Composite material, structural member, and recycling method using biomass-derived resin as a base material

Abstract

To provide a composite material which contains a biomass-derived resin as a base material and has high proportional limit strength, a structural member using the same, and a recycling method of the same.SOLUTION: A composite material 10 is a composite material which contains a biomass-derived resin as a base material and contains an additive, wherein a relative difference between an interval of functional groups arrayed on a molecular chain of a base material 1 and an interval between a functional group arrayed on the structure of an additive 2 and an atom forming an interaction with the functional group is 3% or less. A structural member is formed of a composite material which contains a biomass-derived resin as a base material and contains an additive, wherein a relative difference between an interval of functional groups arrayed on a molecular chain of a base material 1 and an interval between a functional group arrayed on the structure of an additive 2 and an atom forming an interaction with the functional group is 3% or less. A recycling method of a composite material is a recycling method of a composite material which contains a biomass-derived resin as a base material and contains an additive, and includes a step of immersing a used composite material in a reductive solution, and decomposing the additive.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a composite material using a biomass-derived resin as a base material, a structural member using the same, and a method for recycling the same. [Background technology]

[0002] Biomass-derived resins are produced using biomass such as resource plants and biological waste as raw materials. Because biomass-derived resins do not contribute to an increase in CO2 emissions when burned, they are attracting attention as materials that contribute to carbon neutrality. Known biomass-derived resins include polylactic acid produced using lactic acid fermentation, polyamide 11 made from castor oil, and polyamide 4 made from 2-pyrrolidone derived from glutamic acid.

[0003] Biomass-derived resins are environmentally friendly materials with low CO2 emissions, but they have issues with strength and rigidity. When using resin materials as structural components, the proportional limit is an important factor in design. However, biomass-derived resins have the disadvantage of having a small proportional limit. Therefore, the current uses of biomass-derived resins are limited to plastic tableware, packaging film, and exterior and reinforcing materials for personal computers.

[0004] BACKGROUND ART Conventionally, a method of blending a filler (filling material) has been known as a method for improving the mechanical properties of a resin material.

[0005] Patent Document 1 describes a semi-aromatic polyamide resin composition that has excellent mechanical properties, heat resistance, gate cut-off properties, and sliding properties. The semi-aromatic polyamide resin composition contains one or more spherical inorganic fillers selected from the group consisting of silica and glass beads, and one or more inorganic fillers selected from the group consisting of particulate inorganic fillers and fibrous inorganic fillers. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-193247 Summary of the Invention [Problem to be solved by the invention]

[0007] Biomass-derived resins are required to have improved proportional limit strength in order to be used in applications such as structural members. Resin materials used in general structural members, such as those used in the housings of home appliances such as vacuum cleaners, are expected to have a proportional limit equivalent to or greater than that of polypropylene. However, as in Patent Document 1, simply adjusting the particle shape or dispersion structure of the filler makes it difficult to sufficiently increase the proportional limit of biomass-derived resins.

[0008] Conventional methods for improving proportional limit strength at the filler particle level have the problem of not being able to achieve the proportional limit required for general structural members. In particular, biomass-derived resins are sometimes reused through chemical recycling after use. Biomass-derived resins, which are recycled materials, have a reduced molecular weight due to ultraviolet degradation, thermal degradation, etc., and their proportional limit is also significantly reduced. Therefore, there is a need for a means for improving proportional limit strength that can be applied to such recycled materials.

[0009] Therefore, an object of the present invention is to provide a composite material having a high proportional limit strength and using a biomass-derived resin as a base material, a structural member using the same, and a method for recycling the same. [Means for solving the problem]

[0010] In order to solve the above problems, the composite material according to the present invention is a composite material containing an additive and a biomass-derived resin as a base material, wherein the relative difference between the spacing of functional groups arranged on the molecular chain of the base material and the spacing of atoms that interact with the functional groups arranged on the structure of the additive is 3% or less. the base material is polylactic acid, the additive includes at least one selected from 3,3'-dithiodipropionic acid and gallium (III) oxide, and the concentration of the additive relative to the base material is 3 wt% to 22 wt%; or the base material is polyamide 11, the additive includes yttria-stabilized hafnia having an yttria concentration of 5 wt% to 10 wt%, and the concentration of the additive relative to the base material is 5 wt% to 38 wt%; or the base material is polyamide 4, the additive includes sodium potassium oxide having a potassium oxide concentration of 2 wt% to 5 wt%, and the concentration of the additive relative to the base material is 3 wt% to 38 wt%. do.

[0011] The structural member according to the present invention is a structural member formed of a composite material containing an additive and a biomass-derived resin as a base material, wherein the relative difference between the spacing of functional groups arranged on the molecular chain of the base material and the spacing of atoms that interact with the functional groups arranged on the structure of the additive is 3% or less. The base material is polylactic acid, the additive contains at least one selected from 3,3'-dithiodipropionic acid and gallium (III) oxide, and the concentration of the additive relative to the base material is 3 wt% or more and 22 wt% or less, and the structural member has a bent portion formed into a bent shape or bent by bending, or the base material is polyamide 11, and the additive is yttria-stabilized hafnium having an yttria concentration of 5 wt% or more and 10 wt% or less. The base material is polyamide 4, the additive comprises sodium potassium oxide having a potassium oxide concentration of 2 wt% to 5 wt%, the additive concentration of the additive relative to the base material is 3 wt% to 38 wt%, and the structural member has a bent portion formed or bent into a bent shape. do.

[0012] The method for recycling a composite material according to the present invention is a method for recycling a composite material containing an additive and a biomass-derived resin as a base material, wherein the base material is recycled polylactic acid obtained by recycling used polylactic acid, and the additive contains 3,3'-dithiodipropionic acid; The concentration of the additive relative to the base material is 3 wt % or more and 22 wt % or less, and the method includes a step of immersing the composite material after use in a reducing solution to decompose the additive. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a composite material having a high proportional limit strength and using a biomass-derived resin as a base material, a structural member using the same, and a method for recycling the same. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view schematically showing a composite material according to an embodiment of the present invention. [Figure 2] FIG. 10 is a graph showing stress-strain curves of composite materials measured by changing the particle size of the additive. [Figure 3] FIG. 10 is a graph showing the analysis results of the relationship between the proportional limit strength of a composite material and the particle size of an additive. [Figure 4] FIG. 10 is a graph showing the analysis results of the relationship between the proportional limit strength of a composite material and the particle size of an additive. [Figure 5] FIG. 10 is a graph showing the analysis results of the relationship between the proportional limit strength of a composite material and the particle size of an additive. [Figure 6] FIG. 10 is a graph showing the analysis results of the relationship between the proportional limit strength of a composite material and the concentration of an additive. [Figure 7] FIG. 10 is a graph showing the analysis results of the relationship between the proportional limit strength of a composite material and the concentration of an additive. [Figure 8] FIG. 10 is a graph showing the analysis results of the relationship between the proportional limit strength of a composite material and the concentration of an additive. [Figure 9] FIG. 10 is a diagram showing the results of an analysis of the atomic arrangement of a base material to which no additives are added. [Figure 10] FIG. 10 is a diagram showing the results of an analysis of the atomic arrangement of a base material to which no additives are added. [Figure 11] FIG. 10 is a diagram showing the results of an analysis of the atomic arrangement of a base material to which no additives are added. [Figure 12] FIG. 10 is a diagram showing the results of an analysis of the atomic arrangement of a base material to which an additive has been added. [Figure 13] FIG. 10 is a diagram showing the results of an analysis of the atomic arrangement of a base material to which an additive has been added. [Figure 14] FIG. 10 is a diagram showing the results of an analysis of the atomic arrangement of a base material to which an additive has been added. [Figure 15] FIG. 10 is a diagram showing the results of an analysis of the atomic arrangement of a base material to which an additive has been added. [Figure 16] FIG. 10 is a diagram showing the results of an analysis of the atomic arrangement of a base material to which an additive has been added. [Figure 17] 1 is a diagram showing a method for recycling a composite material according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] A composite material according to one embodiment of the present invention, a structural member using the same, and a method for recycling the composite material will be described below with reference to the drawings. In the following drawings, common components are designated by the same reference numerals, and duplicated descriptions will be omitted.

[0016] Fig. 1 is a cross-sectional view schematically illustrating a composite material according to an embodiment of the present invention, in which reference numeral 10 denotes the composite material, reference numeral 1 denotes the base material which is a biomass-derived resin, reference numeral 2 denotes an additive, and reference numeral 3 denotes the interface between the base material and the additive. 1, a composite material 10 according to this embodiment includes at least a base material 1 that is a biomass-derived resin, and an additive 2 dispersed in the base material 1. The additive 2 includes a specific additive that acts to align molecular chains of the biomass-derived resin at the atomic level.

[0017] As a result of extensive research, the inventors have discovered that in order to improve the mechanical strength, particularly the proportional limit strength (proportional limit), of composite materials using biomass-derived resin as a base material, it is effective to add an additive that has the effect of aligning the molecular chains of the biomass-derived resin, thereby improving the adhesive strength between the molecular chains at the atomic level, and have completed the present invention.

[0018] Furthermore, we found that additives that have the effect of aligning the molecular chains of biomass-derived resins are effective when the relative difference between the spacing of the characteristic functional groups arranged on the molecular chains of the base material, which is biomass-derived resin, and the spacing of the characteristic atoms arranged on the structure of the additive is 3% or less.

[0019] The characteristic functional group refers to a functional group possessed by the biomass-derived resin that is a characteristic functional group capable of forming a strong interaction with a specific atom constituting the additive. The characteristic atom refers to an atom constituting the additive that is a characteristic atom capable of forming a strong interaction with a specific functional group possessed by the biomass-derived resin.

[0020] The characteristic functional group and the characteristic atom are sites that form stronger interactions than other functional groups and atoms, and are preferably sites that form the strongest interactions within a molecule. The interactions are actions that apparently adsorb atoms to each other, and include intermolecular interactions such as electrostatic interactions, permanent dipole interactions, induced dipole interactions, and charge transfer interactions based on electronic states and energy states, as well as complex actions due to repulsive forces and repellent forces generated by other sites within the molecule.

[0021] When such an additive is added, the characteristic functional groups on the molecular chain of the base material 1 and the characteristic atoms on the crystal structure or molecular structure of the additive 2 form a strong interaction and can be arranged in close proximity to each other. The molecular chains constituting the base material 1 and the additive 2 can adhere to each other with high adhesion strength that is stable in terms of electronic state and energy state, as a result of the multiple characteristic functional groups and multiple characteristic atoms being periodically arranged in close proximity to each other.

[0022] As a result, at the interface 3 between the base material 1 and the additive 2, the molecular chains constituting the base material 1 are aligned in an appropriate orientation and conformation relative to the crystalline structure and molecular structure of the additive 2. For the molecular chains aligned relative to the additive 2, other molecular chains are aligned in an appropriate orientation and conformation.

[0023] Therefore, the effect of the specified additive 2 extends not only to the interface 3 between the base material 1 and the additive 2, but also to areas away from the interface 3. The effect of aligning the molecular chains of the biomass-derived resin is achieved over a wide range, starting from the specified additive 2. Aligning the molecular chains improves the adhesive strength between the molecular chains, thereby improving the proportional limit strength of the composite material 10.

[0024] Any suitable resin can be used as the biomass-derived resin forming the base material 1, as long as it is made from biomass. As long as biomass is used as part of the raw material, the biomass-derived resin may use a raw material derived from a fossil fuel as part of the raw material. For example, in addition to a polymer obtained by polymerizing a biomass-derived monomer, a copolymer obtained by copolymerizing a biomass-derived monomer and a fossil fuel-derived monomer can also be used.

[0025] Biomass includes resource plants, biological waste, etc. Specific examples of biomass include crushed plant materials such as corn, sugarcane, sugar beet, wood, and sawdust, plant isolates such as rice straw, wheat straw, rice husks, coconut shells, and bran, plant extract residues such as bagasse, food processing by-products, food waste, oil and fat waste, waste paper, clothing waste, farm waste, and livestock manure.

[0026] The biomass-derived resin forming the base material 1 may be a biodegradable resin that exhibits biodegradability, or a non-biodegradable resin that does not exhibit biodegradability. Using a non-biodegradable resin eliminates the need for incineration or other disposal of the composite material 10 after use, thereby reducing the environmental impact after use. Furthermore, since regeneration through biodegradation is possible, the resource reusability of the composite material 10 can be improved.

[0027] Specific examples of biodegradable resins include polylactic acid (PLA), polyamide 4 (PA4), polyglycolic acid (PGA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polyhydroxyalkanoic acid (PHA), etc. Examples of polyhydroxyalkanoic acid include poly-3-hydroxybutanoic acid (PHB) and polyhydroxyalkanoic acid having 4 to 16 carbon atoms.

[0028] Specific examples of non-biodegradable resins include polyamide 11 (PA11), polyamide 1010 (PA1010), polyamide 1012 (PA1012), polyamide 410 (PA410), polyamide 510 (PA510), polyamide 610 (PA610), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polyethylene furanoate (PEF), polyesters (PEs), polyurethane (PU), polycarbonate (PC), etc.

[0029] Additive 2 is an additive that acts to align the molecular chains of the biomass-derived resin at the atomic level, and has a relative difference of 3% or less between the spacing of the characteristic functional groups arranged on the molecular chains of base material 1, which is a biomass-derived resin, and the spacing of the characteristic atoms arranged on the structure of additive 2. The relative difference means the ratio of the difference between the relatively long interval length and the relatively short interval length to the relatively short interval length ((long interval length - short interval length) / short interval length) [%].

[0030] That is, the combination of the base material 1 and the additive 2 is one in which a relatively strong interaction is formed between the characteristic functional groups of the biomass-derived resin and the characteristic atoms that constitute the additive 2. Furthermore, in such a combination, the spacing between the characteristic functional groups and the spacing between the characteristic atoms are similar, and the characteristic functional groups and the characteristic atoms are regularly arranged in close proximity to each other.

[0031] An inorganic compound or an organic compound may be used as the additive 2. The characteristic atoms constituting the additive 2 may be atoms arranged in the crystalline structure of the inorganic compound, atoms arranged in the molecular structure of the inorganic compound, or atoms arranged in the molecular structure of the organic compound.

[0032] When an organic compound is used as additive 2, it is sufficient that there are at least two characteristic atoms on the molecule of the organic compound that is additive 2. A high molecular weight organic compound having many characteristic atoms may be used as additive 2, or a low molecular weight organic compound having a few characteristic atoms may be used. When a low molecular weight organic compound is used, multiple molecules of additive 2 can be associated with one molecular chain of biomass-derived resin.

[0033] There needs to be at least one type of characteristic functional group on the molecular chain of the biomass-derived resin that interacts with the characteristic atom. In other words, additive 2 needs to have a characteristic atom that can form a stronger interaction with at least one functional group on the monomer that makes up the biomass-derived resin than with other functional groups or moieties. However, it is necessary that such characteristic atoms are arranged regularly and that the spacing between the characteristic atoms matches the spacing between the characteristic functional groups.

[0034] Specific examples of the characteristic functional group possessed by the biomass-derived resin include, but are not limited to, a carbonyl group, an amino group, a hydroxy group, a carboxy group, a benzene ring, a furan ring, an amide bond, an ester bond, a urethane bond, etc. The characteristic functional group is preferably present in a side chain of the biomass-derived resin from the viewpoint of appropriately forming an interaction with the characteristic atom constituting the additive 2.

[0035] In addition to additive 2, which acts to align the molecular chains of the biomass-derived resin, other additives may be added to composite material 10. Examples of other additives include antioxidants, UV absorbers, heat stabilizers, light stabilizers, hydrolysis inhibitors, plasticizers, thickeners, viscosity reducers, flame retardants, lubricants, release agents, conductive agents, antistatic agents, insulating agents, heat insulating materials, foaming agents, thermal conductive agents, pigments, dyes, fluorescent agents, antibacterial agents, and antifungal agents.

[0036] In addition to the additive 2 that acts to align the molecular chains of the biomass-derived resin, a general filler may or may not be added to the composite material 10. General fillers include reinforcing agents that improve strength, rigidity, etc., and fillers. Specific examples of general fillers include silica, talc, mica, clay, calcium carbonate, potassium titanate, carbon, glass fiber, carbon fiber, and aramid fiber.

[0037] In the composite material 10 according to this embodiment, preferred combinations of the base material 1 and the additive 2 and preferred concentrations of the additive 2 are as follows (1) to (3).

[0038] (1) Base material 1 is polylactic acid (PLA) (-[O-CH(CH3)-C(=O)] n -). The additive 2 includes at least one selected from 3,3'-dithiodipropionic acid (DTDPA) and gallium (III) oxide (Ga2O3). The concentration of the additive 2 relative to the base material 1 is 3 wt% or more and 22 wt% or less. The 3,3'-dithiodipropionic acid is added as a monomolecule.

[0039] (2) Base material 1 is polyamide 11 (PA11) (-[NH-(CH2) 10 -C(=O)] n -). Additive 2 includes yttria-stabilized hafnia (HfO3+Y2O3). The concentration of additive 2 relative to base material 1 is 5 wt% or more and 38 wt% or less. The yttria-stabilized hafnia preferably has an yttria concentration of 5 wt% or more and 10 wt% or less.

[0040] (3) Base material 1 is polyamide 4 (PA4) (-[NH-(CH2)3-C(=O)] n-), and additive 2 includes sodium potassium oxide (Na2O+K2O), which is sodium oxide containing potassium oxide. The concentration of additive 2 relative to base material 1 is 3 wt% or more and 38 wt% or less. The sodium potassium oxide preferably has a potassium oxide concentration of 2 wt% or more and 5 wt% or less.

[0041] By combining the above (1) to (3), the relative difference between the spacing between the characteristic functional groups arranged on the molecular chains of the base material 1, which is a biomass-derived resin, and the spacing between the characteristic atoms arranged on the structure of the additive 2 is 3% or less. Because the characteristic functional groups and characteristic atoms are regularly arranged at corresponding positions, the molecular chains of the biomass-derived resin are aligned at the interface 3 between the base material 1 and the additive 2. Furthermore, even in regions away from the interface 3, the molecular chains aligned at the interface 3 serve as starting points for aligning other molecular chains. Because the adhesion strength between molecular chains is improved over a wide range in the base material 1, the proportional limit strength of the composite material 10 can be improved.

[0042] Next, we will show the results of preparing a composite material using biomass-derived resin as the base material and confirming the effects of additives.

[0043] The composite material using biomass-derived resin as the base material was produced by mixing pellets formed from the biomass-derived resin with additive powder, and then melting and kneading the resulting mixture. The mixture was melted and kneaded using a co-rotating twin-screw extruder (manufactured by Coperion). The kneading temperature was 170°C. The screw rotation speed was 150 rpm, and the extrusion rate was 20 kg / h. The extrusion pressure was 0.5 to 0.9 MPa, and the extruded strand was water-cooled.

[0044] The composite materials were molded into specified test specimens and then subjected to tensile tests to measure stress-strain properties. The test specimens were Type A1 multipurpose test specimens in accordance with JIS K7139:2019 Plastics - Test Specimens. The thickness of the test specimens was 4 mm. The test specimens were injection molded using the composite materials and then annealed at 110°C for 4 hours. Test specimens were prepared by varying the particle size and type of additive, and the proportional limit strength (proportional limit) of each composite material was determined based on the stress-strain properties measured in the tensile tests.

[0045] Figure 2 shows the stress-strain curves of composite materials measured with different additive particle sizes. Figure 2 shows the results of measurements using polylactic acid (PLA) as the base material and gallium (III) oxide (Ga2O3) as the additive, with different additive particle sizes. The curves in the figure, from top to bottom, are for average particle sizes of 3 nm, 5 nm, 8 nm, 10 nm, and no additive.

[0046] As shown in Figure 2, the stress-strain curve of a composite material rises linearly from the origin. The proportional limit is the stress limit within which the linear relationship between stress and strain is maintained. If the strain is increased beyond the proportional limit, the elastic limit is reached. If the strain is increased beyond the elastic limit, plastic deformation occurs, leaving residual damage due to the stress.

[0047] Generally, when designing structural components, it is desirable for the material to have a high proportional limit strength. In design, proportional limit strength is given more importance than tensile strength, etc. The higher the proportional limit strength, the less likely a material is to be damaged by stress, and the more mechanically strong the material is in practical use.

[0048] As shown in Figure 2, the smaller the particle size of the additive, the more the proportional limit strength tends to improve. However, the effect of fine particle size of the additive is mainly due to the increase in surface area. The effect of the increase in surface area reaches a plateau as the particle size becomes smaller. This is because if the additive is made too fine, the crystallinity deteriorates and the variation in particle size increases, causing problems in the product.

[0049] Therefore, methods that aim to improve the proportional limit strength at the particle level have limitations in terms of effectiveness, and there is a problem that the proportional limit required for general structural members cannot be achieved. In order to improve the proportional limit strength of composite materials that use biomass-derived resin as a matrix, it is effective to add an additive that has the effect of aligning the molecular chains that make up the matrix, thereby improving the adhesion strength between the molecular chains at the atomic level.

[0050] Figure 3 shows the analysis results of the relationship between the proportional limit strength of the composite material and the particle size of the additive. Figure 3 shows the results of measurements using polylactic acid (PLA) as the base material and changing the type of additive. The concentration of the additive was 10 wt% in all cases.

[0051] The dotted line in the figure shows the results when 3,3'-dithiodipropionic acid (DTDPA) was added. The solid line in the figure shows the results when gallium (III) oxide (Ga2O3) was added. The two-dot-dashed line in the figure shows the results when silica (SiO2) was added. The single-dot-dashed line in the figure shows the results when no additives were added. The dashed line in the figure shows the results when a copolymer of lactic acid and 3,3'-dithiodipropionic acid (p[PLA-DTDPA]) was added.

[0052] As shown in Figure 3, the proportional limit strength was significantly improved when 3,3'-dithiodipropionic acid or gallium(III) oxide was added compared to when no additive was added. The proportional limit strength was greater when 3,3'-dithiodipropionic acid was added than when gallium(III) oxide was added.

[0053] When 3,3'-dithiodipropionic acid or gallium (III) oxide was added, the proportional limit strength was found to depend on the particle size of the additive. The smaller the particle size of the additive, the higher the proportional limit strength. The proportional limit strength improved by approximately 100% (approximately 2 times) when the particle size was 3 nm, and by approximately 18% when the particle size was 8 nm.

[0054] On the other hand, when silica or a copolymer of lactic acid and 3,3'-dithiodipropionic acid was added, the proportional limit strength increased by less than 5%, indicating that the effect of improving the proportional limit strength was small.

[0055] Figure 4 shows the analysis results of the relationship between the proportional limit strength of the composite material and the particle size of the additive. Figure 4 shows the results of measurements using polyamide 11 (PA11) as the base material and changing the type of additive. The concentration of the additive was 10 wt% in all cases.

[0056] The dotted line in the figure shows the result of adding yttria-stabilized hafnia (HfO3 + Y2O3) with an yttria concentration of 8 wt%. The solid line in the figure shows the result of adding yttria-stabilized hafnia (HfO3 + Y2O3) with an yttria concentration of 5 wt%. The two-dot-dashed line in the figure shows the result of adding silica (SiO2). The single-dot-dashed line in the figure shows the result when no additives were added.

[0057] As shown in Figure 4, the proportional limit strength was significantly improved when yttria-stabilized hafnia was added compared to when no additive was added. The proportional limit strength was greater when the yttria concentration was 8 wt% than when the yttria concentration was 5 wt%.

[0058] When yttria-stabilized hafnia was added, the proportional limit strength was found to depend on the particle size of the additive. The smaller the particle size of the additive, the higher the proportional limit strength. The proportional limit strength improved by approximately 50% (approximately 1.5 times) when the particle size was 3 nm, and by approximately 21% when the particle size was 8 nm.

[0059] On the other hand, when silica was added, the proportional limit strength increased by less than 5%, indicating that the effect of adding silica on improving the proportional limit strength was small. Furthermore, when the yttria concentration was less than 5 wt% or more than 10 wt%, the proportional limit strength increased by only about 7%. It can be said that the yttria concentration of yttria-stabilized hafnia should preferably be between 5 wt% and 10 wt%.

[0060] Figure 5 shows the analysis results of the relationship between the proportional limit strength of the composite material and the particle size of the additive. Figure 5 shows the results of measurements using polyamide 4 (PA4) as the base material and changing the type of additive. The concentration of the additive was 10 wt% in all cases.

[0061] The dotted line in the figure shows the results when sodium potassium oxide (Na2O + K2O) with a potassium oxide concentration of 3 wt% was added. The solid line in the figure shows the results when sodium potassium oxide (Na2O + K2O) with a potassium oxide concentration of 2 wt% was added. The two-dot chain line in the figure shows the results when silica (SiO2) was added. The single-dot chain line in the figure shows the results when no additives were added.

[0062] As shown in Figure 5, the proportional limit strength was significantly improved when sodium potassium oxide was added compared to when no additive was added. The proportional limit strength was greater when the potassium oxide concentration was 3 wt% than when the potassium oxide concentration was 2 wt%.

[0063] When sodium potassium oxide was added, the proportional limit strength depended on the particle size of the additive. The smaller the particle size of the additive, the higher the proportional limit strength. When the particle size was 3 nm, the proportional limit strength improved by approximately 150% (approximately 2.5 times), and when the particle size was 8 nm, it improved by approximately 40%.

[0064] On the other hand, when silica was added, the proportional limit strength increased by less than 5%, indicating that the effect of adding silica on improving the proportional limit strength was small. Furthermore, when the potassium oxide concentration was less than 2 wt% or more than 5 wt%, the proportional limit strength increased by only about 6%. Therefore, it can be said that the potassium oxide concentration in sodium potassium oxide should be between 2 wt% and 5 wt%.

[0065] Next, we will show the results of confirming the concentration dependence of the additive action in composite materials with biomass-derived resin as the base material.

[0066] Figure 6 shows the analysis results of the relationship between the proportional limit strength of composite materials and the concentration of additives. Figure 6 shows the results of measurements using polylactic acid (PLA) as the base material and 3,3'-dithiodipropionic acid (DTDPA) or gallium oxide (III) (Ga2O3) as the additive, with the additive concentration varied. The average particle size of the additives was 3 nm in all cases.

[0067] The dotted line in the figure shows the results when 3,3'-dithiodipropionic acid (DTDPA) was added, and the solid line shows the results when gallium(III) oxide (Ga2O3) was added.

[0068] As shown in Figure 6, when 3,3'-dithiodipropionic acid or gallium(III) oxide was added, the effect of improving the proportional limit strength was significant when the concentration of the additive relative to the base material was 3 wt% or more and 22 wt% or less. When the additive concentration was less than 3 wt% or more than 22 wt%, the proportional limit strength was significantly reduced.

[0069] Figure 7 shows the analysis results of the relationship between the proportional limit strength of a composite material and the concentration of additive. Figure 7 shows the results of measurements using polyamide 11 (PA11) as the base material and yttria-stabilized hafnia (HfO3 + Y2O3) as the additive, with the additive concentration varied. The average particle size of the additive is 3 nm in all cases.

[0070] The dotted line in the figure shows the results when yttria-stabilized hafnia (HfO3 + Y2O3) with an yttria concentration of 8 wt% was added, and the solid line in the figure shows the results when yttria-stabilized hafnia (HfO3 + Y2O3) with an yttria concentration of 5 wt% was added.

[0071] As shown in Figure 7, when yttria-stabilized hafnia was added, the effect of improving the proportional limit strength was significant when the concentration of the additive relative to the base material was 5 wt% or more and 38 wt% or less. When the additive concentration was less than 5 wt% or more than 38 wt%, the proportional limit strength was significantly reduced.

[0072] Figure 8 shows the analysis results of the relationship between the proportional limit strength of a composite material and the concentration of additive. Figure 8 shows the results of measurements using polyamide 4 (PA4) as the base material and sodium potassium oxide (Na2O + KO2O) as the additive, with the additive concentration varied. The average particle size of the additive was 3 nm in all cases.

[0073] The dotted line in the figure shows the results when sodium potassium oxide (Na2O + KO) with a potassium oxide concentration of 3 wt% was added, and the solid line in the figure shows the results when sodium potassium oxide (Na2O + KO) with a potassium oxide concentration of 2 wt% was added.

[0074] As shown in Figure 8, when sodium potassium oxide was added, the effect of improving the proportional limit strength was significant when the additive concentration relative to the base material was 3 wt% or more and 38 wt% or less. When the additive concentration was less than 3 wt% or more than 38 wt%, the proportional limit strength was significantly reduced.

[0075] 6, 7, and 8, when the concentration of the additive relative to the base material was lower than the lower limit, the effect of improving the proportional limit strength was not sufficiently achieved. Below the lower limit, there were too few starting points for the effect of aligning the molecular chains of the biomass-derived resin, and the effect did not reach areas away from the interface between the base material and the additive, which is thought to have resulted in the molecular chains of the biomass-derived resin becoming disordered and the proportional limit strength not being improved.

[0076] On the other hand, when the concentration of the additive relative to the base material was higher than the upper limit, the effect of improving the proportional limit strength was not sufficiently obtained. When the upper limit was exceeded, there were too many starting points for the effects of aligning the molecular chains of the biomass-derived resin, which interfered with each other, causing the molecular chains of the biomass-derived resin to become disordered, and the proportional limit strength was not improved.

[0077] In contrast, when the concentration of the additive in the base material is equal to or greater than the lower limit and equal to or less than the upper limit, the starting points of the action of aligning the molecular chains of the biomass-derived resin can be appropriately dispersed. The action from the starting points extends independently to areas away from the interface between the base material and the additive, allowing for appropriate action over a wide range of the base material. Therefore, compared to when the additive amount is inappropriate, a high effect of improving the proportional limit strength can be achieved.

[0078] Next, in order to confirm the mechanism of action of the additive on the base material, the atomic arrangement of the base material without the additive and the atomic arrangement of the base material with the additive are compared. The results are shown below.

[0079] The atomic arrangement was analyzed by molecular dynamics simulations combined with density functional theory (DFT), as described in Non-Patent Document 1 (R. Car, M. Parrinello (1985). Unified Approach for Molecular Dynamics and Density-Functional Theory. PHYSICAL REVIEW LETTERS. VOLUME 55, NUMBER 22, 2471-2474).

[0080] In molecular dynamics simulations that combine DFT, the structure of a target substance is expressed using electron density functionals, and the coordinates of each constituent atom at each time can be calculated using molecular orbitals and energy obtained from the equations of motion. It is also possible to select functionals, allowing for highly accurate reflection of intermolecular interactions based on electronic and energy states.

[0081] Figure 9 shows the results of an analysis of the atomic arrangement of a base material to which no additives have been added. Figure 9 shows the results when polylactic acid (PLA) was used as the base material. The black atoms are carbon atoms, the gray atoms are oxygen atoms, and the white atoms are hydrogen atoms.

[0082] Figure 10 shows the results of an analysis of the atomic arrangement of a base material to which no additives have been added. Figure 10 shows the results when polyamide 11 (PA11) was used as the base material. The small gray atoms are carbon atoms, the small black atoms are nitrogen atoms, and the large black atoms are oxygen atoms. Hydrogen atoms are not shown in the figure.

[0083] Figure 11 shows the results of an analysis of the atomic arrangement of a base material to which no additives have been added. Figure 11 shows the results when polyamide 4 (PA4) was used as the base material. The small gray atoms are carbon atoms, the black atoms are nitrogen atoms, the large white atoms are oxygen atoms, and the small black atoms are hydrogen atoms.

[0084] As shown in Figures 9, 10, and 11, a base material that does not contain an additive that acts to align molecular chains has poor regularity even in a crystallized state, and the orientation, conformation, and spacing of molecular chains are all highly variable. This results in weak intermolecular adhesion strength, making it difficult to achieve the proportional limit strength required for general structural components.

[0085] Figure 12 shows the results of an analysis of the atomic arrangement of a base material with an additive added. Figure 12 shows the results when polylactic acid (PLA) was used as the base material and 3,3'-dithiodipropionic acid (DTDPA) was used as the additive. The left image in Figure 12 is a side view of the interface between the base material and the additive, and the right image is a top view of the interface between the base material and the additive. The bottom image shows the molecular structure of 3,3'-dithiodipropionic acid (DTDPA).

[0086] As shown in Figure 12, polylactic acid has a carbonyl group as its characteristic functional group. The carbonyl group is the functional group with the highest polarization in the molecular chain of polylactic acid. Polylactic acid can adopt a conformation in which the nearest carbonyl groups are positioned trans-side, extending like a straight chain. The distance between the carbon atoms constituting the second nearest carbonyl groups in polylactic acid is approximately 0.717 nm.

[0087] On the other hand, 3,3'-dithiodipropionic acid has an oxygen atom of a carbonyl group as a characteristic atom that can form an interaction with the carbonyl group of polylactic acid. The distance between the oxygen atoms that make up the carbonyl group of 3,3'-dithiodipropionic acid is approximately 0.717 nm.

[0088] With this combination, the relative difference between the spacing of the characteristic functional groups arranged on the molecular chain of the base material and the spacing of the characteristic atoms arranged on the structure of the additive becomes small. The characteristic functional groups are periodically arranged at the interface between polylactic acid and 3,3'-dithiodipropionic acid, forming a lattice-matched interface. It can be seen that the carbon atoms that make up the carbonyl groups of polylactic acid and the oxygen atoms that make up the carbonyl groups of 3,3'-dithiodipropionic acid are stabilized in close proximity to each other.

[0089] Furthermore, the molecular chains of polylactic acid also form a more regular atomic arrangement than when no additives are added. It can be seen that when 3,3'-dithiodipropionic acid is added to polylactic acid, the molecular chain orientation, molecular chain conformation, and spacing between molecular chains become more regularly aligned.

[0090] On the other hand, when a copolymer of lactic acid and 3,3'-dithiodipropionic acid is used as an additive, the effect of improving the proportional limit strength is small, as shown in Figure 3. In the case of a copolymer of lactic acid and 3,3'-dithiodipropionic acid, the ester bonds between the lactic acid and 3,3'-dithiodipropionic acid protrude outward and come into contact with the molecular chains that make up the base material, weakening the effect of aligning the molecular chains of polylactic acid.

[0091] Figure 13 shows the results of an analysis of the atomic arrangement of a base material with an additive added. Figure 13 shows the results when polylactic acid (PLA) was used as the base material and gallium oxide (III) (Ga2O3) was used as the additive. The left image in Figure 13 is a side view of the interface between the base material and the additive, and the right image is a top view of the interface between the base material and the additive.

[0092] As shown in Figure 13, polylactic acid has a carbonyl group as its characteristic functional group. The carbonyl group is the functional group with the highest polarization in the molecular chain of polylactic acid. Polylactic acid can adopt a conformation in which the nearest carbonyl groups are positioned trans-side, extending like a straight chain. The distance between the carbon atoms constituting the second nearest carbonyl groups in polylactic acid is approximately 0.717 nm.

[0093] On the other hand, gallium(III) oxide has a gallium atom as a characteristic atom that can interact with the carbonyl group of polylactic acid. The distance between the third nearest neighbor gallium atoms in the same crystal plane of the β-gallium(III) oxide crystal lattice is approximately 0.717 nm.

[0094] With this combination, the relative difference between the spacing of the characteristic functional groups arranged on the molecular chain of the base material and the spacing of the characteristic atoms arranged on the structure of the additive becomes small. The characteristic functional groups are periodically arranged at the interface between polylactic acid and gallium (III) oxide, forming a lattice-matched interface. It can be seen that the oxygen atoms that make up the carbonyl groups of polylactic acid and the gallium atoms of gallium (III) oxide are stabilized in close proximity to each other.

[0095] Furthermore, the molecular chains of polylactic acid also form a more regular atomic arrangement than when no additives are added. It can be seen that when gallium (III) oxide is added to polylactic acid, the molecular chain orientation, molecular chain conformation, and spacing between molecular chains become more regularly aligned.

[0096] On the other hand, as shown in Figure 3, when silica is used as an additive, the effect of improving the proportional limit strength is small. In the case of silica, the spacing between the nearest silicon atoms is approximately 0.306 nm, and the spacing between the second nearest silicon atoms is approximately 0.612 nm. The relative difference between the spacing between the carbon atoms constituting the second nearest carbonyl groups of polylactic acid (approximately 0.717 nm) and the spacing between the second nearest silicon atoms of silica (approximately 0.612 nm) is approximately 17%. Because this relative difference is large, the effect of aligning the molecular chains of polylactic acid is weakened.

[0097] Figure 14 shows the results of an analysis of the atomic arrangement of a base material with an additive added. Figure 14 shows the results when polyamide 11 (PA11) was used as the base material and yttria-stabilized hafnia (HfO3 + Y2O3) with an yttria concentration of 8 wt% was used as the additive. The left image in Figure 14 is a side view of the interface between the base material and the additive, and the right image is a bottom view of the interface between the base material and the additive.

[0098] As shown in Figure 14, polyamide 11 has a carbonyl group with an amide bond as its characteristic functional group. The carbonyl group is the functional group with the highest polarization in the molecular chain of polyamide 11. Polyamide 11 can adopt a conformation that extends in a linear chain. The distance between the oxygen atoms that make up the nearest carbonyl groups in polyamide 11 is approximately 1.456 nm.

[0099] On the other hand, yttria-stabilized hafnia has hafnium and yttrium atoms as characteristic atoms that can interact with the carbonyl groups of polyamide 11. The hafnium and yttrium atoms form six-membered rings via oxygen atoms in the crystal lattice. The spacing between four six-membered rings in the crystal lattice of cubic yttria-stabilized hafnia is approximately 1.456 nm.

[0100] With this combination, the relative difference between the spacing of the characteristic functional groups arranged on the molecular chain of the base material and the spacing of the characteristic atoms arranged on the structure of the additive becomes small. The characteristic functional groups are periodically arranged at the interface between polyamide 11 and yttria-stabilized hafnia, forming a lattice-matched interface. It can be seen that the oxygen atoms that make up the carbonyl groups of polyamide 11 and the hafnium and yttrium atoms of yttria-stabilized hafnia are stabilized in close proximity to each other.

[0101] Furthermore, the molecular chains of polyamide 11 form a more regular atomic arrangement than when no additive is added. It can be seen that when yttria-stabilized hafnia is added to polyamide 11, the molecular chain orientation, molecular chain conformation, and spacing between molecular chains of polyamide 11 become more regularly aligned.

[0102] On the other hand, as shown in Figure 4, when silica is used as an additive, the effect of improving the proportional limit strength is small. In the case of silica, the spacing between five six-membered rings in the crystal lattice is approximately 1.530 nm. The relative difference between the spacing between the oxygen atoms constituting the nearest carbonyl groups in polyamide 11, approximately 1.456 nm, and the spacing between five six-membered rings in the silica crystal lattice, approximately 1.530 nm, is approximately 5%. Because this relative difference is large, the effect of aligning the molecular chains of polyamide 11 is weak.

[0103] Furthermore, when the yttria concentration in yttria-stabilized hafnia is less than 5 wt% or more than 10 wt%, the spacing of four six-membered rings in the crystal lattice is significantly different from approximately 1.456 nm. In such cases, the interface between polyamide 11 and yttria-stabilized hafnia is not lattice-matched, and the effect of aligning the molecular chains of polyamide 11 is weakened.

[0104] Figure 15 shows the results of an analysis of the atomic arrangement of a base material with an additive added. Figure 15 shows the results when polyamide 4 (PA4) was used as the base material and sodium potassium oxide (Na2O+K2O) with a potassium oxide concentration of 3 wt% was used as the additive. The left image in Figure 15 is a side view of the interface between the base material and the additive, and the right image is a top view of the interface between the base material and the additive.

[0105] As shown in Figure 15, polyamide 4 has a carbonyl group with an amide bond as its characteristic functional group. The carbonyl group is the functional group with the highest polarization in the molecular chain of polyamide 4. Polyamide 4 can adopt a conformation that extends in a linear chain. The distance between the oxygen atoms that make up the nearest carbonyl groups in polyamide 4 is approximately 0.581 nm.

[0106] On the other hand, sodium potassium oxide has sodium and potassium atoms as characteristic atoms that can interact with the carbonyl groups of polyamide 4. The sodium and potassium atoms form four-membered rings via oxygen atoms in the crystal lattice. The spacing of one four-membered ring in the crystal lattice of cubic sodium potassium oxide is approximately 0.581 nm.

[0107] With this combination, the relative difference between the spacing of the characteristic functional groups arranged on the molecular chain of the base material and the spacing of the characteristic atoms arranged on the structure of the additive becomes small. The characteristic functional groups are periodically arranged at the interface between polyamide 4 and sodium potassium oxide, forming a lattice-matched interface. It can be seen that the oxygen atoms that make up the carbonyl groups of polyamide 4 and the sodium and potassium atoms of sodium potassium oxide are stabilized in close proximity to each other.

[0108] Furthermore, the molecular chains of polyamide 4 also form a more regular atomic arrangement than when no additives are added. It can be seen that when sodium potassium oxide is added to polyamide 4, the molecular chain orientation, molecular chain conformation, and spacing between molecular chains of polyamide 4 become more regularly aligned.

[0109] On the other hand, as shown in Figure 5, when silica is used as an additive, the effect of improving the proportional limit strength is small. In the case of silica, the distance between two six-membered rings in the crystal lattice is approximately 0.612 nm. The relative difference between the distance between the oxygen atoms constituting the nearest carbonyl groups in polyamide 4 (approximately 0.581 nm) and the distance between two six-membered rings in the silica crystal lattice (approximately 0.612 nm) is approximately 5%. Because this relative difference is large, the effect of aligning the molecular chains of polyamide 11 is weakened.

[0110] Furthermore, when the potassium oxide concentration is less than 2 wt% or more than 5 wt%, the spacing of one four-membered ring in the crystal lattice differs significantly from approximately 0.581 nm. In such cases, the interface between polyamide 4 and sodium potassium oxide is not lattice-matched, and the effect of aligning the molecular chains of polyamide 4 is weakened.

[0111] Figure 16 shows the results of an analysis of the atomic arrangement of a base material with an additive added. Figure 16 shows the results when polyamide 11 (PA11) was used as the base material and silica (SiO2) was used as the additive. The left image in Figure 16 is a side view of the interface between the base material and the additive, and the right image is a bottom view of the interface between the base material and the additive.

[0112] As shown in Figure 16, when silica is used as an additive, the relative difference between the spacing between nearest carbonyl groups in polyamide 11 and the spacing between six-membered rings in the silica crystal lattice is large, so the effect of aligning the molecular chains of polyamide 11 is weakened. Compared to when yttria-stabilized hafnia is added (see Figure 14), the spacing between molecular chains of polyamide 11 when silica is added becomes uneven, with a mixture of wide and narrow areas. Even in regions away from the interface between the base material and the additive, the atomic arrangement of the base material is disrupted, reducing the effect of improving the proportional limit strength.

[0113] As described above, when an additive that acts to align molecular chains is added, if the relative difference between the spacing of the characteristic functional groups arranged on the molecular chains of the base material (a biomass-derived resin) and the spacing of the characteristic atoms arranged on the structure of the additive is 3% or less, the effect of aligning the molecular chains can be obtained over a wide range, significantly improving the proportional limit strength of the composite material. On the other hand, if the relative difference exceeds 3%, the effect of aligning the molecular chains weakens, and the effect of improving the proportional limit strength becomes smaller.

[0114] Next, another embodiment of the composite material using a biomass-derived resin as a matrix will be described.

[0115] In the composite material 10 according to this embodiment, a recycled material obtained by recycling used biomass-derived resin can also be used as the biomass-derived resin that constitutes the base material 1. As an additive, an additive that acts to align the molecular chains of the biomass-derived resin at the atomic level is blended into the recycled material.

[0116] After being used for various purposes, biomass-derived resin can be regenerated through chemical recycling. The used resin is collected and subjected to processes such as removing impurities, crushing the resin, and washing the resin. If necessary, the resin is dissolved and the resin components are separated by gravity, after which the resin flakes and separated monomers are reused as raw materials for the recycled material that forms the base material 1.

[0117] When a recycled material is used as the biomass-derived resin constituting the base material 1, the preferred combination of the base material 1 and the additive 2 and the preferred concentration of the additive 2 are the same as those described above in (1) to (3). The base material 1 can be a recycled polylactic acid obtained by recycling used polylactic acid, a recycled polyamide 11 obtained by recycling used polyamide 11, or a recycled polyamide 4 obtained by recycling used polyamide 4.

[0118] In general, when biomass-derived resins are exposed to ultraviolet light, heat, moisture, alkali, etc., the polymer molecular chains decompose. Biomass-derived resins used for general purposes lose 10 to 50% of their molecular weight due to ultraviolet degradation, thermal degradation, hydrolysis, alkaline washing during recycling, etc. When such resins are regenerated and reused after use, the proportional limit strength also decreases by 10 to 50%.

[0119] In contrast, adding an additive that aligns the molecular chains of biomass-derived resin to recycled materials can improve the proportional limit strength by approximately 15 to 150%. The additive's effect extends to areas away from the interface between the base material and the additive, so it is effective in aligning short molecular chains when using recycled materials with reduced molecular weight. When adding an additive, it is possible to repolymerize the recovered biomass-derived resin, or it is possible not to repolymerize the biomass-derived resin.

[0120] Next, a method for producing a composite material using a biomass-derived resin as a base material and applications of the composite material will be described.

[0121] A composite material using a biomass-derived resin as a base material can be produced by mixing the biomass-derived resin with an additive, melting and kneading the resulting mixture, and molding the resulting resin composition into a desired shape. The additive used should at least have the effect of aligning the molecular chains of the biomass-derived resin at the atomic level.

[0122] The biomass-derived resin can be prepared in an appropriate raw material form such as pellets, powder, granules, liquid, fluid, etc. As the biomass-derived resin, a newly synthesized synthetic product may be used, or a recycled material obtained by recycling used biomass-derived resin may be used.

[0123] The additives may be mixed with the biomass-derived resin either as a single substance or as a masterbatch. The masterbatch can be prepared as pellets containing a high concentration of additives by adding the additives to the biomass-derived resin in advance. The use of a masterbatch makes it easy to handle the additives and adjust the amount of additive added.

[0124] The resin composition can be kneaded using various devices such as a batch-type internal kneader such as a Banbury mixer or a pressure kneader, an open kneader such as a roll kneader or a rotor kneader, a single screw extruder, a twin screw extruder, etc. The resin composition can be granulated using various devices such as an extrusion granulator, a disk die granulator, a roller granulator, etc.

[0125] Composite materials using biomass-derived resin as a base material can be molded into any shape depending on the intended use of the composite material. As a molding method for the composite material, appropriate methods such as extrusion molding, injection molding, blow molding, compression molding, and additive manufacturing can be used.

[0126] As a method of additive manufacturing, it is possible to use fused deposition modeling (FDM) which uses filament-like resin, laser powder deposition modeling which uses powdered resin and melts it with a laser, etc. As a raw material for laser powder deposition modeling, it is possible to use a powder of biomass-derived resin which has additives pre-blended, or a combination of a powder of biomass-derived resin and a powder of additive.

[0127] Composite materials using biomass-derived resins as a base material can be used in various applications, including structural components for electrical equipment such as vacuum cleaners, washing machines, air conditioners, rice cookers, televisions, personal computers, telephones, copy machines, fax machines, and shredders, as well as plastic tableware, containers, bags, clothing, bedding, furniture, stationery, toys, automotive interior materials and parts, packaging films, film substrates, and artificial turf.

[0128] The composite material using biomass-derived resin as a base material is preferably used in applications requiring high mechanical strength, particularly proportionality limit, and more preferably as a structural component for various products. The structural component is formed from a composite material using biomass-derived resin as a base material and containing additives. Examples of the structural component include exterior materials, reinforcing materials, and skeletal materials for products.

[0129] A particularly preferred application of composite materials using biomass-derived resin as a matrix is ​​a structural component having a bent portion molded or bent into a bent shape. The bent portion may be a shape formed from a plate, wire, rod, or the like, and may have a curved or curved shape. The bent portion is a location where stress tends to concentrate. By using a composite material in such a bent portion, a high proportional limit strength can be obtained, thereby suppressing the occurrence of permanent deformation at the atomic level.

[0130] Next, a method for recycling a composite material using a biomass-derived resin as a base material will be described with reference to the drawings.

[0131] FIG. 17 is a diagram showing a method for recycling a composite material according to an embodiment of the present invention. As shown in FIG. 17, when 3,3′-dithiodipropionic acid (DTDPA) is used as an additive that acts to align molecular chains of biomass-derived resin, the composite material 10 according to this embodiment can be recycled by a method including a step of immersing the composite material in a reducing solution 4 to decompose the additive.

[0132] In FIG. 17, a reducing solution 4 is prepared in a processing container 5. A solution containing a strong reducing agent can be used as the reducing solution 4. Examples of strong reducing agents that can be used include reduced glutathione (GSH), dithiothreitol, and 2-mercaptoethanol. A solvent for the reducing solution 4 can be a Tris buffer solution or the like. The pH of the reducing solution 4 is preferably 7 or higher, more preferably 8 or higher, and even more preferably 8.5 or higher.

[0133] The method for recycling a composite material according to this embodiment includes a step of recovering the composite material after use, a step of removing impurities present in the composite material, a step of crushing the composite material, a step of washing the composite material, a step of dissolving the composite material, etc. After the step of dissolving the composite material, a step of gravity separation of the components contained in the composite material can be carried out as necessary.

[0134] In the composite material recycling method according to this embodiment, in the step of dissolving the composite material, a used composite material 10 is immersed in a reducing solution 4 to decompose the additives. As shown in Fig. 17, the composite material 10 is immersed in the reducing solution 4 to decompose the DTDPA. In the step of dissolving the composite material, in addition to decomposing the DTDPA, the biomass-derived resin that constitutes the matrix 1 can also be decomposed.

[0135] According to this recycling method, the composite material 10 is immersed in the reducing solution 4, and the additive 2, DTDPA, is decomposed by reduction of the disulfide bond. This makes it easy to separate the DTDPA added to the matrix 1 when recycling the composite material 10. This makes it possible to efficiently recover a high-purity biomass-derived resin, allowing the used biomass-derived resin to be used as a useful recycled material.

[0136] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and includes various modifications without departing from the technical scope. For example, the above-described embodiments are not necessarily limited to those including all of the configurations described above. Furthermore, it is possible to replace part of the configuration of an embodiment with another configuration, or to add another configuration to the configuration of an embodiment. Furthermore, it is also possible to add other configurations to, delete configurations from, or replace configurations with respect to part of the configuration of an embodiment. [Explanation of symbols]

[0137] 10 Composite materials 1. Base material (biomass-derived resin) 2. Additives 3 Interface 4. Reducing Solution 5 Processing container

Claims

1. A composite material containing a biomass-derived resin as a base material and an additive, a relative difference between the spacing of the functional groups arranged on the molecular chain of the base material and the spacing of atoms that interact with the functional groups arranged on the structure of the additive is 3% or less; the base material is polylactic acid; the additive comprises at least one selected from 3,3'-dithiodipropionic acid and gallium (III) oxide; A composite material in which the concentration of the additive relative to the base material is 3 wt % or more and 22 wt % or less.

2. 2. The composite material of claim 1, The polylactic acid is a composite material made from recycled polylactic acid that has been recycled from used polylactic acid.

3. A composite material containing a biomass-derived resin as a base material and an additive, a relative difference between the spacing of the functional groups arranged on the molecular chain of the base material and the spacing of atoms that interact with the functional groups arranged on the structure of the additive is 3% or less; the matrix is ​​polyamide 11; the additive includes yttria-stabilized hafnia having an yttria concentration of 5 wt % or more and 10 wt % or less; A composite material in which the concentration of the additive relative to the base material is 5 wt % or more and 38 wt % or less.

4. 4. The composite material of claim 3, The polyamide 11 is a composite material made from recycled polyamide 11 recycled from used polyamide 11.

5. A composite material containing a biomass-derived resin as a base material and an additive, a relative difference between the spacing of the functional groups arranged on the molecular chain of the base material and the spacing of atoms that interact with the functional groups arranged on the structure of the additive is 3% or less; the matrix is ​​polyamide 4; The additive contains sodium potassium oxide having a potassium oxide concentration of 2 wt % or more and 5 wt % or less, A composite material in which the concentration of the additive relative to the base material is 3 wt % or more and 38 wt % or less.

6. 6. The composite material of claim 5, The polyamide 4 is a composite material made from recycled polyamide 4 recycled from used polyamide 4.

7. A structural member formed of a composite material containing an additive and a biomass-derived resin as a base material, a relative difference between the spacing of the functional groups arranged on the molecular chain of the base material and the spacing of atoms that interact with the functional groups arranged on the structure of the additive is 3% or less; the base material is polylactic acid; the additive comprises at least one selected from 3,3'-dithiodipropionic acid and gallium (III) oxide; The concentration of the additive relative to the base material is 3 wt % or more and 22 wt % or less, The structural member has a bent portion that has been formed or bent into a bent shape.

8. A structural member formed of a composite material containing an additive and a biomass-derived resin as a base material, a relative difference between the spacing of the functional groups arranged on the molecular chain of the base material and the spacing of atoms that interact with the functional groups arranged on the structure of the additive is 3% or less; the matrix is ​​polyamide 11; the additive includes yttria-stabilized hafnia having an yttria concentration of 5 wt % or more and 10 wt % or less; The concentration of the additive relative to the base material is 5 wt % or more and 38 wt % or less, The structural member has a bent portion that has been formed or bent into a bent shape.

9. A structural member formed of a composite material containing an additive and a biomass-derived resin as a base material, a relative difference between the spacing of the functional groups arranged on the molecular chain of the base material and the spacing of atoms that interact with the functional groups arranged on the structure of the additive is 3% or less; the matrix is ​​polyamide 4; The additive contains sodium potassium oxide having a potassium oxide concentration of 2 wt % or more and 5 wt % or less, The concentration of the additive relative to the base material is 3 wt % or more and 38 wt % or less, The structural member has a bent portion that has been formed or bent into a bent shape.

10. A method for recycling a composite material containing a biomass-derived resin as a base material and an additive, comprising: The base material is recycled polylactic acid obtained by regenerating used polylactic acid, the additive comprises 3,3'-dithiodipropionic acid; The concentration of the additive relative to the base material is 3 wt % or more and 22 wt % or less, A method for recycling a composite material, comprising the step of immersing the used composite material in a solution containing a reducing agent to decompose the additive.

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