JP2006021111A - Particle forming method and particle, and multiplex particle forming method and multiplex particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a particle forming method or the like, which can form a large amount of particles uniform in a particle diameter even if the viscosity of a particle forming material is high. <P>SOLUTION: The particle forming method is comprised of separating and holding a continuous phase and a disperse phase through a separation membrane having one or more openings, moving the disperse phase from the opening formed on the separation membrane to the continuous phase side to shear near the separation membrane and form the particle of the disperse phase material, the section in a thickness direction of the opening formed on the separation membrane having a shape narrowed from the disperse phase side toward continuous phase side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a particle forming method, particles, a multiple particle forming method, and multiple particles for forming fine particles such as spacers, toner, and microcapsules for electronic paper.

Even a substance such as water and oil that is not originally mixed can be apparently mixed by dispersing one substance as fine particles, and this phenomenon is called emulsification. In order to maintain such a state, the dispersed particles need to be small in size and relatively uniform, and this phenomenon is used to obtain fine particles having a small particle size distribution.
It is publicly known that the following methods are specifically used as an emulsification method.

(1) Emulsification with a homogenizer (see Patent Document 1)
This is because a substance to be finely dispersed is added to a liquid called a continuous phase and mechanically stirred to repeatedly apply a shearing force to obtain an emulsified dispersion. Since the force is not uniform depending on the emulsifying position, fine particles having a wide particle size distribution are generated. Since fine particles having a wide particle size distribution are likely to coalesce with each other with the lapse of time after generation, a countermeasure is generally taken to avoid this by adding a large amount of a surfactant to stabilize the particles. However, the surfactant is often unnecessary as a function of the particles, and sometimes has an adverse effect. Therefore, it is usually necessary to wash and remove a large amount of water resources in the subsequent process. Further, the particle size distribution can be suppressed to some extent by taking a long stirring time, but this requires a long time and a lot of energy.

(2) Emulsification using a porous glass membrane (see Patent Document 2 etc.)
The dispersed phase and continuous phase are separated by a porous glass membrane, and the dispersed phase passes through the membrane by extruding the dispersed phase to the continuous phase side. This is a method for obtaining an emulsified dispersion. However, the hole shape of the porous glass membrane is composed of a relatively smooth continuous curve, and the surface tension acting on the extruded interface works relatively uniformly, so it does not readily shear, and the resulting particle size is open. It will be bigger than. Further, since the hole shape and size are not constant, the particle size distribution is narrower than the method (1) but relatively wide.

(3) Emulsification using partition walls with artificially formed micro-openings (see Patent Document 3 etc.)
The dispersed phase and the continuous phase are partitioned by partition walls in which a large number of non-circular openings having the same shape are artificially formed by a semiconductor process, and the dispersed phase is extruded to the continuous phase through the openings to obtain fine particles. At this time, since the opening shape is non-circular such as a slit shape, the surface tension works non-uniformly so that it can be easily sheared and particles having a small particle size distribution can be obtained. However, the disclosed opening shape of the partition wall is a parallel through-hole whose cross-sectional shape does not change with respect to the thickness direction of the partition wall. It would be difficult to extrude into the continuous phase when Conversely, when the partition wall is made thinner, extrusion becomes relatively easy, but problems such as deformation and destruction of the partition wall due to the pressure applied during extrusion can be considered.
Japanese Patent No. 3476223 Japanese Patent No. 2733729 Japanese Patent No. 3511238

  In view of the above problems, the present invention provides a particle forming method, particles, multiple particle forming method, and multiple particles that can form a large amount of particles having a uniform particle size even when the viscosity of the particle forming material is particularly high. The purpose is to do.

In an embodiment of the present invention that achieves the above object, a continuous phase and a dispersed phase are separated and held through a separation membrane having one or more openings, and the dispersed phase is placed on the continuous phase side from the openings formed in the separation membrane. In the particle forming method of forming a dispersed phase material particle by shearing in the vicinity of the separation membrane, the cross section in the thickness direction of the opening formed in the separation membrane is directed from the dispersed phase side to the continuous phase side. This is done through a narrowed opening.
In this method, the shape of the opening formed in the separation membrane is narrowed from the dispersed phase side to the continuous phase side, so that even when a highly viscous material is used for the dispersed phase, it moves to the continuous phase side. As a result, particles having a uniform size can be formed regardless of the viscosity.

Here, the movement of the dispersed phase through the opening is such that the ratio of the cross section in the thickness direction of the opening of the separation membrane used in this method becomes narrower from the dispersed phase side toward the continuous phase side becomes smaller toward the continuous phase side. Is done.
In this method, the ratio of the cross-sectional shape of the opening of the separation membrane to be narrowed is such that it becomes smaller toward the continuous phase, so that the separation membrane has a sufficient thickness even in the vicinity of the opening. It is possible to stably form particles having a uniform size without deformation or destruction.

In the above method, the dispersed phase is moved through a separation membrane having an opening having a shape other than a circle when viewed from the continuous phase side.
In this method, since the opening shape seen from the continuous phase is non-circular, the surface tension acting as a shearing force acts non-uniformly, so the size is uniform with a relatively small volume with respect to the size of the opening. Particle formation can be performed.

In the above method, the dispersed phase is moved through two or more openings having the same shape provided in the separation membrane.
In this method, since particles can be formed from openings having a plurality of shapes, the productivity of particles having the same shape is excellent.

At this time, in this method, the separation membrane in which two or more openings having the same shape are formed in the same direction is used, the dispersed phase is moved to the continuous phase side, and a constant amount is provided between the continuous phase and the separation membrane. Create a speed difference.
In this method, since the dispersed phase moves to the continuous phase from a plurality of openings having the same shape and the same direction, and a constant speed difference is formed between the separation membrane and the continuous phase, shearing due to surface tension is caused. Both the force and the shearing force resulting from the speed difference between the separation membrane and the continuous phase are added, and they work in the same way on the dispersed phase from any opening, so that the productivity of uniform particles is excellent.

In the above method, the dispersed phase is continuously moved to the continuous phase side at a constant speed.
In this method, since the disperse phase is continuously moved to the disperse phase at a constant speed, the particle formation operation is repeatedly performed at a constant speed, so that uniform particle formation can be continuously performed.

Further, in the above method, the dispersed phase is moved to the continuous phase side at a constant cycle speed fluctuation.
In the above method, since the disperse phase is continuously supplied to the continuous phase side at a constant period of speed fluctuation, the formation of a constant volume of particles can be repeated, so that uniform particle formation can be continuously performed.

At this time, in this method, the opening of the separation membrane is opened and closed at regular time intervals.
In this method, since the separation membrane is opened and closed at regular intervals, the dispersed phase can be made into particles with a volume corresponding to the opening and closing time, and uniform particle formation is possible.

In the above method, vibration is applied to the separation membrane.
In this method, since vibration is applied to the separation membrane, the shearing force due to the separation membrane is added to the shearing force due to the surface tension, and a larger shearing force can be repeatedly applied.

  And the particle | grains produced by the said method are high quality particle | grains by which the uniform surfactant and the unnecessary surfactant are excluded.

In another aspect of the present invention, the continuous phase in which the particles obtained by the above method are dispersed is used as the second dispersed phase, and the above-described method is performed using the second dispersed phase and the second continuous phase that are not mutually soluble. The present invention relates to a method for forming multiple particles.
In this method for forming multiple particles, a continuous phase in which particles obtained by the above-described method are dispersed is used as the second dispersed phase, and multiple particles are formed by the above-described method. Particles can be produced.

  The multi-particles produced by this method are of a high quality in which both the inner particles and the outer shell particles have a uniform size and unnecessary components are eliminated.

  According to the present invention, a large amount of particles having a uniform particle size can be formed even when the viscosity of the particle forming material is particularly high.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows an example of a particle production method according to this embodiment. Oil is used as the dispersed phase and water is used as the continuous phase, and these communicate with each other only through the opening of the separation membrane. In such a configuration, in the example shown in the figure, the dispersed phase is pressurized by a third substance such as air to move to the continuous phase side through the separation membrane opening. The dispersed phase that has entered the continuous phase through the opening of the separation membrane tends to be spheroidized by surface tension. The shearing force generated at this time separates from the dispersed phase to form particles. The obtained particle size can be controlled by the shape of the surface on the continuous phase side of the separation membrane opening, the moving speed of the dispersed phase, the surface tension at the interface between the dispersed phase and the continuous phase, and the like.

The flow rate Q of the dispersed phase passing through the separation membrane is as follows. The pressure at the separation membrane inlet is p1, the pressure at the separation membrane outlet is p2, and the conductance is C.
Q = C × (p1-p2)
It is represented by

The conductance C is defined as follows. When the opening formed in the separation membrane is cylindrical, the radius is a, the viscosity coefficient η, the thickness L of the separation membrane, and the average pressure p = (p1−p2) / 2.
C = (πa ⁴ p / 8η) / L
It is expressed by
Q = (πa ⁴ p / 8η) / L × (p1−p2)
It becomes.

  In order to form a certain amount of particles per unit time, if the material volume Q is allowed to pass, if a material having a large viscosity η is used for the dispersed phase from this equation, the pressure p1 on the dispersed phase side is increased. It is necessary to increase the cylindrical shape a or decrease the separation film thickness L or a combination thereof. However, increasing p1 leads to an increase in impossibility of the apparatus, expanding a increases the generated particle diameter, and decreasing L decreases the mechanical strength of the separation membrane. On the other hand, as proposed in the present invention, the influence of these can be reduced by making the opening of the separation membrane so that the opening is larger on the dispersed phase side and smaller as it goes to the continuous phase side. That is, even if the opening diameter of the portion in contact with the continuous phase that determines the size of the particles is the same, the opening diameter on the dispersed phase side is large and the value of a is apparently larger than the actual value. As a result, the value of p1 may be small. These effects can be achieved by setting the shape of the opening having such a shape as shown in FIGS.

  Further, since the acting direction of the stress between the dispersed phase and the opening wall surface generated when extruding the dispersed phase works in the normal direction, the ratio of the smaller opening cross section becomes smaller as it goes to the continuous phase side as shown in FIG. By adopting the shape, the separation membrane can be operated in a direction deviated from the film thickness direction having the weakest mechanical strength, so that the influence of a decrease in mechanical strength can also be reduced.

  As described above, in the process of forming particles, particles are formed by separating the surface tension of the dispersed phase that has moved into the continuous phase as a shearing force. If the volume is the same, the spherical shape has the smallest surface area and the smallest surface tension. When the cross section is considered, if the cross section is the same, a circle is the shortest in circumference and the surface tension is also small. However, if the cross section is a non-circular shape such as a triangle as shown in FIG. 12, for example, a force for forming a circular cross section acts. In particular, when the shape has clear concave or convex vertices, a large force acts in the vicinity of the vertices, so that this portion can be used as a shear start point to cause separation from the continuous phase. As a result, it is possible to obtain a uniform particle size obtained by shearing from a stable position at a relatively early stage.

  FIG. 2 shows an example in which the dispersed phase is directly pressurized using a syringe pump or the like without interposing a third substance in the movement of the dispersed phase. By adopting such a configuration, it is possible to prevent the third substance from being dissolved in the dispersed phase.

  FIG. 6 shows an embodiment of a method for forming a constant speed difference between the separation membrane and the continuous phase. A dispersed phase is put inside the cylindrical body, and an opening is formed in at least a part of the cylindrical surface of the cylindrical body, which acts as a separation membrane. At least a part of the cylindrical body that becomes a separation membrane is in a continuous phase, and the continuous phase forms a constant-speed rotating flow by a rotating stirrer or the like. With such an arrangement, the center of the rotating flow and the center of the cylinder pair containing the dispersed phase coincide with each other, so that the separation membrane formed in the cylindrical body and the continuous phase have a constant speed. When the dispersed phase is moved to the continuous phase through the separation membrane in such a state, a constant shearing force in a certain direction is generated due to a difference in moving speed between the separation membrane and the continuous phase as shown in FIG. At this time, by keeping the direction of the opening formed in the separation membrane part constant, the direction of the shearing force due to the surface tension becomes constant. Accordingly, particles having a uniform size can be formed. At this time, the shearing force can be applied more efficiently by arranging the portion where the shearing force due to the surface tension works most so as to be located in the upstream direction with respect to the moving speed of the separation membrane and the continuous phase. By increasing the shearing force in this way, the effect of improving the particle generation rate can also be obtained.

  FIG. 8 is an explanatory view of a method of forming particles using an opening / closing means provided in the opening of the separation membrane. The dispersed phase has a certain volume in the continuous phase after a certain time has elapsed from the start of movement to the continuous phase. In this state, the disperse phase in the continuous phase can be separated and particles can be formed by moving the opening / closing means as shown in the figure. Thereafter, the disperse phase is moved into the continuous phase by moving the opening / closing means and opening the opening. By repeating this operation, particles are continuously formed. By matching the opening / closing timing with the timing at which a certain amount of the dispersed phase moves into the continuous phase, particles having a constant volume, that is, a uniform size can be formed. The opening / closing means may be formed on the continuous phase side of the separation membrane as shown in FIG. 8, or may be formed on the dispersed phase side as shown in FIG.

  Further, a shearing force can be applied to the dispersed phase by applying vibration to the separation membrane. This may be a vibration with a constant period and intensity, or may be given a pulse-like vibration at the timing at which particles are to be formed.

  The particles thus obtained have a uniform size. Even if the particles having the same size are brought into contact with each other in the continuous phase after formation, they are not easily combined to become larger particles. Therefore, it is possible to reduce the amount of surfactant usually used in the dispersed phase and the continuous phase in order to obtain a stable particle state. Surfactants are often unnecessary as the original function of the particles, and may have an adverse effect, and it was necessary to add and remove a washing step after the particles were formed. It can be greatly reduced.

  FIG. 10 is an explanatory view of a method for producing multiple particles. The continuous phase in which particles are previously formed and dispersed by the method as described above is used as the second dispersed phase, and the first is passed through the separation membrane having an opening larger than the opening of the separation membrane used when forming the second dispersed phase. The two dispersed phases are moved into the second continuous phase. By using the same method for moving the dispersed phase to the continuous phase to form particles, particles made of the second dispersed phase material including the particles made of the dispersed phase material can be obtained. At this time, when water is used as the dispersed phase and oil is used as the continuous phase, water is used as the second continuous phase. When oil is used as the dispersed phase and water is used as the continuous phase, oil is used as the second continuous phase. Multiple particles can be formed by using.

  As shown in FIG. 3, the manufacturing method of the separation membrane in which the opening on the continuous phase side is smaller than the dispersed phase side used in this embodiment has a shape in which the opening cross-section is linearly reduced, and the taper angle at the tip. It can be formed by machining or pressing with a rotary tool with a mark. The shape shown in FIG. 4 can be produced by isotropic etching as shown in FIG. FIG. 14 is a plan view of 3) and 5) of FIG. An opening having a shape as shown in 4) of FIG. 14 can be formed by forming an opening in the protective phase and performing isotropic etching through this opening as shown in 3) hatched part of FIG. The cross section at this time can be obtained by changing the size of the opening shape as shown in 5) of FIG. The shape shown in FIG. 5 can be produced by an electroplating method as shown in FIG. FIG. 12 is a plan view of 3) and 5) of FIG. An insulating layer is patterned on the conductive substrate in a shape similar to the opening. Thereafter, by performing electroplating on the substrate, a separation film having openings similar to the patterned insulating film can be obtained.

  In any of these methods, since a separation membrane made of a metal material can be obtained, a separation membrane having a high mechanical strength can be produced, which is suitable for forming particles using a high-viscosity dispersed phase. It is also possible to make the thickness bendable, and it is possible to bend and fix to the surface of the cylindrical body after being formed on a flat plate.

  In addition, although the form mentioned above is the best thing for implementing this invention, it is not the main point limited to this. Therefore, various modifications can be made without departing from the scope of the present invention.

  Development of an apparatus for producing fine particles to which the present invention is applied is desired, and in particular, development of an emulsion for foods, cosmetics and the like and an apparatus for producing the emulsion are desired.

It is one Example of the particle production method by this embodiment. In this example, the dispersed phase is directly pressurized using a syringe pump or the like without interposing a third substance in the movement of the dispersed phase. It is one of the cross sections of the shape of the separation membrane opening. It is one of the cross sections of the shape of the separation membrane opening. It is one of the cross sections of the shape of the separation membrane opening. It is one Example of the method of forming a fixed speed difference between a separation membrane and a continuous phase. It is a figure regarding the shear force which arises by implementing the method which concerns on the Example of FIG. 6, and arises by the moving speed difference of a separation membrane and a continuous phase. It is explanatory drawing of the method of providing an opening-closing means in the opening part of a separation membrane, and forming particle | grains using this. It is explanatory drawing of the method of forming a particle | grain using the opening / closing means provided in the continuous phase side of a separation membrane. It is explanatory drawing about the method of producing multiparticle. It is explanatory drawing when producing the shape of the separation membrane opening shown in FIG. 5 by the electroplating method. FIG. 11 is a plan view of 3) and 5). It is explanatory drawing when producing the shape of the separation-film opening shown in FIG. 4 by isotropic etching. It is the figure which planarly viewed 3) and 5) of FIG.

Claims (12)

The continuous phase and the dispersed phase are separated and held through a separation membrane having one or more openings, and the dispersed phase is moved to the continuous phase side from the openings formed in the separation membrane and sheared in the vicinity of the separation membrane. In a particle forming method for forming particles of a dispersed phase material,
A method of forming particles, wherein the method is performed through an opening having a shape in which a cross section in the thickness direction of the opening formed in the separation membrane is narrowed from the dispersed phase side toward the continuous phase side.   2. The dispersed phase through the opening such that the thickness direction cross-section of the opening of the separation membrane used in the method according to claim 1 decreases from the dispersed phase side toward the continuous phase side. The particle formation method characterized by the above-mentioned movement.   3. The particle forming method according to claim 1, wherein the dispersed phase is moved through a separation membrane having an opening having a shape other than a circle when viewed from the continuous phase side.   The particle forming method according to claim 1, wherein the dispersed phase is moved through two or more openings having the same shape provided in the separation membrane.   5. The method according to claim 4, wherein the separation membrane in which two or more equally-shaped openings are formed in the same direction is used, the dispersed phase is moved to the continuous phase side, and the continuous phase and the separation membrane are interposed. A particle forming method characterized by forming a constant speed difference.   6. The particle forming method according to claim 1, wherein the dispersed phase is continuously moved to the continuous phase side at a constant speed.   6. The particle forming method according to claim 1, wherein the dispersed phase is moved to the continuous phase side at a constant cycle speed fluctuation.   8. The particle forming method according to claim 6, wherein the opening of the separation membrane is opened and closed at regular time intervals.   9. The particle forming method according to claim 1, wherein vibration is applied to the separation membrane.   Particles produced by the method according to any one of claims 1 to 9.   The continuous phase in which the particles obtained by the method according to any one of claims 1 to 9 are dispersed is defined as a second dispersed phase, and the second dispersed phase and the second continuous phase insoluble in each other. A method for forming multiple particles, wherein the method according to any one of 1 to 9 is performed.   Multi-particles made by the method of claim 11.

Images