Magnesium oxide powder, method for producing same, mixed powder, and resin composition

Abstract

Provided are a magnesium oxide powder capable of achieving both low viscosity and high thermal conductivity when filled into a resin, a method for producing the same, a mixed powder containing the magnesium oxide powder, and a resin composition containing the magnesium oxide powder.　The magnesium oxide powder contains a particle group in which the ratio (R) of the total area (B) of open pores present in all particles to the total area (A) of all the particles present in an observation image is 9.0% or less when the magnesium oxide powder is observed by a scanning electron microscope under a specific condition.

Description

Magnesium oxide powder, its manufacturing method, mixed powder, and resin composition

[0001] The present invention relates to a magnesium oxide powder, a method for producing the same, a mixed powder, and a resin composition.

[0002] In recent years, electrical devices have become smaller and more powerful. As the size and performance of electrical devices have decreased, the density of electronic components that make up the electrical devices has increased, increasing the need to effectively dissipate heat generated by the electronic components.

[0003] Furthermore, in power device applications such as electric vehicles, which have a low environmental impact, high voltages or large currents may be applied to electronic components, which generates a large amount of heat. To address this, there is an increasing demand for more effective heat dissipation than ever before.

[0004] To meet such demands, resin compositions containing thermally conductive inorganic powder as a filler are used. For example, magnesium oxide powder is known as the thermally conductive inorganic powder, and Patent Document 1 discloses specific spherical magnesium oxide particles.

[0005] Japanese Patent Application Laid-Open No. 2018-131378

[0006] However, resin compositions containing only magnesium oxide powder as a filler have the problem of high compound viscosity. Therefore, in order to prevent the resin composition from thickening, magnesium oxide powder is sometimes combined with other inorganic powders and filled into the resin. In this case, depending on the inorganic powder used, problems such as a decrease in thermal conductivity may occur, and when an inorganic powder with high hardness is used, problems such as wear on molding machines and kneading machines may occur. Therefore, there is a demand for magnesium oxide powder that does not result in a high compound viscosity even when used alone as a filler in a resin.

[0007] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a magnesium oxide powder that can achieve both low viscosity and high thermal conductivity when filled into a resin, a method for producing the same, a mixed powder containing the magnesium oxide powder, and a resin composition containing the magnesium oxide powder.

[0008] As a result of extensive research, the present inventors have found that a magnesium oxide powder having the following configuration can solve the above problems. [1] A magnesium oxide powder comprising a particle group in which, when the magnesium oxide powder is observed with a scanning electron microscope under the following conditions, the ratio (R) of the total area (B) of open pores present within all particles to the total area (A) of all particles present in the observed image is 9.0% or less. (Conditions) The magnesium oxide powder is embedded in an epoxy resin and then cured. It is then processed using a cross-section processing device to prepare a sample of the magnesium oxide powder. A cross-section of the sample is observed with a scanning electron microscope at 500x magnification, and the resulting image is analyzed using image analysis software to calculate the total area (A) of all particles present in the observed image. Similarly, the total area (B) of open pores communicating with the particle surfaces of all particles in the observed image is calculated. Then, the ratio (R) of the total area (B) of the open pores to the total area (A) is determined.

[0009] According to the present invention, it is possible to provide a magnesium oxide powder that can achieve both low viscosity and high thermal conductivity when filled into a resin, a method for producing the same, a mixed powder containing the magnesium oxide powder, and a resin composition containing the magnesium oxide powder.

[0010] 1 is a photograph of the magnesium oxide powder of Example 1 after image processing.

[0011] An embodiment of the present disclosure will be described in detail below. However, 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 aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Furthermore, when multiple upper and lower limit values ​​are described for a specific parameter, any of these upper and lower limit values ​​can be combined to form a suitable numerical range. Furthermore, the lower and / or upper limit values ​​of a numerical range described in this disclosure are numerical values ​​within that numerical range and may be replaced with numerical values ​​shown in the examples. The expression "1 to 10" indicating a numerical range means "1 or more and 10 or less." If a specific description described for one embodiment also applies to other embodiments, that description may be omitted in other embodiments.

[0012] The configurations and combinations thereof in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible as appropriate within the scope of the gist of the present disclosure. The present disclosure is not limited to the embodiments.

[0013] Each aspect disclosed herein may be combined with any other feature disclosed herein. As used herein, the term "powder" refers to an aggregate of multiple particles.

[0014] [Magnesium oxide powder] A first embodiment of the present disclosure relates to a magnesium oxide powder. The first embodiment relates to a magnesium oxide powder including a particle group in which, when the magnesium oxide powder is observed with a scanning electron microscope under the following conditions, the ratio (R) of the total area (B) of open pores present within all particles to the total area (A) of all particles present in the observed image is 9.0% or less. (Conditions) The magnesium oxide powder is embedded in an epoxy resin and then cured. It is then processed using a cross-section processing device to create a sample of the magnesium oxide powder. The cross-section of the sample is observed with a scanning electron microscope at 500x magnification, and the resulting image is analyzed using image analysis software to calculate the total area (A) of all particles present in the observed image. Similarly, the total area (B) of open pores that communicate with the particle surfaces of all particles in the observed image is calculated. Then, the ratio (R) of the total area (B) of the open pores to the total area (A) is determined.

[0015] A more specific example of a method for preparing a magnesium oxide powder sample is described below. First, pretreatment is performed under the following conditions, followed by observation and image processing using a scanning electron microscope. Pretreatment: Magnesium oxide powder (0.1 g) is mixed with a two-component thermosetting epoxy resin (e.g., Gatan's product name "G2") (resin:hardener = 10:1). Then, the sample is vacuum-impregnated (0.1 MPa, approximately 20 minutes) using a vacuum impregnation device (e.g., Buhler ITW Japan's product name "Cast N1000"). The vacuum-impregnated epoxy resin containing magnesium oxide powder (hereinafter referred to as the "sample solution") is poured into an embedding plate. The embedding plate is placed on a hot plate and heated at 110°C for 2 hours to harden the sample solution. The hardened sample liquid (hereinafter referred to as "hardened sample") is attached to a cross-section processing device (ion milling device (e.g., Hitachi High-Tech Corporation, product name "IM4000PLUS")), and subjected to broad ion beam processing (acceleration voltage: 4 kV, processing time: 5 hours) to prepare a cross-section sample.

[0016] Observation by Scanning Electron Microscope: The cross-sectional sample is fixed to the observation sample stage of a scanning electron microscope (hereinafter referred to as "SEM"), and the sample stage is attached to an SEM observation holder. The SEM observation holder is then introduced into a field emission SEM (for example, JEOL Ltd., product name "JSM-7001F") for SEM observation (acceleration voltage: 15 kV, WD: 10 mm). An arbitrary particle group on the cross-sectional sample is observed at 500x magnification to obtain an image.

[0017] Image Processing: The observation image obtained above is analyzed using image analysis software (e.g., MEDIA CYBERNETICS, product name "Image Pro Premier"). First, the observation image is binarized using the image analysis software. At this time, particles (magnesium oxide particles) in the cross-sectional sample are lightly highlighted, and the epoxy resin is displayed in a dark color. Furthermore, within the voids inside the particles, the portions impregnated with the epoxy resin are displayed in the same dark color as the epoxy resin, and portions not impregnated with the epoxy resin are displayed with a white highlight surrounding the edge. That is, in this embodiment, among the voids present in the particle group in the observation image, voids displayed in the same dark color as the epoxy resin are determined to be "open pores," and voids surrounded by a white highlight surrounding the edge are determined to be "closed pores." In this embodiment, for the particle group present in the observation image, the interface between the epoxy resin and the portions corresponding to the particles is surrounded by the image analysis software, and the total area (A) is calculated. Furthermore, among the voids inside each particle, the portions (open pores) marked in the same dark color as the epoxy resin are circled at the interface with the particle using image analysis software, and the total area (B) is calculated. Furthermore, the ratio (R) of open pores in the particle group is calculated as (B) / (A)×100(%).

[0018] As described above, the "open pores" in the magnesium oxide powder according to the first embodiment (hereinafter sometimes simply referred to as "powder") refer to voids that extend from the surface of the magnesium oxide particles to the interior of the particles, and that allow the epoxy resin to penetrate when the magnesium oxide powder is embedded in epoxy resin under the aforementioned conditions (i.e., voids that are displayed in the same dark color as the epoxy resin in image analysis processing). On the other hand, the "closed pores" refer to voids that exist inside the magnesium oxide particles and that do not allow the epoxy resin to penetrate when the magnesium oxide powder is embedded in epoxy resin under the aforementioned conditions (i.e., voids whose edges are surrounded by white highlights in image analysis processing). In the present disclosure, the "particles" contained in the magnesium oxide powder refer to magnesium oxide particles. In other words, the aforementioned "particle groups" refer to magnesium oxide particle groups.

[0019] The present inventors conducted research focusing on the voids inside magnesium oxide particles and found that, when the ratio (R) of the area of ​​open pores in a particle group obtained by image analysis under specific conditions (hereinafter sometimes referred to as "ratio (R)") is a certain value or less, low viscosity and high thermal conductivity can be achieved when the powder is filled into a resin. Even when only the magnesium oxide powder is filled into a resin, such powder is less likely to increase in viscosity, making it possible to prepare a low-viscosity resin composition. Magnesium oxide powder that can achieve such a ratio (R) of open pores also has a small absolute number of open pores present inside the particles. The powder containing a particle group having the ratio (R) of open pores of 9.0% or less can be achieved, for example, by preparing magnesium oxide powder by any method and then calcining the magnesium oxide powder at a temperature of 1500°C or higher for 2 hours or more to reduce the number of open pores present inside the magnesium oxide particles.

[0020] FIG. 1 is a photograph obtained by image processing an arbitrary particle group 100 of the magnesium oxide powder of Example 1 under the above-described conditions. The particle group 100 in FIG. 1 includes a plurality of magnesium oxide particles. Here, magnesium oxide particles 10-11 and the open pores 20-21 and closed pores 30 contained therein will be described. In FIG. 1, the magnesium oxide particles 10-11 are covered with an epoxy resin 40. The magnesium oxide particle 10 contains open pores 20 and 21, which are depicted in the same dark color as the epoxy resin 40. Meanwhile, the magnesium oxide particle 11 contains closed pores 30, which are surrounded by a white border. The open pores 21 and closed pores 30 are both large voids present inside the particles, but the voids of the magnesium oxide particle 10 are open pores because they are impregnated with the epoxy resin 40. Meanwhile, the voids of the magnesium oxide particle 11 are closed pores because they are not impregnated with the epoxy resin 40. It has been conventionally believed that large voids located exactly in the center of magnesium oxide particles result from the unevenness of the particle surface or the particle shape, and are not open pores (i.e., pores that are connected to the particle surface). The present inventors have discovered that large voids inside magnesium oxide particles can sometimes become open pores, and that by controlling the proportion of open pores present in the entire particle group, including the large open pores, to a certain value or less, a resin composition with a lower viscosity can be prepared even when only magnesium oxide powder is blended into a resin.

[0021] In one embodiment, from the viewpoint of easily obtaining a resin composition that, when filled into a resin, achieves both low viscosity and high thermal conductivity, the ratio (R) is preferably 7.5% or less, more preferably 6.0% or less, and even more preferably 5.0% or less. Furthermore, the inventors of the present application have found that if the ratio (R) of open pores is too low, the bulk of the filler becomes smaller, reducing contact between fillers in the compound and thereby decreasing thermal conductivity. Therefore, from the viewpoint of easily achieving higher thermal conductivity, the ratio (R) is preferably 0.1% or more. That is, from the viewpoint of easily achieving both low viscosity and high thermal conductivity, the ratio (R) of open pores of the particle group is preferably 0.1 to 9.0%, more preferably 0.1 to 7.5%, and even more preferably 0.1 to 5.0%.

[0022] <Content of Particle Groups> In the powder according to the first embodiment, "containing particle groups having a ratio (R) of open pores of 9.0% or less" means that when any location on a cross section of a sample obtained from the powder according to the first embodiment is observed under SEM, one or more images containing particle groups having a ratio (R) of open pores of 9.0% or less are obtained. In a preferred embodiment, SEM observation and image processing are performed 10 times at different locations on the cross section of the sample, and the average value (R) of the ratio of open pores of the particle groups in each image is calculated. ａｖｅ． ) is 9.0% or less.

[0023] In one embodiment, the content of particle groups in the magnesium oxide powder having a ratio (R) of 9.0% or less is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The content of the particle groups may be 100%. By including 80% or more of particle groups having an open pore ratio (R) of 9.0% or less in the powder, a resin composition with a lower viscosity is more likely to be obtained when the powder according to the first embodiment is filled into a resin. The "content of particle groups having a ratio (R) of 9.0% or less" in the powder is calculated by calculating the ratio (R) for particle groups at any 10 locations on the cross section of the sample and deriving the number of particle groups having a ratio (R) of 9.0% or less. In other words, if there are five particle groups having a ratio (R) of 9.0% or less, the content of the particle groups in the powder is considered to be 50%. Similarly, if the ratio (R) of all particle groups at any 10 locations is 9.0% or less, the content of particle groups with a ratio (R) of 9.0% or less in the powder is taken to be 100%.

[0024] <Median Diameter (D50)> The median diameter (D50) (hereinafter sometimes referred to as "D50") of the magnesium oxide powder according to the first embodiment is preferably 30 to 150 μm, and more preferably 40 to 140 μm. The D50 of the powder according to the first embodiment refers to the median diameter (D50) at which the cumulative value corresponds to 50% in a volume-based particle size distribution measured by a laser diffraction light scattering method. The cumulative particle size distribution is expressed by a distribution curve with the particle diameter (μm) on the horizontal axis and the cumulative value (%) on the vertical axis. Specifically, it can be measured under the following conditions. (Conditions for Measuring Median Diameter) The median diameter (D50) of the powder is determined by measuring the volume-based particle size distribution using a laser diffraction particle size distribution analyzer (for example, a product name "LS 13 320" manufactured by Beckman Coulter, Inc. or a product name "MT3300EXII" manufactured by Microtrackbell Corporation). First, 50 cm ３1 g of pure water and 0.1 g of powder are added, and a dispersion treatment is carried out for 60 seconds using an ultrasonic homogenizer (for example, Microtec Nichion Co., Ltd., product name "Smurt NR-50M (titanium alloy tip φ3 (NS-50M-MT3))"). The dispersion of the dispersed powder is added drop by drop using a dropper to the laser diffraction particle size distribution measuring device, and measurement is carried out 30 seconds after the addition of a predetermined amount. The refractive index of water is 1.33, and the refractive index of the powder is 1.74. From the obtained particle size distribution, the median diameter (D50) at a cumulative frequency of 50% is determined.

[0025] <Specific surface area (BET)> The specific surface area (BET) of the powder according to the first embodiment is 0.1 m ２ / g or less is preferable, and 0.1m ２ / g is more preferable, and 0.09m ２ / g or less is even more preferable. The powder according to the first embodiment contains particle groups with a ratio (R) of 9.0% or less, and furthermore, has a smaller absolute number of open pores, so the specific surface area (BET) of the powder is likely to be small. Such powder is likely to achieve low viscosity and high thermal conductivity when filled into a resin. The specific surface area (BET) can be measured by the following method. (Method for Measuring Specific Surface Area (BET)) 1 g of powder is filled into a measurement cell of a fully automatic specific surface area measuring device (for example, manufactured by Mountech, product name "Macsorb (registered trademark) HM model-1201", BET one-point method), and the specific surface area is measured. The degassing conditions before measurement can be 200°C and 10 minutes. Furthermore, helium can be used as the carrier gas, and nitrogen (mixed concentration: 30.5%) can be used as the adsorption gas.

[0026] <Average circularity> The average circularity of the powder according to the first embodiment may be 0.75 or more, 0.80 or more, 0.85 or more, or 0.90 or more. If the average circularity of the powder is 0.75 or more, the powder tends to be easily filled into the resin, and a resin composition with a lower viscosity is easily obtained. The average circularity of the powder can be measured by the following method. (Method for measuring average circularity) The powder is fixed with carbon tape and coated with osmium. Thereafter, a scanning electron microscope (for example, manufactured by JEOL Ltd., product name "JSM-7001F SHL") is used to photograph the particles constituting the powder at a magnification of 100 to 500 times, and an image analyzer (for example, manufactured by Nippon Roper Co., Ltd., product name "Image-Pro Premier Ver. 9.3") is used to calculate the projected area (Ap) and projected perimeter (L) of the particles, and then the circularity is calculated using the following formula (1). The circularity is calculated for any 200 particles, and the average value thereof is taken as the average circularity. Circularity=4πAp / L ２ ...(1)

[0027] <Apparent Density> In one embodiment, the apparent density of the powder is preferably 3.2 g / mL or more but less than 3.6 g / mL, more preferably 3.25 to 3.5 g / mL, and even more preferably 3.3 to 3.4 g / mL. The powder according to the first embodiment tends to have a relatively low apparent density due to an increase in void content caused by the closure of open pores (the generation of closed pores). Such powders are likely to achieve the effects of reduced viscosity due to the reduction in open pores and improved thermal conductivity due to the increase in bulk. The apparent density of the powder can be measured using a dry densitometer using helium.

[0028] The magnesium oxide powder according to the first embodiment is also characterized by a small number of open pores present inside each particle. In one embodiment, in a particle group having an open pore ratio (R) of 9.0% or less, the average number of open pores present inside each particle of the particle group is preferably 10 or less. The average value is calculated by performing image processing under the above-mentioned conditions, counting the number of open pores for each particle, calculating the total number, and dividing this total number by the number of particles present in the image.

[0029] [Method for producing magnesium oxide powder] A second embodiment of the present disclosure is a method for producing magnesium oxide powder according to the first embodiment. The production method according to the second embodiment includes calcining raw material magnesium oxide powder at 1500°C or higher for 2 hours or more to reduce the number of open pores inside the magnesium oxide particles contained in the raw material magnesium oxide powder (step (i)). Hereinafter, the raw material magnesium oxide powder will be referred to as the "raw material powder" and described in detail.

[0030] <Raw material powder> As the raw material powder, magnesium oxide powder prepared by any method can be used. In one embodiment, the raw material powder may be magnesium oxide powder obtained by calcining magnesium hydroxide powder. Specifically, magnesium hydroxide powder is calcined to obtain magnesium oxide, and then the magnesium oxide powder is dispersed in a liquid and spray-dried. The magnesium oxide granules thus obtained can be calcined to form the raw material powder.

[0031] The median diameter (D50) of the raw material powder is not particularly limited. In one embodiment, when the median diameter (D50) of the magnesium oxide powder to be finally obtained is adjusted to the range of 30 to 150 μm, it is preferable to use a raw material powder having a median diameter (D50) in the same range. The median diameter (D50) of the raw material powder can also be measured by the same method as for the magnesium oxide powder described above.

[0032] The average circularity of the raw material powder is not particularly limited. From the viewpoint of ensuring flowability by making the average circularity of the magnesium oxide powder finally obtained 0.75 or more, the average circularity of the raw material powder may be 0.80 or more. The average circularity of the raw material powder can also be measured by the same method as that for the magnesium oxide powder described above.

[0033] (Step (i)) The production method according to the second embodiment includes calcining the raw material powder at 1500°C or higher for two hours or more to reduce the number of open pores inside the magnesium oxide particles contained in the raw material powder. The temperature at which the raw material powder is calcined is preferably 1500 to 1650°C, more preferably 1500 to 1600°C, from the viewpoint of reducing the number of open pores and making it easier to obtain a powder containing particle groups with a ratio (R) of 9.0% or less. Furthermore, from the above viewpoint, the calcination time is preferably 2 to 8 hours, more preferably 2 to 6 hours. The present inventors have found that calcining the raw material powder at the above calcination temperature and for the above calcination time can effectively reduce the number of open pores inside the magnesium oxide particles contained in the raw material powder. The magnesium oxide powder obtained by this method has a small number of open pores inside the particles, and as a result, the powder contains particle groups with an open pore ratio (R) of 9.0% or less.

[0034] In one embodiment, reducing the number of open pores inside the magnesium oxide particles (step (i)) preferably includes reducing the ratio (r1) of open pores in the particle group contained in the raw material powder (hereinafter, sometimes referred to as "ratio (r1)") by 10% or more. Here, the ratio (r1) of open pores is the ratio of the total area (b1) of open pores present in all particles to the total area (a1) of all particles present in an observed image when the raw material powder before sintering is observed with a scanning electron microscope under the above conditions. The reduction rate of the ratio (r1) of open pores can be calculated using the following formula: Reduction rate of the ratio (r1) of open pores = (1 - (ratio (R) / ratio (r1)) × 100 (%). In one embodiment, step (i) may include reducing the ratio (r1) of open pores to 88% or less, or may include reducing the ratio (r1) of open pores to 86% or less.

[0035] The method for firing the raw material powder is not particularly limited, and for example, an electric furnace, a gas furnace, etc. may be used. Furthermore, firing is preferably carried out in an air atmosphere.

[0036] According to the manufacturing method of the second embodiment, magnesium oxide powder containing magnesium oxide particles with few open pores can be produced without depending on the raw material powder preparation method. For example, in Patent Document 1, the porosity inside the magnesium oxide particles is reduced by adding a certain amount of boron or iron when producing the magnesium oxide powder. However, this method requires controlling the amount of boric acid or iron added so that the boron and iron contents in the final magnesium oxide powder remain constant. Furthermore, the inclusion of boron or iron poses a problem of reduced thermal conductivity of the magnesium oxide powder itself. The manufacturing method of the second embodiment involves further calcining the raw material powder prepared by any method at 1500°C or higher for two hours or more to reduce the number of open pores inside the particles, thereby simplifying the manufacturing steps. Furthermore, since no impurities are particularly required, magnesium oxide powder with higher thermal conductivity can be obtained. Furthermore, in conventional methods, the porosity inside the magnesium oxide particles is adjusted during the raw material powder production process, making it difficult to control the median diameter of the final magnesium oxide powder. Furthermore, the porosity tends to increase as the median diameter increases. According to the production method of the second embodiment, by changing the median diameter of the raw material powder, it is possible to prepare magnesium oxide powders having various median diameters and containing particle groups with a small ratio of open pores (R). Furthermore, even if the magnesium oxide powder has a large median diameter (for example, a magnesium oxide powder with a median diameter (D50) of more than 100 μm), it is possible to prepare powders with a small ratio of open pores (R).

[0037] The proportion of impurities such as boron and iron contained in the finally obtained magnesium oxide powder is not particularly limited. As described above, from the viewpoint that the fewer impurities, the better the thermal conductivity. The boron content in the magnesium oxide powder may be less than 600 ppm. Similarly, the iron content in the magnesium oxide powder may be less than 500 ppm. The contents of impurities such as boron and iron in the magnesium oxide powder may be adjusted when preparing the raw material powder. Furthermore, magnesium oxide powder having the contents of impurities such as boron and iron within the above ranges may be used as the raw material powder.

[0038] Furthermore, the production method according to the second embodiment may include a step of classifying the magnesium oxide powder after reducing the number of open pores in order to obtain magnesium oxide powder having a desired median diameter (D50) and particle size distribution. Examples of classification methods include classification using a sieve, as well as liquid cyclone and air classification.

[0039] Furthermore, in order to improve the moisture resistance of the magnesium oxide powder finally obtained, the production method according to the second embodiment may include subjecting the obtained magnesium oxide powder to a surface treatment after reducing the number of open pores. The surface treatment is not particularly limited, and examples thereof include colloidal silica, silane-based coupling agents, titania sol, titanate-based coupling agents, phosphorus compounds, alumina sol, aluminate-based coupling agents, and zirconium-based coupling agents. These surface treatment agents may be used alone or in combination of two or more.

[0040] [Mixed Powder] A third embodiment of the present disclosure relates to a mixed powder. The mixed powder according to the third embodiment includes the magnesium oxide powder according to the first embodiment and an inorganic powder other than the magnesium oxide powder. In the mixed powder according to the third embodiment, the inorganic powder to be combined with the magnesium oxide powder according to the first embodiment is not particularly limited, and any inorganic powder can be used. Examples include oxide powders such as titanium oxide powder, silica powder, zirconia powder, alumina powder, and magnesium oxide powder other than the magnesium oxide powder according to the first embodiment; sulfide powders such as barium sulfate powder, iron sulfate powder, and copper sulfate powder; hydroxide powders such as aluminum hydroxide powder and magnesium hydroxide powder; nitride powders such as boron nitride powder, aluminum nitride powder, and silicon nitride powder; carbide powders such as silicon carbide powder; and mineral powders such as kaolinite powder, talc powder, natural mica powder, and synthetic mica powder. These may be used alone or in combination of two or more types. Furthermore, these inorganic powders may be surface-treated with the aforementioned surface treatment agent, if necessary.

[0041] The magnesium oxide powder according to the first embodiment can prepare a resin composition with low viscosity and high thermal conductivity even when blended alone in a resin. Therefore, it is possible to set the ratio of the magnesium oxide powder in the mixed powder according to the third embodiment high. In one embodiment, the ratio of the magnesium oxide powder to the total mass of the mixed powder may be in the range of 1 to 99 mass%.

[0042] In one embodiment, the mixed powder may be a mixed powder of the magnesium oxide powder according to the first embodiment and a magnesium oxide powder other than the magnesium oxide powder (i.e., a magnesium oxide powder including a particle group having an open pore ratio (R) of more than 9.0%). The magnesium oxide powder according to the first embodiment can achieve low viscosity and high thermal conductivity when filled into a resin. Therefore, the powder according to the first embodiment may be combined with a general magnesium oxide powder as a viscosity adjuster and / or thermal conductivity adjuster to form a mixed powder. In this case, the ratio of the powder according to the first embodiment in the mixed powder may be adjusted within a range of 1 to 99 mass%.

[0043] The mixed powder may contain any component other than the magnesium oxide powder according to the first embodiment and the inorganic powder, such as a resin powder or an organic-inorganic hybrid powder.

[0044] [Resin Composition] A fourth embodiment of the present disclosure is a resin composition. The resin composition according to the fourth embodiment includes the magnesium oxide powder according to the first embodiment and at least one resin selected from a thermoplastic resin and a thermosetting resin. The resin composition according to the fourth embodiment can achieve both low viscosity and high thermal conductivity.

[0045] The content of the powder in the resin composition is not particularly limited and can be adjusted appropriately depending on the purpose. The powder according to the first embodiment can prepare a low-viscosity resin composition even when only the powder is filled into a resin. Therefore, the amount of powder in the resin composition can be adjusted as desired to obtain desired physical properties. For example, when the resin composition is used for insulating materials or high-heat dissipation components, the powder may be blended in a range of 1 to 99% by mass, more preferably 10 to 90% by mass, relative to the total mass of the resin composition.

[0046] <Resin> The resin composition according to the fourth embodiment contains at least one resin selected from thermoplastic resins and thermosetting resins. More specifically, examples of the resin include polyethylene resins; polypropylene resins; epoxy resins; silicone resins; phenolic resins; melamine resins; urea resins; unsaturated polyester resins; fluororesins; polyamide-based resins such as polyimide resins, polyamideimide resins, and polyetherimide resins; polyester-based resins such as polybutylene terephthalate resins and polyethylene terephthalate resins; polyphenylene sulfide resins; wholly aromatic polyester resins; polysulfone resins; liquid crystal polymer resins; polyethersulfone resins; polycarbonate resins; maleimide-modified resins; ABS resins; AAS (acrylonitrile-acrylic rubber-styrene) resins; AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins; hydrocarbon-based elastomer resins; polyphenylene ether resins; and aromatic polyene-based resins. These may be used alone or in combination of two or more.

[0047] The resin composition according to the fourth embodiment may contain a curing agent, a curing accelerator, a release agent, a coupling agent, a colorant, a flame retardant, an ion scavenger, and the like, as long as the effects of the present invention are not impaired.

[0048] In one embodiment, the thermal conductivity of a resin composition containing only the powder according to the first embodiment, measured under the following conditions, may be 3.0 to 6.0 W / m·K, or may be 3.2 W / m·K or more and less than 4.0 W / mK. The powder according to the first embodiment can prepare a resin composition with high thermal conductivity even when only the powder is blended into a resin. (Conditions for measuring thermal conductivity) A powder is prepared by mixing magnesium oxide powder and spherical alumina powder (a mixture of DAW-10, DAW-03, and ASFP-40 manufactured by Denka Co., Ltd., with a volume ratio of (DAW-10):(DAW-03):(ASFP-40) = 3:25:15). The mixed powder is added to an epoxy resin (e.g., Mitsubishi Chemical Corporation, product name "JER828") to a loading of 70 vol%, and the mixed powder is dispersed and air bubbles are removed using a rotary / revolution vacuum mixer (e.g., Thinky Corporation, product name "Awatori Rentaro (registered trademark) ARV-310P"). The resulting mixture is poured into a 2 cm x 2 cm x 0.6 cm silicone mold and pressed using a heated press under a schedule of 3 kN, 80°C for 1 hour, 5 kN, 150°C for 1 hour, and 7 kN, 200°C for 0.5 hours to produce an epoxy resin molded product containing the mixed powder. The obtained epoxy resin molded product sample is processed into a disk-shaped sample with a diameter of 10 mm and a thickness of 1 mm to prepare an evaluation test piece. The surface of the evaluation test piece is further blackened using a carbon spray (for example, product name "Graphite" manufactured by Netsch Japan Co., Ltd.), and then the thermal diffusivity is measured using a thermal diffusivity measuring device (for example, product name "LFA447 Nanoflash" manufactured by Netsch Japan Co., Ltd.). At this time, the measurement sample temperature is set to 25°C, and the voltage applied to the Xe lamp is set to 247V. The thermal conductivity is calculated from the obtained thermal diffusivity. The thermal conductivity H (unit [W / mK]) is calculated by multiplying the thermal diffusivity T (unit [m ２ / s]), density D (unit [kg / m ３The density D is calculated from the measured values ​​of the density (H) and specific heat capacity C (unit: [J / kg K]) using the formula H = T x D x C. The density D is calculated by measuring the weight and volume of the sample. The specific heat capacity C is set to 940 [J / kg K] (magnesium oxide powder) and 1250 [J / kg K] (epoxy resin), respectively, and the specific heat capacity of spherical alumina is set to 770 [J / kg K].

[0049] In one embodiment, the viscosity of a resin composition containing only the powder according to the first embodiment, measured under the following conditions, is preferably less than 900 Pa·s / 25°C, more preferably 800 Pa·s / 25°C or less, and even more preferably 600 Pa·s / 25°C or less. The powder according to the first embodiment can prepare a low-viscosity resin composition even when only the powder is blended into a resin. (Conditions for Viscosity Measurement) The viscosity of a resin composition consisting of 60 vol% of a bisphenol A-type liquid epoxy resin (epoxy equivalent: 184 to 194) and 40 vol% of the powder is measured using a rotational rheometer at a shear rate of 1.0 / s, a plate shape of a circular flat plate (10 mmφ), a sample thickness of 1 mm, and a temperature of 25±1°C.

[0050] <Method for producing resin composition> The method for producing the resin composition according to the fourth embodiment is not particularly limited, and the resin composition can be produced by stirring, dissolving, mixing, and dispersing predetermined amounts of each material. The apparatus for mixing, stirring, dispersing, etc., of these mixtures is not particularly limited, and examples that can be used include a mortar and pestle machine equipped with a stirring and heating device, a three-roll mill, a ball mill, a planetary mixer, etc. These apparatuses may also be used in appropriate combination.

[0051] As described above, the resin composition containing the magnesium oxide powder according to the first embodiment can achieve both high thermal conductivity and low viscosity. Such a resin composition has low viscosity, and therefore is excellent in processability and workability.

[0052] Another embodiment of the present disclosure is a method for reducing the number of open pores inside magnesium oxide particles contained in magnesium oxide powder, the method comprising calcining the magnesium oxide powder at 1500° C. or higher for 2 hours or more. In the embodiment, the calcination is preferably carried out so that the value of ((1−ratio(2) / ratio(1))×100(%)) is 10% or more, where (1) is the ratio of open pores in the magnesium oxide particles contained in the magnesium oxide powder before calcination and (2) is the ratio of open pores in the magnesium oxide particles contained in the magnesium oxide powder after calcination.

[0053] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following description.

[0054] Example 1 and Comparative Example 1 A magnesium oxide powder was prepared under the following conditions to obtain raw material powder 1. Magnesium hydroxide powder was calcined in an electric furnace under atmospheric pressure at 1000°C for 1 hour to obtain a magnesium oxide powder. Distilled water was added to the magnesium oxide powder to obtain a 60% by mass aqueous dispersion of magnesium oxide powder. This dispersion was granulated by a spray-drying method to obtain granular magnesium oxide raw material powder 1. Raw material powder 1 was calcined at 1500°C for 4 hours to obtain the magnesium oxide powder of Example 1. The open pore ratio (R), median diameter (D50), specific surface area (BET), apparent density, and average circularity of raw material powder 1 (Comparative Example 1) and the calcined magnesium oxide powder (Example 1) were measured under the following conditions. The viscosity and thermal conductivity of a resin composition containing the magnesium oxide powder were also evaluated under the following conditions. The results are shown in Table 1.

[0055] <Open Pore Ratio (R)> First, pretreatment was performed under the following conditions, followed by observation and image processing using a scanning electron microscope. Pretreatment: Magnesium oxide powder (0.1 g) was mixed with a two-component thermosetting epoxy resin (manufactured by Gatan, product name "G2") (resin:curing agent = 10:1). The mixture was then vacuum-impregnated (0.1 MPa, approximately 20 minutes) using a vacuum impregnation device (manufactured by Buhler ITW Japan, product name "Cast N1000"). The vacuum-impregnated epoxy resin containing magnesium oxide powder (hereinafter referred to as "sample solution") was poured into an embedding plate. The embedding plate was placed on a hot plate and heated at 110°C for 2 hours to harden the sample solution. The sample liquid after hardening (hereinafter referred to as "hardened sample") was attached to a cross-section processing device (ion milling device (e.g., Hitachi High-Tech Corporation, product name "IM4000PLUS")), and subjected to broad ion beam processing (accelerating voltage: 4 kV, processing time: 5 hours) to prepare a cross-section sample.

[0056] Observation by Scanning Electron Microscope The cross-sectional sample was fixed to a sample stage for SEM observation, and the sample stage was attached to a holder for SEM observation. The SEM observation holder was then introduced into a field emission SEM (manufactured by JEOL Ltd., product name "JSM-7001F") and SEM observation was performed (acceleration voltage: 15 kV, WD: 10 mm). An arbitrary particle group in the cross-sectional sample was observed at 500x magnification to obtain an image.

[0057] Image Processing The observation images obtained above were analyzed using image analysis software (product name "Image Pro Premier" manufactured by MEDIA CYBERNETICS). First, the observation images were binarized using the image analysis software. Among the voids present in the particle group in the observation image, voids depicted in the same dark color as the epoxy resin were judged to be "open pores," and voids surrounded by a white highlight were judged to be "closed pores." Furthermore, in the particle group present in the observation image, the interface with the epoxy resin of the part corresponding to the particle was circled using the image analysis software, and the total area (A) was calculated. Furthermore, among the voids inside each particle, the interface with the particle of the part (open pore) depicted in the same dark color as the epoxy resin was circled using the image analysis software, and the total area (B) was calculated. Furthermore, the ratio (R) of open pores in the particle group was calculated as (B) / (A) × 100 (%).

[0058] <Method for measuring median diameter> The median diameter (D50) of the magnesium oxide powder was determined by measuring the volumetric particle size distribution using a laser diffraction particle size distribution analyzer (manufactured by Beckman Coulter, Inc., product name "LS 13 320"). First, 50 cm ３ 0.1% of pure water and 0.1% of powder were added, and dispersion treatment was carried out for 60 seconds using an ultrasonic homogenizer (manufactured by Microtec Nichion Co., Ltd., product name "Smurt NR-50M (titanium alloy tip φ3 (NS-50M-MT3))"). The dispersion of the dispersed powder was added drop by drop using a dropper to the laser diffraction particle size distribution measuring device, and measurement was carried out 30 seconds after the specified amount was added. The refractive index of water was 1.33, and the refractive index of the powder was 1.74. From the obtained particle size distribution, the median diameter (D50) at a cumulative frequency of 50% was determined.

[0059] <Method for measuring specific surface area (BET)> 1 g of powder was filled into the measurement cell of a fully automatic specific surface area measuring device (manufactured by Mountech, product name "Macsorb (registered trademark) HM model-1201", BET one-point method), and the specific surface area was measured. The degassing conditions before measurement were 200°C and 10 minutes. Helium was used as the carrier gas, and nitrogen (mixed concentration: 30.5%) was used as the adsorption gas.

[0060] <Method for measuring average circularity> The powder was fixed with carbon tape and coated with osmium. Thereafter, the particles constituting the powder were photographed at a magnification of 100 to 500 times using a scanning electron microscope (manufactured by JEOL Ltd., product name "JSM-7001F SHL"), and the projected area (Ap) and projected perimeter (L) of the particles were calculated using an image analyzer (manufactured by Nippon Roper Co., Ltd., product name "Image-Pro Premier Ver. 9.3"), and then the circularity was calculated using the following formula (1). The circularity was calculated for any 200 particles, and the average value was taken as the average circularity. Circularity = 4πAp / L ２ ...(1)

[0061] <Method for measuring apparent density> The apparent density of the powder was measured using a dry densitometer (Shimadzu Corporation, product name "Accupyk II 1340"). 8 cc of powder was placed in a measurement cell (10 cc), and the powder density was measured at room temperature (23°C) by the gas substitution method (using helium).

[0062] <Method for measuring viscosity of resin composition> 60% by volume of bisphenol A liquid epoxy resin (epoxy equivalent: 184 to 194, manufactured by Mitsubishi Chemical Corporation, product name "JER828") and 40% by volume of powder were mixed and kneaded using a planetary mixer (manufactured by Thinky Corporation, product name "Awatori Rentaro AR-250", rotation speed: 2000 rpm) to prepare a resin composition. Next, the shear viscosity of the resulting resin composition at 25°C was measured using a rotational rheometer (manufactured by Anton Paar, product name "MCR-302") under the following conditions: Plate shape: circular flat plate 10 mmφ Sample thickness: 1 mm Temperature: 25±1°C Speed: 1.0 / s

[0063] <Method for measuring the thermal conductivity of a resin composition> A powder was prepared by mixing magnesium oxide powder and spherical alumina powder (a mixture of Denka Company, Ltd., product names "DAW-10," "DAW-03," and "ASFP-40"; (DAW-10):(DAW-03):(ASFP-40) = 3:25:15 (volume ratio)) in a volume ratio of 57:43. This mixed powder was added to a liquid epoxy (Mitsubishi Chemical Corporation, product name "JER828") containing a curing agent (4,4-Diaminodiphenylmethane) to a loading of 70 vol%, and the powder was dispersed and air bubbles were removed using a rotary / revolution vacuum mixer (Thinky Corporation, product name "Awatori Rentaro ARV-310P"). The resulting mixture was poured into a 2 cm x 2 cm x 0.6 cm silicone mold and pressed using a heated press under a schedule of 3 kN at 80°C for 1 hour, 5 kN at 150°C for 1 hour, and 7 kN at 200°C for 0.5 hours to obtain an epoxy resin molded body containing the mixed powder. The resulting epoxy resin molded body sample was processed into a disk-shaped sample with a diameter of 10 mm and a thickness of 1 mm to prepare an evaluation specimen. The evaluation specimen was further surface-blackened using a carbon spray (manufactured by Netsch Japan Co., Ltd., product name "Graphite"), and then its thermal diffusivity was measured using a thermal diffusivity measuring instrument (manufactured by Netsch Japan Co., Ltd., product name "LFA447 Nanoflash"). The sample temperature was 25°C and the Xe lamp voltage was 247 V. The thermal conductivity was calculated from the obtained thermal diffusivity. Thermal conductivity H (unit: W / mK) is a function of thermal diffusivity T (unit: m ２ / s]), density D (unit [kg / m ３ The density D was calculated from the measured values ​​of the specific heat capacity C (unit: [J / kg K]) and density D was calculated from the formula H = T x D x C. The specific heat capacity C was calculated using the specific heat capacities of the magnesium oxide powder and resin, which were 940 [J / kg K] (magnesium oxide powder) and 1250 [J / kg K] (epoxy resin), respectively, and the specific heat capacity of the spherical alumina was 770 [J / kg K].

[0064] [Example 2] Raw material powder 1 was heated at 1600°C for 4 hours to obtain a magnesium oxide powder of Example 2. The open pore ratio (R), median diameter (D50), specific surface area (BET), apparent density, and average circularity of the obtained magnesium oxide powder were measured under the same conditions as in Example 1. In addition, the viscosity and thermal conductivity of a resin composition containing the magnesium oxide powder were evaluated under the same conditions as in Example 1. The results are shown in Table 1.

[0065] [Example 3 and Comparative Example 2] Magnesium oxide powder was prepared under the following conditions to obtain raw material powder 2. Anhydrous magnesium chloride was dissolved in distilled water to obtain an approximately 4.0 M magnesium chloride aqueous solution. 25% sodium hydroxide aqueous solution was added to the magnesium chloride aqueous solution to produce magnesium hydroxide, which was then recovered by filtration and water washing. The recovered powder was air-dried and then fired in an electric furnace at 800°C for 1 hour in an air atmosphere to obtain magnesium oxide powder. Distilled water was added to the magnesium oxide powder to obtain a 60% by mass aqueous dispersion of magnesium oxide powder. This dispersion was then granulated by spray drying to obtain granular raw material powder 2 of magnesium oxide. Raw material powder 2 was fired at 1600°C for 4 hours to obtain the magnesium oxide powder of Example 3. Raw material powder 2 was also fired at 1500°C for 1 hour to obtain the magnesium oxide powder of Comparative Example 2. The open pore ratio (R), median diameter (D50), specific surface area (BET), apparent density, and average circularity of the magnesium oxide powders of Comparative Example 2 and Example 3 were measured under the same conditions as in Example 1. In addition, the viscosity and thermal conductivity of the resin composition containing the magnesium oxide powder were evaluated under the same conditions as in Example 1. The results are shown in Table 1.

[0066]

[0067] As shown in Table 1, resin compositions with lower viscosity than the powder of Comparative Example 1 were prepared from Examples 1 to 3, which are magnesium oxide powders according to the first embodiment. Furthermore, the content of particle groups with a ratio (R) of 9.0% or less was 100% in the magnesium oxide powders of Examples 1 to 3. Furthermore, it was found that the production method according to the second embodiment can reduce the ratio of open pores inside the particles in the raw material powder by firing raw material powder prepared by any method at 1500°C or higher for 2 hours or more, thereby obtaining the powder according to the first embodiment. The ratio (R) of open pores in raw material powder 1 of Comparative Example 1 corresponds to the ratio (r1) described above (the ratio of open pores in the raw material powder before firing). Comparison of Comparative Example 1 with Examples 1 and 2 confirmed that the production method according to the second embodiment is a method capable of reducing the ratio (r1) of open pores by 10% or more. Comparison of Example 3 with Comparative Example 2 also confirmed that the production method according to the second embodiment is a method capable of effectively reducing the ratio (r1) of open pores in the raw material powder. The powders of Examples 1 to 3 had lower thermal conductivities than the powder of Comparative Example 1, but because the resin compositions containing the powders of Examples 1 to 3 had low viscosities, it was possible to adjust the thermal conductivity by increasing the proportion of the powder in the resin composition. According to studies by the present inventors, a resin composition containing 50 mass% of the powder of the Examples had a viscosity of approximately 800 Pa·s / 25°C and a thermal conductivity of 5.2 W / mK. These results confirmed that it is possible to provide a magnesium oxide powder and a mixed powder thereof, as well as a resin composition containing the magnesium oxide powder, which, when filled into a resin as a filler, can achieve both high thermal conductivity and low viscosity.

[0068] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of the present disclosure is described below. [1] A magnesium oxide powder comprising a particle group in which, when the magnesium oxide powder is observed with a scanning electron microscope under the following conditions, the ratio (R) of the total area (B) of open pores present within all particles to the total area (A) of all particles present in the observed image is 9.0% or less. (Conditions) The magnesium oxide powder is embedded in an epoxy resin and then hardened. It is then processed using a cross-section processing device to create a sample of the magnesium oxide powder. A cross-section of the sample is observed with a scanning electron microscope at 500x magnification, and the resulting image is analyzed using image analysis software to calculate the total area (A) of all particles present in the observed image. Similarly, the total area (B) of open pores that are connected to the particle surfaces of all particles in the observed image is calculated. Then, the ratio (R) of the total area (B) of the open pores to the total area (A) is determined. [2] The magnesium oxide powder according to [1], wherein the proportion of the particle groups having an open pore ratio (R) of 9.0% or less in the magnesium oxide powder is 80% or more. [3] The magnesium oxide powder according to [1] or [2], wherein the median diameter (D50) of the magnesium oxide powder is 30 to 150 μm. [4] The magnesium oxide powder according to any one of [1] to [3], wherein the average circularity of the magnesium oxide powder is 0.75 or more. [5] The magnesium oxide powder according to [1] to [3], wherein the specific surface area (BET) of the magnesium oxide powder is 0.1 m ２ / g or less. [6] The magnesium oxide powder according to any of [1] to [5], wherein the ratio (R) of open pores in the particle group is 0.1% or more. [7] The method for producing the magnesium oxide powder according to any of [1] to [6], comprising calcining a raw material magnesium oxide powder at 1500°C or higher for 2 hours or more to reduce the number of open pores inside the magnesium oxide particles contained in the raw material magnesium oxide powder. [8] The method for producing the magnesium oxide powder according to [7], wherein reducing the number of open pores inside the magnesium oxide particles comprises reducing the ratio (r1) of open pores in the particle group contained in the raw material magnesium oxide powder by 10% or more, and the ratio (r1) of open pores is the ratio of the total area (b1) of open pores present in all particles to the total area (a1) of all particles present in an observed image when the raw material magnesium oxide powder is observed with a scanning electron microscope under the conditions described above. [9] A mixed powder comprising the magnesium oxide powder according to any one of [1] to [6] and an inorganic powder other than the magnesium oxide powder.

[10] A resin composition comprising the magnesium oxide powder according to any one of [1] to [6] and at least one resin selected from a thermoplastic resin and a thermosetting resin.

[0069] The magnesium oxide powder according to the first embodiment can achieve both low viscosity and high thermal conductivity when filled into a resin, and has industrial applicability as a filler.

[0070] 10, 11: Magnesium oxide particles 20, 21: Open pores 30: Closed pores 40: Epoxy resin 100: Particle group

Claims

1. A magnesium oxide powder comprising a particle group in which, when the magnesium oxide powder is observed by a scanning electron microscope under the following conditions, the ratio (R) of the total area (B) of open pores present in all particles to the total area (A) of all particles present in the observed image is 9.0% or less. (Conditions) The magnesium oxide powder is embedded in an epoxy resin and then hardened. Then, it is processed by a cross-section processing device to prepare a sample of the magnesium oxide powder. The cross-section of the sample is observed by a scanning electron microscope at a magnification of 500 times, and the image obtained is analyzed by image analysis software to calculate the total area (A) of all particles present in the observed image. Similarly, the total area (B) of open pores communicating with the particle surfaces of all particles in the observed image is calculated. Then, the ratio (R) of the total area (B) of the open pores to the total area (A) is obtained.

2. The magnesium oxide powder according to claim 1, wherein the proportion of the particle group having an open pore ratio (R) of 9.0% or less in the magnesium oxide powder is 80% or more.

3. The magnesium oxide powder according to claim 1 or 2, wherein the magnesium oxide powder has a median diameter (D50) of 30 to 150 μm.

4. The magnesium oxide powder according to claim 1 or 2, wherein the average circularity of the magnesium oxide powder is 0.75 or more.

5. The specific surface area (BET) of the magnesium oxide powder is 0.1 m ２ The magnesium oxide powder according to claim 1 or 2, wherein the MgO content is 1 / g or less.

6. The magnesium oxide powder according to claim 1 or 2, wherein the ratio (R) of open pores in the particle group is 0.1% or more.

7. A method for producing magnesium oxide powder according to claim 1 or 2, comprising calcining raw material magnesium oxide powder at 1500°C or higher for 2 hours or more to reduce the number of open pores inside the magnesium oxide particles contained in the raw material magnesium oxide powder.

8. The manufacturing method according to claim 7, wherein reducing the number of open pores inside the magnesium oxide particles comprises reducing the ratio (r1) of open pores in a group of particles contained in the raw material magnesium oxide powder by 10% or more, and the ratio (r1) of open pores is the ratio of the total area (b1) of open pores present in all particles to the total area (a1) of all particles present in an observed image when the raw material magnesium oxide powder is observed with a scanning electron microscope under the above conditions.

9. A mixed powder comprising the magnesium oxide powder according to claim 1 or 2 and an inorganic powder other than said magnesium oxide powder.

10. A resin composition comprising the magnesium oxide powder according to claim 1 or 2 and at least one resin selected from thermoplastic resins and thermosetting resins.

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