Digestion accelerator and method for producing pulp using same

Abstract

This digestion accelerator contains at least one digestion-accelerating component selected from the group consisting of casein, an amino acid having an aromatic ring or a heterocyclic ring, and salts thereof.

Description

Cooking accelerator and method for producing pulp using the same

[0001] The present invention relates to a cooking accelerator and a method for producing pulp using the same, and more particularly to a cooking accelerator for lignocellulosic materials and a method for producing pulp using the same.

[0002] To produce pulp from plant lignocellulosic materials such as wood, a cooking process is generally carried out using alkali, sulfite, etc. This cooking process dissolves or disperses unnecessary lignin components, natural resin components, etc., and these components are then removed by filtration, washing, etc. to obtain pulp.

[0003] On the other hand, due to environmental concerns, the over-harvesting of natural resources such as lumber is being restricted, and the price of lumber is also rising. Therefore, it has become important to increase the amount of pulp produced per unit of log consumption and to produce high-quality pulp products. The use of cooking accelerators is known as a method to solve these problems.

[0004] For example, Japanese Patent Laid-Open Publication No. 53-74101 (Patent Document 1) discloses a method for producing pulp, in which lignocellulosic materials are treated with an alkaline chemical solution or a chemical solution containing sulfite to produce pulp. The method adds hydroxyanthracene or a hydroxyanthracene derivative as a cooking aid to a cooking liquor consisting of an alkaline chemical solution or a chemical solution containing sulfite, and cooks the lignocellulosic materials by the alkali method or the sulfite method. International Publication No. 95 / 29288 (Patent Document 2) also discloses a method for purifying pulp raw materials by adding an aqueous dispersion of anthraquinones. However, due to the carcinogenicity of anthraquinones and hydroxyanthracene and their derivatives, their effects on the human body cannot be eliminated. Therefore, there is a need for cooking accelerators that do not use anthraquinones, etc., with greater consideration given to safety.

[0005] Furthermore, Japanese Patent Laid-Open Publication No. 2009-185413 (Patent Document 3) discloses a cooking aid containing an organic acid such as an aminocarboxylic acid or an oxycarboxylic acid and / or a salt thereof. However, this cooking aid does not have a sufficient cooking promotion effect, and the quality of the pulp obtained is also insufficient. Therefore, there is a need for a cooking accelerator that exhibits a better cooking promotion effect and is capable of obtaining pulp of better quality.

[0006] JP 53-74101 A International Publication No. 95 / 29288 JP 2009-185413 A

[0007] The present invention has been made in view of the problems associated with the above-mentioned prior art, and aims to provide a cooking accelerator that is safer, has a superior cooking acceleration effect, and is capable of producing pulp of better quality, and a method for producing pulp using the same.

[0008] As a result of extensive research into achieving the above-mentioned object, the present inventors have found that a cooking accelerator containing, as a cooking-promoting component, at least one selected from the group consisting of casein, amino acids having an aromatic ring or a heterocyclic ring, and salts thereof, has an excellent cooking-promoting effect, and that the use of this cooking accelerator makes it possible to obtain pulp of better quality, which has led to the completion of the present invention.

[0009] That is, the present invention provides the following aspects. [1] A cooking accelerator containing at least one cooking accelerator component selected from the group consisting of casein, amino acids having an aromatic ring or a heterocyclic ring, and salts thereof. [2] The cooking accelerator according to [1], wherein the amino acid having an aromatic ring or a heterocyclic ring is an amino acid having a monocyclic aromatic ring or a monocyclic heterocyclic ring. [3] The cooking accelerator according to [2], wherein the amino acid having a monocyclic aromatic ring or a monocyclic heterocyclic ring is an α-amino acid having a group containing a monocyclic aromatic ring or a monocyclic heterocyclic ring bound to its α-carbon. [4] The cooking accelerator according to [3], wherein the α-amino acid having a group containing a monocyclic aromatic ring or a monocyclic heterocyclic ring bound to its α-carbon is at least one selected from the group consisting of tyrosine and phenylalanine. [5] A method for producing pulp, comprising a step of performing a cooking treatment using the cooking accelerator according to any one of [1] to [4].

[0010] According to the present invention, it is possible to obtain a cooking accelerator that is safer, has a superior cooking acceleration effect, and is capable of producing pulp of better quality, and by using this cooking accelerator, it is possible to produce pulp of better quality.

[0011] The present invention will be described in detail below with reference to preferred embodiments thereof. Note that the following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present invention, its applications, and its uses.

[0012] [Cooking Accelerator] First, the cooking accelerator of the present invention will be described. The cooking accelerator of the present invention contains at least one cooking accelerator component selected from the group consisting of casein, amino acids having an aromatic ring or a heterocyclic ring, and salts thereof.

[0013] (Digestion-promoting component) The digestion-promoting component used in the present invention is at least one compound selected from the group consisting of casein, amino acids having an aromatic ring or a heterocyclic ring, and salts thereof.

[0014] Casein is a type of phosphoprotein and is primarily found in raw animal milk, such as cow's milk, goat's milk, and camel's milk, and in plant milk, such as almond milk, coconut milk, and soy milk. In the present invention, casein may be used in a state contained in raw milk or milk, or in a state contained in skim milk powder obtained by skimming raw milk or milk. However, it is preferable to use casein separated from raw milk or milk, as it has a more excellent digestion-promoting effect and its use as a digestion-promoting component can produce pulp of higher quality. Industrially produced casein can also be used in the present invention. Examples of casein salts include metal salts such as sodium salt, potassium salt, magnesium salt, and calcium salt; inorganic acid salts such as hydrochloride and sulfate; organic acid salts such as acetate, malate, and p-toluenesulfonate; and amine salts such as diethanolamine salt and triethanolamine salt.

[0015] Examples of amino acids having an aromatic ring or a heterocyclic ring include α-amino acids having an aromatic ring or a heterocyclic ring-containing group bonded to the α-carbon (the carbon to which the carboxyl group and the amino group are bonded). Examples of the aromatic ring or heterocyclic ring-containing group include a benzyl group, a hydroxybenzyl group, and an imidazolylmethyl group. Among these amino acids having an aromatic ring or a heterocyclic ring, amino acids having a monocyclic aromatic ring or a monocyclic heterocyclic ring are preferred, from the viewpoint that they have a more excellent cooking-promoting effect and that their use as a cooking-promoting component allows for the production of pulp of better quality. α-amino acids having a monocyclic aromatic ring or a monocyclic heterocyclic ring-containing group bonded to the α-carbon are more preferred, and α-amino acids having a monocyclic aromatic ring-containing group bonded to the α-carbon are even more preferred. More specifically, tyrosine and phenylalanine are preferred, with tyrosine being particularly preferred. Examples of the salt of the amino acid having an aromatic ring or a heterocyclic ring include metal salts such as sodium salt, potassium salt, magnesium salt, and calcium salt; inorganic acid salts such as hydrochloride and sulfate; organic acid salts such as acetate, malate, and p-toluenesulfonate; and amine salts such as diethanolamine salt and triethanolamine salt.

[0016] Tyrosine is one of 22 amino acids used in protein biosynthesis in cells, and is found in large amounts in foods such as shrimp, cheese, whitebait, pork, chicken, and soy products. In the present invention, such tyrosine may be used in a state contained in the food, etc. However, it is preferable to use tyrosine separated from the food, etc., from the viewpoint that tyrosine has a superior digestion-promoting effect and its use as a digestion-promoting component allows for the production of pulp of higher quality. Furthermore, industrially produced tyrosine can also be used in the present invention.

[0017] Phenylalanine is an aromatic amino acid having a benzyl group and is one of the essential amino acids, and is found in large amounts in foods such as dried sardines, cheese, sardines, soybean products, pork, peanuts, and chicken, as well as in artificial sweeteners. In the present invention, such phenylalanine may be used in a state contained in the food, etc., but it is preferable to use it after separating it from the food, etc., from the viewpoint that its cooking-promoting effect is superior and that use as a cooking-promoting component can produce pulp of higher quality. Furthermore, industrially produced phenylalanine can also be used in the present invention.

[0018] In the present invention, among these digestion-promoting components, casein and salts thereof are particularly preferred, as they have a particularly excellent digestion-promoting effect and, when used as a digestion-promoting component, can produce pulp of particularly excellent quality.

[0019] (Cooking Accelerator) The cooking accelerator of the present invention contains the cooking accelerator component, and the content of the cooking accelerator component is preferably 1 to 100 mass%, more preferably 2 to 100 mass%, even more preferably 5 to 100 mass%, and particularly preferably 10 to 100 mass%, from the viewpoints of cooking acceleration effect and cost.

[0020] In the cooking accelerator of the present invention, when the content of the cooking-promoting component is less than 100% by mass, other components that may be contained include known additives such as nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, mineral oil, organic solvents, and natural solvents such as orange oil. The incorporation of such additives improves the penetration and cleanability of the cooking-promoting component into raw materials such as lignocellulosic materials.

[0021] Furthermore, since the digestion accelerator of the present invention cannot eliminate its effects on the human body (potential carcinogenicity), and from the viewpoint of safety, it is particularly preferable that it does not contain anthraquinones or hydroxyanthracenes. Examples of anthraquinones include anthraquinone and anthraquinone derivatives in which an alkyl group having 1 to 4 carbon atoms, an amino group, or a nitro group is bonded to the aromatic ring of anthraquinone, and anthraquinone and anthraquinone derivatives in which a portion of the aromatic ring of the anthraquinone derivative is hydrogenated. Examples of hydroxyanthracenes include hydroxyanthracene and hydroxyanthracene derivatives in which an alkyl group having 1 to 4 carbon atoms, an amino group, or a nitro group is bonded to the aromatic ring of anthraquinone, and anthraquinone derivatives in which a portion of the aromatic ring of the hydroxyanthracene derivative is hydrogenated.

[0022] From the viewpoints of the digestion promoting effect and cost, the amount of the digestion accelerator of the present invention to be used is preferably 0.0001 to 1.0 mass%, more preferably 0.001 to 0.5 mass%, and even more preferably 0.005 to 0.1 mass%, relative to the dry mass of the lignocellulose material.

[0023] The cooking accelerator of the present invention may be used as it is, or may be dissolved, emulsified or dispersed in water or an organic solvent. The organic solvent is not particularly limited, and examples thereof include lower alcohols having 1 to 6 carbon atoms such as methanol, ethanol and propanol, alkylene oxide adducts of the lower alcohols, glycols such as ethylene glycol, diethylene glycol and propylene glycol, and 3-methyl-3-methoxybutanol.

[0024] Furthermore, the cooking accelerator of the present invention may be used in combination with known cooking accelerators (excluding the above-mentioned anthraquinones and hydroxyanthracenes) such as tannin, tannic acid, sugars such as glucose, and quaternary ammonium having a long-chain alkyl group.

[0025] [Pulp Manufacturing Method] Next, the pulp manufacturing method of the present invention will be described. The pulp manufacturing method of the present invention is a pulp manufacturing method including a step of carrying out a cooking treatment using the cooking accelerator of the present invention.

[0026] Pulp production methods generally include a cooking step in which a raw material containing lignocellulosic material is cooked (for example, a physical treatment using heat or pressure, or a chemical treatment using an alkali agent, etc.) to produce pulp, a washing step in which the resulting crude pulp is washed, and a bleaching step in which the washed pulp is bleached. The pulp production method of the present invention is a method in which the cooking step in such a general pulp production method is performed using the cooking promoter of the present invention, and any known cooking method can be used except for using the cooking promoter of the present invention, and known washing and bleaching steps can be used for the washing and bleaching steps.

[0027] The cooking treatment using the cooking accelerator of the present invention is effective not only for producing pulp but also for producing lignin components and hemicellulose components separated from lignocellulose materials.

[0028] The lignocellulosic material used in the method for producing pulp of the present invention is not particularly limited, and examples thereof include wood (coniferous trees (N-wood), broad-leaved trees (L-wood), etc.) as well as non-wood materials such as straw, bamboo grass, reed, kenaf, mulberry, bamboo, herbs, and weeds.

[0029] The cooking method that can be used in the pulp manufacturing method of the present invention is not particularly limited, and examples thereof include known cooking methods such as alkaline cooking and sulfite cooking. Examples of alkaline cooking include kraft cooking, soda cooking, sodium carbonate cooking, and polysulfide cooking. Examples of sulfite cooking include alkaline sulfite cooking, neutral sulfite cooking, and bisulfite cooking. There are no particular limitations on the chemicals (cooking chemicals) used in these cooking methods, and chemicals suitable for each cooking method can be used.

[0030] The equipment (cooking equipment) used for the cooking treatment is not particularly limited, and any known cooking equipment can be used, whether it is a continuous or batch type. Also, cooking systems such as the MCC method (modified cooking method), the ITC method (all-cooker isothermal cooking method), the Lo-solids method (reduction of solids in the cooker), and the BLI method (use of black liquor in the impregnation stage) can be used.

[0031] In the pulp manufacturing method of the present invention, there are no particular limitations on the timing and method of adding the cooking promoter of the present invention, but it is preferable to add the cooking promoter in the cooking step for pulping or in the step before that.Specific examples include a method of adding the cooking promoter directly to the digester before cooking or during the cooking treatment, a method of mixing it with the cooking liquor, a method of spraying it on the lignocellulosic material before cooking, and a method of adding it to the circulating black liquor in the case of a continuous cooking facility.

[0032] The amount of the cooking promoter used in the cooking treatment is preferably 0.0001 to 1.0 mass%, more preferably 0.001 to 0.5 mass%, and even more preferably 0.005 to 0.1 mass%, relative to the dry mass of the lignocellulose material, from the viewpoints of cooking promotion effect and cost.

[0033] In the pulp manufacturing method of the present invention, the cooking accelerator of the present invention may be added as is, or may be added in a dissolved, emulsified, or dispersed state in water or an organic solvent. The organic solvent is not particularly limited, and examples thereof include lower alcohols having 1 to 6 carbon atoms, such as methanol, ethanol, and propanol; alkylene oxide adducts of the lower alcohols; glycols, such as ethylene glycol, diethylene glycol, and propylene glycol; and 3-methyl-3-methoxybutanol. Furthermore, the cooking accelerator of the present invention may be used in combination with known cooking accelerators (excluding the anthraquinones and hydroxyanthracenes), such as tannin, tannic acid, sugars, such as glucose, and quaternary ammonium having a long-chain alkyl group.

[0034] The temperature of the cooking treatment varies depending on the target pulp product and is not limited, but is preferably 50 to 300°C, more preferably 80 to 250°C, from the viewpoints of cooking ability, energy cost, and safety.

[0035] The pressure of the cooking treatment varies depending on the target pulp product and is not limited, but from the viewpoints of cooking ability, energy cost, and safety, it is preferably atmospheric pressure to 10 MPa, more preferably atmospheric pressure to 5 MPa.

[0036] Furthermore, oxygen may be introduced into the digester during the cooking treatment. The method for introducing oxygen is not particularly limited, and examples include a method in which the oxygen partial pressure is set high while adjusting the pressure in the digester and oxygen or air is injected into the digester, and a method in which oxygen or air is injected when the lignocellulosic material or cooking liquor is supplied. The oxygen partial pressure is preferably 0.05 to 1 MPa, and more preferably 0.1 to 0.3 MPa. The oxygen source is not particularly limited as long as the oxygen partial pressure can be maintained within the above range, and examples include pure oxygen, air, and a mixed gas of oxygen and air. However, pure oxygen or a mixed gas of oxygen and air is preferred because increasing the pressure resistance of the digester increases equipment costs.

[0037] Furthermore, during the cooking treatment, if necessary, an oxidizing agent such as a peroxide (e.g., hydrogen peroxide, potassium peroxide, etc.), a percarboxylic acid (e.g., peracetic acid, etc.), or a hydrogen peroxide adduct (e.g., sodium percarbonate, etc.) may be added to the cooking liquor to generate oxygen under cooking conditions.

[0038] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0039] Example A1 [Large-wood lumber, Kraft cooking method] (Kraft cooking treatment) 50.0 g of L-wood chips (acacia) dried at 60 ° C. for 24 hours as wood chips, 6.46 g of sodium sulfide pentahydrate (reagent) (3.00 g of pure sodium sulfide), and 9.00 g of sodium hydroxide (reagent) were mixed and tap water was added to a total of 200 g. 0.0150 g (0.03% by mass based on the wood chips) of sodium caseinate (reagent, manufactured by Tokyo Chemical Industry Co., Ltd.) was added as a cooking accelerator to the resulting aqueous solution, which was then placed in a pot of a Mini Color Dyeing Tester (manufactured by Texam Giken Co., Ltd.) and subjected to a cooking treatment (Kraft cooking treatment) at 160 ° C. for 120 minutes to obtain a mixture of pulp and uncooked wood chips.

[0040] (Washing Treatment) This mixture was repeatedly shower washed with tap water on a two-stage sieve, consisting of a stainless steel sieve with 75 μm openings placed on top of a stainless steel sieve with 710 μm openings, until the washing liquid became colorless.

[0041] After washing, the pulp remaining on the stainless steel sieve with 75 μm openings (hereinafter referred to as "recovered pulp") and the wood chips remaining on the stainless steel sieve with 710 μm openings (hereinafter referred to as "residual chips") were recovered.

[0042] [Wood chip residual ratio] The obtained residual chips were dried at 105°C for 10 hours, and then their mass was measured. This mass was defined as the "amount of residual chips after drying (g)" and the wood chip residual ratio was calculated using the following formula: Wood chip residual ratio (%) = [amount of residual chips after drying (g) / amount of wood chips used in cooking (50.0 g)] × 100. The results are shown in Table 1.

[0043] [Pulp Yield] The recovered pulp obtained was dried at 105°C for 10 hours, and then its mass was measured. This mass was recorded as the "amount of recovered pulp after drying (measured value) (g)." Furthermore, assuming that the residual chips would be subjected to another cooking treatment, the "amount of residual chips after drying (g) / 2" was added to the measured "amount of recovered pulp after drying (measured value) (g)" as a yield, as shown in the following formula: Amount of recovered pulp after drying (corrected value) (g) = Amount of recovered pulp after drying (measured value) (g) + (amount of residual chips after drying (g) / 2). This was used as the "amount of recovered pulp after drying (corrected value) (g)." The pulp yield (%) was then calculated using the following formula: Pulp Yield (%) = [Amount of recovered pulp after drying (corrected value) (g) / Amount of wood chips used for cooking (50.0 g)] × 100. The results are shown in Table 1.

[0044] (Preparation of test paper) The recovered pulp obtained separately in the same manner as in the cooking treatment and washing treatment described above was pulped using a round paper machine ("Standard Sheet Machine Paper Making Apparatus" manufactured by Kumagai Riki Kogyo Co., Ltd.) in accordance with JIS P8222:2015 "Pulp - Preparation method of test handsheets - Method using a standard handsheet machine" to a basis weight of 150 g / m ２ Thereafter, the paper was pressed at a pressure of 700 kPa for 5 minutes and dried at 105°C for 5 minutes using a drum dryer to obtain a test paper.

[0045] [Kappa number] The kappa number of the recovered pulp was measured using the test paper in accordance with JIS P8211:2011 "Pulp - Kappa number test method." The results are shown in Table 1.

[0046] [Whiteness] The whiteness of the test paper was measured using a spectrophotometer-type colorimeter (Technidyne's "Color Touch PC") in accordance with JIS P8148:2018 "Paper, paperboard and pulp - Measurement of diffuse blue light reflectance - Indoor daylight conditions (ISO whiteness)" under conditions of Illuminant C and a measurement angle of 2°. The results are shown in Table 1.

[0047] (Examples A2 to A11) L-type wood chips (acacia) were cooked and washed in the same manner as in Example A1, except that the types and amounts of compounds shown in Table 1 were used as cooking accelerators. The wood chip residual rate and pulp yield were calculated using the resulting residual chips and recovered pulp, and the kappa number of the recovered pulp and the brightness of test paper were measured. The results are shown in Table 1.

[0048] (Comparative Example A1) Wood chips (acacia) of L-type wood were cooked and washed in the same manner as in Example A1, except that no cooking accelerator was added. Using the resulting residual chips and recovered pulp, the wood chip residual rate and pulp yield were calculated, and the kappa number of the recovered pulp and the brightness of the test paper were measured. These results are shown in Table 1.

[0049] Comparative Examples A2 to A5: Wood chips (acacia) of L-type lumber were cooked and washed in the same manner as in Example A1, except that the types and amounts of compounds shown in Table 1 were used as cooking accelerators. The wood chip residual rate and pulp yield were calculated using the resulting residual chips and recovered pulp, and the kappa number of the recovered pulp and the brightness of test paper were measured. The results are shown in Table 1.

[0050]

[0051] (Example B1) [Natural wood, Kraft cooking method] 50.0 g of natural wood chips (pine) dried at 60 ° C for 24 hours was used as wood chips, and the amount of sodium sulfide pentahydrate was changed to 8.61 g (4.00 g of pure sodium sulfide), the amount of sodium hydroxide to 12.0 g, and the amount of sodium caseinate to 0.00250 g (0.005% by mass based on the wood chips). The cooking and washing processes were carried out in the same manner as in Example A1. The residual chips and recovered pulp were used to calculate the residual rate of wood chips and the pulp yield, and the kappa number of the recovered pulp and the brightness of the test paper were measured. The results are shown in Table 2.

[0052] (Examples B2 to B11) N-type wood chips (pine) were cooked and washed in the same manner as in Example B1, except that the types and amounts of compounds shown in Table 2 were used as cooking accelerators. Using the resulting residual chips and recovered pulp, the wood chip residual rate and pulp yield were calculated, and the kappa number of the recovered pulp and the brightness of test paper were measured. These results are shown in Table 2.

[0053] Comparative Example B1: Wood chips (pine) of N-type wood were cooked and washed in the same manner as in Example B1, except that no cooking accelerator was added. The residual wood chips and recovered pulp were used to calculate the residual wood chip rate and pulp yield, and the kappa number of the recovered pulp and the brightness of the test paper were measured. The results are shown in Table 2.

[0054] (Comparative Examples B2 to B5) Wood chips (pine) of N-type wood were cooked and washed in the same manner as in Example B1, except that the types and amounts of compounds shown in Table 2 were used as cooking accelerators. Using the resulting residual chips and recovered pulp, the wood chip residual rate and pulp yield were calculated, and the kappa number of the recovered pulp and the brightness of test paper were measured. These results are shown in Table 2.

[0055]

[0056] (Example C1) [Large-wood, polysulfide cooking method] (Polysulfide cooking treatment) 50.0 g of L-wood wood chips (acacia) dried at 60 ° C for 24 hours as wood chips, 4.31 g of sodium sulfide pentahydrate (reagent) (2.00 g of pure sodium sulfide), 9.00 g of sodium hydroxide (reagent), and 3.33 g of sodium tetrasulfide aqueous solution (manufactured by Nagao Co., Ltd.) (1.00 g of pure sodium tetrasulfide) were mixed, and tap water was added to a total of 200 g. 0.0150 g (0.03% by mass based on the wood chips) of sodium caseinate (reagent, manufactured by Tokyo Chemical Industry Co., Ltd.) was added as a cooking accelerator to the resulting aqueous solution, and the mixture was placed in a pot of a minicolor dyeing tester (manufactured by Texam Giken Co., Ltd.) and subjected to a cooking treatment (polysulfide cooking treatment) at 160 ° C for 120 minutes to obtain a mixture of pulp and uncooked wood chips.

[0057] (Washing Treatment) This mixture was subjected to washing treatment in the same manner as in Example A1, and recovered pulp and residual chips were each recovered.

[0058] The residual wood chip percentage and pulp yield were calculated using the resulting residual chips and recovered pulp in the same manner as in Example A1, and the kappa number of the recovered pulp and the brightness of the test paper were measured. The results are shown in Table 3.

[0059] (Examples C2 to C3) L-type wood chips (acacia) were cooked and washed in the same manner as in Example C1, except that the types and amounts of compounds shown in Table 3 were used as cooking accelerators. The wood chip residual rate and pulp yield were calculated using the resulting residual chips and recovered pulp, and the kappa number of the recovered pulp and the brightness of test paper were measured. These results are shown in Table 3.

[0060] (Comparative Example C1) In the same manner as in Example C1, except that no cooking accelerator was added, L-type wood chips (acacia) were cooked and washed, and the residual wood chips and recovered pulp were used to calculate the residual wood chip rate and pulp yield, and the kappa number of the recovered pulp and the brightness of the test paper were measured. These results are shown in Table 3.

[0061] Comparative Examples C2 to C5: Wood chips (acacia) of L-type wood were cooked and washed in the same manner as in Example C1, except that the types and amounts of compounds shown in Table 3 were used as cooking accelerators. The wood chip residual rate and pulp yield were calculated using the resulting residual chips and recovered pulp, and the kappa number of the recovered pulp and the brightness of test paper were measured. The results are shown in Table 3.

[0062]

[0063] (Example D1) [Natural wood, Kraft cooking method] 50.0 g of natural wood chips (pine) dried at 60 ° C. for 24 hours was used as wood chips, the amount of sodium sulfide pentahydrate was changed to 5.81 g (2.70 g of pure sodium sulfide), the amount of sodium hydroxide was changed to 12.0 g, the amount of sodium tetrasulfide aqueous solution was changed to 4.33 g (1.30 g of pure sodium tetrasulfide), and 0.0150 g (0.03% by mass of wood chips) of casein (milk-derived) (reagent, Fujifilm Wako Pure Chemical Industries, Ltd.) was used as a cooking accelerator. The cooking treatment and washing treatment were carried out in the same manner as in Example C1, and the residual chips and recovered pulp were used to calculate the residual rate of wood chips and the pulp yield. The kappa number of the recovered pulp and the brightness of the test paper were measured. These results are shown in Table 4.

[0064] (Examples D2 to D3) N-type wood chips (pine) were cooked and washed in the same manner as in Example D1, except that the types and amounts of compounds shown in Table 4 were used as cooking accelerators. The wood chip residual rate and pulp yield were calculated using the resulting residual chips and recovered pulp, and the kappa number of the recovered pulp and the brightness of test paper were measured. These results are shown in Table 4.

[0065] (Comparative Example D1) Wood chips (pine) of N-type wood were cooked and washed in the same manner as in Example D1, except that no cooking accelerator was added. Using the resulting residual chips and recovered pulp, the wood chip residual rate and pulp yield were calculated, and the kappa number of the recovered pulp and the brightness of the test paper were measured. These results are shown in Table 4.

[0066] (Comparative Examples D2 to D5) Wood chips (pine) of N-type wood were cooked and washed in the same manner as in Example D1, except that the types and amounts of compounds shown in Table 4 were used as cooking accelerators. The wood chip residual rate and pulp yield were calculated using the resulting residual chips and recovered pulp, and the kappa number of the recovered pulp and the brightness of test paper were measured. These results are shown in Table 4.

[0067]

[0068] As shown in Tables 1 to 4, when at least one compound selected from casein and its salts, tyrosine, and phenylalanine was used as a cooking accelerator (Examples), it was confirmed that the residual rate of wood chips was lower, the pulp yield was higher, the kappa number was lower, and the brightness was higher, for both L-wood and N-wood wood chips and for both Kraft cooking and polysulfide cooking, compared to when gelatin, alanine, valine, or leucine was used (Comparative Examples).

[0069] As described above, the present invention makes it possible to obtain a cooking accelerator that is safer, has a superior cooking accelerator effect, and is capable of producing pulp of higher quality. Therefore, the pulp production method of the present invention uses such a cooking accelerator, and is therefore useful as a method that can efficiently pulp lignocellulosic materials and produce pulp of higher quality.

Claims

1. A cooking promoter comprising at least one cooking promoter component selected from the group consisting of casein, amino acids having an aromatic ring or a heterocyclic ring, and salts thereof.

2. The digestion accelerator according to claim 1, wherein the amino acid having an aromatic ring or a heterocyclic ring is an amino acid having a monocyclic aromatic ring or a monocyclic heterocyclic ring.

3. The digestion accelerator according to claim 2, wherein the amino acid having a monocyclic aromatic ring or a monocyclic heterocyclic ring is an α-amino acid having a group containing a monocyclic aromatic ring or a monocyclic heterocyclic ring bound to the α-carbon.

4. The cooking accelerator according to claim 3, wherein the α-amino acid having a group containing a monocyclic aromatic ring or a monocyclic heterocyclic ring bound to the α carbon is at least one selected from the group consisting of tyrosine and phenylalanine.

5. A method for producing pulp, comprising a step of performing a cooking treatment using the cooking promoter according to any one of claims 1 to 4.

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