Digestion accelerator and method for producing pulp using same

Abstract

A digestion accelerator comprising 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

[Technical Field]

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

[0002] To produce pulp from a lignocellulosic material of a plant such as wood, a digestion treatment is generally performed using an alkali, a sulfite, or the like. By this digestion treatment, unnecessary lignin components, natural resin components, and the like are dissolved or dispersed, and then these components are removed by filtration and washing, or the like, whereby pulp is obtained.

[0003] On the other hand, indiscriminate logging of natural resources such as wood is regulated due to environmental problems and the like, and the current situation is that the price of wood is also becoming high. For this reason, it has become important to increase the production amount of pulp per unit of raw wood and to produce high-quality pulp products. As a method for solving these problems, a method using a digestion accelerator is known.

[0004] For example, Japanese Unexamined Patent Application Publication No. Sho 53-74101 (Patent Literature 1) discloses a method for producing pulp, wherein in a digestion step of pulping a lignocellulosic substance by treating it with an alkaline chemical solution or a chemical solution containing a sulfite, hydroxyanthracene or a hydroxyanthracene derivative is added as a digestion aid into a digestion liquid consisting of an alkaline chemical solution or a chemical solution containing a sulfite, and digestion of the lignocellulosic substance is performed by an alkaline method or a sulfite method. Furthermore, International Publication No. WO 95 / 29288 (Patent Literature 2) discloses a method for refining a pulp raw material by adding an aqueous dispersion of anthraquinone or the like. However, because of the problem of carcinogenicity of anthraquinones, hydroxyanthracene, and derivatives thereof, the effects on the human body cannot be eliminated, and considering greater safety, a digestion accelerator that does not use anthraquinone or the like is sought.

[0005] Furthermore, Japanese Unexamined Patent Application Publication No. 2009-185413 (Patent Literature 3) discloses a digestion aid containing an organic acid such as an aminocarboxylic acid or an oxycarboxylic acid and / or a salt thereof. However, since this digestion aid does not have a sufficient digestion accelerating effect and the quality of the obtained pulp is also not sufficient, a digestion accelerator that exhibits a more excellent digestion accelerating effect and that is also capable of obtaining pulp with more excellent quality is sought.[Citation List][Patent Literature]

[0006] [PTL 1] Japanese Unexamined Patent Application Publication No. Sho 53-74101 [PTL 2] International Publication No. WO 95 / 29288 [PTL 3] Japanese Unexamined Patent Application Publication No. 2009-185413 [Summary of Invention][Technical Problem]

[0007] The present invention has been made in view of the problems of the above-described conventional art, and an object of the present invention is to provide a digestion accelerator that is safer, is excellent in digestion accelerating effect, and is capable of obtaining pulp with more excellent quality, and a method for producing pulp using the same.[Solution to Problem]

[0008] As a result of diligent research conducted by the present inventors to achieve the above object, the present inventors found that a digestion accelerator containing, as a digestion accelerating component, at least one selected from the group consisting of casein, an amino acid having an aromatic ring or a heterocyclic ring, and salts thereof is excellent in digestion accelerating effect, and that by using this digestion accelerator, pulp with more excellent quality can be obtained, and have completed the present invention.

[0009] That is, the present invention provides the following aspects. [1] A digestion accelerator comprising 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. [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 in which a group containing a monocyclic aromatic ring or a monocyclic heterocyclic ring is bonded to the α-carbon. [4] The digestion accelerator according to [3], wherein the α-amino acid in which a group containing a monocyclic aromatic ring or a monocyclic heterocyclic ring is 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 digestion treatment using the digestion accelerator according to any one of [1] to [4]. [Advantageous Effects of Invention]

[0010] According to the present invention, it is possible to obtain a digestion accelerator that is safer, is excellent in digestion accelerating effect, and is capable of obtaining pulp with more excellent quality, and by using this digestion accelerator, it becomes possible to obtain pulp with more excellent quality.[Description of Embodiments]

[0011] Hereinafter, the present invention will be described in detail in accordance with preferred embodiments thereof. The following description of preferred embodiments is merely illustrative in nature and is not intended to limit the present invention, its application, or its uses.[Digestion Accelerator]

[0012] First, the digestion accelerator of the present invention will be described. The digestion accelerator of the present invention contains, as a digestion accelerating component, at least one selected from the group consisting of casein, an amino acid having an aromatic ring or a heterocyclic ring, and salts thereof.(Digestion Accelerating Component)

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

[0014] Casein is a type of phosphoprotein and is mainly contained in animal raw milk such as cow's milk, goat's milk, and camel's milk, and plant milk such as almond milk, coconut milk, and soy milk. In the present invention, such casein may be used in a state of being contained in the raw milk or the milk or in a state of being contained in skimmed milk powder that has been skimmed from the raw milk or the milk, but it is preferable to use casein separated from the raw milk or the milk from the viewpoint that the digestion accelerating effect is more excellent and that pulp with more excellent quality can be obtained by using it as a digestion accelerating component. Furthermore, in the present invention, industrially produced casein can also be used. Examples of the salt of casein 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 the amino acid having an aromatic ring or a heterocyclic ring include α-amino acids in which a group containing an aromatic ring or a heterocyclic ring is bonded to the α-carbon (the carbon to which a carboxyl group and an amino group are bonded). Examples of the group containing an aromatic ring or a heterocyclic ring include a benzyl group, a hydroxybenzyl group, and an imidazolylmethyl group. Among such amino acids having an aromatic ring or a heterocyclic ring, an amino acid having a monocyclic aromatic ring or a monocyclic heterocyclic ring is preferable, an α-amino acid in which a group containing a monocyclic aromatic ring or a monocyclic heterocyclic ring is bonded to the α-carbon is more preferable, an α-amino acid in which a group containing a monocyclic aromatic ring is bonded to the α-carbon is even more preferable, and more specifically, tyrosine and phenylalanine are preferable, and tyrosine is particularly preferable, from the viewpoint that the digestion accelerating effect is more excellent and that pulp with more excellent quality can be obtained by using it as a digestion accelerating component. 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 the 22 amino acids used in protein biosynthesis in cells and is contained in large amounts in foods such as sakura shrimp, cheese, whitebait, pork, chicken, and soy products. In the present invention, such tyrosine may be used in a state of being contained in the food or the like, but it is preferable to use tyrosine separated from the food or the like from the viewpoint that the digestion accelerating effect is more excellent and that pulp with more excellent quality can be obtained by using it as a digestion accelerating component. Furthermore, in the present invention, industrially produced tyrosine can also be used.

[0017] Phenylalanine is an aromatic amino acid having a benzyl group and one of the essential amino acids, and is contained in large amounts in foods such as dried sardines, cheese, sardines, soy products, pork, peanuts, and chicken, and artificial sweeteners. In the present invention, such phenylalanine may be used in a state of being contained in the food or the like, but it is preferable to use phenylalanine separated from the food or the like from the viewpoint that the digestion accelerating effect is more excellent and that pulp with more excellent quality can be obtained by using it as a digestion accelerating component. Furthermore, in the present invention, industrially produced phenylalanine can also be used.

[0018] In the present invention, among these digestion accelerating components, casein and salts thereof are particularly preferable from the viewpoint that the digestion accelerating effect is particularly excellent and that pulp with particularly excellent quality can be obtained by using it as a digestion accelerating component.(Digestion Accelerator)

[0019] The digestion accelerator of the present invention contains the digestion accelerating component, and from the viewpoint of digestion accelerating effect and cost, the content of the digestion accelerating component is preferably 1 to 100% by mass, more preferably 2 to 100% by mass, even more preferably 5 to 100% by mass, and particularly preferably 10 to 100% by mass.

[0020] In the digestion accelerator of the present invention, examples of other components included when the content of the digestion accelerating component is less than 100% by mass include additives such as known nonionic surfactants, known anionic surfactants, known cationic surfactants, known amphoteric surfactants, known mineral oil, known organic solvents, and known natural solvents such as orange oil. By blending such an additive, the permeability into a raw material such as a lignocellulosic material, the detergency, and the like of the digestion accelerating component are improved.

[0021] Furthermore, in the digestion accelerator of the present invention, from the viewpoint that the effects on the human body (possibility of carcinogenicity) cannot be eliminated and that safety is considered, it is particularly preferable that anthraquinone or the like and hydroxyanthracene or the like are not included. Examples of the 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 an aromatic ring of anthraquinone, and anthraquinone derivatives in which a part of the aromatic ring of anthraquinone and the anthraquinone derivatives is hydrogenated. Examples of the 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 an aromatic ring of hydroxyanthracene, and a hydroxyanthracene derivative in which a part of the aromatic ring of hydroxyanthracene and the hydroxyanthracene derivatives is hydrogenated.

[0022] From the viewpoint of digestion accelerating effect and cost, the amount of the digestion accelerator of the present invention used is preferably 0.0001 to 1.0% by mass, more preferably 0.001 to 0.5% by mass, and even more preferably 0.005 to 0.1% by mass with respect to the dry mass of the lignocellulosic material.

[0023] Furthermore, the digestion accelerator of the present invention may be used as it is, but may also be used by dissolving, emulsifying, or dispersing it in water or an organic solvent. The organic solvent is not particularly limited, but 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 digestion accelerator of the present invention may be used in combination with a known digestion accelerator (excluding the anthraquinones and the hydroxyanthracenes) such as saccharides like tannin, tannic acid, and glucose, and a quaternary ammonium having a long-chain alkyl group.[Method for Producing Pulp]

[0025] Next, the method for producing pulp of the present invention will be described. The method for producing pulp of the present invention includes a step of performing a digestion treatment using the digestion accelerator of the present invention.

[0026] A method for producing pulp generally includes a digestion step of pulping a raw material containing a lignocellulosic material by a digestion treatment (for example, a physical treatment performed by applying heat, pressure, or the like, or a chemical treatment performed using an alkali agent or the like), a washing step of washing the obtained crude pulp, and a bleaching step of bleaching the washed pulp. The method for producing pulp of the present invention is a method of performing a digestion treatment using the digestion accelerator of the present invention in the digestion step of such a general method for producing pulp, and a known digestion treatment method can be adopted except for using the digestion accelerator of the present invention, and a known washing step and a known bleaching step can be adopted as the washing step and the bleaching step.

[0027] The digestion treatment using the digestion accelerator of the present invention is also effective not only in the production of pulp, but also in the production of lignin components and hemicellulose components separated from the lignocellulosic material.

[0028] The lignocellulosic material used in the method for producing pulp of the present invention is not particularly limited, and examples thereof include not only wood (softwood (N-wood), hardwood (L-wood), etc.), but also non-wood materials such as straw, bagasse, reed, kenaf, mulberry, bamboo, herbaceous plants, and weeds.

[0029] The digestion treatment method that can be adopted in the method for producing pulp of the present invention is not particularly limited, and examples thereof include known digestion treatment methods such as an alkaline digestion method and a sulfite digestion method. Examples of the alkaline digestion method include a kraft digestion method, a soda digestion method, a soda-ash digestion method, and a polysulfide digestion method. Examples of the sulfite digestion method include an alkaline sulfite digestion method, a neutral sulfite digestion method, and a bisulfite digestion method. The chemical solution (digestion chemical solution) used in these digestion treatment methods is not particularly limited, and a chemical solution suitable for each digestion method can be used.

[0030] The equipment (digestion equipment) used for the digestion treatment is not particularly limited, and known digestion equipment can be used, and it may be a continuous type or a batch type. Furthermore, as the digestion system, an MCC method (modified continuous cooking method), an ITC method (isothermal cooking method), a Lo-solids method (reduction of solids in the digester), a BLI method (use of black liquor in an impregnation stage), or the like can also be adopted.

[0031] In the method for producing pulp of the present invention, the timing and method of addition of the digestion accelerator of the present invention are not particularly limited, but it is preferable to add the digestion accelerator in the digestion step of pulping and in a step prior thereto, and specifically, examples thereof include a method of directly adding the digestion accelerator to a digester before or during the digestion treatment, a method of mixing the digestion accelerator with a digestion chemical solution, a method of spraying the digestion accelerator onto the lignocellulosic material before digestion, and a method of adding the digestion accelerator to the circulating black liquor when the digestion equipment is a continuous type.

[0032] From the viewpoint of digestion accelerating effect and cost, the amount of the digestion accelerator used in the digestion treatment is preferably 0.0001 to 1.0% by mass, more preferably 0.001 to 0.5% by mass, and even more preferably 0.005 to 0.1% by mass with respect to the dry mass of the lignocellulosic material.

[0033] In the method for producing pulp of the present invention, the digestion accelerator of the present invention may be added as it is, but may also be added in a state of being dissolved, emulsified, or dispersed in water or an organic solvent. The organic solvent is not particularly limited, but 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 digestion accelerator of the present invention may be used in combination with a known digestion accelerator (excluding the anthraquinones and the hydroxyanthracenes) such as saccharides like tannin, tannic acid, and glucose, and a 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 from the viewpoint of digestibility, energy cost, and safety, it is preferably 50 to 300°C, and more preferably 80 to 250°C.

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

[0036] Furthermore, during the digestion treatment, oxygen may be introduced into the digester. The method for introducing oxygen is not particularly limited, and examples thereof include a method of setting the oxygen partial pressure high while adjusting the pressure of the digester and injecting oxygen or air under pressure into the digester, and a method of injecting oxygen or air under pressure during the supply of the lignocellulosic material or the supply of the digestion chemical solution. 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 thereof include pure oxygen, air, and a mixed gas of oxygen and air, but since increasing the pressure resistance of the digestion apparatus increases equipment costs, pure oxygen or a mixed gas of oxygen and air is preferable.

[0037] Furthermore, during the digestion treatment, as necessary, an oxidizing agent such as a peroxide (for example, hydrogen peroxide, potassium peroxide, etc.), a percarboxylic acid (for example, peracetic acid, etc.), or a hydrogen peroxide adduct (for example, sodium percarbonate, etc.) may be added to the digestion chemical solution to generate oxygen under digestion conditions.[Examples]

[0038] Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.(Example A1)[L-wood, Kraft Digestion Method](Kraft Digestion Treatment)

[0039] To a mixture of 50.0 g of L-wood wood chips (acacia) dried at 60°C for 24 hours as wood chips, 6.46 g of sodium sulfide pentahydrate (reagent) (3.00 g as a pure component of sodium sulfide), and 9.00 g of sodium hydroxide (reagent), tap water was added to make a total of 200 g. To the obtained aqueous solution, 0.0150 g (0.03% by mass with respect to the wood chips) of sodium caseinate (reagent, manufactured by Tokyo Chemical Industry Co., Ltd.) as a digestion accelerator was added, and the mixture was charged into a pot of a mini color dyeing tester (manufactured by Texam Giken Co., Ltd.), and a digestion treatment (kraft digestion treatment) was performed at 160°C for 120 minutes to obtain a mixture of pulp and undigested wood chips.(Washing Treatment)

[0040] This mixture was subjected to repeated shower washing with tap water on a two-stage sieve in which a stainless steel sieve with an opening of 75 µm was stacked on a stainless steel sieve with an opening of 710 µm, until the washing liquid became colorless.

[0041] After washing, the pulp remaining on the stainless steel sieve with an opening of 75 µm (hereinafter, referred to as "recovered pulp") and the wood chips remaining on the stainless steel sieve with an opening of 710 µm (hereinafter, referred to as "residual chips") were respectively recovered.[Residual Rate of Wood Chips]

[0042] The obtained residual chips were dried at 105°C for 10 hours, and then the mass thereof was measured. This mass was taken as the "Amount of residual chips after drying (g)," and the residual rate of wood chips was calculated by the following formula: The results are shown in Table 1.[Pulp Yield]

[0043] The obtained recovered pulp was dried at 105°C for 10 hours, and then the mass thereof was measured. This mass was taken as the "Amount of recovered pulp after drying (measured value) (g)." Furthermore, assuming that the residual chips are subjected to digestion treatment again, "Amount of residual chips after drying (g) / 2" was added as a yield portion to the measured "Amount of recovered pulp after drying (measured value) (g)", and this was taken as the "Amount of recovered pulp after drying (corrected value) (g)", as in the following formula: The pulp yield (%) was calculated by the following formula:

[0044] The results are shown in Table 1.(Preparation of Test Paper)

[0045] Recovered pulp separately obtained in the same manner as the above-described digestion treatment and washing treatment was handsheeted under the condition of a basis weight of 150 g / m 2< using a round paper machine ("Standard Sheet Machine Papermaking Device" manufactured by Kumagai Riki Kogyo Co., Ltd.) in accordance with JIS P8222:2015 "Pulps - Preparation of laboratory sheets for physical testing - Part 1: Conventional sheet-former method." Thereafter, a press treatment was performed at a pressure of 700 kPa for 5 minutes, and the sheet was dried at 105°C for 5 minutes using a drum dryer to obtain a test paper.[Kappa Number]

[0046] The Kappa number of the recovered pulp was measured using the test paper in accordance with JIS P8211:2011 "Pulps - Determination of Kappa number." The results are shown in Table 1.[Whiteness]

[0047] The whiteness of the test paper was measured using a spectrophotometric colorimeter ("Color Touch PC" manufactured by Technidyne Corporation) in accordance with JIS P8148:2018 "Paper, board and pulps - Measurement of diffuse blue reflectance factor - Indoor daylight conditions (ISO brightness)" under the conditions of a C illuminant and a measurement angle of 2°. The results are shown in Table 1.(Examples A2 to A11)

[0048] A digestion treatment and a washing treatment of L-wood wood chips (acacia) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example A1, except that the type and amount of the compound shown in Table 1 were used as the digestion accelerator. These results are shown in Table 1.(Comparative Example A1)

[0049] A digestion treatment and a washing treatment of L-wood wood chips (acacia) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example A1, except that no digestion accelerator was added. These results are shown in Table 1.(Comparative Examples A2 to A5)

[0050] A digestion treatment and a washing treatment of L-wood wood chips (acacia) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example A1, except that the type and amount of the compound shown in Table 1 were used as the digestion accelerator. These results are shown in Table 1. [Table 1]L-wood Kraft Digestion MethodDigestion AcceleratorWood Chip Residual Rate [%]Pulp Yield [%]Kappa NumberWhitenessTypeAmount [%] (relative to wood chip amount)Example A1Sodium caseinate0.030.0350.615.238.3Example A2Casein (milk-derived)0.0050.0750.315.538.1Example A3Casein (milk-derived)0.010.0650.415.338.2Example A4Casein (milk-derived)0.030.0350.615.138.2Example A5Casein (milk-derived)0.10.0150.714.938.4Example A6L-(-)-Tyrosine0.0050.1450.116.137.8Example A7L-(-)-Tyrosine0.010.1250.216.037.9Example A8L-(-)-Tyrosine0.030.0950.215.738.1Example A9L-(-)-Tyrosine0.10.0750.415.538.1Example A10DL-Tyrosine0.030.0750.315.838.0Example A11L-Phenylalanine0.030.1550.016.237.8Comp. Ex. A1None00.3949.118.337.0Comp. Ex. A2Gelatin0.030.2349.717.237.5Comp. Ex. A3L-Alanine0.030.2749.417.337.3Comp. Ex. A4L-Valine0.030.2749.517.237.3Comp. Ex. A5L-Leucine0.030.2949.517.237.4Sodium caseinate: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. Casein (milk-derived): reagent, manufactured by FUJIFILM Wako Pure Chemical Corporation L-(-)-Tyrosine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. DL-Tyrosine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Phenylalanine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. Gelatin: reagent, manufactured by FUJIFILM Wako Pure Chemical Corporation L-Alanine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Valine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Leucine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. (Example B1)[N-wood, Kraft Digestion Method]

[0051] A digestion treatment and a washing treatment were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example A1, except that 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 8.61 g (4.00 g as a pure component of sodium sulfide), the amount of sodium hydroxide was changed to 12.0 g, and the amount of sodium caseinate was changed to 0.00250 g (0.005% by mass with respect to the wood chips). These results are shown in Table 2.(Examples B2 to B11)

[0052] A digestion treatment and a washing treatment of N-wood wood chips (pine) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example B1, except that the type and amount of the compound shown in Table 2 were used as the digestion accelerator. These results are shown in Table 2.(Comparative Example B1)

[0053] A digestion treatment and a washing treatment of N-wood (softwood) wood chips (pine) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example B1, except that no digestion accelerator was added. These results are shown in Table 2.(Comparative Examples B2 to B5)

[0054] A digestion treatment and a washing treatment of N-wood wood chips (pine) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example B1, except that the type and amount of the compound shown in Table 2 were used as the digestion accelerator. These results are shown in Table 2. [Table 2]N-wood Kraft Digestion MethodDigestion AcceleratorWood Chip Residual Rate [%]Pulp Yield [%]Kappa NumberWhitenessTypeAmount [%] (relative to wood chip amount)Example B1Sodium caseinate0.0050.0651.827.335.2Example B2Sodium caseinate0.010.0351.927.135.3Example B3Sodium caseinate0.030.0252.026.735.3Example B4Sodium caseinate0.10.0152.126.435.5Example B5Casein (milk-derived)0.030.0252.026.835.4Example B6L-(-)-Tyrosine0.030.0751.727.535.1Example B7DL-Tyrosine0.0050.1151.528.134.9Example B8DL-Tyrosine0.010.0951.627.935.0Example B9DL-Tyrosine0.030.0751.727.735.1Example B10DL-Tyrosine0.10.0551.827.135.3Example B11L-Phenylalanine0.030.1351.328.334.9Comp. Ex. B1None00.3350.230.334.1Comp. Ex. B2Gelatin0.030.1950.729.334.5Comp. Ex. B3L-Alanine0.030.2150.529.534.4Comp. Ex. B4L-Valine0.030.2250.529.534.3Comp. Ex. B5L-Leucine0.030.2250.429.634.4Sodium caseinate: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. Casein (milk-derived): reagent, manufactured by FUJIFILM Wako Pure Chemical Corporation L-(-)-Tyrosine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. DL-Tyrosine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Phenylalanine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. Gelatin: reagent, manufactured by FUJIFILM Wako Pure Chemical Corporation L-Alanine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Valine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Leucine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. (Example C1)[L-wood, Polysulfide Digestion Method](Polysulfide Digestion Treatment)

[0055] To a mixture of 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 as a pure component of sodium sulfide), 9.00 g of sodium hydroxide (reagent), and 3.33 g of an aqueous solution of sodium tetrasulfide (manufactured by Nagao & Co., Ltd.) (1.00 g as a pure component of sodium tetrasulfide), tap water was added to make a total of 200 g. To the obtained aqueous solution, 0.0150 g (0.03% by mass with respect to the wood chips) of sodium caseinate (reagent, manufactured by Tokyo Chemical Industry Co., Ltd.) as a digestion accelerator was added, and the mixture was charged into a pot of a mini color dyeing tester (manufactured by Texam Giken Co., Ltd.), and a digestion treatment (polysulfide digestion treatment) was performed at 160°C for 120 minutes to obtain a mixture of pulp and undigested wood chips.(Washing Treatment)

[0056] This mixture was subjected to a washing treatment in the same manner as in Example A1, and recovered pulp and residual chips were respectively recovered.

[0057] In the same manner as in Example A1, using the obtained residual chips and recovered pulp, the residual rate of wood chips and the pulp yield were calculated, and the Kappa number of the recovered pulp and the whiteness of the test paper were measured. These results are shown in Table 3.(Examples C2 to C3)

[0058] A digestion treatment and a washing treatment of L-wood wood chips (acacia) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example C1, except that the type and amount of the compound shown in Table 3 were used as the digestion accelerator. These results are shown in Table 3.(Comparative Example C1)

[0059] A digestion treatment and a washing treatment of L-wood wood chips (acacia) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example C1, except that no digestion accelerator was added. These results are shown in Table 3.(Comparative Examples C2 to C5)

[0060] A digestion treatment and a washing treatment of L-wood wood chips (acacia) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example C1, except that the type and amount of the compound shown in Table 3 were used as the digestion accelerator. These results are shown in Table 3. [Table 3]L-wood Polysulfide Digestion MethodDigestion AcceleratorWood Chip Residual Rate [%]Pulp Yield [%]Kappa NumberWhitenessTypeAmount [%] (relative to wood chip amount)Example C1Sodium caseinate0.030.0350.515.038.4Example C2L-(-)-Tyrosine0.030.0850.215.538.1Example C3L-Phenylalanine0.030.1650.016.037.9Comp. Ex. C1None00.4049.118.037.1Comp. Ex. C2Gelatin0.030.2649.616.837.4Comp. Ex. C3L-Alanine0.030.2849.416.937.3Comp. Ex. C4L-Valine0.030.2849.516.937.2Comp. Ex. C5L-Leucine0.030.3049.417.037.3Sodium caseinate: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-(-)-Tyrosine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Phenylalanine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. Gelatin: reagent, manufactured by FUJIFILM Wako Pure Chemical Corporation L-Alanine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Valine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Leucine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. (Example D1)[N-wood, Kraft Digestion Method]

[0061] A digestion treatment and a washing treatment were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example C1, except that 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 as a pure component of sodium sulfide), the amount of sodium hydroxide was changed to 12.0 g, the amount of the aqueous solution of sodium tetrasulfide was changed to 4.33 g (1.30 g as a pure component of sodium tetrasulfide), and 0.0150 g (0.03% by mass with respect to the wood chips) of casein (milk-derived) (reagent, manufactured by FUJIFILM Wako Pure Chemical Corporation) was used as the digestion accelerator. These results are shown in Table 4.(Examples D2 to D3)

[0062] A digestion treatment and a washing treatment of N-wood wood chips (pine) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example D1, except that the type and amount of the compound shown in Table 4 were used as the digestion accelerator. These results are shown in Table 4.(Comparative Example D1)

[0063] A digestion treatment and a washing treatment of N-wood (softwood) wood chips (pine) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example D1, except that no digestion accelerator was added. These results are shown in Table 4.(Comparative Examples D2 to D5)

[0064] A digestion treatment and a washing treatment of N-wood wood chips (pine) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example D1, except that the type and amount of the compound shown in Table 4 were used as the digestion accelerator. These results are shown in Table 4. [Table 4]N-wood Polysulfide Digestion MethodDigestion AcceleratorWood Chip Residual Rate [%]Pulp Yield [%]Kappa NumberWhitenessTypeAmount [%] (relative to wood chip amount)Example D1Casein (milk-derived)0.030.0352.126.535.6Example D2DL-Tyrosine0.030.0751.727.435.2Example D3L-Phenylalanine0.030.1251.428.134.9Comp. Ex. D1None00.3350.230.334.1Comp. Ex. D2Gelatin0.030.2150.628.934.5Comp. Ex. D3L-Alanine0.030.2350.229.234.3Comp. Ex. D4L-Valine0.030.2450.329.334.4Comp. Ex. D5L-Leucine0.030.2450.329.134.3Casein (milk-derived): reagent, manufactured by FUJIFILM Wako Pure Chemical Corporation DL-Tyrosine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Phenylalanine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. Gelatin: reagent, manufactured by FUJIFILM Wako Pure Chemical Corporation L-Alanine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Valine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Leucine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd.

[0065] As shown in Tables 1 to 4, in the cases where at least one compound of casein and salts thereof, tyrosine, and phenylalanine was used as the digestion accelerator (Examples), it was confirmed that, compared to the cases where gelatin, alanine, valine, or leucine was used (Comparative Examples), in both L-wood and N-wood wood chips and in both the kraft digestion and polysulfide digestion methods, the residual rate of wood chips becomes low, the pulp yield becomes high, the Kappa number becomes low, and the whiteness becomes high.[Industrial Applicability]

[0066] As described above, according to the present invention, it becomes possible to obtain a digestion accelerator that is safer, is excellent in digestion accelerating effect, and is capable of obtaining pulp with more excellent quality. Therefore, since the method for producing pulp of the present invention uses such a digestion accelerator, lignocellulosic materials can efficiently pulped and the method is also useful as a method capable of obtaining pulp with more excellent quality.

Examples

examples

[Examples]

[0038]Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

example a1

(Example A1)

[L-wood, Kraft Digestion Method]

(Kraft Digestion Treatment)

[0039]To a mixture of 50.0 g of L-wood wood chips (acacia) dried at 60°C for 24 hours as wood chips, 6.46 g of sodium sulfide pentahydrate (reagent) (3.00 g as a pure component of sodium sulfide), and 9.00 g of sodium hydroxide (reagent), tap water was added to make a total of 200 g. To the obtained aqueous solution, 0.0150 g (0.03% by mass with respect to the wood chips) of sodium caseinate (reagent, manufactured by Tokyo Chemical Industry Co., Ltd.) as a digestion accelerator was added, and the mixture was charged into a pot of a mini color dyeing tester (manufactured by Texam Giken Co., Ltd.), and a digestion treatment (kraft digestion treatment) was performed at 160°C for 120 minutes to obtain a mixture of pulp and undigested wood chips.

(Washing Treatment)

[0040]This mixture was subjected to repeated shower washing with tap water on a two-stage sieve in which a stainless steel sieve with an opening of 75 µm wa...

examples a2 to a11

(Examples A2 to A11)

[0048]A digestion treatment and a washing treatment of L-wood wood chips (acacia) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example A1, except that the type and amount of the compound shown in Table 1 were used as the digestion accelerator. These results are shown in Table 1.

[Technical Field]

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

[0002] To produce pulp from a lignocellulosic material of a plant such as wood, a digestion treatment is generally performed using an alkali, a sulfite, or the like. By this digestion treatment, unnecessary lignin components, natural resin components, and the like are dissolved or dispersed, and then these components are removed by filtration and washing, or the like, whereby pulp is obtained.

[0003] On the other hand, indiscriminate logging of natural resources such as wood is regulated due to environmental problems and the like, and the current situation is that the price of wood is also becoming high. For this reason, it has become important to increase the production amount of pulp per unit of raw wood and to produce high-quality pulp products. As a method for solving these problems, a method using a digestion accelerator is known.

[0004] For example, Japanese Unexamined Patent Application Publication No. Sho 53-74101 (Patent Literature 1) discloses a method for producing pulp, wherein in a digestion step of pulping a lignocellulosic substance by treating it with an alkaline chemical solution or a chemical solution containing a sulfite, hydroxyanthracene or a hydroxyanthracene derivative is added as a digestion aid into a digestion liquid consisting of an alkaline chemical solution or a chemical solution containing a sulfite, and digestion of the lignocellulosic substance is performed by an alkaline method or a sulfite method. Furthermore, International Publication No. WO 95 / 29288 (Patent Literature 2) discloses a method for refining a pulp raw material by adding an aqueous dispersion of anthraquinone or the like. However, because of the problem of carcinogenicity of anthraquinones, hydroxyanthracene, and derivatives thereof, the effects on the human body cannot be eliminated, and considering greater safety, a digestion accelerator that does not use anthraquinone or the like is sought.

[0005] Furthermore, Japanese Unexamined Patent Application Publication No. 2009-185413 (Patent Literature 3) discloses a digestion aid containing an organic acid such as an aminocarboxylic acid or an oxycarboxylic acid and / or a salt thereof. However, since this digestion aid does not have a sufficient digestion accelerating effect and the quality of the obtained pulp is also not sufficient, a digestion accelerator that exhibits a more excellent digestion accelerating effect and that is also capable of obtaining pulp with more excellent quality is sought.[Citation List][Patent Literature]

[0006] [PTL 1] Japanese Unexamined Patent Application Publication No. Sho 53-74101 [PTL 2] International Publication No. WO 95 / 29288 [PTL 3] Japanese Unexamined Patent Application Publication No. 2009-185413 [Summary of Invention][Technical Problem]

[0007] The present invention has been made in view of the problems of the above-described conventional art, and an object of the present invention is to provide a digestion accelerator that is safer, is excellent in digestion accelerating effect, and is capable of obtaining pulp with more excellent quality, and a method for producing pulp using the same.[Solution to Problem]

[0008] As a result of diligent research conducted by the present inventors to achieve the above object, the present inventors found that a digestion accelerator containing, as a digestion accelerating component, at least one selected from the group consisting of casein, an amino acid having an aromatic ring or a heterocyclic ring, and salts thereof is excellent in digestion accelerating effect, and that by using this digestion accelerator, pulp with more excellent quality can be obtained, and have completed the present invention.

[0009] That is, the present invention provides the following aspects. [1] A digestion accelerator comprising 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. [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 in which a group containing a monocyclic aromatic ring or a monocyclic heterocyclic ring is bonded to the α-carbon. [4] The digestion accelerator according to [3], wherein the α-amino acid in which a group containing a monocyclic aromatic ring or a monocyclic heterocyclic ring is 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 digestion treatment using the digestion accelerator according to any one of [1] to [4]. [Advantageous Effects of Invention]

[0010] According to the present invention, it is possible to obtain a digestion accelerator that is safer, is excellent in digestion accelerating effect, and is capable of obtaining pulp with more excellent quality, and by using this digestion accelerator, it becomes possible to obtain pulp with more excellent quality.[Description of Embodiments]

[0011] Hereinafter, the present invention will be described in detail in accordance with preferred embodiments thereof. The following description of preferred embodiments is merely illustrative in nature and is not intended to limit the present invention, its application, or its uses.[Digestion Accelerator]

[0012] First, the digestion accelerator of the present invention will be described. The digestion accelerator of the present invention contains, as a digestion accelerating component, at least one selected from the group consisting of casein, an amino acid having an aromatic ring or a heterocyclic ring, and salts thereof.(Digestion Accelerating Component)

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

[0014] Casein is a type of phosphoprotein and is mainly contained in animal raw milk such as cow's milk, goat's milk, and camel's milk, and plant milk such as almond milk, coconut milk, and soy milk. In the present invention, such casein may be used in a state of being contained in the raw milk or the milk or in a state of being contained in skimmed milk powder that has been skimmed from the raw milk or the milk, but it is preferable to use casein separated from the raw milk or the milk from the viewpoint that the digestion accelerating effect is more excellent and that pulp with more excellent quality can be obtained by using it as a digestion accelerating component. Furthermore, in the present invention, industrially produced casein can also be used. Examples of the salt of casein 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 the amino acid having an aromatic ring or a heterocyclic ring include α-amino acids in which a group containing an aromatic ring or a heterocyclic ring is bonded to the α-carbon (the carbon to which a carboxyl group and an amino group are bonded). Examples of the group containing an aromatic ring or a heterocyclic ring include a benzyl group, a hydroxybenzyl group, and an imidazolylmethyl group. Among such amino acids having an aromatic ring or a heterocyclic ring, an amino acid having a monocyclic aromatic ring or a monocyclic heterocyclic ring is preferable, an α-amino acid in which a group containing a monocyclic aromatic ring or a monocyclic heterocyclic ring is bonded to the α-carbon is more preferable, an α-amino acid in which a group containing a monocyclic aromatic ring is bonded to the α-carbon is even more preferable, and more specifically, tyrosine and phenylalanine are preferable, and tyrosine is particularly preferable, from the viewpoint that the digestion accelerating effect is more excellent and that pulp with more excellent quality can be obtained by using it as a digestion accelerating component. 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 the 22 amino acids used in protein biosynthesis in cells and is contained in large amounts in foods such as sakura shrimp, cheese, whitebait, pork, chicken, and soy products. In the present invention, such tyrosine may be used in a state of being contained in the food or the like, but it is preferable to use tyrosine separated from the food or the like from the viewpoint that the digestion accelerating effect is more excellent and that pulp with more excellent quality can be obtained by using it as a digestion accelerating component. Furthermore, in the present invention, industrially produced tyrosine can also be used.

[0017] Phenylalanine is an aromatic amino acid having a benzyl group and one of the essential amino acids, and is contained in large amounts in foods such as dried sardines, cheese, sardines, soy products, pork, peanuts, and chicken, and artificial sweeteners. In the present invention, such phenylalanine may be used in a state of being contained in the food or the like, but it is preferable to use phenylalanine separated from the food or the like from the viewpoint that the digestion accelerating effect is more excellent and that pulp with more excellent quality can be obtained by using it as a digestion accelerating component. Furthermore, in the present invention, industrially produced phenylalanine can also be used.

[0018] In the present invention, among these digestion accelerating components, casein and salts thereof are particularly preferable from the viewpoint that the digestion accelerating effect is particularly excellent and that pulp with particularly excellent quality can be obtained by using it as a digestion accelerating component.(Digestion Accelerator)

[0019] The digestion accelerator of the present invention contains the digestion accelerating component, and from the viewpoint of digestion accelerating effect and cost, the content of the digestion accelerating component is preferably 1 to 100% by mass, more preferably 2 to 100% by mass, even more preferably 5 to 100% by mass, and particularly preferably 10 to 100% by mass.

[0020] In the digestion accelerator of the present invention, examples of other components included when the content of the digestion accelerating component is less than 100% by mass include additives such as known nonionic surfactants, known anionic surfactants, known cationic surfactants, known amphoteric surfactants, known mineral oil, known organic solvents, and known natural solvents such as orange oil. By blending such an additive, the permeability into a raw material such as a lignocellulosic material, the detergency, and the like of the digestion accelerating component are improved.

[0021] Furthermore, in the digestion accelerator of the present invention, from the viewpoint that the effects on the human body (possibility of carcinogenicity) cannot be eliminated and that safety is considered, it is particularly preferable that anthraquinone or the like and hydroxyanthracene or the like are not included. Examples of the 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 an aromatic ring of anthraquinone, and anthraquinone derivatives in which a part of the aromatic ring of anthraquinone and the anthraquinone derivatives is hydrogenated. Examples of the 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 an aromatic ring of hydroxyanthracene, and a hydroxyanthracene derivative in which a part of the aromatic ring of hydroxyanthracene and the hydroxyanthracene derivatives is hydrogenated.

[0022] From the viewpoint of digestion accelerating effect and cost, the amount of the digestion accelerator of the present invention used is preferably 0.0001 to 1.0% by mass, more preferably 0.001 to 0.5% by mass, and even more preferably 0.005 to 0.1% by mass with respect to the dry mass of the lignocellulosic material.

[0023] Furthermore, the digestion accelerator of the present invention may be used as it is, but may also be used by dissolving, emulsifying, or dispersing it in water or an organic solvent. The organic solvent is not particularly limited, but 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 digestion accelerator of the present invention may be used in combination with a known digestion accelerator (excluding the anthraquinones and the hydroxyanthracenes) such as saccharides like tannin, tannic acid, and glucose, and a quaternary ammonium having a long-chain alkyl group.[Method for Producing Pulp]

[0025] Next, the method for producing pulp of the present invention will be described. The method for producing pulp of the present invention includes a step of performing a digestion treatment using the digestion accelerator of the present invention.

[0026] A method for producing pulp generally includes a digestion step of pulping a raw material containing a lignocellulosic material by a digestion treatment (for example, a physical treatment performed by applying heat, pressure, or the like, or a chemical treatment performed using an alkali agent or the like), a washing step of washing the obtained crude pulp, and a bleaching step of bleaching the washed pulp. The method for producing pulp of the present invention is a method of performing a digestion treatment using the digestion accelerator of the present invention in the digestion step of such a general method for producing pulp, and a known digestion treatment method can be adopted except for using the digestion accelerator of the present invention, and a known washing step and a known bleaching step can be adopted as the washing step and the bleaching step.

[0027] The digestion treatment using the digestion accelerator of the present invention is also effective not only in the production of pulp, but also in the production of lignin components and hemicellulose components separated from the lignocellulosic material.

[0028] The lignocellulosic material used in the method for producing pulp of the present invention is not particularly limited, and examples thereof include not only wood (softwood (N-wood), hardwood (L-wood), etc.), but also non-wood materials such as straw, bagasse, reed, kenaf, mulberry, bamboo, herbaceous plants, and weeds.

[0029] The digestion treatment method that can be adopted in the method for producing pulp of the present invention is not particularly limited, and examples thereof include known digestion treatment methods such as an alkaline digestion method and a sulfite digestion method. Examples of the alkaline digestion method include a kraft digestion method, a soda digestion method, a soda-ash digestion method, and a polysulfide digestion method. Examples of the sulfite digestion method include an alkaline sulfite digestion method, a neutral sulfite digestion method, and a bisulfite digestion method. The chemical solution (digestion chemical solution) used in these digestion treatment methods is not particularly limited, and a chemical solution suitable for each digestion method can be used.

[0030] The equipment (digestion equipment) used for the digestion treatment is not particularly limited, and known digestion equipment can be used, and it may be a continuous type or a batch type. Furthermore, as the digestion system, an MCC method (modified continuous cooking method), an ITC method (isothermal cooking method), a Lo-solids method (reduction of solids in the digester), a BLI method (use of black liquor in an impregnation stage), or the like can also be adopted.

[0031] In the method for producing pulp of the present invention, the timing and method of addition of the digestion accelerator of the present invention are not particularly limited, but it is preferable to add the digestion accelerator in the digestion step of pulping and in a step prior thereto, and specifically, examples thereof include a method of directly adding the digestion accelerator to a digester before or during the digestion treatment, a method of mixing the digestion accelerator with a digestion chemical solution, a method of spraying the digestion accelerator onto the lignocellulosic material before digestion, and a method of adding the digestion accelerator to the circulating black liquor when the digestion equipment is a continuous type.

[0032] From the viewpoint of digestion accelerating effect and cost, the amount of the digestion accelerator used in the digestion treatment is preferably 0.0001 to 1.0% by mass, more preferably 0.001 to 0.5% by mass, and even more preferably 0.005 to 0.1% by mass with respect to the dry mass of the lignocellulosic material.

[0033] In the method for producing pulp of the present invention, the digestion accelerator of the present invention may be added as it is, but may also be added in a state of being dissolved, emulsified, or dispersed in water or an organic solvent. The organic solvent is not particularly limited, but 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 digestion accelerator of the present invention may be used in combination with a known digestion accelerator (excluding the anthraquinones and the hydroxyanthracenes) such as saccharides like tannin, tannic acid, and glucose, and a 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 from the viewpoint of digestibility, energy cost, and safety, it is preferably 50 to 300°C, and more preferably 80 to 250°C.

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

[0036] Furthermore, during the digestion treatment, oxygen may be introduced into the digester. The method for introducing oxygen is not particularly limited, and examples thereof include a method of setting the oxygen partial pressure high while adjusting the pressure of the digester and injecting oxygen or air under pressure into the digester, and a method of injecting oxygen or air under pressure during the supply of the lignocellulosic material or the supply of the digestion chemical solution. 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 thereof include pure oxygen, air, and a mixed gas of oxygen and air, but since increasing the pressure resistance of the digestion apparatus increases equipment costs, pure oxygen or a mixed gas of oxygen and air is preferable.

[0037] Furthermore, during the digestion treatment, as necessary, an oxidizing agent such as a peroxide (for example, hydrogen peroxide, potassium peroxide, etc.), a percarboxylic acid (for example, peracetic acid, etc.), or a hydrogen peroxide adduct (for example, sodium percarbonate, etc.) may be added to the digestion chemical solution to generate oxygen under digestion conditions.[Examples]

[0038] Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.(Example A1)[L-wood, Kraft Digestion Method](Kraft Digestion Treatment)

[0039] To a mixture of 50.0 g of L-wood wood chips (acacia) dried at 60°C for 24 hours as wood chips, 6.46 g of sodium sulfide pentahydrate (reagent) (3.00 g as a pure component of sodium sulfide), and 9.00 g of sodium hydroxide (reagent), tap water was added to make a total of 200 g. To the obtained aqueous solution, 0.0150 g (0.03% by mass with respect to the wood chips) of sodium caseinate (reagent, manufactured by Tokyo Chemical Industry Co., Ltd.) as a digestion accelerator was added, and the mixture was charged into a pot of a mini color dyeing tester (manufactured by Texam Giken Co., Ltd.), and a digestion treatment (kraft digestion treatment) was performed at 160°C for 120 minutes to obtain a mixture of pulp and undigested wood chips.(Washing Treatment)

[0040] This mixture was subjected to repeated shower washing with tap water on a two-stage sieve in which a stainless steel sieve with an opening of 75 µm was stacked on a stainless steel sieve with an opening of 710 µm, until the washing liquid became colorless.

[0041] After washing, the pulp remaining on the stainless steel sieve with an opening of 75 µm (hereinafter, referred to as "recovered pulp") and the wood chips remaining on the stainless steel sieve with an opening of 710 µm (hereinafter, referred to as "residual chips") were respectively recovered.[Residual Rate of Wood Chips]

[0042] The obtained residual chips were dried at 105°C for 10 hours, and then the mass thereof was measured. This mass was taken as the "Amount of residual chips after drying (g)," and the residual rate of wood chips was calculated by the following formula: The results are shown in Table 1.[Pulp Yield]

[0043] The obtained recovered pulp was dried at 105°C for 10 hours, and then the mass thereof was measured. This mass was taken as the "Amount of recovered pulp after drying (measured value) (g)." Furthermore, assuming that the residual chips are subjected to digestion treatment again, "Amount of residual chips after drying (g) / 2" was added as a yield portion to the measured "Amount of recovered pulp after drying (measured value) (g)", and this was taken as the "Amount of recovered pulp after drying (corrected value) (g)", as in the following formula: The pulp yield (%) was calculated by the following formula:

[0044] The results are shown in Table 1.(Preparation of Test Paper)

[0045] Recovered pulp separately obtained in the same manner as the above-described digestion treatment and washing treatment was handsheeted under the condition of a basis weight of 150 g / m 2< using a round paper machine ("Standard Sheet Machine Papermaking Device" manufactured by Kumagai Riki Kogyo Co., Ltd.) in accordance with JIS P8222:2015 "Pulps - Preparation of laboratory sheets for physical testing - Part 1: Conventional sheet-former method." Thereafter, a press treatment was performed at a pressure of 700 kPa for 5 minutes, and the sheet was dried at 105°C for 5 minutes using a drum dryer to obtain a test paper.[Kappa Number]

[0046] The Kappa number of the recovered pulp was measured using the test paper in accordance with JIS P8211:2011 "Pulps - Determination of Kappa number." The results are shown in Table 1.[Whiteness]

[0047] The whiteness of the test paper was measured using a spectrophotometric colorimeter ("Color Touch PC" manufactured by Technidyne Corporation) in accordance with JIS P8148:2018 "Paper, board and pulps - Measurement of diffuse blue reflectance factor - Indoor daylight conditions (ISO brightness)" under the conditions of a C illuminant and a measurement angle of 2°. The results are shown in Table 1.(Examples A2 to A11)

[0048] A digestion treatment and a washing treatment of L-wood wood chips (acacia) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example A1, except that the type and amount of the compound shown in Table 1 were used as the digestion accelerator. These results are shown in Table 1.(Comparative Example A1)

[0049] A digestion treatment and a washing treatment of L-wood wood chips (acacia) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example A1, except that no digestion accelerator was added. These results are shown in Table 1.(Comparative Examples A2 to A5)

[0050] A digestion treatment and a washing treatment of L-wood wood chips (acacia) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example A1, except that the type and amount of the compound shown in Table 1 were used as the digestion accelerator. These results are shown in Table 1. [Table 1]L-wood Kraft Digestion MethodDigestion AcceleratorWood Chip Residual Rate [%]Pulp Yield [%]Kappa NumberWhitenessTypeAmount [%] (relative to wood chip amount)Example A1Sodium caseinate0.030.0350.615.238.3Example A2Casein (milk-derived)0.0050.0750.315.538.1Example A3Casein (milk-derived)0.010.0650.415.338.2Example A4Casein (milk-derived)0.030.0350.615.138.2Example A5Casein (milk-derived)0.10.0150.714.938.4Example A6L-(-)-Tyrosine0.0050.1450.116.137.8Example A7L-(-)-Tyrosine0.010.1250.216.037.9Example A8L-(-)-Tyrosine0.030.0950.215.738.1Example A9L-(-)-Tyrosine0.10.0750.415.538.1Example A10DL-Tyrosine0.030.0750.315.838.0Example A11L-Phenylalanine0.030.1550.016.237.8Comp. Ex. A1None00.3949.118.337.0Comp. Ex. A2Gelatin0.030.2349.717.237.5Comp. Ex. A3L-Alanine0.030.2749.417.337.3Comp. Ex. A4L-Valine0.030.2749.517.237.3Comp. Ex. A5L-Leucine0.030.2949.517.237.4Sodium caseinate: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. Casein (milk-derived): reagent, manufactured by FUJIFILM Wako Pure Chemical Corporation L-(-)-Tyrosine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. DL-Tyrosine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Phenylalanine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. Gelatin: reagent, manufactured by FUJIFILM Wako Pure Chemical Corporation L-Alanine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Valine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Leucine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. (Example B1)[N-wood, Kraft Digestion Method]

[0051] A digestion treatment and a washing treatment were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example A1, except that 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 8.61 g (4.00 g as a pure component of sodium sulfide), the amount of sodium hydroxide was changed to 12.0 g, and the amount of sodium caseinate was changed to 0.00250 g (0.005% by mass with respect to the wood chips). These results are shown in Table 2.(Examples B2 to B11)

[0052] A digestion treatment and a washing treatment of N-wood wood chips (pine) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example B1, except that the type and amount of the compound shown in Table 2 were used as the digestion accelerator. These results are shown in Table 2.(Comparative Example B1)

[0053] A digestion treatment and a washing treatment of N-wood (softwood) wood chips (pine) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example B1, except that no digestion accelerator was added. These results are shown in Table 2.(Comparative Examples B2 to B5)

[0054] A digestion treatment and a washing treatment of N-wood wood chips (pine) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example B1, except that the type and amount of the compound shown in Table 2 were used as the digestion accelerator. These results are shown in Table 2. [Table 2]N-wood Kraft Digestion MethodDigestion AcceleratorWood Chip Residual Rate [%]Pulp Yield [%]Kappa NumberWhitenessTypeAmount [%] (relative to wood chip amount)Example B1Sodium caseinate0.0050.0651.827.335.2Example B2Sodium caseinate0.010.0351.927.135.3Example B3Sodium caseinate0.030.0252.026.735.3Example B4Sodium caseinate0.10.0152.126.435.5Example B5Casein (milk-derived)0.030.0252.026.835.4Example B6L-(-)-Tyrosine0.030.0751.727.535.1Example B7DL-Tyrosine0.0050.1151.528.134.9Example B8DL-Tyrosine0.010.0951.627.935.0Example B9DL-Tyrosine0.030.0751.727.735.1Example B10DL-Tyrosine0.10.0551.827.135.3Example B11L-Phenylalanine0.030.1351.328.334.9Comp. Ex. B1None00.3350.230.334.1Comp. Ex. B2Gelatin0.030.1950.729.334.5Comp. Ex. B3L-Alanine0.030.2150.529.534.4Comp. Ex. B4L-Valine0.030.2250.529.534.3Comp. Ex. B5L-Leucine0.030.2250.429.634.4Sodium caseinate: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. Casein (milk-derived): reagent, manufactured by FUJIFILM Wako Pure Chemical Corporation L-(-)-Tyrosine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. DL-Tyrosine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Phenylalanine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. Gelatin: reagent, manufactured by FUJIFILM Wako Pure Chemical Corporation L-Alanine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Valine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Leucine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. (Example C1)[L-wood, Polysulfide Digestion Method](Polysulfide Digestion Treatment)

[0055] To a mixture of 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 as a pure component of sodium sulfide), 9.00 g of sodium hydroxide (reagent), and 3.33 g of an aqueous solution of sodium tetrasulfide (manufactured by Nagao & Co., Ltd.) (1.00 g as a pure component of sodium tetrasulfide), tap water was added to make a total of 200 g. To the obtained aqueous solution, 0.0150 g (0.03% by mass with respect to the wood chips) of sodium caseinate (reagent, manufactured by Tokyo Chemical Industry Co., Ltd.) as a digestion accelerator was added, and the mixture was charged into a pot of a mini color dyeing tester (manufactured by Texam Giken Co., Ltd.), and a digestion treatment (polysulfide digestion treatment) was performed at 160°C for 120 minutes to obtain a mixture of pulp and undigested wood chips.(Washing Treatment)

[0056] This mixture was subjected to a washing treatment in the same manner as in Example A1, and recovered pulp and residual chips were respectively recovered.

[0057] In the same manner as in Example A1, using the obtained residual chips and recovered pulp, the residual rate of wood chips and the pulp yield were calculated, and the Kappa number of the recovered pulp and the whiteness of the test paper were measured. These results are shown in Table 3.(Examples C2 to C3)

[0058] A digestion treatment and a washing treatment of L-wood wood chips (acacia) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example C1, except that the type and amount of the compound shown in Table 3 were used as the digestion accelerator. These results are shown in Table 3.(Comparative Example C1)

[0059] A digestion treatment and a washing treatment of L-wood wood chips (acacia) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example C1, except that no digestion accelerator was added. These results are shown in Table 3.(Comparative Examples C2 to C5)

[0060] A digestion treatment and a washing treatment of L-wood wood chips (acacia) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example C1, except that the type and amount of the compound shown in Table 3 were used as the digestion accelerator. These results are shown in Table 3. [Table 3]L-wood Polysulfide Digestion MethodDigestion AcceleratorWood Chip Residual Rate [%]Pulp Yield [%]Kappa NumberWhitenessTypeAmount [%] (relative to wood chip amount)Example C1Sodium caseinate0.030.0350.515.038.4Example C2L-(-)-Tyrosine0.030.0850.215.538.1Example C3L-Phenylalanine0.030.1650.016.037.9Comp. Ex. C1None00.4049.118.037.1Comp. Ex. C2Gelatin0.030.2649.616.837.4Comp. Ex. C3L-Alanine0.030.2849.416.937.3Comp. Ex. C4L-Valine0.030.2849.516.937.2Comp. Ex. C5L-Leucine0.030.3049.417.037.3Sodium caseinate: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-(-)-Tyrosine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Phenylalanine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. Gelatin: reagent, manufactured by FUJIFILM Wako Pure Chemical Corporation L-Alanine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Valine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Leucine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. (Example D1)[N-wood, Kraft Digestion Method]

[0061] A digestion treatment and a washing treatment were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example C1, except that 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 as a pure component of sodium sulfide), the amount of sodium hydroxide was changed to 12.0 g, the amount of the aqueous solution of sodium tetrasulfide was changed to 4.33 g (1.30 g as a pure component of sodium tetrasulfide), and 0.0150 g (0.03% by mass with respect to the wood chips) of casein (milk-derived) (reagent, manufactured by FUJIFILM Wako Pure Chemical Corporation) was used as the digestion accelerator. These results are shown in Table 4.(Examples D2 to D3)

[0062] A digestion treatment and a washing treatment of N-wood wood chips (pine) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example D1, except that the type and amount of the compound shown in Table 4 were used as the digestion accelerator. These results are shown in Table 4.(Comparative Example D1)

[0063] A digestion treatment and a washing treatment of N-wood (softwood) wood chips (pine) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example D1, except that no digestion accelerator was added. These results are shown in Table 4.(Comparative Examples D2 to D5)

[0064] A digestion treatment and a washing treatment of N-wood wood chips (pine) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example D1, except that the type and amount of the compound shown in Table 4 were used as the digestion accelerator. These results are shown in Table 4. [Table 4]N-wood Polysulfide Digestion MethodDigestion AcceleratorWood Chip Residual Rate [%]Pulp Yield [%]Kappa NumberWhitenessTypeAmount [%] (relative to wood chip amount)Example D1Casein (milk-derived)0.030.0352.126.535.6Example D2DL-Tyrosine0.030.0751.727.435.2Example D3L-Phenylalanine0.030.1251.428.134.9Comp. Ex. D1None00.3350.230.334.1Comp. Ex. D2Gelatin0.030.2150.628.934.5Comp. Ex. D3L-Alanine0.030.2350.229.234.3Comp. Ex. D4L-Valine0.030.2450.329.334.4Comp. Ex. D5L-Leucine0.030.2450.329.134.3Casein (milk-derived): reagent, manufactured by FUJIFILM Wako Pure Chemical Corporation DL-Tyrosine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Phenylalanine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. Gelatin: reagent, manufactured by FUJIFILM Wako Pure Chemical Corporation L-Alanine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Valine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd. L-Leucine: reagent, manufactured by Tokyo Chemical Industry Co., Ltd.

[0065] As shown in Tables 1 to 4, in the cases where at least one compound of casein and salts thereof, tyrosine, and phenylalanine was used as the digestion accelerator (Examples), it was confirmed that, compared to the cases where gelatin, alanine, valine, or leucine was used (Comparative Examples), in both L-wood and N-wood wood chips and in both the kraft digestion and polysulfide digestion methods, the residual rate of wood chips becomes low, the pulp yield becomes high, the Kappa number becomes low, and the whiteness becomes high.[Industrial Applicability]

[0066] As described above, according to the present invention, it becomes possible to obtain a digestion accelerator that is safer, is excellent in digestion accelerating effect, and is capable of obtaining pulp with more excellent quality. Therefore, since the method for producing pulp of the present invention uses such a digestion accelerator, lignocellulosic materials can efficiently pulped and the method is also useful as a method capable of obtaining pulp with more excellent quality.

Examples

examples

[Examples]

[0038]Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

example a1

(Example A1)

[L-wood, Kraft Digestion Method]

(Kraft Digestion Treatment)

[0039]To a mixture of 50.0 g of L-wood wood chips (acacia) dried at 60°C for 24 hours as wood chips, 6.46 g of sodium sulfide pentahydrate (reagent) (3.00 g as a pure component of sodium sulfide), and 9.00 g of sodium hydroxide (reagent), tap water was added to make a total of 200 g. To the obtained aqueous solution, 0.0150 g (0.03% by mass with respect to the wood chips) of sodium caseinate (reagent, manufactured by Tokyo Chemical Industry Co., Ltd.) as a digestion accelerator was added, and the mixture was charged into a pot of a mini color dyeing tester (manufactured by Texam Giken Co., Ltd.), and a digestion treatment (kraft digestion treatment) was performed at 160°C for 120 minutes to obtain a mixture of pulp and undigested wood chips.

(Washing Treatment)

[0040]This mixture was subjected to repeated shower washing with tap water on a two-stage sieve in which a stainless steel sieve with an opening of 75 µm wa...

examples a2 to a11

(Examples A2 to A11)

[0048]A digestion treatment and a washing treatment of L-wood wood chips (acacia) were performed, and the residual rate of wood chips and the pulp yield were calculated and the Kappa number of the recovered pulp and the whiteness of the test paper were measured using the obtained residual chips and recovered pulp, in the same manner as in Example A1, except that the type and amount of the compound shown in Table 1 were used as the digestion accelerator. These results are shown in Table 1.

Claims

1. A digestion accelerator comprising 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.

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 in which a group containing a monocyclic aromatic ring or a monocyclic heterocyclic ring is bonded to the α-carbon.

4. The digestion accelerator according to claim 3, wherein the α-amino acid in which a group containing a monocyclic aromatic ring or a monocyclic heterocyclic ring is 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 digestion treatment using the digestion accelerator according to any one of claims 1 to 4.

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