Digestion promoter and method for producing pulp using the same

Abstract

To provide a digestion promoter that is safer, more effective in promoting digestion, and capable of obtaining pulp of better quality.SOLUTION: A digestion promoter contains at least one digestion promoter component selected from a group consisting of casein, amino acid having an aromatic ring or a heterocycle, and salts thereof.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a digestion promoter and a method for producing pulp using the same, and more particularly to a digestion promoter for lignocellulosic material and a method for producing pulp using the same. [Background technology]

[0002] To produce pulp from lignocellulosic materials from plants such as wood, a digestion process is generally carried out using alkali, sulfite, etc. Unnecessary lignin components, natural resin components, etc. are dissolved or dispersed by this digestion process, and then these components are removed by filtration, washing, etc. to obtain pulp.

[0003] On the other hand, the current situation is that excessive felling of natural resources such as lumber is restricted due to environmental issues, and the price of lumber is also rising. Therefore, it is becoming important to increase the amount of pulp produced per unit of raw wood and to produce high-quality pulp products. As a method for solving these problems, a method using a cooking accelerator is known.

[0004] For example, Japanese Patent Application Laid-Open No. 53-74101 (Patent Document 1) discloses a method for producing pulp, characterized in that in a cooking step in which lignocellulosic materials are treated with an alkaline chemical solution or a chemical solution containing sulfite to produce pulp, hydroxyanthracene or a hydroxyanthracene derivative is added as a cooking aid to a cooking liquor consisting of an alkaline chemical solution or a chemical solution containing sulfite, and the lignocellulosic materials are cooked by an alkali method or a sulfite method. In addition, International Publication No. 95 / 29288 (Patent Document 2) discloses a method for refining pulp raw materials by adding an aqueous dispersion of anthraquinones. However, because anthraquinones, hydroxyanthracene, and their derivatives are carcinogenic, their effects on the human body cannot be eliminated, and a cooking accelerator that does not use anthraquinones, etc., is required with greater consideration given to safety.

[0005] Furthermore, JP 2009-185413 A (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 obtained pulp is also insufficient, so there is a demand for a cooking accelerator that exerts a more excellent cooking promotion effect and can obtain pulp of better quality. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 53-74101 [Patent Document 2] WO 95 / 29288 [Patent Document 3] JP 2009-185413 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the problems associated with the above-mentioned conventional techniques, and has an object to provide a cooking accelerator that is safer, has a superior cooking acceleration effect, and is capable of producing pulp of superior quality, and a method for producing pulp using the same. [Means for solving the problem]

[0008] Means for Solving the Problems The present inventors have conducted intensive research in order to achieve the above object and have found that a cooking promoter containing, as a cooking promoter, at least one selected from the group consisting of casein, amino acids having an aromatic ring or a heterocycle, and salts thereof has an excellent cooking promoting effect and that the use of this cooking promoter makes it possible to obtain pulp of better quality, thereby completing the present invention.

[0009] That is, the present invention provides the following aspects. [1] A digestion promoter comprising at least one digestion promoter 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 [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 [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 bonded to the α-carbon. [4] The cooking accelerator described in [3], wherein the α-amino acid having a group containing a monocyclic aromatic ring or a monocyclic heterocycle bonded 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 [1] to [4]. Effect of the Invention

[0010] According to the present invention, it is possible to obtain a cooking accelerator which is safer, has a superior cooking acceleration effect, and is capable of producing pulp of superior quality, and by using this cooking accelerator, it is possible to produce pulp of superior quality. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0012] [Cooking accelerator] First, the cooking promoter of the present invention will be described. The cooking promoter of the present invention contains 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.

[0013] (Digestion promoter) 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 phosphoroprotein, and is mainly contained 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, such 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, but it is preferable to use it after separating it from raw milk or milk, from the viewpoint that casein has a better digestion-promoting effect and can be used as a digestion-promoting component to obtain pulp of better quality. In addition, 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 such amino acids having an aromatic ring or a heterocyclic ring, from the viewpoint of having a better digestion-promoting effect and being able to obtain pulp of better quality by using them as a digestion-promoting component, preferred are amino acids having a monocyclic aromatic ring or a monocyclic heterocyclic ring, more preferred are α-amino acids having a monocyclic aromatic ring or a monocyclic heterocyclic ring-containing group bonded to the α-carbon, even more preferred are α-amino acids having a monocyclic aromatic ring-containing group bonded to the α-carbon, and 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, calcium salt, etc.; inorganic acid salts such as hydrochloride salt, sulfate salt, etc.; organic acid salts such as acetate salt, malate salt, p-toluenesulfonate salt, etc.; and amine salts such as diethanolamine salt, triethanolamine salt, etc.

[0016] Tyrosine is one of the 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., but it is preferable to use it after separating it from the food, etc., from the viewpoint that tyrosine has a superior digestion-promoting effect and that by using it as a digestion-promoting component, pulp of superior quality can be obtained. Moreover, 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 contained in foods such as dried sardines, cheese, sardines, soybean products, pork, peanuts, chicken, and 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 it has a better digestion-promoting effect and that by using it as a digestion-promoting component, pulp of better quality can be obtained. Moreover, in the present invention, industrially produced phenylalanine can also be used.

[0018] In the present invention, among these digestion-promoting components, casein and salts thereof are particularly preferred from the viewpoint that they have a particularly excellent digestion-promoting effect and that their use as a digestion-promoting component makes it possible to obtain pulp of particularly excellent quality.

[0019] (Digestive accelerator) The digestion promoter of the present invention contains the digestion-promoting component, and the content of the digestion-promoting 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 the digestion-promoting effect and cost.

[0020] In the digestion promoter of the present invention, examples of other components contained when the content of the digestion-promoting component is less than 100% by mass include additives such as known nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, mineral oils, organic solvents, and natural solvents such as orange oil, etc. The incorporation of such additives improves the permeability and washability of the digestion-promoting component into raw materials such as lignocellulosic materials.

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

[0022] The amount of the digestion promoter of the present invention 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 %, based on the dry mass of the lignocellulosic material, from the viewpoints of the digestion promoting effect and cost.

[0023] The digestion 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 anthraquinones and hydroxyanthracenes) such as tannin, tannic acid, sugars such as glucose, and quaternary ammonium having a long-chain alkyl group.

[0025] [Method of producing pulp] Next, the method for producing pulp of the present invention will be described. The method for producing pulp of the present invention is a method for producing pulp which includes 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 in which heat or pressure is applied, or a chemical treatment in which an alkaline agent is used) to produce pulp, a washing step in which the obtained 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 a 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 as the washing and bleaching steps.

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

[0028] The lignocellulosic materials used in the pulp manufacturing method of the present invention are not particularly limited, and examples include wood (coniferous trees (Northern wood), broad-leaved trees (Large wood), etc.) as well as non-wood materials such as straw, bamboo, 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, soda 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 process is not particularly limited, and any known cooking equipment can be used, and may be of a continuous or batch type. In addition, as the cooking system, the MCC method (modified cooking method), the ITC method (all-tub isothermal cooking method), the Lo-solids method (reduction of solids in the tub), the BLI method (using black liquor in the impregnation stage), etc. can also be used.

[0031] In the pulp manufacturing method of the present invention, the timing and method of adding the cooking promoter of the present invention are not particularly limited, but it is preferable to add the cooking promoter in the cooking step for pulping or in the step preceding that. Specific examples of the cooking promoter 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 when the cooking equipment is of a continuous type.

[0032] The amount of the digestion promoter used in the digestion 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 %, based on the dry mass of the lignocellulosic material, from the viewpoints of the digestion-promoting effect and cost.

[0033] In the method for producing pulp of the present invention, the cooking accelerator of the present invention may be added as it 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 digestion 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 digestibility, energy cost, and safety.

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

[0036] In addition, oxygen may be introduced into the digester during the digestion treatment. There is no particular limitation on the method of introducing oxygen, and examples of the method include a method of setting the oxygen partial pressure high while adjusting the pressure of the digester and injecting oxygen or air into the digester, and a method of injecting oxygen or air when supplying the lignocellulosic material or the digestion liquid. The oxygen partial pressure is preferably 0.05 to 1 MPa, and more preferably 0.1 to 0.3 MPa. There is no particular limitation on the oxygen source as long as the oxygen partial pressure can be kept within the above range, and examples of the oxygen source include pure oxygen, air, and a mixed gas of oxygen and air. However, since increasing the pressure resistance of the digester increases the equipment cost, pure oxygen or a mixed gas of oxygen and air is preferred.

[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. EXAMPLES

[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) [Luminous wood, Kraft cooking method] (Kraft cooking process) A mixture of 50.0 g of L-wood wood chips (acacia) dried at 60 ° C for 24 hours, 6.46 g of sodium sulfide pentahydrate (reagent) (3.00 g of pure sodium sulfide), and 9.00 g of sodium hydroxide (reagent) was mixed with tap water to make a total of 200 g. 0.0150 g (0.03 mass% based on wood chips) of sodium caseinate (reagent, Tokyo Chemical Industry Co., Ltd.) was added to the obtained aqueous solution as a cooking accelerator, and the mixture was placed in a pot of a mini color dyeing tester (Texam Giken Co., Ltd.) and cooked (kraft cooking) at 160 ° C for 120 minutes to obtain a mixture of pulp and uncooked wood chips.

[0040] (Cleaning process) This mixture was placed on a two-stage sieve, consisting of a stainless steel sieve with 75 μm openings stacked on top of a stainless steel sieve with 710 μm openings, and shower-washed with tap water was repeated 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 each recovered.

[0042] [Wood chip residual rate] The resulting residual chips were dried at 105° C. for 10 hours, and then the mass was measured. This mass was taken as the “amount of residual chips after drying (g)” and calculated using the following formula: Residual rate of wood chips (%) = [amount of remaining chips after drying (g) / amount of wood chips used for cooking (50.0 g)] × 100 The residual rate of wood chips was calculated using the above method. The results are shown in Table 1.

[0043] [Pulp yield] The recovered pulp obtained was dried at 105° C. for 10 hours, and then the mass was measured, and this mass was defined as the "amount of recovered pulp after drying (actual value) (g)". Furthermore, assuming that the residual chips were subjected to a cooking treatment again, the following formula: Amount of pulp recovered after drying (corrected value) (g) = Amount of pulp recovered after drying (actual value) (g) + (amount of remaining chips after drying (g) / 2) As shown above, the actual "amount of recovered pulp after drying (actual value) (g)" is added to the "amount of remaining chips after drying (g) / 2" as the yield, and this is taken as the "amount of recovered pulp after drying (corrected value) (g)" and calculated using the following formula: Pulp yield (%) = [amount of pulp recovered after drying (corrected value) (g) / amount of wood chips used for cooking (50.0 g)] × 100 The pulp yield (%) was calculated based on the above. The results are shown in Table 1.

[0044] (Preparation of test strips) The recovered pulp obtained separately in the same manner as the above cooking and washing processes was spun into a paper with a basis weight of 150 g / m using a round papermaking machine (Kumagaya Riki Kogyo Co., Ltd.'s "Standard Sheet Machine Papermaking Device") in accordance with JIS P8222:2015 "Pulp - Preparation method for test handsheets - Method using a standard handsheet machine". 2 Then, the paper was pressed at 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 method for diffuse blue light reflectance - Indoor daylight conditions (ISO whiteness)" under conditions of C light source and measurement angle of 2°. The results are shown in Table 1.

[0047] (Examples A2 to A11) The same procedure as in Example A1 was used to cook and wash L-wood wood chips (acacia) except that the type and amount of the compound shown in Table 1 was used as the cooking accelerator, and 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 the test paper were measured. The results are shown in Table 1.

[0048] (Comparative Example A1) The wood chips (acacia) of L-wood were cooked and washed in the same manner as in Example A1, except that no cooking promoter was added, and 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 the test paper were measured. The results are shown in Table 1.

[0049] (Comparative examples A2~A5) The same procedure as in Example A1 was used to cook and wash L-wood wood chips (acacia) except that the type and amount of the compound shown in Table 1 was used as the cooking accelerator, and 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 the test paper were measured. The results are shown in Table 1.

[0050] [Table 1]

[0051] (Example B1) [N wood, Kraft cooking method] 50.0 g of N-wood wood chips (pine) dried at 60 ° C for 24 hours were 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 relative to wood chips). Except for this, the cooking and washing treatments were carried out in the same manner as in Example A1, and 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 whiteness of the test paper were measured. These results are shown in Table 2.

[0052] (Examples B2 to B11) The wood chips (pine) of N-type wood were cooked and washed in the same manner as in Example B1, except that the compounds shown in Table 2 were used as cooking accelerators in the types and amounts shown in Table 2. 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 the test paper were measured. The results are shown in Table 2.

[0053] (Comparative Example B1) The same procedure as in Example B1 was used to cook and wash N-wood wood chips (pine), except that no cooking promoter was added, and 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 the test paper were measured. These results are shown in Table 2.

[0054] (Comparative examples B2~B5) The wood chips (pine) of N-type wood were cooked and washed in the same manner as in Example B1, except that the compounds shown in Table 2 were used as cooking accelerators in the types and amounts shown in Table 2. 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 the test paper were measured. The results are shown in Table 2.

[0055] [Table 2]

[0056] (Example C1) [L-wood, polysulfide cooking method] (Polysulfide digestion treatment) A mixture of 50.0 g of L-wood wood chips (acacia) dried at 60 ° C for 24 hours, 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) was mixed with tap water to make a total of 200 g. The resulting aqueous solution was added with 0.0150 g (0.03 mass% relative to the wood chips) of sodium caseinate (reagent, manufactured by Tokyo Kasei Kogyo Co., Ltd.) as a cooking accelerator, and the mixture was placed in a pot of a mini color dyeing tester (manufactured by Texam Giken Co., Ltd.) and cooked (polysulfide cooking) at 160 ° C for 120 minutes to obtain a mixture of pulp and uncooked wood chips.

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

[0058] The residual wood chip percentage and pulp yield were calculated using the residual chips and recovered pulp obtained 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) The L-wood wood chips (acacia) were cooked and washed in the same manner as in Example C1, except that the type and amount of the compound shown in Table 3 was used as the cooking accelerator, and 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 the test paper were measured. These results are shown in Table 3.

[0060] (Comparative Example C1) The wood chips (acacia) of L-wood were cooked and washed in the same manner as in Example C1, except that no cooking promoter was added, and 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 the test paper were measured. The results are shown in Table 3.

[0061] (Comparative examples C2~C5) The L-wood wood chips (acacia) were cooked and washed in the same manner as in Example C1, except that the type and amount of the compound shown in Table 3 was used as the cooking accelerator, and 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 the test paper were measured. These results are shown in Table 3.

[0062] [Table 3]

[0063] (Example D1) [N wood, Kraft cooking method] 50.0 g of N-wood 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 relative to wood chips) of casein (derived from milk) (reagent, Fujifilm Wako Pure Chemical Industries, Ltd.) was used as a cooking accelerator. Except for this, the cooking and washing treatments were performed in the same manner as in Example C1, and the residual chips and recovered pulp were used to calculate the residual rate and pulp yield of the wood chips, and the kappa number of the recovered pulp and the whiteness of the test paper were measured. These results are shown in Table 4.

[0064] (Examples D2 to D3) The same procedure as in Example D1 was used to cook and wash N-wood wood chips (pine) except that the type and amount of the compound shown in Table 4 was used as the cooking accelerator, and 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 the test paper were measured. These results are shown in Table 4.

[0065] (Comparative Example D1) The same procedure as in Example D1 was used to cook and wash N-wood wood chips (pine), except that no cooking promoter was added, and 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 the test paper were measured. These results are shown in Table 4.

[0066] (Comparative examples D2~D5) The same procedure as in Example D1 was used to cook and wash N-wood wood chips (pine) except that the type and amount of the compound shown in Table 4 was used as the cooking accelerator, and 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 the test paper were measured. These results are shown in Table 4.

[0067] [Table 4]

[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 the cooking promoter (Examples), it was confirmed that the wood chip residual rate was lower, the pulp yield was higher, the kappa number was lower, and the whiteness was higher for both L-wood and N-wood wood chips and for both kraft cooking and polysulfide cooking methods, compared to when gelatin, alanine, valine, or leucine was used (Comparative Examples). [Industrial Applicability]

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

Claims

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

2. 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, characterized in that 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 digestion accelerator according to claim 3, characterized in that 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 carrying out a cooking treatment using the cooking promoter according to any one of claims 1 to 4.

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