COMPOSITE MATERIAL DERIVED FROM LIGNOCELLULOSIC BIOMASS, MULTI-COMPOSITE COMPOSITE MATERIAL AND A METHOD FOR PRODUCING THE SAME

Abstract

Composite material in which some hydroxy groups of a lignocellulosic biomass are esterified, wherein the esterified section has short-chain acyl groups with 2 to 4 carbon atoms and long-chain acyl groups with 8 to 18 carbon atoms.

Description

Technical field

[0001] The present invention relates to a composite material derived from a lignocellulosic biomass, a multi-component composite material, and a method for producing the same. General state of the art

[0002] To achieve a low-carbon society, the use of carbon-neutral resources is expressly desired. In particular, lignocellulosic biomass has attracted attention, as it does not compete with food production and is abundant in nature. Lignocellulosic biomass, such as wood, is a polymeric composite material composed of cellulose, hemicellulose, and lignin, which is a polycyclic aromatic polymer. These three components are bound together via strong hydrogen bonds or similar mechanisms, resulting in a beautiful, fine, and strong structure. The development of a technology to obtain a more useful material using this lignocellulosic biomass as a raw material is desirable.

[0003] To develop a technique for converting lignocellulosic biomass into a useful material, the use of an ionic liquid, which is an organic salt in the liquid state at room temperature, has been proposed. For example, patent literature 1 (WO2016 / 068053 A1) discloses a process for producing a polysaccharide derivative, which includes carrying out a reaction in a mixture comprising a polysaccharide-containing feedstock, an ionic liquid for which the pKa of an acid conjugate of an anion in DMSO is 12 to 19 and which is capable of producing a carbene, and a chain or cyclic ester compound or an epoxide compound.

[0004] EP 1 827 645 B1 discloses a composite material with a short-chain acyl group having 4 carbon atoms. The document discloses a process involving a first esterification with an aliphatic monocarboxylic acid and a second esterification with a dicarboxylic acid, which introduces an ionic residue into the fiber. CN 102311550 A discloses a modification of lignocellulose with acyl groups, wherein the acyl groups have 2 to 12 carbon atoms. JP2012167192 discloses a process for improving the thermoplastic properties (plasticity) of cellulose-based composite materials, in which acylating agents with short-chain alkyl groups having 1 to 4 carbon atoms are used. WO2017 / 217503 A1 discloses modifying cellulose by esterification, whereby both short-chain acyl groups with 2 to 4 carbon atoms and long-chain acyl groups with 7 or more carbon atoms can be present in the final product.The presence of short- and long-chain groups improves the mechanical properties and the thermoplastic properties (plasticity). Summary of the invention: Technical problem

[0005] According to the patent literature described above 1, an ionic liquid, such as 1-ethyl-3-methylimidazolium acetate, which dissolves a lignocellulosic biomass and also acts as a catalyst in a transesterification reaction, is used, and a polysaccharide derivative can be obtained directly from a lignocellulosic biomass used as a raw material while maintaining a high degree of polymerization.

[0006] Although the material for the polysaccharide derivative obtained from the patent literature described above was excellent with respect to mechanical strength, there was still room for improvement regarding flexibility and thermoformability. Therefore, an objective of the present invention is to obtain a novel composite material that is excellent in terms of flexibility and thermoformability, using a lignocellulosic biomass as a raw material. Solution to the problem

[0007] To achieve the aforementioned goal, the inventors of the present application conducted intensive studies. As a result, the inventors discovered that a composite material with excellent flexibility and thermoformability can be obtained by esterifying certain hydroxyl groups of a lignocellulosic biomass with short- and long-chain acyl groups, thereby completing the present invention. More precisely, the essential features of the present invention are as follows. (1) A composite material in which some hydroxy groups of a lignocellulosic biomass are esterified, wherein the esterified section has short-chain acyl groups with 2 to 4 carbon atoms and long-chain acyl groups with 8 to 18 carbon atoms. (2) The composite material according to (1) above, wherein both the short-chain acyl groups and the long-chain acyl groups are alkanoyl groups. (3) The composite material according to (1) or (2) above, wherein the molar ratio between the short-chain acyl groups and the long-chain acyl groups is as follows: the short-chain acyl groups : the long-chain acyl groups = 7 : 1 to 1 : 3. (4) The composite material according to at least one of (1) to (3) above, wherein the substitution percentage with respect to the short-chain acyl groups and the long-chain acyl groups is 75 mol% or more. (5) A multi-component composite material formed by mixing the composite material according to any one of (1) to (4) above with another organic or inorganic material. (6) A method for producing the composite material according to any one of (1) to (4) above, comprising: a step in carrying out a reaction in a mixture comprising a biomass containing lignocellulose, an ionic liquid consisting of a cation without hydroxyl groups and a carboxylate anion, and an ester compound with long-chain acyl groups containing 8 to 18 carbon atoms, a step of adding another ester compound with short-chain acyl groups, containing 2 to 4 carbon atoms, to the mixture, followed by carrying out a reaction, and a step of adding the reaction solution to a poor solvent to carry out precipitation of the composite material according to any one of (1) to (4) above. (7) The method for producing the composite material according to (6) above, wherein the moderate solvent is water. (8) The method for producing the composite material according to (6) or (7) above, wherein a cation of the ionic liquid is based on an imidazolium cation.

[0008] The present description claims priority for the present application, based on Japanese patent application No. 2018-159416, the disclosure of which is incorporated herein. Advantageous effects of the invention

[0009] According to the present invention, a composite material can be obtained using a lignocellulosic biomass as a raw material. This composite material comprises three components, namely a cellulose derivative, a hemicellulose derivative, and a lignin derivative, which become integrally compatible or bond together. This composite material possesses the mechanical strength and stiffness of the cellulose derivative, the flexibility of the hemicellulose derivative, and the properties of the lignin derivative, such as UV resistance, high stiffness, high thermal insulation, and high sound insulation, with a good balance of these properties. Furthermore, since this composite material exhibits good thermoformability, it can be used in injection molding. Therefore, the present composite material can preferably be used as a thermoplastic resin material in 3D printing and similar applications. Brief description of the drawings [ Fig.1] The Fig. Figure 1 is a graph showing the results obtained by measuring the materials of Example 1 and Comparison Examples 1 and 2 using a flow test device. [ Fig. 2] The Fig. Figure 2 is a stress-strain curve of the materials of Example 1 and comparison examples 2 and 4. Description of the embodiments

[0010] The present invention is described in detail below.

[0011] In the composite material of the present invention, some hydroxyl groups of a lignocellulosic biomass are esterified. The esterified section has short-chain acyl groups with 2 to 4 carbon atoms and long-chain acyl groups with 8 to 18 carbon atoms (provided that the number of carbon atoms contained in the long-chain acyl group is greater than the number of carbon atoms contained in the short-chain acyl group).

[0012] Any material may be used as a lignocellulosic biomass, provided it is a multi-component material containing cellulose, hemicellulose, and lignin. Examples of materials that may be used as a lignocellulosic biomass include all types of wood-based materials, such as plants, chips of softwoods like cedar or hardwoods, diluted woody materials, construction waste materials, and mushroom waste beds. Materials from angiosperms, in which the main hemicellulose component of the biomass feedstock is glucurone xylan, are preferred. As a specific example, a lignocellulosic biomass may be appropriately selected and used from woody materials such as bagasse (sugarcane residue), kenaf, bamboo or eucalyptus, ginkgo, or a mixture of these two or more types.Preferably, bagasse, eucalyptus or bamboo is used.

[0013] Examples of short-chain acyl groups with 2 to 4 carbon atoms can include saturated or unsaturated aliphatic acyl groups with 2 to 4 carbon atoms and aromatic acyl groups. Here, the number of carbon atoms in the short-chain acyl group refers to the number of carbon atoms, including those in a carbonyl group within the acyl group. The carbon chain can be either linear or branched. Specific examples include acetyl groups, propionyl groups, butyryl groups, and isobutyryl groups. Among these, acetyl groups are preferred.

[0014] An example of a long-chain acyl group with 8 to 18 carbon atoms can be a saturated or unsaturated, aliphatic or aromatic acyl group with 8 to 18 carbon atoms. Here, the number of carbon atoms contained in the long-chain acyl group represents the number of carbon atoms, including those contained in a carbonyl group within the acyl group. The carbon chain can be either linear or branched. Specific examples include saturated or unsaturated aliphatic acyl groups such as propionyl, butyryl, isobutyryl, pentanoyl, hexanoyl, ethylhexanoyl, heptanoyl, decanoyl, stearoyl, or oleoyl groups, and aromatic acyl groups such as benzoyl, toluoyl, or naphthoyl.

[0015] In particular, both the short-chain acyl group and the long-chain acyl group are preferably alkanoyl groups. Furthermore, the difference between the number of carbon atoms in the short-chain acyl group and the number of carbon atoms in the long-chain acyl group is preferably 3 or more, and more preferably 4 or more. A preferred example where the difference in the number of carbon atoms is 3 or more is a case where the short-chain acyl group is an acetyl group, while the long-chain acyl group is a decanoyl group.

[0016] The molar ratio between the short-chain acyl groups and the long-chain acyl groups in the composite material is not particularly restricted. If the ratio of long-chain acyl groups is too high, this is undesirable because the composite material becomes waxy. Conversely, if the ratio of short-chain acyl groups is too high, the crystal structure in the composite material is not disrupted and is preserved, resulting in a high forming temperature and a deterioration of the thermoformability. Therefore, taking these equilibria into account, the molar ratio between the short-chain acyl groups and the long-chain acyl groups in the composite material is determined as appropriate in each case. In particular, the molar ratio between the short-chain acyl groups and the long-chain acyl groups is preferably adjusted to a range within 7:1 to 1:3.The molar ratio between the short-chain acyl groups and the long-chain acyl groups is more preferably within a range of 6:1 and 2:3. The molar ratio between the short-chain acyl groups and the long-chain acyl groups can be adjusted as appropriate by applying a method such as... 1 H-NMR analysis, can be measured.

[0017] If the ratio of unreacted hydroxyl groups in the composite material is too high, the desired improvement in thermoformability cannot be achieved. Therefore, it is desirable for such unreacted hydroxyl groups to be present in small quantities. In particular, while the exact amount of unreacted hydroxyl groups cannot be precisely determined because it varies depending on the types of short-chain and long-chain acyl groups, etc., the percentage of substitution with both short-chain and long-chain acyl groups is preferably 75 mol% or more. That is, the molar ratio of unreacted hydroxyl groups to the total of esterified hydroxyl groups and unreacted hydroxyl groups is preferably 0% to 25%, and more preferably 0% to 5%.The percentage of substitution with the short-chain acyl groups and the long-chain acyl groups, and the amount of unreacted hydroxy groups, can be determined as appropriate by applying a method such as . 31 P-NMR analysis, can be measured.

[0018] In the composite material of the present invention, some hydroxyl groups are esterified with two types of acyl groups, namely short-chain acyl groups and long-chain acyl groups. However, if required, some other hydroxyl groups not esterified with such short-chain or long-chain acyl groups can be further substituted with other groups. For example, hydroxyl groups other than those esterified with the short-chain or long-chain acyl groups can be further esterified with other third acyl groups. The molar ratio of such hydroxyl groups substituted with groups other than the short-chain or long-chain acyl groups is preferably less than 40% in all hydroxyl groups (including substituted hydroxyl groups such as esterified hydroxyl groups).

[0019] The composite material of the present invention has a structure in which three components, namely cellulose esters, hemicellulose esters, and lignin esters, are compatible with one another. The content of each component is not subject to any particular limitation, and, for example, the content of the lignin ester is preferably 1 to 30 wt% and more preferably 1 to 10 wt%, based on the total mass of the composite material. Furthermore, the content of the hemicellulose ester is 1 to 30 wt% and more preferably 1 to 10 wt%, based on the total mass of the composite material.

[0020] Since the aforementioned composite material contains both short-chain and long-chain acyl groups, it becomes a thermoplastic resin with excellent thermoformability. Furthermore, the aforementioned composite material exhibits mechanical strength and stiffness derived from the cellulose ester, flexibility and UV resistance derived from the hemicellulose ester, high stiffness and thermal insulation properties, and high sound insulation properties derived from the lignin ester, thus making the composite material suitable for various applications. The composite material of the present invention can be used in injection molding and can also be wound into a filament form by melt spinning. Consequently, the present composite material can be used as a thermoplastic resin in 3D printing.

[0021] Furthermore, the composite material of the present invention can also be used as a multi-component composite material that is mixed with another organic or inorganic material. In particular, inorganic fibers such as carbon fibers or glass fibers are mixed with the present composite material so that carbon fiber or glass fiber reinforced plastics can be produced. In addition, the present composite material can also be mixed with organic fibers such as cellulose fibers or lignocellulose fibers. Moreover, the composite material can be used as a polymer alloy with polyolefin, such as polypropylene, or with an existing plastic material, such as polylactic acid or polycarbonate.The lignin component contained in the composite material is an aromatic polymer, and this aromatic polymer has a chemical affinity for the surface of carbon fibers or an existing plastic material containing an aromatic ring, such as polycarbonate. Utilizing these properties, the composite material of the present invention can preferably be used as a resin material for the production of carbon fiber reinforced plastics. Furthermore, acyl groups, such as the alkanoyl groups contained in the composite material of the present invention, also exhibit a favorable affinity for hydrocarbon plastics, such as polyolefin, according to a hydrophobic interaction acting between molecules (mainly van der Waals forces).Furthermore, since unreacted hydroxy groups generate hydrogen bonds with the surfaces of cellulose fibers, lignocellulose fibers and polylactic acids, the present composite material can be used as a multi-component composite material with excellent compatibility, which can be used for various applications.

[0022] Next, a process for manufacturing the composite material described above will be described.

[0023] The process for producing the composite material of the present invention comprises: a step of carrying out a reaction in a mixture comprising a lignocellulosic biomass, an ionic liquid consisting of a cation without hydroxyl groups and a carboxylate anion, and an ester compound with long-chain acyl groups having 8 to 18 carbon atoms, a step of adding an ester compound with short-chain acyl groups having 2 to 4 carbon atoms to the mixture, followed by carrying out a reaction, and a step of adding the reaction solution to a poor solvent to carry out precipitation.

[0024] The lignocellulosic biomass used as a raw material is as described above. It should be noted that the lignocellulosic biomass, when used as a raw material, can undergo various pretreatments, such as grinding and drying, as required before being processed.

[0025] The ionic liquid used in the present invention is composed of a cation without hydroxyl groups and a carboxylate anion (RCOO). -(R represents a linear or branched alkyl group containing 1 to 3 carbon atoms, etc.). Such an ionic liquid acts as an effective organocatalyst in a derivatization reaction for a lignocellulosic biomass in the present invention. Furthermore, as in the case of the following choline-acetic acid, if a cation has a hydroxyl group, the ionic liquid itself becomes a reactant, and no biomass derivative of interest (composite material) can be obtained in an unsuitable manner.

[0026] In particular, an imidazolium salt with a cation specified by the following formula (1) (imidazolium-based ionic liquid) is preferred as a cation of the ionic liquid, but is not limited thereto. where R 1 and R 2each independently represent an alkyl group, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group, and R 3 to R 5 each independently represents hydrogen, an alkenyl group, an alkoxyalkyl group, or a substituted or unsubstituted phenyl group.

[0027] Examples of the alkyl group described above can include linear or branched alkyl groups with 1 to 20 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a butyl group, a hexyl group, or an octyl group. A sulfo group can be bonded to the ends of these alkyl groups. Examples of the alkenyl group can include linear or branched alkenyl groups with 1 to 20 carbon atoms, such as a vinyl group, a 1-propenyl group, a 2-propenyl group, a 1-butenyl group, a 2-butenyl group, a 1-pentenyl group, a 2-pentenyl group, a 1-hexenyl group, a 2-hexenyl group, or a 1-octenyl group. Examples of alkoxyalkyl groups can include linear or branched alkoxyalkyl groups with 2 to 20 carbon atoms, such as a methoxymethyl group, an ethoxymethyl group, a 1-methoxyethyl group, a 2-methoxyethyl group, a 1-ethoxyethyl group, or a 2-ethoxyethyl group.Furthermore, examples of substituted or unsubstituted phenyl groups may include phenyl groups that may be substituted with one or two groups selected from a hydroxy group, a halogen atom, a lower alkoxy group, a lower alkenyl group, a methylsulfonyloxy group, a substituted or unsubstituted lower alkyl group, a substituted or unsubstituted amino group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted phenoxy group, and a substituted or unsubstituted pyridyl group.

[0028] Examples of the ionic liquid preferably used in the present invention may include, but are not limited to, the following compounds.

[0029] The ionic liquid described above acts as a solvent for the biomass raw material, disrupting the layered structure of cellulose, hemicellulose, and lignin within it and mitigating physical interactions between the individual components. Simultaneously, a carbene generated from an imidazolium cation or a carboxylate anion acts as a catalyst, thus accelerating the derivatization of the cellulose, hemicellulose, and lignin components that comprise the biomass raw material.For example, in an ionic liquid of 1-ethyl-3-methylimidazolium acetate (EmimOAc), a biomass, vinyl decanoate (serving as an ester compound with long-chain acyl groups), and isopropenyl acetate (serving as an ester compound with short-chain acyl groups) are allowed to react with one another, so that the ionic liquid acts as a catalyst, as mentioned above, and an acetylated and decanoylated biomass (composite material) is produced as a result of the transesterification reactions. In a lignin molecule, hydroxyl groups are present bonded to aromatic carbons and hydroxyl groups bonded to aliphatic carbons. According to the present invention, both can be substituted by the hydroxyl groups.

[0030] The concentration of the biomass raw material in the ionic liquid, which serves as a solvent, varies depending on the type or molecular weight of the biomass and is not subject to any particular limitation. The weight of the ionic liquid is preferably set to twice or more the weight of the biomass raw material, and in particular, the concentration of the biomass raw material in the ionic liquid is preferably set to 3% to 6% by weight.

[0031] Alternatively, the ionic liquid can be used in a co-solvent system with an organic solvent. In this case, the weight of the ionic liquid is preferably set to twice or more the weight of the biomass feedstock. The amount of ionic liquid can be reduced within this range, and the remainder is substituted with an organic solvent, thus lowering the production costs of the individual derivatives.

[0032] The organic solvent used as a co-solvent may, if necessary, be selected from various organic solvents that do not react with the ionic liquid, taking into account its solubility towards a biomass derivative (composite material) being generated, etc. Specific examples of organic solvents used herein may include acetonitrile, tetrahydrofuran (THF), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), 1,3-dioxolane, and 1,4-dioxane. Among these, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), 1,3-dioxolane, and the like are preferred, although the organic solvents used herein are not subject to any restriction. Chloroform is generally unsuitable as an organic solvent in many cases herein because it can react with some ionic liquids, such as 1-ethyl-3-methylimidazolium acetate (EmimOAc).However, chloroform is not excluded from the scope of the present invention.

[0033] The ester to be reacted can be a compound corresponding to the short-chain and long-chain acyl groups to be introduced. Specific examples of esters can include compounds derived from isopropenyl carboxylates, such as isopropenyl acetate, and carboxylic esters, such as vinyl carboxylates or methyl carboxylate. Originally, carboxylic esters were known as extremely stable chemical substances, unlike carboxylic anhydrides, etc. Consequently, to initiate a transesterification reaction, it was essential to use an additional catalyst. In general transesterification reactions, a highly activated carbonyl compound with corrosive properties (e.g., carboxylic anhydride or carboxylic halide (chloride, bromide, etc.)) was used to accelerate the reaction.In the present invention, since the ionic liquid serves not only as a solvent but also as a catalyst, derivatization can be carried out by means of a transesterification reaction without the separate addition of a catalyst.

[0034] The amount of such an ester compound varies depending on the type of biomass raw material, etc. For example, an ester compound with short-chain acyl groups and an ester compound with long-chain acyl groups are preferably reacted with a biomass raw material in a total amount of 10 to 30 equivalents to 1 equivalent of hydroxy groups present in the biomass raw material. Furthermore, it is preferred to add an ester compound with short-chain acyl groups to a biomass raw material in a disproportionately larger amount than that of an ester compound with long-chain acyl groups.In particular, it is preferred to add 10 to 29 equivalents of the ester compound with short-chain acyl groups and 0.1 to 1 equivalent of the ester compound with long-chain acyl groups to a biomass raw material with respect to 1 equivalent of hydroxy groups present in the biomass raw material, but the amounts of these ester compounds are not limited thereto.

[0035] Furthermore, the reaction conditions are not subject to any particular restrictions, as long as they are conditions under which the ionic liquid acts as a catalyst and the reaction proceeds. Such reaction conditions can be determined as appropriate depending on the type of biomass feedstock, etc. For example, a mixture of lignocellulosic biomass, an ionic liquid, and an ester compound is stirred under a nitrogen or argon atmosphere at a temperature of 10°C to 80°C for 0.5 to 48 hours to allow the reaction to proceed. The reaction time depends on the temperature. For example, if the reaction is carried out at 50°C, the reaction time is preferably set to 2 hours or more, and if the reaction is carried out at 10°C, the reaction time is preferably set to a longer period.

[0036] The ester compound with short-chain acyl groups and the ester compound with long-chain acyl groups can be added simultaneously to a mixture of lignocellulosic biomass and an ionic liquid. However, preferably the ester compound with long-chain acyl groups is added first to a mixture of biomass containing lignocellulosic liquid and an ionic liquid, followed by the execution of a reaction, and subsequently the ester compound with short-chain acyl groups is added to the reaction mixture, followed by the execution of a reaction.By allowing the ester compound with short-chain acyl groups to react with the unreacted hydroxy groups in the reaction mixture after the reaction of the ester compound with long-chain acyl groups, both the long-chain acyl groups and the short-chain acyl groups can be easily introduced into the mixture with a targeted ratio for thermal processability.

[0037] After completion of the reaction, insoluble components and impurities are removed from the reaction solution, if necessary, by a process such as reduced-pressure filtration and are appropriately concentrated. The reaction solution is then added to a poor solvent, and precipitation is carried out to obtain a composite material of interest. The resulting composite material is separated by filtration or the like and then dried so that it can be used as a thermoplastic resin material for various applications. The poor solvent used in the precipitation is not subject to any particular restrictions and may include water, hexane, alcohols such as methanol, and the like. Preferably, the poor solvent is water.

[0038] In addition, the ionic liquid used can be recovered by passing the solution obtained during each process, such as the solution after separating the produced composite material, through a cation exchange resin or the like. The recovered ionic liquid can be remixed with biomass as a raw material and used as a solvent and / or a catalyst for the reaction of the present invention. Examples

[0039] The present invention is described in more detail below by means of examples and comparative examples, with the proviso that the technical scope of the present invention is not limited thereto. 1. Composite material production (Example 1)

[0040] A residue (bagasse) of sugarcane juice was used as a lignocellulose biomass sample. The bagasse was pulverized into granules with a diameter of 250 µm or less and then subjected to a delapidation treatment. The bagasse (6 g, 6 wt% / EmimOAc) was added to 1-ethyl-3-methylimidazolium acetate (EmimOAc) / dimethyl sulfoxide (DMSO) (volume ratio: 1 : 1.6), and the resulting mixture was stirred under an argon atmosphere at 110°C for 16 hours to ensure complete dissolution of the sample. The resulting homogeneous solution was cooled to 80°C, and then vinyl decanoate (4.2 mL, 0.25 mol equivalents to 1 equivalent of hydroxy groups present in the bagasse), an ester compound with long-chain acyl groups, was added to the solution. The mixed solution was stirred at 80°C for 30 minutes.Subsequently, isopropenyl acetate (200 mL, 25 equivalents of 1 equivalent of hydroxyl groups present in the bagasse) was added to the reaction solution as an ester compound with short-chain acyl groups, and the resulting mixture was stirred at 80°C for 30 minutes. After completion of the reaction, the resulting black homogeneous solution was added dropwise to acetone (1.2 L), and the resulting mixture was then stirred at room temperature for 1 hour. Insoluble components were then removed by filtration under reduced pressure, and the filtrate was concentrated, followed by precipitation in distilled water (6 L) to obtain a bagasse derivative of interest (a composite material, Bagasse AcDe). The reaction formula is shown below. (Examples 2 and 3)

[0041] A composite material was produced by carrying out esterification in the same manner as in Example 1 described above, except that bamboo (Example 2) or eucalyptus (Example 3) was used as a lignocellulosic biomass (a raw material) instead of bagasse. (Example 4)

[0042] A composite material was prepared in the same way as that of Example 1 described above, with the exception that the amount of isopropenyl acetate added was changed, thus altering the ratio of unreacted hydroxy groups, short-chain acyl groups and long-chain acyl groups. (Examples 5 and 6)

[0043] A composite material was prepared in the same way as that of Example 1 described above, with the exception that the amount of vinyl decanoate added was changed, thus altering the ratio of unreacted hydroxy groups, short-chain acyl groups, and long-chain acyl groups. (Examples 7 to 9)

[0044] A composite material was prepared in the same manner as that of Example 1 described above, except that vinyl propionate (Example 7), vinyl butyrate (Example 8) or vinyl pivalate (Example 9) was added as an ester compound with a short-chain acyl group, instead of isopropenyl acetate. (Example 10)

[0045] A composite material was prepared in the same manner as that of Example 1 described above, except that vinyl stearate (Example 10) was added as an ester compound with long-chain acyl groups instead of vinyl decanoate. (Comparative example 1)

[0046] Six grams of bagasse, pulverized to a particle size of 250 µm or less, were weighed into a 1-liter Schlenk flask, and then 100 grams of 1-ethyl-3-methylimidazolium and 150 mL of dimethyl sulfoxide were added. The resulting mixture was stirred under an argon atmosphere at 110°C for 16 hours until the sample was completely dissolved. The homogeneous solution was cooled to 80°C, and a small amount of vinyl decanoate was added, followed by stirring at 80°C for 30 minutes. Subsequently, an excessive amount of isopropenyl acetate was added to the reaction mixture, and the resulting mixture was stirred at 80°C for 30 minutes.After completion of the reaction, the reaction solution was mixed with an excess amount of methanol for precipitation, and the precipitate was then filtered and washed, yielding a powder of an esterified polysaccharide with long-chain and short-chain acyl groups (cellulose ester + hemicellulose ester, polysaccharide-AcDe). Simultaneously, the lignin component was separated as a methanol filtrate. (Comparative example 2)

[0047] An esterified cellulose with long-chain acyl groups and short-chain acyl groups (Cellulose-AcDe) was produced in the same way as in the comparison example 1 described above, with the exceptions that a cellulose pulp containing neither lignin nor hemicellulose was used as a raw material and that no pulverization treatment was carried out. (Comparative examples 3 to 6)

[0048] The following materials were produced for comparison examples 3 to 6. Comparative example 3: Cellulose acetate butyrate (a commercially available product) Comparison example 4: Polypropylene (a commercially available product) Example of comparison 5: Nylon-6 (trademark, a commercially available product) Comparison example 6: ABS resin (a commercially available product) 2. Evaluation of thermal fluidity

[0049] The composite material (bagasse-AcDe) from Example 1, the esterified polysaccharide material (polysaccharide-AcDe) from Comparative Example 1, and the esterified cellulose material (cellulose-AcDe) from Comparative Example 2 were evaluated with respect to their thermal fluidity. In particular, the thermal fluidity (softening temperature Tf) was determined. Erweichung / Melt initiation temperature T Fluss / Offset temperature T offsetThe melting potential of each sample was evaluated according to JIS K7210 (ISO 1133) using a constant force extrusion-type flow tester (manufactured by Shimadzu Corporation; brand name: CFT-500EX). The measurement initiation temperature was set to 50°C, the test pressure to 0.49 MPa, the nozzle orifice diameter to 1 mm, and the nozzle length to 10 mm. The temperature at the point when a piston moved 5 mm from the initiation of sample melting was defined as the offset temperature. The measurement results are presented in the Fig. 1 shown.

[0050] As in the Fig.As shown in Figure 1, the thermal flow of all resins in Examples 1 and Comparative Examples 1 and 2 was confirmed due to suitable substitutions with long-chain and short-chain acyl groups. The offset temperature of Comparative Example 2 (Cellulose-AcDe) was 266°C, whereas the offset temperature of Comparative Example 1 (Polysaccharide-AcDe), consisting of cellulose ester / hemicellulose ester, was 264°C. Both Comparative Examples 1 and 2 were solid and fragile molded products. Furthermore, the offset temperature of the composite material (Bagasse AcDe), which contained lignin esters in addition to the esterified polysaccharide as in Comparative Example 1, was 194°C, and it was suggested that this composite material exhibited excellent thermal processability and also high flexibility.The offset temperature of the composite material of Example 1 decreased by 60°C or more than those of comparison Examples 1 and 2, and lignin esters, it was suggested, acted as a plasticizing agent. 3. Pull test

[0051] Individual materials obtained as Example 1 and Comparative Examples 2 and 4 were subjected to injection molding prior to a tensile test, as described below. Using a kneading machine (manufactured by Xplore Instruments; brand name: Xplore MC5), individual materials were kneaded. During the kneading process, the temperature of the kneading chamber was set to 170°C, and the rotation speed was set to 60 rpm. Each material was fed into a feed opening of the kneading machine and then kneaded for 10 minutes. Using an injection molding machine (manufactured by Imoto Machinery Co., Ltd.; brand name: IMC-5705), a dumbbell-type test piece was produced from the kneaded product described above, in accordance with JIS K7161. A tensile test was then performed on the test piece using a universal testing machine (manufactured by Shimadzu Corporation; brand name: AG-5kN Xplus). The drawing speed was set to 0.5 mm / min.The results are in the . Fig. 2 shown.

[0052] Based on the in the Fig. The results shown in Example 2 revealed that the material (cellulose-AcDe) of Comparison Example 2 had solid strength, but that this material fractured under a deformation of 2% to 3% and was therefore insufficient with respect to flexibility or elongation. In contrast, the composite material of Example 1 exhibited an elongation approximately three times that of the material of Comparison Example 2, suggesting that the material possessed flexibility. Furthermore, the composite material of Example 1 had a tensile strength comparable to that of the polypropylene material of Comparison Example 4. 4. Other measurements

[0053] Individual materials from examples 1 to 10 and comparison examples 1 to 3 were obtained using 1H-NMR measured, with regard to the ratio between long-chain acyl groups and short-chain acyl groups.

[0054] Furthermore, with regard to the individual materials of Examples 1 to 10 and Comparative Examples 1 to 3, the amount of unreacted hydroxy groups was determined by 31 P-NMR analysis (the method described in S. Suzuki et al., RSC Adv. 2018, 8, 21768-21776) estimated.

[0055] Furthermore, for each of the materials in Examples 1 to 10 and Comparison Examples 1 and 2, the surface area and flexibility of each molded product were subjected to sensory evaluation after measurement using a flow tester. Additionally, the glass transition temperature (Tg) was determined by differential scanning calorimetry (DSC). The measurement results are summarized in the following table. In the table below, the percentage of substitution for long-chain and short-chain acyl groups in Example 1 is identical to that in Example 4. Note that the amount of unreacted hydroxyl groups in Example 4 was greater than in Example 1, and both the percentage of substitution for long-chain and short-chain acyl groups were slightly lower in Example 4 than in Example 1. [Table 1] Synthesized product a Substitution percentage (mol-%) Forming temperature (°C) Molded product b Long chain Short necklace Hydroxyl group Tg T Fluss T offset Surface Flexibility Example 1 BagasseAcDe 22 76 1,4 94 160 194 ◯ ◯ 2 Bamboo AcDe 23 74 3,2 95 163 191 ◯ ◯ 3 EucalyptusAcDe 22 74 3,9 94 160 181 ◯ ◯ 4 BagasseAcDe 22 76 2,3 94 154 186 △ ◯ 5 BagasseAcDe 46 52 2,7 91 138 166 ◯ ◯ 6 BagasseAcDe 58 39 3,3 95 68 75 ◯ ◯ 7 BagassePrDe 10 88 1,2 67 90 115 ◯ ◯ 8 BagasseBuDe 15 83 1,7 65 65 70 ◯ ◯ 9 Bagasse Pide 15 83 3,1 63 70 97 ◯ ◯ 10 BagasseAcSt 23 75 1,9 93 142 166 ◯ △ Comparative example 1 Polysaccharide AcDe 24 76 0,6 100 219 264 × × 2 CelluloseAcDe 12 87 0,4 104 247 266 △ × 3 CelluloseAcBu 24 69 7 234 245 4 Polypropylen 180 184 5 Nylon-6 224 230 6 ABS 163 208 a Bagasse XY: (X: short-chain acyl group, Y: long-chain acyl group) b Sensory assessment of the surface / flexibility of the molded product after measuring with a flow test device (Surface) ◯: smooth, △: some unevenness; x: rough (Flexibility) ◯: can be wound up; △: flexible but fragile, ×: rigid or stiff (breaks without bending)

[0056] As shown in the table above, it was found that the composite materials of examples 1 to 10 with short-chain acyl groups with 2 to 4 carbon atoms and long-chain acyl groups with 8 to 16 carbon atoms exhibit a low offset temperature T Offset They exhibited superior properties compared to those of a polysaccharide ester (Comparison Example 1) or cellulose ester (Comparison Examples 2 and 3) and were excellent with regard to thermal processability. Furthermore, in the case of the composite materials from Examples 1 to 10, only one glass transition point was observed, and therefore it was proposed that individual components derived from cellulose, hemicellulose, and lignin were fully compatible with each other.

[0057] The entire publication, patent and patent application cited herein are also included by reference.

Claims

[1] Composite material in which some hydroxy groups of a lignocellulosic biomass are esterified, wherein the esterified section has short-chain acyl groups with 2 to 4 carbon atoms and long-chain acyl groups with 8 to 18 carbon atoms. [2] Composite material according to claim 1, wherein both the short-chain acyl groups and the long-chain acyl groups are alkanoyl groups. [3] Composite material according to claim 1 or 2, wherein the molar ratio between the short-chain acyl groups and the long-chain acyl groups is as follows: the short-chain acyl groups : the long-chain acyl groups = 7 : 1 to 1 :

3. [4] Composite material according to any one of claims 1 to 3, wherein the substitution percentage with respect to the short-chain acyl groups and the long-chain acyl groups is 75 mol% or more. [5] Multi-component composite material formed by mixing the composite material according to any one of claims 1 to 4 with another organic or inorganic material. [6] Method for producing the composite material according to any one of claims 1 to 4, comprising: a step in carrying out a reaction in a mixture comprising a biomass containing lignocellulose, an ionic liquid consisting of a cation without hydroxyl groups and a carboxylate anion, and an ester compound with long-chain acyl groups containing 8 to 18 carbon atoms, a step of adding another ester compound with short-chain acyl groups, containing 2 to 4 carbon atoms, to the mixture, followed by carrying out a reaction, and a step of adding the reaction solution to a poor solvent to carry out precipitation of the composite material according to any one of claims 1 to 4. [7] Method for producing the composite material according to claim 6, wherein the poor solvent is water. [8] Method for producing the composite material according to claim 6 or 7, wherein a cation of the ionic liquid is based on an imidazolium cation.

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