JP2018104877A - Method for producing chemical pulp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a chemical pulp capable of enhancing a yield, and a cooking method.SOLUTION: A method for producing a chemical pulp by subjecting a lignocellulose material to alkali digestion or sulfurous acid digestion, including digesting a lignocellulose material in a medical fluid containing a radical scavenger. Also, the method relates to a method for producing a chemical pulp, including digesting a lignocellulose material in an alkaline solution containing a radical scavenger.SELECTED DRAWING: None

Description

  The present disclosure relates to a method for producing chemical pulp and a method for cooking lignocellulosic material.

Chemical pulps, that is, methods for producing pulp by chemically treating lignocellulosic materials include alkali cooking and sulfurous acid cooking. The alkaline cooking method in the present disclosure includes various methods such as a kraft cooking method, a soda cooking method, a sulfite cooking method, and an organosolv cooking method. Moreover, the sulfurous acid cooking method (sulfurous acid method) in this indication is a general term for various sulfurous acid methods of the alkaline sulfurous acid method, the neutral sulfurous acid method, the acidic sulfurous acid method, and the bisulfite method.
When producing pulp by cooking lignocellulosic materials, hydroanthraquinones such as dihydroanthraquinone and tetrahydroanthraquinone are used as cooking aids in order to improve the pulp yield and increase the cooking speed. (For example, patent document 1). Moreover, polyoxyalkylene alkyl ether carboxylate is known as a deresin for the cooking process (Patent Document 2).

JP-A-54-84001 Japanese Patent Publication No.53-28522

  However, in recent years, the carcinogenicity of anthraquinone has been pointed out. For example, the European Food Safety Authority (EFSA) published an opinion in 2012 that the potential for carcinogenic effects of anthraquinone cannot be ruled out. In response, the German Federal Institute for Risk Assessment (BfR) announced in 2013 that it would exclude anthraquinones from the list of substances approved for use in paper for food packaging, and the use of anthraquinones. In the direction to refrain from. Moreover, even if polyoxyalkylene alkyl ether carboxylate is added, there exists a problem that a pulp yield and pulp quality cannot fully be improved. Furthermore, if the kappa number obtained in the cooking process is high, there is a problem that a large amount of bleaching agent (oxygen, chlorine dioxide, chlorine, hypochlorous acid, hydrogen peroxide, sodium hydroxide, ozone, etc.) is required in the bleaching process. is there.

  Therefore, in place of the conventional method, there is a need for a new cooking aid that can improve the pulp yield and reduce the kappa number.

  In one or a plurality of embodiments, the present disclosure provides a chemical pulp manufacturing method and a cooking method capable of at least one of improving yield and reducing kappa number.

  In one aspect, the present disclosure provides a method for producing a chemical pulp by alkaline or sulfite cooking of a lignocellulose material, the method comprising cooking the lignocellulose material in a chemical solution containing a radical scavenger. About.

  The present disclosure, in one aspect, relates to a method for producing chemical pulp comprising digesting a lignocellulosic material in an alkaline solution containing a radical scavenger.

  In one aspect, the present disclosure relates to a method for cooking an lignocellulosic material in an alkali or sulfite manner, the method comprising cooking the lignocellulosic material in a chemical solution containing a radical scavenger.

  According to the present disclosure, in one or a plurality of embodiments, it is possible to provide a chemical pulp manufacturing method and a cooking method capable of at least one of improving yield and reducing kappa number.

These are block diagrams which show an example of the flow of a chemical pulp manufacturing system.

  The present disclosure is based on the finding that cooking in the presence of a radical scavenger can promote delignification, improve the yield and / or reduce the kappa number.

The reason why the above effect is achieved by cooking in the presence of a radical scavenger is not clear, but is estimated as follows.
That is, free or fragmented lignin, cellulose, etc. by digesting the lignocellulose material in the presence of a radical scavenger such as N, N′-di-sec-butyl-1,4-phenylenediamine (PDA) Hydrogen or the radical scavenger itself reacts with the radical derived from it. By this reaction, the radical coupling reaction between lignins and the radical coupling reaction between lignin and cellulose can be suppressed. As a result, it is possible to prevent lignin from repolymerizing and to prevent radical polymerization reaction in the lignocellulose material. By these, delignification can be accelerated | stimulated and it is thought that a refinement | purification yield (pulp yield) can be improved rather than before by suppressing the lignocellulose conversion of a cellulose. In the present disclosure, “selection yield (pulp yield)” refers to the dry weight of pulp (selected pulp) after removing undigested fibers such as knot koji from unbleached pulp after cooking. This is the percentage of the total dry weight of the raw material (lignocellulosic material). However, the present disclosure is not limited to these mechanisms.

  In the present disclosure, “chemical pulp” refers to pulp obtained by chemically treating a lignocellulosic material and delignifying it. Examples of the chemical pulp include sulfite pulp, dissolved sulfite pulp, alkali pulp, kraft pulp, and dissolved kraft pulp in one or more embodiments.

  As a method for producing chemical pulp, there is an alkali cooking method or a sulfite cooking method. As an alkali cooking method, in one or a plurality of embodiments, a strong alkaline aqueous solution such as a sodium hydroxide aqueous solution or a mixed solution of sodium hydroxide and sodium sulfide is used as a cooking chemical solution, for example, a cellulose raw material at 140 to 180 ° C. The method of digesting and obtaining pulp is mentioned. Examples of the alkali cooking method include various methods such as a kraft cooking method, a soda cooking method, a sulfite cooking method, and an organosolv cooking method in one or a plurality of embodiments. Moreover, as a sulfurous acid cooking method, in one or some embodiment, the various sulfurous acid methods of an alkaline sulfurous acid method, a neutral sulfurous acid method, an acidic sulfurous acid method, or a bisulfite method are mentioned.

In the present disclosure, “digestion” means that a lignocellulosic material such as wood or non-wood is treated with a chemical at a high temperature and high pressure, and non-fibrous substances such as lignin are dissolved or removed from the lignocellulosic material to dissolve cellulose or the like. This refers to separating fibrin. The cooking in the present disclosure includes an alkali cooking method or a sulfite cooking method. In one or a plurality of embodiments, the cooking can be performed by heating the lignocellulosic material and an alkaline solution (a cooking solution) containing a radical scavenger in a kettle. “Digestion” in the present disclosure includes not only cooking at high temperature and high pressure using a digester for pulping (pulping) but also oxygen cooking for delignification (for example, an oxygen cooking apparatus in an oxygen delignification step ( Cooking) performed in an O ₂ reactor). The high temperature treatment in the present disclosure includes heating to 80 ° C. or higher in one or more embodiments. In one or a plurality of embodiments, cooking in the production method of the present disclosure includes heating so that the temperature of the chemical solution containing the radical scavenger or the alkaline solution is 80 ° C to 200 ° C. In one or a plurality of embodiments, the high-pressure treatment in the present disclosure includes pressurizing to 0.2 MPa or more, preferably 0.3 MPa or more or 1.0 MPa or more, or 3.0 MPa or less, Preferably it is 2.0 MPa or less.

  In the present disclosure, the “lignocellulose material” may be various kinds of wood such as wood chips, or may be non-wood such as straw. In one or a plurality of embodiments, the wood includes a softwood (N material) chip and a hardwood (L material) chip. Examples of coniferous trees include larch, red pine, and cedar in one or more embodiments. Examples of hardwood include eucalyptus and acacia in one or more embodiments. In one or a plurality of embodiments, the lignocellulose material may be a single type of lignocellulosic material or a mixture of two or more types of lignocellulose material. The lignocellulosic material in the present disclosure may include not only the above wood chips and the like, but also pulp slurry (for example, unbleached or unbleached pulp) discharged in a digester (a cooking step).

  In the present disclosure, the “radical scavenger” refers to a compound that can bind to or bind to a radical species generated during cooking, or a compound that can suppress or suppress a polymerization reaction caused by the generated radical species. The radical scavenger of this indication can also be called a free radical scavenger in one or some embodiment.

  Examples of the radical scavenger include an amine radical scavenger, a tetramethylpiperidineoxyl radical scavenger, a phenol radical scavenger, or a quinone radical scavenger in one or more embodiments.

  As an amine radical scavenger, in one or a plurality of embodiments, N, N′-di-sec-butyl-1,4-phenylenediamine (PDA), N, N′-bis (1,4-dimethylpentyl) is used. ) -1,4-phenylenediamine, N- (1,4-dimethylpentyl) -N′-phenyl-1,4-phenylenediamine, N-phenyl-N ′-(1,3-dimethylbutyl) -1, 4-Ferylenediamine, N-phenyl-N′-isopropyl-1,4-phenylenediamine, N, N′-di-phenyl-1,4-phenylenediamine or N, N′-di-2-naphthyl-1 Phenylenediamine radical scavengers such as 1,4-phenylenediamine, hydroxylamine radicals such as N, N-diethylhydroxylamine (DEHA) or N, N-dimethylhydroxylamine Examples include cal scavengers, tributylamine, diphenylamine, phenothiazine, or phenyl-α-naphthylamine.

  In one or a plurality of embodiments, the tetramethylpiperidineoxyl-based radical scavenger is 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (H-TEMPO), 2,2,6, 6-tetramethylpiperidine-1-oxyl, 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-cyano-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-Benzoxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-oxo-2,2,6, 6-tetramethylpiperidine-1-oxyl, 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxyl, or bis- (2,2,6,6-te La-1-oxyl) - sebacate, and the like.

  In one or a plurality of embodiments, the phenol-based radical scavenger is 2-methylphenol, 2-ethylphenol, 2-propylphenol, 2-methoxyphenol, 2,4-dimethylphenol, 2,6-dimethylphenol, Examples include 2,6-dimethoxyphenol, 2-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-methylphenol, and 4-tertiarybutylcatechol.

  Examples of the quinone radical scavenger include hydroquinone, benzoquinone, methoquinone, ethyl hydroquinone, propyl hydroquinone, butyl hydroquinone, pentyl hydroquinone, hexyl hydroquinone, tertiary butyl hydroquinone, hydroxy hydroquinone, and naphthoquinone in one or more embodiments. It is done.

[Method for producing chemical pulp]
In one aspect, the present disclosure relates to a method for producing chemical pulp (a manufacturing method of the present disclosure). In one aspect, the production method of the present disclosure is a method for producing a chemical pulp by alkaline or sulfite cooking of a lignocellulosic material, wherein the lignocellulosic material is cooked in a chemical solution containing a radical scavenger. including. Moreover, the manufacturing method of this indication is related with the manufacturing method of the chemical pulp which includes digesting in the alkaline solution containing a radical scavenger in one aspect | mode.

  In one or a plurality of embodiments, the chemical solution containing the radical scavenger is a chemical solution used in a cooking step in the production of chemical pulp such as sulfite pulp, dissolved sulfite pulp, soda pulp, kraft pulp, and dissolved kraft pulp ( Cooking fluid), and chemicals used in the oxygen delignification step.

  As a chemical | medical solution containing a radical scavenger, the alkaline solution containing a radical scavenger is mentioned in one or some embodiment.

Examples of the alkaline solution containing the radical scavenger include cooking liquor used for alkaline cooking in one or a plurality of embodiments. In one or more embodiments, a chemical solution or an alkaline solution (digestion solution) containing a radical scavenger used in the production method of the present disclosure is a radical scavenger, sodium sulfide (Na ₂ S), sodium hydroxide ( NaOH), preferably sodium sulfide and sodium hydroxide as main components, and a radical scavenger as a cooking aid. In one or a plurality of embodiments, the degree of sulfidation in a chemical solution containing a radical scavenger or an alkaline solution (cooking solution) is 10% to 35%, preferably 27% to 30%. In one or a plurality of embodiments, the alkali addition amount (active alkali addition rate (AA)) is 5% to 35%, preferably 13% to 30%. The degree of sulfidation is represented by (Na ₂ S) / (NaOH + Na ₂ S) × 100. The active alkali is expressed in terms of NaOH + Na ₂ S.

  In one or more embodiments, the chemical solution and the alkaline solution containing the radical scavenger used in the production method of the present disclosure are substantially free of an organic solvent. In one or more embodiments, the organic solvent concentration in the chemical solution or the alkaline solution is 5 wt% or less, 4 wt% or less, 3 wt% or less, 2 wt% or less. 1% by weight or less, 0.5% by weight or less, substantially 0% by weight, or 0% by weight.

  Examples of the alkaline solution containing the radical scavenger include a chemical solution (treatment solution) used in the oxygen delignification step in one or a plurality of embodiments. In one or a plurality of embodiments, the alkaline solution containing the radical scavenger used in the production method of the present disclosure includes at least a radical scavenger and an alkaline agent such as sodium hydroxide or potassium hydroxide. In one or more embodiments, the pH of the alkaline solution is 11 or more, 12 or more, or 14 or less, or 13.5 or less.

  In one or a plurality of embodiments, a chemical solution containing a radical scavenger used in the production method of the present disclosure (digestion solution) is a sulfite solution containing a radical scavenger, or a hydrogen sulfite solution containing a radical scavenger (bisulfite solution). Solution) and the like.

  In one or a plurality of embodiments, the addition amount of the radical scavenger can be appropriately determined according to the dry weight of the lignocellulosic material used as a raw material. In one or a plurality of embodiments, the addition amount of the radical scavenger is 0.005% by weight to 5% by weight, preferably 0.01% by weight to 4% by weight, based on the dry weight of the lignocellulose material. And more preferably 0.05 wt% to 3 wt%. The addition amount of the radical scavenger in the present disclosure includes, in one or more embodiments, the concentration of the radical scavenger in the treatment liquid in which the digestion of the present disclosure is performed.

  In one or a plurality of embodiments, the production method of the present disclosure may include a step of adding a radical scavenger. If the radical scavenger is added so that the lignocellulosic material can be digested in the chemical solution containing the radical scavenger, the addition site is not particularly limited. In one or a plurality of embodiments, the addition site of the radical scavenger includes at least one point from the raw material chip supply step prior to the cooking step to the cooking step in which the lignocellulosic material is subjected to alkali cooking or sulfite cooking. In one or a plurality of embodiments, the radical scavenger may be added to the digester in which cooking is performed, or any one of the raw material chip supply steps for supplying the raw material chips to the digester from the viewpoint of improving the yield. It is preferable to add to. Examples of the addition location in the raw material chip supply step include a chip bin (13 in FIG. 1), a steaming vessel (14 in FIG. 1), a metal trap, a chip chute, and a high-pressure feeder in one or a plurality of embodiments. Moreover, you may add to the injection circulation line of cooking liquid (white liquor and black liquor). You may add to the oxygen cooking apparatus of the delignification process after cooking with a digester. In one or a plurality of embodiments, the radical scavenger may be added at a time or may be added in divided portions.

In FIG. 1, an example of the flow of the manufacturing method of a chemical pulp is shown. The flow of FIG. 1 includes a raw material chip supply step, a cooking step, and an oxygen delignification step of lignocellulosic material.
(Raw material chip supply process)
Chips 11 of lignocellulosic material chipped by a chipper (not shown) are stored in a chip silo 12. The chip stored in the chip silo 12 is selected by a chip screen (not shown) and sent to the chip bin 13, and then the vapor phase inside the chip is replaced with water vapor in the steaming vessel 14.
(Cooking process)
The chips having enhanced permeability in the steaming vessel 14 are promoted in the permeation tower 15 by introducing the alkaline cooking liquid into the chips. Thereafter, in the digester 16, the pulp containing the black liquor in which the non-fiber components are dissolved and the pulp are mixed by mixing the wood chip as a pulp material with a solution containing sodium hydroxide or the like and steaming under pressure. The slurry is discharged. In some cases, the permeation tower 15 is used as a prehydrolysis tank (PHV) tower for prehydrolysis using acid.
(Oxygen delignification process)
The pulp slurry discharged from the digester 16 is washed by the black liquor washing tower 17, passed through the screen 18, the decker 19, and the unexposed high concentration storage tower 20, and then introduced into the oxygen digester 21. In the oxygen digester 21, further delignification is performed, and then transferred to a bleaching step (not shown).

  The heating temperature at the time of cooking is 80 degreeC-200 degreeC in one or some embodiment, Preferably it is 140 degreeC-180 degreeC. In one or a plurality of embodiments, the production method of the present disclosure includes a cooking step including heating the lignocellulosic material at 80 ° C. to 200 ° C. in a chemical solution that is an alkaline solution containing a radical scavenger.

  In one or a plurality of embodiments, the heating time at the time of cooking is 30 minutes to 400 minutes, preferably 50 minutes to 300 minutes.

  The production method of the present disclosure may include performing a pretreatment of the lignocellulosic material prior to the cooking. Examples of the pretreatment include hydrothermal treatment (prehydrolysis treatment) in one or a plurality of embodiments. In one or a plurality of embodiments, the hydrothermal treatment can be performed by treating the chip-shaped lignocellulose material with hot water or steam.

[Cooking method]
In one aspect, the present disclosure relates to a method of cooking lignocellulosic material in an alkaline or sulfite cooking (a cooking method of the present disclosure). In one aspect, the cooking method of the present disclosure includes cooking the lignocellulose material in a chemical solution containing a radical scavenger. The cooking can be performed in the same manner as the production method of the present disclosure.

[Cooking aid]
In one aspect, the present disclosure relates to a cooking aid for producing chemical pulp, which contains a radical scavenger. Examples of the radical scavenger include those described above.

The present disclosure may relate to one or more of the following embodiments;
[1] A method for producing chemical pulp by subjecting lignocellulosic material to alkali cooking or sulfite cooking,
A production method comprising digesting a lignocellulosic material in a chemical solution containing a radical scavenger.
[2] A method for producing a chemical pulp, comprising digesting a lignocellulosic material in an alkaline solution containing a radical scavenger.
[3] The production method according to [1] or [2], wherein the cooking includes heating the chemical solution containing the radical scavenger or the alkaline solution to a temperature of 80 ° C to 200 ° C.
[4] The production method according to [1] or [2], wherein the cooking temperature is 80 ° C to 200 ° C.
[5] The cooking includes heating the lignocellulosic material at 80 ° C. to 200 ° C. in an alkaline solution containing a radical scavenger and sodium sulfide and / or sodium hydroxide. ] The manufacturing method in any one of.
[6] A method of alkaline liquor or sulfite digestion of lignocellulosic material,
A cooking method comprising cooking the lignocellulosic material in a chemical solution containing a radical scavenger.
[7] The cooking method according to [6], wherein the chemical solution is an alkaline solution containing a radical scavenger.

  Hereinafter, this indication is further explained using an example and a comparative example. However, the present disclosure is not construed as being limited to the following examples.

[Drug]
H-TEMPO (Hydroxy-TEMPO): 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl PDA: N, N′-di-sec-butyl-1,4-phenylenediamine DEHA: N , N-diethylhydroxylamine

[Example 1]
Red pine chips 15 g (absolute dry weight) were packed in a 100 ml metal container. Subsequently, the red pine chips were cooked under the following conditions using the cooking solution to which the radical scavenger shown in Table 1 below was added.
Specifically, kraft pulp cooking liquor having an active alkali of 22% and a sulfidity of 29% prepared from sodium hydroxide and sodium sulfide was added to the chip at a liquid ratio (ratio of the weight of the cooking liquid to the absolute dry weight of the chip: liquid / After adding at chip 4), a radical scavenger was added, followed by cooking at 170 ° C. for 2 hours. About the obtained unbleached pulp, the selection yield and the kappa number were measured according to the following method. The results are shown in Table 1 below. The addition amount of the radical scavenger is the weight percent of the radical scavenger relative to the absolutely dry weight of the chip.
Moreover, the same process and measurement were performed as a blank (BL), without adding a radical scavenger. The results are shown in Table 1.
<Cooking conditions>
Apparatus: Pressure vessel, nitrogen replacement Heating conditions: 170 ° C., 1.4 MPa, 2 hours White liquor (distilled liquor): Alkaline addition amount 22%, Sulfide degree 29%, Liquid ratio 4 (W / W)
Radical scavenger: H-TEMPO, PDA or DEHA 1% by weight

[Selection yield]
The obtained unbleached pulp is put in a cloth bag and thoroughly washed with tap water, and then the uncooked fiber is removed by a flat screen (manufactured by Kumagai Riki Kogyo Co., Ltd.), and the product obtained by dehydration is used as a selected pulp. .
The absolute dry weight of the chips before cooking and the absolute dry weight of the finely selected pulp were measured, respectively, and the number obtained by dividing the latter by the former was expressed in% by weight to obtain the selective yield.

[Copper number]
The kappa number of the selected pulp was measured by the method of JIS P 8211.

  As shown in Table 1, each of Examples 1-1 to 1-3 to which a radical scavenger was added had a lower kappa number and a higher selective yield than the blank. That is, in any radical scavenger, both the selective yield and the kappa number could be improved.

[Example 2]
A test was conducted in the same manner as in Example 1 except that 35 g of red pine chips (absolute dry weight) was used and the cooking process was performed in a 300 ml metal pressure vessel under the following cooking conditions. The results are shown in Table 2 below.
<Cooking conditions>
Equipment: Pressure vessel, no nitrogen replacement (atmosphere)
Heating conditions: 165 ° C., 1.6 MPa, 2 hours White liquor (distilled liquor): Alkaline addition 22%, sulfidity 29%, liquid ratio 4 (W / W)
Radical scavenger: H-TEMPO 0.1 or 0.5% by weight

  As shown in Table 2, in Examples 2-1 and 2-2 to which H-TEMPO was added, the selection yield was improved compared to the blank at any concentration.

[Example 3]
The test was conducted in the same manner as in Example 1 using 18 g of red pine chips (absolute dry weight) and using 0.05 wt% or 0.01 wt% PDA as a radical scavenger. The results are shown in Table 3 below.
<Cooking conditions>
Apparatus: Pressure vessel, nitrogen substitution Heating conditions: 170 ° C., 1.4 MPa, 2 hours White liquor (distilled liquor): Alkaline addition amount 22%, Sulfide degree 29%, Liquid ratio 4 (W / W)
Radical scavenger: 0.01% or 0.05% by weight of PDA

  As shown in Table 3, in Examples 3-1 and 3-2 to which PDA was added, the kappa number decreased compared to the blank at any concentration.

[Example 4]
A test was conducted in the same manner as in Example 1 except that 40 g (absolute dry weight) of acacia chips was used and the cooking process was performed in a 300 ml metal pressure vessel under the following cooking conditions. The results are shown in Table 4 below.
<Cooking conditions>
Equipment: Pressure vessel, no nitrogen replacement (atmosphere)
Heating conditions: 165 ° C., 1.6 MPa, 2 hours white liquor (cooking liquid): alkali addition amount 16%, sulfidity 29%, liquid ratio 4 (W / W)
Radical scavenger: H-TEMPO 0.1% by weight

  As shown in Table 4, in Example 4 digested in a chemical solution containing H-TEMPO, the chemical pulp obtained had a lower kappa number and a higher selective yield than the blank. That is, even when the lignocellulosic material is a hardwood (L material), as in the case of a softwood (N material), the selective yield and the kappa number are obtained by digesting in a chemical containing a radical scavenger. Both were improved.

Claims (6)

A method of producing chemical pulp by alkaline or sulfite cooking of lignocellulosic material,
A production method comprising digesting a lignocellulosic material in a chemical solution containing a radical scavenger.   A process for producing a chemical pulp comprising cooking lignocellulosic material in an alkaline solution containing a radical scavenger.   The said digestion is a manufacturing method of Claim 1 or 2 including heating so that the temperature of the chemical | medical solution containing the said radical scavenger or the said alkaline solution may be set to 80 to 200 degreeC.   4. The cooking according to claim 1, wherein the cooking comprises heating the lignocellulosic material at 80 ° C. to 200 ° C. in an alkaline solution containing a radical scavenger and sodium sulfide and / or sodium hydroxide. The manufacturing method as described in. A method of alkaline liquor or sulfite digestion of lignocellulosic material comprising:
A cooking method comprising cooking the lignocellulosic material in a chemical solution containing a radical scavenger.   The cooking method according to claim 5, wherein the chemical solution is an alkaline solution containing a radical scavenger.