JPH0661444B2 - Granulator for producing microspheres - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the invention [Industrial field of application] The present invention relates to a submerged granulator for producing dense, heavy and highly spherical microspheres from fine powder of fine ceramics. It is a thing.

[Conventional technology]

In recent years, hard microballs have found many applications in various industries and have attracted attention. It is said that high-strength and high-wear-resistant microspheres with a diameter of 500 μm or less made from fine ceramics such as zirconia are suitable for finely pulverizing, dispersing or mixing hard raw materials and high-purity raw materials. It is predicted to be. However, it is difficult to manufacture microspheres having a diameter of 500 μm or less by the conventional granulation method, and development of a new granulation method is desired.

These hard microballs are manufactured by molding raw material powder into a ball shape and sintering it at a high temperature. Conventional methods for molding into balls include rolling granulation, fluidized bed granulation and axial pressing. The tumbling granulation method is a method in which a binder is added to a raw material powder and kneaded, and then extruded, for example, a granular material formed into a columnar shape is gradually made spherical while rotating in a pan-type or drum-type container. Is. In the axial press method, instead of extrusion molding, the kneaded material is put into a spherical mold with two cracks, but there is a protruding part at the joint between the upper and lower molding dies and it is rolled to remove it and make it spherical. A process is required. 5 with these methods
It is considered unsuitable for commercial production to produce fine balls of less than 00 μm because it requires a high level of skill and yield is poor.

On the other hand, in the fluidized bed granulation method, a stirring blade is provided in the granulator, and the supplied ceramic raw material powder forms a fluidized bed in the machine by the rotating stirring blade, and the added binder causes a minute spherical particle to form over time. Grow into balls. It is difficult to make a fine ball by this method.

In addition, as another method, a method using an Ebara PBS type device as an example of the submerged granulation method is a method of treating wastewater containing suspended solids, and a coagulant is added to a suspension of solids and water. The method is to add a polymer and stir to granulate, but the produced spheres have a diameter of 1 mm or more and have a low sphericity and lack in denseness, and are not suitable for the production of fine ceramics.

(Problems to be Solved by the Invention) In order to manufacture fine ceramics fired balls having a diameter of 500 μm or less, fine ceramics spherical bodies having a diameter of 600 μm or less must be granulated as elementary spheres. (The raw balls, that is, the balls before firing contract and volume is reduced by firing.) However, the rolling method and the axial pressing method require a high degree of skill, and are a low yield and economically disadvantageous method. Dense balls cannot be made by the granulation method. Further, it is not possible to obtain a spherical body having a diameter of 600 μm or less by the conventional granulation method in a liquid.

An object of the present invention is to provide a granulator capable of producing a fine spherical body having a diameter of 50 to 600 μm and a high sphericity and a fine spherical body by granulating fine ceramic powder in a liquid.

(Means for Solving the Problems) As a result of conducting research, the present inventors have developed a granulator for granulating a dense ceramic spherical body having a spherical shape of 600 μm or less and a high sphericity in a liquid. It was confirmed that the microspheres obtained by firing the granules obtained by this granulator at a high temperature by a usual method can be put to practical use.

That is, the present invention is a submerged granulator for producing a granulated product by placing fine powder, a solvent and a binder in a cylindrical stirring tank equipped with a rotary stirring blade, and rotating the stirring blade to produce a granulated product in a cylindrical container. The submerged granulator is characterized in that concave and convex grooves are formed on the wall surface.

Furthermore, in the above granulator, the concave-convex groove formed on the inner wall surface of the cylindrical stirring tank was cut in a plane parallel to the rotation axis of the rotary stirring blade and perpendicular to the rotation axis. The cross section of the groove at this time is preferably a mold, V-shape or arc-shape. Further, in the above granulator, it is preferable that the submerged granulator has a distance between the tip of the rotary stirring blade and the convex portion of the inner wall surface of the cylindrical stirring tank of 2 to 15 mm.

The present inventor has noticed that the fine ceramics powder has a non-affinity with the organic solvent and has a high affinity with water, and the fine ceramics powder is suspended in the organic solvent to allow the presence of water as a binder. Stirred below to obtain a granulated product. Furthermore, in this system, the granule size, sphericity,
Although the compactness is governed by several factors, the shape of the inner wall surface of the cylindrical stirring tank of the granulator and the distance between the tip of the rotary stirring blade and the inner wall surface (convex portion) of the cylindrical stirring tank are granulated. We found that they were deeply involved in the formation of objects.

The main body of the submerged granulator of the present invention is a cylindrical stirring tank and has a rotating stirring blade, and the inner wall surface of the cylindrical stirring tank is preferably in parallel with the rotary blade axis. A groove is formed over the entire length. (Refer to FIG. 1) The shape of the groove when the stirring tank is cut along a plane perpendicular to the rotation axis is preferably a mold, a V-shape, or an arc-shape. (See FIG. 2) The depth of the groove is not particularly limited, but it is preferably 1 to 3 mm when a spherical body having a diameter of 50 to 1500 μm is manufactured. It is possible to manufacture a spherical body having a relatively large particle size (for example, 800 μm or more) without a groove on the inner wall surface. The distance (pitch) between the center line of the groove and the center line of the adjacent groove is not particularly limited, but is 50 to
1 mm to 250 when producing spherical bodies with a diameter of 1500 μm
mm is preferable.

The groove may be formed on the inner wall surface of the cylindrical stirring tank by shaving the inner wall surface, or a plate having a predetermined shape may be attached to the inner wall surface to form the groove as a result.

The distance (clearance) between the tip of the rotating blade and the inner wall surface (convex portion) of the stirring tank is not particularly limited, but is 50 to 1500 with high density.
When manufacturing a sphere having a size of μm, 2 to 15 mm is preferable.

If the distance between the tip of the rotary blade and the inner wall surface (convex portion) of the stirring tank exceeds 15 mm, the granules become large, and if it is 2 mm or less, the working accuracy becomes high, which is not economical.

There is no limitation on the shape and number of rotor blades. The shape of the rotary blade may be either one of the paddle type and the S type, or any combination of the paddle type and the S type. In the case of combination, there is no particular limitation on the number of each.

Fine ceramics capable of producing microspheres by the submerged granulator of the present invention include zirconia, alumina, mullite, silicon nitride, barium titanate, magnesium oxide,
Such as ferrite.

As the organic solvent, an organic solvent having a low affinity for water can be used, and paraffin hydrocarbons, naphthene hydrocarbons, aromatic hydrocarbons or mixtures thereof are preferable.

The granulator of the present application is used as follows.

A predetermined amount of fine ceramics fine powder, an organic solvent and water as a binder is put in a cylindrical stirring tank, and a rotary stirring blade is rotated at 1000 to 2500 rpm to perform granulation. Although the temperature inside the stirring tank gradually rises, the temperature is not usually adjusted. Since the granulation is completed in 30 to 120 minutes, the granulated product is then fired at 1200 to 1450 ° C. in an oxidizing atmosphere in an ordinary electric furnace to obtain fired balls.

Examples The present invention will be described below with reference to examples, but the invention is not limited thereto.

Powders used: Commercially available zirconia powder (with partial stabilizer), the main properties of which were as follows.

Specific surface area: 7.4 m ² / g (measurement method is BET method
MICROMERITICS 220 type true specific gravity …… 5.699 (Measuring method is liquid phase displacement method, measuring machine is Seishin Enterprise's AUTO TRUE DEUCER MA
T-5000) Average particle diameter (50% weight) …… 0.47 μm (Measuring method is sedimentation method, measuring machine is MICROMERITICS SEDGRAPH 5
000 D) Component analysis …… ZrO ₂ 94.81 (wt%) Y ₂ O ₃ 4.61 CaO 0.03 Na ₂ O 0.02 Roasting loss 0.24 Granulation conditions: Amount of zirconia powder …… 57.6g Organic solvent and its amount …… paraffinic Hydrocarbons, 2900 ml binder and its quantity …… Tap water, 6.5 ml Rotating speed of stirring blade …… 2000 rpm Granulation time …… From the start of rotation of the stirring blade until the entire amount of zirconia powder is granulated and the rotation of stirring blade is stopped Time Granulator: It consists of a stirring tank and a rotary stirring blade. The stirring tank is horizontal and the effective internal volume is 3000 ml. The rotation shaft is driven by an electric motor to rotate the rotation shaft so that the rotation speed can be changed.

-Measurement of granule size: An image analysis method by LUZEX500 manufactured by Nireco Co., Ltd. was used. Using this, the Feret diameter of the microspheres was measured and used as the diameter of the spheres. The sphericity is L / W (L is the maximum diameter,
W is the maximum in the diameter orthogonal to L).

The Feret diameter is the distance between parallel lines when an image of a spherical body projected on a plane is sandwiched by two parallel lines, and the average value of the above distances for a plurality of spherical bodies is regarded as a statistical average value. .

Baking balls: Baking balls obtained by firing the spherical bodies obtained by the above granulator in an ordinary electric furnace in an oxidizing atmosphere at a high temperature (up to 1450 ° C.) were also measured by an image analyzer of LUZEX500 manufactured by Nireco Corporation. . The density was determined by the Archimedes method.

Example 1 Groove shape on the inner wall of the stirring tank 〃 Groove depth 0.5 mm 〃 Groove width 0.5 mm 〃 Groove pitch 1.0 mm 〃 Mountain width 0.5 mm Distance between the tip of the stirring blade and the inner wall surface (projection) 2 mm Number of pieces, etc. [3 sets of paddle type, 4 pieces per set]. One set is in the center of the rotary shaft,
The other two sets are mounted at symmetrical positions with respect to the central one set of the rotary shafts.

Granulation time 40 minutes Particle diameter of the obtained microspheres 305 μm 〃 sphericity 1.04 Particle diameter of firing balls after sintering of the above microspheres 247 μm 〃 sphericity 1.04 〃 Density 6.001 g / cm ³ Example 2 Groove shape on the inner wall of the stirring tank 〃 Groove depth 1 mm 〃 Groove width 1 mm 〃 Groove pitch 2 mm 〃 Mountain width 1 mm Distance between the tip of the stirring blade and the inner wall surface (convex) 15 mm Stirring blade shape and number etc. 1 set per sheet] is 3 sets. One set is in the center of the rotary shaft,
The other two sets are mounted symmetrically with respect to the central one set.

Granulation time 90 minutes Particle diameter of the obtained microspheres 615 μm 〃 sphericity 1.07 Particle diameter of firing balls after sintering of the above microspheres 492 μm 〃 sphericity 1.07 〃 Density 5.811 g / cm ³ Example 3 Groove shape on the inner wall of the stirring tank 〃 Groove depth 1 mm 〃 Groove width 3 mm 〃 Groove pitch 6 mm 〃 Mountain width 3 mm Distance between the tip of the stirring blade and the inner wall surface (convex part) 5 mm Stirring blade shape and number etc. 1 set per sheet] is 3 sets. One set is in the center of the rotary shaft,
The other two sets are mounted symmetrically with respect to the central one set.

Granulation time 40 minutes Particle diameter of obtained microspheres 328 μm 〃 sphericity 1.07 Particle diameter of firing balls after sintering of the above microspheres 262 μm 〃 sphericity 1.03 〃 Density 6.004 g / cm ³ Example 4 Groove shape on the inner wall of the stirring tank 〃 Groove depth 1 mm 〃 Groove width 3 mm 〃 Groove pitch 6 mm 〃 Mountain width 3 mm Distance between the stirring blade tip and inner wall surface (convex part) 5 mm Stirring blade shape and number [S type, 4 1 set per sheet] is 3 sets. One set is mounted at the center of the rotating shaft, and the other two sets are mounted at symmetrical positions with respect to the central one set.

Granulation time 45 minutes Particle diameter of the obtained microspheres 315 μm 〃 sphericity 1.03 Particle diameter of firing balls after sintering of the above microspheres 265 μm 〃 sphericity 1.03 〃 Density 6.001 g / cm ³ Example 5 Groove shape on the inner wall of the stirring tank 〃 Groove depth 1 mm 〃 Groove width 3 mm 〃 Groove pitch 6 mm 〃 Mountain width 3 mm Distance between the tip of the stirring blade and the inner wall surface (convex part) 5 mm Stirring blade shape and number etc. 3 sets, 1 set of 2 pieces and 1 set of [S type, 4 pieces 1 set], both sides are paddle type, S type is arranged in the center, and paddle type is for S type It is installed in a symmetrical position.

Granulation time 45 minutes Particle diameter of the obtained microspheres 322 μm 〃 sphericity 1.04 Particle diameter of firing balls after sintering of the above microspheres 258 μm 〃 sphericity 1.04 〃 Density 6.002 g / cm ³ Example 6 Groove shape on the inner wall of the stirring tank 〃 Groove depth 1 mm 〃 Groove width 3 mm 〃 Groove pitch 6 mm 〃 Mountain width 3 mm Distance between the tip of the stirring blade and the inner wall surface (convex part) 5 mm Stirring blade shape and number etc. 2 sets of one sheet] are mounted at positions at three equal points of the rotation axis length.

Granulation time 50 minutes (rotation speed 220 rpm) Particle diameter of the obtained microspheres 330 μm 〃 sphericity 1.04 Particle diameter of firing balls after sintering of the above microspheres 268 μm 〃 sphericity 1.04 〃 density 5.980g / cm ³ Example 7 Groove shape on the inner wall of the stirring tank 〃 Groove depth 2 mm 〃 Groove width 3 mm 〃 Groove pitch 6 mm 〃 Mountain width 3 mm Distance between the tip of the stirring blade and the inner wall surface (convex portion) 4 mm Stirring blade shape and number Etc. There are 3 sets of [paddle type, 4 sets of 1 set]. One set is in the center of the rotary shaft,
The other two sets are mounted symmetrically with respect to the central one set.

Granulation time 50 minutes Particle diameter of the obtained microspheres 314 μm 〃 sphericity 1.03 Particle diameter of firing balls after sintering the above microspheres 251 μm 〃 sphericity 1.03 〃 Density 6.024 g / cm ³ Example 8 Groove shape on the inner wall of the stirring tank 〃 Groove depth 3 mm 〃 Groove width 3 mm 〃 Groove pitch 6 mm 〃 Mountain width 3 mm Distance between the tip of the stirring blade and the inner wall surface (convex part) 3 mm Stirring blade shape and number etc. 1 set per sheet] is 3 sets. One set is in the center of the rotary shaft,
The remaining two sets are mounted symmetrically with respect to the central one set.

Granulation time 55 minutes Particle diameter of the obtained microspheres 252 μm 〃 sphericity 1.035 Particle diameter of fired balls after sintering of the above microspheres 210 μm 〃 sphericity 1.03 〃 Density 6.040 g / cm ³ Example 9 Groove shape on the inner wall of the stirring tank 〃 Groove depth 1mm 〃 Groove width 3mm 〃 Groove pitch 12mm 〃 Mountain width 9mm Distance between the tip of the stirring blade and the inner wall surface (convex part) 5mm Shape and number of stirring blades [Paper type, 4 1 set per sheet] is 3 sets. One set is in the center of the rotary shaft,
The remaining two sets are mounted symmetrically with respect to the central one set.

Granulation time 55 minutes Particle diameter of the obtained microspheres 580 μm 〃 sphericity 1.04 Particle diameter of firing balls after sintering of the above microspheres 464 μm 〃 sphericity 1.04 〃 Density 5.993 g / cm ³ Example 10 Groove shape on the inner wall of the stirring tank 〃 Groove depth 1mm 〃 Groove width 3mm 〃 Groove pitch 24mm 〃 Mountain width 21mm Distance between the tip of the stirring blade and the inner wall surface (convex part) 5mm Stirring blade shape and number etc. 1 set per sheet] is 3 sets. One set is in the center of the rotary shaft,
The remaining two sets are mounted symmetrically with respect to the central one set.

Granulation time 50 minutes Particle diameter of the obtained microspheres 792 μm 〃 sphericity 1.04 Particle diameter of firing balls after sintering of the above microspheres 634 μm 〃 sphericity 1.04 〃 Density 5.957g / cm ³ Example 11 Groove shape on the inner wall of the stirring tank 〃 Groove depth 1mm 〃 Groove width 3mm 〃 Groove pitch 48mm 〃 Mountain width 45mm Distance between the tip of the stirring blade and inner wall surface (convex part) 5mm Stirring blade shape and number etc. 1 set per sheet] is 3 sets. One set in the center of the rotary shaft,
The other two sets are mounted symmetrically with respect to the central one set.

Granulation time 50 minutes Particle diameter of microspheres obtained 876 μm 〃 sphericity 1.04 Particle diameter of firing balls after sintering of the above microspheres 701 μm 〃 sphericity 1.04 〃 Density 5.957g / cm ³ Example 12 Groove shape on the inner wall of the stirring tank 〃 Groove depth 1 mm 〃 Groove width 3 mm 〃 Groove pitch 243 mm 〃 Mountain width 240 mm Distance between the tip of the stirring blade and the inner wall surface (convex portion) 5 mm Stirring blade shape and number, etc. 1 set per sheet] is 3 sets. One set in the center of the rotary shaft,
The other two sets are mounted symmetrically with respect to the central one set.

Granulation time 105 minutes Particle diameter of obtained microspheres 1323 μm 〃 sphericity 1.04 Particle diameter of fired balls after sintering of the above microspheres 1058 μm 〃 sphericity 1.04 〃 Density 5.913g / cm ³ Example 13 Groove shape on the inner wall of the stirring tank Arc type 〃 Groove depth 1mm 〃 Groove width 3mm 〃 Groove pitch 6mm 〃 Mountain width 3mm Distance between the tip of the stirring blade and inner wall surface (convex part) 5mm Stirring blade shape and number etc. 4 sets are 1 set] 3 sets. One set is mounted at the center of the rotating shaft, and the other two sets are mounted at symmetrical positions with respect to the central one set.

Granulation time 65 minutes Particle diameter of the obtained microspheres 330 μm 〃 sphericity 1.04 Particle diameter of firing balls after sintering of the above microspheres 264 μm 〃 sphericity 1.04 〃 Density 5.990 g / cm ³ Example 14 Groove shape on the inner wall of the stirring tank V type 〃 Groove depth 1 mm 〃 Groove width 3 mm 〃 Groove pitch 6 mm 〃 Mountain width 3 mm Distance between the stirring blade tip and inner wall surface (convex part) 5 mm Stirring blade shape and number etc. 4 sets are 1 set] 3 sets. One set is mounted at the center of the rotating shaft, and the other two sets are mounted at symmetrical positions with respect to the central one set.

Granulation time 70 minutes Particle diameter of the obtained microspheres 345 μm 〃 sphericity 1.05 Particle diameter of firing balls after sintering of the above microspheres 276 μm 〃 sphericity 1.04 〃 Density 5.987g / cm ³ Example 15 Groove shape on the inner wall of the stirring tank 〃 Groove depth 1 mm 〃 Groove width 3 mm 〃 Groove pitch 6 mm 〃 Mountain width 3 mm Distance between the tip of the stirring blade and the inner wall surface (convex part) 5 mm Stirring blade shape and number etc. 1 set per sheet] is 3 sets. One set is mounted at the center of the rotating shaft, and the other two sets are mounted at symmetrical positions with respect to the central one set.

Rotating blade rotation speed 1450 rpm Granulation time 125 minutes Particle diameter of the obtained microspheres 71 μm 〃 sphericity 1.03 Particle diameter of fired balls after sintering of the above microspheres 57 μm 〃 sphericity 1.03 〃 Density 6.002g / cm ³ Note: The specific surface area of the zirconia powder used in Example 15 is
At 28.5 m ² / g, the other properties were substantially the same as those in Examples 1-14.

Example 16 The powder used was commercially available alumina, and its main properties were as follows.

Specific surface area: 7.0 m ² / g (BET method for measurement) True specific gravity: 3.94 (JIS H1902 method for measurement) Average particle diameter (50% weight): 0.5 μm (SEDIGRAPH 5000 D) Component analysis: Al ₂ O ₃ 99.8 (wt%) Na ₂ O 0.02 MgO 0.04 Granulation conditions Amount of alumina powder …… 80 g Organic solvent and its amount …… Paraffin hydrocarbon, 2800 ml Binder and its amount ………… Water Water, 15 ml Groove shape on inner wall of agitator for granulator 〃 Groove depth 1 mm 〃 Groove width 1 mm 〃 Groove pitch 2 mm 〃 Mountain width 1 mm Distance between tip of agitating blade and inner wall surface (convex part) 10 mm Agitating blade shape and number, etc. There are 3 sets of [paddle type, 4 sets are 1 set]. One set is installed at the center of rotation, and the other two sets are installed symmetrically with respect to the central set.

Rotating blade rotation speed: 2200 rpm Granulation time: 90 minutes Particle diameter of the obtained microsphere pair: 340 μm 〃 sphericity: 1.05 After sintering the above microsphere pair (calcination of maximum temperature 1500 ° C for 2 hours Particle diameter of balls: 272 μm 〃 sphericity: 1.05 〃 Density: 3.96 g / cm ³ Example 17 The powder used was commercially available silicon nitride, and the main properties were as follows.

Specific surface area …… 11.1 m ² g Average particle size (50% weight) …… 0.2 μm Component analysis …… N> 38 (weight%) Si> 59 〃 O 1.29 〃 Cl <100ppm Fe <100 〃 Ca <50 〃 Al <50 〃 Crystallinity (% by weight)> 99.5 Granulation conditions Amount of silicon nitride powder: 80 g Organic solvent and its amount: Paraffin hydrocarbon, 2800 ml Binder and its amount: Tap water, 15.5 ml Granulator Stirrer inner wall groove type 〃 Groove depth 1mm 〃 Groove width 3mm 〃 Groove pitch 6mm 〃 Mountain width 3mm Distance between the stirring blade tip and inner wall surface (convex) 5mm Stirring blade shape and number etc. 4 sets, 1 set] is 3 sets. One set is mounted at the center of the rotating shaft, and the other two sets are mounted at symmetrical positions with respect to the central one set.

Rotating blade rotation speed: 2150 rpm Granulation time: 115 minutes Particle diameter of the obtained microspheres: 374 μm 〃 sphericity: 1.02 Outlines of Examples 1 to 17 are shown in Tables 1 and 2 It was shown to.

(Effects of the Invention) With the granulator of the present invention, it is possible to produce a fine ceramic microsphere having a high sphericity and a high sphericity with a diameter of 50 to 500 μm, which cannot be obtained by the conventional method.

Further, the fired balls produced by sintering the microspheres produced by the granulator of the present invention have high hardness, high sphericity, and excellent abrasion resistance. It is possible to grind, disperse, and mix fine ceramics raw materials or grind and disperse pigments efficiently in a short time in a mill using as a medium, and without foreign matter such as abrasion powder being mixed.

[Brief description of drawings]

FIG. 1 is a sectional view of the cylindrical stirring tank of the present application in the direction of the rotation axis. In FIG. 1, 1 ... Cylindrical stirring tank 2 ... Rotating stirring blade 3 ... Rotating shaft 4 ... Groove 5 ... Bearing FIGS. 2-1 to 2-3 are cross-sectional views showing the cross section of the groove when the cylindrical stirring tank of the present application is cut along a plane perpendicular to the rotation axis,
2-1 is a cross-sectional view when the cross section of the groove is U-shaped, 2-2
The drawing is a sectional view when the groove has a V-shaped cross section, and FIG. 2-3 is a sectional view when the groove has an arc-shaped cross section. In FIG. 2, 11 ... Groove depth, 12 ... Groove width 13 ... Groove pitch, 14 ... Crest width 15 ... Convex portion.

 ─────────────────────────────────────────────────── ─── Continued Front Page (56) References JP 61-35836 (JP, A) JP 56-14449 (JP, B2)

Claims (3)

[Claims] 1. A submerged granulator for producing a granulated product by placing fine powder, a solvent and a binder in a cylindrical stirring tank equipped with a rotary stirring blade, and producing a granulated product by using the cylindrical stirring tank. The inner wall surface has a shape with concave and convex grooves, and the concave and convex grooves have a mold, V-shaped or arc-shaped cross section when the stirring tank is cut along a plane perpendicular to the rotation axis of the rotary stirring blade. An in-liquid granulator characterized in that 2. The submerged granulator according to claim 1, wherein the groove is parallel to the rotation axis of the rotary stirring blade. 3. The submerged granulator according to claim 1, wherein the distance between the tip of the rotary stirring blade and the convex portion on the inner wall surface of the cylindrical stirring tank is 2 to 15 mm.