obtain the pulp slurry 3 after the oxygen delignification reaction. The pulp slurry 3 after this oxygen delignification reaction is No. 1 Repulper 4 No. 1 was transferred to the washer. Washed with 1 shower water 6 of washer. This No. Pulp (exit pulp sheet) 9 washed with 1 washer was 2 Repulper 10 No. 2 was transferred to the washer. Washed with 2 washer shower water 12. This No. Pulp (exit pulp sheet) 15 washed with two washers is transferred to a screen. No. The 1-washer filtrate 7 is no. No. 1 washer filtrate tank 8 and no. Used as No. 1 repulper dilution water 5, The 2 washer filtrate 13 was No. It was transferred to the filtrate tank 14 of 2 washer. No. 1 shower water 6 to No. 1 Used as 2 repulper dilution water 11.
For example, in the case of the washing machine of FIG. 1, the position for adding the detergent for kraft pulp can be uniformly mixed and supplied to the inlet of the first stage washing machine (pulp after the oxygen delignification reaction). It is preferable to add to the slurry 3, No. 1 repulper 4 or No. 1 repulper dilution water 5).

Moreover, the kraft pulp manufacturing method of the present invention includes, for example, a cooking step, an oxygen delignification reaction step performed by an O ₂ TW (oxygen delignification reaction tower) shown in FIG. It includes a washing process performed by a washer (washing machines A and B in FIG. 2) and a multi-stage bleaching process.
FIG. 3 is a schematic view for explaining the washing machines A and B in FIG. The kraft pulp cleaning agent of the present invention is preferably added to the supply pipe for the filtrate for dilution (a) and pulp (b) in the cleaning machine schematic diagram of FIG. When added to the vat (c) or shower washing (d), mixing may be insufficient and the effect may not be sufficiently obtained, and foaming may occur in the washing machine. According to the method for producing kraft pulp shown in FIGS. 2 and 3, the washing efficiency of the pulp can be improved. In particular, when bleaching the pulp, the whiteness of the pulp after the oxygen delignification reaction step is improved. Therefore, the amount of bleaching agent added can be reduced, foaming can be prevented, and the amount of antifoaming agent added can be reduced.

  In the case of cardboard manufacture, the kraft pulp manufacturing method does not include the bleaching step, and thus does not have the effect of reducing the amount of chlorine used. However, when the cleaning efficiency is increased, it is used to obtain the same cleaning effect. When the amount of hot water to be used can be reduced and the amount of hot water to be used can be reduced, the amount of black liquor generated can be suppressed, and the load on the recovery boiler can be reduced. Furthermore, if it is a situation where production can be increased, the amount of pulp that can be treated with the same amount of hot water can be increased, and productivity can be improved.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Examples 1-10 and Comparative Examples 1-7)
1 of the multistage filter washing process after the oxygen delignification reaction process of the cellulose pulp manufacturing apparatus comprising the cooking process, the oxygen delignification reaction process, the multistage filter washing process, and the multistage bleaching process with chlorine dioxide and hydrogen peroxide. Hardwood cellulose pulp before the multistage bleaching process was collected from the washer at the stage. Next, 5.6 g as a dry weight of the collected cellulose pulp was weighed into a 500 mL beaker, 65 ° C. warm water was added so that the pulp concentration was 1% by mass, and then EO of various higher alcohols shown in Table 1. 1% by weight of a kraft pulp cleaning agent comprising a PO adduct is added in a solid content to the pulp, and 10% by weight sodium hydroxide is added to the pulp to a solid content of 4% by weight. The pulp slurry was prepared by stirring for 10 minutes while maintaining the temperature. The prepared pulp slurry was immediately subjected to suction filtration using a Kiriyama funnel (diameter: 95 mm) to make paper. During paper making, the pulp slurry was divided so as to have a basis weight of 250 g / m ² to prepare a total of three evaluation sheets. The paper for evaluation was pressed and then dried by ventilation for about 24 hours to obtain a sample for measuring whiteness.
For comparison, when Comparative Example 1 was not added with a cleaning agent, Comparative Example 6 was compared with Comparative Example 7 when Nonylphenol EO12 molar adduct (Lion Corporation's Liponox NC120) was used as a cleaning agent. Indicates a case where sodium dodecylbenzenesulfonate (Lypon LS-250, manufactured by Lion Corporation), which is an anionic surfactant, is used as a cleaning agent.
In Table 1, compounds 1 to 6 were synthesized according to Production Examples 1 and 2 below.

(Production Example 1)
Isotridecyl alcohol [trade name Exxal13, (trade name Exxal13, (for EO, PO, or a mixture of EO and PO] in a stainless steel electromagnetic induction rotary stirrer autoclave connected with a thermometer, a nitrogen introducing tube and a decompression tube 394 g of Exxon Mobil Corporation) and 5 g of 40% potassium hydroxide as a catalyst were added, the temperature was raised to 90 ° C. after nitrogen substitution, and dehydration was performed at 0.003 MPa. Thereafter, the temperature was raised to 120 ° C., and under a pressure of 0.5 Mpa or less, 176 g of ethylene oxide (ethylene oxide (EO) manufactured by Mitsubishi Chemical Co., Ltd.) and propylene oxide (manufactured by Asahi Glass Co., Ltd.) 116 g of propylene oxide (PO) (1 mol per 1 mol of alcohol) was uniformly mixed and then introduced and aged for 2 hours to obtain a random adduct. Next, unreacted EO and PO were removed under reduced pressure, and after cooling, neutralization was performed by adding 80% by weight of acetic acid equivalent to the catalyst to obtain the desired random adduct (compound 1).
Compound 2 and Compound 3 shown in Table 1 were synthesized in the same manner as in Production Example 1 so as to have a predetermined added mole number.

(Production Example 2)
108.2 g (0.4 mol) of stearyl alcohol (manufactured by Shin Nippon Rika Co., Ltd., Conol 30S) and 0.278 g of KOH (manufactured by Toa Gosei Co., Ltd., flake caustic potash) as a catalyst, 2 mol of propylene oxide adduct of stearyl alcohol 0.18 wt.%) Was charged in an autoclave, and the reaction system was sufficiently purged with nitrogen, and after sufficient dehydration at 140 ± 5 ° C. for 1 hour under reduced pressure, propylene oxide (manufactured by Asahi Glass Co., Ltd.) Then, 46.4 g (0.8 mol) of propylene oxide (PO) was gradually added so as to maintain 115 ± 5 ° C. and 0.1 to 0.3 MPa (gauge pressure). After completion of the addition, aging was performed for 2 hours, and then unreacted PO was removed under reduced pressure. Subsequently, after cooling, 0.06 g of KOH was added, the inside of the reaction system was sufficiently replaced with nitrogen, and then 387.2 g (8.8 mol) of ethylene oxide (manufactured by Mitsubishi Chemical Corporation, ethylene oxide (EO)) A mixture of 324.8 g (5.6 mol) of propylene oxide was gradually added so as to maintain 120 ± 5 ° C. and 0.1 to 0.3 MPa (gauge pressure). After completion of the addition, aging and removal of unreacted ethylene oxide and propylene oxide were performed, followed by cooling and adjustment to pH = 7 with acetic acid (99% industrial acetic acid, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) (Compound 4) .
Compound 5 and Compound 6 shown in Table 1 were synthesized in the same manner as in Production Example 2 so as to have a predetermined added mole number. In addition, about the compound 6, it supplied to the propylene oxide adduct of stearyl alcohol separately in steps of ethylene oxide and propylene oxide, and added, and it was set as the block adduct.

(Examples 11 and 12)
In Example 11, the detergent synthesized in the following Production Example 3 was used.
(Production Example 3)
It is obtained by calcining alumina hydroxide / magnesium hydroxide (Kyowa Chemical Industry Co., Ltd., Kyoward 300) having a chemical composition of 2.5 MgO.Al ₂ O ₃ .nH ₂ O for 3 hours at 750 ° C. in a nitrogen stream. A calcined alumina / magnesium hydroxide was obtained. 1.2 g of the obtained calcined alumina hydroxide / magnesium catalyst 1.3 g of 5% potassium hydroxide methanol solution and 350 g of methyl laurate were charged into a 4 liter autoclave, and the catalyst was reformed in the autoclave. Next, after the inside of the autoclave was replaced with nitrogen, the temperature was raised, and while maintaining the temperature at 180 ° C. and the pressure at 3 atm, 504 g of ethylene oxide was introduced and reacted while stirring, and the polyoxyethylene methyl ether of lauric acid was reacted. An adduct having an average ethylene oxide addition mole number of 7.0 was obtained. This was used as the cleaning agent of Example 11.

  Moreover, the cleaning agent for kraft pulp of Example 12 is manufactured by Lion Corporation, which is an ethylene oxide adduct (average number of moles added: 2 moles) of an aliphatic primary amine derived from coconut oil fatty acid corresponding to the general formula (3). Esomine C / 12 was used.

  Next, about the obtained Examples 1-12 and Comparative Examples 1-7, the whiteness and the cloud point of a kraft pulp detergent were measured as follows. The results are shown in Table 2.

<Measurement of whiteness>
Using a spectral color / whiteness meter PF-10 (manufactured by Nippon Denshoku Industries Co., Ltd.), the whiteness at three locations was measured for each produced evaluation sheet, and the average value of the three sheets was determined. Among the evaluation results in the table, the whiteness becomes better as the value becomes larger. The whiteness improvement effect (Δ whiteness) was determined from the difference from the whiteness when no nonionic surfactant as a detergent for kraft pulp was added (Comparative Example 1). If the whiteness improvement effect is 1.5% or more under these experimental conditions, it will contribute to the chlorine dioxide reduction effect.

<Measurement of cloud point of detergent for kraft pulp>
After preparing a 2% by weight nonionic surfactant aqueous solution at 25 ° C., 80 g of the nonionic surfactant aqueous solution was weighed into a transparent glass screw cap bottle equipped with a thermometer and a stirring rod. The temperature was raised while stirring in a warm bath, and the aqueous solution was taken out from the warm bath at a temperature 3 to 5 ° C. after the aqueous solution began to become cloudy, allowed to cool, and the temperature at which the turbidity disappeared was measured visually. . If it was already cloudy when a 2% by weight nonionic surfactant aqueous solution was prepared at 25 ° C., it was left in a constant temperature water bath at 25 ° C. for 1 hour for a transparent glass container having a capacity of 100 ml as described above. After confirming the cloudiness by visual inspection, the cloud point was set to 25 ° C. or lower.

(Example 13)
In a kraft pulp factory (coniferous kraft pulp production 350 tons / day), after the cooking process, the enzyme delignification reaction process, and the enzyme delignification reaction process, three vacuum drum washers (first stage: No. 1 washer, A kraft pulp manufacturing method including a washing step for washing pulp using a second stage: No. 2 washer and a third stage: No. 3 washer and a bleaching step was performed as follows.
No. of vacuum drum washer The nonionic surfactant used in Example 8 was added to a pulp concentration adjusting filtrate introduced into one washer (bat temperature (washing temperature): 80 ° C.) so as to be 300 ppm with respect to the pulp.
Next, no. The washed pulp discharged from the 3 washer was collected, and the whiteness was measured as follows. As a result, the pulp was improved by 1.0% compared to when no nonionic surfactant (detergent) was added. .
Moreover, when the amount of chlorine dioxide used in the bleaching step was measured as follows, it was possible to reduce it by 11.0%.

<Whiteness>
An evaluation sheet with a basis weight of 250 g / m ² was prepared using a TAPPI paper machine, and the whiteness was measured according to JIS P8148. The difference (Δ) from the whiteness when no nonionic surfactant (cleaning agent) was added was used as an evaluation index. Normally, the amount of chlorine dioxide added in the bleaching step of chemical pulp is adjusted by continuously sensing the whiteness of the pulp in the slurry, so if the whiteness improvement effect is 0.5% or more, chlorine dioxide. This will contribute to the reduction effect.

<Chlorine dioxide consumption>
The reduction rate of the amount of chlorine dioxide used was calculated by (the amount of chlorine dioxide added when no detergent was added-the amount of chlorine dioxide added when the detergent was added) / the amount of chlorine dioxide added when no detergent was added) × 100. .
Regarding the amount of chlorine dioxide used, in order to eliminate errors due to fluctuations in the delignification degree due to the oxygen delignification reaction, the horizontal axis represents the kappa number (KN number) indicating the degree of delignification after the enzyme delignification reaction, and the vertical axis represents Create a graph with the amount of chlorine dioxide added to obtain the target whiteness of the final pulp after bleaching, and when the delignification degree after the oxygen delignification reaction is the same KN number from this graph The amount of addition of chlorine dioxide was read to determine the amount of addition. This was performed in each case of no addition and addition of a cleaning agent, and the reduction rate of the chlorine dioxide was calculated. The kappa number was measured according to JIS P8211.

( Reference Example 14)
In a kraft pulp manufacturing plant (hardwood kraft pulp production amount of 1050 tons / day), after a cooking process, an enzyme delignification reaction process, and an enzyme delignification reaction process, a vacuum drum washer, a drum-type pressure washer, and press washing A kraft pulp manufacturing method including a washing step of washing using a machine and a bleaching step was performed as follows.
300 ppm of the nonionic surfactant used in Example 8 on the suction side of the filtrate feed pump for adjusting the pulp concentration introduced into the vacuum drum washer (bat temperature (washing temperature): 83 ° C.). It added so that it might become.
Next, in the same manner as in Example 13, the whiteness of the washed pulp collected from the press washer was improved by 1.1% compared to when no nonionic surfactant (detergent) was added, The amount of chlorine dioxide used in the bleaching process was reduced by 5.2%.

(Example 15)
In a kraft pulp factory (coniferous kraft pulp production 300 tons / day), after the cooking process, enzyme delignification reaction process, and enzyme delignification reaction process, two vacuum drum type washers (first stage: No1 washer, second A kraft pulp manufacturing method including a washing step for washing pulp using a No. 2 washer and a bleaching step was performed as follows.
No. of vacuum drum washer The nonionic surfactant used in Example 8 was 300 ppm with respect to the pulp on the suction side of the filtrate feed pump for adjusting the pulp concentration introduced into one washer (bat temperature (washing temperature): 80 ° C.). It added so that it might become.
Next, in the same manner as in Example 13, the vacuum drum washer No. The whiteness of the washed pulp collected from 2 washers is improved by 1.0% compared to when no nonionic surfactant (detergent) is added, and the amount of chlorine dioxide used in the bleaching process is 12.0%. Reduced.

(Example 16)
In a kraft pulp manufacturing plant (coniferous kraft pulp production 300 tons / day), a drum displacer (pressure type multi-stage washer: DD washer) was used after the cooking, enzyme delignification reaction, and enzyme delignification reaction steps. Then, a kraft pulp manufacturing method including a washing step for washing the pulp in two stages and a bleaching step was carried out as follows.
The nonionic surfactant used in Example 8 was added to the pulp introduced into the DD washer (pulp temperature (washing temperature): 80 ° C.) so as to be 300 ppm based on the pulp.
Next, in the same manner as in Example 13, the whiteness of the washed pulp collected from the DD washer outlet is improved by 0.5% compared to when no nonionic surfactant (detergent) was added, The amount of chlorine dioxide used in the bleaching process was reduced by 5.0%.

  The cleaning agent for kraft pulp of the present invention can be suitably used as a cleaning agent used for cleaning kraft pulp used for producing, for example, fine paper and cardboard.

Claims (4)

A cooking process for cooking pulp raw materials;
An oxygen delignification reaction step of decomposing the lignin component contained in the digested pulp raw material using oxygen;
A washing step of washing the pulp raw material subsequent to the oxygen delignification reaction step,
In the washing step, a nonionic surfactant consisting of at least one selected from the compounds represented by the following general formulas (1), (2) and (3), and from the washing temperature in the washing step Add a detergent for kraft pulp containing a nonionic surfactant with low cloud point,
The method for producing kraft pulp, wherein the washing step is a multi-stage washing step in which a plurality of washing machines are combined, and the cleaning agent is added to the first-stage washing machine immediately after the oxygen delignification reaction step.
R ¹ O- (PO) _n -[(EO) _m ・ (PO) _k ] H ... General formula (1)
However, in the general formula (1), R ¹ Represents either a linear or branched alkyl or alkenyl group having 10 to 20 carbon atoms. n, m, and k represent an average added mole number, n represents 0-10, and the sum of m and k is 1-100. EO and PO respectively represent an ethylene oxide unit and a propylene oxide unit, and [(EO) _m ・ (PO) _k ], The addition form of EO and PO may be either random or block.
R ² -CO- (AO) _y -OR ³   ... General formula (2)
However, in the general formula (2), R ² Represents either a linear alkyl group having 10 to 20 carbon atoms or an alkenyl group. AO represents at least one oxyalkylene group selected from an oxyethylene group, an oxypropylene group, and an oxybutylene group. y represents 1-10. R ³ Is a methyl group.
However, in the general formula (3), R ⁴ Represents an alkyl group having 10 to 20 carbon atoms. EO represents an ethylene oxide group. x and z both represent the added mole number of ethylene oxide, and the sum of x and z is 2-10. The method for producing kraft pulp according to claim 1, further comprising a bleaching step of bleaching the pulp raw material after the washing step. The method for producing kraft pulp according to claim 1, wherein the nonionic surfactant has a cloud point of 55 ° C. or less. The addition position of the cleaning agent for kraft pulp is a position where the cleaning agent for kraft pulp can be uniformly mixed and supplied to the inlet of the first-stage cleaning machine in the multi-stage cleaning process. Kraft pulp production method.