WO2023238558A1

WO2023238558A1 - Hollow particle and method for manufacturing same

Info

Publication number: WO2023238558A1
Application number: PCT/JP2023/017107
Authority: WO
Inventors: 司中村; グエンズイフオンダオ; 雄哉樋口
Original assignee: セトラスホールディングス株式会社
Priority date: 2022-06-09
Filing date: 2023-05-02
Publication date: 2023-12-14

Abstract

Provided is a hollow particle having excellent dielectric properties.　This hollow particle of an embodiment includes a shell the inside of which is hollow. The shell is made of silica that includes aluminum. The abundance of aluminum is higher in a first region than in a second region. The first region is located in the shell, inward in the shell thickness direction. The second region is located in the shell, further outside than the first region in the shell thickness direction.

Description

Hollow particles and their manufacturing method

The present invention relates to hollow particles having a hollow shell inside and a method for producing the same.

For example, in the field of information and communication equipment, electronic components such as circuit boards (typically resin components) are required to have lower dielectric constants and lower dielectric loss tangents in order to support communication in high frequency bands. . In order to achieve this, it has been proposed, for example, to include air with a low dielectric constant in the member. Specifically, as disclosed in Patent Document 1 and Patent Document 2, it has been proposed to introduce air using hollow particles.

International Publication No. 2021/171858 International Publication No. 2021/171859

Due to the recent increase in speed and capacity of information communication equipment, hollow particles are required to have further improved dielectric properties.

The present invention was made to solve the above problems, and one of the objects is to provide hollow particles with further improved dielectric properties.

(1) The hollow particles of the present disclosure have shells that are hollow inside. The shell is silica containing aluminum. The amount of aluminum present is greater in the first region than in the second region. The first portion is located inside the shell in the thickness direction of the shell. The second portion is located on the outer side of the shell in the thickness direction of the shell than the first portion.

(2) In the hollow particles of the present disclosure, in the hollow particles described in (1) above, the aluminum content is less than 1% of the components constituting the shell.

(3) In the hollow particles of the present disclosure, in the hollow particles described in (1) or (2) above, the amount of the aluminum present decreases from the inside of the shell toward the outside.

(4) The hollow particles of the present disclosure have an epoxy resin oil absorption of less than 0.6 g/m ² in the hollow particles described in any one of (1) to (3) above.

(5) The hollow particles of the present disclosure are the hollow particles described in any one of (1) to (4) above, in which the shell further contains sodium. The sodium content of the shell is 3000 ppm or less.

(6) In the hollow particles of the present disclosure, in the hollow particles described in any one of (1) to (5) above, the silica is amorphous silica.

(7) In the hollow particles of the present disclosure, in the hollow particles described in any one of (1) to (6) above, the shell has a hollowness ratio of 30% to 95%.

(8) The hollow particles of the present disclosure are the hollow particles described in any one of (1) to (7) above, and the shell has a thickness of 25 nm or more and 500 nm or less.

(9) The method for manufacturing hollow particles of the present disclosure is the method for manufacturing hollow particles described in any one of (1) to (8) above. The above manufacturing method includes the steps of: coating a core particle with a shell-forming material to obtain a core-shell particle; removing the core particle from the core-shell particle to obtain a hollow particle precursor; and forming a shell on the hollow particle precursor. including coating the material.

(10) The method for manufacturing hollow particles of the present disclosure is the method for manufacturing hollow particles described in (9) above, in which the core particles include an alunite-type compound represented by the following general formula (I).
M _a [Al _1-x M' _x ] ₃ (SO ₄ ^2- ) _y (OH) _z・mH ₂ O...(I)
In formula (I), M is at least one cation selected from the group consisting of Na ⁺ , K ⁺ , NH ₄ ⁺ and H ₃ O ⁺ . In formula (I), M' is at least one cation selected from the group consisting of Cu ²⁺ , Zn ²⁺ , Ni ²⁺ , Sn ⁴⁺ , Zr ⁴⁺ and Ti ⁴⁺ . In formula (I), a satisfies 0.8≦a≦1.35. In formula (I), m satisfies 0≦m≦5. In formula (I), x satisfies 0≦x≦0.4. In formula (I), y satisfies 1.7≦y≦2.5. In formula (I), z satisfies 4≦z≦7.

According to embodiments of the present invention, excellent dielectric properties can be achieved.

It is a schematic diagram explaining a long axis and a short axis. FIG. 1 is a cross-sectional view schematically showing a hollow particle in one embodiment of the present invention. 2 is a graph schematically showing an example of changes in Al abundance in the thickness direction of the shell. It is a graph which shows the outline of another example of the change of Al abundance in the thickness direction of a shell. It is a graph which shows the outline of yet another example of the change of Al abundance in the thickness direction of a shell. It is a schematic sectional view of the layered product in one embodiment of the present invention. 1 is a TEM observation photograph of hollow particles of Example 1. 3 is a TEM observation photograph of hollow particles of Example 2. 3 is a TEM observation photograph of hollow particles of Example 3. 2 is a cross-sectional SEM observation photograph of the resin molded article of Example 1.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

(Definition of terms)
Definitions of terms used herein are as follows.
1. Long diameter of particles The long diameter of particles is a value measured using a scanning electron microscope (SEM). The long diameter of the particles is, for example, the average value of the long diameters of randomly selected primary particles, as shown by L in FIG. Note that primary particles are the smallest particles observed by SEM, and are distinguished from aggregated secondary particles.
2. Short diameter of particles The short diameter of particles is a value measured by SEM observation. The short axis of the particle is, for example, the average value of the short axis of randomly selected primary particles, as shown by T in FIG.
3. Aspect Ratio The aspect ratio is a value calculated by dividing the major axis of the particle by the minor axis of the particle.

A. Hollow Particles Hollow particles in one embodiment of the invention have shells that are hollow inside. In other words, a hollow particle has a shell and a space surrounded by this shell. The shell contains silica. Silica is typically amorphous silica. The silica content of the shell is, for example, 95% by weight or more, preferably 97% by weight or more, and more preferably 98% by weight or more.

The shell of the hollow particle contains aluminum (Al). By containing Al, hollow particles with excellent strength (fracture strength) can be obtained. The Al content is preferably 0.1% or more, more preferably 0.2% or more. On the other hand, hollow particles tend to have a high dielectric constant and a high dielectric loss tangent when they contain Al. Therefore, the Al content is preferably less than 1%, more preferably 0.9% or less, still more preferably 0.7% or less, particularly preferably 0.5% or less. According to such a content, the hollow particles can have extremely good dielectric properties. The Al content can be determined, for example, by compositional analysis using inductively coupled plasma emission spectrometry (ICP-AES).

The hollow particles have a larger amount of Al on the inside in the thickness direction of the shell than on the outside in the thickness direction. According to such a form, hollow particles having excellent strength (breaking strength), hollowness ratio, and dielectric properties can be obtained. Specifically, in the hollow particles, a region where a large amount of Al exists tends to soften during firing. That is, hollow particles can lower the firing temperature in the manufacturing process. Moreover, the hollow particles can be made to shrink more on the inside than on the outside of the hollow particle precursor forming the shell by firing due to the region where a large amount of Al exists. Hollow particles can increase the breaking strength due to the region where a large amount of Al exists. In addition, the hollow particles are considered to contribute to improving the hollowness ratio by suppressing softening and shrinking on the outside in the shell, thereby maintaining the particle diameter, and expanding the internal space due to softening and shrinking on the inside. In other words, the hollow particles have different distributions of Al abundance on the outside and inside of the shell, thereby improving the shell strength and hollowness ratio. Since the hollow particles have excellent strength and can be made low dielectric, it is possible to effectively prevent the hollow particles from being broken, for example, when producing a resin composition containing a resin and hollow particles. As a result, the hollow state of the particles is maintained, which can greatly contribute to improving dielectric properties. In addition, if the thickness of the shell of the hollow particle is thin, it becomes easier for Al to be uniformly distributed. In hollow particles, for example, when Al is uniformly distributed, the inside and outside of the shell shrink in the same way, and the particle size tends to become smaller.

FIG. 2 is a cross-sectional view schematically showing a hollow particle in one embodiment of the present invention. In addition, in FIG. 2, hatching is omitted for the cross section of the hollow particle in order to make the figure easier to read. The hollow particle 2 has a shell 4 and a space (hollow part) 6 surrounded by the shell 4. In the shell 4, the amount of Al present in the first region 4a located on the inner side in the thickness direction is greater than the amount of Al present in the second region 4b located on the outer side in the thickness direction than the first region 4a. For example, as shown in FIG. 2, when the first part 4a is located at or near the inner surface of the shell 4 and the second part 4b is located at or near the outer surface of the shell, the hollow particle The amount of Al present in one site 4a is preferably twice or more, more preferably three times or more, the amount of Al present in the second site 4b. The distribution of Al abundance can be determined, for example, by compositional analysis using energy dispersive X-ray spectroscopy (TEM-EDS) using a transmission electron microscope (TEM). In one embodiment, the amount of Al present can be evaluated by the molar ratio of Al to Si.

An example of the distribution of Al abundance in the thickness direction is a form in which the Al abundance decreases continuously from the inside to the outside of the shell. In this case, the manner in which the amount of Al present changes is not particularly limited. For example, Al abundance may decrease linearly with distance from the inner surface of the shell, as shown in Figure 3A. It may also decrease exponentially with distance from the inner surface of the shell, as shown in FIG. 3B. Specifically, the amount of Al present in the hollow particles can be controlled by controlling how the Al raw material is added during the primary silica treatment of the core particles and the secondary silica treatment of the hollow particle precursors. Hollow particles tend to have a higher hollowness ratio when Al abundance decreases linearly compared to when Al is uniformly distributed in the shell. Hollow particles tend to have a higher hollowness ratio when the Al abundance decreases exponentially compared to when it decreases linearly.

Another example of the distribution of Al abundance in the thickness direction is a form in which the Al abundance decreases stepwise from the inside to the outside of the shell. In other words, in the hollow particles, the amount of Al present decreases discontinuously from the inside to the outside of the shell. For example, as shown in FIG. 3C, the hollow particle has a first region 41 in which the amount of Al is constant from the inner surface of the shell to the outside, and the amount of Al in the outside than the first region 41 is constant. An example is a configuration in which the second region 42 has a smaller amount than the first region 41. Note that in FIG. 3C, for convenience, the first region 41 and the second region 42 are shown in a straight line, but the expression that the Al abundance is constant means, for example, that the variation in the Al abundance is 20% or less. do. Further, although FIG. 3C shows an example in which the amount of Al present decreases in two stages, it may be reduced in three or more stages. Hollow particles can enhance the effect of improving strength and hollowness ratio when the Al content decreases stepwise.

The shell of the hollow particles may contain sodium (Na). If the Na content of the hollow particles is too high, it will be difficult to increase the firing temperature in the hollow particle manufacturing process, and the hollow particles will tend to shrink. The content of Na is preferably 3000 ppm or less, more preferably 2000 ppm or less, still more preferably 1500 ppm or less. On the other hand, the content of Na is preferably 100 ppm or more. The Na content can be determined, for example, by composition analysis using atomic absorption spectrometry (AAS).

In the hollow particles, it is preferable that the amount of Na present is greater on the inside in the thickness direction of the shell than on the outside in the thickness direction. It is considered that when a part of Si(4+) is replaced with Al(3+), Na easily enters the hollow particles to fill the electron vacancies. Therefore, it is considered that hollow particles tend to have a large amount of Na in a region where a large amount of Al exists.

In one embodiment, the primary particles of the hollow particles preferably satisfy 1≦D _SL ≦1.5. When the primary particles of the hollow particles satisfy 1≦D _SL ≦1.5, variations between particles can be suppressed and dielectric properties can be made uniform. The primary particles of the hollow particles more preferably satisfy 1≦D _SL ≦1.4, and even more preferably satisfy 1≦D _SL ≦1.3. Here, D _SL is D _75L /D _25L , and D _25L and D _75L are each determined by measuring the long axis of 100 randomly selected primary particles during observation using a scanning electron microscope. The 25th and 75th values are shown when arranged in descending order.

The primary particles of hollow particles preferably satisfy 1≦D _ST ≦1.5, more preferably satisfy 1≦D _ST ≦1.4, and still more preferably satisfy 1≦D _ST ≦1.3. do. Here, D _ST is D _75T /D _25T , and D _25T and D _75T are the sizes obtained by measuring the short axis of 100 randomly selected primary particles during observation using a scanning electron microscope. The 25th and 75th values are shown when they are arranged in descending order.

The aspect ratio of the hollow particles is preferably less than 2, more preferably 1.9 or less. On the other hand, the aspect ratio of the hollow particles is 1 or more, preferably more than 1, and more preferably 1.1 or more.

Hollow particles can have any suitable shape. Examples of the shape of the hollow particles include elliptical, spherical, aggregated, scale-like, plate-like, film-like, cylindrical, prismatic, flattened, go-stone-like, and rice-grain-like. Preferably, the shape of the hollow particles is spherical or grid-shaped. By adopting such a shape, for example, the above _DSL and _DST can be satisfactorily satisfied.

The long axis of the hollow particles is preferably 0.5 μm or more, more preferably 1 μm or more. This is because if the hollow particles have a major axis of 0.5 μm or more, for example, they can fully satisfy the hollowness ratio described below. On the other hand, the length of the hollow particles is preferably 10 μm or less, more preferably 5 μm or less. This is because hollow particles having a major axis of 10 μm or less, for example, can greatly contribute to making the member used smaller or thinner.

The short axis of the hollow particles is preferably 0.25 μm or more, more preferably 0.5 μm or more. This is because if the hollow particles have a short axis of 0.25 μm or more, for example, they can fully satisfy the hollowness ratio described below. On the other hand, the short axis of the hollow particles is preferably 10 μm or less, more preferably 5 μm or less. This is because hollow particles, for example, if the short axis is 10 μm or less, can greatly contribute to making the member used smaller or thinner.

The thickness of the shell of the hollow particles is preferably 25 nm or more, more preferably 50 nm or more, and still more preferably 75 nm or more. According to such a thickness, for example, when producing a resin composition, it is possible to effectively prevent the hollow particles from being broken. On the other hand, the thickness of the shell of the hollow particles is preferably 500 nm or less, more preferably 350 nm or less, and even more preferably 250 nm or less. With such a thickness, the hollowness ratio described below can be fully satisfied, and it can greatly contribute to improving dielectric properties and reducing weight. Note that the thickness of the shell can be measured by TEM observation. For example, it can be determined by measuring the shell thickness of randomly selected hollow particles and calculating the average value of the measured shell thicknesses. The shell thickness of hollow particles may affect the distribution of Al abundance.

The hollowness ratio of the hollow particles is preferably 30% or more, more preferably 40% or more, still more preferably 45% or more, and particularly preferably 50% or more. Such a hollowness ratio can greatly contribute to improving dielectric properties and reducing weight, for example. On the other hand, the hollowness ratio of the hollow particles is preferably 95% or less, more preferably 90% or less, still more preferably 85% or less, particularly preferably 80% or less. According to such a hollowness ratio, for example, when producing a resin composition, it is possible to effectively prevent hollow particles from being broken. Note that the hollowness ratio can be calculated from the major axis and minor axis and the thickness of the shell.

The BET specific surface area of the hollow particles is preferably 30 m ² /g or less, more preferably 20 m ² /g or less, still more preferably 10 m ² /g or less. On the other hand, the BET specific surface area of the hollow particles is, for example, 0.5 m ² /g or more, and may be 1 m ² /g or more.

The cumulative pore volume of the pores of the hollow particles having a diameter of 1 nm to 100 nm is preferably 0.1 cc/g or less, more preferably 0.08 cc/g or less, and even more preferably 0.06 cc/g or less. It is. Such a pore volume can effectively prevent resin from penetrating into the interior of hollow particles in a resin composition, for example, and can greatly contribute to improving dielectric properties. On the other hand, the cumulative pore volume of the pores of the hollow particles having a diameter of 1 nm to 100 nm is, for example, 0.01 cc/g or more.

The cumulative pore volume of the pores of the hollow particles having a diameter of 1 nm to 10 nm is preferably 0.025 cc/g or less, more preferably 0.020 cc/g or less, and even more preferably 0.010 cc/g or less. It is. Such a pore volume can effectively prevent resin from penetrating into the interior of hollow particles in a resin composition, for example, and can greatly contribute to improving dielectric properties. On the other hand, the cumulative pore volume of the pores of the hollow particles having a diameter of 1 nm to 10 nm is, for example, 0.001 cc/g or more.

The density of the hollow particles is preferably 0.90 g/cc or less, more preferably 0.80 g/cc or less. On the other hand, the density of the hollow particles is preferably 0.55 g/cc or more, more preferably 0.60 g/cc or more. With such a density, the hollow particles can maintain shell strength and hollowness.

The dielectric constant of the hollow particles at 25° C. and 10 GHz is preferably 2.2 or less, more preferably 2.0 or less. On the other hand, the dielectric constant of the hollow particles at 25° C. and 10 GHz is, for example, 1.0 or more. The dielectric loss tangent of the hollow particles at 25° C. and 10 GHz is preferably 0.005 or less, more preferably 0.002 or less. On the other hand, the dielectric loss tangent of the hollow particles at 25° C. and 10 GHz is, for example, 0.0001 or more.

The breaking strength of the hollow particles is preferably 10 MPa or more, more preferably 12 MPa or more, still more preferably 14 MPa or more, and particularly preferably 16 MPa or more. Such breaking strength can effectively prevent hollow particles from breaking, for example, when producing a resin composition. As a result, the hollow state of the particles is maintained, which can greatly contribute to improving dielectric properties. On the other hand, the breaking strength of hollow particles is, for example, 800 MPa or less.

The breaking strength of hollow particles can be measured, for example, using a micro compression tester ("MCT-510" manufactured by Shimadzu Corporation) using a length measurement kit and a side observation kit. Specifically, the measurement can be carried out by scattering a very small amount of hollow particles on the lower pressure plate and performing a destructive test on each particle under the following measurement conditions.
・Test force: 0.980mN
・Load speed: 0.0223mN/sec
・Upper pressure indenter: flat surface φ20μm

For example, 10 particles are measured, and the breaking strength Cs is calculated from the measured particle diameter d (mm) of each particle and the value of the test force P (N) at the breaking point. The following formula of JIS R 1639-5 "Method for measuring fine ceramic granule properties - Part 5: Single granule crushing strength" is used to calculate the breaking strength Cs.
Cs=2.48P/πd ²
By calculating the average value of the breaking strength Cs (MPa) of the 10 particles, the breaking strength of the hollow particles can be determined.

The epoxy resin oil absorption amount per gram of hollow particles is preferably 2.3 g or less, more preferably 2.0 g or less. Further, the epoxy resin oil absorption amount of the hollow particles is preferably less than 0.6 g/m ² , more preferably 0.46 g/m ² or less, and even more preferably 0.35 g/m ² or less.

In one embodiment, the hollow particles are preferably surface-treated with any suitable surface treatment agent. Examples of surface treatment agents include higher fatty acids, anionic surfactants, cationic surfactants, phosphate esters, coupling agents, esters of polyhydric alcohols and fatty acids, acrylic polymers, and silicone treatment agents. At least one selected from the group consisting of is used.

Any suitable method may be adopted as the method for producing the hollow particles. A method for producing hollow particles according to one embodiment of the present invention includes: coating a core particle with a shell-forming material to obtain a core-shell particle; removing the core particle from the core-shell particle to obtain a hollow particle precursor; coating the hollow particle precursor with a shell-forming material. By coating the hollow particle precursor with a shell-forming material, a strong shell can be formed, for example, while suppressing a decrease in hollowness ratio. Specifically, the hollow particle precursor obtained by removing the core particle may have pores and may be in a brittle state. By filling the pores of the hollow particle precursor with a shell-forming material, hollow particles having a strong shell can be obtained without shrinking the hollow particle precursor. The contraction of the hollow particle precursor is, for example, softening contraction.

The primary particles of the core particles preferably satisfy 1≦D _SL ≦1.5, more preferably 1≦D _SL ≦1.4, and still more preferably 1≦D _SL ≦1.3. Further, the primary particles of the core particles preferably satisfy 1≦D _ST ≦1.5, more preferably 1≦D _ST ≦1.4, and even more preferably 1≦D _ST ≦1.3. Note that _DSL and _DST are as described above.

The aspect ratio of the core particles is preferably less than 2, more preferably 1.9 or less. On the other hand, the aspect ratio of the core particles is 1 or more, preferably more than 1, and more preferably 1.1 or more. Examples of the shape of the core particles include elliptical, spherical, aggregated, scale-like, plate-like, film-like, cylindrical, prismatic, flattened, go-stone-like, and rice-grain-like. Preferably, the shape of the core particles is spherical or grid-shaped.

The major axis of the core particle is preferably 0.5 μm or more, more preferably 1 μm or more. On the other hand, the major axis of the core particles is preferably 10 μm or less, more preferably 5 μm or less. The short axis of the core particles is preferably 0.25 μm or more, more preferably 0.5 μm or more. On the other hand, the short axis of the core particle is preferably 10 μm or less, more preferably 5 μm or less.

Any suitable material may be employed as the material for forming the core particles. For example, by using a material containing aluminum, the above distribution of Al abundance can be satisfied in the resulting hollow particles. In one embodiment, the core particles are preferably formed of an alunite-type compound represented by the following general formula (I).
M _a [Al _1-x M' _x ] ₃ (SO ₄ ^2- ) _y (OH) _z・mH ₂ O...(I)
In formula (I), M is at least one cation selected from the group consisting of Na ⁺ , K ⁺ , NH ₄ ⁺ and H ₃ O ⁺ . In formula (I), M' is at least one cation selected from the group consisting of Cu ²⁺ , Zn ²⁺ , Ni ²⁺ , Sn ⁴⁺ , Zr ⁴⁺ and Ti ⁴⁺ . In formula (I), a satisfies 0.8≦a≦1.35. In formula (I), m satisfies 0≦m≦5. In formula (I), x satisfies 0≦x≦0.4. In formula (I), y satisfies 1.7≦y≦2.5. In formula (I), z satisfies 4≦z≦7.

As the shell forming material, for example, alkoxysilanes such as sodium silicate (Na ₂ O.nSiO ₂ ) and tetraethoxysilane (Si(OCH ₂ CH ₃ ) ₄ ) are used. In one embodiment, sodium silicate (water glass) is used. Due to the presence of Na, for example, the material may be easily softened during firing, which will be described later, and the firing temperature may be easily controlled. The shell forming material may contain Al. For example, when a core particle is coated with a shell-forming material multiple times, by adjusting the Al concentration in the shell-forming material used for each treatment, the distribution of the Al abundance in the resulting hollow particles can be adjusted. It can also satisfy you.

The amount of coverage with the shell-forming material can be adjusted by any suitable method. For example, the amount of coating can be adjusted by controlling the pH value when coating with a shell-forming material containing sodium silicate. Specifically, sodium silicate can be stable in high pH regions. For example, sodium silicate may be stable at pH 11 or higher. Therefore, by lowering the pH value, sodium silicate molecules can be condensed and silica can be efficiently precipitated onto the core particles. Here, when the core particles contain the above-mentioned alunite type compound, the water slurry of the alunite type compound itself may exhibit acidity. The acidity of the aqueous slurry of the alunite type compound itself is, for example, pH 3 to 5. Since the aqueous slurry of the alunite compound itself is acidic, silica can be efficiently precipitated onto the core particles, for example, without using a pH adjuster to lower the pH value. When core particles containing an alunite-type compound are coated multiple times with a shell-forming material containing sodium silicate, a pH adjuster may be used in one or more of the multiple coats. In this case, as the pH adjuster, for example, an acidic solution such as hydrochloric acid or sulfuric acid can be used. By using an acidic solution, hollow particles with a low Na content can be obtained.

Note that coating with the shell-forming material can also be promoted by heating when coating with the shell-forming material. Specifically, shell precipitation can be promoted to increase the shell formation rate. The heating temperature when coating with the shell forming material is, for example, 80°C to 90°C. Furthermore, the amount of coating can be adjusted by controlling the concentration, blending amount, etc. of the shell-forming material when coating. When the core particles are coated with a shell-forming material containing sodium silicate, the concentration of sodium silicate in the shell-forming material is, for example, 0.1 mol/L to 2 mol/L.

The removal of the core particles is typically performed by dissolving the core particles in an acidic solution. As the acidic solution, for example, hydrochloric acid, sulfuric acid, and nitric acid are used. The melting temperature is, for example, 30°C to 90°C, preferably 50°C to 80°C. According to such a temperature, the core particles can be efficiently dissolved while suppressing problems such as the shell becoming easily broken. In one embodiment, sulfuric acid is used as the acidic solution, for example, from the viewpoint of reusing the substance obtained by reacting with the core particles. Examples of substances obtained by reacting with core particles include salts. The concentration of sulfuric acid is, for example, 0.1 mol/L to 3.5 mol/L, preferably 0.5 mol/L or more. When dissolving the core particles containing the alunite-type compound, the above-mentioned Al content can be satisfactorily achieved by, for example, adjusting the acidic solution, dissolution temperature, and time.

The hollow particle manufacturing method may include firing the core-shell particles before removing the core particles. When the core particles contain the above-mentioned alunite type compound, it is preferable to perform calcination before removing the core particles. It is preferable that the firing is performed, for example, in an air atmosphere. This is because the alunite-type compound can have acid resistance, so the alunite-type compound is changed by firing, and the core particles after firing are in a state where they are easily dissolved in an acidic solution. Specifically, in a core particle containing an alunite-type compound, a portion with a low aggregation density is easily dissolved in an acidic solution, but a portion with a high aggregation density is difficult to dissolve in an acidic solution, and the amount dissolved in an acidic solution is, for example, It remains at about 30% by weight. By firing, aluminum oxide (Al ₂ O ₃ ), which is easily soluble in acidic solutions, is produced from the alunite-type compound, and the solubility of the core particles in acidic solutions can be improved.

The temperature for firing the core-shell particles is, for example, 300°C to 900°C, preferably 300°C to 650°C. According to such a firing temperature, the crystallization of the shell can be suppressed and the aluminum oxide can be produced. The firing time is, for example, 0.5 to 20 hours. Firing may be performed continuously or in multiple stages at different temperatures. In addition, when baking is performed in multiple stages, the above-mentioned baking time is the total baking time of each stage. In one embodiment, the above distribution of Al abundance may be satisfied in the resulting hollow particles by adjusting the firing temperature of the core-shell particles.

The shell-forming material used to coat the hollow particle precursor is preferably selected in accordance with the shell-forming material used to coat the core particle. Specifically, when sodium silicate is employed as the shell-forming material used to coat the core particles, sodium silicate is preferably employed as the shell-forming material used to coat the hollow particle precursor. Ru.

Also when coating the hollow particle precursor with a shell-forming material containing sodium silicate, it is preferable to adjust the coating amount by controlling the pH value. Specifically, sodium silicate can be stable in high pH regions. The high pH region is, for example, pH 11 or higher. Preferably, sodium silicate causes silica to be efficiently precipitated into the hollow particle precursor by condensing sodium silicate molecules by lowering the pH value using, for example, a pH adjuster. As the pH adjuster, for example, an acidic solution such as hydrochloric acid or sulfuric acid is used.

The method for producing hollow particles described above may include firing a hollow particle precursor coated with a shell-forming material. Specifically, the hollow particle precursor may be fired after the hollow particle precursor is coated with the shell forming material. By firing the hollow particle precursor, hollow particles that can greatly contribute to improving dielectric properties can be obtained. Specifically, the hydrophobicity of the surface of the hollow particle precursor can be improved. More specifically, the silanol groups on the surface of the hollow particle precursor can be changed to siloxane. Further, hollow particles that can be easily blended into or dispersed in a resin when producing a resin composition can be obtained. Specifically, by appropriately shrinking the particles by firing, it is possible to fill the pores on the surface of the hollow particle precursor and obtain hollow particles with a smooth surface while preventing the particles from adhering to each other. By obtaining hollow particles with smooth surfaces, for example, the above-mentioned BET specific surface area and pore volume can be satisfactorily achieved. In one embodiment, the above distribution of Al abundance may be satisfied in the resulting hollow particles by adjusting the firing temperature of the hollow particle precursor.

The temperature for firing the hollow particle precursor is, for example, 300°C to 1300°C, preferably 700°C to 1300°C, and more preferably 900°C to 1300°C. According to such a firing temperature, the above-mentioned hydrophobization can be achieved satisfactorily. Moreover, even if firing is performed at such a firing temperature, a high hollowness ratio can be achieved. Specifically, by firing the hollow particle precursor in which the pores are filled with a shell-forming material coating, hydrophobization is successfully achieved while suppressing shrinkage of the hollow particle precursor. can be done. The firing time of the hollow particle precursor is, for example, 0.1 hour to 10 hours. Firing may be performed continuously or in multiple stages at different temperatures. For example, after firing at a temperature T1 of less than 950°C, it may be fired at a temperature T2 of 950°C or higher. In this case, the difference between temperature T1 and temperature T2 (T2-T1) is preferably 150°C or more, more preferably 250°C or more. In addition, when baking is performed in multiple stages, the above-mentioned baking time is the total baking time of each stage.

The method for producing hollow particles may include subjecting the hollow particle precursor to acid treatment before firing the hollow particle precursor. It is preferable that the acid treatment is typically performed using an acidic solution such as hydrochloric acid or sulfuric acid. If sodium silicate is employed as the shell-forming material, the hollow particle precursor may include Na. By removing Na through acid treatment, the firing temperature of the hollow particle precursor can be set high, and hollow particles can be obtained that can greatly contribute to improving dielectric properties.

In the method for producing hollow particles, the step of obtaining the core-shell particles preferably includes a drying process. Specifically, when the core particles are coated with the shell-forming material multiple times, the core particles coated with the shell-forming material are dried and then coated with the shell-forming material again. It is preferable to apply The drying temperature in the step of obtaining core-shell particles is, for example, 90°C to 120°C. The drying time in the step of obtaining core-shell particles is, for example, 3 hours to 24 hours. By including such a drying treatment, the above-mentioned oil absorption amount can be satisfactorily achieved, for example, regardless of whether or not a pH adjuster is used during coating with the shell-forming material.

In one embodiment of the present invention, the hollow particles are used as a functional agent for resin materials. The resin composition containing the hollow particles described above will be explained below.

B. Resin Composition A resin composition in one embodiment of the present invention includes a resin and the hollow particles described above. In the resin composition, the hollow particles can maintain their hollow state well. Moreover, in a resin molded article molded using a resin composition, the hollow state of the hollow particles can be well maintained.

Any appropriate resin may be selected as the resin, depending on the use of the resulting resin composition, for example. For example, the resin may be a thermoplastic resin or a thermosetting resin. Specific examples of the resin include epoxy resin, polyimide resin, polyamide resin, polyamideimide resin, polyetheretherketone resin, polyester resin, polyhydroxypolyether resin, polyolefin resin, fluororesin, liquid crystal polymer, and modified polyimide. These may be used alone or in combination of two or more.

The content of the hollow particles in the resin composition is preferably 0.1% by weight or more, more preferably 0.5% by weight or more. On the other hand, the content ratio is preferably 90% by weight or less, more preferably 85% by weight or less.

In the resin composition, the hollow particles are preferably contained in an amount of 0.5 parts by weight or more, more preferably 1 part by weight or more, based on 100 parts by weight of the resin. On the other hand, the hollow particles are preferably contained in an amount of 300 parts by weight or less, more preferably 200 parts by weight or less, per 100 parts by weight of the resin.

The volume ratio of hollow particles in the resin composition is preferably 0.1% or more, more preferably 0.5% or more. On the other hand, the volume ratio of hollow particles in the resin composition is preferably 70% or less, more preferably 60% or less. For example, this is because the processability when producing a resin composition can be excellent.

The hollowness ratio of the hollow particles in the resin composition is preferably 30% or more, more preferably 40% or more, still more preferably 45% or more, and particularly preferably 50% or more.

The resin composition may contain optional components. Examples of optional components include a curing agent, a stress reducing agent, a coloring agent, an adhesion improver, a mold release agent, a flow regulator, a defoaming agent, a solvent, and a filler. These may be used alone or in combination of two or more. In one embodiment, the resin composition includes a curing agent. The content of the curing agent is, for example, 1 part by weight to 150 parts by weight based on 100 parts by weight of the resin.

Any appropriate method may be employed as a method for producing the resin composition. Specifically, the resin composition is obtained by dispersing the hollow particles in the resin using any suitable dispersion method. Examples of the dispersion method include dispersion using various stirrers such as a homomixer, a disper, and a ball mill, dispersion using an autorotation-revolution mixer, dispersion using shear force using three rolls, and dispersion using ultrasonic treatment.

The above-mentioned resin composition is typically formed into a resin molded article into a desired shape. For example, it is a resin molded body formed into a desired shape using a mold. When molding a resin molded article, the resin composition may be subjected to any appropriate treatment. For example, the resin composition may be subjected to a curing treatment.

In one embodiment of the present invention, the resin composition is used as a resin layer included in a laminate. Hereinafter, a laminate having a resin layer formed from the above resin composition will be explained.

C. Laminate FIG. 4 is a schematic cross-sectional view of a laminate in one embodiment of the present invention. The laminate 10 has a resin layer 11 and a metal foil 12. The resin layer 11 is formed from the above resin composition. Specifically, the resin layer 11 includes the resin and the hollow particles. Although not shown, the laminate 10 may include other layers. Examples of other layers include a base material. The base material may be laminated on one side of the resin layer 11. Specifically, the base material may be placed on the side of the resin layer 11 where the metal foil 12 is not placed. A resin film is typically used as the base material. Unlike the illustrated example, the laminate 10 may have a structure in which a metal foil 12 is disposed on the surface of a laminate structure including a plurality of resin layers 11. The laminate 10 may have a structure in which metal foils 12 are disposed on both sides of a laminate structure including a plurality of resin layers 11. Further, the laminate 10 may have a structure in which a plurality of combinations of resin layers 11 and metal foils 12 are stacked. The laminate 10 is typically used as a printed circuit board. The metal foil 12 is formed into a predetermined shape, for example, so as to constitute a predetermined circuit wiring.

The thickness of the resin layer is, for example, 5 μm or more, preferably 10 μm or more. On the other hand, the thickness of the resin layer is, for example, 100 μm or less, preferably 50 μm or less, and more preferably 25 μm or less. With such a thickness, for example, it is possible to sufficiently cope with the miniaturization of electronic components in recent years.

Any suitable metal may be used as the metal forming the metal foil. Examples include copper, aluminum, nickel, chromium, and gold. These may be used alone or in combination of two or more. The thickness of the metal foil is, for example, 2 μm to 35 μm.

Any suitable method may be adopted as a method for producing the above-mentioned laminate. For example, the resin composition is coated on the base material to form a coating layer, and the metal foil is laminated on the coating layer to obtain a laminate. As another specific example, a laminate is obtained by coating the metal foil with the resin composition to form a coating layer. Typically, the coating layer is cured by applying energy such as heating or light irradiation to the coating layer at any appropriate timing. During coating, the resin composition may be dissolved in any suitable solvent.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples. The method for measuring each characteristic is as follows unless otherwise specified. Further, unless otherwise specified, "%" and "ppm" are based on weight.
1. Long diameter of particles The long diameter of particles was calculated by FE-SEM observation. Specifically, the major diameters of 100 primary particles randomly selected from SEM photographs of the particles were measured, and the arithmetic mean (average major diameter) of the obtained measured values was determined. Note that the magnification for SEM observation was 10,000 times.
2. Short diameter of particles The short diameter of particles was calculated by FE-SEM observation. Specifically, the short axis of 100 primary particles randomly selected from SEM photographs of the particles was measured, and the arithmetic mean (average short axis) of the obtained measurement values was determined. Note that the magnification for SEM observation was 10,000 times.
3. _DSL and _DST
D _SL and D _ST were calculated by FE-SEM observation. Specifically, the major axis of each of 100 primary particles randomly selected from SEM photographs of particles is measured, and the 75th value (D _75L ) is divided by the 25th value (D _25L ). _DSL was calculated. In addition, the short axis of each of 100 primary particles randomly selected from the SEM photographs of the particles was measured, and the 75th value (D _75T ) was divided by the 25th value (D _25T ) to calculate D _ST was calculated.
4. Aspect Ratio The aspect ratio was calculated by FE-SEM observation. Specifically, the aspect ratio was calculated by dividing the average major axis of the particles by the average minor axis of the particles.

[Example 1]
(Preparation of hollow silica particles)
Elliptical alunite particle powder (NaAl ₃ (SO ₄ ) ₂ (OH) ₆ , major axis: 1.98 μm, D _SL : 1.13, minor axis: 1.35 μm, D _ST : 1.18, aspect ratio: 1 .47) 800 g was suspended in 5 L of ion-exchanged water to obtain a slurry of alunite particles.

Next, the obtained slurry of alunite particles was heated to 90° C. while stirring, and 0.55 mol/L of No. 3 water glass (Na ₂ O 2.97 SiO ₂ , manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was added to it. ) was added over 4 hours. After aging the slurry thus obtained for 1 hour, it was dehydrated and washed with water to obtain a cake of the first core-shell particle precursor. Next, the first core-shell particle precursor cake was dried at 105° C. for one day to obtain a core-shell particle powder.

Next, the powder of the first core-shell particle precursor was suspended in 5 L of ion-exchanged water, heated to 90° C. with stirring, and 136 ml of No. 3 water glass containing 0.55 mol/L was added over 10 minutes. Ta. Thereafter, 680 ml of 0.55 mol/L No. 3 water glass and 757 ml of 0.50 mol/L sulfuric acid were simultaneously added. Here, No. 3 water glass was added over 50 minutes, and sulfuric acid was added over 60 minutes. The slurry thus obtained was aged for 30 minutes, then dehydrated and washed with water to obtain a second core-shell particle precursor cake.

The obtained cake of the second core-shell particle precursor was suspended in 5 L of ion-exchanged water, heated to 90°C with stirring, and 136 ml of 0.55 mol/L No. 3 water glass was added thereto over 10 minutes. added. Thereafter, 680 ml of 0.55 mol/L No. 3 water glass and 757 ml of 0.50 mol/L sulfuric acid were simultaneously added. Here, No. 3 water glass was added over 50 minutes, and sulfuric acid was added over 60 minutes. The slurry thus obtained was aged for 30 minutes, dehydrated and washed with water, and then dried at 105° C. for one day to obtain a powder of core-shell particles.

Next, the obtained core-shell particle powder was fired at 500°C for 3 hours and further at 550°C for 1 hour. It is thought that the alunite particles change as described below due to firing.
_NaAl3 ( _SO4 ) ₂ (OH) ₆ → _NaAl ( _SO4 ) ₂ + _Al2O3 + _3H2O

Next, 6 L of ion-exchanged water was added to 737 g of the calcined core-shell particles and resuspended under stirring at room temperature. To this, 3.95 L of 2 mol/L sulfuric acid was added, heated to 90 ° C., and reacted for 5 hours. The core particles were dissolved to obtain a first slurry of hollow silica precursor. The first hollow silica precursor is also a hollow particle precursor. The obtained slurry of the first hollow silica precursor was dehydrated and washed with water to obtain a cake of the first hollow silica precursor.

Next, the obtained first hollow silica precursor cake (88 g of powder) was suspended in 4 L of ion-exchanged water, heated to 90°C with stirring, and added with 0.55 mol/L of No. 3 water. After adding 40 ml of glass over 10 minutes, 200 ml of 0.55 mol/L No. 3 water glass and 210 ml of 0.5 mol/L sulfuric acid were simultaneously added. Here, No. 3 water glass was added over 50 minutes, and sulfuric acid was added over 60 minutes. The slurry thus obtained was aged for 30 minutes, then dehydrated and washed with water to obtain a second hollow silica precursor cake.
Next, the obtained cake of the second hollow silica precursor was suspended in 4 L of ion-exchanged water, heated to 90°C with stirring, and 40 ml of 0.55 mol/L No. 3 water glass was added to this for 10 minutes. After the addition, 200 ml of 0.55 mol/L No. 3 water glass and 210 ml of 0.50 mol/L sulfuric acid were simultaneously added. Here, No. 3 water glass was added over 50 minutes, and sulfuric acid was added over 60 minutes. The slurry thus obtained was aged for 30 minutes, then dehydrated and washed with water to obtain a third hollow silica precursor cake. Furthermore, the third hollow silica precursor cake obtained was suspended in 4 L of ion-exchanged water, heated to 90°C while stirring, and 40 ml of 0.55 mol/L No. 3 water glass was added to this for 10 minutes. After the addition, 200 ml of 0.55 mol/L No. 3 water glass and 210 ml of 0.50 mol/L sulfuric acid were simultaneously added. Here, No. 3 water glass was added over 50 minutes, and sulfuric acid was added over 60 minutes. The slurry thus obtained was aged for 30 minutes, then dehydrated and washed with water to obtain a fourth hollow silica precursor cake.

Next, 2 L of ion-exchanged water and 1083 ml of 2 mol/L sulfuric acid were added to the obtained cake of the fourth hollow silica precursor (282 g of powder), and the mixture was left at 90°C for 1.5 hours to form the fifth hollow silica precursor. of slurry was obtained. Thereafter, the cake obtained by dehydration and water washing was dried at 105° C. for one day to obtain a fifth hollow silica precursor powder.

Next, the obtained fifth hollow silica precursor powder was fired in an electric furnace at 800°C for 1 hour and at 1100°C for 1 hour to obtain hollow silica particles. Specifically, the powder of the fifth hollow silica precursor was fired in an air atmosphere to obtain hollow particles.

(Preparation of resin composition)
95.2 phr of bisphenol F type epoxy resin ("JER806" manufactured by Mitsubishi Chemical Corporation) and 40 phr of the obtained hollow silica particles were heated to atmospheric pressure using a rotational revolution mixer ("ARV-310P" manufactured by Shinky Corporation). A mixture was obtained by mixing for 3 minutes under the conditions of 1000 rpm of rotation and 2000 rpm of revolution. Hereinafter, hollow silica particles may be referred to as filler.
The obtained mixture and 4.8 phr of an imidazole-based epoxy resin curing agent ("2E4MZ" manufactured by Shikoku Kasei Co., Ltd.) were mixed using an autorotation-revolution mixer at a rotation speed of 1000 rpm, a rotation speed of 2000 rpm, and a pressure of 0.7 kPa for 3 minutes. A resin composition was obtained by mixing.

(Preparation of resin molded body)
The obtained resin composition was poured into a Teflon (registered trademark) mold having a thickness of 1.0 mm, and press-molded at 80° C. for 1 hour. After cooling, the molded product was taken out of the mold and placed in a dryer at 150° C. for 4 hours to further heat cure. Thereafter, the molded body was cooled to obtain a sample for evaluation.

[Example 2]
(Preparation of hollow silica particles)
Elliptical alunite particle powder (NaAl ₃ (SO ₄ ) ₂ (OH) ₆ , major axis: 1.98 μm, D _SL : 1.13, minor axis: 1.35 μm, D _ST : 1.18, aspect ratio: 1 .47) 200 g was suspended in 1.4 L of ion-exchanged water to obtain a slurry of alunite particles.

Next, the obtained slurry of alunite particles was heated to 90° C. while stirring, and 0.56 mol/L of No. 3 water glass (Na ₂ O 2.97 SiO ₂ , manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was added to this. ) was added over 4 hours. After aging the slurry thus obtained for 1 hour, it was dehydrated and washed with water to obtain a cake of the first core-shell particle precursor. Next, the first core-shell particle precursor cake was dried at 105° C. for one day to obtain a core-shell particle powder.

Next, the powder of the first core-shell particle precursor was suspended in 1.4 L of ion-exchanged water, heated to 90°C while stirring, and 34 ml of 0.56 mol/L No. 3 water glass was added to this for 10 minutes. added. Thereafter, 168 ml of 0.56 mol/L No. 3 water glass and 188 ml of 0.51 mol/L sulfuric acid were simultaneously added. Here, No. 3 water glass was added over 50 minutes, and sulfuric acid was added over 60 minutes. The slurry thus obtained was aged for 30 minutes, then dehydrated and washed with water to obtain a second core-shell particle precursor cake.

The obtained second core-shell particle precursor cake was suspended in 1.4 L of ion-exchanged water, heated to 90°C with stirring, and 34 ml of 0.56 mol/L No. 3 water glass was added to this for 10 minutes. I added it over time. Thereafter, 168 ml of 0.56 mol/L No. 3 water glass and 188 ml of 0.51 mol/L sulfuric acid were simultaneously added. Here, No. 3 water glass was added over 50 minutes, and sulfuric acid was added over 60 minutes. The slurry thus obtained was aged for 30 minutes, dehydrated and washed with water, and then dried at 105° C. for one day to obtain a powder of core-shell particles.

Next, 1305 ml of ion-exchanged water was added to 177 g of the calcined core-shell particles and resuspended under stirring at room temperature. To this, 555 ml of 3.35 mol/L sulfuric acid was added, heated to 90 ° C., and reacted for 5 hours. The core particles were dissolved to obtain a first slurry of hollow silica precursor. The obtained slurry of the first hollow silica precursor was dehydrated and washed with water to obtain a cake of the first hollow silica precursor.

Next, the obtained first hollow silica precursor cake (18.8 g of powder) was suspended in 1.36 L of ion-exchanged water, heated to 90°C with stirring, and added with 0.56 mol/L. After adding 20 ml of No. 3 water glass over 10 minutes, 100 ml of 0.56 mol/L No. 3 water glass and 105 ml of 0.51 mol/L sulfuric acid were simultaneously added. Here, No. 3 water glass was added over 50 minutes, and sulfuric acid was added over 60 minutes. The slurry thus obtained was aged for 30 minutes, then dehydrated and washed with water to obtain a second hollow silica precursor cake.
Next, the obtained cake of the second hollow silica precursor was suspended in 1.36 L of ion-exchanged water, heated to 90°C with stirring, and 20 ml of 0.56 mol/L No. 3 water glass was added thereto. After the addition took 10 minutes, 100 ml of 0.56 mol/L No. 3 water glass and 105 ml of 0.51 mol/L sulfuric acid were simultaneously added. Here, No. 3 water glass was added over 50 minutes, and sulfuric acid was added over 60 minutes. The slurry thus obtained was aged for 30 minutes, then dehydrated and washed with water to obtain a third hollow silica precursor cake. Furthermore, the third hollow silica precursor cake obtained was suspended in 1.36 L of ion-exchanged water, heated to 90°C with stirring, and 20 ml of 0.56 mol/L No. 3 water glass was added to this. After the addition took 10 minutes, 100 ml of 0.56 mol/L No. 3 water glass and 105 ml of 0.51 mol/L sulfuric acid were simultaneously added. Here, No. 3 water glass was added over 50 minutes, and sulfuric acid was added over 60 minutes. The slurry thus obtained was aged for 30 minutes, then dehydrated and washed with water to obtain a fourth hollow silica precursor cake.

Next, 1.36 L of ion-exchanged water and 146 ml of 3.35 mol/L sulfuric acid were added to the obtained fourth hollow silica precursor cake (52.8 g of powder), and the mixture was left at 90°C for 1.5 hours. A slurry of hollow silica precursor No. 5 was obtained. Thereafter, the cake obtained by dehydration and water washing was dried at 105° C. for one day to obtain a fifth hollow silica precursor powder.

Next, the obtained powder of the fifth hollow silica precursor was fired in an electric furnace (in an air atmosphere) at 800°C for 1 hour and at 1100°C for 1 hour to obtain hollow silica particles.

(Preparation of resin molded body)
A molded article (sample for evaluation) was obtained in the same manner as in Example 1 except that the hollow silica particles were used.

[Example 3]
(Preparation of hollow silica particles)
Elliptical alunite particle powder (NaAl ₃ (SO ₄ ) ₂ (OH) ₆ , major axis: 1.98 μm, D _SL : 1.13, minor axis: 1.35 μm, D _ST : 1.18, aspect ratio: 1 .47) 1500 g was suspended in 7.5 L of ion-exchanged water to obtain a slurry of alunite particles.

Next, the obtained slurry of alunite particles was heated to 90° C. while stirring, and 0.54 mol/L of No. 3 water glass (Na ₂ O 3.14 SiO ₂ , manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was added to it. ) was added over 4 hours. After aging the slurry thus obtained for 1 hour, it was dehydrated and washed with water to obtain a cake of the first core-shell particle precursor.

Next, the obtained cake of the first core-shell particle precursor was suspended in 7.5 L of ion-exchanged water and heated to 90° C. with stirring, and 1507 ml of 0.54 mol/L No. 3 water glass was added thereto. Added over 2 hours. The slurry thus obtained was aged for 1 hour, left for 15 hours with stirring, and then dehydrated and washed with water to obtain a second core-shell particle precursor cake. The obtained second core-shell particle precursor cake was suspended in 7.5 L of ion-exchanged water, heated to 90°C with stirring, and 1507 ml of 0.54 mol/L No. 3 water glass was added to this for 2 hours. I added it over time. The slurry thus obtained was aged for 1 hour, left for 15 hours with stirring, dehydrated and washed with water, and then dried at 100° C. for 1 day to obtain a powder of core-shell particles.

Next, 6 L of ion-exchanged water was added to 864 g of the calcined core-shell particles and resuspended under stirring at room temperature. To this, 7.8 L of 1 mol/L sulfuric acid was added, heated to 90 ° C., and reacted for 5 hours. The core particles were dissolved to obtain a first slurry of hollow silica precursor. The obtained slurry of the first hollow silica precursor was dehydrated and washed with water to obtain a cake of the first hollow silica precursor.

Next, the obtained first hollow silica precursor cake (130 g of powder) was suspended in 860 ml of ion-exchanged water, heated to 90°C with stirring, and added with 0.54 mol/L No. 3 water. After adding 33 ml of glass over 10 minutes, 163 ml of 0.54 mol/L No. 3 water glass and 186 ml of 0.50 mol/L sulfuric acid were added at the same time, and the No. 3 water glass was added over 50 minutes. was added over 60 minutes. The slurry thus obtained was aged for 30 minutes, then dehydrated and washed with water to obtain a hollow silica precursor cake. This same operation was repeated two more times to obtain a second hollow silica precursor cake.

Next, 2 L of ion-exchanged water and 400 ml of 2.87 mol/L sulfuric acid were added to the obtained second hollow silica precursor cake (284 g of powder), and the mixture was left at 90°C for 1.5 hours to form the third hollow silica precursor. Got a body slurry. Thereafter, the cake obtained by dehydration and water washing was dried at 100° C. for one day to obtain a third hollow silica precursor powder.

Next, the obtained powder of the third hollow silica precursor was fired in an electric furnace (in an air atmosphere) at 800°C for 1 hour and at 1100°C for 1 hour to obtain hollow silica particles.

(Preparation of resin molded body)
A molded article (sample for evaluation) was obtained in the same manner as in Example 1, except that the above hollow silica particles were used and the amount of hollow silica particles was 25 phr. Although an attempt was made to blend hollow silica particles in the same amount as in Example 1, it was not possible to blend any more.

[Comparative example 1]
A molded article (sample for evaluation) was obtained in the same manner as in Example 1 except that hollow silica particles were not blended.

<XRD measurement>
When the hollow silica particles of Examples 1, 2, and 3 were analyzed by X-ray diffraction ("EMPYRIAN" manufactured by PANalytical), they were found to be amorphous silica.

<TEM-EDS measurement>
The hollow silica particles of Examples 1, 2, and 3 were analyzed using a transmission electron microscope ("JEM-2100PLUS" manufactured by JEOL Ltd.) and an energy dispersive X-ray analyzer (manufactured by JEOL Ltd.) attached to it. An image was captured using an accelerating voltage of 200 kV and a magnification of 200,000 times, and the composition was analyzed at three points in the thickness direction using a point analysis mode.
The observation results of the hollow silica particles of Example 1 are shown in FIG. 5A, the observation results of the hollow silica particles of Example 2 are shown in FIG. 5B, and the observation results of the hollow silica particles of Example 3 are shown in FIG. 5C. The atomic ratios of oxygen (O), aluminum (Al), and silicon (Si) determined from the obtained peak intensities are also shown. In both cases, it was confirmed that the Al content tended to decrease from the inside to the outside of the shell.

The hollow silica particles of Examples 1, 2, and 3 were also evaluated as follows. The evaluation results are summarized in Table 1.
1. Content of Al The content of Al was determined by preparing an Al content measurement sample from hollow silica particles by pretreatment and analyzing it by high frequency inductively coupled plasma emission spectroscopy (ICP-AES). Specifically, 250 mg of hollow silica particles were weighed into a PMP resin beaker. After that, the hollow silica particles were blended with ultrapure water, 3 ml of nitric acid and 5 ml of hydrofluoric acid were added, dissolved by heating, concentrated to 5 ml, and a 1% aqueous boric acid solution was added to remove the remaining fluoride. Hydrogen acid was masked and heated for 10 minutes to inactivate it so as not to damage the analytical equipment. After cooling, the sample was diluted to 50 ml with ultrapure water to prepare a sample for measuring Al content, which was subjected to analysis.
From the obtained results, the content ratio of Al was calculated.
2. Content of Na The content of Na was determined by preparing a Na content measurement sample from hollow silica particles by pretreatment and analyzing it by atomic absorption spectrometry (AAS). Specifically, 250 mg of hollow silica particles were weighed into a PMP resin beaker. After that, the hollow silica particles were blended with ultrapure water, 3 ml of nitric acid and 5 ml of hydrofluoric acid were added, dissolved by heating, concentrated to 5 ml, and a 1% aqueous boric acid solution was added to remove the remaining fluoride. Hydrogen acid was masked and heated for 10 minutes to inactivate it so as not to damage the analytical equipment. After cooling, the sample was diluted to 50 ml with ultrapure water to prepare a sample for measuring Na content, which was subjected to analysis.
From the obtained results, the content ratio of Na was calculated.
3. Thickness of shell of hollow particles The thickness of shell of particles was calculated by TEM observation. Specifically, the shell thicknesses of 10 primary particles randomly selected from TEM photographs of the particles were measured, and the arithmetic mean (average thickness) of the obtained measured values was determined. Note that the magnification for TEM observation was 10,000 times and 100,000 times.
4. Hollow Ratio The hollow ratio was calculated from the above major axis and short axis and the thickness of the shell. Specifically, the shape of the particle was approximated by the volume in a cylinder using the primary particle diameter (long axis, short axis) and the shell thickness, and the hollow ratio was calculated using the following formula.
Hollowness ratio = Hollow region volume of hollow particles ÷ Volume of hollow particles × 100
Volume of hollow particle = π x Radius ² x Height = π x (Long axis ÷ 2) ² x Short axis Volume of hollow region of hollow particle = π x ((Long axis - Shell thickness x 2) ÷ 2) ² x (Breadth axis - Shell thickness x 2)
5. BET Specific Surface Area The specific surface area was measured using "BELsorp-mini" manufactured by Microtrac Bell Co., Ltd. Specifically, it was measured by a constant volume gas adsorption method using nitrogen gas, and the specific surface area was determined by analysis using the BET multipoint method.
6. Pore Volume Pore volume was measured with "BELsorp-max" manufactured by Microtrac Bell Co., Ltd. Specifically, the pore volume (accumulated pore volume of pores with a diameter of 1 nm to 100 nm and pore volume of pores with a diameter of 1 nm to 10 nm) was measured by a constant volume gas adsorption method using nitrogen gas, and analyzed by the BJH method. The cumulative pore volume of the pores was determined.
7. Density Density was determined by nitrogen gas replacement method. Specifically, a 0.15 to 0.2 g sample was collected in a 1 cm ³ cell using a gas displacement density measuring device (Micromeritics, dry automatic density meter Accupic II 1340), and nitrogen gas Measured using. The measurement was repeated five times or more, and the average value was determined.
8. Dielectric constant and dielectric loss tangent The dielectric constant and dielectric loss tangent were measured by the cavity resonance method using a dielectric constant measuring device for powder. The measurement was performed under the conditions of 10 GHz in an environment of a temperature of 25° C. and a humidity of 44% RH. Note that, as the density necessary for calculating the dielectric properties, the density value determined by the nitrogen gas replacement method described above was used.
9. Oil absorption amount Epoxy resin (JER819 manufactured by Mitsubishi Chemical Corporation) is dropped and mixed with 1 g of hollow silica particles to be measured, and when it changes to a paste, the following conversion formula is calculated from the amount of dropped epoxy resin. The oil absorption amount was calculated. Specifically, the epoxy resin was repeatedly dropped and mixed onto the hollow silica particles, and the end point was defined as the point at which the hollow silica particles turned into a paste. The dropping near the end point was carried out while blending the epoxy resin drop by drop. Thereafter, the amount of epoxy resin per gram of the measurement target is calculated using the following formula, and the obtained oil absorption amount per gram is divided by the specific surface area of the measurement target to calculate the amount per unit area (m ² ) of the surface area. The oil absorption amount was calculated.
Oil absorption per 1g = Epoxy resin titration (g) / Mass of powder to be measured (g)
Oil absorption per unit area (m ² ) of surface area = Oil absorption per 1 g (g/g) / Specific surface area of powder to be measured (m ² /g)

<Evaluation of resin molded body>
Regarding the resin molded bodies (evaluation samples) of Examples and Comparative Examples, density measurements, cross-sectional observations, and dielectric properties were measured. In addition, the porosity of the resin molded body, the filler density in the resin molded body, and the filler porosity in the resin molded body were calculated. The evaluation results are summarized in Table 1. The results of observing the resin molded article of Example 1 at 2000 times magnification are shown in FIG.

(Measurement of density)
The density of the resin molded body was measured using an electronic densitometer (“SD120L” manufactured by Alpha Mirage Co., Ltd.). Specifically, the obtained resin molded body was cut into a size of 5 cm×6 cm using an ultrasonic cutter, and the molded body sample obtained by the cutting was subjected to measurement.

1. Porosity of resin molded body From the above density measurement results, the porosity (volume ratio of air in the resin molded body) Va% of the resin molded body was calculated.
2. Filler Density in Resin Molding The filler density in the resin molding was calculated from the following formula. The filler density in the resin molded article was calculated by subtracting the volume of the resin component from the volume of the filler-containing resin molded article to calculate the filler volume, and dividing the filler addition amount by the calculated filler volume. The volume of the filler-containing resin molded body was measured using an electronic densitometer (“SD120L” manufactured by Alpha Mirage Co., Ltd.). The volume of the resin component was separately calculated from the weight and density of a blank resin molded body prepared without containing a filler.
Filler density in resin molded body=wf/(Vc-mr/ρr)=wf/(Vc-100/ρr)
wf: Part by weight of particles (filler) when the weight of resin is 100 parts by weight (phr) Vc: Volume of resin molding mr: Weight of resin (g)
ρr: Density of resin (g/ml)
3. Filler Hollow Ratio in Resin Molded Body Filler hollow ratio Va/(Va+Vs) in the resin molded body was calculated from the value of the porosity Va% of the resin molded body. Here, Vs can be determined from the following formula.

Vc: Volume of resin molding Vs: Volume of particle shell Va: Volume of air in resin molding Vr: Volume of resin mc: Weight of resin molding (g)
ρc: Density of resin molded body (g/ml)
ms: Weight of particle (shell) (g)
ρs: density of particle shell (2.28 (g/ml))
mr: Weight of resin (g)
ρr: Density of resin (g/ml)
wf: Parts by weight (phr) of particles (filler) when the weight of the resin is 100 parts by weight (phr)

(Observation of cross section of resin molded body)
The obtained molded body sample was cut with a cross-section polisher ("IB-09010CP" manufactured by JEOL Ltd.), and the cross section was subjected to FE-SEM ("JSM-7600F" manufactured by JEOL Ltd., magnification: 2000 times, Observation was made at a magnification of 5,000 times or 10,000 times.

(Measurement of dielectric constant and dielectric loss tangent)
The dielectric constant and dielectric loss tangent of the obtained molded body sample were measured under the following conditions.
・Measurement method: Compliant with IEC 62810 (cavity resonator perturbation method)
・Sample shape: length 55mm or more, width 1.6-2.4mm, height 0.7-1.0mm
・Test conditions: Frequency 10GHz
・Number of measurements: 2 times ・Condition adjustment: 23℃±1℃, 50%RH±5%RH, 24 hours<
・Testing room environment: 23℃±1℃, 50%RH±5%RH
・Measuring device: PNA network analyzer N5222B (manufactured by Keysight Technologies Co., Ltd.)
・Cavity resonator: CP531 for 10GHz (manufactured by Kanto Electronic Application Development Co., Ltd.)

In each Example, as shown in FIG. 6, cross-sectional observation of the resin molded body did not confirm that the resin entered the hollow region, and it was confirmed that the destruction of the hollow particles was suppressed. It can be seen that in Examples 1 and 2 where the oil absorption is low, it is possible to incorporate more filler into the resin, and the dielectric properties of the resin composition (resin molded body) are more excellent.

The hollow particles of the present invention can typically be suitably used for electronic materials. In addition, it can be used in, for example, heat insulating materials, soundproofing materials, impact buffering materials, stress buffering materials, optical materials, and lightweight materials.

L Long axis T Short axis 2 Hollow particle 4 Shell 6 Space (hollow part)
10 Laminated body 11 Resin layer 12 Metal foil

Claims

A hollow particle having a hollow shell inside,
The shell is silica containing aluminum, and the amount of aluminum present in the shell is greater in a first region of the shell located inside in the thickness direction of the shell than in the first region. Hollow particles are characterized by being larger in number than in the second part located on the outside in the thickness direction.
The hollow particles according to claim 1, wherein the aluminum content is less than 1% of the components constituting the shell.
The hollow particle according to claim 1, wherein the amount of aluminum decreases from the inside to the outside of the shell.
Hollow particles according to claim 1, wherein the epoxy resin oil absorption is less than 0.6 g/ m2 .
The hollow particles according to claim 1, wherein the shell further contains sodium, and the sodium content of the shell is 3000 ppm or less.
The hollow particles according to claim 1, wherein the silica is amorphous silica.
The hollow particle according to claim 1, wherein the shell has a hollowness ratio of 30% or more and 95% or less.
The hollow particle according to claim 1, wherein the thickness of the shell is 25 nm or more and 500 nm or less.
obtaining core-shell particles by coating the core particles with a shell-forming material;
removing the core particle from the core-shell particle to obtain a hollow particle precursor; and
coating the hollow particle precursor with a shell-forming material;
The method for producing hollow particles according to any one of claims 1 to 8, comprising:
The manufacturing method according to claim 9, wherein the core particle contains an alunite type compound represented by the following general formula (I):
M a [Al 1-x M' x ] 3 (SO 4 2- ) y (OH) z・mH 2 O...(I)
In formula (I), M is at least one cation selected from the group consisting of Na + , K + , NH 4 + and H 3 O + , and M' is Cu 2+ , Zn 2+ , Ni 2+ , Sn 4+ , Zr 4+ and Ti 4+ , a satisfies 0.8≦a≦1.35, and m satisfies 0≦m≦5. x satisfies 0≦x≦0.4, y satisfies 1.7≦y≦2.5, and z satisfies 4≦z≦7.