JP7595335B2 - Raw material for composite material, its manufacturing method, and composite material - Google Patents

Description

The present invention relates to raw materials for composite materials, their manufacturing method, and composite materials.

Particle-dispersed composite materials, in which particles as reinforcing materials are dispersed in a resin as a base material, have been attracting attention in recent years because they have the potential to simultaneously exhibit the excellent properties of both materials. Because this type of composite material is made up of a combination of resin and particles, it is important to improve the affinity between the resin and the particles and to uniformly disperse the particles in the resin. Previously, efforts have been made to improve the mechanical properties of composite materials, such as the tensile strength, by improving the affinity between the resin and the particles to improve adhesion between them, or by improving the dispersibility of the particles in the resin by modifying the resin or particles.

Surface modification of particles through chemical reactions is widely used as a method for improving the adhesion between resin and particles in composite materials. For example, Patent Document 1 discloses a technology relating to a resin composition in which the surface of a spherical substrate is modified with a silane coupling agent, dried, and then dispersed in a resin, and a resin molded product obtained by molding the resin composition. Patent Document 2 discloses a technology relating to a nanocomposite in which a graft polymer having graft chains with specific functional groups is synthesized and nanoparticles are dispersed in the polymer in order to uniformly disperse particles in a resin.

WO2018/043246 publication JP 2006-307199 A

However, the technique of Patent Document 1 requires drying the particles after modification with the silane coupling agent, which may lead to particle aggregation due to drying. Aggregated particles may lead to a decrease in the strength of the composite material. Furthermore, the technique of Patent Document 2 requires the advance synthesis of a special graft polymer to improve particle dispersion, which may complicate the manufacturing process of the raw material for the composite material. Furthermore, these techniques also require a separate process for uniformly dispersing the particles in the resin. Therefore, with the conventional techniques, it is difficult to relatively easily manufacture raw materials for composite materials that can produce composite materials with improved tensile strength. As a result, it is also difficult to obtain composite materials with improved tensile strength using the raw materials for composite materials.

The present invention has been made in view of these problems, and aims to provide a method for relatively easily producing raw materials for composite materials that can produce composite materials with improved tensile strength, raw materials for composite materials that can produce composite materials with improved tensile strength, and composite materials with improved tensile strength.

One aspect of the present invention is
A raw material for a composite material used in a particle dispersion reinforced composite material in which particles as a reinforcing material are dispersed in a resin as a matrix (excluding those in which the particles as the reinforcing material are oriented in the resin as the matrix) ,
a dispersion medium containing at least one of the resin serving as the base material of the composite material and a resin component serving as a component for constituting the resin serving as the base material of the composite material (excluding a chain aliphatic epoxy resin having a hydrophilic group, a resin having a fluorene skeleton, and a rubber latex) and a solvent ;
A plurality of particles (excluding granular adsorbent fillers in which cellulose or a thermoplastic resin is adsorbed on a filler, and nanoparticles in which one or more oligomers derived from two or more polymerizable units are covalently bonded via a coupling agent ) dispersed in the dispersion medium;
a coating layer covering the surface of the particle,
the coating layer is formed from a resin-derived component that is derived from at least one of the resin and the resin component contained in the dispersion medium and that is adsorbed on the surface of the particle ,
The coating layer is formed by applying a shear force to a mixture containing the dispersion medium and the particles , in the raw material for a composite material.

Another aspect of the present invention is
A method for producing a raw material for a composite material used in a particle-dispersion-reinforced composite material in which particles as a reinforcing material are dispersed in a resin as a matrix (excluding those in which the particles as the reinforcing material are oriented in the resin as the matrix) , comprising:
a preparation step of preparing a mixture including a dispersion medium containing at least one of the resin serving as the base material of the composite material and a resin component serving as a component for constituting the resin serving as the base material of the composite material (excluding a chain aliphatic epoxy resin having a hydrophilic group, a resin having a fluorene skeleton, and a rubber latex) and a solvent , and a plurality of particles (excluding cellulose , a granular adsorption filler in which a thermoplastic resin is adsorbed onto a filler, and nanoparticles in which one or more oligomers derived from two or more polymerizable units are covalently bonded via a coupling agent) mixed in the dispersion medium ;
a mechanical treatment step of dispersing a plurality of the particles in the dispersion medium by applying a shear force to the prepared mixture, and coating the surfaces of the particles with a coating layer formed from a resin-derived component adsorbed on the surfaces of the particles, the resin being derived from at least one of the resin and the resin component contained in the dispersion medium;
The present invention relates to a method for producing a raw material for a composite material, comprising the steps of:

Yet another aspect of the present invention is a composite material formed using the above-mentioned composite material raw material.

The above-mentioned method for producing raw materials for composite materials has the above-mentioned steps. Therefore, according to the above-mentioned method for producing raw materials for composite materials, dispersion of particles in a dispersion medium containing at least one of a resin and a resin component, and surface coating of the particle surfaces with a resin-derived component derived from at least one of the resin and the resin component contained in the dispersion medium can be carried out in one step. Furthermore, the above-mentioned method for producing raw materials for composite materials does not necessarily require pretreatment of the particles with a surface modifier, and does not require the synthesis of a special resin in advance. Therefore, the above-mentioned method for producing raw materials for composite materials can produce raw materials for composite materials relatively easily compared to conventional production methods.

The composite material raw material has the above-mentioned configuration. The composite material raw material can be obtained by the manufacturing method of the composite material raw material. The composite material molded using the composite material raw material can exhibit a higher tensile strength than a reference composite material molded using a reference raw material to which particles are first mixed in a resin-free dispersion medium that does not contain resin or resin components, and then mechanically treated and resin or resin components are added. This is thought to be due to the fact that in the composite material raw material, the resin or resin component and the coating layer are of the same resin system, so there is a high affinity, the adhesion between the particles and the coating layer is improved, and the particles have high dispersibility.

Therefore, according to the present invention, it is possible to provide a method for relatively easily producing a raw material for a composite material that can produce a composite material with improved tensile strength, a raw material for a composite material that can produce a composite material with improved tensile strength, and a composite material with improved tensile strength.

FIG. 1 is an explanatory diagram that shows a schematic diagram of a composite material raw material according to the present embodiment. FIG. 2 is an explanatory diagram that shows a schematic diagram of the manufacturing method of the composite material raw material of this embodiment, where (a) is an explanatory diagram that shows a schematic diagram of the mixture prepared in the preparation step, and (b) is an explanatory diagram that shows a schematic diagram of the composite material raw material obtained through the mechanical treatment step. FIG. 3 is an explanatory diagram for explaining the mechanical treatment in the mechanical treatment step of the method for producing a raw material for a composite material according to this embodiment. FIG. 4 is an explanatory diagram showing details of a nozzle member provided in a dispersion nozzle section of a wet jet mill used in an experimental example, where (a) is a cross-sectional view of the nozzle member, (b) is an arrow view taken along line IVb-IVb in (a), (c) is an arrow view taken along line IVc-IVc in (a), (d) is an arrow view taken along line IVd-IVd in (a), and (e) is an arrow view taken along line IVe-IVe in (c). FIG. 5 is a scanning electron microscope photograph of a fracture surface after a tensile test of a composite material molded using the composite material raw material of Sample 1-1 obtained in an experimental example. FIG. 6 is a scanning electron microscope photograph of a fracture surface after a tensile test of a composite material molded using the composite material raw material of Sample 1R obtained in an experimental example. FIG. 7 shows an infrared spectrum of an epoxy base resin obtained by an infrared spectrophotometer in an experimental example. FIG. 8 shows infrared spectra obtained by an infrared spectrophotometer in an experimental example of the aluminum oxide powder itself, the aluminum oxide powders recovered from the composite material raw materials of Sample 1-1 and Sample 1-2, and the aluminum oxide powder recovered from the reference raw material of Sample 1R. FIG. 9 shows infrared spectra of the silicon dioxide powder itself, the silicon dioxide powder recovered from the composite material raw material of sample 2, and the silicon dioxide powder recovered from the reference raw material of sample 2R, obtained by an infrared spectrophotometer in the experimental example. FIG. 10 is an enlarged view of the infrared spectrum shown in FIG. FIG. 11 shows infrared spectra obtained by an infrared spectrophotometer in an experimental example of the magnesium oxide powder itself, the magnesium oxide powder recovered from the composite material raw material of sample 3, and the magnesium oxide powder recovered from the reference raw material of sample 3R. FIG. 12 is a diagram showing the relationship between the particle size (nm) and the accumulation (volume %) or frequency (volume %) before and after the mechanical treatment in the preparation of the composite material raw material of Sample 1-1. FIG. 13 is a graph showing the relationship between the particle size (nm) and the accumulation (volume %) or frequency (volume %) before and after the mechanical treatment in the preparation of the composite material raw material of Sample 1-2. FIG. 14 is a graph showing the relationship between the particle size (nm) and the accumulation (volume %) or frequency (volume %) before and after the mechanical treatment in the preparation of the composite material raw material of Sample 2. FIG. 15 is a graph showing the relationship between the particle size (nm) and the accumulation (volume %) or frequency (volume %) before and after the mechanical treatment in the preparation of the composite material raw material of Sample 3. FIG. 16 is a graph showing the relationship between the particle size (nm) and the accumulation (volume %) or frequency (volume %) before and after the mechanical treatment in the preparation of the composite material raw material of sample 1R. FIG. 17 is a diagram showing the relationship between the particle size (nm) and the accumulation (volume %) or frequency (volume %) before and after the mechanical treatment in the preparation of the composite material raw material of sample 2R. FIG. 18 is a graph showing the relationship between the particle size (nm) and the accumulation (volume %) or frequency (volume %) before and after the mechanical treatment in the preparation of the composite material raw material of sample 3R. FIG. 19 is a diagram showing the relationship between particle size (nm) and accumulation (volume %) in the composite material raw materials of Samples 1-1C to 1-3C. FIG. 20 is a diagram showing the relationship between particle size (nm) and frequency (volume %) in the composite material raw materials of Samples 1-1C to 1-3C.

The composite material raw material, the manufacturing method for the composite material raw material, and the composite material of this embodiment will be described in detail with reference to Figures 1 to 3.

(Raw material for composite materials)
As illustrated in FIG. 1 , a composite material raw material 1 of this embodiment includes a dispersion medium 10 , a plurality of particles 11 , and a coating layer 12 .

The dispersion medium 10 contains at least one of the resin 101 and the resin component 102. The resin 101 contained in the dispersion medium 10 is the base material (matrix) of the composite material. Examples of the resin 101 include curable resins such as thermosetting resins and ultraviolet curable resins, and thermoplastic resins. These can be used alone or in combination of two or more. The resin component 102 contained in the dispersion medium 10 is a component for constituting the resin 101 that is the base material of the composite material, and specifically includes monomers, oligomers, prepolymers, etc. These can be used alone or in combination of two or more. In addition, among the above-mentioned resins 101, the curable resin may be composed of a base agent and a curing agent (including a curing accelerator). The base agent and curing agent for constituting the curable resin are included in the concept of resin components.

The dispersion medium 10 includes a solvent 103 (which can also be called a diluent) such as an aqueous solvent or an organic solvent (organic solvent) in addition to the resin 101 and the resin component 102. More specifically, the dispersion medium 10 can be composed of the resin 101 or the resin component 102 and the solvent 103 when the resin 101 or the resin component 102 used is liquid. The dispersion medium 10 can be composed of the resin 101 or the resin component 102 and the solvent 103 when the resin 101 or the resin component 102 used is solid. That is, in this case, the solid resin 101 or the resin component 102 is dissolved in the solvent 103. The dispersion medium 10 preferably includes the solvent 103 from the viewpoint of improving the dispersibility of the particles 11. The solvent 103 may be used alone or in a mixture of two or more types. The type of the solvent 103 can be appropriately selected according to the type of the resin 101 or the resin component 102 used. Furthermore, the aqueous solvent as the solvent 103 may contain ions for adjusting the pH or ionic strength.

Examples of resin 101 include thermosetting resins such as epoxy resin, phenolic resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, oxazine resin, bismaleimide resin, and triazine resin, and thermoplastic resins such as polyamide, polyester, polycarbonate, acrylic polymer, methacrylic polymer, polyimide, liquid crystal polymer, polyolefin, polystyrene, and polyphenylene ether.

Examples of resin component 102 include an epoxy resin base, an epoxy resin hardener, a phenolic compound, melamine, urea, styrene, a fatty acid, benzoxazine, and epsilon caprolactam. The above-mentioned resin 101 and resin component 102 can be used alone or in combination of two or more kinds.

The plurality of particles 11 are dispersed in the dispersion medium 10. Examples of the shape of the particles 11 include spherical shapes such as perfect spheres, elliptical spheres, oval spheres, and chunky spheres, and shapes in which the length in the long axis direction differs from the length in the short axis direction, such as plate-like, scaly, rod-like, needle-like, and fibrous shapes. These may be used alone or in combination of two or more kinds.

The particles 11 can be made of any material as long as it can improve at least the tensile strength of the mechanical properties of the composite material. Examples of the particles 11 include ceramic particles, metal particles, carbon particles, and organic particles. These can be used alone or in combination of two or more types. This configuration makes it easier to improve the tensile strength of the composite material.

Examples of ceramics constituting the ceramic particles include aluminum oxide (alumina), zinc oxide, magnesium oxide, silicon oxide, titanium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, silicon carbide, aluminum hydroxide, magnesium hydroxide, zirconium oxide (zirconia), and yttrium oxide (yttria). These can be used alone or in combination of two or more.

Examples of metals constituting the metal particles include gold, silver, copper, platinum group metals, and alloys of these metals. These metals can be used alone or in combination of two or more.

Examples of carbon constituting the carbon particles include carbon black, diamond, graphite, carbon nanotubes, carbon nanofibers, fullerenes, and ground carbon fibers (milled fibers). These can be used alone or in combination of two or more.

Examples of organic matter constituting the organic particles include cellulose, chitosan, chitin, etc. These can be used alone or in combination of two or more.

The coating layer 12 covers the surface of each particle 11. The coating layer 12 may cover the entire surface of the particle 11, or may cover a part of the surface of the particle 11. Here, the coating layer 12 is formed from a resin-derived component derived from at least one of the resin 101 and the resin component 102 contained in the dispersion medium 10. In other words, the coating layer 12 is formed from a part of the resin 101 and the resin component 102 contained in the dispersion medium 10. Specifically, the resin-derived component may be the same as at least one of the resin 101 and the resin component 102 contained in the dispersion medium 10, or may have a molecular structure that is partially different from that of at least one of the resin 101 and the resin component 102 contained in the dispersion medium 10 due to a chemical reaction with the particle surface, etc.

The resin-derived component can be configured to be adsorbed onto the surface of the particle 11. This configuration increases the adhesion between the particle 11 and the coating layer 12, ensuring an improvement in the tensile strength of the composite material. The adsorption may be either chemical adsorption or physical adsorption. Chemical adsorption is advantageous for improving the adhesion of the coating layer 12 through covalent bonds between the particle 11 surface and the resin-derived component.

The adsorption of the resin-derived component to the particle 11 surface can be confirmed by the following example. A plurality of particles 11 covered with the coating layer 12 are collected from the composite material raw material 1 by centrifugation, filtration, etc. Next, the collected particles 11 are thoroughly washed with a solvent in which the resin 101 and the resin component 102 dissolve in order to remove unnecessary components such as unadsorbed components, and are vacuum-dried to obtain a powder. Next, an infrared spectrum is obtained for the dried powder by a diffuse reflectance method using an infrared spectrophotometer. Next, the presence or absence of a peak derived from the resin or the resin component in the obtained infrared spectrum is observed. If a peak derived from the resin or the resin component is observed, it can be determined that at least a part of the resin 101 and the resin component 102 contained in the dispersion medium 10 is adsorbed to the surface of the particle 11. On the other hand, if a peak derived from the resin or the resin component is not observed, it can be determined that at least a part of the resin 101 and the resin component 102 contained in the dispersion medium 10 is not adsorbed to the surface of the particle 11.

In this disclosure, the reference raw material is a raw material for a composite material prepared by using a dispersion medium that does not contain the resin 101 or resin component 102 contained in the coating layer 12 of the particle 11 instead of the dispersion medium 10 used in the raw material for a composite material 1. The coating ratio, which is defined as the ratio of the coating amount of the coating layer 12 covering the surface of the particle 11 in the raw material for a composite material 1 to the coating amount of the coating layer covering the surface of the particle in the reference raw material, can be 1.3 times or more. Note that the coating amount of the coating layer 12 can be said to be the adsorption amount of the resin-derived component on the surface of the particle 11 when the resin-derived component is adsorbed on the surface of the particle 11. In addition, the above-mentioned coating ratio can be, for example, 20.0 times or less from the viewpoint that if the coating ratio is too large, the apparent particle diameter becomes large and the maximum loading amount of the particle decreases.

The reference raw material is prepared as follows. Specifically, the type of particles 11 in the raw material 1 for composite material and the type of resin 101 or resin component 102 that is the source of the resin-derived component that forms the coating layer 12 that covers the surface of the particles 11 are identified. For the identification, a measurement method such as powder X-ray diffraction measurement, energy dispersive X-ray spectroscopy measurement, Fourier transform infrared spectroscopy measurement, Raman spectroscopy measurement, etc. can be used. A resin-free mixture containing a resin-free dispersion medium that does not contain resin 101 and resin component 102 and a plurality of particles 11 is prepared. After subjecting the prepared resin-free mixture to mechanical processing using a wet jet mill, the same resin 101 or resin component 102 as that specified above is mixed so that the volume ratio of the plurality of particles 11 is the same as that of the raw material 1 for composite material. The conditions for the mechanical processing using the wet jet mill are: diameter of the small hole of the dispersion nozzle part of the wet jet mill: 0.17 mm, pressure: 200 MPa, and number of mechanical processing times: 5 times. The resin-containing mixture obtained in this manner is used as the reference raw material.

The amount of coating of the coating layer 12 can be measured as follows. A plurality of particles 11 whose surfaces are covered with the coating layer 12 are collected from the composite material raw material 1 by centrifugation, filtration, or the like. Next, the collected particles 11 are thoroughly washed with a solvent in which the resin 101 and the resin component 102 dissolve in order to remove unnecessary components such as unadsorbed components, and then vacuum dried to obtain a powder. Next, the mass reduction rate of the dried powder is measured from 150°C to 600°C at a heating rate of 10°C/min using a thermogravimetric differential thermal analyzer. The mass reduction rate (mass%) can be calculated by the formula 100 x (mass at 150°C - mass at 600°C) / (initial mass <mass at room temperature>). The mass reduction rate obtained above is the amount of coating of the coating layer 12 on each particle 11. In other words, the amount of coating of the coating layer 12 is the mass% of the coating layer 12 relative to the particles 11 coated with the coating layer 12 measured by thermogravimetric differential thermal analysis. The reference material can also be measured in the same way.

Specifically, for example, when the particles 11 are made of aluminum oxide, the amount of coating of the coating layer 12 is preferably 0.25% by mass or more, more preferably 0.50% by mass or more, even more preferably 0.75% by mass or more, even more preferably 1.00% by mass or more, even more preferably 1.25% by mass or more, and most preferably 1.50% by mass or more. Also, for example, when the particles 11 are made of silicon dioxide, the amount of coating of the coating layer 12 is preferably 1.20% by mass or more, more preferably 1.30% by mass or more, and even more preferably 1.40% by mass or more. Also, for example, when the particles 11 are made of magnesium oxide, the amount of coating of the coating layer 12 is preferably 2.20% by mass or more, more preferably 2.40% by mass or more, even more preferably 2.60% by mass or more, even more preferably 2.80% by mass or more, and even more preferably 3.00% by mass or more. In addition, when the particles 11 are made of aluminum oxide, when the particles 11 are made of silicon dioxide, or when the particles 11 are made of magnesium oxide, the amount of coating layer 12 can be 10.00 mass% or less. If the amount of coating layer 12 is too large, the apparent particle size becomes large, and the maximum loading amount of particles 11 decreases.

At least one of the resin 101 and the resin component 102 can have a reactive functional group in its molecular structure that reacts with the surface of the particle 11. The functional group may be one type or two or more types in the molecular structure. With this configuration, a covalent bond can be formed between the surface of the particle 11 and the resin-derived component via the functional group contained in the resin-derived component. Therefore, with this configuration, the adhesion between the particle 11 and the coating layer 12 is increased, which is advantageous for improving the tensile strength of the composite material.

At least one of the resin and the resin component may have functional groups in its molecular structure, such as hydroxyl groups, aldehyde groups, carboxyl groups, carbonyl groups, amino groups, nitro groups, sulfo groups, ketone groups, acetyl groups, azo groups, vinyl groups, epoxy groups, styryl groups, methacryl groups, acrylic groups, isocyanate groups, mercapto groups, and silyl groups. One or more of these functional groups may be contained in the molecular structure.

The median diameter D50 of the particles 11 whose surfaces are covered with the coating layer 12 can be 3.0 nm or more and 1.0 x ¹⁰⁵ nm or less. The median diameter D50 of the particles 11 whose surfaces are covered with the coating layer 12 is measured by a laser diffraction type particle size distribution measuring device. Specifically, the median diameter D50 of the particles 11 whose surfaces are covered with the coating layer 12 is the particle diameter when the volume-based cumulative frequency distribution measured by the laser diffraction type particle size distribution measuring device indicates 50%. By setting the median diameter D50 of the particles 11 whose surfaces are covered with the coating layer 12 to 3.0 nm or more, the particles 11 are not too small, and the characteristics of the particles 11 can be easily reflected in the composite material. By setting the median diameter D50 of the particles 11 whose surfaces are covered with the coating layer 12 to 1.0 × 10 ⁵ nm or less, the surface area of the particles 11 is large, so that the coating layer 12 is easily formed during the production of the composite material raw material 1 described later, and mechanical processing in which a shear force is applied can be easily performed.

The median diameter D50 of the particles 11 whose surfaces are covered with the coating layer 12 can be preferably 1.0× ¹⁰¹ nm or more, more preferably 2.0× ¹⁰¹ nm or more, and even more preferably 3.0×101 nm or more, from the viewpoint of ensuring the above-mentioned effects. The median diameter D50 of the particles 11 whose surfaces are covered with the coating layer 12 can be preferably 5.0× ^{104 nm or less, more preferably 3.0×104 nm} or less, and even more preferably 1.0× ^{104 nm} or less, from the viewpoint of ensuring the above-mentioned effects.

The volume ratio of the particles 11 to the total volume of the particles 11 and at least one of the resin 101 and the resin component 102 in the dispersion medium 10 can be 1.0 volume % or more and 90.0 volume % or less. In other words, the volume ratio of the particles 11 to at least one of the resin 101 and the resin component 102 in the dispersion medium 10 can be in the range of 1.0:99.0 to 90.0:10.0.

When the volume fraction of the particles 11 is 1.0 volume% or more, it is advantageous for improving the tensile strength of the composite material. When the volume fraction of the particles 11 is 90.0 volume% or less, it is possible to suppress an increase in viscosity during the production of the composite material raw material 1, and to suppress the occurrence of voids in the composite material that cause a decrease in tensile strength. The volume fraction of the particles 11 can be preferably 3.0 volume% or more, more preferably 5.0 volume% or more. The volume fraction of the particles 11 can be preferably 85.0 volume% or less, more preferably 80.0 volume% or less.

The total volume of at least one of the resin 101 and the resin component 102 and the plurality of particles 11 in the dispersion medium 10 means the total volume of the resin 101 and the plurality of particles 11 in the dispersion medium 10 when the dispersion medium 10 does not contain the resin component 102 but contains the resin 101, the total volume of the resin component 102 and the plurality of particles 11 in the dispersion medium 10 when the dispersion medium 10 does not contain the resin 101 but contains the resin component 102, and the total volume of both the resin 101 and the resin component 102 and the plurality of particles 11 in the dispersion medium 10 when the dispersion medium 10 contains both the resin 101 and the resin component 102. In other words, the total volume mentioned above does not include the volume of the solvent (diluent) described above.

The content of the multiple particles 11 contained in the composite material raw material 1 can be 0.5 volume % or more and 50.0 volume % or less. When the content of the multiple particles 11 is 0.5 volume % or more, the amount of the dispersion medium 10 used can be reduced, making it easier to apply to various industrial fields. Furthermore, when the content of the multiple particles 11 is 50.0 volume % or less, the increase in viscosity can be suppressed during the production of the composite material raw material 1, making it easier to apply the mechanical treatment described below that applies shear force.

(Method of manufacturing raw materials for composite materials)
The method for producing a raw material for a composite material according to the present embodiment includes a preparation step and a mechanical treatment step.

The preparation step is a step of preparing a mixture 2 containing a dispersion medium 10 containing at least one of a resin 101 and a resin component 102, and a plurality of particles 11 mixed in the dispersion medium 10, as illustrated in FIG. 2(a).

Conventionally, when manufacturing raw materials for composite materials, first, in a dispersion process, a plurality of dried particles are added to a solvent such as an organic solvent that does not contain resin or resin components, and the plurality of particles in the solvent are dispersed, and then the resin and resin components are mixed through a drying process. This is because, if the resin or resin components are added first in the dispersion process, the solvent that dissolves them is limited, and impurities such as resin and resin components should not be put into the device for dispersing the particles. In contrast, in the above preparation process, a dispersion medium 10 containing at least one of the resin 101 and the resin component 102 and a plurality of particles 11 are intentionally mixed first to prepare a mixture 2 containing them. This is because, even if the particles 11 are mixed first in a resin-free dispersion medium that does not contain the resin 101 and the resin component 102, and the resin 101 or the resin component 102 is added after mechanical processing, the adhesion between the particles 11 and the resin 101 or the resin component 102 is not improved, and a composite material with improved tensile strength cannot be obtained. In other words, in the manufacturing method for composite material raw materials of this embodiment, in order to obtain a composite material with improved tensile strength, resin 101 or resin component 102 is mixed with particles 11 at a stage before mechanical processing is performed to disperse multiple particles 11 in dispersion medium 10.

The mixing of the plurality of particles 11 and the dispersion medium 10 can be carried out using an existing mixing device such as a kneader or a stirrer. For example, when the resin 101 is a curable resin and is liquid, the plurality of particles 11 can be mixed with the liquid curable resin. As described above, the curable resin may be composed of a base agent and a curing agent. In this case, the base agent may be mixed with the plurality of particles 11, or the curing agent may be mixed with the plurality of particles 11. The base agent and the curing agent may be mixed with the plurality of particles 11. When the base agent and the plurality of particles 11 are mixed to prepare the mixture 2, the curing agent can be further mixed after the mechanical treatment. When the curing agent and the plurality of particles 11 are mixed to prepare the mixture 2, the base agent can be further mixed after the mechanical treatment. The liquid curable resin, the base agent, and the curing agent may be diluted with a solvent.

Also, for example, when the resin 101 is a thermoplastic resin, the resin 101 can be dissolved in a solvent and then mixed with a plurality of particles 11.

In the mixture 2, the volume ratio of the multiple particles 11 to the total volume of at least one of the resin 101 and the resin component 102 in the dispersion medium 10 and the multiple particles 11 can be 1.0 volume % or more and 90.0 volume % or less.

When the volume fraction of the particles 11 is 1.0 volume% or more, it is advantageous for improving the tensile strength of the composite material. When the volume fraction of the particles 11 is 90.0 volume% or less, it is possible to suppress an increase in viscosity during the production of the composite material raw material 1, and to suppress the occurrence of voids in the composite material that cause a decrease in tensile strength. The volume fraction of the particles 11 can be preferably 3.0 volume% or more, more preferably 5.0 volume% or more. The volume fraction of the particles 11 can be preferably 85.0 volume% or less, more preferably 80.0 volume% or less.

The content of the particles 11 contained in the mixture 2 can be 0.5 volume % or more and 50.0 volume % or less. When the content of the particles 11 is 0.5 volume % or more, the amount of the dispersion medium 10 used can be reduced, making it easier to apply to various industrial fields. Furthermore, when the content of the particles 11 contained in the mixture 2 is 50.0 volume % or less, the increase in viscosity can be suppressed during the production of the composite material raw material 1, making it easier to apply the mechanical treatment described below in which a shear force is applied.

The mechanical treatment process is a process in which a mechanical treatment is performed on the prepared mixture by applying a shear force to disperse a plurality of particles 11 in the dispersion medium 10, and the surfaces of the particles 11 are coated with a coating layer 12 formed from a resin-derived component derived from at least one of the resin 101 and the resin component 102 contained in the dispersion medium 10. In this mechanical treatment process, the dispersion of the particles 11 in the dispersion medium 10 containing at least one of the resin 101 and the resin component 102, and the surface coating of the particle 11 surface with the resin-derived component derived from at least one of the resin 101 and the resin component 102 contained in the dispersion medium 10 are simultaneously performed.

Any method may be used for the mechanical treatment as long as it can apply a shear force to the mixture 2. For example, a wet jet mill, a rotary disk mill, a high-pressure homogenizer, or the like, which is a mechanical device capable of applying a shear flow while taking into account the movement of the fluid, can be suitably used for the mechanical treatment. In addition, for example, a planetary homogenizer, a high-speed mixer, a three-roll mill, or the like can also be used.

In the mechanical treatment step, the mixture 2 is pressurized to 30 MPa or more and 250 MPa or less, and the shear force generated when the mixture 2 passes through the small holes can be utilized. This configuration ensures that the particles 11 are dispersed in the dispersion medium 10 and that the coating layer 12 is formed on the surface of the particles 11.

The pressure applied to the mixture 2 is preferably 50 MPa or more, more preferably 100 MPa or more, and even more preferably 150 MPa or more. The pressure applied to the mixture 2 is preferably 230 MPa or less, and more preferably 200 MPa or less. The diameter of the small hole is preferably 0.01 mm or more, more preferably 0.05 mm or more, and even more preferably 0.10 mm or more.

The temperature of mixture 2 in the mechanical treatment step may be any temperature at which mixture 2 does not vaporize or solidify. The temperature of mixture 2 may also increase due to the shear force generated when passing through the small holes. In this case, mixture 2 can be appropriately cooled to prevent it from vaporizing.

Figure 3 shows an example of mechanical processing using a wet jet mill. The wet jet mill 5 shown in Figure 3 has a mill body 51 equipped with a plunger 510, a supply section 52 connected to the mill body 51, and a dispersion nozzle section 53 connected to an end of the mill body 51 downstream of the supply section 52. The mill body 51 and the supply section 52 of the wet jet mill 5 are filled with a mixture 2 containing a liquid dispersion medium 10 containing at least one of a resin 101 and a resin component 102 and a plurality of particles 11. In addition, the dispersion nozzle section 53 has a small hole 530 that sharply narrows the flow path through which the mixture 2 flows. The mixture 2 in the mill body 51 is applied with high pressure by the plunger 510. The mixture 2 to which high pressure is applied is guided to the dispersion nozzle section 53 and passes through the small hole 530. When passing through the small holes 530, a shear force acts on the mixture 2, dispersing the particles 11 in the dispersion medium 10 and simultaneously coating the surfaces of the particles 11 with a resin-derived component derived from at least one of the resin 101 and the resin component 102 contained in the dispersion medium 10. The composite material raw material 1 generated by passing through the small holes 530 is collected in a container (not shown) or the like. The diameter of the small holes 530 can be, for example, 0.01 mm or more and 0.50 mm or less.

The mechanical treatment can be carried out once or multiple times. When the mechanical treatment is carried out multiple times, specifically, a mechanical treatment is carried out in which a shear force is applied to the prepared mixture 2, and then the mixture 2 that has been subjected to the mechanical treatment is further subjected to the mechanical treatment once or multiple times. When the mechanical treatment is carried out multiple times, the dispersion of the particles 11 in the dispersion medium 10 and the surface coating of the surfaces of the particles 11 by the resin-derived components can be more sufficiently achieved.

The composite material raw material 1 of this embodiment can be obtained by the manufacturing method of the composite material raw material of this embodiment.

In terms of ensuring an improvement in the tensile strength of the composite material, the composite material raw material 1 obtained by the composite material raw material manufacturing method of this embodiment has a coating ratio, which is defined as the ratio of the coating amount of the coating layer covering the surface of the particles in the composite material raw material to the coating amount of the coating layer covering the surface of the particles in the reference raw material, of preferably 1.3 times or more, more preferably 1.5 times or more, and even more preferably 1.7 times or more. In addition, the above coating ratio is preferably 20.0 times or less, more preferably 17.5 times or less, and even more preferably 15.0 times or less.

The tensile strength of the composite material molded using the composite material raw material 1 obtained by the manufacturing method for composite material raw material of this embodiment is preferably 1.1 times or more, more preferably 1.2 times or more, and even more preferably 1.3 times or more of the tensile strength of the reference composite material molded using the reference raw material, from the viewpoint of ensuring an improvement in the tensile strength of the composite material.

The method for measuring the coating amount of the coating layer and the reference raw materials are as described above in (Raw materials for composite materials).

(Composite materials)
The composite material of the present embodiment is formed using the composite material raw material 1 of the present embodiment. The composite material raw material 1 of the present embodiment may be obtained by the manufacturing method for the composite material raw material of the present embodiment, or may be manufactured by another manufacturing method.

The molding method of the composite material is not particularly limited. For example, when the composite material raw material 1 does not contain a solvent, it can be molded into a desired shape by a known molding method such as injection molding, extrusion molding, press molding, vacuum press molding, etc. Also, for example, when the composite material raw material 1 contains a solvent 103, the solvent 103 can be removed and then molded into a desired shape by the above molding method. Also, for example, when the composite material raw material 1 contains a resin component 102, the remaining resin component required to constitute the resin 101 can be mixed with the composite material raw material 1, and then this can be molded into a desired shape by the above molding method. Also, for example, the particles 11 whose surfaces are covered with the coating layer 12 can be collected from the composite material raw material 1, and the particles 11 and the resin 101 can be mixed and molded into a desired shape by the above molding method.

The tensile modulus and tensile strength of the composite material can be measured as follows. A dumbbell-shaped No. 7 composite material test piece as specified in JIS K6251 is prepared from the composite material raw material 1 from which the solvent has been removed. The tensile modulus and tensile strength can be measured by conducting a tensile test on the prepared composite material test piece using a universal testing machine at room temperature and a tensile speed of 1 mm/min.

The composite materials described above can be used, for example, as structural materials for automobiles, aircraft, etc.

The contents of the description of the composite material raw material, the method for producing the composite material raw material, and the composite material of the present embodiment described above can be appropriately referred to and applied to each other as necessary.

<Experimental Example>
(Sample 1-1)
35.3 g (10.0 cm ³ ) of aluminum oxide powder (Kanto Chemical Co., Ltd., "NanoTek", single particle diameter 52 nm) as ceramic powder, 29.0 g (25.0 cm ³ ) of epoxy resin base material (hereinafter, sometimes referred to as epoxy base material) (Mitsubishi Chemical Co., Ltd., "JER827") as thermosetting resin, 12.4 g (15.4 cm ³ ) of methyl ethyl ketone as a solvent and 354.8 g (449.9 cm ³ ) of ethanol as a diluent were mixed and stirred with a planetary mixer to prepare a liquid mixture (suspension). The single particle diameter of the aluminum oxide powder is the arithmetic average value of the particle diameters of 100 random particles observed by a scanning electron microscope. The measurement method is the same for each sample described later.

The volume ratio of the aluminum oxide powder to the total volume of the epoxy base material and the aluminum oxide powder in the mixture was 28.6% by volume. The content of the aluminum oxide powder in the mixture was 2.0% by volume. The median diameter D50 of the aluminum oxide powder in the mixture, measured using a laser diffraction particle size distribution measuring device (manufactured by Horiba, Ltd., "LA-950V2"), was 8.3 x ¹⁰³ nm. More detailed particle size distribution measurement results and their discussion will be described later. The same applies to the other samples described later.

Next, the prepared mixture was subjected to mechanical processing using a wet jet mill (Advanced Nano Technology, "LSU2540-P20D-AP"). The conditions for mechanical processing using the wet jet mill were: diameter of the small hole in the dispersion nozzle of the wet jet mill: 0.17 mm, pressure: 200 MPa, number of mechanical processing times: 5 times. This is the raw material for the composite material of sample 1-1.

In this experimental example, the dispersion nozzle part described above specifically has a nozzle member 53A having a shape shown in FIG. 4. More specifically, the nozzle member 53A has a first flow path component 531 and a second flow path component 532 laminated on the first flow path component 531. A small hole 530 is formed in the center of the first flow path component 531 so as to be aligned with the pressurization direction of the mixture 2 by the plunger 510 described above. A narrow groove 534 having a width equal to the diameter of the small hole 530, a groove depth equal to the diameter of the small hole 530, and a length equal to the length of the small hole 530 is formed on the surface of the second flow path component 532 on the first flow path component 531 side. The small hole 530 is connected to the center of the long direction of the narrow groove 534. In addition, a pair of large holes 535 is formed in the second flow path component 532 so as to be aligned with the pressurization direction. The diameter of the pair of large holes 535 is larger than the diameter of the small hole 530. One end of each large hole 535 is connected to both ends of the elongated groove 534. The other end of each large hole 535 is open to the surface of the second flow path forming member 532 opposite to the surface on the first flow path forming member 531 side. In the nozzle member 53A, the small hole 530, the elongated groove 534, and the pair of large holes 535 form an intra-nozzle flow path. The mixture 2 flows in from the small hole 530. In this experimental example, the diameter φ ₁ of the small hole 530 was 0.17 mm, the length L ₁ (length of the cylinder) of the small hole 530 was 1.1 mm, the width w of the elongated groove 534 was 0.17 mm, the groove depth d of the elongated groove 534 was 0.17 mm, the length L ₂ in the planar direction of the elongated groove 534 was 1.1 mm, the diameter φ ₂ of the large hole 535 was 0.7 mm, and the length L ₃ (length of the cylinder) of the large hole 535 was 2.5 mm. The nozzle member 53A was made of sintered diamond. The diameter of the flow path through which the mixture 2 flows before the nozzle member 53A was 3.2 mm.

The composite material raw material of the prepared sample 1-1 was centrifuged at 3500 rpm for 60 minutes, and the precipitated aluminum oxide powder was collected. The collected aluminum oxide powder was then washed three times with methyl ethyl ketone and vacuum dried for 8 hours. The mass reduction rate of the dried aluminum oxide powder was measured from 150°C to 600°C at a heating rate of 10°C/min using a thermogravimetric differential thermal analyzer (manufactured by Rigaku Corporation, "TG-8120"). Since a mass reduction was observed even in the aluminum oxide powder after the above washing, it was confirmed that the surfaces of the aluminum oxide particles constituting the aluminum oxide powder were covered with a coating layer formed from a resin-derived component derived from the epoxy base agent. Furthermore, since the resin-derived component could not be removed by the above washing, it can be said that the resin-derived component is adsorbed on the surface of the aluminum oxide particles. More details will be described later using the measurement results using an infrared spectrophotometer. According to the above measurement results of the mass reduction rate, the coating amount (adsorption amount of resin-derived component) of the coating layer covering the surface of the aluminum oxide particles was 1.97 mass%.

As a result of the above, a composite material raw material of sample 1-1 was obtained, which has a dispersion medium containing an epoxy base material and a solvent, a plurality of aluminum oxide particles dispersed in the dispersion medium, and a coating layer formed from a resin-derived component derived from the epoxy base material that covers the surfaces of the aluminum oxide particles.

The composite material raw material of Sample 1-1 had a median diameter D50 of 7.0×10 1 nm of aluminum oxide powder covered with a coating layer, as measured by the above-mentioned laser diffraction particle size distribution measuring device (LA- ^950V2 , manufactured by Horiba, Ltd.). More detailed particle size distribution measurement results and their discussion will be described later. The same applies to the other samples described later.

Next, the solvents in the composite material raw material of Sample 1-1, ethanol and methyl ethyl ketone, were removed by an evaporator. 1.4 g (1.2 cm ³ ) of an epoxy resin curing agent (sometimes called an epoxy curing agent) (manufactured by Mitsubishi Chemical Corporation, "ST11") was added to 5.0 g of the composite material raw material from which the solvent had been removed, and the mixture was stirred by a planetary mixer. The resulting mixture was poured into a silicone mold capable of forming a dumbbell test piece (dumbbell type No. 7 as specified in JIS K6251) to be used in a tensile test, and heated at 80°C for 3 hours to cure the epoxy resin, thereby producing a composite material. The mixing ratio of aluminum oxide powder in the produced composite material was 20.0% by volume.

Then, a tensile test was performed on the prepared composite material using a universal testing machine (Shimadzu Corporation, "EZ-SX") at room temperature and a tensile speed of 1 mm/min to measure the tensile modulus and tensile strength. The tensile modulus of the obtained composite material was 3.07 GPa and the tensile strength was 92.5 MPa.

Next, the microstructure of the fracture surface of the composite material of sample 1-1 after the tensile test was observed using a scanning electron microscope (JEOL Ltd., "JSM-IT300HR"). The results are shown in Figure 4. As shown in Figure 4, it can be seen that aluminum oxide particles are embedded inside the epoxy resin in the composite material of sample 1-1. This result confirmed that the adhesion between the resin and the particles is improved by forming a composite material using the composite material raw material of the present disclosure.

(Sample 1-2)
A composite material raw material and a composite material of Sample 1-2 were prepared in the same manner as Sample 1-1, except that 12.4 g (15.4 cm ³ ) of methyl ethyl ketone and 354.8 g (449.9 ^{cm 3} ) of ethanol were changed to 374.3 g (463.6 cm 3 ) of methyl ethyl ketone.

The volume ratio of the aluminum oxide powder to the total volume of the epoxy base material and the aluminum oxide powder in the mixture was 28.6% by volume. The content of the aluminum oxide powder contained in the mixture was 2.0% by volume. The median diameter D50 of the aluminum oxide powder contained in the mixture was 1.3×10 ⁴ nm. The coating amount (adsorption amount) of the coating layer that covers the surface of the aluminum oxide particles was 0.79 mass%. The median diameter D50 of the aluminum oxide powder whose surface was covered with the coating layer in the composite material raw material of Sample 1-2 was 7.4×10 ¹ nm. The mixing ratio of the aluminum oxide powder in the prepared composite material was 20.0% by volume. The tensile modulus of the prepared composite material was 3.03 GPa and the tensile strength was 85.1 MPa.

(Sample 2)
The composite material raw material and composite material of Sample 2 were prepared in the same manner as Sample 1-1, except that the aluminum oxide powder was changed to 66.3 g (25.0 cm ³ ) of silicon dioxide powder (manufactured by Sakai Chemical Industry Co., Ltd., "Sciqas GRADE 0.25 μm", single particle size 2.6 × 10 ² nm), which is a ceramic powder, and the epoxy base material was changed to 72.5 g (62.5 cm ³ ), 31.0 g (38.4 ^{cm 3 )} , methyl ethyl ketone, and 295.0 g (374.1 cm 3 ), respectively. The composite material raw material of Sample 2 has a dispersion medium containing an epoxy base material and a solvent, a plurality of silicon dioxide particles dispersed in the dispersion medium, and a coating layer formed from a resin-derived component derived from the epoxy base material that covers the surfaces of the silicon dioxide particles.

The volume ratio of silicon dioxide powder to the total volume of the epoxy base material and silicon dioxide powder in the mixture was 28.6% by volume. The content of silicon dioxide powder contained in the mixture was 5.0% by volume. The median diameter D50 of the silicon dioxide powder contained in the mixture was 2.7×10 ² nm. The amount of the coating layer covering the surface of the silicon dioxide particles was 1.53% by mass. The median diameter D50 of the silicon dioxide powder whose surface was covered with the coating layer in the composite material raw material of sample 2 was 1.9×10 ² nm. The mixing ratio of silicon dioxide powder in the prepared composite material was 20.0% by volume. The tensile modulus of the prepared composite material was 2.67 GPa, and the tensile strength was 104.6 MPa.

(Sample 3)
Except for changing the silicon dioxide powder to 90.0 g (25.0 cm ³ ) of magnesium oxide powder, which is a ceramic powder (manufactured by Tateho Corporation, "PUREMAG (registered trademark) FNMG", single particle size 3.9 × 10 ² nm), the composite material raw material and composite material of Sample 3 were prepared in the same manner as Sample 2. The composite material raw material of Sample 3 has a dispersion medium containing an epoxy base agent and a solvent, a plurality of magnesium oxide particles dispersed in the dispersion medium, and a coating layer formed from a resin-derived component derived from the epoxy base agent that covers the surfaces of the magnesium oxide particles.

The volume ratio of the magnesium oxide powder to the total volume of the epoxy base material and the magnesium oxide powder in the mixture was 28.6% by volume. The content of the magnesium oxide powder in the mixture was 5.0% by volume. The median diameter D50 of the magnesium oxide powder in the mixture was 9.5×10 ² nm. The coating amount (adsorption amount) of the coating layer that covers the surface of the magnesium oxide particles was 3.02 mass%. The median diameter D50 of the magnesium oxide powder whose surface was covered with the coating layer in the composite material raw material of sample 2 was 1.9×10 ² nm. The mixing ratio of the magnesium oxide powder in the prepared composite material was 20.0% by volume. The tensile modulus of the prepared composite material was 2.82 GPa, and the tensile strength was 91.1 MPa.

(Sample 1R)
A reference material for sample 1R and a reference composite material using the same were prepared in the same manner as sample 1-1, except that a liquid mixture of aluminum oxide powder, methyl ethyl ketone, and ethanol was subjected to mechanical treatment and then an epoxy base resin was added.

The volume ratio of the aluminum oxide powder to the total volume of the epoxy base material and the aluminum oxide powder in the reference raw material was 28.6 volume %. The content of the aluminum oxide powder contained in the reference raw material was 2.0 volume %. The median diameter D50 of the aluminum oxide powder contained in the reference raw material was 1.0 x 10 ⁴ nm. The coating amount of the coating layer that covers the surface of the aluminum oxide particles was 0.17 mass %. The median diameter D50 of the aluminum oxide powder whose surface was covered with the coating layer in the reference composite material of sample 1R was 7.3 x 10 ¹ nm. The mixing ratio of the aluminum oxide powder in the prepared reference composite material was 20.0 volume %. The tensile modulus of the prepared reference composite material was 2.43 GPa and the tensile strength was 68.5 MPa.

Next, the microstructure of the fracture surface of the reference composite material of sample 1R after the tensile test was observed using the above-mentioned scanning electron microscope. The results are shown in Figure 6. As shown in Figure 6, in the reference composite material of sample 1R, the aluminum oxide particles peeled off from the epoxy resin, and voids of the same shape as the aluminum oxide particles were observed. This is because the resin-derived components that form the coating layer that covers the particle surfaces were not sufficiently adsorbed onto the particle surfaces, resulting in poor adhesion at the interface between the two.

(Sample 2R)
A reference material for Sample 2R and a reference composite material using the same were prepared in the same manner as Sample 2, except that a liquid mixture of silicon dioxide powder, methyl ethyl ketone, and ethanol was subjected to mechanical treatment and then an epoxy base resin was added.

The volume ratio of silicon dioxide powder to the total volume of the epoxy base material and silicon dioxide powder in the reference raw material is 28.6 volume%. The content of silicon dioxide powder contained in the reference raw material is 5.0 volume%. The median diameter D50 of the silicon dioxide powder contained in the reference raw material was 3.2 x 10 ² nm. The amount of the coating layer covering the surface of the silicon dioxide particles was 0.85 mass%. The median diameter D50 of the silicon dioxide powder whose surface was covered with the coating layer in the reference composite material of sample 2R was 2.1 x 10 ² nm. The mixing ratio of silicon dioxide powder in the prepared reference composite material was 20.0 volume%. The tensile modulus of the prepared reference composite material was 2.28 GPa, and the tensile strength was 90.7 MPa.

(Sample 3R)
A reference material for Sample 3R and a reference composite material using this were prepared in the same manner as Sample 3, except that a liquid mixture of magnesium oxide powder, methyl ethyl ketone, and ethanol was subjected to mechanical treatment and then an epoxy base resin was added.

The volume ratio of magnesium oxide powder to the total volume of the epoxy base material and magnesium oxide powder in the reference raw material was 28.6 volume %. The content of magnesium oxide powder contained in the reference raw material was 5.0 volume %. The median diameter D50 of magnesium oxide powder contained in the reference raw material was 6.4 × 10 ³ nm. The coating amount of the coating layer that covers the surface of the magnesium oxide particles was 1.58 mass %. The median diameter D50 of magnesium oxide powder whose surface was covered with a coating layer in the reference composite material of sample 3R was 1.9 × 10 ² nm. The mixing ratio of magnesium oxide powder in the prepared reference composite material was 20.0 volume %. The tensile modulus of elasticity of the prepared reference composite material was 2.57 GPa, and the tensile strength was 58.1 MPa.

(Sample 1-1C)
92.9 g (26.3 Rm ³ ) of aluminum oxide powder, 395 g (500 cm ³ ) of ethanol, and 0.5 g (0.5 cm ³ ) of 0.01N hydrochloric acid were mixed and stirred in a planetary mixer to prepare a liquid mixture (suspension). Next, 16.5 g of 3-glycidoxypropyltriethoxysilane, a silane coupling agent, was added to this mixture, and the mixture was stirred for 2 hours. Next, using a wet jet mill, the mixture to which the silane coupling agent had been added was subjected to mechanical treatment. At this time, the conditions for the mechanical treatment using the wet jet mill were a small hole diameter of 0.17 mm, a pressure of 200 MPa, and the number of mechanical treatments: 10 times. This was used as the raw material for the composite material of Sample 1-1C.

The composite material raw material of the prepared sample 1-1C was centrifuged, and the supernatant was removed. The precipitated aluminum oxide was dried at 120°C for 2 hours. The median diameter D50 of the dried magnesium oxide powder was 7.4 x 10 ¹ nm. 2.74 g of the dried aluminum oxide powder, 2.26 g of the epoxy base agent, and 1.35 g of the epoxy curing agent were mixed and stirred with a planetary mixer. The obtained liquid mixture was poured into a silicone mold capable of forming a dumbbell test piece to be used in a tensile test, and heated at 80°C for 3 hours to cure the epoxy resin, thereby preparing a composite material. The mixture ratio of the aluminum oxide powder in the prepared composite material was 20.0% by volume. The tensile modulus of the obtained composite material was 2.66 GPa, and the tensile strength was 67.9 MPa.

(Sample 1-2C)
The median diameter D50 of the magnesium oxide powder contained in the composite material raw material of sample 1-1C after mechanical treatment and before mixing with the epoxy base was 7.2×10 ¹ nm. The composite material raw material of sample 1-1C was centrifuged to remove the supernatant. 7.46 g of precipitated aluminum oxide was mixed with 14.81 g of methyl ethyl ketone and 4.81 g of the epoxy base, and stirred with a planetary mixer. The resulting liquid mixture was dried under reduced pressure to remove the methyl ethyl ketone. Next, 2.89 g of an epoxy curing agent was added thereto, and the mixture was stirred with a planetary mixer. The resulting liquid mixture was poured into a silicone mold capable of forming a dumbbell test piece to be subjected to a tensile test, and heated at 80° C. for 3 hours to cure the epoxy resin, thereby producing a composite material of sample 1-2C. The mixing ratio of the aluminum oxide powder in the produced composite material was 20.0% by volume. The resulting composite material had a tensile modulus of 2.98 GPa and a tensile strength of 78.2 MPa.

(Sample 1-3C)
The composite material raw material and composite material of Sample 1-3C were prepared in the same manner as Sample 1-2C, except that no mechanical treatment using a wet jet mill was performed. The median diameter D50 of the magnesium oxide powder contained in the composite material raw material of Sample 1-3C before mixing with the epoxy base agent was 6.1 x 10 ³ nm. The mixed ratio of aluminum oxide powder in the composite material of Sample 1-3C prepared was 20.0 volume %. The tensile modulus of elasticity of the obtained composite material was 2.41 GPa, and the tensile strength was 70.6 MPa.

The details of each sample and the results obtained for each sample are summarized in Tables 1 and 2. Figure 7 shows the infrared spectrum of the epoxy base resin. Figure 8 shows the infrared spectra of the aluminum oxide powder itself, the aluminum oxide powders recovered from the composite material raw materials of Samples 1-1 and 1-2, and the aluminum oxide powder recovered from the reference raw material of Sample 1R. Figure 9 shows the infrared spectra of the silicon dioxide powder itself, the silicon dioxide powder recovered from the composite material raw material of Sample 2, and the silicon dioxide powder recovered from the reference raw material of Sample 2R. Figure 10 shows an enlarged view of the infrared spectrum shown in Figure 9. Figure 11 shows the infrared spectra of the magnesium oxide powder itself, the magnesium oxide powder recovered from the composite material raw material of Sample 3, and the magnesium oxide powder recovered from the reference raw material of Sample 3R. The infrared spectrophotometer used to measure the infrared spectra was "Spectrum Two" manufactured by PerkinElmer Japan. In addition, the powders used for infrared spectroscopy measurements were powders recovered from each composite material raw material and reference raw material, washed three times with methyl ethyl ketone, and then vacuum-dried for eight hours.

Figures 12 to 18 show the relationship between particle size (nm) and cumulative (volume %) or frequency (volume %) before and after mechanical processing in the preparation of composite material raw materials for Samples 1-1 to 3 and Samples 1R to 3R. Figures 19 and 20 show the relationship between particle size (nm) and frequency (volume %) in composite material raw materials for Samples 1-1C to 1-3C. Table 3 summarizes these particle size distribution data in numerical form. In Table 3, particle size D10 is the particle size when the volume-based cumulative frequency distribution measured by a laser diffraction particle size distribution analyzer is 10%, and particle size D90 is the particle size when the volume-based cumulative frequency distribution measured by a laser diffraction particle size distribution analyzer is 90%.

The following can be seen from Tables 1 and 2 and Figures 7 to 11. Compared with Sample 1R, Sample 1-1 had a coating amount and tensile strength that increased by 1060% and 35%, respectively. From this result, it can be seen that by performing a mechanical treatment in which a shear force is applied to a predetermined mixture, a part of the resin component in the dispersion medium (epoxy base in this experimental example) is adsorbed onto the surface of the particles (ceramic particles in this experimental example), and the tensile strength of the composite material is improved. Furthermore, Sample 1-2 had a coating amount and tensile strength that increased by 365% and 24%, respectively, compared with Sample 1R. From this result, it was confirmed that the tensile strength of the composite material can be improved even if the type of solvent contained in the mixture to which the mechanical treatment is performed is changed. Furthermore, as shown in Figures 7 and 8, three peaks of resin-derived components were observed in the wavenumber range of 2800 to 3000 cm ^-1 and one each at wavenumbers 1511, 1250, and 1185 cm ^-1 in Sample 1-1. In sample 1-2, a peak of the resin-derived component was observed, although the peak intensity was weaker than that of sample 1-1. From this result, it was revealed that in samples 1-1 and 1-2, the resin-derived component forming the coating layer covering the surface of the particles is adsorbed to the particle surface. On the other hand, in sample 1R, a peak of the resin-derived component was not observed, and it was found that the resin-derived component forming the coating layer covering the surface of the particles is not adsorbed to the particle surface.

Compared to sample 2R, sample 2 had an 80% and 15% increase in the coating amount and tensile strength of the coating layer. Compared to sample 3R, sample 3 had a 91% and 57% increase in the coating amount and tensile strength of the coating layer. These results confirmed that the tensile strength of the composite material can be improved by changing the type of particles contained in the mixture to be mechanically treated. As shown in Figures 7, 9, and 10, peaks of resin-derived components were observed in sample 2 and sample 2R, but no difference was observed between the two. As shown in Figures 7 and 11, peaks of resin-derived components were observed in sample 3 and sample 3R, but sample 3 had a higher peak strength than sample 3R.

In addition, according to Tables 1 and 3, in Samples 1-1 to 3, the median diameter D50 of the multiple particles is smaller after mechanical treatment than before mechanical treatment, which shows that the multiple particles are well dispersed.

In contrast, sample 1-1C was prepared by surface modification of the particles using a silane coupling agent, a conventional method, but the tensile strength was reduced. This is due to the aggregation of particles during drying after the silane coupling reaction. In sample 1-2C, the aggregation of particles was suppressed by not performing a drying operation after the silane coupling reaction, but the increase in tensile strength was only 14% compared to sample 1R. In sample 1-3C, the median diameter D50 was large and the tensile strength hardly increased at all, because no mechanical treatment was performed to apply a shear force to the mixture.

The following can also be seen from Table 3, Figures 19 and 20. It can be seen that the particles are agglomerated in the raw materials used for Samples 1-1C to 1-3C. It can also be seen that while many particles are dispersed in Sample 1-1C, agglomerated particles are present in more than 92% of the area. This is thought to be due to the effects of drying. It can also be seen that Sample 1-2C is in the same state as Sample 1-1C before drying, and the particles are dispersed without agglomeration. It can also be seen that many agglomerated particles are present in Sample 1-3C, as no mechanical processing using a wet jet mill was performed.

The present invention is not limited to the above-described embodiments and experimental examples, and various modifications are possible without departing from the spirit of the invention. Furthermore, the configurations shown in the embodiments and experimental examples can be combined in any manner.

The above-mentioned composite material raw materials and composite materials are also useful as structural components for automobiles, aircraft, sporting goods, etc., and heat dissipation components for electronic devices, etc.

1 Raw material for composite material 10 Dispersion medium 101 Resin 102 Resin component 11 Particles 12 Coating layer 2 Mixture

Claims (16)

A raw material for a composite material used in a particle dispersion reinforced composite material in which particles as a reinforcing material are dispersed in a resin as a matrix (excluding those in which the particles as the reinforcing material are oriented in the resin as the matrix) ,
a dispersion medium containing at least one of the resin serving as the base material of the composite material and a resin component serving as a component for constituting the resin serving as the base material of the composite material (excluding a chain aliphatic epoxy resin having a hydrophilic group, a resin having a fluorene skeleton, and a rubber latex) and a solvent ;
A plurality of particles dispersed in the dispersion medium (excluding, however, cellulose , an adsorbent filler in which a thermoplastic resin is adsorbed on a filler, and nanoparticles in which one or more oligomers derived from two or more polymerizable units are covalently bonded via a coupling agent ),
a coating layer covering the surface of the particle,
the coating layer is formed from a resin-derived component that is derived from at least one of the resin and the resin component contained in the dispersion medium and that is adsorbed on the surface of the particle ,
The coating layer is formed by applying a shear force to a mixture containing the dispersion medium and the particles . 2. The raw material for composite materials according to claim 1, wherein a coating ratio, defined as the ratio of the coating amount of the coating layer covering the surface of the particle in the raw material for composite materials to the coating amount of the coating layer covering the surface of the particle in the reference raw material, is 1.3 times or more.
However, the above reference material is a resin-containing mixture prepared as follows.
A resin-free mixture containing the resin and a resin-free dispersion medium that does not contain the resin component and a plurality of the particles is prepared, and the prepared resin-free mixture is subjected to mechanical treatment using a wet jet mill, and then the resin or the resin component is mixed so that the volume ratio of the plurality of particles is the same as that of the raw material for the composite material to obtain a resin-containing mixture. The conditions for the mechanical treatment using the wet jet mill are: diameter of the small hole of the dispersion nozzle part in the wet jet mill: 0.17 mm, pressure: 200 MPa, and number of times of the mechanical treatment: 5 times. 3. The raw material for a composite material according to claim 1, wherein the particles whose surfaces are covered with the coating layer have a median diameter D50 of 3.0 nm or more and 1.0 x 10 ⁵ nm or less, as measured by a laser diffraction particle size distribution analyzer. 4. The composite material raw material according to claim 1, wherein the particles are at least one type selected from the group consisting of ceramic particles, metal particles, carbon particles, and organic particles. 5. The raw material for a composite material according to claim 4, wherein the ceramic constituting the ceramic particles is at least one selected from the group consisting of aluminum oxide, zinc oxide, magnesium oxide, silicon oxide, titanium oxide, beryllium oxide, boron nitride , aluminum nitride, silicon nitride, silicon carbide, aluminum hydroxide, magnesium hydroxide, zirconium oxide, and yttrium oxide. 5. The composite material raw material according to claim 4 , wherein the metal constituting the metal particles is gold, silver, copper, a platinum group metal, or an alloy thereof. 5. The composite material raw material according to claim 4 , wherein the carbon constituting the carbon particles is at least one selected from the group consisting of carbon black, diamond, graphite, carbon nanotubes, carbon nanofibers, fullerenes, and pulverized carbon fibers. 5. The composite material raw material according to claim 4 , wherein the organic matter constituting the organic particles is at least one selected from the group consisting of chitosan and chitin. 9. The composite material raw material according to claim 1, wherein at least one of the resin and the resin component has a reactive functional group in its molecular structure that reacts with the surface of the particles. 9. The raw material for a composite material according to claim 1, wherein at least one of the resin and the resin component has at least one functional group selected from the group consisting of a hydroxyl group, an aldehyde group, a carboxyl group, a carbonyl group, an amino group, a nitro group, a sulfo group, a ketone group, an acetyl group, an azo group, a vinyl group, an epoxy group, a styryl group, a methacryl group, an acrylic group, an isocyanate group, a mercapto group, and a silyl group in its molecular structure. A raw material for composite materials according to any one of claims 1 to 10, wherein the volume ratio of the plurality of particles to the total volume of at least one of the resin and the resin component in the dispersion medium and the plurality of particles is 1.0 volume % or more and 90.0 volume % or less. The composite material raw material according to claim 1 , wherein the content of the plurality of particles contained in the composite material raw material is 0.5 volume % or more and 50.0 volume % or less. A method for producing a raw material for a composite material used in a particle-dispersion-reinforced composite material in which particles as a reinforcing material are dispersed in a resin as a matrix (excluding those in which the particles as the reinforcing material are oriented in the resin as the matrix) , comprising:
a preparation step of preparing a mixture including a dispersion medium containing at least one of the resin serving as the base material of the composite material and a resin component serving as a component for constituting the resin serving as the base material of the composite material (excluding a chain aliphatic epoxy resin having a hydrophilic group, a resin having a fluorene skeleton, and a rubber latex) and a solvent , and a plurality of particles (excluding cellulose , an adsorbent filler in which a thermoplastic resin is adsorbed on a filler, and nanoparticles in which one or more oligomers derived from two or more polymerizable units are covalently bonded via a coupling agent ) mixed in the dispersion medium;
a mechanical treatment step of dispersing a plurality of the particles in the dispersion medium by applying a shear force to the prepared mixture, and coating the surfaces of the particles with a coating layer formed from a resin-derived component adsorbed on the surfaces of the particles, the resin being derived from at least one of the resin and the resin component contained in the dispersion medium;
The method for producing a raw material for a composite material comprising the steps of: 14. The method for producing a raw material for a composite material according to claim 13 , wherein in the mechanical treatment step, the mixture is pressurized to a pressure of 30 MPa or more and 250 MPa or less, and a shear force generated when the mixture passes through small holes is utilized. The method for producing a raw material for a composite material according to claim 13 or 14, wherein the tensile strength of a composite material molded using the raw material for a composite material obtained by the method for producing a raw material for a composite material is 1.1 times or more the tensile strength of a reference composite material molded using a reference raw material.
However, the above reference material is a resin-containing mixture prepared as follows.
A resin-free mixture containing the resin and a resin-free dispersion medium that does not contain the resin component and a plurality of the particles is prepared, and the prepared resin-free mixture is subjected to mechanical treatment using a wet jet mill, and then the resin or the resin component is mixed so that the volume ratio of the plurality of particles is the same as that of the raw material for the composite material to obtain a resin-containing mixture. The conditions for the mechanical treatment using the wet jet mill are: diameter of the small hole of the dispersion nozzle part in the wet jet mill: 0.17 mm, pressure: 200 MPa, and number of times of the mechanical treatment: 5 times. A composite material formed using the composite material raw material according to any one of claims 1 to 12 .

Images