JP2008238005A - Dispersing apparatus for liquid raw material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dispersing apparatus in a new structure capable of uniformly dispersing a liquid raw material (cracking agglomerated particles) with a very simple structure. <P>SOLUTION: The dispersing apparatus for generating shearing stress in the liquid raw material, performing atomization in the liquid raw material and uniformly dispersing it comprises a treatment container 28 with a columnar space 26 and a columnar member 30 fitted to the columnar space 26. The columnar member 3 is rotated at a high speed in the treatment container 28. Also, the treatment container 28 is in a sealed structure with a raw material entrance 28a on one end side and a product exit 28b on the other end side. A shearing flow generation gap is formed between the treatment container 28 and the columnar member 30. A raw material supply means and a product discharge means are connected to the raw material entrance 28a and the product exit 28b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a dispersion device and a dispersion method for a liquid material having a novel structure, and more specifically, a liquid material is obtained by applying a vertical rotational force to a liquid material of a solid-liquid mixing system to cause a vortex or shear flow movement. It is an invention relating to a liquid raw material dispersing apparatus suitable for making a raw material a uniform dispersion (fine dispersion). Here, a solid-liquid mixing system (suspension) will be described as an example of the liquid raw material, but the dispersion apparatus of the present invention is expected to be applicable to a liquid-liquid mixing system (O / W emulsion, W / O emulsion). The

  The dispersion apparatus and dispersion method of the liquid raw material of the present invention are particularly suitable for supplying products in the form of dispersion in liquid such as paints, ceramics, and hybrid materials.

  Due to the solubility / reactivity of recent nanoparticles (less than 1 μm) and the unique properties (electromagnetic / optical / mechanical properties) when they are commercialized, the demand for this dispersion technology in liquids is increasing. These properties are attributed to an increase in specific surface area accompanying the refinement of the particle diameter.

  In view of industrial use, nanoparticles are often stored and transported as dry powder and dispersed in liquid at the stage of manufacturing products (paints, ceramics, hybrid materials). In order to maximize the properties of the nanoparticles, it is desirable that the nanoparticles are dispersed in the dispersion medium as close to the nanoparticles as possible. However, nanoparticles have many surface active sites due to their specific surface area and have a strong cohesive force. In particular, it is difficult to re-disperse nanoparticles once dried. In order to make products that take advantage of the characteristics of nanoparticles, technology is needed to uniformly disperse aggregated nanoparticles that have been dried (hereinafter referred to as “aggregated particles”) as close to primary particles as possible. It is.

  Research to disperse aggregated particles into nanoparticles (primary particles) as much as possible has been performed conventionally, and they can be roughly divided into physical approaches and chemical approaches. Here, the primary particle refers to a single particle or a collection of several molecules. The physical method is a method in which energy exceeding the cohesive force of particles is physically given to the aggregate, and the aggregate is crushed and dispersed. For example, a method using ultrasonic vibration or medium flow can be mentioned. The chemical method is a method for improving the dispersibility of particles by chemical treatment. Examples thereof include chemical surface modification of particles. These two physical and chemical approaches have been independently studied so far, but have not yet reached the point of redispersion of dry powder nanoparticles to a state close to primary particles. The physical dispersion method has a problem that reaggregation starts immediately after the dispersion, and the chemical dispersion method has a problem that it is difficult to chemically treat the deep part of the aggregate.

  And as a dispersion apparatus used for a physical dispersion method, for example, by applying a vertical rotational force to a medium (medium: beads) to cause eddy current movement, that is, by generating a shear flow, There is a medium agitation mill that finely disperses (pulverizes and mixes) solid particles (medium).

  As a stirring mill of the above type, for example, there is a medium stirring mill proposed by one of the applicants of the present application (Patent Document 1).

  However, the medium agitating mill having the above configuration is required to have a relatively large power for transporting the liquid raw material (slurry: solid-liquid mixed system). In addition to the power for transporting the slurry, the beads are moved from the outside to the inside against the moving force toward the outer circumference due to the centrifugal force, and further outside against the lifting force due to the centrifugal force in the outer annular gap. This is because it is necessary to forcibly circulate the beads from above to below.

  Therefore, one of the applicants of the present application has made extensive efforts to develop a new dispersion apparatus and dispersion method that can uniformly disperse liquid raw materials with low power, and as a result, has used media (beads). Even if not, it was found that the aggregated particles could be crushed (dispersed) to some extent, and a liquid raw material dispersing apparatus having the following configuration was proposed (Patent Document 2).

“A dispersion apparatus that makes a liquid raw material a uniform dispersion system by applying a vertical rotational force to the liquid raw material in a state without a pulverizing medium (medium) and moving the liquid raw material in a vortex (shear flow) manner,
An annular processing vessel constituting a vertical annular processing chamber, and an inverted bottomed cylindrical shape (inverted bowl) which is disposed in the annular processing chamber with a bottom clearance at the lower end so as to be vertically rotatable and forms an inner / outer annular clearance. The stirring member is provided with a communication hole in the peripheral wall, and the annular processing vessel is provided with a raw material supply port and a product discharge port. "
However, the dispersing device having the above configuration is complicated in structure, and if the inner and outer annular gaps on the inner and outer peripheral surfaces of the stirring member are made smaller than a predetermined value (for example, 0.1 mm or less) in order to increase the dispersion efficiency, the dispersing device is stable. It was difficult to form a gap.

  Although not affecting the patentability of the present invention, a thin-film swirl high-speed stirring system technique has been introduced as a dispersion technique that can replace the conventional ultra-high pressure homogenizer when preparing a nano-sized emulsion (non-native). Patent Document 1). Some of these are summarized or quoted below.

“The processing liquid held in the container or the processing liquid injected from the bottom swirls by the turbine and rises along the inner wall surface by centrifugal force. When the equilibrium speed is reached, a thin film is formed along the entire inner wall surface of the container. For example, when a turning speed (circumferential speed) is 50 m / s in a container having an inner diameter of 80 mm, a hollow cylindrical turning thin film having a thickness (film thickness) of about 20 mm is formed by high-speed turning. The flow velocity inside follows at a speed that is only slightly slower than the turbine, and the speed drop is slight. It drops to 0 m / s at a few μm at a stroke.A sudden speed difference of 50 m / s is generated while receiving a centrifugal force of 6700 G, so that an intense “heavy stress” is generated on the inner wall surface of the container. , 360 ° Occurs at exactly the same mechanism level. The droplets are thinly drawn and broken instantly, and the aggregates are crushed by rolling on the wall surface by the swirl flow while being pressed against the wall surface by centrifugal force. This is the mechanism of emulsification / dispersion by the thin film swirl high speed stirring method. This intense shear stress made it possible to make fine particles down to submicron, which could not be achieved with a conventional high-speed rotating stirrer. "
JP 2000-126635 A (Claims etc.) JP 2005-319403 A (Claims etc.) Haruo Shibuya “New stirring technology that enables emulsified particle design to nano size”, Chemical Equipment, Chemical Research Committee, April 2006, P.55-56

  In view of the above, an object of the present invention is to provide a dispersing device having a novel structure capable of uniformly dispersing a liquid material (disintegrating aggregated particles) with a very simple structure.

  Another object of the present invention is to provide a dispersion of crushed and agglomerated particles that is stabilized using the above-described dispersion apparatus.

  In order to solve the above-mentioned problems, the present inventors have provided a dispersion device having a meandering shear flow generation gap with a meandering cross section in which a communication hole is eliminated in the beadless dispersion device described in Patent Document 2 previously proposed by the present inventors. (Hereinafter referred to as “inverted cup / column composite type”: see FIG. 1) and a dispersing device (hereinafter referred to as “simple column type”) having a U-shaped shear flow generation gap by fitting a column in a cylindrical container. 2), the gap was set to 1 mm, and high speed rotation (peripheral speed: 40 m / s, 1579 rpm) was performed. As a result, it was found that the dispersibility (micronization ability) is not inferior to the “simple cylindrical type” as compared to the “inverted cup / cylindrical composite type” (see FIG. 6).

  Based on the above findings, the inventors have arrived at a liquid raw material dispersing apparatus having the following constitution that can achieve the first object.

A dispersing device that generates shear stress in a liquid material to crush (aggregate) the agglomerated particles in the liquid material and uniformly disperse the particles,
A processing container having a columnar space; and a columnar member fitted in the columnar space; and a rotation driving means for relatively rotating the processing container and the columnar member,
The processing vessel comprises a raw material inlet on one end side and a product outlet on the other end side,
A shear flow generation gap communicating with the raw material inlet and the product outlet is formed between the processing container and the cylindrical member,
The shear flow generation gap includes a disk-like gap located on the raw material inlet side and a cylindrical gap located on the product outlet side,
A raw material supply means and a product discharge means are connected to the raw material inlet and the product outlet, respectively.

  The liquid raw material dispersing apparatus having the above-described configuration can be used without using media (beads), and without having uneven holes corresponding to communication holes on the outer periphery of the stirring member (turbine). Are very close to each other (for example, 1 mm or less), so that the dispersed particles can be miniaturized.

  Furthermore, the second object of the present invention (preparation of a stable dispersion) can be achieved by the following method.

  When the liquid raw material containing aggregated powder is allowed to pass through the gap for generating shear flow in the dispersion apparatus and pulverized (finely divided) in a substantially sealed space, the liquid raw material is subjected to surface modification. It is characterized by being carried out while adding an agent. That is, re-aggregation of the pulverized and agglomerated particles can be prevented by surface modification in a shear field.

  Next, based on one desirable embodiment of the present invention, it explains in detail.

  Here, the aggregated particles (nanoparticle aggregates) in the solid-liquid dispersion (particle aggregate-containing liquid: slurry) are crushed (micronized: physically dispersed), and at the same time, the aggregated particles after pulverization (pulverized aggregate) The case where a stable dispersion liquid in which the pulverized and agglomerated particles are not re-agglomerated is prepared by surface modification (chemical surface modification) of the particles) will be described as an example.

  FIG. 3 shows a distribution apparatus system diagram applied to the method of the present invention.

  Basically, the dispersion apparatus (container / rotary body assembly) 12 of the present invention and a storage tank 14 are provided, and between the storage tank 14 and the container / rotation body assembly 16 of the dispersion apparatus 12. The supply pipe 18 and the return pipe 20 are connected, and the supply pipe 18 further includes a supply pump (slurry pump, gear pump, etc.) 22, and can circulate the dispersion (slurry) between the dispersion device 12 and the storage tank 14. It is said that. Furthermore, a modifier injector 24 is connected to the bottom of the processing vessel 28 so that a surface modifier can be supplied to the raw material supply side (see FIG. 2). The raw material supply port 28a of the processing container 28 can be connected to the raw material supply pipe 18 via a check means (check valve). In addition, it is good also as a structure provided with the suction pump in the return piping, without using the supply pump or without using it.

  And the dispersion | distribution apparatus 12 is provided with the following structure (refer FIG. 2).

  A processing vessel 28 having a cylindrical space 26 and a columnar member 30 fitted in the cylindrical space 26 are provided, and a rotation driving means 32 for relatively rotating the processing vessel 28 and the cylindrical member 30 is provided. ing. Here, the columnar shape includes a tapered shape. Here, the taper angle (tilt angle) is usually 15 °, more usually within 10 °. Usually, the taper widens from the raw material inlet toward the product outlet, but may be reversed.

  The processing vessel 28 includes a raw material inlet 28a on one end side and a product outlet 28b on the other end side, and a shear flow generation gap 34 communicating with the raw material inlet 28a and the product outlet 28b is provided between the processing vessel 28 and the cylindrical member 30. The formed shear flow gap 34 is a disc-like or conical gap (hereinafter referred to as a “bottom-side gap”) 34a (in the example shown in the figure) 34a located on the raw material inlet 28a side and a product outlet 28b side. And a cylindrical gap (hereinafter referred to as a “circumferential surface side gap”) 34b.

  Here, the gaps (dimensions) between the bottom side and circumferential surface side gaps are set to 2000 μm or less (preferably 1200 μm or less). If the lower limit can form a stable gap, and a liquid material can be supplied and a cylindrical member can be formed, the narrower one can be expected to improve the dispersibility by increasing the shear stress (normally The lower limit is 100 to 200 μm). However, as shown in the test examples to be described later, in the range of 1200 to 400 μm, there is no significant difference in dispersibility (micronization ability). For this reason, it may be around 1000 μm from the viewpoint of stability in manufacturing and operation.

  The gap dimensions are those when the cross-sections of the cylindrical space 26 and the cylindrical member 30 are concentric circles. One or both of the cross-sections of the columnar space 26 and the columnar member 30 may be a regular polygon close to a perfect circle within a range in which both can be relatively rotated. Furthermore, unevenness (dents: dimples) may be formed entirely or partially on one or both of the inner peripheral wall of the cylindrical space 26 and the outer peripheral wall of the cylindrical member 30.

  In the present embodiment, the processing container 28 is vertically placed, and the raw material is supplied to the processing container 28 from the bottom side, and the product is discharged from the ceiling side. The material supply and product discharge can be reversed upside down, and further, the dispersing device can be placed horizontally. In addition, although the raw material inlet 28a is located in the center part of the bottom part side clearance 34a in the example of a figure, you may form it in the eccentric position within about 1/10 of a disc diameter. In that case, it can be expected that the vortex flow (shear flow) is generated more efficiently.

  The rotation driving means 32 is configured such that the columnar member 30 is driven to rotate at high speed by a pulley transmission 38 by a motor (electric motor) 36 via a liquid seal mechanical seal 33. The processing container 28 can be rotated, and both the processing container 28 and the columnar member 30 can be rotated in the reverse direction. The mechanical seal 33 can be replaced with other sealing means such as a ground seal, and the pulley transmission can also be replaced with other transmission means such as a gear, chain transmission, timing belt transmission and the like.

  Furthermore, it is good also considering a dispersion | distribution apparatus as horizontal installation and a cylindrical member as a both-ends axial support structure. By adopting the both-end shaft support structure, it is possible to reliably prevent the columnar member from swinging during high-speed rotation and to make the cylindrical gap narrower.

  Further, the cylindrical member may have a tapered (conical) fitting on the bottom side of the regular polygon of the gap instead of a perfect circle. When the taper is fitted, the bottom side gap amount can be adjusted.

  Although not shown, the processing container is provided with temperature adjusting means (cooling means). This is because the temperature due to shear friction rises, and particles that are dispersoids (particularly primary particles after pulverization) may adhere to the inner wall surface of the processing container. Usually, water cooling by a jacket is used, but air cooling or the like may be used.

  And, though not necessarily, when the dispersed particles of the liquid raw material have a high hardness, the surface of the processing vessel that contacts the processing raw material of the stirring member is a wear-resistant polymer material or a wear-resistant metal (for example, zirconia). Lined with In particular, the bottom side of the processing container is preferably subjected to lining because the wear tends to be accelerated by the centrifugal force and gravity of the cylindrical member (see Patent Document 2).

  Next, the usage mode of the above embodiment will be described.

  Here, a solid-liquid dispersion containing aggregated particles as a liquid raw material will be described as an example, but the method of the present invention can also be applied to a liquid-liquid dispersion. In that case, no surface modifier is used.

  First, the liquid raw material and the surface modifier (liquid or powder) are put into the storage tank 14 and the injector 24, respectively. Then, the pump 22 of the supply pipe 18 and the motor 36 of the dispersing device 12 are driven, and the surface modifier is injected into the processing container. Usually, the injection is continuous, but it may be intermittent.

  Here, the surface modifier varies depending on the dispersion medium and dispersoid (aggregated particles) constituting the liquid raw material. For example, when the dispersion medium is water and the dispersoid is an inorganic compound, a silane coupling agent is used.

Here, the rotation speed (circumferential speed) of the columnar member 30 is usually 10 to 50 m / s, preferably 20 to 45 m / s. For example, when the circumferential speed of the cylindrical member 30 is 40 m / s, the dispersion treatment time is usually 3 to 20 minutes, preferably 4 to 12 minutes, and more preferably 4 to 6 minutes. These numerical values slightly vary depending on the type of the liquid raw material and the size of the processing container 28. Moreover, although the dispersion liquid transport amount of the pump 22 varies depending on the processing capability of the dispersion apparatus, for example, in the case of a processing container capacity (only the processing container) of 20 L (dm ³ ), it is set to 400 to 800 L (dm ³ ) / min.

  At this time, as shown in FIG. 4, the aggregated particles in the liquid raw material are crushed by being subjected to shear stress by the generated shear flow to become crushed aggregated particles, and further, the aggregation preventing modifier is formed on the surface of the crushed aggregated particles. (Surface modifier) adheres. As a result, the pulverized primary particles are not re-agglomerated and a good uniform dispersion state is maintained.

Next, test examples of Examples and Comparative Examples performed for confirming the operation and effect of the present invention will be described.
<Examination of nanoparticle dispersion conditions>
(1) With a view to combining chemical surface modification, we examined a device for physically dispersing aggregated nanoparticles (hereinafter referred to as “aggregated particles”) and attempted to determine the optimum operating conditions. It was.

  A dispersion device for fine particles in liquid is a “stirring type” that uses a propeller blade to stir the particle suspension and utilizes the velocity gradient of the medium flow near the blade and particle collision with the blade. "High-speed rotational shear type" using a high shear field generated in the gap between the fixed ring and "Mill type" using collision between hard spheres, "High-pressure jet type" using pressure difference due to jetting, ultrasonic vibration Broadly divided into “ultrasonic type” to be used. In the stirring type, only aggregates near the blade are dispersed, and uniform dispersion cannot be expected. The mill type has a limit of micron level dispersion. The high-pressure jet type and ultrasonic type are effective for dispersion at the submicron level, but the high-pressure jet type is difficult to apply the surface modification reaction due to the structure of the apparatus. In the ultrasonic type, reaggregation may occur due to long-time ultrasonic irradiation, and it is difficult to ensure the reaction time of the reforming reaction. On the other hand, the high-speed rotary shear type is relatively uniformly dispersed, and the surface modification reaction time can be arbitrarily set by combining with a closed circulation system.

  Therefore, a high-speed rotational shearing type dispersion device was adopted.

  In this study, since the surface of the aggregated particles is not modified, reaggregation starts immediately after dispersion. In particular, when the wettability between the particles and the dispersion medium is poor, aggregation may occur before the evaluation of the particle dispersibility, and the actual dispersion performance may not be evaluated correctly. Therefore, the measurement time required for the evaluation of dispersibility was secured by using a calcium carbonate / water-based slurry in which the wettability of the particles and the dispersion medium was relatively good. The dispersion performance is considered to be affected by the magnitude of the velocity gradient of the shear flow.

  Change the shape of the high-speed rotating body (columnar member or inverted cup), the distance between the rotating body and the container, the rotational speed of the rotating body, and the dispersion processing time, evaluate the dispersion performance by the particle size distribution measurement of the following method, and determine the optimum conditions. Tried. Furthermore, the particles after the dispersion treatment were observed by SEM of the following method, and the presence or absence of particle destruction (crushing) was confirmed.

1) Particle size distribution measurement The measurement was performed using “Microtrac MT3000” (manufactured by Nikkiso Co., Ltd.) to which laser diffraction / scattering method was applied. The time from sampling to measurement was 5 minutes.

  The particle size distribution measurement by the laser diffraction / scattering method is a method of irradiating the particles in the slurry with laser light, detecting the amount of scattered light and the pattern, and measuring the particle size distribution by arithmetic processing. Since the aggregate is processed as a single particle, the particle size distribution of the aggregate is actually measured.

2) SEM observation The SEM sample of the raw material particles was prepared by adhering the raw material powder on the carbon paste applied to the sample stage and applying the osmium coating. The SEM sample after the dispersion treatment was prepared by applying a carbon paste on a sample stage, dropping the slurry, drying, and applying an osmium coating. Each sample was observed with a scanning electron microscope (SCANNING MICROSCOPY) “JSM-7000F” (manufactured by JEOL Ltd.).

  A scanning electron microscope (SEM) is a device that scans the surface of a sample with a focused electron beam, detects and amplifies electrons emitted from each scanning point, and displays an enlarged image in synchronization with the scanning. .

(2) The experiment was conducted as follows
1) Sample preparation Calcium carbonate (“Nanocube 60”: primary particle size: 60 nm, trade name, manufactured by Nittetsu Mining Co., Ltd.) is added to distilled water, stirred gently for 30 minutes, and calcium carbonate with a solid concentration of 4.5 mass%. A slurry was prepared. This was designated as slurry (liquid raw material: dispersion) A. Next, 1 mass% sodium hexametaphosphate (Kanto Chemical Co., Inc.) was added to slurry A as a dispersant with respect to the weight of calcium carbonate, and this was used as slurry (liquid raw material: dispersion) B.

2) Particle dispersion process In the high-speed rotary shear type dispersion device, a shear flow is generated in the gap between the high-speed rotary body and the container covering the rotary body. When agglomerates are placed in a shear flow, the agglomerates are subject to different fluid resistances depending on the site due to the velocity gradient in the shear flow and are considered to break.

  The processing containers of the high-speed rotary shear type dispersion apparatus used for the study are Examples 1, 2, and 3 (FIG. 2) and a comparative example (FIG. 1). In the comparative example, a reverse cup type rotating body 30A is put on a processing container having an annular space 26A. Each processing container used had the dimensions shown in the figure. The gap G in FIG. 2 was set to Example 1: 1 mm (1000 μm), Example 2: 0.5 mm (500 μm), and Example 3: 0.25 mm (250 μm).

  An experiment was conducted by incorporating the dispersion apparatuses of Examples 1, 2, and 3 and the comparative example into the distributed processing apparatus system shown in FIG.

  In addition, water was used as a sealing liquid for the mechanical seal, and nitrogen was pressurized. In order to prevent the dispersion (slurry) from overheating, the storage tank and the processing vessel were cooled with cooling water.

3) Simulation FIG. 4 shows an example of the simulation result of the water flow in the horizontal section of the container by the finite element method for the dispersion apparatus of Example 1 (simple cylinder type: gap 1 mm). ANSYS (Ansys Corporation) was used as simulation software.

  The simulation conditions were 2323 elements, 2714 contacts, water temperature 27 ° C, viscosity 855 µPa · s, rotating body peripheral speed 40 m / s, and various dimensions measured. The arrow in the figure is the velocity vector of the water flow. As a result of the simulation, it was confirmed that a shear flow was generated in the gap between the outer wall surface of the cylindrical member (rotating body) 30 and the inner wall surface of the processing container 28.

  (3) The evaluation experiment was conducted on the following items.

1) Evaluation of the influence of the shape of the rotating body on dispersion performance:
It carried out using each processing container of Example 1 (simple cylindrical type) and a comparative example (inverted cup / cylindrical composite type).

  2000 ml of the slurry A was put into the tank, and the circulation pump (discharge amount 500 ml / min) was operated for 10 minutes, and then operated for 5 minutes at a rotating body peripheral speed of 40 m / s (rotating body outer surface).

2) Evaluation of the influence of the distance between the rotating body and the container on dispersion performance:
It carried out using each processing container of Examples 1, 2, and 3. 2000 ml of slurry B was put into the tank, and the circulation pump (discharge amount 500 ml / min) was operated for 10 minutes, and then it was operated for 15 minutes at a rotating body peripheral speed of 40 m / s.

3) Evaluation of the influence of peripheral speed on dispersion performance:
It carried out using each processing container of Examples 1, 2, and 3. Put 2000 ml of slurry B into the tank and operate the circulation pump (discharge amount 500 ml / min) for 10 minutes, then set the rotating body peripheral speed to 21, 27, 34, 40 m / s and set the dispersion time. 5 minutes.

4) Evaluation of influence of dispersion time on dispersion performance:
It carried out using each processing container of Examples 1, 2, and 3. After putting 2000 ml of slurry B into the tank and operating the circulation pump (discharge amount 500 ml / min) for 10 minutes, the peripheral speed of the rotating body was set to 40 m / s and the dispersion time was set to 5, 10, 15 minutes. .

(4) Measurement Experiment Results and Discussion FIG. 5 shows the particle size distribution measurement results of the raw material particles. The volume average particle diameter was 21.4 μm, indicating that aggregates were formed.

1) Influence of Rotating Body Shape Formation of a particle cake was observed on the inner wall of the inverted cup of the comparative example after finishing the dispersion treatment. On the other hand, no particle cake was formed on the inner wall of the container covering the rotating body. Similarly, no cake formation was observed on the inner wall of the processing container of Example 1. From this, it was found that in the high-speed rotary shear type disperser, the shear flow inside the rotating body, that is, the shear flow generated when the inside stops and the outside rotates is unsuitable for particle dispersion. This is considered to be because a shear flow rotating on the outside works in the same manner as a centrifuge.

  FIG. 6 shows the particle size distribution measurement results of the slurry A subjected to the dispersion treatment using the dispersion devices of the comparative example and the example 1. Both showed almost the same particle size distribution. Since both shapes are exactly the same on the outside of the rotating body, the dispersion performance is considered to be dominated by the particle dispersion action in the region outside the rotating body.

  For comparison, the particle size distribution was also measured for the raw material particles. The result is shown in FIG. Obviously, it can be seen that the particle size distribution of the slurry shown in FIG. 6 after the shear dispersion treatment has shifted to the smaller diameter side.

2) Influence of Rotating Body / Container Distance FIG. 7 shows the particle size distribution measurement result of slurry B subjected to dispersion treatment in the treatment containers of Examples 1 and 2. As the distance between the rotating body and the container becomes smaller, smaller dispersed aggregated particles appear. This is considered to be because when the rotating body peripheral speed is the same, the smaller the distance between the rotating body and the container, the larger the velocity gradient of the shear flow, and the greater force is applied to the aggregated particles. Furthermore, it is expected that the dispersion performance is further improved by reducing the distance between the two.

3) Influence of rotating body peripheral speed The results of dispersion treatment of slurry (liquid raw material) B at a peripheral speed of 0 to 40 m / s using the dispersion processing apparatus of Examples 1, 2, and 3 are shown in FIG. Shown in (B) and (C). The average particle size decreased with the increase of the peripheral speed of the rotating body. This is because coarse particles are dispersed, and the minimum particle diameter hardly changes even when the peripheral speed is increased when the peripheral speed is 25 m / s or more. When the aggregate becomes smaller, the difference in fluid resistance due to the site becomes smaller, so that it is considered that dispersion becomes difficult.

  “D10” indicates the particle diameter at an accumulated volume (from the small diameter side; the same applies hereinafter) of 10%, “D50” indicates an accumulated volume of 50%, and “D90” indicates an accumulated volume of 90%. The same applies to the following drawings.

4) Influence of dispersion treatment time The results of dispersion treatment of slurry B at various dispersion times using the treatment containers of Examples 1, 2, and 3 are shown in FIGS. 9 (A), (B), and (C). In Examples 1 and 2 with a gap of 1 mm and 0.5 mm, when the dispersion time is 5 minutes or more, even if the dispersion time is increased, the coarse particles are slightly reduced and the average particle diameter does not change much. Due to the relationship between the amount of liquid fed by the slurry circulation pump and the amount of slurry, most of the slurry only made one round in the system in the dispersion time of 5 minutes. From this, it is considered that the aggregated particles are crushed and uniformly dispersed only once through the high shear field in the high-speed rotary shear type dispersion device (continuous processing is possible). In Example 3 where the gap is 0.25 mm, the dispersion performance is maintained until the dispersion time is about 15 minutes. The reason is that it can be crushed to smaller aggregates than those of other larger gaps, and it takes time to break up the aggregates.

  As a result of SEM observation of each sample, many aggregated particles of 10 μm or more were observed before the dispersed particles, whereas almost no aggregated particles of 10 μm or more were observed after the dispersion treatment. In addition, after the dispersion treatment, the particles formed a thin and wide aggregate. This is presumed to be a result of agglomerates once dispersed at the submicron level being re-aggregated in the drying process in preparation of SEM samples. Furthermore, observation with an SEM high magnification (50000 times) confirmed that the shape of the primary particles did not change and the particles were not destroyed.

(5) Summary In the rotating body / container assembly (Examples 1, 2, 3 and Comparative Examples) of the high-speed rotating shear type dispersing apparatus, the shear flow generated outside the rotating body contributes to particle dispersion. I understood. It has been found that the dispersion effect is enhanced by reducing the distance between the rotating body and the container, or increasing the peripheral speed of the rotating body and applying a large velocity gradient to the shear flow. In addition, it was found that the particles that passed through the shear field were uniformly dispersed without leakage in the high-speed rotary shear type dispersion device. From SEM observation, it was confirmed that the primary particles were not broken by the shear flow.

Based on the above results, a simple column type was used for the rotating body / container assembly of the dispersion processing apparatus, and the liquid raw material was set by setting the peripheral speed of the rotating body to 40 m / s and the dispersing time to 5 minutes to 15 minutes It was shown that the dispersion effect of the particles in the (slurry) is maximized.

<Surface modification of silica nanoparticles in high shear field>
(1) Examination of new particle dispersion technology (hereinafter referred to as shear field surface modification method) that combines physical dispersion by high-speed shearing dispersion device (hereinafter referred to as “dispersion device”) and chemical dispersion by surface modification. It was.

  Although the calcium carbonate nanoparticles could not be dispersed into the primary particles using a disperser, the aggregates were distorted or deformed in the aggregated structure due to the shearing force, and the positions of the particles within the aggregates were exchanged. It is considered that the aggregate surface particles are changed every moment. Therefore, it is expected that surface modification can be performed uniformly on the primary particle surface by performing surface modification in a high shear field.

A system with poor wettability was selected to show the effect of the dispersion technique. A silica / organic solvent system is a system with poor wettability and many applications. Dispersion of silica nanoparticles in an organic solvent is expected to be applied to scratch-resistant coating films, high-hardness / high-strength hybrid materials, and the like. Dispersion of silica particles in an organic solvent has been attempted by surface modification using a silane coupling agent. Silane coupling agents are organic compounds of silicon and have two or more different functional groups that chemically react with inorganic and organic materials. As shown in FIG. 10, the site chemically bonded to the silica surface in the silane coupling agent becomes a silanol group by a hydrolysis reaction, and is adsorbed and dehydrated and condensed in a hydrogen bond to the inorganic surface to form a chemical bond. For this reason, the wettability between an inorganic material and an organic material is improved. There are a wide variety of silane coupling agents, and various functional functional groups can be introduced on the particle surface by appropriately selecting the silane coupling. Isocyanate groups are used in base materials for paints and adhesives because of their high reactivity and stability after reaction. By introducing isocyanate groups on the silica surface, silica can be firmly bonded to the substrate in these products. Based on the above, in this experiment, 3-isocyanatopropyltriethoxysilane was used as a surface modification reagent. In order to demonstrate the effectiveness of the shear surface modification method, surface modification was performed using an autoclave. Thereafter, a comparison with a sample dispersed using a disperser (hereinafter referred to as an autoclave method) was also performed.

  The autoclave method is a method of reacting in a supercritical state of an organic solvent. In a supercritical solvent, the polarity in the system decreases and the viscosity decreases, so it is considered that the modifier easily reaches the deep part of the aggregate. A schematic diagram of the autoclave is shown in FIG.

  And as described above, particle size distribution measurement and dispersion performance evaluation by SEM are performed, confirmation of surface modification reaction using the following FT-IR, and quantitative evaluation of particle surface modification group density using the following TG / DTA went.

1) FT-IR method
The surface modification reaction was confirmed using FT-IR (“FT-IR6200” manufactured by JASCO Corporation).

  Each molecule has its own vibration, and when the molecule is irradiated with infrared light, the infrared light corresponding to the vibration energy of the vibration unique to the molecule is absorbed, and a unique spectrum corresponding to the molecular structure is obtained. FT-IR uses this principle to analyze the molecular structure.

  The silica / hexane slurry was pressure filtered, washed, dried, and then a pellet-shaped measurement sample was prepared with a microtablet molding machine.

2) TG / DTA method
The weight loss by heating was measured with TG / DTA ("Thermo Plus 2 TG8120" manufactured by Rigaku Corporation). The measurement was performed at a temperature increase of 20 ° C./min and in a measurement temperature range of 30 ° C. to 500 ° C. in an oxygen atmosphere. The differential heat / thermogravimetric simultaneous measurement device is a device for measuring the weight change of a sample and the amount of heat generation / endotherm while changing the temperature.

As shown in FIG. 12, the weight reduction range was determined from the DTA curve, and the weight reduction rate within the range was determined. Using the obtained results and the following formula, the modified group density: d _M on the particle surface was determined.

但し、ΔW_Dは改質粒子の重量減少率、ΔW_OH：未改質粒子の重量減少率、N_A：アボガドロ数(/mol)、 M_w：脱離部の分子量(g/mol) ( = 84)、S_N2（m²/g）：比表面積である。

Where ΔW _D is the weight reduction rate of the modified particles, ΔW _OH is the weight reduction rate of the unmodified particles, N _{A is} Avogadro's number (/ mol), and M _{w is} the molecular weight of the desorption site (g / mol) (= 84), S _N2 (m ² / g): specific surface area.

  (2) The experiment was conducted as follows.

1) Sample preparation “AerosilOX50” (trade name, manufactured by Nippon Aerosil Co., Ltd.) was used as silica nanoparticles. The primary particle size is 40 nm and the specific surface area is 50 m2 / g. As a solvent, n-hexane (Kanto Chemical Co., Inc.) (hereinafter, hexane) was used. 3-Isocyanatopropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) was used as a surface modifier.

  1000 ml of a silica / hexane slurry having a solid concentration of 1 mass% was prepared. Next, a modifier solution was prepared based on the following formula.

但し、c_M：改質剤量(ml)、W：粒子重量(g) (= 6.6)、Ｓ_N2：非表面積（ｍ²／ｇ）、d_OH：粒子表面水酸基密度（/nm²）（= 2.8）、M_w：改質剤分子量 (= 247.4)、N_A：アボガドロ数(/mol)、ρ：改質剤密度（g/cm3）(= 1.00)である。

Where c _M : modifier amount (ml), W: particle weight (g) (= 6.6), S _N2 : non-surface area (m ² / g), d _OH : particle surface hydroxyl group density (/ nm ² ) ( = 2.8), M _w : modifier molecular weight (= 247.4), N _A : Avogadro number (/ mol), ρ: modifier density (g / cm 3) (= 1.00).

Then, with respect to d _OH, 1-fold (eq), 2-fold, 5-fold, prepared 10-fold amount of the modifying agent, it was unified total addition of hexane in 30 ml each. Below, in this text to the sample used an equivalent amount of the modifying agent to d _OH denoted as 1x, 2-fold, 5-fold, respectively 10 times, referred to 2x, 5x, and 10x.

2) Sample dispersion treatment The dispersion device of Example 2 was incorporated into the dispersion treatment system device of Fig. 3 to perform shear dispersion treatment. The sealing liquid of the mechanical seal was changed to hexane in accordance with the dispersion medium. The prepared silica / hexane slurry was put into a slurry tank filled with nitrogen. The slurry circulation pump (liquid feed amount: 1000 ml / min) was activated and left for 10 minutes. The rotating body was operated and shear dispersion was performed for 10 minutes. The peripheral speed of the rotating body was set to 40 m / s. Next, the modifier injection device was operated to inject the modifier solution into the dispersion vessel at 1 ml / min. The reaction was carried out for 150 minutes from the start of injection while the rotating body was operating. The slurry was heated by frictional heat from a high shear field, and the temperature at the outlet of the reaction vessel was 68.7 ° C., the boiling point of hexane.

3) Autoclave method (control sample preparation)
200 ml of a silica / hexane slurry having a solid concentration of 82 mass% was prepared. The modifier added to the slurry, equal amounts to likewise d _OH and shear field method, 2-fold, 5-fold, were prepared 10-fold modifier was added each sample.

Each sample was reacted for 1 hour under the conditions of 235 ° C. and 30 kgf / cm 2 using an autoclave. After completion of the reaction, the solvent was discharged to obtain a dry sample. Furthermore, the obtained sample was thrown into the dispersion apparatus of Example 2 together with 1000 ml of hexane to perform dispersion treatment. The slurry circulation pump (liquid feed amount: 1000 ml / min) was operated and allowed to stand for 10 minutes, and then the rotating body was operated to perform shear dispersion for 10 minutes. The peripheral speed of the rotating body was set to 40 m / s.
(3) Since the evaluation test of the following items was conducted, the results and discussion will be described.

1) Qualitative evaluation of modified particle surface
(i) FT-IR measurement:
FIG. 13 shows the results of FT-IR measurement of particles whose surface was modified using the shear field surface modification method. Untreated silica particles showed a peak derived from OH stretching vibration at 3750 cm ^−1, and were confirmed to have a hydroxyl group. On the other hand, the sample shear field surface modification method disappeared O-H stretching vibration of 3750 cm ^-1, the C-H stretching vibration 2840 ~ 3000 cm ^-1, the 2285 cm ^-1 N = C = O stretching A peak derived from vibration was shown. From this result, it is considered that an isocyanate propyl group was introduced on the particle surface by surface modification. The peak observed at 3400 cm ⁻¹ is considered to be derived from an amine produced by the reaction of an isocyanate group with moisture in the air to produce carbamic acid and further elimination of carbon dioxide from carbamic acid.

FIG. 14 shows the results of FT-IR measurement of particles whose surface was modified using the autoclave method. Similar to the shear field method, the O-H stretching vibration at 3750 cm ^-1 disappears, derived from the C-H stretching vibration at 2840 to 3000 cm ^-1 , and the N = C = O stretching vibration at 2285 cm ^-1 Showed a peak. From this result, it is considered that an isocyanate propyl group was introduced on the particle surface by surface modification.

(ii) Determination of surface modification group density (d _M ):
FIG. 15 shows the surface modification group density (d _M ) with respect to the amount of modifier used in the shear field surface modification method. According the amount of the surface modifier is increased, d _M is increased. Further, from 5x Toward the 10x, an increase of d _M to increasing amounts of modifier is gradual, this is a possible number of surface hydroxyl groups of the unreacted decreased, the reaction by steric hindrance between the modifying groups This is thought to be because the progression was inhibited. Further, d _M with increasing reaction time was found to increase.

  FIG. 16 shows the relationship between the amount of modifying agent used and the surface modifying group density in the autoclave method. As the amount of modifier used increased from 2x to 10x, the surface modifying group density increased slowly with increasing modifier amount. Similar to the shear field method, it is considered that the number of unreacted surface hydroxyl groups decreased and steric hindrance between the modifying groups.

2) Measurement of agglomerated diameter FIG. 17 shows the result of measuring the particle size distribution of unmodified silica particles in hexane. As a representative example of particles subjected to surface modification by the shear field method, FIG. 18 shows the particle size distribution measurement result in hexane of particles having a modifier amount of 5 times and a reaction time of 150 minutes. Due to the surface modification, the particle size distribution shifted to the smaller diameter side and the distribution width became narrower. From this, it was found that the dispersibility of the particles is improved by the surface modification method of the shear field.

FIG. 19 shows the relationship between the surface modification group density (d _M ) and the average particle diameter. In the unmodified particles, the average particle size of the aggregates decreased from about 60 μm to about 25 μm after 10 minutes of shearing, indicating that the aggregates were dispersed.

Furthermore, it was found that by carrying out surface modification by the shear field method, the average particle size was reduced to 10 to 20 μm and the dispersibility was improved. The average particle size decreased gradually with increasing d _M from 0.9 to 2.4 / nm ² . This is considered due to the nature of the hydroxyl group on the silica surface. Hydroxyl groups on the silica surface are divided into hydrogen-bonded hydroxyl groups that have already formed hydrogen bonds in the molecule and free hydroxyl groups that are independent in the molecule. The free hydroxyl group forms hydrogen bonds between the particles and causes aggregation between the particles. Because the chemical reaction is more likely to occur than the hydrogen bond type, and the free hydroxyl density (d _OH free) on the silica surface is about 1.3 / nm ² , the sample with d _M 0.9 / nm ² is about 70% It is considered that the free hydroxyl groups are consumed in the surface modification reaction. In other words, since the influence of free hydroxyl groups that cause aggregation in the sample of d _M 0.9 / nm ² has already decreased, it is considered that the amount of decrease in the particle diameter was small even when d _M increased.

The modified particles obtained by the autoclave method showed a larger aggregate diameter than the unmodified particles at d _M 0.75 / nm ² , and a smaller aggregate particle diameter than the unmodified particles at d _M 2.0 / nm ² or more. Moreover, all the samples showed larger aggregate particle diameters than the samples using the shear field method. From this result, it was shown that the shear field surface modification method is more effective for particle dispersion than the autoclave method. Modified particles an autoclave method, despite having a d _M equivalent to the modified particles by shear field method, the poor dispersibility, drying process during the solvent removal is thought to be responsible. In the drying process, aggregates are formed due to the influence of unreacted hydroxyl groups, and the dispersibility is considered to have decreased. In particular, in the sample of d _M 0.75 / nm 2, it is considered that the dispersibility was lower than that of the unmodified particles because a strong aggregate was formed due to the influence of the unreacted free hydroxyl group.

3) SEM observation When observed with SEM of unmodified particles, many aggregates of 10 to 80 μm are observed, which is consistent with the particle size distribution measurement results. The particles after the surface modification of the shear field formed an aggregate in which the particles were thinly spread. It is inferred that the aggregates once dispersed are the result of aggregation in the drying process in preparation of the SEM sample. Further, the particles after surface modification of the shear field were observed at a high magnification (50000 times), and it was confirmed that the shape of the primary particles was not changed and the particles were not broken.

(4) Summary Only the physical dispersion gave a higher dispersion effect than the surface modification by autoclave. From this, the effectiveness of the shear field surface modification method could be demonstrated. Further development of the shear field surface modification method can be expected in the future by examining each of the dispersion device and the surface modification in detail and how to combine them.

It is the model exploded perspective view (A) and model sectional view (B) of the processing container of the dispersion apparatus in the examination stage of the present invention. It is the model disassembled perspective view (A) and model cross-sectional view (B) of the processing container which show one form of the dispersion apparatus of this invention. It is an example of a distribution apparatus system incorporating the distribution apparatus of the present invention. It is a simulation figure in the shear flow generation gap (periphery side) of a simple cylinder type. It is a graph which shows the particle size distribution measurement result of raw material particles. It is a graph which shows the particle size distribution measurement result of the slurry which performed the dispersion process with each dispersion apparatus of Example 1 and a comparative example. It is a graph which shows the particle size distribution measurement result of the slurry which performed the dispersion process with each dispersion apparatus of Example 1-2. It is a graph which shows the change of the particle diameter at the time of performing a dispersion process by changing rotating body peripheral speed with each dispersion apparatus of Example 1, 2, and 3. FIG. It is a graph which shows the change of the particle diameter at the time of performing a dispersion process by changing a dispersion time rotary body peripheral speed with each dispersion apparatus of Example 1, 2, and 3. FIG. It is a model figure which shows the reaction mechanism of a silane coupling agent and an inorganic surface. It is a schematic perspective view which shows an autoclave method. It is a DTA curve used for TG / DTA. It is IR spectrum figure of the particle | grains which surface-modified by the shear field modification method. It is IR spectrum figure of the particle | grains which surface-modified by the autoclave method. It is a graph which shows the measurement result of the surface modification density with respect to the surface modification agent usage-amount in a shear-field modification method. It is a graph which shows the measurement result of the surface modification density with respect to the surface modification agent usage-amount in an autoclave method. It is a graph which shows the particle size distribution measurement result of the unmodified particle | grains in hexane. It is a graph which shows the shear field surface modified grain distribution measurement result in hexane. It is a graph which shows the relationship of the average particle diameter with respect to surface modification group density | concentration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 12 Dispersing device 14 Storage tank 18 Supply piping 20 Return piping 24 Reformer injector 26 Cylindrical space 28 Processing vessel 28a Raw material inlet 28b Product outlet 30 Cylindrical member 32 Rotation drive means 34 Shear flow generating gap 34a Bottom side gap 34b Circumference Face side clearance

Claims (6)

A dispersing device that generates shear stress in a liquid material to crush (aggregate) the agglomerated particles in the liquid material and uniformly disperse the particles,
A processing container having a columnar shape (including a tapered shape; the same applies hereinafter) space and a columnar member fitted in the columnar space are provided, and the processing container and the columnar member are relatively rotated. A rotation driving means;
The processing vessel comprises a raw material inlet on one end side and a product outlet on the other end side,
A shear flow generation gap communicating with the raw material inlet and the product outlet is formed between the processing container and the cylindrical member,
The shear flow generation gap includes a disk-like or cross-section tapered gap located on the raw material inlet side, and a cylindrical gap located on the product outlet side,
A liquid raw material dispersing apparatus, wherein a raw material supply means and a product discharge means are connected to the raw material inlet and the product outlet, respectively.   2. The liquid raw material dispersing apparatus according to claim 1, wherein the raw material inlet is formed at an eccentric position within a central portion of the disc-shaped gap or within about 1/10 of the disc diameter.   The liquid raw material dispersing apparatus according to claim 1 or 2, wherein a gap between the disc-shaped gap and the cylindrical gap is selected within a range of 2000 µm or less.   4. The liquid material according to claim 3, wherein a raw material supply pipe connected directly or indirectly to a raw material transport power source is connectable to the raw material supply port via a check means. Raw material dispersion equipment.   The apparatus for dispersing a liquid material according to any one of claims 1 to 4, wherein the processing container includes a heat radiating or cooling means on an outer peripheral wall forming the cylindrical space. In carrying out the dispersion (atomization) treatment in a substantially sealed space by passing the liquid raw material containing the agglomerated powder through the shear flow generation gap in the dispersion apparatus according to any one of claims 1 to 5. A method for dispersing a liquid material, comprising adding a surface modifier to the liquid material.

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