Biomass epoxy resin composition

Abstract

Provided is a biomass epoxy resin composition comprising an epoxy resin, a biomass-derived curing agent, a biomass-derived monomer, and a polymerization initiator, in which the gelation time of a polymer of the monomer at 100°C or lower is 20 minutes or less, and the glass transition temperature of the polymer of the monomer is 60°C or higher.

Description

Biomass epoxy resin composition

[0001] The present disclosure relates to biomass epoxy resin compositions.

[0002] Epoxy resins are widely used as insulating materials for electrical equipment due to their excellent thermomechanical properties, electrical properties, moisture resistance, chemical resistance, dimensional stability, etc. Epoxy resins are a type of thermosetting resin that, once cured, undergoes a three-dimensional network-like reaction to form a strong cured product that is insoluble and infusible, making it difficult to reuse after curing. For this reason, most used epoxy resins are disposed of by incineration, landfilling, etc. However, incineration of epoxy resins releases CO, a greenhouse gas. ２ occurs.

[0003] In recent years, from the perspective of preventing global warming, CO ２ Reducing carbon dioxide emissions is an issue. There is also a need to reduce the amount of petroleum resources used, creating a need for materials with low environmental impact. Against this background, it has been proposed to use biomass materials with carbon-neutral properties as raw materials for epoxy resins.

[0004] Japanese Patent Laid-Open Publication No. 2009-263549 (Patent Document 1) and Japanese Patent Laid-Open Publication No. 2013-181040 (Patent Document 2) disclose epoxy resin compositions comprising an epoxy resin and a biomass-derived curing agent that is solid at room temperature. Patent Document 1 proposes a method of using lignin having a phenol skeleton in the molecule as a curing agent, and discloses that an epoxy resin cured product having a high glass transition temperature (Tg) of 200°C or higher has been obtained. Furthermore, Patent Document 2 proposes a method of using a derivative of relatively low-molecular-weight plant-derived polyphenols as a curing agent from the viewpoint of moldability.

[0005] Furthermore, JP 2016-520677 A (Patent Document 3) discloses a multi-component synthetic resin adhesive containing at least one of a reactive diluent and a reactive resin (including an epoxy resin). Patent Document 3 lists the challenges of increasing the proportion of bio-derived materials in the synthetic resin adhesive and improving product characteristics related to environmental friendliness and sustainability, and proposes a method of solving these challenges by using a bio-derived reactive diluent and reactive resin.

[0006] JP 2009-263549 A JP 2013-181040 A JP 2016-520677 A

[0007] However, both Patent Documents 1 and 2 use a curing agent that is solid at room temperature, which has the problem of inferior workability compared to resin compositions using a liquid curing agent. In particular, when lignin with a high molecular weight is used as the curing agent, as disclosed in Patent Document 1, the viscosity of the resin composition increases and workability decreases. Furthermore, as disclosed in Patent Document 2, when pyrogallol, a derivative of polyphenols, is used as the curing agent, improved workability is expected compared to lignin, but there is room for improvement in heat resistance.

[0008] Furthermore, Patent Document 3 uses a biomass-derived reactive diluent as a constituent component, but does not consider workability or heat resistance. Heat resistance in particular is known to be affected by the structure of the cured product made of a multi-component synthetic resin, and control of the structure of the cured product is important.

[0009] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a biomass epoxy resin composition that is environmentally friendly and has both workability and heat resistance.

[0010] As a result of extensive research aimed at solving the above problems, the present inventors have found that by combining an epoxy resin, a biomass-derived curing agent, a biomass-derived monomer, and a polymerization initiator, it is possible to obtain the effects of achieving excellent environmental friendliness, workability, and heat resistance.The present disclosure relates to the following biomass-derived epoxy resin composition.

[0011] A biomass epoxy resin composition comprising an epoxy resin, a biomass-derived curing agent, a biomass-derived monomer, and a polymerization initiator, wherein the gelation time of a polymer of the monomer at 100°C or less is 20 minutes or less, and the glass transition temperature of the polymer of the monomer is 60°C or higher.

[0012] According to the present disclosure, it is possible to provide a biomass epoxy resin composition that is environmentally friendly and has both workability and heat resistance.

[0013] Hereinafter, embodiments of the present disclosure will be described.

[0014] Embodiment 1 <Biomass Epoxy Resin Composition> The biomass epoxy resin composition of this embodiment contains an epoxy resin (A), a biomass-derived curing agent (B), a biomass-derived monomer (C), and a polymerization initiator (D). The gelation time of the polymer of the biomass-derived monomer (C) at 100°C or less is 20 minutes or less. The Tg of the polymer of the biomass-derived monomer (C) is 60°C or higher. Hereinafter, the polymer of the biomass-derived monomer (C) will also be simply referred to as the "polymer."

[0015] (Epoxy Resin (A)) The epoxy resin (A) contained in the biomass epoxy resin composition of the present embodiment is a compound having two or more oxirane rings (epoxy groups) per molecule. There are no particular restrictions on the form of the epoxy resin (A), but from the viewpoint of dissolving the solid biomass-derived curing agent (B), it is preferable that the epoxy resin (A) be liquid at room temperature.

[0016] Examples of such epoxy resins (A) include bisphenol A epoxy resins, bisphenol F epoxy resins, cresol novolac epoxy resins, alicyclic epoxy resins, and glycidyl amine epoxy resins. Among these epoxy resins (A), bisphenol A epoxy resins and bisphenol F epoxy resins are preferred from the viewpoints of workability and heat resistance. Furthermore, when high heat resistance is required, polyfunctional epoxy resins are preferred.

[0017] The epoxy resin (A) may be derived from petroleum or biomass. The epoxy resin (A) may be used alone or in combination of two or more. When two or more types are used in combination, the combination is not particularly limited.

[0018] (Biomass-derived curing agent (B)) The biomass-derived epoxy resin composition of the present embodiment contains a biomass-derived curing agent (B). By including the biomass-derived curing agent (B), it is possible to obtain an environmentally friendly biomass-derived epoxy resin composition.

[0019] From the viewpoint of heat resistance, the biomass-derived curing agent (B) is preferably a compound having an aromatic ring. Examples of such biomass-derived curing agents (B) include aromatic compounds such as 4-aminobenzoic acid, 4-hydroxybenzoic acid, and protocatechuic acid, and industrial lignin obtained by isolating lignin, a phenolic polymer compound, by various methods. Among these biomass-derived curing agents (B), 4-aminobenzoic acid, 4-hydroxybenzoic acid, and protocatechuic acid are preferred. 4-aminobenzoic acid, 4-hydroxybenzoic acid, and protocatechuic acid have low molecular weights, and by using a low-molecular-weight biomass-derived curing agent (B), the mixing viscosity of the biomass epoxy resin composition can be kept low, allowing for the production of a biomass epoxy resin composition with excellent workability.

[0020] The biomass-derived curing agent (B) may be used alone or in combination of two or more thereof. The biomass-derived curing agent (B) may be entirely or partially derived from biomass.

[0021] The content of the biomass-derived curing agent (B) should be such that, when the epoxy groups in the molecules of the epoxy resin (A) react with the active hydrogen of the amino groups, hydroxyl groups, carboxyl groups, acid anhydrides, and other functional groups reactive with epoxy groups in the molecules of the biomass-derived curing agent (B) at a chemical equivalent ratio of 1:1, the equivalent ratio of the epoxy groups in the molecules of the epoxy resin (A) to the functional groups in the molecules of the biomass-derived curing agent (B) is 0.3 to 3.0. If the ratio is outside the above range, there is a risk that properties such as heat resistance will not be fully exhibited.

[0022] Furthermore, the content of the biomass-derived curing agent (B) is preferably such that the number of active hydrogen atoms of the epoxy groups in the epoxy resin (A) is equivalent to that of the functional groups in the biomass-derived curing agent (B). For example, when a bisphenol A epoxy resin having an epoxy equivalent of 190 g / eq is used as the epoxy resin (A) and 4-aminobenzoic acid is used as the biomass-derived curing agent (B), the amount of 4-aminobenzoic acid is 24.0 parts by weight per 100 parts by weight of the bisphenol A epoxy resin. For example, when a similar bisphenol A epoxy resin is used as the epoxy resin (A) and 4-hydroxybenzoic acid is used as the biomass-derived curing agent (B), the amount of 4-hydroxybenzoic acid is 36.4 parts by weight per 100 parts by weight of the bisphenol A epoxy resin.

[0023] (Biomass-derived monomer (C)) The biomass epoxy resin composition of the present embodiment contains a biomass-derived monomer (C). By including the biomass-derived monomer (C), it is possible to obtain a biomass epoxy resin composition that is excellent in environmental friendliness and workability.

[0024] Examples of the biomass-derived monomer (C) include ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, tetrabutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, glycidyl (meth)acrylate, and neopentyl glycol dimethacrylate. The biomass-derived monomer (C) may be used alone or in combination of two or more. The biomass-derived monomer (C) may be completely or partially derived from biomass. In addition, as long as the monomer (C) derived from biomass is contained, it may also contain a petroleum-derived monomer.

[0025] Among these biomass-derived monomers (C), ethyl methacrylate, tetrabutyl methacrylate, cyclohexyl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl (meth)acrylate, etc. are preferred, with isobornyl (meth)acrylate being more preferred. This is because isobornyl (meth)acrylate has a high Tg (Tg: 180°C), and compatibility between isobornyl (meth)acrylate and epoxy resin (A) allows the production of a biomass epoxy resin composition with excellent heat resistance. Therefore, biomass epoxy resin compositions using isobornyl (meth)acrylate can be suitably used in applications requiring high heat resistance.

[0026] As will be described later, when the biomass epoxy resin composition of this embodiment is cured, the polymer has a Tg of 60° C. or higher. The above-mentioned biomass-derived monomer (C) includes those having a Tg of less than 60° C. However, by combining two or more types of biomass-derived monomer (C) having a Tg of 60° C. or higher and biomass-derived monomer (C) having a Tg of less than 60° C., the Tg of the polymer may be adjusted to 60° C. or higher.

[0027] The content of the biomass-derived monomer (C) is 10 to 70% by weight based on the epoxy resin (A), biomass-derived curing agent (B), and biomass-derived monomer (C). If the content of the biomass-derived monomer (C) is less than 10% by weight, the effect of the biomass-derived monomer (C) may be reduced. If the content of the biomass-derived monomer (C) exceeds 70% by weight, the biomass-derived epoxy resin composition may become brittle, resulting in impaired moldability.

[0028] (Polymerization initiator (D)) The biomass epoxy resin composition of this embodiment contains a polymerization initiator (D). The polymerization initiator (D) is a compound that can initiate the polymerization of the biomass-derived monomer (C), and examples of the polymerization initiator include a radical initiator that generates active radicals, acids, etc. under the action of light or heat, and a redox initiator that generates radicals by utilizing an oxidation-reduction reaction.

[0029] Examples of the polymerization initiator (D) include organic peroxides such as hydroperoxides, dialkyl peroxides, peroxyesters, diacyl peroxides, peroxycarbonates, peroxyketals, and ketone peroxides, as well as combinations of these organic peroxides with reducing agents such as metal salts and amines. Among these polymerization initiators (D), combinations of hydroperoxides and metal salts, and combinations of ketone peroxides and metal salts, which can efficiently generate radicals even at low temperatures, are preferred. Examples of hydroperoxides include tert-butyl hydroperoxide and cumene hydroperoxide. Examples of ketone peroxides include methyl ethyl ketone peroxide and cyclohexanone peroxide. Examples of metal salts include cobalt salts such as cobalt naphthenate and cobalt octoate, and vanadium compounds such as vanadium pentoxide.

[0030] The content of the polymerization initiator (D) varies depending on the type of the biomass-derived monomer (C) used, but is 0.001 to 20 parts by weight, and preferably 0.005 to 10 parts by weight, per 100 parts by weight of the biomass-derived monomer (C). By setting the content of the polymerization initiator (D) within the above range, the gelation time of the polymer, which will be described later, can be adjusted to an appropriate range.

[0031] (Curing Accelerator) The biomass epoxy resin composition of the present embodiment may contain a curing accelerator to increase the curing rate of the epoxy resin (A). The curing accelerator is not particularly limited as long as it accelerates the curing of the epoxy resin (A). Examples include tertiary amine accelerators such as benzyldimethylamine, imidazole accelerators such as 2-ethyl-4-methylimidazole, phosphorus accelerators such as triphenylphosphine, and organometallic accelerators such as zinc octylate. The curing accelerators may be used alone or in combination of two or more. The content of the curing accelerator may be adjusted appropriately depending on the type of epoxy resin (A) and biomass-derived curing agent (B) used, and is generally 0.1 to 100 parts by weight per 100 parts by weight of the epoxy resin (A).

[0032] (Properties of Biomass Epoxy Resin Composition) [Gelation Time] When the biomass epoxy resin composition of this embodiment is cured, the gelation time of the polymer at 100°C or below is 20 minutes or less. If the gelation time of the polymer at 100°C or below exceeds 20 minutes, the volatilization of the biomass-derived monomer (C) progresses, and the reaction between the epoxy resin (A) and the biomass-derived curing agent (B) progresses, resulting in an increase in viscosity, which suppresses the degree of polymerization of the biomass-derived monomer (C), making it difficult to obtain the effects of adding the biomass-derived monomer (C). The gelation time of the polymer at 100°C or below is preferably 18 minutes or less. While a faster gelation time is preferable, a gelation time of 30 seconds or more is preferred from the viewpoint of the moldability of the biomass epoxy resin composition.

[0033] The gelation time can be measured, for example, by the following procedure. A gelation tester (No. 153 Gel Time Tester, manufactured by Yasuda Seiki Seisakusho Co., Ltd.) is prepared as a measuring device. A rotor is rotated in a test tube containing 1 ml of a polymer sample. As the sample gels, the rotor falls due to a magnetic coupling mechanism and the timer stops when a certain torque is applied to the rotor. The time at this point is taken as the gelation time.

[0034] [Glass Transition Temperature] When the biomass epoxy resin composition of the present embodiment is cured, the Tg of the polymer is 60°C or higher. If the Tg of the polymer is lower than 60°C, the heat resistance decreases. The Tg of the polymer is preferably 100°C or higher. Note that a higher Tg is preferable, but it may be, for example, 300°C or lower.

[0035] Tg can be measured, for example, by the following procedure. As a measuring device, for example, a dynamic mechanical analysis (DMA) device (DMS6100, manufactured by Hitachi High-Tech Science Corporation) is prepared. Using a test piece (40 mm long x 10 mm wide x 1 to 3 mm thick) made of a polymer, measurement is performed under the following test conditions, and the peak top temperature of the loss tangent (tan δ) is taken as Tg. {Test conditions} Deformation mode: Tensile mode Measurement temperature: 25 to 250°C Heating rate: 2°C / min Frequency: 0.2 to 5 Hz

[0036] [Phase Structure] In this embodiment, the phase structure of the cured product of the biomass epoxy resin composition (hereinafter simply referred to as "phase structure") affects physical properties such as heat resistance and mechanical strength. Examples of the phase structure include a state in which the cured epoxy resin, which is a cured product of epoxy resin (A) and biomass-derived curing agent (B), is incompatible with the polymer and exists in a separated state, i.e., a phase-separated state, and a state in which the cured epoxy resin and the polymer are compatible with each other. The phase structure can be identified by the peak shape and peak temperature of tan δ of the dynamic viscoelasticity of the cured product.

[0037] When the Tg of the cured epoxy resin (hereinafter also referred to as Tg1) and the Tg of the polymer (hereinafter also referred to as Tg2) are different, if they are completely phase-separated from each other, two tan δ peaks will appear as the Tg's shown by each.

[0038] Furthermore, when a cured epoxy resin material and a polymer are compatible with each other, a single tan δ peak appears. When a cured epoxy resin material and a polymer are compatible with each other, the following situations can occur: (1) the cured epoxy resin material and the polymer have functional groups capable of chemically bonding to each other; (2) the cured epoxy resin material and the polymer each form a network structure but do not have functional groups capable of chemically bonding to each other; or (3) one of the cured epoxy resin material and the polymer forms a network structure, while the other is a long-chain polymer that does not form a network structure and does not have functional groups capable of chemically bonding to each other. In (1), the two network structures, or the network structure and the chain structure, form a single network structure through chemical bonding, resulting in a single tan δ peak. In (2), when the two network structures form an interpenetrating network (IPN) structure in which they are uniformly and physically entangled, a single tan δ peak appears. In (3), a semi-IPN structure is formed in which the long-chain polymer is physically entangled with the other network structure, resulting in a single tan δ peak.

[0039] Furthermore, the tan δ peak may appear as two peaks or a shoulder peak at values ​​different from the Tg values ​​of the cured epoxy resin and the polymer alone. In such cases, the following situations may occur: (1) the cured epoxy resin and the polymer have functional groups capable of chemically bonding to each other; (2) the network structures of the cured epoxy resin and the polymer are uniformly physically entangled to form an IPN structure; or (3) a long-chain polymer is physically entangled with the network structure of the other polymer to form a semi-IPN structure. In (1), the compatibility between the cured epoxy resin and the polymer is improved by chemical bonding, but partial or total phase separation occurs when there are few functional groups or the molecular weight of the polymer is high. In (2), if there are areas where the entanglement is weak, the polymer will undergo phase separation. In (3), similar to (2), if there are areas where the molecular chains are weakly entangled, the polymer will undergo partial or total phase separation.

[0040] In this embodiment, when Tg2 is lower than Tg1, it is preferred that the cured epoxy resin and the polymer in the biomass epoxy resin composition are phase-separated. In this case, Tg1 exhibits a Tg equivalent to that of the epoxy resin (A) alone, preventing a decrease in the Tg of the entire biomass epoxy resin composition.

[0041] On the other hand, when Tg2 is higher than Tg1, the cured epoxy resin and the polymer in the biomass epoxy resin composition are preferably completely or partially compatible with each other. In this case, Tg1 can be made higher than the Tg of the epoxy resin (A) alone, making the composition suitable for applications requiring higher heat resistance.

[0042] (Radioactive Carbon) The biomass epoxy resin composition of the present embodiment contains radioactive carbon (carbon-14, hereinafter referred to as "C14"). C14 is always present in the atmosphere at a constant rate. During the growth process, plants absorb CO2 from the atmosphere. ２Since plants absorb carbon dioxide, the carbon-14 content in plants is the same as that in the atmosphere. Fossil fuels, such as petroleum, do not contain carbon-14, making it possible to distinguish between biomass-derived carbon and petroleum-derived carbon. The current carbon-14 concentration in the atmosphere is approximately 100 pMC (percent modern carbon). If a biomass plastic were made from 100% biomass-derived materials, the pMC of that sample would be approximately 100. On the other hand, if the material were petroleum-derived, the pMC of that sample would be approximately 0. For example, a sample containing 50% biomass-derived and 50% petroleum-derived materials (based on the carbon content) would exhibit a value of approximately 50 pMC. Therefore, determining the carbon-14 content in a biomass epoxy resin composition allows us to verify the environmental impact of the biomass epoxy resin composition.

[0043] The C14 content of the total carbon in the biomass epoxy resin composition of this embodiment is 20% or more. The C14 content is calculated using the following formula (1): C14 content in biomass epoxy resin composition (%) = 100 × C14 content in biomass epoxy resin composition / total carbon content in biomass epoxy resin composition (1). If the C14 content in the biomass epoxy resin composition is less than 20%, the effect as a carbon offset material will be poor.

[0044] (Mixed Viscosity) From the viewpoint of workability, the mixed viscosity of the biomass epoxy resin composition at 60°C is preferably 5000 mPa·s or less, more preferably 1000 mPa·s or less, and even more preferably 300 mPa·s or less. In this embodiment, the mixed viscosity of the biomass epoxy resin composition is measured using an E-type viscometer. Note that a lower mixed viscosity is preferable, but it may be, for example, 10 mPa·s or more.

[0045] (Uses) The use of the biomass epoxy resin composition of this embodiment is not particularly limited, and it can be used in a variety of applications. For example, it may be dissolved in an organic solvent and used as a varnish for motors, or as in the second embodiment described below, it may be used as a molding resin for motors, power modules, etc. by adding a filler.

[0046] <Method for Producing Biomass Epoxy Resin Composition> The method for producing the biomass epoxy resin composition of this embodiment is not particularly limited. For example, epoxy resin (A) and biomass-derived curing agent (B) are mixed at room temperature or under heating to obtain a first mixture. The heating temperature is, for example, in the range of 40 to 180°C. Biomass-derived monomer (C) and polymerization initiator (D) are mixed at room temperature to obtain a second mixture. These first and second mixtures are heated and mixed to obtain a biomass epoxy resin composition. The heating temperature and heating time may be appropriately set depending on the epoxy resin (A), biomass-derived curing agent (B), and biomass-derived monomer (C) used. The heating temperature is, for example, in the range of 40 to 180°C, but is preferably in the range of 40 to 120°C from the viewpoint of suppressing volatilization of biomass-derived monomer (C). The heating time is, for example, in the range of 1 to 180 minutes. The degree of polymerization of the biomass-derived monomer (C) varies depending on the heating temperature and heating time. For example, the degree of polymerization may be the same when heated at a high temperature for a short time as when heated at a low temperature for a long time.

[0047] A solvent may be used when mixing the epoxy resin (A) and the biomass-derived curing agent (B). The solvent is not particularly limited, but examples thereof include toluene and methyl ethyl ketone.

[0048] Alternatively, for example, the epoxy resin (A), the biomass-derived curing agent (B), and the biomass-derived monomer (C) may be mixed at room temperature or under heating, and then the polymerization initiator (D) may be added and mixed at room temperature or under heating. The heating temperature when the epoxy resin (A), the biomass-derived curing agent (B), and the biomass-derived monomer (C) are mixed is, for example, in the range of 40 to 180°C. The heating temperature after the addition of the polymerization initiator (D) is, for example, in the range of 40 to 180°C.

[0049] The curing conditions for the biomass epoxy resin composition are not particularly limited, but for example, the heating temperature is in the range of 30 to 300° C., and the heating time is in the range of 1 minute to 100 hours.

[0050] Embodiment 2: The biomass epoxy resin composition according to this embodiment further contains an inorganic filler (E). By including the inorganic filler (E) in the biomass epoxy resin composition, it is possible to obtain a biomass epoxy resin composition with the desired mechanical strength and linear expansion coefficient. Explanations other than those that differ from embodiment 1 will be omitted.

[0051] (Inorganic filler (E)) The inorganic filler (E) is not particularly limited, but examples thereof include metal oxide particles such as aluminum oxide (alumina), zinc oxide, indium tin oxide (ITO), magnesium oxide, beryllium oxide, and titanium oxide, metal nitride particles such as boron nitride, silicon nitride, and aluminum nitride, carbon compound particles such as silicon carbide, graphite, diamond, amorphous carbon, carbon black, and carbon fiber, and silica compound powders such as quartz and quartz glass. These may be used alone or in combination of two or more. Among these, from the viewpoint of insulation, aluminum oxide (alumina), zinc oxide, magnesium oxide, beryllium oxide, titanium oxide, boron nitride, silicon nitride, aluminum nitride, diamond, quartz, and quartz glass are preferred.

[0052] The average particle size of the inorganic filler (E) is preferably 1 nm to 100 μm, more preferably 1 nm to 80 μm. If the average particle size of the inorganic filler (E) is less than 1 nm, the viscosity of the biomass epoxy resin composition may increase, potentially impairing workability and moldability. If the average particle size of the inorganic filler (E) is more than 100 μm, the strength of the cured product of the biomass epoxy resin composition may decrease, and sedimentation of the inorganic filler (E) may occur during storage of the biomass epoxy resin composition.

[0053] The content of inorganic filler (E) is preferably 40 to 90 wt %, more preferably 70 to 85 wt %, based on the total weight of the biomass epoxy resin composition. If the content of inorganic filler (E) is less than 40 wt %, it may be difficult to obtain a cured product of the biomass epoxy resin composition having the desired mechanical strength and thermal expansion coefficient. If the content of inorganic filler (E) is more than 90 wt %, the viscosity of the biomass epoxy resin composition may increase, which may impair workability and moldability.

[0054] (Coupling Agent) The inorganic filler (E) may be subjected to a coupling treatment with a coupling agent for the purposes of improving the wettability of the inorganic filler (E) with the biomass epoxy resin composition, reinforcing the interface between the inorganic filler (E) and the biomass epoxy resin composition, improving the dispersibility of the inorganic filler (E), etc. Examples of such coupling agents include γ-glycidoxypropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, etc. These may be used alone or in combination of two or more types.

[0055] The content of the coupling agent may be appropriately determined depending on the types of epoxy resin (A) and inorganic filler (E), and is, for example, 0.01 to 5 parts by weight per 100 parts by weight of epoxy resin (A).

[0056] (Production Method) The method for mixing the inorganic filler (E) is not particularly limited, and for example, the inorganic filler (E) may be mixed in the step of mixing the epoxy resin (A) and the biomass-derived curing agent (B) at room temperature or with heating to obtain a first mixture. For example, the inorganic filler (E) may be mixed in the step of heating and mixing the first mixture and the second mixture.

[0057] Furthermore, for example, the inorganic filler (E) may be mixed in the step of mixing the epoxy resin (A), the biomass-derived curing agent (B), and the biomass-derived monomer (C) at room temperature or under heating.

[0058] The coupling treatment of the inorganic filler (E) with a coupling agent may be carried out using a conventionally known method before mixing the inorganic filler (E).

[0059] Embodiment 3. The biomass epoxy resin composition according to this embodiment further contains a compatible monomer (F). By including the compatible monomer (F) in the biomass epoxy resin composition, the cured epoxy resin and the polymer partially form chemical bonds, improving the compatibility between the cured epoxy resin and the polymer. As a result, a biomass epoxy resin composition with improved heat resistance can be obtained. Note that a description of the differences from embodiment 1 will be omitted.

[0060] (Compatible Monomer (F)) The compatible monomer (F) is preferably a monomer having at least one functional group selected from the group consisting of a first functional group that reacts with the epoxy resin (A) and the biomass-derived monomer (C), and a second functional group that reacts with the biomass-derived curing agent (B) and the biomass-derived monomer (C).

[0061] Examples of the compatible monomer (F) having a first functional group include acrylates and methacrylates such as methacrylamide, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxyphenyl (meth)acrylate, 4-vinylphenol, and β-carboxyethyl acrylate, and styrenes such as p-acetoxystyrene, o-acetoxystyrene, m-acetoxystyrene, 3-methoxy-4-acetoxystyrene, and p-hydroxyphenylstyrene.

[0062] Examples of the compatible monomer (F) having a second functional group include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, (meth)allyl glycidyl ether, (meth)allyl methyl glycidyl ether, 3,4-epoxycyclohexylmethyl (meth)acrylate, and 4-hydroxybutyl acrylate glycidyl ether.

[0063] These may be used alone or in combination of two or more. Among these, glycidyl methacrylate is preferred from the viewpoint of compatibility.

[0064] The content of the compatible monomer (F) may be adjusted appropriately depending on the types of epoxy resin (A), biomass-derived curing agent (B), and biomass-derived monomer (C) used. The content of the epoxy resin (A) or the biomass-derived curing agent (B) may also be adjusted depending on the content of the compatible monomer (F).

[0065] The content of the compatible monomer (F) may be such that, when the epoxy groups in the molecules of the epoxy resin (A) react with the functional groups reactive with epoxy groups, such as active hydrogen of the amino groups, hydroxyl groups, carboxyl groups, acetoxy groups, and acid anhydrides in the molecules of the compatible monomer (F), at a chemical equivalent ratio of 1:1, the equivalent ratio of the functional groups in the molecules of the compatible monomer (F) to the epoxy groups in the molecules of the epoxy resin (A) is 0.3 to 3.0. If the ratio is outside the above range, there is a possibility that properties such as heat resistance will not be fully exhibited.

[0066] The content of the compatible monomer (F) may be such that, for example, when a functional group reactive with an epoxy group in a molecule of the biomass-derived curing agent (B) reacts with an epoxy group in a molecule of the compatible monomer (F) at a chemical equivalent ratio of 1:1, the equivalent ratio of the epoxy group in the molecule of the compatible monomer (F) to the functional group in the molecule of the biomass-derived curing agent (B) is 0.3 to 3.0. If the ratio is outside the above range, properties such as heat resistance may not be fully exhibited.

[0067] (Production Method) The method for mixing the compatible monomer (F) is not particularly limited, and for example, the biomass-derived monomer (C) and the polymerization initiator (D) may be mixed at room temperature, and the compatible monomer (F) may be mixed in the step of obtaining a second mixture. For example, the compatible monomer (F) may be mixed in the step of heating and mixing the first mixture and the second mixture.

[0068] Furthermore, for example, the compatible monomer (F) may be mixed in the step of mixing the epoxy resin (A), the biomass-derived curing agent (B), and the biomass-derived monomer (C) at room temperature or under heating.

[0069] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to these examples.

[0070] Example 1 The components (A) to (D) were prepared in the amounts shown in Table 1. Components (A-1) and (B-1) were heated and mixed at 130°C to obtain a first mixture. Components (C-1) and (D-1) were mixed uniformly at room temperature, and then component (D-2) was added and mixed uniformly to obtain a second mixture. The resulting first and second mixtures were mixed and heated at 100°C for 15 minutes to obtain the biomass epoxy resin composition of Example 1. The resulting biomass epoxy resin composition was then heated at 80°C for 2 hours, 130°C for 2 hours, and 180°C for 2 hours to obtain a cured biomass epoxy resin composition.

[0071] Examples 2 to 4 Biomass epoxy resin compositions and cured products thereof were obtained in the same manner as in Example 1, except that the blending amounts of component (C) and component (D) were changed to the amounts shown in Table 1.

[0072] Example 5 A biomass epoxy resin composition and a cured product thereof were obtained in the same manner as in Example 1, except that the amount of component (D) was changed to the amount shown in Table 1 and the heating time after mixing the first mixture and the second mixture was changed to 5 minutes.

[0073] Example 6 A biomass epoxy resin composition and a cured product thereof were obtained in the same manner as in Example 1, except that the component (B-1) was changed to the component (B-2), the component (C-1) to the component (C-2), and the amounts of the components (B) to (D) were changed to those shown in Table 1.

[0074] Example 7 Components (A) to (E) were prepared in the amounts shown in Table 1. Component (A-1) and component (B-1) were heated and mixed at 130°C to obtain a first mixture. Component (C-1) was heated and mixed with the obtained first mixture at 100°C, and after returning to room temperature, component (E-1) was added and mixed. Component (D-2) was added to these mixtures, mixed uniformly, and heated at 100°C for 15 minutes to obtain the biomass epoxy resin composition of Example 7. A cured product of the biomass epoxy resin composition was produced in the same manner as in Example 1.

[0075] Example 8 The components (A) to (F) were prepared in the amounts shown in Table 1. Components (A-1) and (B-1) were heated and mixed at 130°C to obtain a first mixture. Components (C-1), (F-1), and (D-1) were uniformly mixed at room temperature, and then component (D-2) was added and mixed uniformly to obtain a second mixture. The resulting first and second mixtures were mixed and heated at 100°C for 15 minutes to obtain the biomass epoxy resin composition of Example 8. A cured product of the biomass epoxy resin composition was produced in the same manner as in Example 1.

[0076] Comparative Example 1 Component (A) and component (B') were prepared in the amounts shown in Table 1. Component (A-1) and component (B'-1) were heated at 100°C for 15 minutes to obtain a biomass epoxy resin composition of Comparative Example 1. Thereafter, a cured product was obtained in the same manner as in Example 1.

[0077] Comparative Example 2 Component (A) and component (B) were prepared in the amounts shown in Table 1. Component (A-1) and component (B-1) were heated at 100°C for 15 minutes to obtain a biomass epoxy resin composition of Comparative Example 2. Thereafter, a cured product was obtained in the same manner as in Example 1.

[0078] Comparative Example 3: Component (A) and component (B) were prepared in the amounts shown in Table 1. Component (A-1) and component (B-2) were heated at 100°C for 15 minutes to obtain a biomass epoxy resin composition of Comparative Example 3. Thereafter, a cured product was obtained in the same manner as in Example 1.

[0079] Comparative Example 4 A biomass epoxy resin composition and a cured product thereof were obtained in the same manner as in Example 1, except that the component (C-1) was changed to the component (C'-1) and the amount of the component (C') was changed to the amount shown in Table 1.

[0080] Comparative Example 5 A biomass epoxy resin composition and a cured product thereof were obtained in the same manner as in Example 1, except that the blending amount of component (D) was changed to the amount shown in Table 1 and the heating time after mixing the first mixture and the second mixture was changed to 60 minutes.

[0081] Comparative Example 6 Components (A), (B), and (E) were prepared in the amounts shown in Table 1. Components (A-1) and (B-1) were heated and mixed at 130°C to obtain a first mixture. After cooling the obtained first mixture to 80°C, component (E-1) was added, and the mixture was mixed uniformly. The mixture was then heated at 100°C for 15 minutes to obtain the biomass epoxy resin composition of Comparative Example 6. A cured product of the biomass epoxy resin composition was produced in the same manner as in Example 1.

[0082] The components shown in Table 1 (each component symbolized) are as follows:

[0083] [Epoxy Resin: Component A] (A-1) Bisphenol A type epoxy resin [jER828 manufactured by Mitsubishi Chemical Corporation] (liquid at room temperature)

[0084] [Biomass-derived curing agent: Component B] (B-1) 4-aminobenzoic acid (solid at room temperature) (B-2) 4-hydroxybenzoic acid (solid at room temperature)

[0085] [Petroleum-derived curing agent: component B'] (B'-1) Acid anhydride curing agent [HN2000 manufactured by Showa Denko Materials Co., Ltd.] (liquid at room temperature)

[0086] [Biomass-derived monomers: component C] (C-1) Isobornyl (meth)acrylate (IBOMA) (liquid at room temperature) (Tg: 180°C) (C-2) Tetrahydrofurfuryl (meth)acrylate (liquid at room temperature) (Tg: 60°C) (C-3) Tetrahydrofurfuryl acrylate (liquid at room temperature) (Tg: -12°C)

[0087] [Polymerization initiator: component D] (D-1) Curing agent 328E [manufactured by Kayaku Akzo Co., Ltd.] (D-2) Cobalt octoate

[0088] [Inorganic filler: component E] (E-1) Fused silica [FB74 manufactured by Denka Co., Ltd.] (average particle size: 30 μm)

[0089] [Compatible Monomer: Component F] (F-1) Glycidyl methacrylate (GM) (liquid at room temperature) (Tg: 46°C)

[0090] <Evaluation Method> Evaluations were performed by the following methods: (1) The sample used for evaluating gelation time and (2) Tg was a polymer obtained by polymerizing only component (C), (3) the sample used for evaluating C14 was a biomass epoxy resin composition, and (5) the sample used for evaluating tan δ peak temperature was a cured product of the biomass epoxy resin composition.

[0091] (1) Gel Time A gelation tester (No. 153 Gel Time Tester, manufactured by Yasuda Seiki Seisakusho Co., Ltd.) was prepared. A rotor was rotated in a test tube containing 1 ml of sample. As the sample gelled, a certain torque was applied to the rotor, causing the rotor to drop due to the magnetic coupling mechanism. The time at which the timer stopped was recorded as the gelation time of each sample. Measurements were performed by heating the test tube to 100°C in an oil bath.

[0092] (2) Tg A DMA apparatus (DMS6100 manufactured by Hitachi High-Tech Science Corporation) was prepared. A polymer test piece (40 mm length x 10 mm width x 1 to 3 mm thickness) was used and measured under the following test conditions. The peak top temperature of tan δ in this measurement was taken as Tg. {Test conditions} Deformation mode: Tensile mode Measurement temperature: 25 to 250°C Heating rate: 2°C / min Frequency: 0.2 to 5 Hz

[0093] (3) C14 The C14 content of each sample was calculated using the following formula (1): C14 content (%) in biomass epoxy resin composition = 100 × C14 content in biomass epoxy resin composition / total carbon content in biomass epoxy resin composition (1)

[0094] (4) Mixed Viscosity An E-type viscometer (RE105U, manufactured by Toki Sangyo Co., Ltd.) was prepared. Mixtures containing each of the components (A) to (C) were prepared as samples. The mixtures were prepared by heating and mixing components (A) and (B) at 130°C, and component (C) at 100°C. The sample not containing component (C) was prepared by heating and mixing components (A) and (B) at 130°C. The mixed viscosity of each mixture at 60°C was measured. Mixed viscosities of less than 300 mPa·s were rated "W," 300 mPa·s or more but less than 1000 mPa·s as "X," 1000 mPa·s or more but less than 5000 mPa·s as "Y," and 5000 mPa·s or more as "Z," with all viscosity grades other than "Z" being rated as "good." The reason for using such a sample is that when component (D) is added and heated, the polymerization reaction begins, causing the mixed viscosity to change (increase) over time. Note that, since the content of component (D) in the biomass epoxy resin composition is small, adding component (D) does not affect the mixed viscosity of the biomass epoxy resin composition.

[0095] (5) tan δ peak temperature The above-mentioned DMA apparatus was prepared. The tan δ peak temperature of each sample was measured. When two peaks were obtained, the value with the higher tan δ peak value (intensity) was taken as the tan δ peak temperature.

[0096] The evaluation results of the obtained evaluation samples according to the above items (1) to (5) are shown in Table 1.

[0097]

[0098] <Results> The biomass epoxy resin compositions of the examples use a biomass-derived curing agent (B) and a biomass-derived monomer (C), and have a C14 content of 20% or more, making them environmentally friendly. Furthermore, the biomass epoxy resin compositions of the examples have excellent workability, as the polymer gel time is within 20 minutes. Furthermore, the biomass epoxy resin compositions of the examples have excellent heat resistance, as the polymer Tg is 60°C or higher.

[0099] It was confirmed that the mixed viscosities of Examples 1 to 5 and 8 were significantly lower than those of Comparative Examples 2 and 3, which did not contain the biomass-derived monomer (C). In particular, in Examples 3 and 4, by adding 50% by weight or more of the biomass-derived monomer (C), the mixed viscosities were equal to or lower than that of the acid anhydride-cured epoxy resin composition used as a potting material, as shown in Example 1.

[0100] It was also confirmed that the mixed viscosity of Example 7 was significantly lower than that of Comparative Example 6 in which no biomass-derived monomer (C) component was added.

[0101] These results confirmed that the inclusion of the biomass-derived monomer (C) significantly improved workability, and that increasing the content of the biomass-derived monomer (C) further improved workability.

[0102] In Examples 1 to 4, the tan δ peak was broad, confirming that the cured epoxy resin and the polymer were partially compatible. On the other hand, in Example 5, two tan δ peaks were obtained, confirming that the cured epoxy resin and the polymer were phase-separated. As shown in Example 5, when the gelation time of the polymer is short, it is thought that the cured epoxy resin and the polymer are not fully compatible, and a cured product of the biomass epoxy resin composition is formed in a partially phase-separated state.

[0103] From the tan δ peak temperatures shown in Examples 1 to 4, it was confirmed that the Tg of the cured product of the biomass epoxy resin composition increased as the amount of IBOMA added increased, which has a Tg of 180°C for the polymer alone. In Examples 1 and 2, the tan δ peak temperature showed a value between the Tg of the cured epoxy resin and the Tg of the polymer. This is presumably because the cured epoxy resin and the polymer are partially compatible with each other, resulting in the Tg of the entire biomass epoxy resin composition being a value between the Tg of the cured epoxy resin and the Tg of the polymer.

[0104] Furthermore, the tan δ peak temperature was higher than the Tg of the polymer alone in Examples 3 and 4. This is presumably because the molecular chains of the cured epoxy resin and the polymer were physically entangled and constrained, resulting in a higher Tg than that of the polymer alone, and improved heat resistance.

[0105] In the case of Example 5 where partial phase separation occurs between the cured epoxy resin and the polymer, the lower of the two tan δ peak temperatures exhibited a value equivalent to that of the biomass-derived epoxy resin composition of Comparative Example 2, which does not contain the biomass-derived monomer (C). However, it was confirmed that even in the case where partial phase separation occurs between the cured epoxy resin and the polymer, the inclusion of the biomass-derived monomer (C) can improve workability and heat resistance.

[0106] These results confirmed that the inclusion of the biomass-derived monomer (C) can improve heat resistance.

[0107] Even when the Tg of the polymer is relatively low as in Example 6, it was confirmed that the mixing viscosity can be reduced compared to Comparative Example 3, which does not contain the biomass-derived monomer (C), and therefore workability can be improved.

[0108] Examples 1 and 8 have the same content of monomer components. Example 1 uses only IBOMA, which has a Tg of 180°C as a polymer alone, while Example 8 uses equal amounts of IBOMA and GM, which has a Tg of 46°C as a polymer alone. Although the Tgs of IBOMA and GM as polymers differ significantly, the tan δ peak temperature of Example 7 is higher than that of Example 1. This is presumably because the inclusion of the compatible monomer (F) in the biomass epoxy resin composition allows the cured epoxy resin material and the polymer to form partial chemical bonds in addition to physical entanglement of molecular chains, thereby improving the compatibility between the cured epoxy resin material and the polymer and improving heat resistance.

[0109] These results confirm that the inclusion of the compatible monomer (F) can improve heat resistance.

[0110] Comparative Example 1 is poor in environmental friendliness because it does not contain the biomass-derived curing agent (B) and the biomass-derived monomer (C).

[0111] Comparative Examples 2 and 3 are inferior in workability compared to Examples 1 to 6 because they do not contain the biomass-derived monomer (C).

[0112] In Comparative Example 4, the Tg of the polymer is less than 60° C., and therefore the heat resistance is poor.

[0113] In Comparative Example 5, the gelation time of the polymer at 100°C exceeded 20 minutes, which led to the volatilization of the biomass-derived monomer (C) and the suppression of the degree of polymerization of the biomass-derived monomer (C). As a result, a low-molecular-weight polymer was formed, and the Tg of the polymer was also lower than 60°C, which is thought to have resulted in a decrease in heat resistance.

[0114] The embodiments and examples disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

Claims

1. A biomass epoxy resin composition comprising an epoxy resin, a biomass-derived curing agent, a biomass-derived monomer, and a polymerization initiator, the gelation time of the polymer of the monomer at 100° C. or less is 20 minutes or less; A biomass epoxy resin composition, wherein the glass transition temperature of the polymer of the monomer is 60°C or higher.

2. The biomass epoxy resin composition according to claim 1, wherein the content of radioactive carbon relative to the total carbon in the biomass epoxy resin composition is 20% or more.

3. The biomass epoxy resin composition according to claim 1 or 2, wherein the curing agent comprises at least one selected from the group consisting of 4-aminobenzoic acid, 4-hydroxybenzoic acid and protocatechuic acid.

4. 3. The biomass epoxy resin composition according to claim 1 or 2, wherein the monomer comprises at least one selected from the group consisting of ethyl methacrylate, tetrabutyl methacrylate, cyclohexyl methacrylate, tetrahydrofurfuryl methacrylate and isobornyl (meth)acrylate.

5. The biomass epoxy resin composition according to claim 1 or 2, wherein the polymerization initiator comprises at least one selected from the group consisting of hydroperoxides and ketone peroxides, and a metal salt.

6. The biomass epoxy resin composition according to claim 1 or 2, further comprising an inorganic filler.

7. 3. The biomass epoxy resin composition according to claim 1 or 2, further comprising a compatible monomer.

8. 8. The biomass epoxy resin composition of claim 7, wherein the compatible monomer is glycidyl methacrylate.