Modified lignin and method for producing the same

Abstract

This invention provides modified lignin, which can be effectively utilized as a plant-derived biomass, and which can be dispersed or dissolved in resin in a good state. [Solution] The modified lignin is an alkyl etherified lignin in which at least a portion of the aromatic hydroxyl groups of lignin are etherified with at least one alkyl group selected from the group consisting of linear alkyl groups having 4 to 22 carbon atoms, branched alkyl groups having 4 to 22 carbon atoms, cycloalkyl groups having 4 to 22 carbon atoms, and arylalkyl groups having 7 to 22 carbon atoms, and has a sulfur atom content of less than 0.2% by mass, a lignin-derived portion content of 50 to 90% by mass, and a number-average molecular weight of 800 to 10,000.

Description

Technical Field

[0001] The present invention relates to modified lignin and a method for producing the same.

Background Art

[0002] In recent years, from the perspectives of carbon dioxide reduction and circular economy, development of technologies utilizing biomass materials, particularly research and development of technologies utilizing wood which is a plant-derived material, has been actively carried out. Examples of biomass materials include cellulose, lignocellulose, and lignin. Among them, lignin is known as one of the most abundant substances on Earth, with an annual production volume reaching as high as 80 million tons. However, from the perspectives of coloring, poor solubility, and handleability, the only industrial applications are sulfonation for use as dispersants for cement and the like, while most of the lignin is incinerated and used as fuel energy.

[0003] In recent years, effective utilization of lignin for industrial and commercial applications has been investigated. Specifically, modification of lignin for application to thermoplastic resins and thermosetting resins has been studied. For example, phenol-modified lignin obtained by using lignin as a raw material for phenol resins has been proposed (Patent Documents 1 and 2). Also, polyalkylene glycol-modified lignin obtained by reacting lignin with polyethylene glycol has been proposed (Patent Documents 3 and 4). Furthermore, vinyl polymer-modified lignin obtained by imparting a radically polymerizable polymerization initiating group to lignin, then graft-polymerizing a vinyl monomer from the polymerization initiating group via living radical polymerization has been proposed (Non-Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

[0005] [Non-Patent Document 1] International Journal of Biological Macromolecules Volume207,15 May 2022,Pages522-530 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, phenol-modified lignin has limited applications due to its thermosetting properties. Furthermore, polyalkylene glycol-modified lignin is soft, and the heat resistance of the introduced polyalkylene glycol chains is low, making it difficult to produce articles with sufficiently satisfactory physical properties.

[0007] Furthermore, polyvinyl polymer-modified lignin is expected to improve the heat resistance and solvent solubility of the polyvinyl polymer to which it is applied. However, because vinyl monomers are grafted by living radical polymerization, the resulting modified lignin tends to retain polymerization catalysts and other substances, and the polymerization rate is often insufficient, resulting in residual monomers. For this reason, purification is necessary, and the formulation and polymerization conditions must be considered depending on the monomer being polymerized, which has resulted in a lack of versatility in the manufacturing process.

[0008] This invention has been made in view of the problems of the prior art, and its objective is to provide a resin composition with excellent manufacturability and processability, in which lignin, a plant-derived biomass, is effectively utilized and modified lignin, a modified form of lignin, is dispersed or dissolved in the resin in a good state. Another objective of this invention is to provide a simple method for manufacturing this resin composition. [Means for solving the problem]

[0009] In other words, the present invention provides the modified lignin shown below. [1] Alkyl etherified lignin in which at least a portion of the aromatic hydroxyl groups of lignin are etherified with at least one alkyl group selected from the group consisting of linear alkyl groups having 4 to 22 carbon atoms, branched alkyl groups having 4 to 22 carbon atoms, cycloalkyl groups having 4 to 22 carbon atoms, and arylalkyl groups having 7 to 22 carbon atoms, wherein the sulfur atom content is less than 0.2% by mass, the content of the portion derived from the lignin is 50 to 90% by mass, and the number average molecular weight is 800 to 10,000. [2] The modified lignin according to [1], wherein the alkyl group is a linear alkyl group having 8 to 22 carbon atoms or a branched alkyl group having 8 to 22 carbon atoms. [3] The resin composition according to [2], wherein the alkyl group is an octadecyl group.

[0010] Furthermore, the present invention provides a method for producing modified lignin as shown below. [4] A method for producing modified lignin according to any one of [1] to [3] above, comprising the step of reacting an alkali metal salt with the aromatic hydroxyl group of lignin having a sulfur atom content of less than 0.5% by mass to alkoxideize it, and then reacting it with an alkyl halide to obtain modified lignin which is alkyl etherified lignin, wherein the alkyl halide is at least one selected from the group consisting of linear alkyl halides having 4 to 22 carbon atoms, branched alkyl halides having 4 to 22 carbon atoms, cycloalkyl halides having 4 to 22 carbon atoms, and arylalkyl halides having 7 to 22 carbon atoms. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a resin composition with excellent manufacturability and processability, in which lignin, a modified form of lignin, is effectively utilized and modified lignin is dispersed or dissolved in the resin in a good state. Furthermore, according to the present invention, a simple method for producing this resin composition can be provided. [Brief explanation of the drawing]

[0012] [Figure 1] This is the NMR chart of denatured lignin HR-1 obtained in Synthesis Example 1. [Figure 2] This is the IR chart of denatured lignin HR-1 obtained in Synthesis Example 1. [Figure 3] This is a micrograph (50x magnification) showing the microstructure of a sheet prepared using resin composition J-1 manufactured in Example 1. [Figure 4] This is a micrograph (50x magnification) showing the microstructure of a sheet prepared using the resin composition HJ-1 manufactured in Comparative Example 1. [Figure 5] This is a micrograph (50x magnification) showing the microstructure of a sheet prepared using the resin composition HJ-2 manufactured in Comparative Example 2. [Modes for carrying out the invention]

[0013] <Resin composition> The embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments. One embodiment of the resin composition of the present invention is a composition containing modified lignin and a resin. Modified lignin is alkyl etherified lignin in which at least a portion of the aromatic hydroxyl groups of lignin are etherified with at least one alkyl group selected from the group consisting of linear alkyl groups having 4 to 22 carbon atoms, branched alkyl groups having 4 to 22 carbon atoms, cycloalkyl groups having 4 to 22 carbon atoms, and arylalkyl groups having 7 to 22 carbon atoms. The sulfur atom content of the modified lignin is less than 0.2% by mass, and the content of the portion derived from lignin constituting the modified lignin is 50 to 90% by mass. The number average molecular weight of the modified lignin is 800 to 10,000.

[0014] The resin composition of the present embodiment is a composition in which modified lignin, which is obtained by improving the resin physical properties derived from the polyaromatic nature of lignin that is plant-derived biomass, is well dispersed or dissolved. Lignin itself is a natural product that is poorly soluble and poorly dispersible, and is difficult to compound into thermoplastic resins and the like. When attempting to disperse or dissolve lignin in a thermoplastic resin, lignin aggregates will form. In contrast, the specific modified lignin can be favorably dispersed and dissolved in resins such as thermoplastic resins. Therefore, by using the specific modified lignin, a large amount of lignin can be compounded in the resin, and improvement in the transparency of the material is also expected.

[0015] Since the resin composition of the present embodiment makes effective use of lignin, which is an unused natural material, it contributes to environmental friendliness, carbon neutrality, global warming prevention, and waste reduction. In addition, by compounding lignin having many aromatic rings into a resin, the physical properties of the resin can be improved, and it is expected to provide an article imparted with effects such as ultraviolet absorbability, antibacterial properties, antioxidant properties, and heat resistance. Furthermore, since modified lignin can also function as a brown colorant derived from lignin, weight reduction can be achieved as compared with the case of using a brown inorganic pigment. Since lignin has biodegradability, the use of the resin composition of the present embodiment is also expected to solve the waste plastic problem.

[0016] When kraft lignin, organosolv lignin, sulfonated lignin and the like containing a large amount of sulfur (S) are thermally processed, a large amount of offensive sulfur odor tends to be generated. For this reason, thermal processing of lignin containing a large amount of sulfur is difficult, and odor tends to remain in the resulting article. In contrast, since the modified lignin used in the resin composition of the present embodiment has a low sulfur atom content, almost no odor is generated during thermal processing, and the produced article has almost no odor.

[0017] (Lignin) The modified lignin used in the resin composition of this embodiment is produced by modifying lignin obtained from plants or wood through decomposition or other means. Examples of raw materials for lignin include coniferous trees such as cedar, pine, and cypress; broad-leaved trees such as beech, birch, oak, and zelkova; and grasses such as rice, wheat, corn, and sugarcane; and other woods and plants.

[0018] The method for producing lignin is not particularly limited, and lignin produced in paper manufacturing, pulp manufacturing processes, bioethanol manufacturing processes, and cellulose-degrading enzyme processes can be used. The lignin obtained in the above processes may be pure lignin, which is extracted as the target product, or a by-product of the above processes. Examples of lignin obtained as a by-product include kraft lignin, lignin sulfonic acid, soda lignin, organosorb lignin, explosion lignin, and lignophenol. The modified lignin contained in the resin composition of this embodiment is lignin modified to have a sulfur atom content of less than 0.5% by mass, preferably less than 0.2% by mass. It is preferable to use lignin obtained in manufacturing processes such as bioethanol manufacturing processes or cellulose-degrading enzyme methods. The lignin may contain impurities such as polysaccharides and inorganic substances.

[0019] Lignin is a naturally occurring material with a complex chemical structure. It contains a complex array of groups and bonds, including aromatic rings, phenolic hydroxyl groups, aliphatic hydroxyl groups, aldehydes, ether groups, ketone groups, and unsaturated bonds, making it impossible to determine its chemical structure definitively. A typical example of a lignin structure is shown below.

[0020] TIFF2026167399000001.tif155170

[0021] Lignin typically contains aromatic hydroxyl groups (phenolic hydroxyl groups) in its molecular structure. The presence or absence of phenolic hydroxyl groups can be confirmed by infrared spectroscopy, nuclear magnetic resonance spectroscopy, and colorimetric reactions. The amount of phenolic hydroxyl groups can also be quantified by titration. Titration methods include the anhydride acetate-pyridine titration method, titration using the forin-siocart reagent, and methods for calculation from IR and NMR peaks. However, because lignin is highly colored, has a complex structure, and its exact structure has not been definitively determined, it is difficult to accurately measure the amount of phenolic hydroxyl groups. In this invention, the presence of sufficient phenolic hydroxyl groups in the lignin is confirmed by analysis using IR and NMR. That is, the amount of phenolic hydroxyl groups in the lignin used is not particularly limited; any lignin having one or more phenolic hydroxyl groups in its molecule can be used.

[0022] Lignin has a complex structure, and even when dissolved in solution, it does not form random coils like linear polymers, but rather a complex three-dimensional structure, making it difficult to accurately measure its molecular weight. In this invention, a solution prepared by dissolving lignin and modified lignin in a solvent such as tetrahydrofuran (THF) or dimethylformamide (DMF) is used, and the number-average molecular weight (Mn) in polystyrene equivalent, measured by gel permeation chromatography (GPC), is used as the molecular weight of lignin and modified lignin. The number-average molecular weight (Mn) of lignin is preferably 500 to 9,000, and more preferably 800 to 8,000. If the Mn of lignin is less than 500, the molecular weight is too small, and the effects of using lignin may not be fully realized. On the other hand, if the Mn of lignin exceeds 9,000, the Mn of modified lignin also increases, which can lead to increased viscosity, decreased compatibility with the resin used as the dispersion medium, or increased gelation during mixing. The molecular weight distribution of lignin (PDI = weight-average molecular weight (Mw) / number-average molecular weight (Mn)) is not particularly limited and may be, for example, between 1.5 and 100. In this specification, "number-average molecular weight (Mn)" is a polystyrene-convertible value measured by GPC using THF as the developing solvent. Examples of detectors used for GPC measurement include radioisotope refractometers (RI detectors) and ultraviolet detectors (UV detectors, measurement wavelength 254 nm). In the examples described later, a UV detector was used.

[0023] (Modified lignin) Modified lignin is alkyl etherified lignin in which at least some of the aromatic hydroxyl groups of the lignin described above are etherified (alkyl etherified) with a specific alkyl group. By attaching many alkyl groups to the molecular skeleton of lignin, properties such as thermoplasticity and solvent solubility can be imparted to the lignin, and its compatibility with resins can be improved.

[0024] The alkyl group is at least one selected from the group consisting of linear alkyl groups having 4 to 22 carbon atoms, branched alkyl groups having 4 to 22 carbon atoms, cycloalkyl groups having 4 to 22 carbon atoms, and arylalkyl groups having 7 to 22 carbon atoms. Examples of linear alkyl groups having 4 to 22 carbon atoms include butyl group, pentyl group, hexyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group, henicosyl group, and docosyl group.

[0025] Examples of branched alkyl groups having 4 to 22 carbon atoms include isobutyl group, t-butyl group, 2-ethylhexyl group, 3,7-dimethyloctyl group, 2-hexyloctyl group, 2-hexyldecyl group, 2-octyldodecyl group, and 3,7,11-trimethyldodecyl group. Note that branched alkyl groups having 4 to 22 carbon atoms also include primary alkyl groups having cyclic cycloalkyl groups such as cyclohexylmethyl group. Examples of cycloalkyl groups having 4 to 22 carbon atoms include cyclohexyl group, t-butylcyclohexyl group, trimethylcyclohexyl group, tricyclodecyl group, and isobornyl group. Furthermore, examples of arylalkyl groups having 7 to 22 carbon atoms include benzyl group and phenylethyl group.

[0026] When using an olefin-based polymer, which is a thermoplastic resin, as the resin, the alkyl group is preferably a linear alkyl group having 8 to 22 carbon atoms or a branched alkyl group having 8 to 22 carbon atoms, and more preferably a linear alkyl group having 8 to 22 carbon atoms. Modified lignin etherified with these alkyl groups has particularly excellent compatibility with olefin-based polymers. Furthermore, the crystallinity of the long-chain alkyl group improves handling, and is also preferable from the viewpoint of thermoplasticity and low melting point of the modified lignin. Examples of linear alkyl groups having 8 to 22 carbon atoms include octyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group, and docosyl group. These alkyl groups are aliphatic groups derived from natural materials such as coconut oil. Therefore, by modifying lignin, which is a natural material, with these alkyl groups, all of the modified lignin can be made from natural materials, which is environmentally friendly. Among these, the alkyl group is preferably an octadecyl group from the viewpoint of cost, crystallinity, and melting point.

[0027] Modified lignin is obtained by etherifying at least a portion of the aromatic hydroxyl groups of lignin with alkyl groups, and consists of a lignin-derived portion and the introduced alkyl group. The content of the lignin-derived portion constituting the modified lignin is preferably 50 to 90% by mass, and more preferably 60 to 80% by mass, based on the total of the lignin-derived portion and the alkyl group. If the content of the lignin-derived portion exceeds 90% by mass, the amount of alkyl group is small, resulting in insufficient compatibility with the resin and making it prone to granulation. On the other hand, if the content of the lignin-derived portion is less than 50% by mass, the amount of alkyl group is large, which reduces the mechanical properties of the resin, causing it to soften, or significantly lowers the melting temperature of the resin composition.

[0028] If the modified lignin is one in which some of the aromatic hydroxyl groups of lignin have been etherified with a specific alkyl group, the remaining aromatic hydroxyl groups may remain as they are, or they may be etherified with an alkyl group other than the specific alkyl group. Furthermore, the remaining aromatic hydroxyl groups may be reacted with compounds having epoxy groups or compounds having carboxyl groups. In addition, the aliphatic hydroxyl groups in the structure of lignin may be reacted with compounds that can react with such hydroxyl groups, such as compounds having carboxyl groups, amino groups, and isocyanate groups, or compounds that can react with aliphatic hydroxyl groups, such as acid halides.

[0029] The sulfur atom content of the modified lignin is less than 0.2% by mass, preferably less than 0.1% by mass. By using modified lignin with a sulfur atom content of less than 0.2% by mass, the generation of unpleasant odors (sulfurous odor) during processing can be suppressed, and the sulfurous odor remaining in the molded product can be reduced. As will be described later, modified lignin with a sulfur atom content of less than 0.2% by mass can be obtained by modifying lignin with a sulfur atom content of less than 0.5% by mass.

[0030] The number-average molecular weight (Mn) of modified lignin is 800 to 10,000, preferably 1,000 to 8,000. If the Mn of modified lignin is less than 800, the molecular weight is too small, which may make it difficult to achieve the desired effect of using modified lignin. On the other hand, if the Mn of modified lignin is greater than 10,000, the compatibility with resins tends to decrease, or the viscosity may increase during mixing with resins. The molecular weight distribution (PDI) of modified lignin is not particularly limited and can be, for example, 1.5 to 100.

[0031] (resin) Conventional thermoplastic resins and thermosetting resins can be used as resins. Examples of thermoplastic resins include olefin polymers such as polyethylene, polypropylene, polyethylene vinyl acetate, polyethylene vinyl alcohol, polyethylene ethyl acrylate, polymethylpentene, and polycyclopentadiene; styrene polymers such as polystyrene, polystyrene butadiene polymer, and polyacrylonitrile butadiene styrene; halogenated vinyl polymers such as polyvinyl chloride, polyvinylidene chloride, and polytetrafluoroethylene; acrylic polymers such as polymethyl methacrylate and polyacrylonitrile; vinyl acetate polymers such as polyvinyl acetate and polyvinyl alcohol; ester polymers such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactic acid, and polyhydroxyalkanoic acid; amide polymers such as nylon 6, nylon 66, and polyamide 11; carbonate polymers such as polybisphenol A carbonate; acetal polymers such as polyoxymethylene; urethane polymers; silicone polymers; and engineering plastics such as polyphenylene ether, polyphenylene sulfide, and polyether ether ketone. Examples of thermosetting resins include phenolic resins, urea resins, alkyd resins, unsaturated polyester resins, and epoxy resins.

[0032] As the resin, it is preferable to use a thermoplastic resin that can be processed into films, molded products, containers, and fibers. In particular, since modified lignin having long-chain alkyl ether groups is used, it is preferable to use an olefin polymer that has good compatibility with such modified lignin, and it is even more preferable to use a highly versatile olefin polymer such as polyethylene or polypropylene.

[0033] In the resin composition, the content of modified lignin is preferably 1 to 33.4% by mass, and more preferably 5 to 25% by mass, based on the total amount of modified lignin and resin. If the content of modified lignin is less than 1% by mass, the effects of using modified lignin may not be fully realized. On the other hand, if the content of modified lignin exceeds 33.4% by mass, the amount of alkyl ether groups in the structure of the modified lignin becomes too large, which may significantly degrade the physical properties of the resin composition itself. When the content of modified lignin in the resin composition is 1 to 33.4% by mass, the content of the lignin-derived portion in the resin composition is, for example, 0.5 to 30% by mass, based on the total amount of modified lignin and resin.

[0034] (Additives) The resin composition may further contain various additives as components other than modified lignin and resin. Examples of additives include antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, antifogging agents, lubricants, compatibilizers, conductive materials, magnetic materials, foaming agents, fragrances, odor reducers, and flame retardants. Lignin may decompose upon heating, generating vanillin and other substances. Therefore, amines or hydrazine compounds can be added to the resin composition to trap vanillin. Colorants such as dyes and pigments may also be further included. Furthermore, various fillers such as silica, glass fibers, carbon fibers, carbon nanotubes, cellulose fibers, cellulose nanofibers, lignocellulose, and unmodified lignin may also be further included.

[0035] When wood-derived materials such as cellulose fibers, lignocellulose, and unmodified lignin are used as fillers, modified lignin can adsorb to the surface of these fillers and act as a dispersant, allowing these fillers to be dispersed in the resin as fine particles. Furthermore, when fillers with a six-membered carbon skeleton, such as carbon fibers or carbon nanotubes, are used, the polyaromatic rings of modified lignin can adsorb to the fillers through ππ stacking, allowing the fillers to be well dispersed in the resin.

[0036] The resin composition of this embodiment is useful as a material for various molded products such as automobiles, home appliances, electronic components, display materials, building materials, food containers, cosmetic containers, agricultural films, and battery materials.

[0037] The resin composition may be molded as is to produce a molded article, or it may be made into a masterbatch containing a high concentration of modified lignin, then diluted with resin to a predetermined amount of modified lignin before molding to produce a molded article. The resin composition of this embodiment effectively utilizes the effects of lignin, improving the mechanical properties and light resistance of the resin used as the base. Furthermore, since it uses lignin, which is a biomass material, it is possible to manufacture environmentally friendly molded articles. Moreover, since it uses lignin derived from plants such as wood, it is possible to manufacture a resin composition that can produce molded articles with a wood-like texture. In addition, since the resin composition of this embodiment uses lignin, it is also expected to provide molded articles that are environmentally degradable, meaning that when left in the environment, their shape will collapse due to the action of white rot fungi that decompose lignin.

[0038] <Method for producing resin compositions> The aforementioned resin composition can be produced by the following method. That is, one embodiment of the method for producing the resin composition of the present invention is a method for producing the aforementioned resin composition, which includes a step (modification step) in which an alkali metal salt is reacted with the aromatic hydroxyl group of lignin having a sulfur atom content of less than 0.5% by mass to alkoxideize it, and then an alkyl halide is reacted to obtain modified lignin, which is alkyl etherified lignin. The alkyl halide is at least one selected from the group consisting of linear alkyl halides having 4 to 22 carbon atoms, branched alkyl halides having 4 to 22 carbon atoms, cycloalkyl halides having 4 to 22 carbon atoms, and arylalkyl halides having 7 to 22 carbon atoms.

[0039] When alkyl etherifying lignin, the reaction can be carried out with the lignin completely dissolved in a lignin-soluble organic solvent. Alternatively, aromatic hydroxyl groups on the surface or inside of particulate lignin dispersed in a lignin-insoluble or sparingly soluble solvent may be alkyl etherified. Examples of lignin-soluble organic solvents include amide solvents such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and 3-methoxy-N,N-dimethylpropionamide; sulfoxide solvents such as dimethyl sulfoxide and sulfolane; urea solvents such as tetramethylurea and dimethylimidazolidinone; and the like. Examples of lignin-insoluble or sparingly soluble solvents include water; hydrocarbon solvents such as toluene; alcohol solvents such as isopropyl alcohol; ketone solvents such as acetone and methyl ethyl ketone; ester solvents such as butyl acetate; ether solvents such as tetrahydrofuran; glycol solvents such as diethylene glycol dimethyl ether; and the like. It should be noted that a lignin-soluble organic solvent may be used in combination with a lignin-insoluble or sparingly soluble solvent.

[0040] As the lignin used, lignin with a sulfur atom content of less than 0.5% by mass, preferably 0.3% by mass or less, is used. By denaturing lignin with a sulfur atom content of less than 0.5% by mass, denatured lignin with a sulfur atom content of less than 0.2% by mass can be obtained.

[0041] Lignin can be dissolved or dispersed in a solvent, and then alkoxideized by reacting at least some of the aromatic hydroxyl groups of the lignin with an alkyl metal salt. The concentration of lignin in the lignin solution / dispersion obtained by dissolving or dispersing lignin in a solvent can be, for example, 10 to 40% by mass, or 20 to 33% by mass if productivity is considered. Examples of alkyl metal salts include carbonates such as sodium carbonate and potassium carbonate; alkali metal alkoxides such as sodium methoxide and potassium t-butoxide; sodium hydride; and the like.

[0042] Alkoxide-modified lignin, in which at least some of the aromatic hydroxyl groups have been alkoxide-modified, is reacted with an alkyl halide. This process eliminates the alkali metal halide, and at least some of the aromatic hydroxyl groups of the lignin are alkyl etherified, yielding modified lignin, which is alkyl ether-modified lignin.

[0043] The reaction between alkoxide-modified lignin and alkyl halides is a nucleophilic substitution reaction by the alkyl halide. At least one alkyl halide is selected from the group consisting of linear alkyl halides (4-22 carbon atoms), branched alkyl halides (4-22 carbon atoms), cycloalkyl halides (4-22 carbon atoms), and arylalkyl halides (7-22 carbon atoms). From the viewpoint of suppressing the side effect of alkyl halide elimination, it is preferable to use a primary alkyl halide. Furthermore, alkyl chlorides, alkyl bromides, and alkyl iodides can be used as alkyl halides. Among these, alkyl bromides are preferred from the viewpoint of elimination properties and stability. Specific examples of alkyl halides include octyl bromide, nonyl bromide, decyl bromide, dodecyl bromide, tridecyl bromide, tetradecyl bromide, hexadecyl bromide, heptadecyl bromide, octadecyl bromide, and docosyl bromide. Among these, octadecyl chloride, octadecyl bromide, and octadecyl iodide are preferred, with octadecyl bromide being particularly preferred.

[0044] The amount of alkyl halide reacted with alkoxide-modified lignin is not particularly limited. However, in order to suppress the residue of unreacted alkyl halides, it is preferable to react with a small amount of alkyl halide relative to the alkoxide-modified hydroxyl groups. Specifically, it is preferable to use 1.1 to 3 moles of alkoxide-modified lignin per mole of alkyl halide, and more preferably 1.3 to 2 moles.

[0045] The temperature at which the alkali metal salt reacts with the aromatic hydroxyl group of lignin can be, for example, 0 to 100°C, and preferably 30 to 50°C. The temperature at which the alkoxide-modified lignin reacts with the alkyl halide can be, for example, 50 to 150°C, and preferably 70 to 110°C.

[0046] Modified lignin can be precipitated by reacting alkoxide-modified lignin with an alkyl halide, and then adding the reaction solution to water or an aqueous liquid medium containing water. If an aqueous liquid medium containing an acidic substance such as hydrochloric acid or acetic acid is used, the remaining alkoxide that did not react with the alkyl halide can be converted into aromatic hydroxyl groups. The precipitated modified lignin can then be thoroughly washed with water or methanol to remove the resulting alkali metal halides. After washing, the modified lignin can be used as an aqueous paste, or after drying, as a powder or in the form of lumps. It can also be pulverized as needed.

[0047] The modified lignin, resin, and various additives used as needed can be mixed and kneaded using conventionally known methods to obtain the desired resin composition. If the resin is solid, it is preferable to heat-melt the resin and knead it. Mixing rolls, Banbury mixers, kneaders, kneader-ruders, single-screw extruders, and multi-screw extruders can be used for kneading. The temperature during kneading should be set considering the melting point and midpoint of the resin used. After kneading, the obtained resin composition may be cut into sheets or pelletized using a pelletizer. On the other hand, if the resin is liquid, a stirrer such as a disper can be used. [Examples]

[0048] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the examples and comparative examples, "parts" and "%" are based on mass unless otherwise specified.

[0049] <Synthesis of denatured lignin> (Synthesis Example 1) 525 parts of dimethylformamide (DMF) were added to a reaction vessel and stirred. 114.1 parts of lignin-1 (trade name "LIGNOVA PURE", manufactured by Fibenol, number average molecular weight (Mn) 610, molecular weight distribution (PDI) 20.3, peak-top molecular weight (PT) 1,200, lignin content 98.8%, sulfur atom content 0.2%) were added and dissolved in DMF. A dark brown solution was obtained, with almost no insoluble matter. Molecular weights and other values ​​are polystyrene equivalents measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as the developing solvent.

[0050] 45.6 parts of potassium carbonate were added and the mixture was reacted at 50°C for 2 hours. 100.2 parts of octadecyl bromide (SB) were added and the mixture was reacted at 90°C for 7 hours. Initially, there were no insoluble components, but after 2 hours, the mixture became opaque. It is thought that potassium bromide, a by-product, was formed during the reaction. After the reaction was complete, the reaction solution was analyzed by GPC, and no peak for SB, the starting material, was detected, suggesting that all of the SB reacted with lignin.

[0051] 5,000 mL of water was placed in a separate container, and 200 parts of hydrochloric acid diluted 10 times with water were added. When the reaction solution was added while stirring with a disperser, a brown powder precipitated. After stirring for 30 minutes, it was filtered. The filtrate was slightly brown and almost transparent. After washing thoroughly with water, it was removed and dried in a drying oven at 60°C. Using a moisture meter set to 120°C, it was further dried until the non-volatile content was 99% or more, yielding 189.1 parts of modified lignin HR-1, a brown powder with a non-volatile content of 99.5%.

[0052] Analysis of the obtained modified lignin HR-1 by GPC revealed a unimodal peak shape. Furthermore, the Mn content was 2,400, PDI was 10.5, and PT was 3,400, confirming an increase in molecular weight compared to the starting material, lignin-1. NMR and IR measurements were performed using a nuclear magnetic resonance spectrometer and an infrared spectrophotometer. The NMR chart of modified lignin HR-1 is shown in Figure 1. The IR chart of modified lignin HR-1 is shown in Figure 2. As shown in Figure 1, the aromatic ring peak of lignin is observed around 6.5-6.7 ppm, and the alkyl group peak of the octadecyl group can also be confirmed. Also, as shown in Figure 2, at 3,000 cm⁻¹... -1 Nearby alkyl groups, and 1,700 cm -1 A characteristic peak of lignin in the vicinity was identified. Based on this, it was confirmed that alkyl etherified lignin was formed. Furthermore, a portion of the material was burned, and the resulting gas was absorbed using an absorption solution. This solution was analyzed by ion chromatography. As a result, a peak of sulfur atoms was observed. The sulfur atom content was quantified to be 0.12%, indicating a very low sulfur atom content.

[0053] Since all of the SB used has reacted, the amount of alkyl group (octadecyl group) and lignin contained in the resulting modified lignin can be calculated according to the following calculation method.

[0054] A: Moles of SB = Moles of hydrogen released from lignin: 100.2 (parts by mass of SB) ÷ 333.4 (molecular weight of SB) = 0.3 B: Mass % of octadecyl groups in SB = 253.5 (molecular weight of octadecyl groups in SB) ÷ 333.4 (molecular weight of SB) × 100 = 76.0 C: Amount of lignin after reaction = 114.1 (mass part of lignin) - 0.3 (amount of hydrogen atoms eliminated in the reaction) = 113.8 D: Mass of the octadecyl group introduced into lignin = 100.2 (mass part of SB) × B / 100 = 76.1 Lignin content (mass %) in denatured lignin = C ÷ (C + D) × 100 = 113.8 / (113.8 + 76.1) × 100 = 60

[0055] From the above, it can be seen that modified lignin HR-1 contains lignin and alkyl groups in a ratio of lignin:alkyl group = 60:40, and that its lignin content is 60%.

[0056] (Synthesis examples 2-6, comparative synthesis examples 1-3) Modified lignins HR-2 to 6 and HHR-1 to 3 were obtained in the same manner as in Synthesis Example 1 described above, except that the types and quantities of various materials shown in Tables 1 and 2 were used. The various physical properties of the obtained modified lignins are shown in Tables 1 and 2. The amount of DMF was adjusted so that the other raw materials accounted for 33.1% by mass. The meaning of the abbreviations in Tables 1 and 2 is shown below. BB: Butyl bromide • DB: Dodecyl bromide TB: Tetradecyl bromide Lignin-2: Product name "IndulinAT", manufactured by INGEVITY, Mn800, PDI11.18, PT1,200, lignin content 97.5%, sulfur atom content 5%)

[0057] TIFF2026167399000002.tif111170

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[0059] The modified lignin HHR-1 obtained in Comparative Synthesis Example 1 has a high lignin content and a low alkyl group content, meaning it is a modified lignin with a low amount of alkyl groups compatible with resin. The modified lignin HHR-2 obtained in Comparative Synthesis Example 2 has a low lignin content and a high alkyl group content. This modified lignin HHR-2 dissolved at 60°C when dried, similar to Synthesis Example 1, and was found to be soft. In Comparative Synthesis Example 3, lignin with a high sulfur atom content was used. As a result, a strong sulfurous odor was detected during synthesis and drying after precipitation, raising concerns about processing and use in products.

[0060] <Manufacturing and evaluation of resin compositions (1)> (Example 1) 83.3 parts of polyethylene (PE-1) (product name "Novatec LF640MA", manufactured by Nippon Polyethylene Co., Ltd., MFR 5g / 10min, melting point 113℃, coarsely crushed), 16.7 parts of modified lignin HR-1, and 0.1 parts of antioxidant (product name "Irganox 10101", manufactured by BASF) were placed in a poly bag and shaken well to mix. Then, using a mixing mixer (model "IMC-A911", manufactured by Inoue Seisakusho Co., Ltd., mixing blade clearance 0.5mm), the mixture was kneaded at 180℃ to obtain resin composition J-1, a dark brown mixture. No unpleasant odors such as sulfurous odor were generated during kneading. The evaluation result for processability was "○". The evaluation criteria for processability are shown below. ○: No unpleasant odor was produced. ×: A strong, unpleasant odor was produced.

[0061] After grinding the resin composition J-1 obtained using a pulverizer, a sheet approximately 0.5 mm thick was prepared using a hot press. The prepared sheet was free of lumps and foreign matter, was a uniform brown sheet, and the compatibility evaluation result was "○". A micrograph (50x magnification) showing the microstructure of the prepared sheet is shown in Figure 3. Figure 3 shows that the modified lignin was dispersed in the resin in an extremely compatible state. The compatibility evaluation criteria are shown below. ○: No foreign matter or other contaminants were present, and the mixture was well compatible. △: Some foreign matter or particles were observed, but the amount was small. ×: While some parts were found to be compatible, there were many lumps and foreign objects. ××: They were almost completely incompatible and consisted of lumps and foreign matter.

[0062] (Examples 2-20, Comparative Examples 1-5) Resin compositions J-2 to 20 and HJ-1 to 5 were obtained in the same manner as in Example 1 described above, except that the formulations and conditions were as shown in Tables 3 to 7. The physical properties and evaluation results of the obtained resin compositions are shown in Tables 3 to 7. The meaning of the abbreviations in the tables is shown below. Furthermore, Figure 4 shows a micrograph (50x magnification) of the microstructure of the sheet made using resin composition HJ-1 produced in Comparative Example 1. In addition, Figure 5 shows a micrograph (50x magnification) of the microstructure of the sheet made using resin composition HJ-2 produced in Comparative Example 2. PE-2: Polyethylene, product name "Suntech-LD-M6545", manufactured by Asahi Kasei Corporation, MFR 45g / 10min, bit cut softening point temperature 79℃, coarsely crushed product • PP: Polypropylene, product name "Prime PolyPro J707EG", manufactured by Prime Polymer, MFR 30g / min PA: Polyamide 11, trade name "Rilsan BMNO", manufactured by Arkema, melting point 189°C • PES: Polylactic acid, product name "Luminy LX175", manufactured by Total Corbion PLA, MFR 8g / 10min, melting point 150~160℃

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[0068] <Manufacturing and evaluation of resin compositions (2)> (Examples 21 and 22) The resin composition J-3 obtained in Example 3 was pulverized using a pulverizer. 75 parts of PE-1 and 25 parts of the pulverized resin composition J-3 were mixed and then kneaded at 180°C using a twin-screw extruder. Next, the mixture was extruded in strand form, cooled, and then cut with a pelletizer to obtain the pelletized resin composition J-21.

[0069] Similarly, a pelletized resin composition J-22 was obtained using 90 parts of PE-1 and 10 parts of pulverized resin composition J-3. Resin composition J-21 had a modified lignin content of 8.3% and a lignin content of 5%. Resin composition J-22 had a modified lignin content of 3.3% and a lignin content of 2%. Sheets were prepared using each of the obtained resin compositions in the same manner as in Example 1. Upon observation of the prepared sheets, it was found that there were no blemishes or foreign matter, indicating good compatibility. From these results, it was found that by diluting a resin composition containing a high concentration of modified lignin, it is possible to produce resin compositions and molded products with modified lignin at any desired concentration. In other words, it was found that the resin compositions of this embodiment can be used as masterbatches.

[0070] (Example 23) 77.5 parts of cresol novolac epoxy resin (product name "Epiclon N-660", manufactured by DIC Corporation), 20 parts of modified lignin HR-5, 0.5 parts of 2-methylimidazole, and 2 parts of carnauba wax were mixed and kneaded for 5 minutes using a heated roll at a temperature of 100°C to obtain a sheet-like molded product. After cooling, the obtained sheet-like molded product was pulverized to obtain resin composition J-23. The obtained resin composition J-23 has a modified lignin content of 20% by mass and a lignin content of 4.6%. Using the obtained resin composition J-23, a sheet was prepared in the same manner as in Example 1. When the prepared sheet was observed, it was found to have no blemishes or foreign matter and showed good compatibility.

[0071] <Example of evaluation> Dumbbell pieces (dumbbell thickness: 2 mm) were manufactured by injection molding PP and resin composition J-14 at 200°C. Tensile tests were then conducted using a tensile testing machine (universal testing machine, manufactured by Shimadzu Corporation) in accordance with JIS K7161, and the tensile strength, tensile elongation, and tensile modulus were measured and calculated. As a result, the tensile strength of the dumbbell piece manufactured using PP was 27.6 MPa, the tensile elongation was 40%, and the tensile modulus was 1,450 MPa. In contrast, the tensile strength of the dumbbell piece manufactured using resin composition J-14 was 24.3 MPa, the tensile elongation was 53%, and the tensile modulus was 1,560 MPa. From these results, it can be seen that the physical properties of the resin (PP) were improved by using modified lignin. Similar tests were also conducted on resin compositions manufactured in other examples, and it was confirmed that the physical properties of the resin were improved. [Industrial applicability]

[0072] The resin composition of the present invention is useful as a constituent material for automobiles, home appliances, electronic components, display materials, buildings, containers, films, batteries, and semiconductor encapsulants.

Claims

1. Alkyl etherified lignin is characterized in that at least a portion of the aromatic hydroxyl groups of lignin are etherified with at least one alkyl group selected from the group consisting of linear alkyl groups having 4 to 22 carbon atoms, branched alkyl groups having 4 to 22 carbon atoms, cycloalkyl groups having 4 to 22 carbon atoms, and arylalkyl groups having 7 to 22 carbon atoms. The sulfur atom content is less than 0.2% by mass. The content of the lignin-derived portion is 50 to 90% by mass. Modified lignin with a number-average molecular weight of 800 to 10,000.

2. The modified lignin according to claim 1, wherein the alkyl group is a linear alkyl group having 8 to 22 carbon atoms or a branched alkyl group having 8 to 22 carbon atoms.

3. The resin composition according to claim 2, wherein the alkyl group is an octadecyl group.

4. A method for producing modified lignin according to any one of claims 1 to 3, The process involves reacting the aromatic hydroxyl groups of lignin with an alkali metal salt to alkoxideize them, and then reacting them with an alkyl halide to obtain modified lignin, which is alkyl etherified lignin. A method for producing modified lignin, wherein the alkyl halide is at least one selected from the group consisting of linear alkyl halides having 4 to 22 carbon atoms, branched alkyl halides having 4 to 22 carbon atoms, cycloalkyl halides having 4 to 22 carbon atoms, and arylalkyl halides having 7 to 22 carbon atoms.

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