JP7165323B2 - Pulp cooking aid and method for producing chemical pulp using the same - Google Patents

Description

The present disclosure relates to pulp cooking aids and methods for making chemical pulp and cooking lignocellulosic materials therewith.

Chemical pulping, that is, methods of chemically treating lignocellulosic material to produce pulp, include alkaline and sulfite cooking methods. Alkaline cooking methods in the present disclosure include a wide variety of kraft cooking methods, soda cooking methods, sulfite cooking methods, organosolv cooking methods, and the like. In addition, the sulfite cooking method (sulfite method) in the present disclosure is a general term for various sulfite methods including the alkaline sulfite method, the neutral sulfite method, the acid sulfite method, and the bisulfite method.
Hydroanthraquinones such as dihydroanthraquinone and tetrahydroanthraquinone are used as cooking aids in the production of pulp by cooking lignocellulosic materials in order to improve the pulp yield and the cooking rate. (For example, Patent Document 1). Also, polyoxyalkylene alkyl ether carboxylate is known as a resin removing agent for the cooking process (Patent Document 2).

JP-A-54-82401 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) issued an opinion in 2012 that anthraquinones cannot be ruled out as carcinogenic. In response, the German Federal Institute for Risk Assessment (BfR) announced in 2013 that anthraquinone would be removed from the list of substances permitted for use in food packaging paper. There is a tendency to refrain from using it.
Moreover, even if polyoxyalkylene alkyl ether carboxylate is added to the cooking liquor, there is a problem that the pulp yield and pulp quality cannot be sufficiently improved. Furthermore, when the kappa number obtained in the cooking process is high, there is a problem that a large amount of bleaching agents (oxygen, chlorine dioxide, chlorine, hypochlorous acid, hydrogen peroxide, sodium hydroxide, ozone, etc.) is required in the bleaching process. be.
Therefore, there is a demand for a new cooking aid capable of improving the pulp yield and lowering the kappa number in place of the conventional methods.

The present disclosure, in one or more embodiments, provides pulp cooking aids, methods of making chemical pulp, and methods of cooking that can increase yield and reduce kappa number.

The present disclosure, in one aspect, relates to a pulp cooking aid containing a radical scavenger and a solvent.

The present disclosure, in one aspect, relates to a method of making chemical pulp comprising alkaline or sulfite cooking a lignocellulosic material in a chemical solution containing a radical scavenger and a solvent.

The present disclosure relates, in one aspect, to a method for alkaline or sulfite cooking of lignocellulosic material comprising cooking the lignocellulosic material in a chemical solution containing a radical scavenger and a solvent.

INDUSTRIAL APPLICABILITY According to the present disclosure, in one or more embodiments, a pulp cooking aid, chemical pulp manufacturing method, and cooking method capable of improving pulp yield and reducing kappa number can be provided.

FIG. 1 is a block diagram showing an example of the flow of a chemical pulp manufacturing system. FIG. 2 shows a photograph of uncooked fibers that were not flat screen screened in Example 1. FIG.

The present disclosure is based on the finding that cooking in the presence of a radical scavenger and a solvent can promote delignification, resulting in higher screen yields and lower kappa numbers.

Although the reason why the above effects are obtained by cooking in the presence of a radical scavenger and a solvent is not clear, it is presumed as follows.
The radical scavenger itself and hydrogen in the cooking liquor react with radicals derived from lignin, cellulose, etc., which are liberated or fragmented by cooking. This reaction can suppress the radical coupling reaction between lignins and the radical coupling reaction between lignin and cellulose, prevent the repolymerization of lignin and the radical polymerization reaction in lignocellulose materials, promote delignification, and promote the formation of cellulose. It is possible to suppress lignocellulose formation, and as a result, the screening yield (pulp yield) is improved more than before. Furthermore, the partial kappa number reduction effect of the solvent can be applied to the entire lignocellulose material by using the radical scavenger together, and the kappa number reduction effect is even better than when the solvent is used alone. can be obtained. As a result, it is considered that both an improvement in screening yield (pulp yield) and a decrease in kappa number can be achieved. However, the present disclosure is not limited to these mechanisms.

In the present disclosure, the “screening yield (pulp yield)” refers to the dry weight of the pulp (screening pulp) after removing uncooked fibers such as knot residue from the unbleached pulp after cooking. (Lignocellulosic material) Refers to the percentage of the total absolute dry weight. In the present disclosure, "absolute dry weight" refers to the weight after drying at 105°C for one day.

In the present disclosure, the “kappa number” refers to the kappa number obtained by testing the above screened pulp according to JIS P 8211 (pulp-kappa number test method).

In the present disclosure, "chemical pulp" is pulp obtained by chemically treating and delignifying lignocellulosic material. Chemical pulps, in one or more embodiments, include sulfite pulp, dissolved sulfite pulp, alkaline pulp, kraft pulp, dissolved kraft pulp, or the like.

Methods for producing chemical pulp include alkali cooking and sulfite cooking. As the alkaline cooking method, in one or more embodiments, a strong alkaline aqueous solution such as an aqueous solution of sodium hydroxide or a mixed solution of sodium hydroxide and sodium sulfide is used as a cooking chemical solution, and in the cooking solution, for example, A method of cooking a cellulose raw material at 140 to 180° C. to obtain a pulp can be mentioned. Alkaline digestion, in one or more embodiments, includes various methods such as kraft digestion, soda digestion, sulfite digestion, or organosolv digestion. In one or more embodiments, the sulfite cooking method includes various sulfite methods such as an alkaline sulfite method, a neutral sulfite method, an acid sulfite method, and a bisulfite method.

In the present disclosure, the term “cooking” means subjecting a wood or non-wood lignocellulose material to a high-temperature, high-pressure treatment using chemicals to dissolve or remove non-fiber materials such as lignin from the lignocellulose material to produce cellulose or the like. Separation of fibrin. Cooking in the present disclosure includes alkaline cooking or sulfite cooking. Cooking, in one or more embodiments, can be carried out by heating the lignocellulosic material and an alkaline solution (cooking liquor) containing a radical scavenger in a kettle. “Cooking” in the present disclosure includes not only cooking under high temperature and high pressure using a digester for fiberization (pulping), but also oxygen cooking for delignification (e.g., oxygen digester in oxygen delignification process ( cooking performed in an _O2 reactor)). High temperature treatment in the present disclosure includes heating to 80° C. or higher in one or more embodiments. Cooking in the present disclosure includes, in one or more embodiments, heating the chemical solution containing the radical scavenger or the alkaline solution to a temperature of 80°C to 200°C. In one or more embodiments, high-pressure treatment in the present disclosure includes applying pressure to 0.2 MPa or more, preferably 0.3 MPa or more, 1.0 MPa or more, or 3.0 MPa or less, It is preferably 2.0 MPa or less.

In the present disclosure, "lignocellulose material" may be various types of wood such as wood chips, or non-wood such as straw. Wood, in one or more embodiments, includes softwood (N material) chips and hardwood (L material) chips. Conifers, in one or more embodiments, include larch, red pine, cedar, and the like. Broadleaf trees, in one or more embodiments, include eucalyptus, acacia, and the like. The lignocellulosic material, in one or more embodiments, may be a single type of lignocellulosic material or a mixture of two or more types of lignocellulosic material. Lignocellulosic materials in the present disclosure can include pulp slurries (eg, unbleached or unbleached pulp, etc.) discharged from the digester (digestion process), as well as the wood chips and the like described above.

[Pulp cooking aid]
The present disclosure, in one aspect, relates to a pulp cooking aid containing a radical scavenger and a solvent (pulp cooking aid of the disclosure). According to the pulp cooking aid of the present disclosure, in one or more embodiments, both improved post-cooking pulp yield and reduced post-cooking kappa number can be achieved. According to the pulp cooking aid of the present disclosure, in one or more embodiments, it is possible to provide a pulp cooking aid that contains a high concentration of a radical scavenger and has excellent long-term storage stability. According to the pulp cooking aid of the present disclosure, in one or more embodiments, the partial kappa number reducing effect of the solvent can be applied to the entire lignocellulosic material by using it in combination with the radical scavenger. Thus, a better kappa number reduction effect can be obtained than when a radical scavenger or solvent is used alone.

The pulp cooking aid of the present disclosure contains a radical scavenger. In the present disclosure, the term “radical scavenger” refers to a compound that binds or can bind to radical species generated during cooking, or a compound that suppresses or can suppress a polymerization reaction caused by the radical species generated. Radical scavengers of the present disclosure can also be referred to as free radical scavengers in one or more embodiments.

As the radical scavenger, in one or more embodiments, nitrogen-based radical scavengers such as tetramethylpiperidineoxyl-based radical scavengers and amine-based radical scavengers, phenol-based radical scavengers, or quinone-based radical scavengers are used. mentioned.

Tetramethylpiperidineoxyl-based radical scavengers include, in one or more embodiments, 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-tetramethylpiperidine-1-oxyl) - Sebacate and the like. As the tetramethylpiperidineoxyl-based radical scavenger, H-TEMPO is preferred in one or more embodiments.

As the amine-based radical scavenger, in one or more embodiments, N,N'-di-sec-butyl-1,4-phenylenediamine (PDA), N,N'-bis(1,4-dimethylpentyl )-1,4-phenylenediamine, N-(1,4-dimethylpentyl)-N′-phenyl-1,4-phenylenediamine, N-phenyl-N′-(1,3-dimethylbutyl)-1, 4-phenylenediamine, N-phenyl-N'-isopropyl-1,4-phenylenediamine, N,N'-di-phenyl-1,4-phenylenediamine or N,N'-di-2-naphthyl-1 ,4-phenylenediamine and other phenylenediamine radical scavengers, N,N-diethylhydroxylamine (DEHA) or N,N-dimethylhydroxylamine and other hydroxylamine radical scavengers, tributylamine, diphenylamine, phenothiazine, or phenyl -α-naphthylamine and the like.

Phenolic radical scavengers include, in one or more embodiments, 2-methylphenol, 2-ethylphenol, 2-propylphenol, 2-methoxyphenol, 2,4-dimethylphenol, 2,6-dimethylphenol, 2,6-dimethoxyphenol, 2-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-methylphenol, 4-tert-butylcatechol (TBC) and the like. As the phenolic radical scavenger, TBC is preferred in one or more embodiments.

In one or more embodiments, the quinone-based radical scavenger includes hydroquinone, benzoquinone, methoquinone, ethylhydroquinone, propylhydroquinone, butylhydroquinone, pentylhydroquinone, hexylhydroquinone, tert-butylhydroquinone, hydroxyhydroquinone, naphthoquinone, and the like. be done.

The pulp cooking aid of the present disclosure contains a solvent. Since the pulp cooking aid of the present disclosure contains a solvent in addition to the radical scavenger, in one or more embodiments, it can be a cooking aid containing a high concentration of the radical scavenger, and A one-liquid formulation having excellent long-term storage stability can be obtained.

Solvents include hydrophilic organic solvents in one or more embodiments. Solvents include, in one or more embodiments, glycol-based solvents, glycol ether-based solvents, alcohol-based solvents, amine/amide-based solvents, and the like. Solvents may be used singly or in combination of two or more in one or more embodiments.

Glycol-based solvents include, in one or more embodiments, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, or polypropylene glycol. As the glycol-based solvent, ethylene glycol or the like is preferable in one or more embodiments.

As the glycol ether solvent, in one or more embodiments, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monophenyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, Diethylene glycol monohexyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether propionate, propylene glycol monobutyl ether, 3-methoxy-3-methyl-1-butanol, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, and the like. As the glycol ether-based solvent, in one or more embodiments, ethylene glycol monophenyl ether, diethylene glycol monobutyl ether, dipropylene glycol monobutyl ether, or the like is preferable.

As alcohol solvents, in one or more embodiments, methanol, ethanol, n-propanol, iso-propanol, n-butanol, tert-butanol, 1,4-butanediol, 1,5-pentanediol, benzyl alcohol , or 2-ethyl-1-hexanol.

As the amine/amide solvent, in one or more embodiments, N,N-dimethylformamide, N-methylpyrrolidone, hexamethylphosphoric acid triamide, 1,3-dipropylimidazolidinone, 1,3-dimethylimidazon lysinone tetramethylurea, N,N-dimethylacetamide dimethylsulfonium, monoethanolamine, diethanolamine, triethanolamine, ditripropanolamine, tripropanolamine, triisopropanolamine and the like.

As the solvent, in one or a plurality of embodiments, a glycol ether solvent and a glycol solvent are preferable because they can improve the pulp yield and produce a pulp with a low kappa number.

The content of the radical scavenger in the cooking aid of the present disclosure is, in one or more embodiments, 1 wt% to 50 wt%, preferably 5 wt% to 40 wt%.

The content of solvent in the cooking aid of the present disclosure is, in one or more embodiments, 1 wt% to 80 wt%, preferably 5 wt% to 40 wt%. The content of the solvent may be determined according to the content of the radical scavenger in one or more embodiments. The blending ratio of the solvent to the radical scavenger (100 parts by weight) is, in one or more embodiments, 1 to 500 parts by weight, preferably 25 to 200 parts by weight.

The cooking aids of the present disclosure may contain water in one or more embodiments. The water content in the cooking aids of the present disclosure, in one or more embodiments, may be determined according to the solvent content. The mixing ratio of water and solvent (water/solvent) is 0.01 to 10, preferably 0.1 to 3, in one or more embodiments. The cooking aids of the present disclosure may, in one or more embodiments, be the balance water.

The cooking aids of the present disclosure, in one or more embodiments, may further include surfactants, defoamers, other additives, and the like.

As the surfactant, in one or more embodiments, a nonionic surfactant is preferable from the viewpoint of suppressing foaming. As nonionic surfactants, in one or more embodiments, polyoxyalkylene alkylamines, polyoxyalkylene alkyl ethers, polyoxyalkylene fatty acid esters, sucrose fatty acid esters, polyoxyalkylene alkylphenyl ethers, polyoxyalkylene poly Oxypropylene alkylamines, ethylene oxide adducts of sorbitan fatty acid esters, and the like can be mentioned. Alkylene oxides in nonionic surfactants include, in one or more embodiments, ethylene oxide and propylene oxide and combinations thereof. As nonionic surfactants, in one or more embodiments, polyoxyalkylene alkylamines and polyoxyalkylene alkyl ethers are preferred, and polyoxyethylene alkylamines and polyoxyethylene alkyl ethers are more preferred.

The cooking aid of the present disclosure, in one or more embodiments, can be produced by mixing a radical scavenger and a solvent, optionally adding water, surfactants, antifoaming agents, or other additives. It can be prepared by mixing the agents together, preferably by homogeneous mixing.

[Method for producing chemical pulp]
In one aspect, the present disclosure relates to a chemical pulp manufacturing method (chemical pulp manufacturing method of the present disclosure) comprising alkaline or sulfite digesting a lignocellulosic material in a chemical solution containing a radical scavenger and a solvent. According to the chemical pulp production method of the present disclosure, since the cooking is performed in the presence of a radical scavenger and a solvent, in one or more embodiments, a low kappa number pulp can be produced with a high pulp yield. can be done.

In one or more embodiments, the chemical solution used for cooking in the chemical pulp manufacturing method of the present disclosure contains at least a radical scavenger and a solvent, and further contains a chemical solution (cooking solution) used for alkaline cooking or sulfite cooking. As a chemical solution (cooking liquor) used for alkaline cooking or sulfite cooking, in one or more embodiments, in the cooking process in the production of chemical pulp such as sulfite pulp, dissolved sulfite pulp, soda pulp, kraft pulp, and dissolved kraft pulp Chemical solutions (cooking liquor) used, chemical solutions (treatment liquid) used in the oxygen delignification step, and the like.

In one or a plurality of embodiments, the chemical liquid (digesting liquor) used for alkaline cooking includes an alkaline solution (digesting liquor) and the like. The alkaline solution (cooking liquor), in one or more embodiments, contains sodium sulfide (Na ₂ S) and sodium hydroxide (NaOH), preferably sodium sulfide and sodium hydroxide as main components. . The sulfidity in alkaline (cooking liquor) is in one or more embodiments from 10% to 35%, preferably from 27% to 30%. The alkali addition amount (active alkali addition rate (AA)) is in one or more embodiments from 5% to 35%, preferably from 13% to 30%. Sulfidity is represented by (Na ₂ S)/(NaOH+Na ₂ S)×100. Active alkali is represented by converting NaOH concentration ₊ Na2S concentration into _Na2O .

In one or a plurality of embodiments, a chemical solution (digesting liquor) used for sulfite cooking includes a sulfite solution, a hydrogen sulfite solution (bisulfite solution), or the like.

In one or more embodiments, the chemical solution (treatment liquid) used in the oxygen delignification step includes an alkaline solution (treatment liquid) used in the oxygen delignification step. The alkaline solution, in one or more embodiments, includes an alkaline agent such as sodium hydroxide or potassium hydroxide. The pH of the alkaline solution is, in one or more embodiments, 11 or higher or 12 or higher, or 14 or lower or 13.5 or lower.

In one or more embodiments, the content of the radical scavenger and the solvent in the chemical solution used for cooking depends on the amount of lignocellulose material or pulp to be cooked (for example, absolute dry weight), sodium hydroxide, etc. in the chemical solution. can be appropriately determined according to the concentration of the alkaline agent. The contents of the radical scavenger and the solvent in the chemical solution used for cooking may be constant in one or more embodiments, or may be increased or decreased according to the concentration of the alkaline agent in the chemical solution. In one or more embodiments, the production method of the present disclosure may include increasing or decreasing the content of the radical scavenger and the solvent in the chemical according to the concentration of the alkaline agent in the chemical.

In one or more embodiments, the content of the radical scavenger in the chemical solution is 0.0005% to 5% by weight, preferably 0.001% to 5% by weight, relative to the absolute dry weight of the lignocellulose material. 2% by weight, more preferably 0.005% to 1% by weight. In one or more embodiments, the content of the solvent in the chemical solution is 0.0005% to 5% by weight, preferably 0.001% to 2% by weight, relative to the absolute dry weight of the lignocellulose material. %, more preferably 0.005 wt % to 1 wt %. In addition, in one or more embodiments, the total content of the radical scavenger and the solvent in the chemical solution may be 0.0005% to 5% by weight with respect to the absolute dry weight of the lignocellulose material. , preferably 0.001% to 2% by weight, more preferably 0.005% to 1% by weight.

The production method of the present disclosure, in one or more embodiments, may include a step of adding a radical scavenger and a solvent to the chemical solution to be digested. In one or more embodiments, the radical scavenger and the solvent may be added so that the content of the radical scavenger and the solvent in the chemical liquid to be digested is the above content. The amount of the radical scavenger and the solvent to be added can be appropriately determined according to the amount of the lignocellulose material or pulp to be digested and the concentration of the alkaline agent such as sodium hydroxide in the chemical solution in one or more embodiments. can. In one or a plurality of embodiments, the amount of the radical scavenger and the solvent added may be constant, or may be increased or decreased according to the concentration of the alkaline agent in the chemical solution. In one or more embodiments, the production method of the present disclosure may include increasing or decreasing the amounts of the radical scavenger and the solvent added according to the concentration of the alkaline agent in the chemical solution.

The location and timing of addition of the radical scavenger and the solvent are not particularly limited as long as they are added so that the lignocellulose material exhibits the above effects in digestion in the chemical solution containing the radical scavenger and solvent. The radical scavenger and solvent may be added simultaneously or separately in one or more embodiments. When they are added at the same time, the radical scavenger and solvent may be added as a pre-mixed one, or may be added after being prepared and mixed, or may be added without being mixed. The pulp cooking aid of the present disclosure may also be used as a radical scavenger and solvent.

In one or a plurality of embodiments, the radical scavenger and solvent are added at least one point from the step of supplying raw material chips prior to the digestion step to the digestion step of digesting the lignocellulose material with alkali or sulfite. In one or more embodiments, the radical scavenger and solvent may be added to the digester where cooking is performed, and from the viewpoint of improving yield, the raw material chip feeding step of supplying raw material chips to the digester. It is preferable to add either one. In one or a plurality of embodiments, addition points 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, a high-pressure feeder, and the like. Therefore, the production method of the present disclosure may include mixing at least one of the radical scavenger and the solvent with the raw material chips, and may include mixing the radical scavenger with the raw material chips.
Also, the radical scavenger and solvent may be added to the injection circulation line of the cooking liquor (white liquor and black liquor), and may be added to the oxygen digester in the delignification step after cooking in the digester. The radical scavenger and solvent may be added at once or in portions in one or more embodiments.

FIG. 1 shows an example of the flow of the chemical pulp manufacturing method. The flow of FIG. 1 includes a step of supplying raw material chips of lignocellulose material, a cooking step, and an oxygen delignification step.
(Raw material chip supply process)
Chips 11 of lignocellulose material chipped by a chipper (not shown) are stored in a chip silo 12 . After the chips stored in the chip silo 12 are selected by a chip screen (not shown) and sent to the chip bin 13 , the gas phase inside the chips is replaced with water vapor in the steaming vessel 14 .
(Cooking process)
The chips whose permeability has been enhanced in the steaming vessel 14 are introduced with an alkaline cooking liquid in the impregnation tower 15 to promote the permeation of the cooking liquid into the interior of the chips. After that, in the digester 16, wood chips, which are pulp materials, are mixed with a solution containing at least a radical scavenger, a solvent, sodium hydroxide, etc., and steamed under pressure to obtain a black liquor in which non-fiber components are dissolved. Pulp slurry mixed with pulp is discharged. Permeate tower 15 may also optionally be used as a prehydrolysis vessel (PHV) tower for prehydrolysis with acid.
(Oxygen delignification step)
The pulp slurry discharged from the digester 16 is washed in a black liquor washing tower 17, passed through a screen 18, a decker 19 and an unbleached high-concentration storage tower 20, and then introduced into an oxygen digester 21. Further delignification takes place in the oxygen digester 21 before being transferred to the bleaching step (not shown).

The heating temperature during cooking is, in one or more embodiments, 80°C to 200°C, preferably 140°C to 180°C. In one or more embodiments of the production method of the present disclosure, the lignocellulose material is heated at 80 ° C. to 200 ° C. in a chemical solution that is an alkaline solution containing a radical scavenger and a solvent. including.

The heating time during digestion is, in one or more embodiments, 30 minutes to 400 minutes, preferably 50 minutes to 300 minutes.

The production method of the present disclosure may include pre-treating the lignocellulosic material prior to the cooking as described above. In one or more embodiments, the pretreatment includes hydrothermal treatment (prehydrolysis treatment) and the like. Hydrothermal treatment, in one or more embodiments, can be performed by treating the chipped lignocellulose material with hot water or steam.

[Cooking method]
The present disclosure relates, in one aspect, to a method of alkaline or sulfite cooking of lignocellulosic material (cooking method of the disclosure) comprising cooking lignocellulosic material in a chemical solution containing a radical scavenger and a solvent. According to the cooking method of the present disclosure, in one or more embodiments, improved pulp yield after cooking and lower kappa number after cooking can be achieved. In the cooking method of the present disclosure, cooking can be performed in the same manner as in the production method of the present disclosure.

The present disclosure may relate to one or more embodiments of;
[1] A pulp cooking aid containing a radical scavenger and a solvent.
[2] The pulp cooking aid according to [1], wherein the solvent is selected from the group consisting of glycol-based solvents and glycol ether-based solvents.
[3] The radical scavenger is selected from the group consisting of tetramethylpiperidineoxyl radical scavengers, phenol radical scavengers, amine radical scavengers and quinone radical scavengers [1] or [2] Pulp cooking aid according to.
[4] A method for producing chemical pulp, comprising subjecting a lignocellulose material to alkaline digestion or sulfite digestion in a chemical solution containing a radical scavenger and a solvent.
[5] The production method according to [4], which includes adding a radical scavenger and a solvent to the chemical solution simultaneously or separately.
[6] The production method according to [4] or [5], wherein the cooking includes heating the chemical solution to a temperature of 80°C to 200°C.
[7] A method of digesting a lignocellulose material with alkali or sulfite, which comprises digesting the lignocellulose material in a chemical solution containing a radical scavenger and a solvent.

The present disclosure will be further described below using examples and reference examples. However, the present disclosure should not be construed as being limited to the following examples.

[Radical Scavenger]
H-TEMPO: 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl TBC: 4-tert-butylcatechol [solvent]
BDG: diethylene glycol mono-n-butyl ether EG: ethylene glycol PhG: ethylene glycol monophenyl ether BFDG: dipropylene glycol monobutyl ether

[Formulation stability confirmation test 1]
A confirmation test of the storage stability of a cooking aid containing a radical scavenger and a solvent was carried out.
H-TEMPO and BDG were mixed at the concentrations shown in Table 1 below, and the balance was adjusted with water to prepare a test solution. 20 ml of the test solution was placed in each 50 ml screw bottle and allowed to stand in a constant temperature bath at 0°C. When the test solution reached 0° C., a small amount of H-TEMPO crystals was added, and the solution was stored in a constant temperature bath at 0° C. for 1 day. As a comparative formulation example, the same evaluation was performed for a formulation containing only H-TEMPO (not mixed with BDG). Those results are shown in Table 1.

While crystals precipitated in H-TEMPO alone (comparative formulation example), no crystals precipitated in Formulation Examples 1 and 2 mixed with BDG. It was confirmed that it can be saved in . In addition, it was confirmed that, in the case of a preparation with a concentration of H-TEMPO of 30% by weight, the storage stability was further improved by increasing the concentration of BDG to 10% by weight or more.

[Formulation stability confirmation test 2]
H-TEMPO and EG were mixed at the concentrations shown in Table 2 below, and the balance was adjusted with water to prepare a test solution. Using the prepared test solution, it was carried out in the same manner as the stability confirmation test 1 except that it was stored in a -5 ° C. constant temperature bath. The results are shown in Table 2 below.

It was confirmed that preparations containing H-TEMPO could be stably stored even when EG was used as the solvent.

[Preparation of cooking aid]
Digesting aids A to E were prepared by mixing a radical scavenger and a solvent shown in Table 3 below at a ratio of 1:1 (weight ratio). Specifically, the cooking aids A to D were prepared by mixing an H-TEMPO aqueous solution with the solvents shown in Table 3 below so that the mixing ratio of each solvent to 100 parts by weight of H-TEMPO was 100 parts by weight. The cooking aid E was prepared by mixing TBC and BDG such that the mixing ratio of BDG to 100 parts by weight of TBC was 100 parts by weight. The content of active ingredients (total of radical scavenger and solvent) contained in cooking aids A to E is 46% by weight, and the blending ratio of solvent and water (water/solvent) is 2.3/1. .

[Example 1]
A 100 ml metal container is packed with 40 g (absolute dry weight) of red pine chips, and then the following cooking liquor (20% active alkali, 29% sulfidity) is added to the liquid ratio (ratio of cooking liquor weight to absolute dry weight of chips: cooking liquor / Chips) Add in 4.2, add any one of the cooking aids A to E so that the total concentration of the radical scavenger and solvent is 0.5% by weight with respect to the absolute dry weight of the chips, and then Cooking was carried out under the following cooking conditions. The screening yield and kappa number of the obtained unbleached pulp were measured according to the following methods. The results are shown in Table 4 below.
In the reference example, H-TEMPO or BDG was used instead of the cooking aid, and added to the cooking liquid so that the concentration of H-TEMPO or BDG relative to the absolute dry weight of the chips was 0.5% by weight, followed by the same treatment. and measured. Also, blanks were processed and measured in the same manner without the addition of drugs. These results are shown in Table 4.
<Cooking liquor>
Composition: 20% active alkali, 29% sulfidity
Active alkali: value obtained by converting NaOH concentration + Na ₂ S concentration into Na ₂ O <cooking conditions>
Apparatus: pressure vessel, nitrogen substitution Heating conditions: 160°C, 1.6 MPa, 3 hours

[Selection yield]
The obtained unbleached pulp was placed in a cloth bag, washed thoroughly with tap water, and then undigested fibers were removed using a flat screen (manufactured by Kumagai Riki Kogyo Co., Ltd.). . The screen pulp was dried at 105° C. for 3 hours to obtain the oven dry weight of the screen pulp. The screened yield was obtained by dividing the bone dry weight of the screened pulp by the bone dry weight of the chips before digestion and expressed in weight %. Also shown in FIG. 2 is a photograph of the uncooked fibers that were not screened on the flat screen.
[Kappa number]
The kappa number of the screened pulp was measured by the method of JIS P 8211.

As shown in Table 4, by cooking using a cooking liquor to which cooking aids A to E containing a radical scavenger (H-TEMPO or TBC) and a glycol-based solvent or glycol ether-based solvent were added, a blank was obtained. Compared to , it was confirmed that the selective yield was improved and the kappa number was lowered. In addition, the combined use of a radical scavenger and a glycol-based solvent or a glycol ether-based solvent (use of cooking aids A to E) improves the selective yield and reduces the kappa number. was higher than that used in

In addition, as shown in FIG. 2, although the cooking liquor and cooking conditions were the same except that the chemicals added to the cooking liquor were different, the cooking aid A containing H-TEMPO and BDG was added. When cooking using a liquid (Example 1-1), compared to the case of using a blank and a cooking liquid to which H-TEMPO or BDG alone was added (Blank or Reference Example 1 or 2), it remained on the flat screen. It was confirmed that the amount of undigested fibers was significantly reduced, and that the undigested fibers were loosened more finely. In other words, by adding H-TEMPO (radical scavenger) and BDG (solvent) to the cooking liquor, wood chips can be uniformly and sufficiently cooked to be sufficiently converted into pulp fibers, and this sufficient pulp fiberization can be achieved. As a result, the kappa number lowering effect of the solvent could be exerted on the whole pulp, so it can be said that both the improvement of the screening yield and the lowering of the kappa number were realized.

[Example 2]
The procedure was carried out in the same manner as in Example 1, except that 35 g (absolute dry weight) of acacia chips and chemicals shown in Table 5 below were used instead of red pine chips, and the active alkali was 16% and the sulfidity was 29%. The results are shown in Table 5 below.

As shown in Table 5, even when acacia chips are used instead of red pine chips, H-TEMPO or solvent (EG) can be obtained by cooking with a cooking liquor containing H-TEMPO and solvent (EG). As compared with the case of using a cooking liquor to which (EG) alone was added, it was possible to confirm an improvement effect in both the improvement of the clarification yield and the reduction of the kappa number.

Claims (7)

A pulp cooking aid containing a radical scavenger and a solvent ,
The solvent is selected from the group consisting of glycol-based solvents and glycol ether-based solvents,
The pulp cooking aid , wherein the radical scavenger is selected from the group consisting of tetramethylpiperidineoxyl-based radical scavengers, phenolic radical scavengers, and amine-based radical scavengers . The glycol-based solvent is selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and polypropylene glycol,
The glycol ether solvent includes ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monophenyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, and triethylene glycol. Monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether propionate, propylene glycol monobutyl ether, 3-methoxy-3-methyl-1-butanol, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether , and tripropylene glycol monomethyl ether . The tetramethylpiperidineoxyl radical scavenger includes 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, and bis-(2,2,6,6-tetramethylpiperidine-1-oxyl)-sebacate ,
the amine-based radical scavenger is selected from the group consisting of phenylenediamine-based radical scavengers, hydroxylamine-based radical scavengers, tributylamine, diphenylamine, phenothiazine, and phenyl-α-naphthylamine;
The phenolic radical scavenger includes 2-methylphenol, 2-ethylphenol, 2-propylphenol, 2-methoxyphenol, 2,4-dimethylphenol, 2,6-dimethylphenol, 2,6-dimethoxyphenol, 2 -tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-methylphenol, and 4-tert-butylcatechol (TBC) . of pulp cooking aids. Alkaline digestion or sulfite digestion of a lignocellulose material in a chemical solution containing a radical scavenger and a solvent;
The solvent is selected from the group consisting of glycol-based solvents and glycol ether-based solvents,
The method for producing chemical pulp, wherein the radical scavenger is selected from the group consisting of tetramethylpiperidineoxyl-based radical scavengers, phenolic radical scavengers, and amine-based radical scavengers . 5. The manufacturing method according to claim 4, comprising adding the radical scavenger and the solvent to the chemical solution simultaneously or separately. The production method according to claim 4 or 5, wherein the cooking includes heating the chemical solution to a temperature of 80°C to 200°C. digesting the lignocellulosic material in a chemical solution containing a radical scavenger and a solvent;
The solvent is selected from the group consisting of glycol-based solvents and glycol ether-based solvents,
A method for alkaline or sulfite digestion of a lignocellulose material, wherein the radical scavenger is selected from the group consisting of tetramethylpiperidineoxyl-based radical scavengers, phenolic radical scavengers, and amine-based radical scavengers .

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