JP6839757B2 - How to make inorganic flakes and inorganic flakes - Google Patents

Description

The present invention relates to a method for producing inorganic flakes and an inorganic flakes.

Conventionally, flakes made of inorganic substances such as glass or minerals used as effective pigments are known.

For example, in Patent Document 1, the sparkle exhibited by an effect pigment produced from a synthetic small piece substrate such as glass flakes is reduced by reducing the amount of substrate particles having a particle size of less than 9 microns and substrate particles having a particle size of more than 85 microns. Techniques for improvement are described. Patent Document 1 describes that the required particle size and particle size distribution can be obtained by classifying flakes through a screen. "Glass flakes" is a registered trademark of Nippon Sheet Glass Co., Ltd.

Patent Document 2 describes an effect pigment containing an artificial base material such as a glass microplate or a microplate of synthetic mica, which has a predetermined volume average cumulative subsieving distribution curve. The predetermined volume average cumulative subsieving distribution curve is realized by performing a classification operation on the artificial base material.

Patent Document 3 describes an effect pigment based on a flake-like substrate such as synthetic mica flakes. The flake-like substrate has a circular coefficient of 1.2 to 2. The flake-like substrate is coated with a high refractive index layer having a refractive index of 1.8 or more.

Further, a technique for rounding the edge portion of particles made of an inorganic substance such as glass particles is also known. For example, Patent Document 4 describes a method for producing edgeless glass particles by passing preheated crushed glass particles through a flame zone having a predetermined width and then passing them through cooling air.

Patent Document 5 describes a crushed glass particle rounding device including a heating device that raises the temperature to a predetermined temperature equal to or higher than the glass softening temperature of the crushed glass particles.

Patent Document 6 describes silica in which the corners generated when the rough stone is crushed are rounded by heat treatment.

In Patent Document 7, a device such as a jet mill is used to give an impact to the flake-shaped glass to crush the flake-shaped glass, and at the same time, the edge portion of the flake-shaped glass is abraded. The manufacturing method is described.

Patent Document 8 describes a method for producing flaky glass having sharp edges, which comprises treating the flaky glass with a corrosive liquid.

Japanese Patent Publication No. 2008-534753 Japanese Patent Application Laid-Open No. 2011-515508 Japanese Unexamined Patent Publication No. 2013-129831 JP-A-2000-119028 Japanese Unexamined Patent Publication No. 2006-306642 Japanese Unexamined Patent Publication No. 2005-162593 International Publication No. 2010/0678225 Japanese Unexamined Patent Publication No. 2010-138010

According to the description of Patent Documents 1 and 2, effective pigments having a predetermined particle size distribution are produced by classification. However, Patent Documents 1 to 3 do not describe or suggest that the raw material is heated above the softening temperature before classification. According to the techniques of Patent Documents 4 and 5, the crushed glass particles are heated to the softening temperature or higher, but the crushed glass particles such as cullet are the targets of treatment, and the flake-shaped glass particles are the targets of treatment. Do not mean. According to the technique described in Patent Document 6, the silica generated when crushing the rough stone is the target of the treatment, and the flake-shaped silica is not the target of the treatment. Although the techniques described in Patent Documents 7 and 8 target flake-shaped glass, there is no description or suggestion that the flake-shaped glass is heated to a temperature higher than the softening temperature.

As described above, Patent Documents 1 to 8 do not describe or suggest an appropriate classification operation for a powder obtained by heating a powder containing flake-like particles formed of an inorganic substance to a temperature higher than the softening temperature of the inorganic substance. .. Therefore, the present invention is a novel method capable of producing inorganic flakes having a narrow particle size distribution by appropriately classifying the powder obtained by heating a powder containing flaky particles made of an inorganic substance to a temperature equal to or higher than the softening temperature of the inorganic substance. Provide a method. The present invention also provides inorganic flakes having a large number of flaky particles having rounded ends and a narrow particle size distribution.

The present invention
The first powder containing the first flake-like particles made of an inorganic substance is heated so that the surface temperature of the first flake-like particles is higher than the softening temperature of the inorganic substance, and the second flake-like particles are heated. And a second powder containing spherical particles having a particle size smaller than the particle size of the second flake-shaped particles was prepared.
The second powder is passed through a sieve having an opening larger than the particle size of the spherical particles together with running water to remove the spherical particles.
Provided is a method for producing inorganic flakes.

In addition, the present invention
Inorganic flakes
Contains 50% or more of flaky particles with rounded edges on a number basis.
The particle diameter corresponding to the cumulative distribution of 10%, the median diameter, and the particle diameter corresponding to the cumulative distribution of 90% in the volume-based particle size distribution of the inorganic flakes are d2 (10), d2 (50), and d2 (90), respectively. )
10 μm ≤ d2 (50) ≤ 1000 μm,
The relationship of 1.1 ≦ d2 (90) / d2 (10) ≦ 20 and 0.1 ≦ {d2 (90) −d2 (10)} / d2 (50) ≦ 7 is satisfied.
Provides inorganic flakes.

According to the above method, it is possible to produce inorganic flakes containing a large amount of flaky particles having rounded ends and having a narrow particle size distribution.

FIG. 1 is a graph showing the volume-based particle size distribution of the raw material powders of Examples and Comparative Examples. FIG. 2 is a graph showing the volume-based particle size distribution of the intermediate powders of Examples and Comparative Examples. FIG. 3 is a graph showing the volume-based particle size distribution of the inorganic flakes according to the embodiment. FIG. 4 is a graph showing the volume-based particle size distribution of the final powder according to the comparative example. FIG. 5 is a scanning electron microscope (SEM) photograph of the intermediate powder. FIG. 6 is an SEM photograph of the intermediate powder. FIG. 7 is an SEM photograph of the inorganic flakes according to the example. FIG. 8 is an SEM photograph of the inorganic flakes according to the example. FIG. 9 is an SEM photograph of the powder according to the comparative example. FIG. 10 is an SEM photograph of the raw material powder.

Hereinafter, embodiments of the present invention will be described. The following description relates to an example of the present invention, and the present invention is not limited thereto.

The present inventor produces inorganic flakes containing a large amount of flaky particles having rounded ends and having a narrow particle size distribution from a raw material which is a powder containing flaky particles made of an inorganic substance. We examined the method day and night. As a result, the present inventor heats the raw material powder so that the surface temperature of the flake-like particles is higher than the softening temperature of the inorganic substance, and the relatively small particles contained in the raw material powder are contained. We have newly found that particles with a diameter become spherical particles. From the viewpoint of producing inorganic flakes having a narrow particle size distribution, it is conceivable to put a powder containing the spherical particles on a sieve having a size larger than the particle size of the spherical particles in order to remove such spherical particles. Be done. However, the inventor has newly found that the spheroidal particles cannot be properly removed by simply sieving the powder containing the spheroidal particles. Therefore, the present inventor has further studied the classification operation capable of appropriately removing spherical particles, and devised a method for producing inorganic flakes according to the present invention. In the present specification, the “spherical particle” means a particle in which the ratio (Dx / Di) of the maximum diameter Dx to the minimum diameter Di is 1.5 or less when observed by SEM.

The inorganic flakes according to the present invention are typically produced by a method including the following steps (i) and (ii).
(I) The first powder containing the first flake-like particles made of an inorganic substance is heated so that the temperature of the surface of the first flake-like particles is higher than the softening temperature of the inorganic substance, and the second powder To make. Here, the second powder contains the second flake-shaped particles and spherical particles having a particle diameter smaller than the particle size of the second flake-shaped particles.
(Ii) Along with running water, the second powder is passed through a sieve having an opening larger than the particle size of the spherical particles to remove the spherical particles.

By heating the first powder as described above, the surface of the first flake-shaped particles becomes a temperature higher than the softening temperature of the inorganic substance, and the end portion of the first flake-shaped particles is softened. As a result, the second flake-like particles have rounded ends. Further, the heating of the first powder tends to soften the entire particles having a relatively small particle size contained in the first powder. Particles that are softened as a whole tend to become spherical particles due to surface tension. Therefore, the second powder contains spherical particles in addition to the second flake-like particles. It is considered that it is difficult to remove the spherical particles even if the second powder is simply sieved due to the interaction between the spherical particles or the interaction between the spherical particles and the second flake-shaped particles. However, when the second powder is sieved while the running water passes through the sieve, most of the spherical particles pass through the sieve together with the running water and the spherical particles are removed. As a result, it is possible to produce inorganic flakes containing a large amount of flaky particles having rounded ends and having a narrow particle size distribution.

For example, inorganic flakes contain 50% or more of flaky particles having rounded ends on a number basis. As a result, the inorganic flakes have a good tactile sensation.

The particle diameter corresponding to the cumulative distribution of 10%, the median diameter, and the particle diameter corresponding to the cumulative distribution of 90% in the volume-based particle size distribution of the first powder are d1 (10), d1 (50), and d1 (, respectively. It is expressed as 90). Further, the particle diameter corresponding to the cumulative distribution of 10%, the median diameter, and the particle diameter corresponding to the cumulative distribution of 90% in the volume-based particle size distribution of the inorganic flakes are d2 (10), d2 (50), and d2 (, respectively. It is expressed as 90). The volume-based particle size distribution of the first powder and the inorganic flakes can be measured by, for example, a laser diffraction type particle size distribution measuring device. For example, the following relationships are satisfied in the first powder and the inorganic flakes.
10 μm ≤ d1 (50) ≤ 1000 μm
10 μm ≤ d2 (50) ≤ 1000 μm
d2 (90) / d2 (10) <d1 (90) / d1 (10)
{D2 (90) -d2 (10)} / d2 (50) << {d 1 (90) -d 1 (10)} / d 1 (50)

As described above, the inorganic flakes produced by the method of the present invention have a narrower particle size distribution than the first powder. The volume-based particle size distribution of the inorganic flakes is, for example, 1.1 ≦ d2 (90) / d2 (10) ≦ 20 and 0.1 ≦ {d2 (90) −d2 (10)} / d2 (50) ≦. The relationship of 7 is further satisfied.

The thickness of the inorganic flakes is, for example, 0.2 μm to 1000 μm.

The conditions for heating the first powder in the step (i) above are typically such that the ends are softened while maintaining the overall shape of the first flake-like particles having a relatively large particle size. It has been decided. In addition, the heating condition of the first powder in the step (i) above is included in the first powder so that the second powder contains spherical particles having a predetermined particle size (for example, 100 μm or less). It is defined so that the entire particles having a relatively small particle size can be softened. For example, the conditions for heating the first powder in the step (i) above are set so that the temperature of the surface of the first flake-like particles is 50 ° C. to 250 ° C. higher than the softening temperature of the inorganic substance. ..

The heating of the first powder in the step (i) is performed, for example, by passing the first powder through a flame formed by a burner. For example, the flame is formed in the horizontal direction, and the first powder is dropped so as to pass through the flame. In this case, preferably, the first powder is preheated to a predetermined temperature lower than the softening temperature of the inorganic material before passing the first powder through the flame. For example, the first powder is preheated to a temperature 20 ° C. to 100 ° C. lower than the softening temperature of the inorganic material. For example, the first powder can be preheated by bringing the first powder into contact with the air heated by the flame formed by the burner. In the step (i) above, preferably, after heating the first powder, the heated first powder is rapidly cooled by cooling air. As a result, the shape of the particles contained in the second powder can be easily determined to be an appropriate shape. The quenching of the first powder is performed, for example, by sending cooling air (outside air) by a blower into the space where the first powder that has passed through the flame moves.

In the first powder, the inorganic substance forming the first flake-like particles is not limited to a specific inorganic substance as long as it is an inorganic substance that softens at a predetermined temperature, but is, for example, glass or a mineral. The mineral forming the first flake-like particles is, for example, mica or talc. In this case, in the step (i) above, the particles contained in the first powder having a relatively small particle size tend to become spherical particles.

The second powder contains, for example, 1% to 49% of spherical particles on a number basis. The particle size of the spherical particles contained in the second powder is, for example, 100 μm or less. By removing the spherical particles from the second powder, inorganic flakes having a narrow particle size distribution can be obtained.

The sieve used in the step (ii) above has a mesh size larger than the particle size of the spherical particles. This sieve preferably has an opening smaller than most of the particle size of the second flake-like particles contained in the second powder. The mesh size of the sieve is, for example, 2 μm to 1000 μm.

In the step (ii) above, it is considered that spherical particles pass through the sieve together with running water. Therefore, in order to remove many spherical particles from the second powder, it is desirable that the entire second powder comes into contact with running water evenly. Therefore, in the step (ii) above, it is desirable to move the sieve in a direction perpendicular to the flow direction of running water.

The flow rate of running water in the step (ii) is set so that the spherical particles can be removed and the second flake-shaped particles are not crushed. For example, running water flow rate in the step (ii) above is 1 cm ³ / sec ~1000cm ³ / sec.

From the viewpoint of removing more spherical particles in the step (ii), preferably, the second powder is added to the liquid and stirred for a predetermined period before sieving. The liquid to which the second powder is added is not particularly limited as long as it is a liquid that does not change the quality of the second powder and can disperse the second powder, and is, for example, water. The stirring time is not limited to a specific time, and is, for example, 0.1 minutes to 60 minutes.

By recovering the powder that has not passed through the sieve in the step (ii) above, the inorganic flakes according to the present invention can be obtained. In this case, the moisture adhering to the inorganic flakes is removed by a natural drying treatment or a drying treatment in a drying oven. The inorganic flakes may be coated with a predetermined coating.

The inorganic flakes according to the present invention exhibit a good tactile sensation because most of the second flake-like particles have rounded ends. The inorganic flakes according to the present invention are, for example, at least one of a static friction coefficient of 0.9 or less and a dynamic friction coefficient of 0.7 or less on a friction surface formed by adhering inorganic flakes to the adhesive surface of a fixed adhesive tape. Or give one.

The present invention will be described in more detail by way of examples. The present invention is not limited to the following examples.

<Example>
Raw material powder (manufactured by Nippon Sheet Glass Co., Ltd., product name: glass flake MTD160FY) was prepared. The average thickness of the flaky particles contained in the raw material powder is 0.4 μm, the true density of the raw material powder is 2.7 g / cm ³ , and the bulk density of the raw material powder is 0.03 g / cm ³ . there were. The softening temperature Ts of the glass forming the raw material powder was 870 ° C. to 880 ° C., and the glass transition temperature Tg of the glass forming the raw material powder was about 700 ° C. The volume-based particle size distribution of the raw material powder was measured using a laser diffraction type particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., product name: Microtrac MT3500). The results are shown in FIG. 1 and Table 1. An SEM photograph of the raw material powder is shown in FIG. As shown in FIG. 10, the raw material powder had sharp edges.

The raw material powder preheated to 775 ° C. to 855 ° C. (typical temperature: 820 ° C.) is heat-treated by passing it through a flame formed by a burner, and then rapidly cooled by contacting it with the cooling air blown from the blower. Was done. The surface temperature of the particles of the raw material powder when passing through the flame was 925 ° C. to 1125 ° C. (representative temperature: 1020 ° C.), which was higher than the softening temperature Ts of the glass forming the raw material powder. In this way, an intermediate powder was obtained. The volume-based particle size distribution of the intermediate powder was measured using a laser diffraction type particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., product name: Microtrac MT3500). The results are shown in FIG. 2 and Table 1. In addition, SEM photographs of the intermediate powder are shown in FIGS. 5 and 6. As shown in FIG. 5, the intermediate powder contained flake-like particles and spherical particles. The intermediate powder contained about 20% spherical particles on a number basis. As shown in the histogram of FIG. 2, the particle size distribution of the intermediate powder has a particle size distribution having a single peak with a relatively large particle size and a particle size having a single peak with a relatively small particle size. It had a distribution that seemed to overlap with the distribution. It is considered that the particle size distribution of the intermediate powder reflected a state in which flaky particles having a relatively large particle size and spherical particles having a relatively small particle size were mixed. As shown in FIG. 6, most of the flaky particles of the intermediate powder had rounded ends. Of the flake-shaped particles of the intermediate powder, about 90% or more of the flake-shaped particles on a number basis had rounded ends.

The intermediate powder was stirred in water for 30 minutes at room temperature. Then, the intermediate powder was sieved with a mesh opening of 106 μm while running tap water. During this period, the sieve was moved to reciprocate several times in the horizontal direction. The flow rate of tap water was 10 cm ³ / sec.

The powder remaining on the sieve was dried at 100 ° C. for 30 minutes in a drying oven to obtain inorganic flakes according to Examples. A volume-based particle size distribution of the inorganic flakes according to the examples was measured using a laser diffraction type particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., product name: Microtrack MT3500). The results are shown in FIG. 3 and Table 1. As shown in FIG. 3 and Table 1, it was suggested that the inorganic flakes according to the examples had a narrow particle size distribution. SEM photographs of the inorganic flakes are shown in FIGS. 7 and 8. As shown in FIG. 7, it was suggested that the inorganic flakes contained almost no spherical particles, and most of the spherical particles in the intermediate powder were removed. As shown in FIG. 8, many of the particles of the inorganic flakes had rounded ends.

<Comparison example>
The intermediate powder dried without running tap water was sieved through a sieve having a mesh size of 106 μm. The powder remaining on the sieve was recovered to obtain the powder according to the comparative example. A volume-based particle size distribution of the powder according to the comparative example was measured using a laser diffraction type particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., product name: Microtrack MT3500). The results are shown in FIG. 4 and Table 1. An SEM photograph of the powder according to the comparative example is shown in FIG. As shown in FIG. 9, the powder according to the comparative example contained many spherical particles.

As shown in Table 1, the inorganic flakes according to the examples have smaller D90 / D10 values and smaller (D90-D10) / D50 values as compared with the powders according to the comparative examples, and are narrower particles. It had a diameter distribution. Inorganic flakes having a narrow particle size distribution can be produced by changing particles having a relatively small particle size in the raw material powder into spherical particles by heat treatment and selecting an appropriate classification operation for removing the spherical particles. It was suggested.

<Evaluation of coefficient of friction>
A double-sided tape was attached to the measurement stage of a friction feeling measuring device (manufactured by Trinity Lab, product name: TL201Ts), and 0.1 g of the inorganic flakes according to the example was evenly sprinkled on the adhesive surface of the double-sided tape. Then, the coefficient of static friction and the coefficient of dynamic friction of the adhesive surface of the double-sided tape to which the inorganic flakes of the examples were attached were measured under the following conditions. The results are shown in Table 2.
Meter: Fingerprint type Load applied to the adhesive surface of double-sided tape: 30 g
Measurement distance: 30 mm
Sampling pitch: 1 ms Number of measurements: 3 times

Flakes (D10: 64 μm, D50: 149 μm, D90: 262 μm) according to a comparative example composed of flaky particles having non-rounded (squared) ends that were not heat-treated were prepared. The coefficient of static friction and the coefficient of dynamic friction of the adhesive surface of the double-sided tape to which the flakes of Comparative Example were attached were measured in the same manner except that the flakes of Comparative Example were used instead of the inorganic flakes of Examples. The results are shown in Table 2. As shown in Table 2, the adhesive surface of the double-sided tape to which the inorganic flakes of the examples were attached had a lower static friction coefficient and a lower dynamic friction coefficient than the adhesive surface of the double-sided tape to which the flakes of the comparative example were attached. Therefore, it was suggested that the inorganic flakes according to the examples could impart a good tactile sensation.

Claims (8)

The first powder containing the first flake-like particles made of an inorganic substance is heated so that the surface temperature of the first flake-like particles is higher than the softening temperature of the inorganic substance, and the second flake-like particles are heated. And a second powder containing spherical particles having a particle size smaller than the particle size of the second flake-shaped particles was prepared.
The second powder is passed through a sieve having an opening larger than the particle size of the spherical particles together with running water to remove the spherical particles.
A method of producing inorganic flakes. The particle diameter corresponding to the cumulative distribution of 10%, the median diameter, and the particle diameter corresponding to the cumulative distribution of 90% in the volume-based particle size distribution of the first powder are d1 (10), d1 (50), and d1 respectively. Expressed as (90)
The particle diameter corresponding to the cumulative distribution of 10%, the median diameter, and the particle diameter corresponding to the cumulative distribution of 90% in the volume-based particle size distribution of the inorganic flakes are d2 (10), d2 (50), and d2 (90), respectively. )
10 μm ≤ d1 (50) ≤ 1000 μm,
10 μm ≤ d2 (50) ≤ 1000 μm,
d2 (90) / d2 (10) <d1 (90) / d1 (10), and {d2 (90) -d2 (10)} / d2 (50) << {d1 (90) -d1 (10)} / Satisfy the relationship of d1 (50),
The method according to claim 1. The second aspect of claim 2, further satisfying the relationship of 1.1 ≦ d2 (90) / d2 (10) ≦ 20 and 0.1 ≦ {d2 (90) −d2 (10)} / d2 (50) ≦ 7. Method. The method according to any one of claims 1 to 3, wherein the second flake-like particles have rounded ends. The method according to any one of claims 1 to 4, wherein the second powder is added to the liquid and stirred for a predetermined period before being sieved. The method according to any one of claims 1 to 5, wherein the inorganic substance is glass or a mineral. Inorganic flakes (excluding flaky particles having a maximum particle size of 124.5 μm or less in the particle size distribution) .
Contains 50% or more of flaky particles with rounded edges on a number basis.
The particle diameter corresponding to the cumulative distribution of 10%, the median diameter, and the particle diameter corresponding to the cumulative distribution of 90% in the volume-based particle size distribution of the inorganic flakes are d2 (10), d2 (50), and d2 (90), respectively. )
10 μm ≤ d2 (50) ≤ 1000 μm,
The relationship of 1.1 ≦ d2 (90) / d2 (10) ≦ 20 and 0.1 ≦ {d2 (90) −d2 (10)} / d2 (50) ≦ 7 is satisfied.
Inorganic flakes. Claimed to impart at least one of a static friction coefficient of 0.9 or less and a dynamic friction coefficient of 0.7 or less to a friction surface formed by adhering the inorganic flakes to the adhesive surface of the fixed adhesive tape. 7. The inorganic flakes according to 7.

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