Alumina particle material, method for producing same, and organic composition

Abstract

The present invention addresses the problem of providing: an alumina particle material from which a resin composition having excellent electrical characteristics can be obtained; and a method for producing the alumina particle material. It was found that the electrical characteristics of an alumina particle material can be improved by reducing the moisture contained in the alumina particle material, in particular the moisture present on the surface, and the following invention was completed. A method for producing an alumina particle material according to the present invention comprises: a starting material particle material preparation step for preparing a starting material particle material having alumina as a main component; a heating step for preparing a dried starting material particle material by holding the starting material particle material at 100 DEG C or more for 5 minutes or more; and a surface treatment step for treating, with a surface treatment agent, the dried starting material particle material in a state after the heating step and in which the adsorption of moisture to the surface is less than before the heating step, so as to mask at least some of the OH groups present on the surface. The alumina constituting the alumina particle material has an OH group on the surface. Since a plurality of water molecules are adsorbed on the OH group, the adsorbed water is removed by a heating step.

Description

Technical Field

[0001] The present invention relates to an alumina particle material, a method for manufacturing the same, and an organic composition. Background Art

[0002] The alumina particle material is used as a resin composition filled into a resin material in applications such as sealing materials and thermal conductivity materials (TIM) for electronic materials. For the purpose of improving the affinity with the resin, surface treatment is usually performed (Patent Documents 1 and 2).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: International Publication No. 2016 / 017637

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2020-066678 Summary of the Invention

[0007] With the improvement of the performance of electronic devices in recent years, resin compositions for electronic materials are also required to have excellent electrical properties.

[0008] The present invention has been completed in view of the above actual situation, and the problem to be solved is to provide an alumina particle material, a method for manufacturing the same, and an organic composition obtained by dispersing the alumina particle material in an organic substance, which can obtain a resin composition having excellent electrical properties.

[0009] For the purpose of solving the above problems, the present inventors conducted in-depth research and found that by reducing the moisture content of the alumina particle material, particularly the moisture present on the surface, the electrical properties of the alumina particle material can be improved, and the following invention was completed.

[0010] (1) The method for manufacturing an alumina particle material of the present invention for solving the above problems includes:

[0011] a raw material particle material preparation step of preparing a raw material particle material mainly composed of alumina;

[0012] a heating step of preparing a dried raw material particle material by holding the above raw material particle material at 100°C to 300°C for 5 minutes or more; and

[0013] a surface treatment step of treating the dried raw material particle material in a state where the moisture adsorbed on the surface is less than that before the heating step with a surface treatment agent to mask at least a part of the OH groups present on the surface.

[0014] The alumina that constitutes the alumina particle material has OH groups on its surface. It is known that since multiple water molecules are adsorbed on these OH groups, even if surface treatment is performed using a surface treatment agent, sufficient surface treatment cannot be achieved.

[0015] That is, multiple water molecules present on the surface of the alumina hinder the direct reaction between the surface treatment agent and the OH groups present on the surface of the alumina. Therefore, immediately after surface treatment using a surface treatment agent, the amount of OH groups on the surface of the particles is small, and the value of the dielectric loss tangent can be maintained at a low level. However, the surface treatment agent that is not directly bonded to the surface of the alumina falls off over time, and OH groups are regenerated on its surface, and a tendency for the dielectric loss tangent to increase is confirmed.

[0016] As an inorganic material used in a resin composition for electronic materials in the same manner as alumina, silica is known. However, the amount of water molecule adsorption on the OH groups present on the surface of silica is less than that on the OH groups present on the surface of alumina. Therefore, the particle material composed of silica can be easily modified by surface treatment. The detailed content will be described in the examples.

[0017] Therefore, in the alumina particle material, by removing the water molecules adsorbed before surface treatment and performing surface treatment before the water molecules are re-adsorbed, the effect of surface treatment can be fully exerted.

[0018] (2) The alumina particle material of the present invention that solves the above problems is a spherical particle material mainly composed of alumina,

[0019] The volume average particle diameter is 2.0 μm or less (preferably less than 0.5 μm), the specific surface area is 1.5 m 2 / g or more,

[0020] The amount of water generated when heated from 25 °C to 200 °C is 700 ppm or less on a mass basis,

[0021] The dielectric loss tangent is 0.0075 or less,

[0022] and it has organic functional groups on its surface.

[0023] (3) The organic composition that solves the above problems has:

[0024] The alumina particle material described in the above (1), and

[0025] A dispersion medium composed of at least one of an organic resin material or an organic solvent in which the above alumina particle material is dispersed.

[0026] According to the manufacturing method of the alumina particle material of the present invention, with the above-described constitution, it is possible to remove the adsorbed water that is usually present in a large amount on the surface of alumina, and it is possible to introduce the required organic functional groups. In addition, by performing surface treatment in a state where there is no adsorbed water, even if it comes into contact with moisture thereafter (including the case of being exposed to a high-humidity atmosphere), since there are few free OH groups, the adsorption of moisture can also be suppressed.

[0027] The alumina particle material of the present invention has the required organic functional groups introduced on the surface and has the required functionality. In particular, since the surface treatment is performed in a state where the amount of adsorbed water is small, the adsorption of moisture on the surface thereafter is suppressed. Furthermore, when the alumina particle material is filled into a resin material and used as a resin composition, by removing the moisture adsorbed on the alumina particle material, the effect of suppressing the influence on the resin material can also be exerted. As the influence on the resin material, there can be mentioned the influence on curing in the case where a resin precursor before curing is used as the resin material. Detailed Description of the Embodiment

[0028] Based on the embodiment, the alumina particle material of the present invention, its manufacturing method, and the organic composition will be described in detail. The use of the alumina particle material of the present embodiment is not particularly limited, and it is preferably used as a filler dispersed in a resin material and filled into a resin composition for electronic materials. As the resin material, there is no particular limitation, and examples thereof include epoxy resins, polyurethane resins, silicone resins, and the like.

[0029] The alumina, which is the main constituent element of the alumina particle material of the present embodiment, has high thermal conductivity and can be applied to fillers for resin compositions used in thermal conductive materials (TIM), sealing materials, underfills, and the like. In this specification, even if the numerical values cited are not particularly described, ranges can be set with these numerical values as the upper limit value or the lower limit value. In this case, the range can be a range including the numerical value, or a range not including the numerical value. Furthermore, other arbitrary numerical values can also be used to set ranges having an upper limit and a lower limit. In this case, the ranges can be set in a form that independently includes or does not include the set upper limit and lower limit.

[0030] (Alumina Particle Material)

[0031] The alumina particle material of the present embodiment has alumina as the main component. Having alumina as the main component means containing 50% or more of alumina on a mass basis, and preferably 75% or more, 90% or more, 95% or more, 99% or more, and being composed of alumina except for unavoidable impurities, etc.

[0032] The alumina preferably has an α - conversion rate of less than 90%. As the upper limit value of the α - conversion rate, 85%, 80%, 75%, 70%, etc. can be cited. When alumina is exposed to high temperatures, the α - conversion rate increases. For example, by exposure to 1300 °C or higher, the α - conversion rate becomes 90% or higher. The alumina particle material of the present embodiment can be manufactured by a manufacturing method including a heating step as described later. As its heating temperature, it is a condition where the α - conversion rate hardly increases, so it can have an α - conversion rate within the above range.

[0033] As materials that can be contained in addition to alumina, metal oxides such as silica, titanium dioxide, and zirconia can be exemplified. They can be contained as crystals different from alumina or can be contained in the crystals of alumina. Further, it can also be a mixture of a particle material composed of alumina and a particle material composed of other materials.

[0034] The alumina particle material of the present embodiment has an organic functional group on its surface. Examples of the organic functional group include vinyl, amino, alkoxy, phenyl, aminophenyl, epoxy, methacryloyl, acryloyl, styryl, alkyl, and isocyanate groups. These organic functional groups are bonded to the surface of alumina.

[0035] Specifically, it can be directly bonded to the Al atom or oxygen atom constituting alumina, or can also be bonded to the Al atom or oxygen atom constituting alumina via a silicon atom, titanium atom, aluminum atom, etc. For example, it can be introduced by reacting a silane coupling agent (silane compound), a titanium coupling agent (titanium compound), or an aluminate coupling agent (aluminum compound) having an organic functional group to be introduced.

[0036] In the case of introduction via a silane compound, it is expected to introduce an organic functional group to the Al atom constituting alumina using a chemical structure such as (Al - O - Si - organic functional group). In the case of introduction via a titanium compound, it is expected to introduce an organic functional group to the Al atom constituting alumina using a chemical structure such as (Al - O - Ti - organic functional group).

[0037] In the above chemical structure, the part of (Si - organic functional group) can also adopt a structure such as (Si - linker - organic functional group). As the linker, there is no particular limitation, and an alkylene group having about 1 to 6 carbon atoms or an organosiloxanyl group having a methyl or ethyl group can be adopted.

[0038] In addition to the surface treatment using a silane coupling agent, a silylating agent (silane compound) can also be used to introduce a silyl group. Multiple silane compounds such as silane coupling agents and silylating agents can be used.

[0039] The introduced amount of the organic functional group is not particularly limited. Taking the surface area of the alumina particle material (the value measured by the BET method using nitrogen; the same applies hereinafter) as a reference, it can be 0.3 per nm 2 ~2.0 per nm 2 or so. As the lower limit value, 0.3 per nm 2 , 0.4 per nm 2 can be adopted. As the upper limit value, 1.0 per nm 2 , 1.5 per nm 2 , 2.0 per nm 2 can be adopted. These upper limit values and lower limit values can be arbitrarily combined.

[0040] The alumina particle material of this embodiment is preferably spherical. In particular, the roundness can be 0.8 or more, 0.9 or more, 0.95 or more, 0.99 or more. The roundness is calculated from the area and perimeter of the observed particles by taking a photograph using SEM, and (roundness) = {4π×(area)÷(perimeter) 2}. The closer it is to 1, the closer it is to a true sphere. Specifically, the average value measured for 100 or more particles using image processing software (Asahi Kasei Engineering Co., Ltd.: A Image King) is adopted.

[0041] There are active points on the surface of the alumina particle material that react with the epoxy groups present in the epoxy resin material, and the amount of these reaction points can be evaluated by the epoxy equivalent. It is preferably that the reaction between the surface of the alumina particle material and the epoxy resin material does not occur as much as possible. Specifically, the epoxy equivalent of the alumina particle material of this embodiment is preferably 175 (g / eq) or less, more preferably 170 (g / eq) or less, and further preferably 165 (g / eq) or less.

[0042] The alumina particle material of this embodiment is different from the existing alumina particle materials in that the reduction of the reaction points is sufficiently carried out through surface treatment with a surface treatment agent. That is, by performing surface treatment in a state where the moisture adsorbed on the surface is less, even if the materials from the surface treatment agent present on the surface are of the same degree, the degree of reduction of the reaction points is different.

[0043] In particular, the increase rate of the epoxy equivalent after being held at 110 °C for 12 hours is preferably 8.0% or less. In particular, as the preferred upper limit value of the increase rate of the epoxy equivalent, 7.5%, 6.0%, 5.0%, 4.0%, 3.0%, 2.5%, 2.0%, 1.5%, 1.0% can be cited. The heating conditions and the measurement method of the epoxy equivalent are carried out by the methods adopted in the following examples.

[0044] The alumina particle material of this embodiment satisfies the requirement of the following (a). For reference, an alumina particle material of (b) with different volume average particle sizes is shown.

[0045] (a) The volume average particle size is 2.0 μm or less (preferably less than 0.5 μm), the specific surface area is 1.5 m 2 / g or more, the amount of water generated when heated from 25 °C to 200 °C is 700 ppm or less based on mass, and the dielectric loss tangent is 0.0075 or less. As the upper limit value of the volume average particle size, 1.8 μm, 1.6 μm, 1.5 μm, 1.4 μm, 1.3 μm, 1.2 μm, 1.1 μm, 1.0 μm, 0.9 μm, 0.8 μm, 0.7 μm, 0.6 μm, 0.49 μm, 0.48 μm, 0.47 μm, 0.45 μm, 0.44 μm, 0.43 μm, 0.42 μm, 0.41 μm, 0.40 μm can also be adopted. If the particle size is small, there is a tendency for the specific surface area to become larger, and the influence of the water adsorbed on the surface becomes larger.

[0046] In this specification, unless otherwise specified, the specific surface area is a value measured by the BET method using nitrogen. In this specification, unless otherwise specified, the amount of water is a value obtained by measuring the water generated when the weighed sample is heated from 25 °C to 200 °C using a device of model CA310 manufactured by Mitsubishi Chemical Analytech Co., Ltd. and by the Karl Fischer coulometric titration method.

[0047] As the upper limit of the amount of water, 650 ppm, 600 ppm, 550 ppm, 500 ppm can be cited. As the preferred upper limit value of the dielectric loss tangent, 0.0050, 0.0040, 0.0030, 0.0025 can be exemplified. When the volume average particle size is small, the rate of re-adsorption of water becomes high, and it is difficult to obtain an alumina particle material in which a surface treatment agent reacts with a water amount below the water amount specified in this embodiment unless an operation for reducing the water amount is performed.

[0048] (b) The volume average particle size is 2.0 μm to 20 μm, the specific surface area is 0.2 m 2 / g or more and less than 1.5 m 2 / g, the amount of water generated when heated from 25 °C to 200 °C is 200 ppm or less based on mass, and the dielectric loss tangent is 0.0020 or less.

[0049] As the upper limit of the moisture content, 190 ppm, 150 ppm, 130 ppm, 110 ppm, 80 ppm, and 60 ppm can be cited. As the preferred upper limit value of the dielectric loss tangent, 0.0015, 0.0012, and 0.0010 can be exemplified.

[0050] (Manufacturing method of alumina particle material)

[0051] The manufacturing method of the alumina particle material of the present embodiment has a raw material particle material preparation step, a heating step, a surface treatment step, and other optional steps as needed.

[0052] · Raw material particle material preparation step

[0053] The raw material particle material preparation step is a step of preparing a raw material particle material having alumina as a main component. The specific method for preparing the alumina particle material is not limited, and examples include the VMC method in which a powder material composed of metallic aluminum is introduced into a high-temperature oxidation atmosphere, detonated, and then rapidly cooled to prepare a spherical raw material particle material composed of alumina; and the melting method in which a particle material composed of alumina is introduced into a high-temperature atmosphere, heated and melted, and then rapidly cooled to form a spherical shape.

[0054] In the VMC method, a metal element corresponding to a metal oxide contained in addition to alumina can be contained in the aluminum used as a raw material. In the melting method, the material constituting the alumina particle material can be used as the material for the melting method. In addition, in the melting method, granulation of small particles can be performed to form a granulated product having a large particle size, and the granulated product can be melted to form a raw material particle material. The raw material particle material is preferably supplied to the subsequent heating step without contacting moisture. In addition, before the heating step, the same treatment as the surface treatment performed in the subsequent surface treatment step can be performed or not.

[0055] · Heating step

[0056] The heating process is a process of preparing dry raw material particles by maintaining the raw material particle material at 100 °C or higher for 5 minutes or longer. By heating to 100 °C or higher, the adsorbed water present on the surface of the raw material particle material can be removed. The lower limit value of the heating temperature can be 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, 200 °C, 400 °C, 800 °C, etc. As the upper limit value, the temperature at which the raw material particle material does not melt, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, 250 °C, 260 °C, 270 °C, 280 °C, 290 °C, 300 °C, 310 °C, 320 °C, 330 °C, 340 °C, 350 °C, 360 °C, 370 °C, 380 °C, 390 °C, 400 °C, 500 °C, 600 °C, 700 °C, 800 °C, 900 °C, 1000 °C, etc. can be adopted. These upper limit values and lower limit values can be arbitrarily combined. As the heating temperature, if it is 200 °C or higher, removal of bound water can also be expected. Furthermore, if it exceeds 400 °C, a dehydration reaction from the OH groups present on the surface of alumina can be expected.

[0057] The heating temperature can be constant, or it can be raised or lowered. The raising or lowering of the temperature can be carried out gradually or stepwise.

[0058] In order to achieve sufficient removal of adsorbed water, as the lower limit value of the heating time, 5 minutes, 10 minutes, 20 minutes, 30 minutes, etc. can be adopted. The longer the time, the more useful it is for the removal of adsorbed water, and by shortening the time, the cost required for heating can be suppressed.

[0059] In the heating process, it is preferred to carry out until the amount of water per 1 g converted to the amount of OH groups is 5×10 18 or less. In particular, the upper limit of the amount of OH groups is preferably 1×10 18 、2×10 18 、5×10 18 or less. The measurement of the amount of OH groups is calculated based on the amount of water (a) after the heating process, the amount of water (b) before the heating process, and the amount of hydroxyl groups (c) at that time, using (amount of OH groups per 1 g) = c×(a / b).

[0060] During heating, it is preferred to suppress the inflow of moisture from the outside or heat in a closed treatment tank. As heating methods, methods such as heating the treatment tank, etc. from the outside, introducing heated dry gas (dry air, etc.) into the treatment tank, and irradiating microwaves, etc. can be exemplified. In addition, during heating, the raw material particle material can be depressurized or dry gas can be supplied. Furthermore, in order to effectively remove the adsorbed water after desorption, during heating, it is preferred to stir the raw material particle material or form a fluidized bed.

[0061] ·Surface treatment process

[0062] The surface treatment process is a process of masking at least a part of the OH groups present on the surface by subjecting the dry raw material particle material to surface treatment using a surface treatment agent. It is assumed that the OH groups present on the surface are directly bonded to the Al atoms of the alumina constituting the alumina particle material.

[0063] After heating in the heating process, surface treatment is carried out until the adsorption of moisture on the surface reaches saturation. If moisture is adsorbed on the surface, it is difficult to carry out sufficient surface treatment. Therefore, by carrying out surface treatment before the moisture content returns to before the heating process, an effect higher than the surface treatment without carrying out the heating process can be exerted.

[0064] Furthermore, the surface treatment is preferably carried out within a time when the temperature of the dry raw material particle material is not lower than 80°C. Since the re-adsorption of moisture on the surface of the dry raw material particle material occurs as the temperature decreases, the surface treatment is carried out before the temperature decreases.

[0065] In addition, it is preferably carried out after cooling in a space with a limited amount of moisture present after heating in the heating process. Here, a limited amount of moisture present means that even if all the moisture present is adsorbed, the moisture content before the heating process cannot be reached, or the moisture content before the heating process cannot be reached when cooling is carried out in this space. It is particularly preferred that even if all the moisture present is adsorbed, it is below the upper limit of the above-mentioned OH groups. Furthermore, even when the moisture content is more than the upper limit of the above-mentioned OH groups, the surface treatment can be carried out before the amount of moisture exceeding the upper limit value is adsorbed. Furthermore, in addition to the operation of carrying out surface treatment after the above-mentioned heating process and before the temperature is lowered, it can also be carried out by cooling while maintaining in a space with a limited amount of moisture present.

[0066] In the surface treatment process, the residual OH groups are masked by reacting a surface treatment agent with the OH groups. In this case, since the amount of water adsorbed on the surface can be reduced, it is possible to inhibit the interposition of water molecules between alumina and the surface treatment agent as in the past, and the amount of direct reaction between the surface treatment agent and the surface of alumina can be increased. As the surface treatment agent, a surface treatment agent that reacts with OH groups can be used. For example, silane compounds such as silane coupling agents and titanium compounds such as titanium coupling agents can be exemplified. The surface treatment agent preferably has appropriate organic functional groups. As the organic functional groups, since the functional groups described in the alumina particle material column of the above-described present embodiment can be used, the description thereof is omitted. As specific surface treatment agents, silane compounds (silane coupling agents), titanium compounds (titanium coupling agents), and hexamethyldisilazane (HMDS) having these organic functional groups in their structures can be exemplified. For the silane compound and the titanium compound, the organic functional group may be directly bonded to the silicon atom or the titanium atom, or may be bonded via the above-described linker.

[0067] The amount of the surface treatment agent is not particularly limited, and is preferably an amount that can react with all OH groups present on the surface of the dried raw material particle material. For example, based on the mass of the dried raw material particle material, an amount of about 0.1% to 3.0% can be cited. As the lower limit value, 0.2%, 0.3%, and 0.4% can be exemplified, and as the upper limit value, 2% and 2.5% can be exemplified. The upper limit value and the lower limit value can be arbitrarily combined.

[0068] Furthermore, the surface treatment can be performed using multiple surface treatment agents. In the case of using multiple surface treatment agents, the multiple surface treatment agents can be divided into one type or two or more types, and made to react sequentially or made to react all at once.

[0069] The surface treatment process is a process of surface-treating the dried raw material particle material in a state where adsorbed water is slightly removed by the heating process. After the heating process, as the temperature decreases, the water contained in the atmosphere is adsorbed on the surface of the dried raw material particle material. In addition, after the heating process, as time passes, the water present in the atmosphere is re-adsorbed on the dried raw material particle material. Therefore, it is preferable to perform the surface treatment as quickly as possible after the heating process.

[0070] In the surface treatment process, it is preferable to select any one of performing the surface treatment before the temperature decreases, or making the amount of water contained in the atmosphere lower than that in the environment to reduce the adsorption rate on the surface when the temperature decreases, and quickly performing the surface treatment before the water is adsorbed. In addition, it is preferable to perform the surface treatment in a state where the amount of water contained in the atmosphere is lower than that in the environment. As a method of making the amount of water contained in the atmosphere lower than that in the environment, it can be achieved by using a part or all of a purified gas with a small amount of water, or using dehumidified air, or performing decompression.

[0071] The surface treatment agent contacts the surface of the dry raw material particle material by an appropriate method. It can be directly mixed with the dry raw material particle material or mixed in a state of being dissolved in an appropriate solvent. In the case of compounds that require hydrolysis such as silane compounds and titanium compounds as the surface treatment agent, hydrolysis can be carried out by the moisture present in the atmosphere or the moisture present on the surface of the dry raw material particle material. In the case of being dissolved in a solvent, hydrolysis can be carried out by the moisture contained in the solvent. When mixing the surface treatment agent, it can be carried out while stirring the dry raw material particle material.

[0072] After the surface treatment, although not particularly limited, heating can be carried out. For example, heating can be carried out while mixing the surface treatment agent, or heating can be carried out after mixing. As the heating temperature, 80 °C or higher, 100 °C or higher, 120 °C or higher, 140 °C or higher, 160 °C or higher, etc. can be selected.

[0073] · Other processes

[0074] After the surface treatment process, it is preferably not in contact with water. In addition, even if it is in contact with water, it is preferably followed by a reheating process of reheating to 100 °C or higher again. As the heating temperature of the reheating process, 120 °C, 150 °C, 200 °C can be exemplified.

[0075] It is preferable to have a crushing process of crushing the obtained particles after the surface treatment process or the heating process. In the crushing process, the pulverization operation of a jet mill or the like can be used.

[0076] (Organic composition)

[0077] The organic composition of the present embodiment has the alumina particle material of the present embodiment described above and a dispersion medium for dispersing the alumina particle material. The blending amount of the alumina particle material in the organic composition of the present embodiment is not particularly limited. As the lower limit of the blending amount, based on the total mass, 60%, 70%, 80%, 90% can be adopted.

[0078] The dispersion medium is composed of at least one of an organic resin material and an organic solvent. If an organic resin material is used as the dispersion medium, it can be applied to resin compositions for electronic devices such as sealing materials, underfill agents, and substrates for semiconductor elements. If an organic solvent is used as the dispersion medium, it can be applied to slurry compositions and the like, and the slurry compositions and the like are used for supplying silica particle materials to resin materials.

[0079] As the organic resin material, either thermosetting resin or thermoplastic resin can be used, and the organic resin material before curing can also be used. Examples of the organic resin material include epoxy resin, silicone resin, urea resin, acrylic resin, etc. Examples of the organic solvent include ketones such as methyl ethyl ketone and acetone; hydrocarbons such as hexane and octane; alcohols such as methanol and ethanol; and aromatic hydrocarbons such as toluene and xylene.

[0080] Examples

[0081] Hereinafter, based on the examples, the alumina particle material of the present invention and its manufacturing method will be described in detail.

[0082] (Preliminary test)

[0083] A particle material composed of alumina with a volume average particle diameter of 0.2 μm and a specific surface area of 6.6 m 2 / g was used as the test specimen. This test specimen was prepared by the VMC method. For this test specimen, in an air atmosphere, it was heated at 200 °C for 480 minutes and then cooled in a normal-temperature air atmosphere. The moisture content of the test specimen was measured at 200 °C (just after heating), 80 °C (45 minutes after heating), and normal temperature (25 °C: 90 minutes after heating), and also at 3 hours, 4.5 hours, and 6 hours after heating. The results are shown in Table 1.

[0084] [Table 1]

[0085]

[0086] It is clearly understood from Table 1 that as the temperature of the test specimen approaches normal temperature, the moisture content increases. It should be noted that it can be seen that if the temperature of the test specimen decreases, the moisture content increases rapidly, and if the temperature does not change, the change in the moisture content almost disappears. That is, it can be seen that for the decrease in temperature, the moisture content also rapidly follows. In order to keep the moisture content low, after heating, it is necessary to maintain it at a condition with a low moisture content at a high temperature state, or perform the surface treatment described below.

[0087] (Test)

[0088] ·Examples 1 - 10

[0089] A particle material composed of alumina with the volume average particle diameter and specific surface area shown in Table 2 was used as the raw material particle material (raw material particle material preparation process). This raw material particle material was prepared by the VMC method. For this raw material particle material, in a vacuum atmosphere, it was heated at 160 °C for 30 minutes to obtain a dried raw material particle material (heating process).

[0090] After the heating step, surface treatment was carried out using the surface treatment agents of the respective examples shown in Table 2 under the condition of 10 minutes later (the temperature of the dried raw material particle material was 80 °C).

[0091] · Comparative Examples 1 to 10

[0092] The alumina particle materials prepared without performing the corresponding heating step of the examples were used as the test specimens for the respective comparative examples.

[0093] · Evaluation (moisture content, viscosity of resin composition, dielectric loss tangent, particle size, specific surface area)

[0094] The moisture content, viscosity of the resin composition, dielectric loss tangent, particle size, and specific surface area were measured for several of the test specimens of the respective examples and comparative examples, and are shown in Table 2.

[0095] The measurement of the moisture content was to measure the moisture content generated when heating from 25 °C to 200 °C and from 200 °C to 550 °C, calculate the moisture content per unit mass generated under each condition, and are shown in Table 2. The measurement of the moisture content generated when heating from 200 °C to 550 °C was carried out under the same conditions as the measurement of the moisture content when heating from 25 °C to 200 °C, except for changing the starting temperature and ending temperature of the heating temperature. For the raw material particle materials and dried raw material particle materials of the respective examples, the moisture content generated when heating from 25 °C to 200 °C was also measured, and the moisture content per unit mass generated under the conditions was calculated.

[0096] For the test specimens of the respective examples and comparative examples, a slurry-like resin composition (organic composition) was prepared by mixing to be 75% by mass in the resin material shown in Table 2. The viscosity of the prepared resin compositions of the respective examples was measured using a rheometer. The measurement conditions of the viscosity were carried out at a shear rate of 0.1 / s and 1 / s.

[0097] The value of the dielectric loss tangent was measured for the test specimens of the respective examples and comparative examples using a network analyzer.

[0098] The particle size was D50, and it was measured as the median particle size by laser diffraction / scattering method using LA960 manufactured by Horiba, Ltd. The specific surface area was measured by the BET method using nitrogen at room temperature (25 °C).

[0099] [Table 2]

[0100]

[0101] As is clearly shown in Table 2, the test specimens of the examples have less moisture content, lower dielectric loss tangent, and lower viscosity in the resin compared to the corresponding test specimens of the comparative examples without the heating process. In addition, the test specimens of the examples also have a smaller dielectric loss tangent compared to the corresponding test specimens of the comparative examples.

[0102] That is, it can be seen that the alumina particle material obtained by reducing the moisture content in the alumina particle material before surface treatment through the heating process can reduce the dielectric loss tangent and can also reduce the viscosity of the resin composition obtained by filling it into the resin material.

[0103] · Evaluation (Epoxy equivalent)

[0104] As test specimens, the epoxy equivalent was measured for the specimens of each test example in which the alumina particle material (manufactured by Admatechs: AO-502, D50 = 0.2 - 0.3 μm, specific surface area 6.5 - 9.0 m 2 / g) was subjected to the heating process and the surface treatment process under the conditions shown in Table 3.

[0105] The heating process was carried out at the temperature shown in Table 3 for 60 minutes, followed immediately by the HMDS surface treatment process. The measurement of the epoxy equivalent was performed on a mixture obtained by mixing 40 parts by mass of the test specimen and 60 parts by mass of epoxy resin (ZX-1059 (manufactured by NIPPON STEEL Chemical & Material Co., Ltd.)) immediately after the surface treatment process, and on the mixtures maintained at 110 °C for 12 hours and 24 hours after mixing. The heating at 110 °C was carried out by blowing air to the specimen after heating air with a relative humidity of 60% at 25 °C to 110 °C.

[0106] The epoxy equivalent was also measured only for the epoxy resin (ZX-1059 (manufactured by NIPPON STEEL Chemical & Material Co., Ltd.)). The results are shown in Table 3. Table 3 also records the values of the epoxy equivalent directly measured for the test specimens and the values converted only into resin. To convert only into resin, it can be carried out by multiplying each measured value by the mass ratio of the resin after mixing (0.6).

[0107] The specific epoxy equivalent was measured according to the following procedure.

[0108] 1. Titrate the dichloromethane added as a control specimen (Blank) with sodium hydroxide. alkane.

[0109] 2. Only measure a specified amount (W) of the test specimen to be measured into a conical flask, add an excessive amount of dichloromethane alkane solution, and use the solution in which the specimen is dissolved as the test solution.

[0110] 3. Add a phenolphthalein solution and use a burette to titrate the amount of diethyl ether hydrochloride remaining in the test solution with sodium hydroxide. 4. Calculate the epoxy equivalent according to the following formula using the difference between the amount of sodium hydroxide (Vb) equivalent to the added amount of diethyl ether hydrochloride and the amount of sodium hydroxide (Vs) equivalent to the amount of diethyl ether hydrochloride remaining in the test solution.

[0111] 4. Use the difference between the amount of sodium hydroxide (Vb) corresponding to the added amount of diethyl ether hydrochloride and the amount of sodium hydroxide (Vs) corresponding to the amount of diethyl ether hydrochloride remaining in the test solution, and calculate the epoxy equivalent according to the following formula. 9. The difference between the amount of sodium hydroxide (Vb) equivalent to the added amount of diethyl ether hydrochloride and the amount of sodium hydroxide (Vs) equivalent to the amount of diethyl ether hydrochloride remaining in the test solution. (Epoxy equivalent) = 10000W / f(Vb - Vs) [g / mol]

[0112] (Epoxy equivalent) = 10000W / f(Vb - Vs) [g / mol]

[0113] f: Titrant factor = 1

[0114] [Table 3]

[0115]

[0116] It is clear from Table 3 that without heating at 110°C, regardless of the presence or absence of the heating process and the heating temperature, the epoxy equivalent is at the same level. However, as the heating time at 110°C increases, compared with the test specimens of Test Example 1 without both the heating process and the surface treatment process, the epoxy equivalent of the test specimens of Test Examples 2 to 4 with only the surface treatment process becomes smaller. In addition, the more the amount of the surface treatment agent added in the surface treatment process, the smaller the epoxy equivalent. In addition, the epoxy equivalent of Test Examples 5 to 8 with both the heating process and the surface treatment process becomes even smaller. Here, if Test Example 5 with different temperatures in only the heating process is compared with Test Example 8, it can be seen that there is no significant difference between the two. If the heating temperature is 200°C or higher, sufficient effects can be achieved.

[0117] That is, after performing the heating process of the present invention, by quickly performing the surface treatment process before re-adsorbing moisture, it is possible to reduce the reaction points related to the increase in epoxy equivalent without being hindered by the moisture adsorbed on the surface.

[0118] Moreover, by performing the heating process, the increase rate of the epoxy equivalent before and after heating at 110°C can be suppressed to less than 8%. In addition, the increase in the epoxy equivalent due to heating at 110°C is smaller as the treatment amount of the surface treatment agent is within the range of 0.045%, 0.090%, and 0.120%.

[0119] In addition, although not shown in detail, the test specimens that are surface-treated after cooling to room temperature in the atmosphere after the heating process show an epoxy equivalent at the same level as the specimens without the heating process.

[0120] It is clear from the above results that by performing surface treatment, the increase in epoxy equivalent over time can be suppressed. Furthermore, it is known that by performing a heating process before the surface treatment process, the increase in epoxy equivalent over time can be further suppressed.

[0121] (Study on the elapsed time from the heating process to the surface treatment process)

[0122] · Comparative Example 11

[0123] After the heating process and before the surface treatment process, it was allowed to cool in the air to 25°C. Otherwise, the alumina particle material was prepared in the same manner as the test specimen of Manufacturing Example 1, and this was used as the test specimen of this comparative example. As a result, it showed the same levels of moisture content, dielectric loss tangent, and viscosity as Comparative Example 1 corresponding to Example 1. From this result, it can be seen that after drying, by cooling in an atmosphere with a humidity not equal to 0%, moisture is re-adsorbed and the effect of the heating process is reduced. That is, it is clear that even if the heating process is performed, if the moisture content is restored, the effect of the heating process will become smaller.

Claims

1. A method for manufacturing an alumina particle material, comprising: a raw material particle material preparation step of preparing a raw material particle material mainly composed of alumina; a heating step of maintaining the raw material particle material at 100°C to 300°C for 5 minutes or more to prepare a dried raw material particle material; and a surface treatment step of treating the dried raw material particle material in a state where the adsorption of moisture on the surface is less than that before the heating step with a surface treatment agent to mask at least a part of the OH groups present on the surface.

2. The manufacturing method of the alumina particle material according to claim 1, wherein, The heating temperature in the heating step is 150°C or higher.

3. The manufacturing method of the alumina particle material according to claim 1 or 2, wherein, During the period after the heating step and before the surface treatment step, at least one of the following conditions (1) and (2) is maintained: (1) Cooling is carried out while maintaining in a space with a limited amount of existing moisture, and (2) Natural cooling is carried out within a time when the temperature is not lower than 80°C.

4. The manufacturing method of the alumina particle material according to claim 1 or 2, wherein, After the surface treatment step, it does not come into contact with water, or has a reheating step of reheating to 100°C or higher again after coming into contact with water.

5. The manufacturing method of the alumina particle material according to claim 1 or 2, wherein, The heating process is carried out until the amount of OH groups converted from the water content per 1 g is 5×10 18 or less.

6. An alumina particle material, The volume average particle size is 2.0 μm or less, and the specific surface area is 1.5 m 2 / g or more, and the degree of gelatinization is less than 90%, the amount of water generated when heated from 25°C to 200°C is 700 ppm or less on a mass basis, the dielectric loss tangent is 0.0075 or less, has organic functional groups on the surface, is mainly composed of alumina and is spherical.

7. The alumina particle material according to claim 6, wherein, The volume average particle diameter is less than 0.5 μm.

8. The alumina particle material according to claim 6, wherein The increase rate of the epoxy equivalent after maintaining at 110°C for 12 hours is 8.0% or less.

9. An organic composition, comprising: the alumina particle material according to any one of claims 6 to 8, and a dispersion medium composed of at least one of an organic resin material or an organic solvent for dispersing the alumina particle material.

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