JP7523943B2 - Particulate material and resin composition - Google Patents

Description

The present invention relates to a particulate material and a resin composition.

Traditionally, inorganic particulate materials have been dispersed in resin materials. The resin composition obtained by dispersing the particulate material has excellent physical properties.

JP 2011-126994 A

In particular, it has been found that resin compositions in which aggregates of nanometer-order primary particles are dispersed in a resin material exhibit high physical properties. Aggregates in particular are sometimes used in fields that require a balance between the properties derived from small primary particles (such as transparency and the smoothness of the resin composition's surface) and the properties derived from the particle size of the aggregates themselves (such as mechanical properties).

However, inorganic substances that make up the particulate material may affect the resin material when they come into contact with the resin material (Patent Document 1). In particular, since aggregates are formed by agglomerating primary particles and have a large specific surface area, the contact area is also large when dispersed in a resin material, and the effect of the particulate material on the resin material is significant. For example, a resin composition in which aggregates are dispersed in a resin material may discolor or decompose over time, and the viscosity of the resin composition before curing may increase over time.

The present invention was completed in consideration of the current situation, and the problem to be solved is to provide a particulate material that has minimal effect on a resin material when dispersed in the resin material, and a resin composition using the particulate material.

In order to solve the above problems, the inventors conducted extensive research and found that the effects on resin materials can be effectively suppressed by attaching a basic substance to the surface of aggregates of primary particles made of inorganic material and having a particle size within a certain range.

The particulate material of the present invention, which solves the above problems, is composed of primary particles made of an inorganic substance, with a specific surface area diameter based on the surface that is connected to the outside being 0.1 nm or more and 80 nm or less, and has aggregates in which the particles are bonded and fused together by dehydration condensation, and a basic substance that adheres to the aggregates.

In particular, it is preferable that the primary particles have a different surface composition from the internal composition. This allows the necessary material to be selected as the internal composition that does not directly contact the resin material, without considering the effect on the resin material. In particular, the surface composition can be selected to be silica, and the internal composition can be selected to contain aluminum elements. In addition, the aggregates can be selected to be composed of silica.

The basic substance may be one or more compounds selected from the group consisting of ammonia, organic amines, silazanes, nitrogen-containing cyclic compounds, and amino group-containing silane compounds. In particular, the basic substance is preferably a hindered amine (HALS).

The amount of the basic substance is preferably 0.01 μmol to 5 μmol in base equivalent based on the surface area of the aggregate.

The volume average particle size of the aggregates is preferably 0.1 μm or more and 500 μm or less.

The primary particles may be composed of boehmite in the interior and silica on the surface, and the dehydration condensation may be carried out by firing at a temperature of more than 250°C. The primary particles may be composed of gamma alumina in the interior and silica on the surface, and the dehydration condensation may be carried out by firing at a temperature of 900°C or higher.

The resin composition of the present invention, which solves the above problems, contains the above-mentioned particulate material and a resin material that disperses the particulate material.

Another resin composition of the present invention that solves the above problems comprises aggregates that are composed of primary particles made of an inorganic material and have a specific surface area diameter of 0.1 nm to 80 nm based on the surface that is connected to the outside, particles are bonded and fused together by dehydration condensation, a basic substance that adheres to the aggregates, and a resin material that disperses the aggregates and the basic substance.

In particular, these resin materials can be made into transparent resin materials to obtain transparent resin compositions. When using transparent resin materials, it is preferable that the light transmittance (400 nm/2 mm) is 80% or more.

The particulate material of the present invention has little effect on the resin material when dispersed in the resin material, and therefore can improve the performance of the resin composition dispersed in the resin material.

1 shows XRD spectra of each sample in the examples. 1 shows XRD spectra of each sample in a comparative example. 1 shows XRD spectra of each sample in the examples. 1 shows XRD spectra of each sample in a comparative example. 1 shows the results of analyzing the XRD spectrum of each sample in the examples and comparative examples. TG-DTA measurement results of each sample in Example 1-0 and Comparative Example 1-0. 1 is a graph showing the change in epoxy equivalent before and after time in Test 7. 1 is a graph showing the change in viscosity before and after time in Test 7. 1 is a graph showing the change in epoxy equivalent before and after time in Test 8. 1 is a graph showing the change in viscosity before and after time in Test 8.

The particulate material of this embodiment and the resin composition using this particulate material will be described in detail below based on the embodiment. The particulate material of this embodiment is a material that has little effect on the resin material when it comes into contact with the resin material. In addition, the properties of the resin composition of this embodiment include high transparency (when a transparent resin material is used as the resin material), low coefficient of thermal expansion (CTE), high gas barrier properties, high elastic modulus, high surface hardness, high compressive strength, and high anti-blocking properties. These properties are achieved by the particulate material contained.

(Particulate material)
The particulate material of the present embodiment has aggregates constituted by primary particles made of an inorganic substance, and a basic substance adhered to the surfaces of the aggregates.

-Agglomerates Agglomerates are formed by binding and fusing primary particles through dehydration condensation to form an aggregate. The particle size of the aggregate is not particularly limited. Since the primary particles are bound and fused together, they are firmly bound together, improving the mechanical strength of the particulate material. Since the strength can be improved as the particle size increases, it is preferable to increase the particle size to the extent that it can be mixed. For example, when the particulate material is applied to a form that may not be physically able to penetrate, such as a thin film, the appropriate particle size distribution of the particulate material is determined so that it can physically penetrate into the form of the part to which it is applied.

Preferable lower limits of the volume average particle size of the aggregates are 0.1 μm, 0.5 μm, 1.0 μm, etc. Preferable upper limits of the volume average particle size are 500 μm, 100 μm, 10 μm, 5 μm, etc. Furthermore, the aggregates can have multiple particle size peaks, such as large and small particle sizes.

The aggregates have a specific surface area diameter of 0.1 nm or more and 80 nm or less, based on the surface that is in communication with the outside air. The specific surface area diameter is a value calculated from the specific surface area (surface area per unit mass) and the specific gravity of the material that constitutes the particulate material, and for secondary particles that are formed as aggregates of primary particles, a value close to the particle size of the primary particles that make up the secondary particles is calculated.

The specific surface area diameter can have lower limits of 0.5 nm, 1 nm, 5 nm, and 10 nm, and upper limits of 30 nm, 50 nm, and 70 nm.

The primary particles constituting the aggregate (hereinafter referred to as "constituent primary particles") are not particularly limited except that they are inorganic. For example, alumina (such as gamma alumina), boehmite, silica, etc. can be used, and particles made of these inorganic substances can also be combined. When combining, they may be combined within a single constituent primary particle, or constituent primary particles of different compositions may be combined.

It can also be made of inorganic materials with different surface and internal compositions. By making the surface and internal compositions different, the material that constitutes the inside of the constituent primary particles is less likely to affect the outside. Also, the influence from the outside is less likely to reach the inside. And the interaction between the surface composition and the internal composition can produce unexpected effects. An example of an unexpected effect is that when gamma alumina is used as the internal composition, making the surface a different material (e.g., silica) affects the phase transition of the gamma alumina crystal. It is known that gamma alumina undergoes phase transition when heated, but it has been confirmed that gamma alumina present in the constituent primary particles whose surfaces are made of a different material does not undergo phase transition even when heated to a temperature at which gamma alumina alone undergoes phase transition. Therefore, the production of the aggregate by dehydration condensation can be carried out at 900°C or higher (preferably 950°C or higher, 1000°C or higher).

In addition, by using boehmite as the internal composition and silica as the surface, the transformation of boehmite to alumina (particularly gamma alumina) due to heating can be suppressed. Therefore, the production of aggregates by dehydration condensation can be carried out at temperatures above 250°C.

Furthermore, it is possible to contain constituent primary particles having other compositions (for example, those consisting of a single composition as a whole). An example of a particle that can be contained as a constituent primary particle is a second particle made of an oxide of an element with an atomic number of 38 or more. A specific example of an element with an atomic number of 38 or more contained in an oxide that is preferably contained therein is zirconium. There are no particular limitations on the particle shape of the constituent primary particles.

It is up to the discretion of the inorganic material to be used for the surface composition and internal composition of the primary particles. Here, it is preferable to select silica as the surface composition. This is because silica is easy to treat with various types of surface treatments, has high physical and chemical stability, and is easy to synthesize. From the perspective of improving optical properties, it is preferable to use amorphous silica.

There are no particular limitations on the ratio of surface to interior. It is preferable for the surface to cover the interior with almost no gaps.

Particulate materials can have a coating layer made of an organic substance on their surface. The coating layer is a layer that covers the surface of the constituent primary particles.

The thickness of the coating layer is not particularly limited, but it is preferable to coat the surface of the particle material with almost no gaps. When a coating layer is provided, it can be interposed between the aggregated primary particles, or the surface of the aggregated primary particles can be coated to coat the primary particles in a state where the primary particles are directly aggregated together. It is preferable that the coating layer is either covalently bonded to the surface of the primary particles or physically bonded by intermolecular force bonds. The organic material constituting the coating layer is preferably a condensation product of a silane compound. If the silane compound is a compound having two or more SiOR groups, a coating layer made of a condensation product can be formed. The condensation product of a silane compound can be produced by condensing the above-mentioned silane compound in contact with the surface of the primary particles (before or after forming the aggregate). The primary particles are composed of an inorganic material and usually have OH groups on their surfaces. Therefore, the above-mentioned silane compound can react with the OH groups present on the surface of the primary particles to form covalent bonds.

Furthermore, when Al ₂ O ₃ is used as the surface or internal composition of the particulate material, it is preferable that the half-width of the peaks present at 2θ of 45° to 49° and 64° to 67° in X-ray diffraction is 0.5° or more. The peak (first peak) in the 2θ range of 45° to 49° is γ-alumina, and the peak (second peak) in the 2θ range of 64° to 67° is γ-alumina. If the half-width of the peaks present in this range is 0.5° or more, α-alumina is not formed, which is preferable.

Furthermore, when boehmite is used as the surface or internal composition of the particle material, it is preferable that the half-width of the peaks at 2θ of 37° to 39° and 71° to 73° in X-ray diffraction is 2.5° or less, and/or the half-width of the peaks at 2θ of 45° to 49° and 64° to 67° is 2.5° or less. Peaks with 2θ in these ranges are boehmite, and it is preferable that the half-width of the peaks in this range is 2.5° or less because boehmite remains.

Basic Substance The basic substance is a Lewis base. The basic substance may be a single compound as it is, or two or more basic substances may be mixed. The basic substance is preferably one containing nitrogen. Examples of basic substances containing nitrogen include ammonia, organic amines, silazanes, nitrogen-containing cyclic compounds, and amino group-containing silane compounds. In particular, the basic substance is preferably a hindered amine. The hindered amine in this specification is a secondary or tertiary amine, and is a compound in which the two carbons bonded to the nitrogen of the secondary or tertiary amine are tertiary carbons. Examples of the hindered amine include tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate; 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate; 2,2,6,6-tetramethyl-4-piperidyl methacrylate; tetrakis(2,2,6,6-tetramethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate; 2,2,6,6-tetramethylpiperidin-4-yl hexadecanoate; and 2,2,6,6-tetramethylpiperidin-4-yl octadecanoate. Of these, 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate is preferred.

The basic substance is attached to the surface of the aggregate. The form of the attached basic substance is not particularly limited, and it can be in the form of particles or a film. If it is in the form of particles, it can be prepared by mixing the particulate basic substance with the aggregate. If it is in the form of a film, it can be formed into a film by dissolving the basic substance in a solvent to prepare a solution, attaching it to the surface of the aggregate, and then removing the solvent by heating or the like.

The amount of the basic substance is not particularly limited, but it is preferable to use an amount that can uniformly cover the surface of the aggregate or an amount that can cover all of the active points present on the surface of the aggregate. As another method for determining the amount, the amount can be set to about 0.001 mg/m ² to 5 mg/m ² based on the surface area of the aggregate. In particular, the lower limit can be 0.005 mg/m ² , 0.01 mg/m ² , 0.02 mg/m ² , 0.03 mg/m ² , or 0.05 mg/m ² , and the upper limit can be 2 mg/m ² , 1 mg/m ² , 0.5 mg/m ² , 0.3 mg/m ² , or 0.25 mg/m ² . These lower and upper limits can be combined arbitrarily.

The basic substance can also be contained in the coating layer described above. When the basic substance is contained in the coating layer, the basic substance is contained in the material that constitutes the coating layer. The material that constitutes the coating layer is preferably a polymer material. The polymer material may be organic, inorganic, or a composite of these.

(Method of Manufacturing Particulate Material)
The method for producing a particulate material of this embodiment is a method that can suitably produce the primary particles having a core-shell structure among the particulate materials of this embodiment described above. For particulate materials other than those having a core-shell structure, primary particles having a single structure are used, and the particulate material can be produced by applying the aggregation process described below to the primary particles.

The method for producing particulate materials includes a dispersion process, a coating process, and other processes that can be selected as necessary. Other processes include an aggregation process, a modification process, and a particle size distribution adjustment process.

The dispersion process is a process in which particles (core particles) having the internal composition are dispersed in a liquid dispersion medium to form a dispersion liquid. Core particles can be obtained by conventional methods. For example, they can be produced by reacting a compound that serves as a precursor of the internal composition. For example, when using boehmite as the internal composition, aluminum hydroxide that has been milled to an appropriate particle size can be used as a precursor, and core particles made of boehmite can be obtained by hydrothermal treatment. Also, aluminum oxide that has been milled to an appropriate particle size can be used as a precursor, and core particles can be obtained by heating it in an acid or alkaline aqueous solution.

The coating process is a process in which a precursor, which is a compound that becomes the surface composition through a reaction, is added to the obtained dispersion liquid to generate the surface composition, thereby forming coated particles in which the surface of the core particles is coated with the surface composition. The ratio of the internal composition to the surface composition can be controlled by the amount of precursor added. Any compound may be used as the precursor. When silica is used as the surface composition, tetraethoxysilane can be used as the precursor. Tetraethoxysilane easily generates silica in the presence of water. For example, the so-called sol-gel method can be used in which tetraethoxysilane is hydrolyzed in an acidic or basic atmosphere.

The aggregation process is a process carried out after the coating process, in which the coated particles obtained in the coating process are heated to aggregate. The resulting aggregates can be pulverized or classified to obtain the required particle size distribution. The heating temperature in the aggregation process is a temperature at which dehydration condensation occurs between the coated particles. Examples include temperatures above 250°C, 450°C or higher, and 500°C or higher. Heating within this temperature range can improve the strength of the obtained particle material.

The modification step is a step carried out after the coating step, in which a silane compound is brought into contact with the surface of the coated particles obtained by the coating step to modify them. When combined with the aggregation step, the modification step can be carried out either before or after the aggregation step. By adding a basic substance during the modification step, it becomes possible to effectively introduce the basic substance to the surface. In addition, in the modification step, a precursor of a polymer compound is introduced together with a basic substance, and then a polymerization reaction is allowed to proceed, thereby introducing the basic substance onto the surface.

(Resin composition: Part 1)
The resin composition of this embodiment has the above-mentioned particulate material and a resin material that disperses the particulate material. When a transparent resin material is used as the resin material, the light transmittance is 80% or more, and particularly 85% or more, and preferably 90% or more. The light transmittance is measured using a test sample having a thickness of 2 mm and a light beam having a wavelength of 400 nm. When a transparent resin material is used, the mixing ratio of the particulate material and the transparent resin material is determined within a range in which the above-mentioned light transmittance can be achieved, and it is preferable to increase the proportion of the particulate material from the viewpoint of improving mechanical properties.

The particle materials that can be used are as described above, so further explanation is omitted. The resin material can be selected from ordinary resin materials such as thermoplastic resins and thermosetting resins. Examples include epoxy resins, polyimides, polycarbonates, polyethylene terephthalate, polybutylene terephthalate, polymethyl methacrylate, vinyl chloride, polypropylene, and polyethylene.

There are no particular limitations on the method for dispersing the particulate material in the resin material. For example, when a thermoplastic resin is used as the resin material, a resin composition can be obtained by mixing and kneading the heated and melted resin material with the particulate material, or by mixing a precursor of the resin material (resin precursor material: monomer, etc.) with the particulate material and then carrying out a polymerization reaction. When the resin material is a thermosetting resin, the precursor of the resin material (monomer, prepolymer, etc.) can be mixed with the particulate material and then cured.

In addition, by using a photopolymerizable material as the resin precursor material, a photopolymerizable resin composition can be provided. The photopolymerizable resin composition can be used to manufacture a molded body by irradiating it with light after being enclosed in a mold, or can be used as a photocurable resin material for modeling with a so-called stereolithography type 3D printer. After polymerization, the resin composition can be expected to have high transparency, a low coefficient of thermal expansion (CTE), and a high elastic modulus.

( Reference: Resin composition: Part 2)
The resin composition of this embodiment has a configuration in which the aggregates, which are the main components of the particulate material of this embodiment, and the basic substance are individually dispersed in the resin material. The resin material described in the above-mentioned resin composition (part 1) can be used as is. Either the aggregates or the basic substance may be dispersed in the resin material first, or both may be dispersed in the resin material at the same time. The types and amounts of the aggregates and basic substance may be used as described in the above-mentioned particulate material and resin composition of this embodiment.

The particulate material, its manufacturing method, and resin composition of the present invention will be described in detail below with reference to examples. First, the manufacturing method of the aggregates, which are the main components of the particulate material of this embodiment, will be described.

(Test 1: Production of aggregates consisting of primary particles with silica as the surface composition and boehmite as the internal composition)
40 parts by mass of isopropanol (IPA) was added to 100 parts by mass of _Aluminosol 10A (containing 10% by mass of _Al2O3 ; minor axis x major axis is 10 nm x 50 nm; equivalent to core particles) manufactured by Kawaken Fine Chemical Co., Ltd., and 10 parts by mass of tetraethoxysilane (TEOS; precursor of silica, which is the surface composition) was added. By adopting this mixing ratio, the mass ratio of boehmite to silica in the aggregate finally obtained is theoretically 78:22.

After reacting for 24 hours at room temperature, the mixture was neutralized with aqueous ammonia to obtain a gel-like precipitate consisting of primary particles. The precipitate was washed with pure water, dried at 160°C for 2 hours, and pulverized in a jet mill to an average particle size of 2 μm or less to obtain the aggregate of Example 1-0.

The aggregate of Example 1-0 was heat-treated at 650°C for 2 hours to obtain the aggregate of Example 1-1. The aggregate of Example 1-2 was obtained by heat-treating at 850°C for 2 hours.

The aggregate of Example 1-1 was heat-treated at 1100°C for 2 hours to obtain the aggregate of Example 1-3. The aggregate of Example 1-1 was heat-treated at 1200°C for 2 hours to obtain the aggregate of Example 1-4. Furthermore, the aggregate of Example 1-0 was heat-treated at 250°C (Example 1-5), 400°C (Example 1-6), and 450°C (Example 1-7) for 2 hours to obtain the aggregate of each Example. The volume average particle size, specific surface area, and refractive index of the aggregates of Examples 1-0 to 1-7 are shown in Table 1. The volume average particle size was measured using a laser diffraction particle size measuring device. The specific surface area was measured by the BET method using nitrogen. The refractive index of the particles was defined by the following method. A number of levels of mixed solvents with different blending ratios of two types of solvents with known refractive indexes were prepared, and when particles were dispersed in these, the refractive index of the mixed liquid at the point where the transmittance was 80% or more (589 nm/10 mm) and the mixed liquid was the most transparent was defined as the refractive index of the particles. In addition, when the transmittance of the mixed liquid is less than 80%, it is defined as optically incompletely opaque. The XRD spectra of each of Examples 1-0 to 1-4 are summarized in Figure 1, and the XRD spectra of each of Examples 1-5 to 1-7 are summarized in Figure 3. The full width at half maximum (FWHM) of the peaks at 2θ of 45° to 49° and 64° to 67° in each Example, calculated from the results of each XRD measurement, is shown in Table 2.

As is clear from Table 1, the aggregate of Example 1-0 shows a refractive index close to the value (approximately 1.60) calculated from the refractive index of boehmite (1.65), the refractive index of silica (1.45 to 1.47), and the mixing ratio of the two (78:22). And the aggregates of Examples 1-1 to 1-4 had a higher refractive index of 1.62 to 1.63 as a result of the boehmite being transformed into gamma alumina by heating at high temperatures.

The XRD measurement results also showed that the half-widths of the peaks at 2θ of 45° to 49° and 64° to 67° were 0.7° or more, and no crystals derived from alpha-alumina were observed. Normally, when boehmite is heated to around 1200°C, it becomes alpha-alumina, but it was found that this can be suppressed by covering the surface with silica.

In addition, the specific surface area diameter in each example remains unchanged at just under 340 ^m2 /g when heated up to 650°C, but increases as the heating temperature increases at higher temperatures (e.g., 850°C or higher). This indicates that sintering of the constituent primary particles is progressing, and it can be inferred that the strength of the aggregate is increasing.

Because boehmite transforms into gamma alumina when heated at high temperatures, we investigated the generation and disappearance of this transformation to determine how the transformation from boehmite to gamma alumina is affected by silica present on the surface.

Specifically, the disappearance of boehmite and the generation of gamma alumina were analyzed from the results of Figures 3 and 4, and the effects of changes in heating temperature and the presence or absence of silica on the surface were examined. For each peak, the peaks at 2θ near 38°, 50°, 64°, and 72° are peaks derived from boehmite, and the peaks at 2θ near 45° and 67° are peaks derived from gamma alumina. When all of the above-mentioned peaks derived from boehmite are present and all of their full widths at half maximum (FWHM) are narrow (for example, 2.5° or less, preferably 0.5° or less), it was determined that boehmite is the main component. In addition, when all of the above-mentioned peaks derived from gamma alumina are present and all of their full widths at half maximum are 0.5° or more (preferably 3.0° or more), it was determined that a considerable amount of gamma alumina was generated. The analysis results are shown in Figure 5.

Each sample in this study was initially composed of only boehmite and contained almost no gamma alumina, so when a peak derived from gamma alumina is observed using the above criteria, it is clear that the transition from boehmite to gamma alumina is progressing. Furthermore, the refractive indexes of these samples were measured and are shown in Figure 5.

As is clear from Figure 5, in Comparative Example 1-5, which was heated at 250°C, the peak derived from gamma alumina was small and boehmite was the main component, but as the heating temperature increased to Comparative Example 1-6, which was heated at 400°C, and Comparative Example 1-7, which was heated at 450°C, it was found that boehmite was transformed into gamma alumina. The refractive index also increased due to the transformation to gamma alumina.

In contrast, in Examples 1-5 to 1-7, in which the surface was formed from silica, even when heated at 250°C (Example 1-5), 400°C (Example 1-6), and 450°C (Embodiment 1-7), boehmite was the main component in all cases, and the generation of gamma alumina was hardly observed. The refractive index also did not show any significant change. Being able to heat at such high temperatures allowed the aggregates to be firmly bonded together while still remaining as boehmite.

For reference, the results of TG-DTA measurements on Example 1-0 and Comparative Example 1-0 are shown in Figure 6. The sample of Example 1-0 showed an endothermic peak near 460°C, indicating that boehmite had transformed into gamma alumina at around this temperature. In contrast, the sample of Comparative Example 1-0 showed an endothermic peak near 420°C, which was 40°C lower than the endothermic peak temperature of Example 1-0, whose surface was made of silica.

(Test 2: Formation of a coating layer made of organic matter: Part 1)
The aggregates of Example 1-2 (dried at 160°C and sintered at 850°C) were placed in a mixer in the amounts shown in Table 3, and then surface treatment was carried out by adding, with stirring, a silane compound solution corresponding to the organic compound amount (amount of silane compound) shown in Table 3. The silane compound solution was a mixed solution of equal amounts of vinyltrimethoxysilane (KBM-1003, manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane compound, IPA, and water.

Then, the mixture was left to mature at room temperature for one day, and then heated at 160°C for two hours to volatilize the liquid components, yielding the composite aggregates of Examples 2-1 to 2-3. This surface treatment resulted in the formation of a coating layer made of an organic substance on the surface of the aggregate.

As is clear from Table 3, it is possible to thicken the coating layer by increasing the amount of silane compound used, and it was found that the refractive index decreases as the coating layer becomes thicker.

(Test 3: Formation of a coating layer made of organic matter: Part 2)
The aggregate of Example 1-0 (only dried at 160°C) was placed in a mixer in the amount shown in Table 4, and then surface treatment was performed by adding, with stirring, a silane compound solution corresponding to the organic compound amount (amount of silane compound) shown in Table 4. The silane compound solution was a mixed solution of equal amounts of vinyltrimethoxysilane (KBM-1003 manufactured by Shin-Etsu Chemical Co., Ltd.) as the silane compound, IPA, and water.

Then, the mixture was left to mature at room temperature for one day, and then heated at 160°C for two hours to volatilize the liquid components, yielding the composite aggregates of Examples 3-1 to 3-3. This surface treatment resulted in the formation of a coating layer made of an organic substance on the surface of the aggregate.

As is clear from Table 4, it is possible to reduce the refractive index by increasing the amount of silane compound added and thickening the organic coating layer.

(Test 4: Formation of a coating layer made of organic matter: Part 3)
Except for changing the amount of TEOS added to the amount shown in Table 5, the aggregates of Examples 4-1, 4-2, and 4-3 were produced in the same manner as in Example 1-2 described above.

The measured refractive index values showed that the refractive index could be controlled by increasing the amount of TEOS added.

Furthermore, 100 parts by mass of each of the aggregates of Examples 1-2, 4-1, 4-2, and 4-3 were reacted with 50 parts by mass of methyltrimethoxysilane (KBM-13, Shin-Etsu Chemical Co., Ltd.) to obtain aggregates of Examples 4-4, 4-5, 4-6, and 4-7, respectively, and the refractive index was measured (Table 6).

As is clear from Table 6, it was found that it is possible to control the refractive index by performing surface treatment with KBM-13. By treating with KBM-13, it was possible to make the refractive index smaller than that of the original aggregate.

(Test 5: When no silica layer is formed on the surface)
Except for not adding TEOS, aggregates were produced in the same manner as in Examples 1-0 to 1-7 of Test 1, and used as aggregates of Comparative Examples 1-0 to 1-7. The aggregates of the Comparative Examples were entirely formed of boehmite or γ-alumina in which boehmite was converted by heating.

The specific surface area, refractive index, and XRD results for the aggregates of the comparative examples are shown in Table 7. The measured XRD spectra for Comparative Examples 1-0, 1-1, 1-3, and 1-4 are shown in Figure 2, and the measured XRD spectra for Comparative Examples 1-5 to 1-7 are shown in Figure 4.

As is clear from Table 7, the absence of a silica layer on the surface caused primary particles to fuse together upon heating, reducing the specific surface area and enlarging the primary particles. This showed that particle enlargement affects light transmittance. In addition, in Comparative Example 1-4, which was heated at 1200°C, the half-widths of the peaks at 2θ of 45° to 49° and 64° to 67° in the spectrum measured by XRD were 0.2°, indicating that gamma alumina had been converted to alpha alumina. As a result, the specific surface area also became smaller, indicating particle enlargement. This shows that the formation of a silica layer on the surface of boehmite can suppress the conversion to alpha alumina due to heating.

(Test 6)
Examples 5-1 to 5-4 were produced by adding colloidal silica together with TEOS in the amount shown in Table 9 when producing the aggregate of Example 4-1. Comparative Example 5-1 was produced by omitting TEOS when producing the aggregate of Example 4-1 and adding colloidal silica in the amount shown in Table 8.

As is clear from the table, the addition of TEOS maintained transparency (allowing the measurement of the refractive index) even when colloidal silica was added. It is presumed that the refractive index could not be measured in Comparative Example 5-1 because pores that were not connected to the outside were created.

(Test 7: Production of particulate material: introduction of basic substance into aggregates of Test Example 6)
100 parts by mass of the aggregate of Example 5-2 was placed in a mixer and stirred, while an equivalent solution of methacryltrimethoxysilane, IPA, and water was added so that the amount of methacryltrimethoxysilane was 30 parts by mass. The mixture was then left to stand at room temperature for one day to mature, and then heated at 105°C for two hours to volatilize the liquid components, preparing a composite aggregate that was used as the particle material (refractive index 1.52) for this test.

The particle material of this test was dispersed in epoxy resin (3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, Daicel Corporation: Celoxide 2021P) as a resin composition at 30 wt % based on the mass of the epoxy resin, and a basic substance (hindered amine, ADEKA Corporation, LA-82) was added in amounts of 0, 0.5, 1, and 5 parts by mass based on 100 parts by mass of the aggregate to prepare a resin composition. These resin compositions (corresponding to the above-mentioned resin composition (part 2)) were used as the test samples for this test.

The test samples in this study were stored at 20°C for one week, and the changes in epoxy equivalent and viscosity were measured from immediately after mixing until 170 hours later (Figures 7 and 8). The sample without added basic substance (0%) showed a large increase in both viscosity and epoxy equivalent, but the sample with added basic substance showed limited increase in both epoxy equivalent and viscosity even after one week.

(Test 8: Corresponding to the above-mentioned resin composition (part 1))
A resin composition was prepared in the same manner as in Test 7, except that a basic substance (hindered amine, LA-82, 1 part by mass assuming that the mass of the aggregate is 100 parts by mass) was added to the aggregate in advance and stirred to form a particulate material in which the basic substance adhered to the surface of the aggregate. The epoxy equivalent change and viscosity change were measured in the same manner as in Test 7. Furthermore, a resin composition was prepared in the same manner as in Test 7, except that 5 parts of hexamethyldisilazane (HMDS) was added as a basic substance instead of the hindered amine, and the epoxy equivalent change and viscosity change were measured in the same manner. When a basic substance was used as in Test Example 7, the increase in epoxy equivalent and viscosity were suppressed. It was also found that the hindered amine was more effective at suppressing the increase in viscosity and epoxy equivalent than HMDS (FIGS. 9 and 10).

(Test 9: Corresponding to the above-mentioned resin composition (part 2))
100 parts by mass of the aggregate of Example 5-2 was placed in a mixer and stirred, while an equivalent solution of phenyltrimethoxysilane, IPA, and water was added so that the amount of phenyltrimethoxysilane was 30 parts by mass. The aggregate was then left to stand at room temperature for one day to mature, and then heated at 160°C for two hours to volatilize the liquid components. The composite aggregate obtained was coated with one part of a hindered amine in the same manner as in Test Example 8 to prepare a particle material for a test sample in the present test example.

The obtained test sample was added to polycarbonate powder in an amount of 25% by mass based on the mass of polycarbonate to prepare a resin composition, which was used as the resin composition of the example of this test. The particle material of the test sample of the example of this test was prepared in the same manner except that no hindered amine was added, which was used as the particle material of the comparative example of this test, and a resin composition was prepared in the same manner to be used as the resin composition of the comparative example of this test.

The resin compositions of the examples and comparative examples were heated at 250°C for 1 hour. The resin composition of the comparative example, which did not contain a hindered amine, changed color to a dark brown, but no coloring was observed in the resin composition of the example, which contained a hindered amine. A resin material consisting of polycarbonate alone was also heated at 250°C for 1 hour, but no coloring was observed, indicating that the presence of the particulate material of the comparative example promotes coloring.

(Others: Applications of the particle material and resin composition of the present embodiment described above)
The following describes application examples of the particle material and resin composition of the present embodiment. In the following description, descriptions limiting the resin material in the resin composition are intended to exemplify preferred resins, and are not intended to limit the use of only those resin materials. In the following examples, the description is limited to transparent resin compositions using transparent resin materials as the resin material.

- By using epoxy resin or silicone resin as the transparent resin material in the transparent resin composition, it can be suitably used in transparent resin compositions for sealing optical devices. Optical devices include LEDs, optical sensors, and light guides. High transparency, low CTE, high gas barrier properties, and high elastic modulus can be expected.

- By using acrylic resin as the transparent resin material in the transparent resin composition, it can be suitably used in dental resin compositions. The dental resin composition can be used in dental restorative materials such as artificial teeth and prostheses. It is expected to have high transparency, low coefficient of thermal expansion (CTE), high elasticity, high surface hardness, high compressive strength, etc.

- By using polyimide, polyester, or epoxy resin as the transparent resin material in the transparent resin composition, it can be suitably used for transparent films. High transparency, high gas barrier properties, high surface hardness, high anti-blocking properties, etc. can be expected. Transparent films can be used in electronic devices such as displays (for example, resin glass for displays and films for display substrates) and for wrapping applications to improve design.

- By including particulate material in the design layer, it can be suitably applied to decorative films for insert molding or in-mold. In addition to the particulate material of this embodiment, pigments, dyes, etc. can be included in the design layer. High transparency, high gas barrier properties, high surface hardness, etc. can be expected. To form the design layer, the particulate material of this embodiment is dispersed in some kind of dispersion medium (for example, the transparent resin material described above). Furthermore, pigments, dyes, metal particles, and metal foil may be included to produce color. An example of a decorative film is one that is integrated with an object by thermal transfer.

- By incorporating particulate materials into an oil-based vehicle, they can be suitably used in oil-based transparent coating compositions. High transparency, low CTE, high surface hardness, etc. can be expected.

- By using transparent resin compositions in optical lenses, high transparency, low CTE, high surface hardness, etc. can be expected.

-An optical adhesive composition made of the transparent resin composition of this embodiment can be provided. A pre-polymerized precursor can be mixed as the transparent resin material contained therein, and the composition can be cured by heat or light when necessary, or the transparent resin composition of this embodiment can be dissolved in an appropriate solvent and cured by evaporating the solvent. High transparency and low CTE can be achieved. The optical adhesive composition can be suitably used for bonding optical components. It can also be used in optical displays, etc.

- A resin glass molded body can be provided that is made from the transparent resin composition of this embodiment. It is possible to achieve high transparency, low CTE, high elastic modulus, high surface hardness, etc.

- A mobile communication terminal housing made of the transparent resin composition of this embodiment can be provided. This housing has millimeter wave transparency. Because the particle size of the primary particles of the particulate material contained is small, absorption of millimeter waves can also be reduced. High-speed communication can be achieved by adopting a portable information device or the like as a mobile communication terminal. In addition, millimeter wave radar for moving objects such as automobiles can also be adopted as a mobile communication terminal. High transparency, surface hardness, etc. can be achieved.

・For a molded body molded from the transparent resin composition of this embodiment, by making it have a gradient structure in which the content of the particulate material of this embodiment increases toward the surface, high transparency, low CTE, high surface hardness, etc. can be expected. Although there is no particular limitation on the method for realizing the gradient structure, an example is a method in which a molded body is made from a material with a different content of particulate material (using in-mold molding or the like to make the content of particulate material different for each part of the molded body). Either a thermosetting resin or a thermoplastic resin can be used for the resin composition. There is no particular limitation on the molded body, and it can be used for the above-mentioned applications. By making the surface contain a large amount of particulate material, the surface properties can be improved by the particulate material. Since the particulate material is concentrated on the surface, it is particularly expected that the gas barrier properties and surface hardness will be improved.

- A concave-convex structure containing a particulate material can be formed on the surface of a molded product formed from the transparent resin composition of this embodiment. When a molded product is formed using a mold or the like, this concave-convex structure can be formed by transferring the concave-convex structure formed on the surface inside the mold, or by precipitating a particulate material on the surface. The concave-convex structure contains a particle structure. High transparency, low CTE, high gas barrier properties, high surface hardness, high anti-blocking properties, etc. can be expected. Either a thermosetting resin or a thermoplastic resin can be used for the resin composition. There is no particular limitation on the molded product, and it can be used for the applications described above.

Claims (9)

an aggregate having a specific surface area diameter based on a surface communicating with the outside of the material of 0.1 nm to 80 nm, which is composed of primary particles made of an inorganic substance and in which the particles are bonded and fused together by dehydration condensation;
a basic substance comprising a hindered amine attached to the aggregate;
having
The primary particles have a surface composition different from an internal composition,
A particulate material in which the interior is composed of boehmite and the surface is composed of silica, or the interior is composed of gamma alumina and the surface is composed of silica . an aggregate having a specific surface area diameter based on a surface communicating with the outside of the material of 0.1 nm to 80 nm, which is composed of primary particles made of an inorganic substance and in which the particles are bonded and fused together by dehydration condensation;
a basic substance comprising a hindered amine attached to the aggregate;
having
The aggregates are particulate material composed of silica . 3. The particulate material according to claim 1 , wherein the amount of the basic substance is 0.01 μmol to 5 μmol in terms of base equivalent based on the surface area of the aggregate. The particulate material according to any one of claims 1 to 3 , wherein the volume average particle size of the aggregates is 0.1 µm or more and 500 µm or less. A method for producing a particulate material according to claim 1 and any one of claims 3 to 4 which directly or indirectly derives from claim 1, comprising:
The primary particles are composed of boehmite in the interior and silica on the surface,
The method for producing a particulate material, wherein the dehydration and condensation is carried out by firing at a temperature of more than 250°C. A method for producing a particulate material according to claim 1 and any one of claims 3 to 4 which directly or indirectly derives from claim 1, comprising:
the primary particles are composed of γ-alumina in the interior and silica on the surface;
The method for producing a particulate material, wherein the dehydration and condensation is carried out by firing at 900° C. or higher. A particulate material according to any one of claims 1 to 4 ,
A resin material in which the particulate material is dispersed;
having
The resin composition , wherein the hindered amine is unevenly distributed in the vicinity of the surface of the particulate material . The resin composition according to claim 7 , wherein the resin material is a transparent resin material. The resin composition according to claim 8 , having a light transmittance (400 nm/2 mm) of 80% or more.

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