JP6238440B2 - Silica-coated metal nitride particles and method for producing the same - Google Patents

Description

  The present invention relates to silica-coated metal nitride particles and a method for producing the same.

  Ceramic particles may be employed in order to improve physical properties of a sealing material for sealing electronic components such as semiconductor devices and a substrate on which the electronic components are disposed. Among the ceramic particles, metal nitrides are known as those having excellent thermal conductivity.

  In recent years, portable wireless communication devices such as mobile phones and smart phones are required to have both high functionality and small size. When the function is increased and the size is reduced, the treatment of the generated heat becomes a problem, and the use of metal nitride particles having excellent thermal conductivity is being studied.

  However, the metal nitride has insufficient water resistance and its application is limited, and the handleability is not sufficient. If the water resistance is increased, it can be expected that the metal nitride particles can be applied to paints and the like, and that the handleability can be improved.

  Therefore, in the prior art, after heating the alumina powder in a nitrogen atmosphere in the presence of carbon powder to obtain an aluminum nitride powder, the obtained aluminum nitride powder is surface-treated in the presence of the residual carbon powder, A method for producing aluminum nitride powder having a step of removing residual carbon powder is disclosed (see Patent Document 1).

JP2012-140260A

  However, it was difficult to say that an aluminum nitride powder having sufficient water resistance was obtained by the conventional manufacturing method.

  The present invention has been completed in view of the above circumstances, and silica-coated metal nitride particles in which silica particles are directly bonded to the surface of metal nitride particles for the purpose of further improving the water resistance of metal nitride, and metal nitriding It is an object to be solved to provide a production method capable of effectively bonding silica particles to the surface of product particles.

(A) The silica-coated metal nitride particles of the present invention that solve the above-mentioned problems are metal nitride particles and the volume average particle size is smaller than that of the metal nitride particles and not less than 5 nm and not more than 200 nm. Silica particles that are sintered on the surface and coated with almost no gaps.

  By bonding between the metal nitride particles and the silica particles by sintering, it is possible to stably develop high thermal conductivity without fear of remaining carbon particles. Conventionally, silica particles having a volume average particle diameter of about 5 nm or more and 200 nm or less are difficult to exist as primary particles when dried, and can only exist as secondary particles aggregated with each other. The present inventors have succeeded in obtaining silica particles that can exist as primary particles in a dry state, and have found that the surface of metal nitride particles can be coated almost without gaps using the silica particles. The metal nitride particles thus coated are firmly bonded while maintaining the surface adhesion state of the silica particles by performing a sintering operation, which means that the silica particles and the metal nitride particles do not melt. (In the present specification, “sintering” and “firing” are used without distinction). Furthermore, it is considered that the silica particles adhering to the surface of the metal nitride particles are firmly bonded by sintering to the adjacent silica particles (the same adhering to the surface of the metal nitride particles). It is done.

  The metal nitride coated in this way has been found to improve water resistance, although the detailed reason is not clear.

The silica-coated metal nitride particles disclosed in (a) above can be added with any one or more of the components (b) to (d) described below.
(B) The silica particles are
The volume average particle size of the primary particles is 200 nm or less, the bulk density is 450 g / L or less,
Sintered ^{one having} a functional group represented by the formula (1): -OSiX ¹ X ² X ³ and a functional group represented by the formula (2): -OSiY ¹ Y ² Y ³ on the surface It is characterized by being.

Silica particles having such a functional group on the surface have particularly low agglomeration properties and can maintain a state of being dispersed to the state of primary particles, so that the surface of metal nitride particles can be coated with almost no gaps. .
(In the above formulas (1) and (2); X ¹ is a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acrylic group; X ² , X ³ Are independently selected from —OSiR ₃ and —OSiY ⁴ Y ⁵ Y ⁶ ; Y ¹ is R; Y ² and Y ³ are each independently selected from R and —OSiY ⁴ Y ⁵ Y ⁶ .Y ⁴ is an R; ^{Y 5} and ^{Y 6} is selected from R and -OSiR ₃ independently;. R is independently selected from alkyl groups of 1 to 3 carbon atoms Incidentally, ^{X 2} , X ³ , Y ² , Y ³ , Y ⁵ , and Y ⁶ are any of the adjacent functional groups X ² , X ³ , Y ² , Y ³ , Y ⁵ , and Y ⁶ , and —O—. May be combined with each other.)
(C) The metal nitride particles have a volume average particle size of 200 μm or less and 0.5 μm or more.
(D) The metal nitride particles are mainly composed of aluminum nitride.
(E) The method for producing silica-coated metal nitride particles that solves the above-described problem is pulverized so that the bulk density is 450 g / L or less with respect to the raw material silica particles whose primary particles have a volume average particle diameter of 200 nm or less. Crushing process;
Mixing the silica particles obtained in the crushing step and the metal nitride particles having a volume average particle size larger than the primary particles of the silica particles to adhere the silica particles to the surface of the metal nitride particles Process,
A heating and sintering step of heating the mixture at 800 ° C. to 1100 ° C. to sinter the metal nitride particles and the silica particles;
Have
The raw silica particles are
A surface treatment step of surface treatment with a silane coupling agent and an organosilazane in a liquid medium containing water;
Removing the liquid medium;
It is processed in the pretreatment process with
The silane coupling agent has three alkoxy groups, a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acrylic group,
The molar ratio of the silane coupling agent to the organosilazane is characterized in that the silane coupling agent: the organosilazane = 1: 2 to 1:10.

  By adopting such a process, the silica particles can be firmly bonded to the surface of the metal nitride particles without agglomeration.

In the manufacturing method (e) described above, the following component (f) can be added.
(F) The surface treatment step includes
A first treatment step of treating with the silane coupling agent;
A second treatment step of treating with the organosilazane,
The second processing step is performed after the first processing step.

  The silica-coated metal nitride particles of the present invention can provide high-performance metal nitride particles having excellent water resistance by appropriately coating the surface of the metal nitride particles with silica particles.

It is a SEM photograph of test sample A-2 in an example. It is a SEM photograph of test sample A-3 in an example. It is a SEM photograph of test sample A-4 in an example.

  The silica-coated metal nitride particles and the production method thereof according to the present invention will be described in detail below based on the embodiments. The silica-coated metal nitride particles of the present invention can be used as a filler in a sealing material for sealing a semiconductor device or the like. When used in a semiconductor device or the like, it can be compressed and solidified as it is, or mixed with a resin material and used as a resin composition. Furthermore, it can be considered that the electronic component is dispersed in a substrate on which electronic components are arranged. It can also be used as a paint by being dispersed in some vehicle. Further, the silica-coated metal nitride particles can be formed into a molded product by solidification molding such as compression. Thermal conductivity can be improved by incorporating the silica-coated metal nitride particles of the present invention.

(Silica-coated metal nitride particles)
The silica-coated metal nitride particles of this embodiment have metal nitride particles and silica particles that are sintered and bonded to the surface of the metal nitride particles. The silica particles are sintered after adhering to the surface of the metal nitride particles so as to cover them almost without any gaps.

  The method for attaching the silica particles to the surface of the metal nitride particles before sintering is not particularly limited, and can be carried out by simply mixing or applying vibration after mixing. The silica particles can be adhered to the surface of the metal nitride particles in a dry state. The mixing ratio of the metal nitride particles and the silica particles is not particularly limited, but is mixed to such an extent that the surface of the metal nitride particles can be covered with almost no gap. Here, it is desirable that the silica particles adhere so that at least one layer covers the surface of the metal nitride particles. The larger the amount of adhesion, such as two layers, three layers, and four layers, the more reliably the water resistance can be improved. . Further, when the amount of adhesion (number of layers) is reduced, the proportion of metal nitride particles is relatively increased, and the thermal conductivity is improved. For example, the content of silica particles can adopt a preferred range with an upper limit of about 10%, 7.5%, 5%, 3%, 1% based on the mass of the metal nitride particles, and a lower limit of 0.001%, About 0.005% and 0.0001% can be adopted as a preferable range.

A desirable value can be calculated as follows for the mixing ratio of the silica particles and the metal nitride particles. First, based on the specific surface area c (m ² / g) of the metal nitride particles and the area Am ² / g that can be coated with 1 g of silica particles, the minimum silica necessary for coating the surface with almost no gap per 1 g of metal nitride particles. The amount of particles (required theoretical coating amount) W (g) can be calculated as c / A (g).

  Here, the value of A can be calculated from the particle size of the silica particles (assuming all the silica particles have the same particle size). When silica particles having a small variation in particle size are employed as the silica particles, if only one layer is densely packed on the plane (on the surface of the metal nitride particles) (closest packed), each silica particle Can be assumed to form an equilateral triangle between adjacent silica particles. Therefore, A can be calculated from the area of this equilateral triangle (which can be calculated from the particle diameter of the silica particles) and the specific gravity of silica (measured values can also be used).

  If the value of r = w / W obtained from the amount of W and the amount of silica particles actually mixed (amount of metal nitride particles mixed per gram) w (g) is 1 The surface of the nitride particles can theoretically be covered without excess or deficiency (in one layer) without gaps. Here, the value of r is preferably 0.1 or more and 10 or less. By making it 0.1 or more, a layer of silica particles having sufficient insulating properties can be formed on the surface of the metal nitride particles, and by making it 10 or less, the fluidity of the silica-coated metal nitride particles produced is reduced. It can be kept in a high state (if there are many silica particles, the silica particles alone aggregate to form independent particles separated from the metal nitride particles, or protrude from the surface of the metal nitride particles to form silica-coated metal nitride particles. May affect the liquidity of the product).

  The metal nitride particles have a volume average particle size larger than the primary particles of the silica particles, and the silica particles adhere to the surface. Silica particles are generally present on the surface of the metal nitride particles without any gaps. Here, “there is almost no gap” means that the value of r described above is 0.1 or more and 10 or less. As a lower limit of the value of r, 0.2, 0.3, 0.5, and 0.75 can be illustrated as preferable values. As the upper limit of the value of r, 8, 6, 5, 43, 2, 1.5 can be exemplified as preferable values.

  Silica particles are bonded to the surface of the metal nitride particles by sintering. Since they are bonded by sintering, the silica particles are not melted and are present on the surface of the metal nitride particles while maintaining the state of primary particles.

  Here, it is desirable that the silica particles substantially exist as primary particles on the surface of the metal nitride particles. Here, the presence of primary particles means particles in a state where the particles are in contact with each other in a SEM photograph.

  The metal nitride particles may be any nitrided metal, but are preferably aluminum nitride and silicon nitride. The metal nitride may be a mixture of a plurality of types of metal nitrides, or may contain a material other than the metal nitride, the main component (50% by mass or more) of the metal nitride.

  The particle size of the metal nitride particles is not particularly limited. For example, as a desirable upper limit of the volume average particle diameter, 200 μm, 150 μm, 100 μm, 80 μm, 60 μm, 50 μm, 40 μm, 30 μm, 20 μm, and 15 μm can be adopted. Examples of the lower limit of the particle size of the metal nitride particles include 0.5 μm, 1.0 μm, 2.0 μm, 3.0 μm, and 5.0 μm.

  Silica particles have a volume average particle size of primary particles of 5 nm to 200 nm. In particular, the bulk density is desirably 450 g / L or less. As a volume average particle diameter, 100 nm, 70 nm, 50 nm, 30 nm, and 20 nm are mentioned as a preferable upper limit. Moreover, 10 nm is mentioned as a preferable minimum. The silica particles preferably have a particle size of 300 nm or less.

  The measurement of the bulk density in this specification is performed using the Tsutsui-Rikagakuki Co., Ltd. product: electromagnetic vibration type | mold beak density measuring device (MVD-86 type | mold). Specifically, after the sample to be measured is put into the upper 500 μm sieve as the sample tank, the sample is dispersed through the two upper and lower 500 μm sieves under electromagnetic acceleration conditions, and dropped into a 100 mL sample container. The mass was measured, and the bulk density was calculated from the mass and volume. In order to prevent a decrease in bulk density due to its own weight, measurement should be performed within 1 hour after dropping.

  Preferred upper limits for the bulk density include 400 g / L, 370 g / L, 350 g / L, 300 g / L, 280 g / L, and 250 g / L. A preferred lower limit is 100 g / L. By setting the bulk density to a value below these upper limits, primary particles can be separated more reliably. Moreover, when the bulk density is set to a value higher than these lower limits, the bulk is small and the handling becomes easy.

  In the silica particles of this embodiment, functional groups containing carbon are introduced on the surface. Since the specific structure of the functional group containing carbon and the method of introducing it onto the surface of the silica particles will be described in detail in the production method described later, description thereof is omitted here.

(Method for producing silica-coated metal nitride particles)
In the method for producing silica-coated metal nitride particles according to the present embodiment, the silica particles produced by performing a crushing step on the raw silica particles are mixed with the metal nitride particles and adhered to the surface (mixing step). This is a method of sintering by baking (heat sintering process). This is a method that can be suitably used for producing the silica-coated metal nitride particles of the present embodiment described above. The raw material silica particles have a large proportion of primary particles bonded together, but the bonds can be separated in the crushing step.

  The mixing step is a step of mixing the silica particles and the metal nitride particles, and is not particularly limited. However, as described above, the silica particles crushed to primary particles in a dry state are mixed with the metal nitride particles as they are to cover the particles. It can be carried out.

  The heating and sintering step is a step of heating the mixture obtained in the mixing step at 800 ° C. or higher and 1100 ° C. or lower to sinter the metal nitride particles and the silica particles. The atmosphere for heating is not particularly limited. Examples include the atmosphere, an inert gas such as argon and helium, and nitrogen gas. Since this is a sintering process, the silica particles and metal nitride particles are not melted (substantially maintaining the original particle morphology. When melting proceeds, the particles are integrated and the original shape is not maintained. In the present specification, “sintering” refers to a state in which particles are bonded without being integrated). Specifically, sintering is advanced without melting by appropriately controlling the combination of the heating temperature and the heating time. As a minimum of heating temperature, 850 ° C and 900 ° C are desirable. Moreover, as an upper limit of heating temperature, 1050 degreeC and 1000 degreeC are desirable. The heating time is not particularly limited as long as it can be appropriately sintered. For example, the lower limit of the heating time can be exemplified by 1 hour, 2 hours, 3 hours, and the upper limit can be exemplified by 24 hours, 18 hours, 12 hours, 8 hours, 6 hours, 5 hours, 4 hours.

  The method for the crushing step is not particularly limited. Preferably, a method of adding an effect of separating the aggregates of the aggregates is preferable, and a method that does not destroy the primary particles constituting the aggregates is preferable. For example, it can be performed by a method similar to pulverization performed in a dry state, and examples thereof include a jet mill, a pin mill, and a hammer mill. It is particularly desirable to use a jet mill. The final stage of the process is judged from the value of the bulk density of the raw silica particles. After the proper bulk density, it can be selected from the range described above. The jet mill is a device that performs pulverization by placing raw material silica particles in an air stream. Any type of jet mill is acceptable. Crushing by a jet mill is desirably performed by a dry method.

  The raw material silica particles have a primary particle size volume average particle size of 200 nm or less. In addition, examples of the upper limit include 100 nm, 70 nm, and 50 nm. The method for producing the raw material silica particles is not particularly limited. For example, a water glass method, an alkoxide method, and a VMC method can be exemplified, and it is desirable to employ the water glass method. The water glass method is a method of precipitating raw material silica particles by performing ion exchange, introduction / desorption of substituents by chemical reaction, control of pH, temperature, and the like on water glass. For example, an aqueous slurry in which nanometer order silica particles are dispersed can be prepared by ion exchange of water glass with an ion exchange resin. The particle diameter of the secondary particles constituting the raw silica particles is not particularly limited, but the volume average particle diameter may be 10 μm or more, 100 μm or more. Furthermore, the raw material silica particles can be produced by dissolving metal silicon in an alkali solution or the like and then depositing it (a method similar to the water glass method).

  A pretreatment process is applied to the preparation of the raw silica particles. The pretreatment process includes a surface treatment process and a process for removing the liquid medium (solidification process). The surface treatment step is a step of performing a surface treatment with a silane coupling agent and an organosilazane in a liquid medium containing water (water, one containing alcohol in addition to water). The silane coupling agent has three alkoxy groups and a phenyl group, vinyl group, epoxy group, methacryl group, amino group, ureido group, mercapto group, isocyanate group, or acrylic group. The molar ratio of the silane coupling agent to the organosilazane is (silane coupling agent) :( organosilazane) = 1: 2 to 1:10.

  The surface treatment step includes a first treatment step for treating with the above-described silane coupling agent and a second treatment step for treating with organosilazane thereafter.

In the surface treatment step, the functional group represented by the formula (1): -OSiX ¹ X ² X ³ and the formula (2): -OSiY ¹ Y ² Y are applied to the silica particles obtained by the above-described method. ³ is a step of obtaining raw material silica particles in which the functional group represented by ³ is bonded to the surface. Hereinafter, the functional group represented by the formula (1) is referred to as a first functional group, and the functional group represented by the formula (2) is referred to as a second functional group.

X ¹ in the first functional group is a phenyl group, vinyl group, epoxy group, methacryl group, amino group, ureido group, mercapto group, isocyanate group, or acrylic group. X ² and X ³ are —OSiR ₃ or —OSiY ⁴ Y ⁵ Y ⁶ , respectively. Y ⁴ is R. Y ⁵ and Y ⁶ are each R or —OSiR ₃ .

Y ¹ in the second functional group is R. Y ² and Y ³ are each —OSiR ₃ or —OSiY ⁴ Y ⁵ Y ⁶ .

The more —OSiR ₃ contained in the first functional group and the second functional group, the more R on the surface of the raw silica particles. As the R (the alkyl group having 1 to 3 carbon atoms) contained in the first functional group and the second functional group increases, the raw silica particles are less likely to aggregate.

Regarding the first functional group, when X ² and X ³ are each —OSiR ₃ , the number of R is minimized. Further, ^{X 2} and ^{X 3} is -OSiY ⁴ Y ⁵ Y ^6, respectively, ^and, if Y 5, ^{Y 6} is -OSiR ₃ respectively, the number of R is maximized.

Regarding the second functional group, when Y ² and Y ³ are each —OSiR ₃ , the number of R is minimized. Further, ^{Y 2} and ^{Y 3} are -OSiY ⁴ Y ⁵ Y ^6, respectively, ^and, if Y 5, ^{Y 6} is -OSiR ₃ respectively, the number of R is maximized.

The number of X ¹ contained in the first functional group, the number of R contained in the first functional group, and the number of R contained in the second functional group are the abundance ratio of R and X ¹ What is necessary is just to set suitably according to the particle size and use of a silica particle.

^{Incidentally, X 2, X 3, Y} 2, Y 3, Y 5, and any of ^{Y 6, X} 2 of the adjacent ^{functionality, X 3, Y 2, Y} 3, Y 5, and any ^{Y 6} You may combine with heel -O-. For example, any one of the first functional group X ² , X ³ , Y ⁵ , and Y ⁶ is the first functional group adjacent to the first functional group X ² , X ³ , Y ⁵ , and It may be bonded to any of Y ⁶ by —O—. Similarly, any of Y ² , Y ³ , Y ⁵ , and Y ⁶ of the second functional group is replaced with Y ² , Y ³ , Y ⁵ , Y ² of the second functional group adjacent to the second functional group. And Y ⁶ may be bonded to each other by —O—. Furthermore, any one of the first functional groups X ² , X ³ , Y ⁵ , and Y ⁶ is the second functional group adjacent to the first functional group, Y ² , Y ³ , Y ⁵ , And Y ⁶ may be bonded to each other by —O—.

In the raw material silica particles, the presence ratio of the first functional groups and second functional groups is 1: 12-1: if 60, the surface of the raw material silica particles and X ¹ and R are present good balance. For this reason, the raw material silica particle whose abundance ratio of the first functional group and the second functional group is 1:12 to 1:60 is particularly excellent in the affinity for the resin and the aggregation suppressing effect. Further, if X ¹ is 0.5 to 2.5 per unit surface area (nm ² ) of the raw silica particles, a sufficient number of first functional groups are bonded to the surface of the raw silica particles, and the first There are also a sufficient number of Rs derived from the functional group and the second functional group. Therefore, also in this case, the affinity for the resin and the aggregation suppressing effect of the raw silica particles are sufficiently exhibited.

In any case, R per unit surface area (nm ² ) of the raw silica particles is preferably 1 to 10. In this case, the balance between the number of X ¹ present on the surface of the raw silica particles and the number of R is improved, and both the affinity for the resin and the aggregation suppressing effect of the raw silica particles are exhibited in a well-balanced manner.

In the raw material silica particles, it is preferable that all of the hydroxyl groups present on the surface of the silica particles are substituted with the first functional group or the second functional group. If the sum of the first functional group and the second functional group is 2.0 or more per unit surface area (nm ² ) of the raw silica particles, the raw silica particles were present on the surface of the silica particles. It can be said that almost all of the hydroxyl groups are substituted with the first functional group or the second functional group.

The raw silica particles have R on the surface. This can be confirmed by an infrared absorption spectrum. Specifically, when the infrared absorption spectrum of the raw silica particles is measured by the solid diffuse reflection method, there is a maximum absorption of C—H stretching vibration at 2962 ± 2 cm ⁻¹ .

  Further, as described above, the raw material silica particles hardly aggregate.

  Note that the raw silica particles can be dispersed again by ultrasonic treatment even if they are slightly agglomerated. Specifically, the raw silica particles can be substantially dispersed to primary particles by irradiating the raw silica particles dispersed in methyl ethyl ketone with ultrasonic waves having an oscillation frequency of 39 kHz and an output of 500 W. The ultrasonic irradiation time at this time may be 10 minutes or less. Whether or not the raw material silica particles are dispersed to the primary particles can be confirmed by measuring the particle size distribution. Specifically, when the methyl ethyl ketone dispersion material of the raw material silica particles is measured with a particle size distribution measuring device such as a microtrack device, and there is a particle size distribution of the raw material silica particles, it can be said that the raw material silica particles are dispersed to primary particles.

  Since the raw silica particles hardly aggregate, they can be provided as raw silica particles that are not dispersed in a liquid medium such as water or alcohol. In this case, since no liquid medium is brought in, it is preferably used as a filler for a resin material.

  Further, since the raw silica particles are difficult to aggregate, they can be easily washed with water.

The raw material silica particles are treated in a step of treating the silica particles with a silane coupling agent and an organosilazane (surface treatment step) in a liquid medium containing water. The silane coupling agent has three alkoxy groups and a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acrylic group (that is, X ¹ described above).

By performing the surface treatment with the silane coupling agent, the hydroxyl group present on the surface of the silica particles is substituted with a functional group derived from the silane coupling agent. The functional group derived from the silane coupling agent is represented by the formula (3): —OSiX ¹ X ⁴ X ⁵ . The functional group represented by the formula (3) is referred to as a third functional group. X ¹ in the third functional group is the same as X ¹ in the functional group represented by the formula (1). X ⁴ and X ⁵ are each an alkoxy group. By surface-treating with organosilazane, the third functional group X ⁴ and X ⁵ are derived from organosilazane —OSiY ¹ Y ² Y ³ (the functional group represented by the formula (2), the second functional group ). When all of the hydroxyl groups present on the surface of the silica particles are not substituted with the third functional group, the hydroxyl groups remaining on the surface of the silica particles are substituted with the second functional group. For this reason, on the surface of the surface-treated raw material silica particles, a functional group represented by the formula (1): -OSiX ¹ X ² X ³ (that is, the first functional group) and a formula (2): -OSiY ^The functional group represented by ¹ Y ² Y ³ is bonded to the functional group (that is, the second functional group). In addition, since the molar ratio of the silane coupling agent and the organosilazane is silane coupling agent: organosilazane = 1: 2 to 1:10, the first functional group and the second functional group in the obtained raw material silica particles are used. The abundance ratio with the functional group is theoretically from 1:12 to 1:60.

In the surface treatment step, the silica particles may be simultaneously surface treated with a silane coupling agent and an organosilazane. Alternatively, the silica particles may first be surface treated with a silane coupling agent and then surface treated with organosilazane. Alternatively, the silica particles may be first surface treated with organosilazane, then surface treated with a silane coupling agent, and then surface treated with organosilazane. In any case, the amount of organosilazane may be adjusted so that all the hydroxyl groups present on the surface of the silica particles are not substituted with the second functional group. The hydroxyl groups present on the surface of the silica particles may all be substituted with the third functional group, or only a part may be substituted with the third functional group, and the other part may be substituted with the second functional group. It may be replaced. All of X ⁴ and X ⁵ contained in the third functional group may be substituted with the second functional group.

A part of organosilazane may be replaced with the second silane coupling agent. As the second silane coupling agent, one having three alkoxy groups and one alkyl group can be used. In this case, X ⁴ and X ⁵ contained in the third functional group are substituted with the fourth functional group derived from the second silane coupling agent. The fourth functional group is represented by formula (4): —OSiY ¹ X ⁶ X ⁷ . Y ¹ is the same R as ^{Y 1} in the second functional ^{group, X 6,} X ⁷ is an alkoxy group or a hydroxyl group, respectively. X ⁶ and X ⁷ contained in the fourth functional group are substituted with the second functional group derived from organosilazane, or are substituted with another fourth functional group. In this case, the amount of R present on the surface of the raw silica particles can be further increased. When a part of the organosilazane is replaced with the second silane coupling agent, it is necessary to surface-treat with the organosilazane again after the surface treatment with the second silane coupling agent. This is because X ⁶ and X ⁷ contained in the fourth functional group are finally substituted with the second functional group derived from organosilazane.

When a part of the organosilazane is replaced with the second silane coupling agent, X ⁴ and X ⁵ contained in the first functional group described above are substituted with the second functional group derived from the organosilazane, Substitution with a fourth functional group derived from the second silane coupling agent. When X ⁴ and X ⁵ are substituted with the fourth functional group, X ⁶ and X ⁷ contained in the fourth functional group are substituted with the second functional group or another fourth functional group. Is replaced by If X ^6, X ⁷ contained in the fourth functional group has been replaced by another fourth functional group, X ^6, X ⁷ contained in the fourth functional groups is substituted with the second functional group The For this reason, the second silane coupling agent is an organosilazane set when the surface treatment is performed only with the first coupling agent and the organosilazane (when the organosilazane is not replaced with the second silane coupling agent). A maximum of 5a / 3 mol can be substituted for the amount (a) mol. The amount of organosilazane required in this case is 8a / 3 mol.

  The alkoxy groups of the silane coupling agent and the second silane coupling agent are not particularly limited, but those having a relatively small carbon number are preferred, and those having 1 to 12 carbon atoms are preferred. Considering the hydrolyzability of the alkoxy group, the alkoxy group is more preferably any one of a methoxy group, an ethoxy group, a propoxy group, and a butoxy group.

  Specific examples of silane coupling agents include phenyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane. 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-phenyl-3 -Aminopropyltrimethoxysilane.

  Any organosilazane may be used as long as it can replace the hydroxyl group present on the surface of the silica particles and the alkoxy group derived from the silane coupling agent with the second functional group described above. preferable. Specific examples include tetramethyldisilazane, hexamethyldisilazane, pentamethyldisilazane, and the like.

  Examples of the second silane coupling agent include methyltrimethoxysilane, methyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, and hexyltriethoxysilane.

  In the surface treatment step, a polymerization inhibitor may be added in order to suppress polymerization of the silane coupling agent or polymerization of the second silane coupling agent. As the polymerization inhibitor, common ones such as 3,5-dibutyl-4-hydroxytoluene (BHT) and p-methoxyphenol (methoquinone) can be used.

  The raw silica particles may be provided with a solidification step after the surface treatment step. The solidification step is a step in which the raw material silica particles after the surface treatment are precipitated with a mineral acid, and the precipitate is washed with water and dried to obtain a solid material of the raw material silica particles. As described above, since general silica particles are very likely to aggregate, it is very difficult to disperse once solidified silica particles. However, since the raw silica particles are difficult to agglomerate, they are difficult to agglomerate even if solidified, and are easily redispersed even if agglomerated. In the washing step, washing is preferably repeated until the electrical conductivity of the extraction water of the raw silica particles (specifically, the water in which the silica particles are immersed at 121 ° C. for 24 hours) is 50 μS / cm or less.

  Examples of the mineral acid used in the solidification step include hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid, and hydrochloric acid is particularly desirable. The mineral acid may be used as it is, but is preferably used as a mineral acid aqueous solution. The concentration of the mineral acid in the aqueous mineral acid solution is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. The amount of the mineral acid aqueous solution can be about 6 to 12 times based on the mass of the raw silica particles to be cleaned.

  The cleaning with the mineral acid aqueous solution can be performed a plurality of times. The washing with the mineral acid aqueous solution is preferably performed after the raw silica particles are immersed in the mineral acid aqueous solution and then stirred. Further, it can be left in the immersed state for 1 to 24 hours, and further for about 72 hours. When it is allowed to stand, stirring can be continued or not stirred. When washing in the mineral acid-containing liquid, it can be heated to room temperature or higher.

  Thereafter, the raw silica particles washed and suspended are collected by filtration and then washed with water. It is desirable that the water used does not contain ions such as alkali metals (for example, 1 ppm or less on a mass basis). For example, ion exchange water, distilled water, pure water and the like. Washing with water is the same as washing with an aqueous mineral acid solution, after the raw silica particles are dispersed and suspended, they can be filtered, or by continuously passing water through the filtered raw silica particles. Is possible. The end of washing with water may be determined by the electrical conductivity of the extracted water described above, or may be the time when the alkali metal concentration in the waste water after washing the raw silica particles becomes 1 ppm or less, It is good also as the time of the alkali metal concentration of extraction water becoming 5 ppm or less. When washing with water, it can be heated to a room temperature or higher.

  Drying of the raw silica particles can be performed by a conventional method. For example, heating or leaving under reduced pressure (vacuum).

  The silica-coated metal nitride particles of the present invention and the production method thereof will be described based on examples. In this example, when mentioning the particle size, the particle size of the secondary particles is described unless there is a description that the particle size of the primary particles.

-Preparation of test sample-Test examples A1 to A6: Adopting aluminum nitride as metal nitride (Test example A-1)
Aluminum nitride powder as metal nitride particles (volume average particle diameter (D50) 1.9 μm, (D90) 3.2 μm, specific surface area 2.6 m ² / g, specific surface area was measured by BET method using nitrogen) .) 1 kg and 50 g of silica particles (manufactured by Admatechs; nanosilica; volume average particle size 10 nm) (16 mg per 1 m ² of surface area of metal nitride particles (for one layer)) were mixed using a rotary mixer. (Mixing process). In this test, r was 1.2. This mixture was heated from room temperature at 20 ° C. per minute in the atmosphere, and after reaching 900 ° C., it was heated and sintered at 900 ° C. for 1 hour (heating and sintering step). The obtained powder was used as silica-coated metal nitride particles of this test example.
Since some of the particles are aggregated after sintering, the particles were easily pulverized by a pulverization operation (jet mill, etc.), and could be easily separated into single particles (silica-coated metal nitride particles).

(Test Example A-2)
The silica-coated metal nitride particles of this test example were produced in the same process as in Test Example A-1, except that the sintering temperature for the mixture (sintering temperature in the heating and sintering process) was 1000 ° C. The obtained test sample was observed by SEM (FIG. 1).

(Test Example A-3)
The silica-coated metal nitride particles of this test example were produced in the same process as in Test Example A-1, except that the sintering temperature for the mixture (sintering temperature in the heat sintering process) was 1200 ° C. The obtained test sample was observed by SEM (FIG. 2).

(Test Example A-4)
The metal nitride particles of this test example were produced in the same process as test example A-2 except that the silica particles were not added. The obtained test sample was observed by SEM (FIG. 3).

(Test Example A-5)
The metal nitride powder itself used in Test Example A-1 was used as the metal nitride particles of this test example.

(Test Example A-6)
The mixture subjected to the heating and sintering step in Test Example A-1 was directly used as silica-coated metal nitride particles in this Test Example.

Test Examples A7 to A9: Silicon nitride is used as the metal nitride (Test Example A-7)
Test except that silicon nitride powder (volume average particle diameter (D50) 3.2 μm, (D90) 6.8 μm, specific surface area 2.0 m ² / g) was used in place of aluminum nitride powder as metal nitride particles. Silica-coated metal nitride particles of this test example were produced in the same process as in Example A-2. The amount of silica particles added was varied according to the specific surface area so that the value of r would be the same.

(Test Example A-8)
The silica-coated metal nitride particles of this test example were produced in the same process as test example A-7, except that the sintering temperature for the mixture (sintering temperature in the heat sintering process) was 1200 ° C.

(Test Example A-9)
The metal nitride powder itself used in Test Example A-7 was used as the metal nitride particles of this test example.

Test examples A10 to A12: As the metal nitride, aluminum nitride having a particle size larger than that used in Test Examples A-1 to A-6 is used (Test Example A-10).
Similar to Test Example A-1, except that aluminum nitride powder (volume average particle diameter (D50) 11.7 μm, (D90) 24.3 μm, specific surface area 4.8 m ² / g) as metal nitride particles was used. The silica-coated metal nitride particles of this test example were produced in the process. The amount of silica particles added was varied according to the specific surface area so that the value of r would be the same.

(Test Example A-11)
The silica-coated metal nitride particles of this test example were produced in the same process as in Test Example A-10 except that the sintering temperature for the mixture (sintering temperature in the heat sintering process) was 1000 ° C.

(Test Example A-12)
The metal nitride powder itself used in Test Example A-10 was used as the metal nitride particles of this test example.

-Water resistance test The electrical conductivity (EC) and pH of the pressure cooker extraction water were measured about the test sample of each test example. The pressure cooker extraction water was obtained by immersing 3.5 g of a test sample in 35 mL of pure water and heating it at 121 ° C. for 24 hours while applying pressure (about 2 atm). The results are shown in Table 1. In Table 1, the temperature and time under “sintering conditions” indicate “sintering temperature” and “sintering time after reaching that temperature”. Test Example A-4 was not evaluated for pressure cooker extracted water, but was evaluated for normal extracted water as described below.

  As is apparent from the table, when the test examples A-1 to A7 are examined, in the test examples A-1 and A-2 which are sintered at 900 ° C. and 1000 ° C., both are only metal nitride powders. It was found that the electrical conductivity was decreased and the water resistance was improved as compared with Test Example A-5 and Test Example A-6 in which the silica particles were added and sintering was not performed. Here, the value of EC is a value that increases according to the degree to which the metal nitride is eluted. In Test Example A-3 in which the sintering temperature was 1200 ° C., it was found that the EC value increased. When the adhesion state of the silica particles is evaluated, the shape of the silica particles can be observed as it is in Test Example A-2 (FIG. 1) as compared with the result of Test Example A-5 (FIG. 3) in which no silica particles are added. In Test Example A-3 (FIG. 2), it seemed to be partially dissolved. That is, it was suggested that sufficient water resistance cannot be exhibited at a high temperature at which dissolution proceeds.

  Next, for Test Example A-4 in which the metal nitride powder was heated alone (1000 ° C., 1 hour), 3.5 g of extracted water (added to 35 mL of pure water, shaken for 30 minutes, and then 30 minutes at 14000 rpm) The EC of 5 minutes of centrifugal separation was 59.1 μS / cm, which was higher than the EC value of 24.6 μS / cm in Test Example A-5 where the metal nitride powder remained as it was. Accordingly, it has been clarified that the addition of silica particles does not provide an effect of improving the water resistance, and that the addition of the silica particles and sintering the coated surface can improve the water resistance.

  For Test Examples A-7 to A-9 employing silicon nitride, Test Example A-7 in which the sintering temperature is 1000 ° C. provides sufficient water resistance, and Test Example A- in which the sintering temperature is 1200 ° C. Since sufficient water resistance was not obtained with No. 8, the cause of the insufficient water resistance improvement effect when 1200 ° C. was selected as the sintering condition was not specific to the type of metal nitride but specific to the silica particles. Was suggested. Therefore, even when aluminum nitride other than silicon nitride or silicon nitride is used as the metal nitride, it is sufficiently suggested that water resistance can be obtained by heating at less than 1200 ° C. when silica particles covering the surface are used. It was.

  Test examples A-10 to A-12 employing aluminum nitride having a larger volume average particle size than Test Examples A-1 to A-6 are sufficient for Test Example A-10 having a sintering temperature of 1000 ° C. Water resistance is obtained, and in Test Example A-11 where the sintering temperature is 1200 ° C., sufficient water resistance was not obtained, so that insufficient water resistance improvement effect when 1200 ° C. was selected as the sintering condition It was suggested that the cause of this is not the particle size of the metal nitride but unique to the silica particles. Therefore, even when the particle size of the metal nitride was changed, it was sufficiently suggested that when silica particles covering the surface were employed, water resistance could be obtained by heating at less than 1200 ° C.

<Manufacture of silica particles (surface-treated)>
[Test Example 1]
(Manufacture of raw silica particles)
Colloidal silica snowtex OS as an aqueous slurry in which silica particles are dispersed in water as an aqueous medium (silica content 20%: manufactured by Nissan Chemical Co., Ltd .: primary particle size is 10 nm) for 100 parts by mass (surface treatment) Treatment step and drying step).

(Surface treatment process)
(1) Preparatory process 40 mass parts of isopropanol was added to 100 mass parts of aqueous slurry, and the dispersion liquid by which a silica particle was disperse | distributed to the liquid medium was obtained by mixing at room temperature (about 25 degreeC).
(2) First Step 1.82 parts by mass of phenyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM103) was added to this dispersion and mixed at 40 ° C. for 72 hours. By this step, the hydroxyl group present on the surface of the silica particles was surface treated with a silane coupling agent. At this time, phenyltrimethoxysilane was calculated and added so that a necessary amount of hydroxyl groups (partially) remained without being surface-treated.
(3) Second Step Next, 3.71 parts by mass of hexamethyldisilazane was added to this mixture and left at 40 ° C. for 72 hours. Through this step, the silica particles were surface-treated to obtain a silica particle material. As the surface treatment progressed, the silica particles that became hydrophobic could no longer exist stably in water and isopropanol, and agglomerated and precipitated. The molar ratio of phenyltrimethoxysilane to mexamethyldisilazane was 2: 5.

(Solidification process)
4.8 parts by mass of 35% aqueous hydrochloric acid solution was added to the mixture obtained in the surface treatment step to precipitate the silica particle material. The precipitate was filtered with a filter paper (5A manufactured by Advantech). The filtration residue (solid content) was washed with pure water and then vacuum-dried at 100 ° C. to obtain a silica particle material solid material (raw material silica particles).
The obtained silica particles had D10 of 8.8 μm, D50 of 124.5 μm, and D90 of 451.9 μm.

(Crushing process)
A crushing step was performed on the obtained raw material silica particles to obtain silica particles of this test example. The crushing step was carried out under the conditions of a crushing pressure of 0.3 MPa and a supply rate of 10 kg / h using a jet mill (manufactured by Seishin Enterprises, model number STJ-200). The obtained silica particles had a bulk density of 251.7 g / L, D10 of 0.8 μm, D50 of 1.8 μm, D90 of 4.0 μm, and primary particles having a volume average particle size of 10 nm.

[Test Example 2]
Instead of the crushing step in Test Example 1, what was spray dried by the spray drying method was used as a test sample of this Test Example. Specifically, 100 parts by mass of the raw material silica particles obtained in the solidification step were dispersed in 200 parts by mass of IPA, which was sprayed at a flow rate of 180 ° C. and 5 L / h and dried. The obtained silica particles had a bulk density of 341.3 g / L.

[Test Example 3]
What was obtained in the solidification step without carrying out the crushing step in Test Example 1 was used as the test sample of this Test Example. The obtained silica particles had a bulk density of 769 g / L, D10 of 8.8 μm, D50 of 124.5 μm, D90 of 451.9 μm, and the volume average particle size of the primary particles was 10 nm.

[Test Example 4]
Commercially available silica particles (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.) were used as test samples in this test example. The silica particles of this test example had a bulk density of 41.0 g / L.

[Test Examples 5 to 7]
In the crushing step in Test Example 1, the bulk density was adjusted by adjusting the crushing pressure and the supply amount. The bulk density of the test sample of Test Example 5 was 271.3 g / L, the test sample of Test Example 6 was 364.6 g / L, and the test sample of Test Example 7 was 249.8 g / L. There was a tendency for the bulk density to increase by increasing the crushing pressure. Although detailed results are not shown, it was found that the surface of the metal nitride particles can be coated almost without gaps as in the above test.

Claims (5)

Metal nitride particles and the volume average particle diameter are sintered to the surface of said metal nitride is 200nm or less and 5nm or less than the particle of the metal nitride particles generally have a silica particles which are no gaps coated ,
The silica particles are
The volume average particle size of the primary particles is 200 nm or less, the bulk density is 450 g / L or less,
Sintered ^{one having} a functional group represented by the formula (1): -OSiX ¹ X ² X ³ and a functional group represented by the formula (2): -OSiY ¹ Y ² Y ³ on the surface silica-coated metal nitride particles is. (In the above formulas (1) and (2); X ¹ is a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acrylic group; X ² , X ³ selected Y 2, ^{Y 3} are each independently from R and -OSiY ⁴ Y ⁵ Y ^6; is -OSiR ₃ and -OSiY ⁴ Y ⁵ Y ⁶ are each independently selected from; ^{Y 1} is R .Y ⁴ is an R; ^{Y 5} and ^{Y 6} is selected from R and -OSiR ₃ independently;. R is independently selected from alkyl groups of 1 to 3 carbon atoms Incidentally, ^{X 2} , X ³ , Y ² , Y ³ , Y ⁵ , and Y ⁶ are any of the adjacent functional groups X ² , X ³ , Y ² , Y ³ , Y ⁵ , and Y ⁶ , and —O—. May be combined with each other.) The silica-coated metal nitride particles according to claim 1, wherein the metal nitride particles have a volume average particle size of 200 μm or less and 0.5 μm or more. The silica-coated metal nitride particles according to claim 1 or 2 , wherein the metal nitride particles are mainly composed of aluminum nitride. A crushing step of crushing so that the bulk density is 450 g / L or less with respect to the raw material silica particles having a volume average particle size of primary particles of 200 nm or less
Mixing the silica particles obtained in the crushing step and the metal nitride particles having a volume average particle size larger than the primary particles of the silica particles to adhere the silica particles to the surface of the metal nitride particles Process,
A heating and sintering step of heating the mixture at 800 ° C. to 1100 ° C. to sinter the metal nitride particles and the silica particles;
Have
The raw silica particles are
A surface treatment step of surface treatment with a silane coupling agent and an organosilazane in a liquid medium containing water;
Removing the liquid medium;
It is processed in the pretreatment process with
The silane coupling agent has three alkoxy groups, a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acrylic group,
The molar ratio of the silane coupling agent to the organosilazane is the silane coupling agent: the organosilazane = 1: 2 to 1:10.
A method for producing silica-coated metal nitride particles, wherein: The surface treatment step includes
A first treatment step of treating with the silane coupling agent;
A second treatment step of treating with the organosilazane,
The method for producing silica-coated metal nitride particles according to claim 4 , wherein the second treatment step is performed after the first treatment step.