JP2005021884A - Production method and production apparatus for inorganic spherical body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method for an inorganic spherical body having substantially uniform particle size with good productivity over a long period, and an apparatus for the same. <P>SOLUTION: In the production method for the inorganic spherical body, an aqueous liquid containing an inorganic compound is extruded through a plurality of fine holes formed in one partition wall, into an organic liquid flowing in a laminar flow state at a rate of 0.001-2 m/s in a passage partitioned by the partition wall, and a W/O emulsion is formed with the organic liquid as a dispersion medium and the aqueous liquid containing the inorganic compound as a dispersion phase, then the aqueous liquid in the emulsion is solidified to form the inorganic spherical body. A metallic sheet with a surface subjected to water-repellent treatment is used as the partition wall with the lot of fine holes formed thereon. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing an inorganic sphere. In particular, the present invention relates to a production method and a production apparatus for continuously obtaining inorganic spheres having a substantially uniform particle size useful for liquid chromatographic fillers, cosmetic fillers, catalyst carriers and the like.

  Conventionally, various methods have been proposed as methods for obtaining inorganic spheres having a uniform particle size. In Patent Document 1, a W / O emulsion is prepared by injecting an inorganic compound aqueous solution into an organic liquid through a polymer film having a hole penetrating in the thickness direction, and droplets of the inorganic compound aqueous solution in the emulsion are prepared. Discloses a method for obtaining inorganic spheres from the above. In this method, the emulsion particle size distribution can be made narrow, but because the particle size depends on the physical properties of the polymer membrane and the flow of the organic liquid is not controlled, the emulsion particle size distribution occurs. In terms of the uniformity of the particle size of the inorganic sphere, it was insufficient. There was also a problem with the durability of the polymer film during long-term use.

  In recent years, Patent Document 2 proposes a method for producing a homogeneous emulsion by extruding a pressurized aqueous solution of an inorganic compound into an organic liquid through micropores having a distorted shape and an apparatus therefor. Recently, there has been a demand for the development of a method and an apparatus therefor capable of producing an inorganic sphere having a uniform particle size efficiently over a long period, in a large amount and stably.

JP-A-5-23565 (Claims, FIG. 1) JP 2002-119841 (Claims, FIG. 1)

  An object of the present invention is to provide a method and an apparatus capable of obtaining an inorganic sphere having a substantially uniform particle diameter with high productivity by a continuous process stable over a long period of time.

  In the present invention, an aqueous liquid containing an inorganic compound is a plurality of organic liquids formed in one partition wall in an organic liquid flowing in a laminar flow state at a flow rate of 0.001 to 2 m / s in a flow path partitioned by the partition walls. After extruding through the micropores to form a W / O emulsion in which the organic liquid is a dispersion medium and the aqueous liquid containing the inorganic compound is the dispersed phase, an aqueous liquid containing the inorganic compound in the W / O emulsion is formed. In the method for producing an inorganic sphere by solidification, the method for producing an inorganic sphere is characterized in that the partition wall in which the plurality of micropores are formed is a metal sheet having a water-repellent surface.

  Further, according to the present invention, an aqueous liquid containing an inorganic compound is formed in one partition wall in an organic liquid that flows in a laminar flow state at a flow rate of 0.001 to 2 m / s in a flow path partitioned by the partition walls. A W / O emulsion is formed by extrusion through a plurality of micropores, and an aqueous liquid containing an inorganic compound in the W / O emulsion is solidified to form inorganic spheres. An apparatus for producing an inorganic sphere, wherein the partition wall having a plurality of micropores is a metal sheet having a water repellent surface.

  In the present invention, it is easy to process, has high durability against acidic or basic aqueous liquids and organic solvents, and uses metal partition walls with excellent mechanical properties. Also, problems such as bending and wear hardly occur, and it is suitable for use as mass production equipment.

  According to the present invention, an inorganic sphere having a substantially uniform particle size can be produced with high productivity by a continuous process that is stable over a long period of time. In particular, inorganic spheres having a number average particle diameter measured from a scanning electron micrograph of 0.1 to 100 μm and a standard deviation of the particle diameter distribution divided by the number average particle diameter of 0.20 or less are long. Can be manufactured over time.

  In the present invention, an aqueous liquid containing an inorganic compound is extruded through micropores into an organic liquid flowing in a laminar flow, whereby the organic liquid becomes a dispersion medium (continuous phase), and the aqueous solution containing the inorganic compound is contained therein. After forming an emulsion in which droplets are in a dispersed phase, that is, a W / O type emulsion, an aqueous liquid containing the inorganic compound in the W / O type emulsion is solidified to produce inorganic spheres.

  First, any aqueous liquid containing an inorganic compound can be applied as long as it can form a precipitate by solidification, and not only an aqueous solution of an inorganic compound but also a colloidal solution such as silica sol or alumina sol. Can be adopted. Specific examples of aqueous solutions of inorganic compounds include alkali metal silicates, aluminates, alkaline earth metal halides, copper sulfates, hydrochlorides and nitrates, iron, cobalt or nickel sulfates, hydrochloric acid Examples include aqueous solutions of salts and nitrates.

In the present invention, it is preferable to use an aqueous liquid containing at least one selected from the group consisting of potassium silicate, sodium silicate, sodium aluminate and silica as the inorganic compound. Specifically, an aqueous solution in which water-soluble silica is dissolved, an aqueous dispersion (colloidal silica) in which solid silica is dispersed, such as silica sol obtained by hydrolyzing an organosilicon compound and commercially available silica sol, potassium silicate, An aqueous solution of sodium silicate is preferably used. Of these, sodium silicate is most preferred because of its availability and economic reasons. The ratio of sodium and silicic acid is preferably 2.0 to 3.8, more preferably 2.0 to 3.5 in terms of SiO ₂ / Na ₂ O (molar ratio). Further, the concentration of alkali silicate or silica in the aqueous liquid is preferably 5 to 30% by mass, more preferably 5 to 25% by mass as the SiO ₂ concentration.

  Next, the organic liquid is preferably a saturated hydrocarbon having 9 to 12 carbon atoms, operability, safety to fire, separability between solidified particles and organic liquid, shape characteristics of inorganic spherical particles, water It is selected by comprehensively considering the solubility of the organic liquid in the water. The saturated hydrocarbon having 9 to 12 carbon atoms may be used alone, or two or more of them may be mixed and used. In addition, the saturated hydrocarbon having 9 to 12 carbon atoms may be a linear hydrocarbon or a hydrocarbon having a side chain as long as its chemical stability is good.

  The flash point of the saturated hydrocarbon having 9 to 12 carbon atoms is preferably 20 to 80 ° C. When a saturated hydrocarbon having a flash point of less than 20 ° C. is used as an organic liquid, since the flash point is too low, measures for fire prevention and work environment are required. In addition, those having a flash point of more than 80 ° C. have low volatility, and therefore the amount of hydrocarbons adhering to the resulting inorganic spheres may increase.

In the present invention, the inorganic sphere and the organic liquid after solidifying the emulsion are usually subjected to solid-liquid separation. The organic liquid adhering or adsorbing to the inorganic spheres after separation is preferably vaporized and separated by a drying operation or the like. In terms of being easily separated by vaporization, the organic liquid preferably has a boiling point of 200 ° C. or lower, and those satisfying these conditions are selected from the group consisting of C ₉ H ₂₀ , C ₁₀ H ₂₂ and C ₁₁ H _24. One or more selected from the above are preferred.

  In the present invention, it is preferable to use a surfactant in forming the W / O emulsion. As the surfactant at this time, an anionic surfactant or a cationic surfactant can be used, but a nonionic surfactant is preferable in terms of easy adjustment of hydrophilicity and lipophilicity. For example, polyethylene glycol fatty acid ester, polyethylene glycol alkyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether and the like are desirable.

  The amount of the surfactant used is a condition such as the type of the surfactant, HLB (Hydrophile-lipophile balance) which is an index indicating the degree of hydrophilicity or hydrophobicity of the surfactant, and the particle size of the target inorganic sphere. Depending on the case, it is preferable to contain 500 to 50000 ppm, preferably 1000 to 20000 ppm in the organic liquid. If it is less than 500 ppm, droplets of the aqueous solution to be emulsified become large and the emulsion may become unstable. Moreover, when it exceeds 50000 ppm, the quantity of surfactant adhering to the inorganic spherical body particle | grains which are products becomes large and is unpreferable.

  In the present invention, by setting the flow rate of the organic liquid to 0.001 to 2 m / s, emulsion droplets having a narrow particle size distribution are formed, and the particle size distribution of the obtained inorganic spherical body can be narrowed. More preferably, the flow rate of the organic liquid is 0.01 to 1 m / s.

The Reynolds number of the organic liquid flowing in the flow path is 2100 or less. Here, the Reynolds number when the cross section of the flow path is circular is calculated by Equation 1, and the inner diameter D of the flow path uses the minimum diameter in the cross section of the flow path. Here, D (inner diameter of the channel: m), u (average flow velocity: m / s), ρ (fluid density: kg / m ³ ), μ (fluid viscosity: Pa · s).
Reynolds number (−) = D · u · ρ / μ Equation 1

Further, the Reynolds number when the cross section of the flow path is not circular is calculated by Equation 2. Here, r is the flow path radius (m) = the cross-sectional area of the flow path (m ² ) / the circumferential length (m) in contact with the fluid of the cross-section of the flow path, and u, ρ, and μ are the same as in Equation 1. is there.
Reynolds number (−) = 4 × r · u · ρ / μ Equation 2

  When the Reynolds number is 2100 or less, the flow of the organic liquid is in a laminar state, and thus the flow of the organic liquid is stable. As a result, the aqueous liquid containing the inorganic compound supplied through the micropores always becomes a W / O type emulsion having a constant particle size, so that an inorganic sphere having a substantially uniform particle size is easily produced. On the other hand, when the Reynolds number exceeds 2100, the flow of the organic liquid becomes turbulent, so that the W / O emulsion has a nonuniform particle size as in the conventional case. As a result, the particle size of the inorganic spheres is also uneven. Become. In order to further stabilize the flow of the organic liquid, the Reynolds number of the flow of the organic liquid is preferably 500 or less. The shape of the organic liquid channel is not particularly limited.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the figure, 1, 5 are acrylic resin plates, 2 is a fluororesin sheet, 3 is a metal partition, and 4 is an acrylic resin plate component. In FIG. 1, an aqueous liquid containing an inorganic compound is introduced from a nozzle 8, and is pressed into an organic liquid flowing in a laminar flow so as to be introduced from a nozzle 6 and discharged from a nozzle 7 through a minute hole 9. In addition, the aqueous liquid material press-fitted from the micropores 9 grows larger than the pore diameter at the outlet of the micropores 9 due to the interfacial tension. Thereafter, the droplets are separated by the flow of the organic liquid and become droplets of the W / O emulsion in the organic liquid.

  In the present invention, as a material constituting the partition, an aqueous liquid containing an inorganic compound and a material having resistance to an organic liquid are used. A metal-based material is preferable because it is excellent in workability and mechanical strength, but as a material constituting the partition walls other than the metal partition walls 3, a material mainly composed of a resin is also preferably used. As the resin, it is preferable to use one or more kinds of polyphenylene sulfide, polyether ether ketone, polyimide, polyamideimide, aromatic polyester, and fluororesin because of excellent workability and dimensional stability.

  In the present invention, the metal partition 3 having a plurality of micropores 9 through which the aqueous liquid material passes is formed by forming a plurality of micropores in the metal sheet and then subjecting the surface to a water repellent treatment. This is to promote separation of the liquid from the metal partition 3 after the aqueous liquid containing the inorganic compound has passed through the micropores 9. When the metal partition 3 is hydrophilic, the metal partition is removed after exiting the micropores. It is clear from observation with a high-speed camera that the aqueous liquid flows along the line 3 and the particle diameter of the emulsion tends to be non-uniform. The water repellent treatment needs to be performed on at least a portion of the surface of the metal sheet that comes into contact with the organic liquid.

  The metal sheet has excellent resistance to aqueous liquids and organic liquids containing inorganic compounds and processability when forming micropores, and is a metal that has wear resistance and flex resistance and can exhibit excellent characteristics in practical use. As long as it is comprised by material, nickel, nickel alloy, stainless steel, etc. are suitable as this metal material. Among these, it is preferable to use a stainless steel sheet because it is relatively inexpensive and easily available and has excellent resistance and workability.

  The thickness of the metal sheet is preferably 10 to 500 μm. If the thickness is less than 10 μm, the sheet is likely to be bent, and the horizontality of the sheet may be impaired. In addition, the liquid droplets that are press-fitted from the micropores may be coalesced to form uniform droplets. This is not preferable because it may hinder formation. On the other hand, if the thickness exceeds 500 μm, the processing step may be too complicated, or the processing may take a long time, which is not preferable because it tends to increase costs and deteriorate processing accuracy. More preferably, the thickness of the sheet is 30 to 200 μm.

  There are no particular limitations on the method of forming the micropores, and various processing methods such as laser processing, etching processing, electroforming processing, and press processing can be applied. However, excimer laser and UV- It is preferable to use a laser processing method such as a YAG laser.

  The water-repellent treatment may be performed by a method that can exhibit the water-repellent effect on the metal surface for a long period of time and does not block the micropores. Specifically, the water-repellent treatment is performed by dissolving a hydrophobic resin or a silane coupling agent in a solvent. It is preferable to coat the surface with a treating agent. A thermoplastic resin is preferably used as the hydrophobic resin. This is because even if the micropores are blocked during coating, the pores can be penetrated by heat treatment. In addition, it is preferable from the viewpoint of durability to use a solvent-soluble fluororesin as the hydrophobic resin. Any method can be used for coating, but it is preferable to dip coat a water repellent treatment agent because it can be thinly and uniformly coated. Further, it is preferable to form a water repellent film having a film thickness of 0.001 to 5 μm by the water repellent process. When the thickness is less than 0.001 μm, durability and mechanical strength are insufficient, and pinholes are easily formed. On the other hand, if it is thicker than 5 μm, the micropores are easily clogged during coating, which is not preferable.

  The micropores preferably have a circular cross-sectional shape, but may have a shape other than a circular shape. One or more shapes selected from the group consisting of a rectangle, an ellipse, and a triangle that are not convex on the inside are preferable because processing is relatively easy and an inorganic sphere having a uniform particle diameter can be stably produced. . However, it is essential that any hole be smaller than the channel width of the organic liquid. Examples of the method for forming the micropores include a processing method using a laser such as an excimer laser and a method such as press working, but are not particularly limited.

  Here, when the cross-section of the micropore is a shape other than a circular shape, the droplet has a curvature distribution when it becomes a droplet at the exit of the hole, and is spontaneously separated relatively early and liquid in the organic liquid. Presumed to be drops. Therefore, compared with the case where circular holes are used, there is an advantage that a product having a relatively small emulsion particle diameter can be easily obtained. At this time, the ratio of the diameter of the circle circumscribing the cross-sectional shape to the diameter of the circle inscribed in the cross-sectional shape is preferably 20 or less. More preferably, it is 10 or less. When it exceeds 20, the tendency of the liquid droplets to be divided in the major axis direction is observed, and as a result, the emulsion particles tend to be non-uniform, which is not preferable. In particular, the diameter of the circle inscribed in the cross-sectional shape is preferably 1 μm or more, and the diameter of the circle inscribed in the cross-sectional shape is preferably 80 μm or less.

Moreover, it is preferable that the quadruple value of the dynamic radius r of the cross section of the micropore be 0.1 to 100 μm. More preferably, it is 1 to 80 μm. Here, like Equation 2, r is the hydrodynamic radius r (m) of the cross section = the cross sectional area of the micropore (m ² ) / the perimeter of the microhole cross section (m). Therefore, when the cross section of the microhole is circular, the hydrodynamic radius r = the inner diameter D / 4 of the circle, and therefore, the quadruple value of the hydrodynamic radius r corresponds to the inner diameter D of the circle. When the value of four times the dynamic radius r of the cross section of the micropore is less than 0.1 μm, the supply amount of the aqueous liquid containing the inorganic compound is small, which is not preferable in terms of productivity. On the other hand, when it is larger than 100 μm, it is not preferable because emulsion particles deviating from the target particle diameter are easily generated.

  In the present invention, a plurality of micropores 9 for supplying an aqueous liquid containing an inorganic compound are provided so as to penetrate in the thickness direction of the metal partition 3 on the organic liquid channel from the viewpoint of productivity. Preferably, 100 or more, particularly 1000 or more, can provide sufficient productivity.

  In addition, the arrangement of the micropores 9 at that time is not particularly limited, but from the viewpoint of productivity and workability, the width direction of the metal partition wall 3 (width direction of the organic liquid channel) and the length direction ( A parallel arrangement in which a plurality of micropores are installed at a constant pitch in each of the flow directions of the organic liquid flow paths, or two micropores adjacent in the width direction among the micropores arranged in parallel, and the length It is preferable to select two micropores adjacent to each other in the direction and form a staggered arrangement in which another micropore is installed at the center of a rectangular diagonal line formed by connecting the centers of these holes. Among these, the staggered arrangement is particularly preferable from the viewpoint of improving productivity because the micropores can be densely arranged and the hole area ratio can be increased.

  At this time, it is preferable that the porosity of the metal partition wall 3 is 1 to 35%. When the hole area ratio is 1% or less, productivity is low and equipment costs are expensive, which is not preferable. On the other hand, when the open area ratio is 35% or more, the emulsion droplets formed by press-fitting the aqueous liquid from the respective micropores are united, and as a result, there is a high possibility that the particle diameter becomes non-uniform. Absent. A more preferable aperture ratio is 2 to 25%.

Here, the hole area ratio in the case where a plurality of micropores having a constant area are arranged in a fixed arrangement is calculated by Equation 3. At this time, it is S (cross-sectional area of the micropore: m ² ), P ₁ (pitch in the width direction: m), and P ₂ (pitch in the length direction: m).
Opening ratio (%) = 100 × S / (P ₁ × P ₂ ) Equation 3

In Equation 3, the aperture ratio when circular micro holes are installed in a parallel arrangement can be calculated by Equation 4. Here, it is D (micropore diameter: m), and P ₁ and P ₂ are the same as in Equation 3.
Opening ratio (%) = 78.5 × D ² / (P ₁ × P ₂ ) (4)

In Formula 3, when circular micro holes are installed in a staggered arrangement, when the angle formed by the two diagonal lines defined above is 90 ° (square staggered arrangement), the open area ratio is 60 ° in Formula 5. In the case of (60 ° staggered arrangement), the hole area ratio can be calculated by Expression 6. Here, D is the same as Equation 4, and P is the pitch (m). Note that P in Expression 6 indicates the shorter one (m) of the pitches in the width direction and the length direction.
Opening ratio (%) = 157 × D ² / P ² Formula 5
Opening ratio (%) = 91 × D ² / P ² Formula 6

  Further, it is preferable that the micro holes 9 are provided on the metal partition wall 3 with an interval of 1/2 or more of the diameter of a circle circumscribing the cross-sectional shape of the micro holes. More preferably, an interval equal to or larger than the diameter of the circumscribed circle is provided in the cross-sectional shape of the micropore. If the micropores are provided with an interval shorter than ½ of the diameter of the circumscribed circle, the emulsion droplets are likely to coalesce, and as a result, the particle diameter may be non-uniform, which is not preferable. However, it is preferable to install them as close as possible within a range where they are not united, because productivity can be improved.

  Furthermore, from the viewpoint of efficiently obtaining an inorganic sphere having a target particle diameter, in the present invention, the ratio of the average particle diameter of the inorganic sphere to the four times the hydrodynamic radius r of the cross section of the micropore is set to 0. It is preferable to be 1 to 5.0. More preferably, it is 0.3-3.0. If this ratio is less than 0.1, productivity is lowered, and the average particle size of the resulting inorganic spheres is likely to be larger than the target value, which is not preferable. On the other hand, if it exceeds 5.0, it is difficult to control the particle diameter, and there is a high possibility of causing by-product of fine particles that greatly deviate from the target particle diameter.

  In addition, the manufacturing apparatus of the inorganic spherical body of this invention may be installed so that the metal partition 3 may become parallel with respect to a horizontal surface like FIG. However, when the density of the organic liquid is smaller than the density of the aqueous liquid, the organic liquid flow path is installed so as to have an angle of 30 ° or more with respect to the horizontal plane, and the organic liquid is allowed to flow upward from below. And it is easy to obtain an inorganic sphere having a uniform particle diameter, which is preferable. In particular, it is preferable to install the metal partition 3 so as to be perpendicular to the horizontal plane. On the other hand, when the density of the organic liquid is larger than the density of the aqueous liquid, it is preferable to use these devices and flow the organic liquid downward from above, because the effect of uniformizing the particle diameter as described above can be easily obtained. .

  When the metal partition 3 is installed so as to have an angle of 30 ° or more with respect to the horizontal plane, a pressure due to the liquid depth is applied to each of the aqueous liquid body side and the organic liquid side on the predetermined horizontal plane in the height direction. Assuming that the liquid depths of the aqueous liquid and the organic liquid are substantially the same in a specific horizontal plane, this results from the density difference between the aqueous liquid and the organic liquid, and corresponds to (aqueous liquid density−organic liquid density) × liquid depth. Pressure is applied. Therefore, if the density of the organic liquid is lower than the density of the aqueous liquid, the organic liquid is flowed from the bottom to the top. As compared with the above, the change in the pressure difference between the aqueous liquid body side and the organic liquid side in all channels can be made relatively narrow. As a result, the supply amount of the aqueous liquid material from each micropore on the metal partition wall 3 can be stabilized and the emulsion droplet diameter can be made uniform, which is effective in making the particle diameter of the resulting inorganic spherical body uniform.

  In the present invention, the droplet diameter of the generated W / O type emulsion is not limited to the micropore installation conditions defined above, but the ratio of the linear velocity in the flow direction of the organic liquid to the linear velocity in the flow direction of the aqueous liquid. Also affected by. Here, in FIG. 1, the linear velocity in the flow direction of the aqueous liquid may be measured at the micropore 9 portion. The linear speed ratio is preferably 1 to 500, and more preferably 10 to 300. When the linear velocity ratio exceeds 500, the organic liquid may be excessively consumed, which is not preferable from an economical viewpoint. On the other hand, if it is less than 1, it is difficult to obtain the effect of separating the droplets by the flow of the organic liquid, and the emulsion particles may become non-uniform, which is not preferable.

  As a method of solidifying the aqueous liquid containing the inorganic compound in the W / O emulsion to form an inorganic sphere, a method of adding a precipitant to precipitate the inorganic compound can be used. The precipitant is at least one selected from the group consisting of alkali metal halides or carbonates, inorganic acids, organic acids, inorganic acid ammonium salts, organic acid ammonium salts and alkaline earth metal halides. An aqueous solution may be mentioned. Specific examples include aqueous solutions of ammonium hydrogen carbonate, ammonium sulfate, potassium chloride, potassium hydrogen carbonate and the like, but are not limited thereto.

  When the inorganic compound in the aqueous liquid containing the inorganic compound is alkali silicate or silica, the dispersed droplets of the spherical aqueous solution are gelled while maintaining this shape by gelling the W / O type emulsion. To obtain a spherical silica hydrogel. For gelation, it is preferable to introduce a gelling agent into the emulsion. As the gelling agent, an acid such as an inorganic acid or an organic acid is used, and sulfuric acid, hydrochloric acid, nitric acid, carbonic acid, etc., which are inorganic acids, are particularly preferable. From the standpoint of ease of operation, the most simple and preferred method is a method using carbon dioxide gas. As the carbon dioxide, pure carbon dioxide having a concentration of 100% may be introduced, or carbon dioxide diluted with air or an inert gas may be introduced. The time required for gelation is usually preferably 4 to 30 minutes, and the temperature during gelation is preferably 5 to 30 ° C.

  After the gelation is completed, it is preferable that the reaction system is allowed to stand to separate the silica gel by two-phase separation into an organic liquid phase and an aqueous phase containing silica hydrogel. When saturated hydrocarbon is used as the organic liquid, the organic liquid phase is separated in the upper layer and the aqueous liquid phase containing silica hydrogel is separated in the lower layer. In that case, it is preferable to separate using a separation device.

  The aqueous slurry of silica hydrogel is optionally adjusted to pH 1 to 5 by adding an acid such as sulfuric acid to complete the gelation, and then steamed at a temperature of 60 to 150 ° C, preferably 80 to 120 ° C. Distilling off and removing a few saturated hydrocarbons remaining in the water slurry, and further aging the silica hydrogel by heating at an appropriate pH of about pH 7-9.

  If necessary, after performing the above-mentioned aging treatment, the water slurry is filtered to obtain a silica hydrogel, and this is dried at a temperature of about 100 to 150 ° C. for about 1 to 30 hours, whereby a porous silica spherical body is obtained. Particles are obtained.

  In addition, when an alkali silicate aqueous solution is used as the aqueous liquid and an acid is used as the gelling agent, an alkali metal salt (for example, sodium carbonate if the gelling agent is carbonic acid) is by-produced. In order to prevent mixing into the porous spherical body, it is preferable to sufficiently wash the silica hydrogel (wet cake) when filtered. In some cases, water may be added again to the wet cake after washing to form a slurry to repeat filtration and washing again. At this time, if necessary, an operation of adjusting the pH of the slurry to about 1 to 5 and aging again may be performed.

[Example 1]
(1) (Preparation of solution)
A sodium silicate aqueous solution having a SiO ₂ concentration of 24.4% by mass and a Na ₂ O concentration of 8.14% by mass (SiO ₂ / Na ₂ O molar ratio = 3.09, density of 1320 kg / m ³ ) was prepared. As the organic liquid, isononane (C ₉ H ₂₀ , density 730 kg / m ³ ) was used, and 5000 ppm of sorbitan monooleate as a surfactant was prepared in advance.

(2) (Emulsification device production)
The emulsifying device is shown in cross section in FIG. First, two through holes with an inner diameter of 3.2 mm are formed in a square acrylic resin plate 1 having a thickness of 2 mm and a side of 50 mm, and an outer diameter of 3.2 mm rubber tube piping (product name: Tygon, manufactured by Norton). Tube R-3603) was connected to form nozzles 6 and 7, respectively, so that liquid could be supplied from nozzle 6 and liquid could be discharged from nozzle 7. A through hole with an inner diameter of 3.0 mm is formed at the center of another square acrylic resin plate 5 with a thickness of 2 mm and a side of 50 mm, and a tetrafluoroethylene tube pipe with an inner diameter of 1 mm is connected via a joint part. The nozzle 8 was used so that the liquid could be supplied from the nozzle 8. Further, an acrylic resin plate part 4 was produced by punching out an inner 30 mm square, leaving 10 mm from the outer edge of another square acrylic resin plate having a thickness of 2 mm and a side of 50 mm. Next, a slit having a width of 3 mm and a length of 35 mm was formed in a square fluororesin sheet 2 having a thickness of 400 μm and a side of 50 mm. Furthermore, in the center part of a square SUS304 sheet having a thickness of 50 μm and a side of 50 mm, 28 through-holes having a circular cross-sectional shape with an inner diameter of 30 μm using a UV-YAG laser and having a 100 μm pitch in the width direction, the length direction A total of 6440 holes were drilled as a parallel arrangement of 230 pieces at a pitch of 100 μm, and a solvent-soluble fluororesin (manufactured by Asahi Glass Co., Ltd., trade name: Cytop) was dissolved in a solvent (manufactured by Asahi Glass Co., Ltd., trade name: CT-Solv100). The solution was coated by a dip coating method so that the coating thickness after drying was 0.1 μm, and a metal partition wall 3 was produced. In a range surrounded by a line connecting the centers of the through holes provided at the outermost portions in the width direction and the length direction, the opening ratio of the metal partition wall 3 calculated from Equation 4 was 7.1%.

  The acrylic resin plate 1, the fluororesin sheet 2, the metal partition 3, the acrylic resin plate component 4, and the acrylic resin plate 5 were sequentially laminated, and the four sides were clamped and fixed with an equal force. At this time, the width direction and the length direction of the through hole drilled in the metal partition wall 3 are aligned with the width direction and the length direction of the slit made in the fluororesin sheet 2 so that the through hole is positioned at the center of the slit. In addition, the holes of the nozzle 6 and the holes of the nozzle 7 of the acrylic resin plate 1 were installed so as to be positioned on the slits of the fluororesin sheet 2. Furthermore, it was confirmed that the liquid was not leaked by supplying water to the manufactured device in advance.

(3) (Emulsification)
The emulsifying device prepared in (2) is used in a horizontal position, and isononane prepared by dissolving the surfactant prepared in (1) is supplied from the nozzle 6 and the sodium silicate aqueous solution prepared in (1) is supplied from the nozzle 8. Thus, a W / O type emulsion in which an aqueous sodium silicate solution was dispersed in isononane in which a surfactant was dissolved was continuously produced. At this time, the supply amount of isononane in which the surfactant was dissolved was 1350 mL / h. The experiment was performed at room temperature and the operation time was 2 hours.

At this time, the Reynolds number of the flow of isononane was about 213 as calculated from the hydrodynamic radius of the flow path: 176.5 μm, the linear velocity: 0.31 m / s, and the viscosity: 7.5 × 10 ⁻⁴ Pa · s. There was a laminar flow state. Moreover, the supply amount of the sodium silicate aqueous solution was 32.2 mL / h, and the linear velocity in the flow direction in the micropores 9 was 2.0 × 10 ⁻³ m / s.

  Further, the ratio of the linear velocity in the flow direction of isononane to the linear velocity in the flow direction at the micropore 9 portion of the sodium silicate aqueous solution supplied from the micropore 9 was 159. When the state of emulsification was continuously confirmed with a high-speed camera (not shown) installed in front of the acrylic resin plate 1, the sodium silicate aqueous solution was formed into droplets at the exit of the micropores 9, and the emulsion particles were It had a substantially uniform particle size of about 60 μm.

(4) (gelation)
After collecting the W / O type emulsion prepared in (3), gelation was performed by blowing carbon dioxide gas of 100% concentration at a supply rate of 300 mL / min for 15 minutes while stirring. To the produced silica hydrogel, 200 mL of water was added and allowed to stand for 10 minutes, and then two phases were separated due to the difference in specific gravity to obtain an aqueous slurry (aqueous phase) of silica hydrogel. Next, a 0.1 N aqueous sulfuric acid solution was added to the resulting silica hydrogel water slurry, adjusted to pH 2 at 25 ° C., and allowed to stand for 30 minutes. Next, filtration, washing with water and drying at 120 ° C. for 20 hours gave a porous silica spherical body. The yield of the obtained silica porous sphere was 19.7 g.

(5) (Shape confirmation)
The obtained porous silica spherical body was confirmed to be almost spherical from a scanning electron micrograph. Further, a plurality of photographs were used so that the total number of particles was 1000 or more, and the particle diameter distribution was measured using the results of measuring the total number that can be confirmed in the photographs. The number average particle diameter was 50 μm, and the standard deviation was 6.4 μm. The value obtained by dividing the standard deviation of the particle size distribution by the number average particle size was 0.128.

[Example 2 (comparative example)]
A W / O type emulsion was continuously prepared in the same manner as in Example 1 except that a metal sheet with micropores that was not coated with a fluororesin was used instead of the metal partition wall 3. In addition, when the state of emulsification was confirmed with a high-speed camera, an emulsion having a droplet diameter exceeding 200 μm was generated, and there was also the presence of fine droplets by-produced by partial division of the emulsion droplets. Observed.

[Example 3]
A W / O type emulsion was continuously prepared in the same manner as in Example 1 except that the operation time of emulsification was 954 hours, and the W / O type emulsion produced during the 2 hours immediately before the end of the operation was collected. As in Example 1, gelation was performed to obtain a porous silica spherical body. The yield of the obtained silica porous sphere was 19.5 g.

  The silica porous sphere was confirmed to be almost spherical from a scanning electron micrograph, and the number average particle size measured in the same manner as in Example 1 was 51 μm, and the standard deviation was 6.8 μm. The value obtained by dividing the standard deviation of the particle size distribution by the number average particle size was 0.133, which was a porous silica spherical body having a substantially uniform particle size.

[Example 4 (comparative example)]
A through hole was drilled in the center of a square polyphenylene sulfide sheet having a thickness of 50 μm and a side of 50 mm in the same manner as in Example 1. A W / O emulsion was continuously prepared in the same manner as in Example 1 except that this sheet was used in place of the metal partition wall 3 and that the emulsifying operation time was 55 hours. The W / O type emulsion produced during 2 hours immediately before the end of the operation was collected and gelled in the same manner as in Example 1 to obtain 19.4 g of a porous silica sphere.

  The porous silica sphere was confirmed to be almost spherical from a scanning electron micrograph. When the particle size distribution of the obtained particles was measured in the same manner as in Example 1, the number average particle size was 46 μm, and the standard deviation was 18.3 μm. At this time, the value obtained by dividing the standard deviation of the particle size distribution by the number average particle size was 0.396, which was wider than those of Examples 1 and 3. The cause of this is not necessarily clear, but it is expected that the surface of the polyphenylene sulfide sheet has become hydrophilic over time.

  According to the present invention, inorganic spheres having a substantially uniform particle size can be produced with high productivity by a stable continuous process.

The figure which shows sectional drawing of the emulsification apparatus used in Example 1

Explanation of symbols

1, 5: Acrylic resin plate 2: Fluorine resin sheet 3: Metal partition wall 4: Acrylic resin plate component 6, 7: Nozzle formed on the acrylic resin plate 1 8: Nozzle formed on the acrylic resin plate 5 9: Micro hole penetrating the metal partition 3

Claims (7)

An aqueous liquid containing an inorganic compound is extruded through a plurality of micropores formed in one partition into an organic liquid flowing in a laminar flow state at a flow rate of 0.001 to 2 m / s through a flow path partitioned by the partition. After forming a W / O emulsion in which the organic liquid is a dispersion medium and the aqueous liquid containing the inorganic compound is the dispersed phase, the aqueous liquid containing the inorganic compound in the W / O emulsion is solidified to form an inorganic substance. In a method for producing a spherical body,
The method for producing an inorganic sphere, wherein the partition wall in which the plurality of micropores are formed is a metal sheet having a water repellent surface.   The method for producing an inorganic sphere according to claim 1, wherein the metal sheet has a thickness of 10 to 500 μm.   The method for producing an inorganic sphere according to claim 1 or 2, wherein the constituent material of the metal sheet is any one selected from the group consisting of nickel, a nickel alloy, and stainless steel.   The manufacturing method of the inorganic spherical body in any one of Claims 1-3 which perform the said water-repellent process by spraying or application | coating of a water-repellent agent.   The method for producing an inorganic spheroid according to claim 4, wherein the water repellent treatment agent is obtained by dissolving a hydrophobic resin or a silane coupling agent in a solvent.   The method for producing an inorganic sphere according to any one of claims 1 to 5, wherein a water repellent film having a thickness of 0.001 to 5 µm is formed by the water repellent process. An aqueous liquid containing an inorganic compound passes through a plurality of micropores formed in one partition into an organic liquid flowing in a laminar flow state at a flow rate of 0.001 to 2 m / s through a flow path partitioned by the partition. An apparatus for producing inorganic spheres that is extruded to form a W / O emulsion, and an aqueous liquid containing an inorganic compound in the W / O emulsion is solidified to form an inorganic sphere. An apparatus for producing an inorganic sphere, wherein the partition wall having a plurality of micropores is a metal sheet having a water repellent surface.

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