Method for producing spherical silica powder

Abstract

This invention provides a method for producing spherical silica powder with excellent dielectric properties from silicone resin powder. [Solution] A method for producing spherical silica powder, The manufacturing method involves placing spherical silicone resin powder into a furnace and raising the temperature inside the furnace to a calcination temperature (T1) of 1000 to 1500°C at a heating rate of 0.1 to 10°C / min in one or more stages; and A method for producing spherical silica powder, comprising: heating the spherical silicone resin powder at the aforementioned firing temperature (T1) for one hour or more.

Description

Technical Field

[0001] The present disclosure relates to a method for producing spherical silica powder.

Background Art

[0002] In recent years, with the increase in information traffic in the communication field, the signal frequency used in semiconductors has become increasingly high. For high-speed and low-loss signal transmission, fillers are required to have low dielectric constant and low dielectric loss. The dielectric constant and dielectric loss of a material basically depend on the chemical composition and structure of the material.

[0003] Silica particles have a relatively low dielectric constant and a quality factor index Qf (a value obtained by multiplying the reciprocal of the dielectric tangent by the measurement frequency) of about 120,000, and thus are promising as ceramic fillers having low dielectric constant and low dielectric tangent. From the perspective of facilitating blending into resins, it is more preferable that the shape is closer to spherical.

[0004] In addition to the method for producing spherical silica particles using inorganic materials, a method for producing spherical silica by preparing polysiloxane powder from an organosilicon compound as a raw material and then calcining it is known as a conventional method for producing spherical silica particles (Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Since spherical silicone resin contains carbon, if the calcination is not sufficient, carbon remains particularly in the central region (core part) of the fine particles, and in that case, it is difficult to obtain spherical silica powder having excellent dielectric properties.

[0007] The present disclosure aims to provide a method for producing spherical silica powder with excellent dielectric properties from silicone resin powder.

Means for Solving the Problems

[0008] The present disclosure includes the following aspects. A method for producing spherical silica powder, wherein the production method includes charging spherical silicone resin powder into a furnace and raising the temperature in the furnace to a calcination temperature (T1) of 1000 to 1500 °C at a heating rate of 0.1 to 10 °C / min in one step or two or more steps; and heat-treating the spherical silicone resin powder at the calcination temperature (T1) for 1 hour or more; A method for producing spherical silica powder, including.

Effects of the Invention

[0009] According to the present disclosure, a method for producing spherical silica powder with excellent dielectric properties from silicone resin powder can be provided.

Brief Description of the Drawings

[0010] [Figure 1a] Figure 1a is a diagram showing changes in heating rate (V0), heating temperature (T0), heating rate (V1), and calcination temperature (T1) in the heat treatment (Condition 1). [Figure 1b] Figure 1b is a diagram showing changes in heating rate (V1) and calcination temperature (T1) in the heat treatment (Condition 2). [Figure 1c] Figure 1c is a diagram showing changes in heating rate (V1) and calcination temperature (T1) in the heat treatment (Condition 3). [Figure 1d] Figure 1d is a diagram showing changes in heating rate (V1) and calcination temperature (T1) in the heat treatment (Condition 4).

Embodiments for Carrying Out the Invention

[0011] One embodiment of the present disclosure will be described in detail below, but the scope of the present disclosure is not limited to the embodiment described herein, and various modifications can be made without departing from the spirit of the present disclosure. Each embodiment disclosed herein can be combined with any other features disclosed herein. If multiple upper and lower limits are given for a particular parameter, any combination of these upper and lower limits can be used to create a suitable numerical range. The lower and / or upper limits of the numerical ranges described herein may be replaced with numerical values ​​within that range, as shown in the examples. The expression "X~Y" indicating a numerical range means "X or greater and Y or less". If a particular description given for one embodiment also applies to other embodiments, that description may be omitted in the other embodiments.

[0012] [Method for producing silica powder] The method for producing spherical silica powder according to this embodiment is as follows: The spherical silicone resin powder is placed in the furnace, and the temperature inside the furnace is raised to a calcination temperature (T1) of 1000°C to 1500°C at a heating rate of 0.1 to 10°C / min in one or more stages; and This includes heating the spherical silicone resin powder at the aforementioned firing temperature (T1) for at least one hour.

[0013] Spherical silicone resin powder readily absorbs moisture from the air during storage. As a result, water tends to remain in the fine particles that make up the resulting spherical silica powder, making it difficult to obtain spherical silica powder with excellent dielectric properties. Furthermore, since spherical silicone resin contains carbon, if calcination is insufficient, carbon will remain, especially in the central region (core) of the fine particles, also making it difficult to obtain spherical silica powder with excellent dielectric properties.

[0014] In the course of research, the inventors discovered that spherical silica powder with excellent dielectric properties can be produced by setting the calcination temperature of spherical silicone resin powder and the heating rate from room temperature to the calcination temperature within a predetermined range, and have completed this disclosure. The mechanism is not clear at this stage, but as a non-limiting mechanism, it is thought that by calcining at a predetermined temperature, carbon and moisture originating from the raw material are easily removed from the spherical silicone resin fine particles, and by raising the temperature at a predetermined rate, carbon and moisture in the central region of the spherical silicone resin fine particles can also be effectively removed.

[0015] <Raw material (silicone resin powder)> The method for producing spherical silica powder described herein uses spherical silicone resin powder as a raw material. "Spherical" in this context means that when the particles are observed with a microscope or the like, their projected view (including three-dimensional and two-dimensional views) is close to a circular shape.

[0016] In one embodiment, the method for producing spherical silica powder includes a step of preparing spherical silicone resin powder as a raw material.

[0017] The spherical silicone resin powder is not limited, but examples include those having a network structure formed by three-dimensionally linked siloxane bonds, and may also have one methyl group bonded to a silicon atom. Examples of commercially available spherical silicone resin powders include Tospar® products from Momentive Performance Materials Japan LLC, such as Tospar 120, Tospar 130, and Tospar 145; MSP-SN08 and MSP-SN05 from Nikko Rica Co., Ltd.; and KMP-706, KMP-590, and X-52-1621 from Shin-Etsu Chemical Co., Ltd. The spherical silicone resin powder may also be synthesized from organosilicon alkoxides. For example, vinyltrimethoxysilane or methyltrimethoxysilane can be synthesized by mixing and stirring them with an aqueous solution whose pH has been adjusted to be basic. The silicone resin powder may be used alone or in combination of two or more types.

[0018] The average particle size of the spherical silicone resin powder used as raw material is preferably 0.1 to 10 μm, more preferably 0.1 μm to less than 10 μm, and from the viewpoint of more easily obtaining spherical silica powder with a lower dielectric loss tangent, it is even more preferably 0.5 to less than 10 μm, and particularly preferably 0.6 to less than 10 μm.

[0019] In one embodiment, the average particle size of the spherical silicone resin powder may be distinguished by particle size, from the viewpoint of easily adjusting the heat treatment conditions. For example, it may be 0.1 μm or more and less than 2.5 μm, 2.5 μm or more and 5.0 μm or less, or greater than 5.0 μm and 10 μm or less.

[0020] The average particle size of the spherical silicone resin powder may be the manufacturer's catalog value, a value measured using image processing software with a scanning electron microscope (SEM), or the particle size corresponding to 50% of the cumulative value in the volume-based cumulative particle size distribution measured using a laser diffraction particle size distribution analyzer (D50). The cumulative particle size distribution is represented by a distribution curve with particle size (μm) on the horizontal axis and cumulative value (%) on the vertical axis.

[0021] <(1) Heating process> The method for producing spherical silica powder according to this disclosure includes a heating step of introducing spherical silicone resin powder into a furnace and raising the temperature inside the furnace to a calcination temperature (T1) of 1000 to 1500°C at a heating rate of 0.1 to 10°C / min in one or more stages. The furnace used is not limited, and any known electric furnace can be used. The timing of introducing the spherical silicone resin powder into the furnace is not limited, and may be at room temperature, or, for example, after preheating to a temperature of 200°C or lower.

[0022] Spherical silica powder with excellent dielectric properties can be easily produced from silicone resin powder by heating it to a predetermined calcination temperature (T1) in one or more stages at a predetermined heating rate. Whether to heat it to the calcination temperature (T1) in one stage or in two or more stages is preferably selected according to the average particle size of the raw material spherical silicone resin powder. For example, if the average particle size of the raw material spherical silicone resin powder is small (e.g., 0.1 μm or more and less than 2.5 μm), it is preferable to heat it in two or more stages. If the average particle size of the raw material spherical silicone resin powder is medium or larger (e.g., 2.5 μm or more), it may be heated in one stage or in two or more stages. When heating in two or more stages, it is preferably heated in 2 to 5 stages, more preferably in 2 to 3 stages, and even more preferably in 2 stages. Details of the calcination temperature (T1) will be described later.

[0023] The heating rate is preferably 0.1 to 9°C / min, more preferably 0.5 to 7°C / min, and more preferably 2 to 6°C / min. When the heating rate (V1) is within the range of 0.1 to 9°C / min, decarburization and dehydration are easily promoted.

[0024] In one embodiment, it is preferable that the manufacturing method is carried out by either (i) raising the temperature from room temperature to the baking temperature (T1) in one step, or (ii) raising the temperature from room temperature to the baking temperature (T1) in two or more steps.

[0025] In one embodiment, (i) raising the temperature in one step is preferably satisfied with condition 2 or condition 3 below, and (ii) raising the temperature in two or more steps is preferably satisfied with condition 1 below.

[0026] In other words, in one embodiment, the heating step preferably satisfies any of the following conditions 1 to 3. (Condition 1) A first heating step is performed in which the temperature is raised from room temperature to a temperature (T0) in the range of 350 to 550°C at a heating rate (V0) of 0.1 to 9°C / min, and then held at the said temperature (T0) for 5 to 7 hours. This includes a second heating step, in which the temperature is raised from the aforementioned temperature (T0) to the aforementioned firing temperature (T1) at a heating rate of 0.1 to 9°C / min. (Condition 2) The heating is carried out in one step from room temperature to the aforementioned firing temperature (T1) at a heating rate of more than 3°C / min and less than or equal to 9°C / min. (Condition 3) The heating is carried out in one step from room temperature to the aforementioned firing temperature (T1) at a heating rate of 0.1 to 3°C / min.

[0027] {condition 1} By satisfying Condition 1, the temperature is raised in two or more stages, which effectively removes carbon and water from the central region (core) of the spherical silicone resin fine particles. This makes it easier to obtain spherical silica powder with excellent dielectric properties, regardless of the average particle size of the raw material spherical silicone resin powder. Condition 1 includes a first temperature increase and a second temperature increase.

[0028] (First temperature increase) In the first heating step, the temperature (T0) is 350 to 550°C, and from the viewpoint of promoting decarburization and dehydration over a wide range from the surface region to the center region of the spherical silicone resin fine particles, 400 to 500°C is preferred, and 420 to 450°C is more preferred. In the first heating step, the heating rate (V0) is in the range of 0.1 to 9°C / min, and from the viewpoint of promoting decarburization and dehydration over a wide range from the surface region to the center region of the spherical silicone resin fine particles, 0.5 to 7°C / min is preferred, and 2 to 6°C / min is more preferred. In the first heating step, the holding time after heating to the temperature (T0) is 5 to 7 hours, preferably 5 to 6 hours, from the viewpoint of making it easier to obtain spherical silica powder with excellent dielectric properties.

[0029] (Second temperature increase) In the second heating stage, the heating rate (V1) is in the range of 0.1 to 9°C / min, preferably 0.5 to 7°C / min, and more preferably 2 to 6°C / min. When the heating rate (V1) in the second heating stage is in the range of 0.1 to 9°C / min, decarburization and dehydration are easily promoted over a wide range from the surface region to the center region of the spherical silicone resin fine particles.

[0030] {condition 2} By satisfying condition 2, the temperature can be raised in a single step, making it easier to obtain spherical silica powder with superior dielectric properties.

[0031] In condition 2, the heating rate to the calcination temperature (T1) is greater than 3°C / min and less than or equal to 9°C / min. From the viewpoint of more easily obtaining spherical silica powder with excellent dielectric properties, 3.5 to 8.5°C / min is preferred, 4 to 8°C / min is more preferred, and 5°C / min is also acceptable. This may be used as the upper or lower limit.

[0032] {condition 3} By satisfying condition 3, the temperature is raised in a single step, making it easier to obtain spherical silica powder with superior dielectric properties. Furthermore, because the temperature is raised more gradually than under condition 2, carbon and water in the central region (core) of the spherical silicone resin fine particles are removed more effectively, making it easier to obtain spherical silica powder with superior dielectric properties regardless of the average particle size of the raw material spherical silicone resin powder.

[0033] In condition 3, the heating rate to the calcination temperature (T1) is 0.1 to 3°C / min, and from the viewpoint of more easily obtaining spherical silica powder with excellent dielectric properties, 0.5 to 2.5°C / min is preferred, 1.5 to 2.2°C / min is more preferred, and 2°C / min may also be used, and this may be set as the upper or lower limit.

[0034] In one embodiment, if the average particle size of the spherical silicone resin powder raw material is 0.1 μm or more and less than 2.5 μm, it is preferable that the heating step satisfies condition 1. By satisfying condition 1, it is easier to obtain spherical silica powder with a low dielectric loss tangent.

[0035] In one embodiment, when the average particle size of the raw material spherical silicone resin powder is 2.5 to 10 μm, the heating step may satisfy any of conditions 1 to 3, preferably condition 1 or 3. In any of conditions 1 to 3, spherical silica powder with a low dielectric loss tangent is easily obtained.

[0036] <(2) Heat treatment process> In the heat treatment process, the spherical silicone resin powder is heat-treated at a calcination temperature (T1) of 1000 to 1500°C for at least one hour. By heat-treating at a calcination temperature (T1) of 1000 to 1500°C for at least one hour, spherical silica powder with excellent dielectric properties is obtained.

[0037] The calcination temperature (T1) is 1000 to 1500°C, preferably 1050 to 1400°C. A calcination temperature (T1) of 1000 to 1500°C further promotes dehydration and decarburization, allowing for the production of spherical silica particles with excellent dielectric properties. On the other hand, if the temperature during the heat treatment exceeds 1500°C, the dispersibility of the spherical silica particles in the resin deteriorates due to particle fusion, etc.

[0038] In one embodiment, when the heating process is performed in a single step (preferably when condition 2 or condition 3 is met), the calcination temperature (T1) is preferably 1100°C to 1500°C, more preferably above 1100°C and below 1400°C, and even more preferably 1200°C to 1300°C, from the viewpoint of making it easier to obtain spherical silica powder with excellent dielectric properties.

[0039] In one embodiment, when the heating process is carried out in two or more stages (preferably satisfying condition 1), the calcination temperature (T1) is preferably 1020 to 1400°C, more preferably 1050 to 1300°C, and even more preferably 1100°C or higher and less than 1200°C, from the viewpoint of making it easier to obtain spherical silica powder with excellent dielectric properties.

[0040] The heating time after raising the temperature to the aforementioned firing temperature (T1) is 1 hour or more, more preferably 2 to 14 hours, and even more preferably 3 to 12 hours, from the viewpoint of easily obtaining spherical silica powder with excellent dielectric properties.

[0041] In one embodiment, heat treatment is performed in order to more easily obtain spherical silica powder with excellent dielectric properties. (i) If the heating is performed in one step (preferably satisfying condition 2 or condition 3), this includes heating the spherical silicone resin powder at the firing temperature (T1) for less than 6 hours (preferably 1 to 5 hours, more preferably 1 to 3 hours), (ii) If the heating is performed in two or more stages (preferably satisfying condition 1), it is preferable that the spherical silicone resin powder is heat-treated at the firing temperature (T1) for 1 to 14 hours (preferably 3 to 13 hours, more preferably 9 to 12 hours).

[0042] After the above heat treatment, spherical silica powder can be obtained by cooling to room temperature, for example, by natural cooling. The spherical silica powder may be classified as needed.

[0043] <Method for measuring the heating rate> The rate at which the temperature rises from the ambient temperature (room temperature) inside the electric furnace to the firing temperature (T1) can be calculated by dividing it by the time (minutes) it takes to reach the firing temperature (T1). Similarly, the rate at which the temperature rises from the ambient temperature (room temperature) inside the electric furnace to the temperature (T0) can be calculated by dividing it by the time (minutes) it takes to reach the temperature (T0).

[0044] [Spherical silica powder] The spherical silica powder obtained by the method for producing spherical silica powder according to this embodiment contains amorphous spherical silica particles. "Spherical" here means that when the particles are observed with a microscope or the like, their projection (including three-dimensional and plan views) is close to a circular shape. The spherical silica powder is preferably perfectly spherical. "Perfectly spherical" here means that when the particles are observed with a microscope or the like, their projection (including three-dimensional and plan views) is approximately circular. The crystalline structure of the spherical silica has an amorphous phase that accounts for 95% or more by mass of the total. By having an amorphous phase of 95% or more, the effect of suppressing the coefficient of thermal expansion during resin filling is greatly increased.

[0045] In one embodiment, the spherical silica powder preferably has a dielectric tangent of the spherical silica powder calculated under the following conditions of 0.002 or less, more preferably 0.0019 or less, even more preferably 0.0011 or less, particularly preferably 0.0008 or less, and most preferably 0.0007 or less. The spherical silica powder with a dielectric tangent of the spherical silica powder calculated under the following conditions of 0.002 or less can better prevent the transmission loss of circuit signals in electronic devices, communication devices, etc. to which a high-frequency band is applied.

[0046] <Dielectric constant> In one embodiment, the dielectric constant (εr f ) calculated under the following conditions is preferably 3.5 to 4.5. <Condition> A sheet (thickness: 0.3 mm, diameter: 30 mm) of a resin composition composed of 60 to 90% by volume of a polyethylene resin (density: 0.92 g / cm 3 ) and 10 to 40% by volume of an inorganic powder is measured for the dielectric constant (εr c ) using a split cylinder resonator at a measurement frequency of 40 GHz, a temperature of 20 °C, and a humidity of 60% RH. Then, the dielectric constant (εr f ) is calculated from the following formula (2). log(εr c ) = V f · log(εr f ) + (1 - V f )· log(εr r ) ···(2) (In formula (2), εr c , εr f , εr r represent the dielectric constants of the resin composition, spherical silica powder, and polyethylene resin, respectively, and V f represents the content (volume %) of the spherical silica powder in the resin composition.)

[0047] <Dielectric tangent> In one embodiment, it is calculated using a sheet of the resin composition under the same conditions as above. The dielectric tangent (tanδ f ) of the spherical silica powder can be calculated from the following formula (1). tanδ c = Vf ·tanδ f +(1-V f )·tanδ r ...(1) (In formula (1), V f This represents the content (volume %) of spherical silica powder in the resin composition, and tanδ c represents the dielectric loss tangent of the resin composition, and tanδ r (This represents the dielectric loss tangent of polyethylene resin.)

[0048] In one embodiment, the spherical silica powder has a BET specific surface area of ​​0.5 to 4.5 m². 2 A value of / g is preferred, and the BET specific surface area can be measured by the BET single-point method using nitrogen gas adsorption.

[0049] In one embodiment, the BET specific surface area of ​​the spherical silica powder is 4.5 m². 2 The particle size is preferably less than or equal to / g, and the dielectric loss tangent of the spherical silica powder is preferably 0.002 or less; the BET specific surface area of ​​the spherical silica powder is preferably 2.5 m². 2 The density is less than or equal to / g, and the dielectric loss tangent of the spherical silica powder is more preferably 0.0011 or less; the BET specific surface area of ​​the spherical silica powder is 2.0 m². 2 The particle size is less than or equal to / g, and the dielectric loss tangent of the spherical silica powder is more preferably 0.0008 or less; the BET specific surface area of ​​the spherical silica powder is 1.5m². 2 The amount is less than or equal to / g, and it is even more preferable that the dielectric loss tangent of the spherical silica powder is 0.00065 or less; the BET specific surface area of ​​the spherical silica powder is 1.0 to 1.5 m². 2 The value is / g, and it is particularly preferable that the dielectric loss tangent of the spherical silica powder is 0.00055 or less.

[0050] The average particle size (D50) of the spherical silica powder is not limited, but is preferably 0.1 to 30 μm, more preferably 0.2 to 15 μm, and even more preferably 0.3 to 10 μm. If the average particle size of the spherical silica powder is within the above range, it is easier to achieve good packing properties in the resin. The average particle size is defined as the particle size (D50) corresponding to 50% of the cumulative value in the volume-based cumulative particle size distribution measured using a laser diffraction particle size distribution analyzer. The cumulative particle size distribution is represented by a distribution curve with particle size (μm) on the horizontal axis and cumulative value (%) on the vertical axis.

[0051] The spherical silica powder is preferably white to gray in color. When the spherical silica powder is white to gray, decarburization is progressing favorably, resulting in spherical silica powder with superior dielectric properties. Furthermore, when used as a resin filler, it is easier to obtain molded products with excellent appearance.

[0052] The spherical silica powder obtained by the manufacturing method of the above embodiment is a ceramic product of spherical silicone resin powder. This can be confirmed by measuring the particle size of the primary particles using SEM observation, which shows that the primary particles are monodisperse (D90 / D10 < 2.0).

[0053] [Application] The spherical silica powder obtained by the manufacturing method described herein has excellent dielectric properties and is therefore suitable for use as a filler for resin materials. When used as a substrate material or insulating material for high frequency bands, it can be used as a filler for known low-dielectric resins. Examples of low-dielectric resins include hydrocarbon-based elastomer resins, polyphenylene ether resins, and aromatic polyene resins.

[0054] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of this disclosure are disclosed below. [1] A method for producing spherical silica powder, The manufacturing method involves placing spherical silicone resin powder into a furnace and raising the temperature inside the furnace to a calcination temperature (T1) of 1000 to 1500°C at a heating rate of 0.1 to 10°C / min in one or more stages; and A method for producing spherical silica powder, comprising: heating the spherical silicone resin powder at the aforementioned firing temperature (T1) for one hour or more. [2] The method for producing spherical silica powder according to [1], wherein the average particle size of the spherical silicone resin powder is 0.1 to 10 μm. [3] The heat treatment described above is (i) If the heating is performed in one step, this includes heating the spherical silicone resin powder at the firing temperature (T1) for less than 6 hours. (ii) If the heating is performed in two or more stages, this includes heating the spherical silicone resin powder at the firing temperature (T1) for 1 to 14 hours. A method for producing spherical silica powder as described in [1] or [2]. [4] The above-mentioned temperature increase is due to any of the following conditions 1 to 3: (Condition 1) The first heating is performed by raising the temperature from room temperature to a temperature (T0) in the range of 350 to 550°C at a heating rate of 0.1 to 9°C / min, and then holding the temperature (T0) for 5 to 7 hours. This includes a second heating step, in which the temperature is raised from the aforementioned temperature (T0) to the aforementioned firing temperature (T1) at a heating rate of 0.1 to 9°C / min; (Condition 2) The heating process is carried out in one step from room temperature to the aforementioned firing temperature (T1) at a heating rate of more than 3°C / min and no more than 9°C / min; (Condition 3) The heating process is carried out in one step, from room temperature to the aforementioned firing temperature (T1) at a heating rate of 0.1 to 3°C / min; A method for producing spherical silica powder according to any of [1] to [3] that satisfies the following conditions. [5] The above-mentioned raising of temperature is If the average particle size of the spherical silicone resin powder is 0.1 μm or more and less than 2.5 μm, then condition 1 is satisfied. The method for producing spherical silica powder according to any of [1] to [4], provided that the average particle size of the spherical silicone resin powder is 2.5 to 10 μm, and any of the above conditions 1 to 3 are met. [6] A method for producing spherical silica powder according to any one of [1] to [5], wherein the dielectric loss tangent of the spherical silica powder calculated under the following conditions is 0.002 or less. <Condition> The dielectric loss tangent (tanδ) of a sheet (thickness: 0.3 mm, diameter: 30 mm) of a resin composition consisting of 60-90 volume% polyethylene resin and 10-40 volume% of the spherical silica powder. c The dielectric loss tangent (tanδ) was measured using a split-cylinder resonator at a measurement frequency of 40 GHz, a temperature of 20°C, and a humidity of 60% RH. f ) is calculated using the following formula (1). tanδ c =V f ·tanδ f +(1-V f )·tanδ r ...(1) (In formula (1), V f This represents the content (volume %) of spherical silica powder in the resin composition, and tanδ c represents the dielectric loss tangent of the resin composition, and tanδ r (This represents the dielectric loss tangent of polyethylene resin.) Each configuration and its combination in each embodiment is an example, and additions, omissions, substitutions, and other modifications can be made as appropriate without departing from the spirit of this disclosure. This disclosure is not limited by the embodiments. [Examples]

[0055] The following experimental and reference examples will further illustrate this disclosure, but these examples are not intended to limit the interpretation of this disclosure.

[0056] In the experimental example, the following silicone resin powders were used as raw materials. Raw material 1: Spherical silicone resin powder, manufactured by Momentive Performance Materials Japan LLC, "Tospearl (registered trademark) 120" Raw material 2: Spherical silicone resin powder, manufactured by Momentive Performance Materials Japan LLC, "Tospearl (registered trademark) 130" Raw material 3: Spherical silicone resin powder, Shin-Etsu Silicone, "X-52-1621" Raw material 4: Spherical silicone resin powder, Shin-Etsu Silicone, "KMP-706"

[0057] For each of the silicone resin powders listed above (raw materials 1-4), various physical properties (appearance, specific surface area, average particle size) were measured using the same measurement method as for the silica powder described later. The results are shown in Table 1.

[0058] In the experimental example, one of the following heat treatment steps [Condition 1] to [Condition 4] was used. [Condition 1] Under atmospheric conditions, the temperature inside an electric furnace (manufactured by Motoyama Co., Ltd., product name: Atmospheric High-Speed ​​Heating Electric Furnace NLA-2025D-SP) was raised from room temperature to 450°C at an air supply rate of 2 L / min and a heating rate of 5°C / min. The temperature inside the electric furnace was then maintained at a temperature (T0) of 450°C for 6 hours for heat treatment. Subsequently, the temperature inside the electric furnace was further raised to 1100°C at a heating rate of 5°C / min, and the calcination temperature (T1) was maintained at 1100°C for 12 hours while circulating 2 L / min of air into the electric furnace for heat treatment. [Condition 2] Under atmospheric conditions, the temperature inside the electric furnace was increased from room temperature to 1200°C at a heating rate of 5°C / min. The furnace was then heated while 2 L / min of air was flowed through it, and the calcination temperature (T1) of 1200°C was maintained for 3 hours. [Condition 3] Under atmospheric conditions, the temperature inside the electric furnace was increased from room temperature to 1200°C at a heating rate of 2°C / min. The furnace was then heated and maintained at a calcination temperature (T1) of 1200°C for 3 hours while 2 L / min of air was flowed into it. [Condition 4] Under atmospheric conditions, the temperature inside the electric furnace was increased from room temperature to 1200°C at a heating rate of 10°C / min. The furnace was then heated and maintained at a calcination temperature (T1) of 1200°C (T1) for 3 hours while 2 L / min of air was flowed into the furnace.

[0059] [Experimental Examples 1-4] 30g of spherical silicone resin powder (average particle size: 2.0 μm, measured by SEM particle size measurement) of raw material 1 was placed in an alumina container (φ=5cm, depth 3cm, no lid) and placed in an electric furnace (manufactured by Motoyama Co., Ltd., product name: atmosphere-type high-speed heating electric furnace). The furnace was then heated under one of the conditions 1 to 4 shown in Table 1. After that, the furnace was allowed to cool naturally until it reached room temperature, and the calcined material was collected. The obtained powder was measured using a dry densimeter (pycnometer), and the true density of amorphous silica (approximately 2.2 g / cm³) was determined. 3 It was confirmed that silica powder was obtained by having ).

[0060] [Experimental Examples 5-7] Silica powder was obtained using the same method as in Experimental Example 1, except that raw material 2 (average particle size: 3.0 μm as measured by SEM particle size measurement) was heat-treated under the conditions shown in Table 2.

[0061] [Experimental Examples 8, 9] Silica powder was obtained using the same method as in Experimental Example 1, except that raw material 3 (average particle size: 5.0 μm as measured by SEM particle size measurement) or raw material 4 (average particle size: 2.0 μm as measured by SEM particle size measurement) was heat-treated under the conditions shown in Table 3.

[0062] [Reference example] As a reference example, spherical silica powder made from inorganic materials (manufactured by Denka Co., Ltd., product name: Fused Silica GT Grade, model number: GT3SDC) was prepared.

[0063] [measurement] The appearance, specific surface area, average particle size, dielectric constant, and dielectric loss tangent of the silica powder obtained above were measured using the following methods. The measurement results are shown in Tables 1 to 4.

[0064] <External observation> The surface color of the obtained spherical silica powder was visually determined. Furthermore, particle shapes were observed using a scanning electron microscope (JEOL Ltd., "JSM-7001F SHL") at magnifications of 10,000 to 50,000 times.

[0065] <Specific surface area> 1 g of the obtained spherical silica powder was packed into a measuring cell, and the specific surface area was measured using a fully automated specific surface area diameter analyzer (Mountech, product name: Macsorb HM model-1201 (BET 1-point method)). The degassing conditions before measurement were 200°C for 10 minutes.

[0066] <Average particle diameter (D50)> The average particle size was measured using a laser diffraction particle size distribution analyzer (Beckman Coulter, product name: LS 13 320). First, 50 cm³ of material was collected in a glass beaker. 3 Ethanol and 0.1 g of spherical silica powder were added and dispersed for 1 minute using an ultrasonic homogenizer (BRANSON, product name: SFX250). The dispersed spherical silica powder was added drop by drop using a dropper to a laser diffraction particle size distribution analyzer, and measurements were taken 30 seconds after the predetermined amount was added. The particle size distribution was calculated from the light intensity distribution data of the diffracted / scattered light of the spherical silica powder detected by the sensor in the laser diffraction particle size distribution analyzer. The average particle diameter was calculated from the particle diameter corresponding to 50% of the cumulative value in the volume-based cumulative particle size distribution of the measured particle diameter.

[0067] <Evaluation of dielectric properties (dielectric constant and dielectric loss tangent)> (conditions) Polyethylene resin (density: 0.92 g / cm³) 3 The dielectric constant (εr) of a sheet (thickness: 0.3 mm, diameter: 30 mm) of a resin composition consisting of 60 volume% of Sumitomo Seika Co., Ltd.'s product name "Flosen (registered trademark) UF-20S" and 40 volume% of spherical silica powder. cThe dielectric constant (εr) of the inorganic powder was measured using a split-cylinder resonator at a measurement frequency of 40 GHz, a temperature of 20°C, and a humidity of 60% RH. f ) was calculated using the following formula (2). log(εr c )=V f ·log(εr f )+(1-V f )·log(εr r ) ···(2) (In formula (2), εr c , εr f , εr r These represent the dielectric constants of the resin composition, spherical silica powder, and polyethylene resin, respectively. f This represents the content (volume %) of spherical silica powder in the resin composition.

[0068] Furthermore, using the same sheet as described above, the dielectric loss tangent was measured in a split-cylinder resonator at a measurement frequency of 40 GHz, a temperature of 20°C, and a humidity of 60% RH. Subsequently, the dielectric loss tangent (tanδ) was calculated. f ) was calculated from the following formula (1). tanδ c =V f ·tanδ f +(1-V f )·tanδ r ...(1) (In formula (1), V f This represents the content (volume %) of spherical silica powder in the resin composition, and tanδ c represents the dielectric loss tangent of the resin composition, and tanδ r (This represents the dielectric loss tangent of polyethylene resin.)

[0069] [Table 1]

[0070] [Table 2]

[0071] [Table 3]

[0072] [Table 4]

[0073] As shown in Experimental Examples 1 to 9, spherical silica powder with a low dielectric loss tangent of 0.002 or less at 40 GHz can be produced by heating spherical silicone resin powder from room temperature to a predetermined heating rate and then calcining it at the predetermined calcination temperature. From Experimental Examples 1-4 and 9, when the average particle size of the raw material spherical silicone resin powder is 0.1 μm or more and less than 2.5 μm, heating treatment under condition 1 above makes it easier to obtain spherical silica powder with a lower dielectric loss tangent. From Experimental Examples 5-8, when the average particle size of the spherical silicone resin powder used as raw material is 2.5-10 μm, a spherical silica powder with a lower dielectric loss tangent is more easily obtained by satisfying any of the above conditions 1-3. [Industrial applicability]

[0074] The method for producing spherical silica powder according to this embodiment yields spherical silica powder with excellent dielectric properties, and therefore has industrial potential for use, for example, as a filler in resins.

Claims

1. A method for producing spherical silica powder, The manufacturing method involves placing spherical silicone resin powder into a furnace and raising the temperature inside the furnace to a calcination temperature (T1) of 1000 to 1500°C at a heating rate of 0.1 to 10°C / min in one or more stages; and A method for producing spherical silica powder, comprising: heating the spherical silicone resin powder at the aforementioned firing temperature (T1) for one hour or more.

2. The method for producing spherical silica powder according to claim 1, wherein the average particle size of the spherical silicone resin powder is 0.1 to 10 μm.

3. The aforementioned heat treatment is performed (i) If the heating is performed in one step, this includes heating the spherical silicone resin powder at the firing temperature (T1) for less than 6 hours. (ii) If the heating is performed in two or more stages, this includes heating the spherical silicone resin powder at the firing temperature (T1) for 1 to 14 hours. A method for producing spherical silica powder according to claim 1 or 2.

4. The aforementioned temperature increase is performed under any of the following conditions 1 to 3: (Condition 1) A first heating step is performed in which the temperature is raised from room temperature to a temperature (T0) in the range of 350 to 550°C at a heating rate of 0.1 to 9°C / min, and then held at the said temperature (T0) for 5 to 7 hours. This includes a second heating step, in which the temperature is raised from the aforementioned temperature (T0) to the aforementioned firing temperature (T1) at a heating rate of 0.1 to 9°C / min; (Condition 2) The heating process is carried out in one step from room temperature to the aforementioned firing temperature (T1) at a heating rate of more than 3°C / min and less than or equal to 9°C / min; (Condition 3) The heating process is carried out in one step from room temperature to the aforementioned firing temperature (T1) at a heating rate of 0.1 to 3°C / min; A method for producing spherical silica powder according to claim 1 or 2, satisfying the requirements.

5. The aforementioned temperature increase is If the average particle size of the spherical silicone resin powder is 0.1 μm or more and less than 2.5 μm, then condition 1 is satisfied. The method for producing spherical silica powder according to claim 4, wherein any of the above conditions 1 to 3 are satisfied when the average particle size of the spherical silicone resin powder is 2.5 to 10 μm.

6. A method for producing spherical silica powder according to claim 1 or 2, wherein the dielectric loss tangent of the spherical silica powder calculated under the following conditions is 0.002 or less. <Conditions> The dielectric loss tangent (tanδ) of a sheet (thickness: 0.3 mm, diameter: 30 mm) of a resin composition consisting of 60-90 volume% polyethylene resin and 10-40 volume% of the spherical silica powder. ｃ The dielectric loss tangent (tanδ) is measured using a split-cylinder resonator at a measurement frequency of 40 GHz, a temperature of 20°C, and a humidity of 60% RH. ｆ ) is calculated using the following formula (1), tent ｃ =V ｆ ・Tanδ ｆ + (1-V) ｆ )・Tanδ ｒ ・・・(1) (In formula (1), V ｆ represents the content (volume %) of the spherical silica powder in the resin composition, and tan δ ｃ represents the dielectric tangent of the resin composition, and tan δ ｒ represents the dielectric tangent of the polyethylene resin.)

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