Method for producing glycol lignin

Abstract

To provide a method for producing glycol lignin that enables safe plant-scale production with stable quality at reduced cost and energy compared with conventional methods, the glycol lignin being suitable as a raw material for high value-added materials.SOLUTION: A method for producing glycol lignin comprises a step (a) of, in a mixing device having at least two stirring blades and a vessel, kneading lignocellulose and at least one glycol-based solvent selected from the group consisting of polyethylene glycol, diethylene glycol, ethylene glycol, propylene glycol, polypropylene glycol, glycerin, and polyglycerin, in the presence of an acid catalyst under normal pressure, while applying shear stress generated by rotation of the at least two stirring blades, wherein an amount of the glycol-based solvent is less than 2 pts.wt. relative to 1 pt.wt. of the lignocellulose.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing glycol lignin. [Background technology]

[0002] Lignin is one of the three main components of biomass and the second most abundant organic polymer on earth. Lignin is separated from biomass materials during the chemical pulping process and bioethanol pretreatment process, and is fractionated in waste liquid (black liquor) as a lignin decomposition product. However, due to issues with deterioration and stability, there are few uses other than as a heat source, and effective uses of lignin and its derivatives as materials are being explored.

[0003] Lignin decomposition products obtained by solvolysis of lignocellulose using glycol-based agents such as polyethylene glycol and diethylene glycol with concentrated sulfuric acid as a catalyst are glycol lignins derivatized with glycol-based agents, which are endowed with thermal processability while retaining the inherent properties of lignin. For example, a method for producing carbon fibers and activated carbon fibers using glycol lignins obtained in this manner has been disclosed (Patent Document 1). Because glycol lignins obtained by such acid solvolysis methods are endowed with thermal processability, they are expected to be used as raw materials for high-value-added materials such as engineering plastics, various thermoplastic resins, films, electronic substrates, fiber reinforcements, various adhesives, carbon fibers, various carbon materials, chemical admixtures for concrete, dispersants, and various surfactants, in addition to carbon fibers.

[0004] Meanwhile, the largest amount of unused biomass in Japan is in rural areas, at approximately 20 million m per year. 3It is said that forest residues are generated in large quantities. Approximately 30% of forest residues is lignin, and there is a need to utilize this. In addition, there is the issue of transportation costs for forest residues, and there is a need to process forest residues locally. If high-value-added glycol lignin could be safely produced from forest residues in rural areas where they are generated, it would not only be an effective use of lignin, but would also contribute to the creation of new industries and regional revitalization in rural areas.

[0005] Patent Document 2 discloses a method and system for producing glycol lignin, which can be used as a raw material for high-value-added materials, safely on a plant scale. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-147768 [Patent Document 2] Japanese Patent Application Publication No. 2017-197517 Summary of the Invention [Problem to be solved by the invention]

[0007] The manufacturing industry is constantly required to balance product quality with cost, that is, to manufacture products that offer high cost performance.

[0008] An object of the present invention is to provide a method for producing glycol lignin, which can produce glycol lignin, which can be used as a raw material for high-value-added materials, safely and with stable quality on a plant scale at lower cost and with less energy than conventional production methods.

[0009] In conventional glycol lignin production methods, such as those disclosed in Patent Documents 1 and 2, lignocellulose is subjected to solvolysis by heat treatment in a glycol-based solvent in the presence of an acid catalyst. Here, "solvolysis" refers to a chemical reaction that occurs when a substance is decomposed in an organic solvent reagent. The decomposition of the substance simultaneously chemically bonds the decomposed substance with the solvent reagent used (i.e., the solvent molecules are added to the decomposition product). Through the solvolysis reaction, sugar components such as cellulose in lignocellulose are decomposed into smaller molecules. At the same time, numerous hydrophilic groups, such as alcoholic hydroxyl groups and / or polyoxyalkylene groups, derived from the glycol-based solvent are introduced into the lignin in the lignocellulose, producing glycol lignin. In conventional glycol lignin production methods, the lignocellulose is completely immersed in the glycol-based solvent to ensure efficient solvolysis. For example, in Patent Document 2, the solvolysis reaction is carried out in 5 parts by weight of glycol-based solvent per 1 part by mass (bone dry weight) of lignocellulose.

[0010] The present inventors have investigated ways to reduce the cost of glycol lignin production and have found that even when the amount of glycol solvent relative to lignocellulose is significantly reduced, glycol lignin can be efficiently produced by kneading lignocellulose and glycol solvent while applying strong shear stress. Furthermore, they have found that glycol lignin produced by this method has stable quality regardless of the form of the raw material lignocellulose.

[0011] Specific means for solving the above problems are as follows. Embodiments of the present invention include the following method for producing glycol lignin. [1] (a) A method for producing a lignocellulose mixture comprising: kneading, in a mixing device having at least two agitating blades and a container, lignocellulose with at least one glycol-based solvent selected from the group consisting of polyethylene glycol, diethylene glycol, ethylene glycol, propylene glycol, polypropylene glycol, glycerin, and polyglycerin in the presence of an acid catalyst under normal pressure while applying shear stress generated by the rotation of the at least two agitating blades; The amount of the glycol-based solvent is less than 2 parts by weight relative to 1 part by weight of the lignocellulose. Method for producing glycol lignin. [2] The method for producing glycol lignin according to [1], wherein the mixing device is a planetary mixer, a kneader, a pug mill type mixer, a Lödige mixer, or an Apex mixer. [3] The method for producing glycol lignin according to [1] or [2], wherein the kneaded product obtained in the kneading step is in a solid state as a whole. [4] (b) mixing the kneaded product obtained in the kneading step with an alkaline aqueous solution and separating a solution fraction containing glycol lignin and a solid fraction from the resulting mixture; (c) acidifying the solution fraction with an acid to obtain glycol lignin as a precipitate; (d) separating a glycol lignin precipitate from the acidified solution fraction; (e) collecting the separated solution after separating the glycol lignin precipitate, and neutralizing the collected solution by adding an alkali to the collected solution; (f) heating the neutralized solution to concentrate it to a water content of 10% or less and recovering the glycol-based solvent; (g) separating the alkali metal salt crystals formed by the concentration; The method for producing glycol lignin according to any one of [1] to [3] above, further comprising: [5] The glycol-based solvent recovered in the step (f) is reused as the glycol-based solvent in the step (a). The method for producing glycol lignin according to [4] above. [Effects of the Invention]

[0012] According to an aspect of the present invention, there is provided a method for producing glycol lignin, which can produce glycol lignin, which can be used as a raw material for high-value-added materials, safely and with stable quality on a plant scale at lower cost and with less energy than conventional production methods. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Method of producing glycol lignin] A method for producing glycol lignin according to one embodiment of the present invention comprises: (a) a step of kneading lignocellulose with at least one glycol solvent selected from the group consisting of polyethylene glycol, diethylene glycol, ethylene glycol, propylene glycol, polypropylene glycol, glycerin, and polyglycerin in a mixing device having at least two agitating blades and a container, in the presence of an acid catalyst under normal pressure, while applying shear stress generated by the rotation of the at least two agitating blades (hereinafter, this may be referred to as "kneading step (a)" or simply "step (a)"); The amount of the glycol-based solvent is less than 2 parts by weight relative to 1 part by weight of the lignocellulose. A method for producing glycol lignin.

[0014] The type of lignocellulose used in the kneading step (a) is not particularly limited, and examples include conifers such as cedar, fir, cypress, and pine; broad-leaved trees such as eucalyptus, acacia, birch, beech, and oak; rice straw; grains; bagasse; bamboo; kenaf; and herbaceous plants such as reeds. Unused and recycled woody biomass, such as thinned wood, forest residues, sawmill residues, construction waste, and pruned branches and leaves, is desirable from the perspective of resource availability and effective utilization. Lignocellulose may be in the form of chips or powder. The pulverizing method for converting lignocellulose into powder is not particularly limited, and conventional mills such as cutting chippers, crushing chippers, cutter mills, vibration mills, and hammer mills can be used. The moisture content of the lignocellulose may be adjusted to 50% or less, preferably 20% or less.

[0015] The glycol-based solvent used in the kneading step (a) is at least one selected from polyethylene glycol, diethylene glycol, ethylene glycol, propylene glycol, polypropylene glycol, glycerin, and polyglycerin. In the kneading step (a), a large number of hydrophilic groups, such as alcoholic hydroxyl groups and / or polyoxyalkylene groups, derived from the glycol-based solvent are introduced into the lignin in the lignocellulose, producing glycol lignin. The glycol-based solvent can be selected depending on the desired performance of the glycol lignin, and two or more glycol-based solvents may be used in combination. As the polyethylene glycol, polyethylene glycols with various average molecular weights can be selected depending on the thermal melting properties of the resulting glycol lignin. For example, polyethylene glycols with an average molecular weight of 100 to 2000, preferably 200 to 600, can be used. These glycol-based solvents are low in flammability and safe, making them ideal for use in small bench plants in local areas.

[0016] In one embodiment, the glycol-based solvent may be polyethylene glycol. In one embodiment, the glycol-based solvent may be glycerin. In one embodiment, the glycol-based solvent may be a combination of polyethylene glycol and glycerin. In one embodiment, the glycol-based solvent is a combination of polyethylene glycol and glycerin, and the ratio of polyethylene glycol to glycerin ([polyethylene glycol]:[glycerin]) may be 1 to 99:99 to 1 by weight.

[0017] Examples of the acid catalyst used in the kneading step (a) include, but are not limited to, hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, etc., and sulfuric acid is preferred. The amount of the acid catalyst added is preferably 0.1 to 2.0% by weight, more preferably 0.2 to 1.5% by weight, based on the weight of the glycol solvent.

[0018] Lignocellulose and a glycol-based solvent are kneaded under an acid catalyst at atmospheric pressure in a mixer equipped with at least two agitator blades and a container, while applying shear stress generated by the rotation of the at least two agitator blades. The amount of glycol-based solvent is less than 2 parts by weight per 1 part by weight of lignocellulose, e.g., 0.5 to 2 parts by weight, e.g., 0.5 to 1.5 parts by weight, e.g., 0.8 to 1.2 parts by weight. By using a mixer equipped with at least two agitator blades and a container, a strong shear stress can be applied to the lignocellulose, even when the amount of glycol-based solvent is significantly reduced compared to conventional amounts, thereby enabling effective kneading of the lignocellulose and glycol-based solvent. Note that, in this specification, "kneading" refers to the process of dispersing powder particles while coating them with a liquid or paste, as described in "Powder Technology Glossary, Second Edition," edited by the Society of Powder Technology (Nikkan Kogyo Shimbun, 2000). This kneading process solvolyzes lignocellulose with the glycol-based solvent to the same extent as when lignocellulose is cooked in a large amount of glycol-based solvent, and hydrophilic groups such as alcoholic hydroxyl groups and / or polyoxyalkylene groups derived from the glycol-based solvent are efficiently introduced into the lignin in the lignocellulose, producing glycol lignin.

[0019] Reducing the amount of glycol-based solvent used not only reduces material costs but also allows for an increased amount of lignocellulose to be processed in a mixing device at one time, thereby increasing the amount of glycol lignin produced per process, contributing to lower costs and energy consumption in the production process. Furthermore, in conventional production methods, uneven reaction may occur depending on the form and particle size of the lignocellulose used for solvolysis. In the production method of this embodiment, when kneading is performed while applying strong shear stress, chip-like lignocellulose and large-particle-sized particulate lignocellulose are crushed by the shear stress and converge to a uniform particle size. As a result, uneven solvolysis reaction during kneading is suppressed, resulting in the production of glycol lignin of more stable quality.

[0020] The mixing device having at least two stirring blades and a container includes a device having one or more stirring blades and a container fixed to each of two or more rotating shafts, and a device having two or more stirring blades and a container fixed to one rotating shaft. The shape of the stirring blade is determined depending on the type of mixing device. The shape of the container is determined depending on the type of mixing device and can be vertical or horizontal. Since the kneading step (a) is performed under normal pressure, the container does not have to be a pressure-resistant container.

[0021] Examples of devices having one or more impellers and a container attached to each of two or more rotating shafts include, but are not limited to, planetary mixers, twin-shaft kneaders, and pug mill mixers. Planetary mixers have two or three rotating shafts, each with a frame-type impeller attached. By revolving and rotating the frame-type impeller within the container, shear stress can be applied to the materials being processed between the inner wall and the bottom of the container. Twin-shaft kneaders rotate one or more impellers attached to each of two rotating shafts within the container, creating shear stress between the container and the impellers to knead the materials. Pug mill mixers, which are sometimes used in the production of asphalt mixtures, have two rotating shafts, each with multiple impellers attached, and by rotating the two shafts in opposite directions, shear stress is applied to the materials to knead them.

[0022] Examples of devices with two or more mixing blades and a container fixed to a single rotating shaft include, but are not limited to, Loedige mixers and Apex mixers. Loedige mixers and Apex mixers have two or more mixing blades with special shapes, such as plow-shaped or sawtooth-shaped, fixed to a single rotating shaft in a horizontal container, and the materials are mixed by the three-dimensional flow and shear stress caused by the mixing blades. These Loedige mixers and Apex mixers can be equipped with an additional high-speed chopper to achieve a more advanced material grinding effect.

[0023] In the kneading step (a), the rotation speed of the at least two stirring blades can be appropriately set depending on the type of mixer used. The rotation speed of the at least two stirring blades can be, for example, 5 rpm or more, for example, 5 to 200 rpm, for example, 10 to 200 rpm, or for example, 20 to 180 rpm.

[0024] In the kneading step (a), for example, a glycol-based solvent and an acid catalyst are placed in a mixing device and mixed by stirring beforehand. Then, lignocellulose is added, and the temperature inside the mixing device is set to 120 to 200°C, preferably 130 to 180°C, and the mixture is kneaded by rotating the stirring blades for 60 to 240 minutes, preferably 60 to 200 minutes. The time required for the temperature rise inside the container is not particularly limited, but may be, for example, 30 to 120 minutes. Because the kneading step (a) is performed under normal pressure, it is possible to directly observe the inside of the mixing device through a viewing window and sample the contents during kneading. This point symbolizes the simplicity and safety of the production method of this embodiment.

[0025] The kneaded product obtained in the kneading step (a) is in a solid state as a whole, for example, in a clayey state. In conventional methods for producing glycol lignin, a reaction mixture of lignocellulose and a glycol-based solvent is obtained in a liquefied state, and after mixing with an alkaline aqueous solution, a solution fraction containing glycol lignin and a solid fraction mainly composed of cellulose and hemicellulose are separated. On the other hand, in the production method of this embodiment, a kneaded product is obtained in a solid state as a whole, but even if the kneaded product is in a solid state, by mixing with an alkaline aqueous solution, glycol lignin is extracted into the alkaline aqueous solution, resulting in a solution fraction containing glycol lignin. In this way, glycol lignin can be isolated.

[0026] The production method of this embodiment may include the following steps (b) to (g) from the viewpoint of producing glycol lignin at low cost and with low energy on a plant scale. (b) mixing the kneaded product obtained in the kneading step with an alkaline aqueous solution and separating a solution fraction containing glycol lignin and a solid fraction from the resulting mixture; (c) acidifying the solution fraction with an acid to obtain glycol lignin as a precipitate; (d) separating a glycol lignin precipitate from the acidified solution fraction; (e) collecting the separated solution after separating the glycol lignin precipitate, and neutralizing the collected solution by adding an alkali to the collected solution; (f) a step of concentrating the neutralized solution to a water content of 10% or less by heating the neutralized solution to recover the glycol-based solvent; and (g) A step comprising separating the alkali metal salt crystals produced by the concentration.

[0027] After the kneading step (a), (b) the kneaded product obtained in the kneading step is mixed with an alkaline aqueous solution, and the resulting mixture is separated into a solution fraction containing glycol lignin and solids. After the kneading step, the mixer is cooled, and when the internal temperature reaches 40°C or below, an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide is added to the mixer and stirred again. Alternatively, the kneaded product may be transferred to a mixer other than the mixer used in the kneading step (a), after being cooled to approximately ambient temperature. An alkaline aqueous solution such as sodium hydroxide or potassium hydroxide may then be added to the mixer and stirred. By adjusting the pH to 10.5 or higher, glycol lignin is extracted into the alkaline aqueous solution, resulting in a solution fraction containing glycol lignin. The solution fraction containing glycol lignin is then separated from pulp, a solid component primarily composed of cellulose and hemicellulose. Separators for this separation include, but are not limited to, filter presses, vacuum filters, belt presses, and centrifuges, with filter presses being preferred. After separation, the pulp contains a small amount of glycol lignin-containing solution fraction, which can be washed with water to recover the remaining glycol lignin. After washing, the washed water can be combined with the glycol lignin-containing solution fraction and subjected to step (c) described below.

[0028] After step (b), (c) the solution fraction is acidified with an acid to obtain glycol lignin as a precipitate. The pH of the solution fraction is adjusted to 2 to 5, preferably 2 to 3, by adding an acid, and the solution is stirred at room temperature or under heating, preferably at 50°C or higher, to obtain glycol lignin as a precipitate. Examples of acids that can be used include sulfuric acid, hydrochloric acid, phosphoric acid, and acetic acid, with sulfuric acid being preferred. Glycol lignin particles are very fine, but when the solution fraction is acidified with an acid and the acidic solution is heated to 50°C or higher, glycol lignin aggregates and the particle size increases, making it easier to separate the glycol lignin by filtration, as described below. The upper limit of the heating temperature can be, for example, 60°C to 70°C.

[0029] After step (c), (d) the glycol lignin precipitate is separated from the acidified solution fraction by filtration, centrifugation, or the like. Filtration can be performed using a continuous filtration device such as a belt filter. Solid-liquid separation is achieved by introducing a suspension containing glycol lignin into the upstream part of a moving filter cloth installed in the belt filter, and at the same time, unreacted glycol-based solvents and salts can be removed by introducing wash water downstream of the moving filter cloth, thereby purifying the glycol lignin. The filtrate (separated liquid) containing the wash water is recovered and used in step (e) described below. In the case of centrifugation, the lignin suspension is continuously fed from the first pH adjustment tank to a centrifugal separator, such as a cylindrical centrifuge, to separate the precipitate. When a cylindrical centrifuge is used, the solids containing glycol lignin are deposited in a cylindrical shape, and the separated liquid containing glycol-based solvents, water, and acid-soluble glycol lignin is continuously discharged and collected in a second pH adjustment tank (separated liquid A). The solids separated by centrifugation are suspended in water, washed, and returned to the first pH adjustment tank. By centrifuging again, unreacted glycol-based solvents and salts can be removed, and the glycol lignin can be purified. The water used in this purification is also continuously discharged and collected in a second pH adjustment tank (separated liquid B). These separated liquids are used in step (e), described below. In conventional production methods, a large amount of glycol-based solvent is used for solvolysis, resulting in a large amount of unreacted glycol-based solvent after the solvolysis reaction. Therefore, a large amount of water is required to remove the unreacted glycol-based solvent adhering to the separated glycol lignin. In the production method of this embodiment, the amount of glycol-based solvent used in the kneading step (a) is significantly reduced, thereby significantly reducing the amount of water used for purifying the glycol lignin.

[0030] After step (d), (e) the separated solution after separation of the glycol lignin precipitate is collected, and an alkali is added to the collected solution to neutralize it. Because the separated solution after separation of the glycol lignin precipitate is an acidic aqueous solution with a pH of 2.0 to 5.5, if it is directly subjected to the solvent recovery step in step (f) described below, problems arise such as pipe blockage due to deposition of glycol lignin contained in the acidic aqueous solution and deterioration of the solvent (increase in molecular weight due to condensation between solvent molecules). Therefore, in step (e), an alkali such as sodium hydroxide or potassium hydroxide is added to the collected solution to neutralize the pH of the collected solution to 7 to 8, preferably about 7.5, and then the collected solution is subjected to step (f) described below.

[0031] In this production method, the solvent recovered in step (f) can be reused as the glycol-based solvent in step (a), as described below. In this case, repeated reuse reduces the hydroxyl value of the recovered solvent and increases its viscosity. This is thought to be due to the binding of soluble lignin decomposition products, impurities, and the like to some of the hydroxyl groups of the recovered solvent. Reusing such a recovered solvent as the glycol-based solvent in step (a) reduces the solvolysis efficiency and reduces the yield of glycol lignin. Therefore, in step (e), it is preferable to collect the separated solution after separating the glycol lignin precipitate, add an acid to the collected solution as needed, and then heat the collected solution before adding an alkali such as sodium hydroxide or potassium hydroxide to the collected solution (solution heating regeneration treatment step). This allows the soluble lignin decomposition products and impurities bound to some of the hydroxyl groups of the solvent by hydrolysis to be released from the hydroxyl groups, thereby regenerating the solvent. By including this solution heating regeneration treatment step, the solvent recovered in step (f) can be repeatedly reused as the glycol-based solvent in step (a) without reducing the yield of glycol lignin.

[0032] In the solution heating regeneration treatment step, an acid is added to the accumulated solution as needed. Because the accumulated solution is an acidic aqueous solution with a pH of 2.0 to 5.5, the hydrolysis reaction proceeds by heating the accumulated solution as is. However, an acid is added as needed to adjust the pH of the accumulated solution to 0 to 6, preferably 1 to 4, and more preferably about 1. Examples of acids that can be used include sulfuric acid, hydrochloric acid, phosphoric acid, and acetic acid, with sulfuric acid being preferred. The heating temperature varies depending on conditions such as the acid concentration and pressure, but is preferably 70 to 180°C, preferably 100 to 140°C, or the temperature at which the solution boils. The heating time varies depending on conditions such as the acid concentration, pressure, and heating temperature, but is preferably 30 to 240 minutes, more preferably 60 to 90 minutes. The heat treatment can be performed under normal pressure or under pressure. The solution heating regeneration treatment step may be performed each time the cooking solvent is reused, or after multiple reuses, for example, after the second to fifth reuses, specifically after the third reuse. After the heat treatment, the solution is cooled to room temperature, and if necessary, the precipitate is removed by filtration or the like. Then, an alkali such as sodium hydroxide or potassium hydroxide is added to the heat-treated accumulated solution to neutralize the accumulated solution.

[0033] After step (e), (f) the neutralized solution is heated to concentrate it to a water content of 10% or less, preferably 5% or less, and more preferably less than 5%, thereby recovering the glycol-based solvent. In the concentration step, the internal temperature of the concentrator is set to, for example, 120 to 150°C, and heating is performed. The concentration is terminated when the liquid reaches the predetermined temperature. Water typically evaporates at 100°C, and once most of the water has evaporated, the internal temperature rises to 100°C or higher. When the recovered chemical solution is reused in the kneading step (a), if the chemical solution contains more than 10% water, the temperature rise time may increase. The heating time, such as temperature rise time, is thought to have a significant impact on the quality of the glycol lignin produced, and efficient water removal from the recovered chemical solution is an important factor in ensuring product quality.

[0034] In conventional production methods, a large amount of water is required to purify glycol lignin, resulting in a large amount of water in the resulting neutralized solution, and a large amount of energy is required to heat the neutralized solution and evaporate the water. In the production method of this embodiment, as described above, the amount of water used to purify glycol lignin can be significantly reduced, thereby significantly reducing the amount of energy required to recover the glycol-based solvent, contributing to lower costs and energy consumption in the production method.

[0035] When the concentration of the glycol-based solvent increases due to evaporation of water during concentration of the solution, a large amount of alkali metal salts produced by neutralization precipitates, causing a problem of clogging the piping at the bottom of the concentrator. Therefore, during concentration, it is preferable to provide a line for circulating the concentrated solution from the piping at the bottom of the concentrator to the top of the concentrator, and to perform concentration under pump circulation. After concentration, the solution can be sent from the concentrator to a solvent tank.

[0036] Any type of concentrator can be used, but it is preferable to use a wall-wetter type concentrator because it can efficiently remove water.

[0037] After step (f), (g) the alkali metal salt crystals produced by concentration are separated. The separation method is not particularly limited, but since the alkali metal salts in the recovered chemical solution are very prone to settling, 90% of them can be removed as precipitates by decantation. Furthermore, by installing a pre-filter such as a strainer in the liquid transfer line and then installing a finer mesh cartridge filter or the like in the subsequent stage, the alkali metal salts can be efficiently removed. For efficiency reasons, it is preferable to separate the alkali metal salt crystals in the liquid transfer line.

[0038] In this embodiment, the glycol-based solvent recovered in step (f) can be reused as the glycol-based solvent in step (a). When the recovered glycol-based solvent is reused as the glycol-based solvent in step (a), the amount of acid catalyst added in step (a) is appropriately adjusted because it is believed that some alkali metal salt remains in the recovered glycol-based solvent. [Example]

[0039] The present invention will be described in more detail below by showing examples, but the present invention is not limited to these examples.

[0040] Example 1: Production of glycol lignin 1 The glycol solvent used was polyethylene glycol with an average molecular weight of 400 (PEG-400). 7.5 g of sulfuric acid catalyst was added to 750 g of PEG-400 and stirred, after which approximately 810 g of cedar wood flour (750 g bone dry weight) was added. The mixture was placed in a planetary mixer (Inoue Seisakusho: PLM-15), stirring was initiated, and the internal temperature was raised to 135-140°C. After the temperature was raised, the mixture was maintained for the specified reaction time (60-200 minutes). The stirring speed of the planetary mixer was approximately 38 rpm. Shear stress acted between the planetary mixer blades and between the blades and the inner surface of the tank, kneading the materials. As the reaction progressed, the wood flour transformed into a clayey substance. After confirming the transformation, stirring was stopped, and the solid mixture was allowed to cool naturally.

[0041] After cooling, 50 g of sodium hydroxide solution (0.1 N) was added to 10 g of the kneaded product and stirred for 60 minutes using a magnetic stirrer. The mixture was filtered to separate the solution fraction containing glycol lignin from the solid residue (pulp). The solution fraction remaining in the pulp was washed with water and recovered. The pulp residue ratio was 47.7%.

[0042] The solution containing glycol lignin separated by filtration was transferred to a beaker, and sulfuric acid was added while stirring to adjust the pH. The adjusted solution was heated while stirring until the liquid temperature reached 50-60°C, yielding a glycol lignin suspension. Next, the solid matter containing glycol lignin was filtered, and the filtered product was again transferred to the beaker and washed with water. The yield of glycol lignin recovered was 33.8% based on the weight of the wood flour.

[0043] Example 2: Production of glycol lignin 2 Glycol lignin was produced and recovered in the same manner as in Example 1, except that the glycol solvent used in Example 1 was changed to a mixture of 675 g of polyethylene glycol (PEG-400) having an average molecular weight of 400 and 75 g of glycerin. The yield of recovered glycol lignin was 34.1% based on the weight of wood flour. The pulp residue rate was 45.6%.

[0044] Example 3: Production of glycol lignin 3 Glycol lignin was produced and recovered in the same manner as in Example 1, except that the glycol solvent used in Example 1 was changed to a mixture of 637.5 g of polyethylene glycol (PEG-400) having an average molecular weight of 400 and 112.5 g of glycerin. The yield of recovered glycol lignin was 31.3% based on the weight of wood flour. The pulp residue rate was 40.8%.

[0045] Example 4: Production of glycol lignin 4 Glycol lignin was produced and recovered in the same manner as in Example 1, except that the glycol-based solvent used in Example 1 was changed to a mixture of 600 g of polyethylene glycol (PEG-400) having an average molecular weight of 400 and 150 g of glycerin. The yield of recovered glycol lignin was 32.7% based on the weight of wood flour. The pulp residue rate was 41.6%.

[0046] Example 5: Production of glycol lignin 5 Glycol lignin was produced and recovered in the same manner as in Example 1, except that the glycol solvent used in Example 1 was changed to a mixture of 525 g of polyethylene glycol (PEG-400) having an average molecular weight of 400 and 225 g of glycerin. The yield of recovered glycol lignin was 30.3% based on the weight of wood flour. The pulp residue rate was 39.9%.

[0047] Example 6: Production of glycol lignin 6 Glycol lignin was produced and recovered in the same manner as in Example 1, except that the glycol solvent used in Example 1 was changed to a mixture of 450 g of polyethylene glycol (PEG-400) with an average molecular weight of 400 and 300 g of glycerin. The yield of recovered glycol lignin was 30.1% based on the weight of wood flour. The pulp residue rate was 41.1%.

[0048] Example 7: Production of glycol lignin 7 Glycol lignin was produced and recovered in the same manner as in Example 1, except that the glycol solvent used in Example 1 was changed to a mixture of 375 g of polyethylene glycol (PEG-400) having an average molecular weight of 400 and 375 g of glycerin. The yield of recovered glycol lignin was 27.9% based on the weight of wood flour. The pulp residue rate was 36.9%.

[0049] Example 8: Production of glycol lignin 8 Glycol lignin was produced and recovered in the same manner as in Example 1, except that the glycol solvent used in Example 1 was changed to a mixture of 300 g of polyethylene glycol (PEG-400) having an average molecular weight of 400 and 450 g of glycerin. The yield of recovered glycol lignin was 27.5% based on the weight of wood flour. The pulp residue rate was 46.8%.

[0050] Example 9: Production of glycol lignin 9 Glycol lignin was produced and recovered in the same manner as in Example 1, except that the glycol solvent used in Example 1 was changed to a mixture of 225 g of polyethylene glycol (PEG-400) having an average molecular weight of 400 and 525 g of glycerin. The yield of recovered glycol lignin was 27.7% based on the weight of wood flour. The pulp residue rate was 43.6%. [Industrial Applicability]

[0051] The method for producing glycol lignin of the present invention is extremely useful because it enables glycol lignin, which can be used as a raw material for high-value-added materials, to be produced safely and with stable quality on a plant scale at lower cost and with less energy than conventional production methods.

Claims

1. (a) in a mixing device having at least two stirring blades and a container, kneading lignocellulose with at least one glycol-based solvent selected from the group consisting of polyethylene glycol, diethylene glycol, ethylene glycol, propylene glycol, polypropylene glycol, glycerin, and polyglycerin in the presence of an acid catalyst under normal pressure while applying shear stress generated by the rotation of the at least two stirring blades, The amount of the glycol-based solvent is less than 2 parts by weight per 1 part by weight of the lignocellulose. Method for producing glycol lignin.

2. 2. The method for producing glycol lignin according to claim 1, wherein the mixing device is a planetary mixer, a kneader, a pug mill type mixer, a Loedige mixer, or an Apex mixer.

3. The method for producing glycol lignin according to claim 1 or 2, wherein the kneaded product obtained in the kneading step is in a solid state as a whole.

4. (b) mixing the kneaded product obtained in the kneading step with an alkaline aqueous solution and separating a solution fraction containing glycol lignin and a solid fraction from the resulting mixture; (c) acidifying the solution fraction with an acid to obtain glycol lignin as a precipitate; (d) separating a glycol lignin precipitate from the acidified solution fraction; (e) collecting the separated solution after separating the glycol lignin precipitate, and neutralizing the collected solution by adding an alkali to the collected solution; (f) heating the neutralized solution to concentrate it to a water content of 10% or less to recover the glycol-based solvent; (g) separating the alkali metal salt crystals produced by the concentration; The method for producing glycol lignin according to any one of claims 1 to 3, further comprising:

5. The glycol-based solvent recovered in the step (f) is reused as the glycol-based solvent in the step (a). The method for producing glycol lignin according to claim 4.