Colloid systems and wetting agents; subcombinations thereof; pro – Continuous liquid or supercritical phase: colloid systems;... – Aqueous continuous liquid phase and discontinuous phase...
Reexamination Certificate
1999-03-01
2001-01-23
Lovering, Richard D. (Department: 1712)
Colloid systems and wetting agents; subcombinations thereof; pro
Continuous liquid or supercritical phase: colloid systems;...
Aqueous continuous liquid phase and discontinuous phase...
C264S011000, C366S173100, C366S176100, C366S176400, C514S937000, C514S941000, C516S924000
Reexamination Certificate
active
06177479
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a manufacturing method for microspheres (including emulsions and fine particles suspended in liquid) used in the food industry, the manufacturing of drugs and cosmetics, etc., and to an apparatus for carrying out the method.
2. Description of Related Art
Techniques in which a biphasic system, for which a separated state is thermodynamically stable, is formed, such as that composed of a water phase and an organic phase which are emulsified to obtain a semi-stable emulsion, are conventionally known. As general, well-known emulsification methods, there have been described in “Science of Emulsions” (Asakura-shoten, 1971), the methods of using a mixer, a colloid mill, a homogenizer, etc., and the method of dispersion with sound waves.
The general methods mentioned above have a disadvantage in that the diameters of dispersed phase particles in a continuous phase are distributed over a wide range.
Therefore, a method of using filtration by means of a membrane comprising polycarbonate (Biochemica et Biophysica Acta, 557 (1979), North Holland Biochemical Press); a method using repeated filtrations through a PTFE (polytetrafluoroethylene) membrane (Proceedings of the 26th Autumn Meeting of the Society of Chemical Engineers, Japan, 1993); and, a method of manufacturing homogenous emulsions by transferring a dispersed phase into a continuous phase through a porous glass membrane having uniform pores (Japanese Patent Application Laid-Open Nos. 2-95433, 5-220382 and 6-315617), have been proposed.
In addition, a method of manufacturing emulsions via fine pores formed in a membrane filter with a dry etching process or a wet etching process has been proposed in Japanese Patent Application Laid-Open No. 6-71150, a method of manufacturing emulsions by transferring a dispersed phase into a continuous phase through a nozzle has been proposed in Japanese Patent Application Laid-Open No. 60-5223, and a method of producing emulsions using a porous plate has been proposed in Japanese Patent Application Laid-Open No. 54-116389. In addition, a laminar-flow dripping method (KAGAKU KOOGAKU Vol. 21, No. 4, 1957) is also known.
Furthermore, a method of producing emulsions by transferring a dispersed phase into a continuous phase through microchannels having a predetermined width has been proposed (JAOCS, 74, 1997, pp. 317-321).
The method using filtration through a membrane comprising polycarbonate and the method using repeated filtrations through a PTFE membrane theoretically cannot manufacture emulsions comprising particles larger than the membrane pores and cannot separate particles smaller than the membrane pores. These methods are, therefore, especially unsuitable for producing emulsions comprising large particles.
In the method using a porous glass membrane having uniform pores, when the average diameter of the membrane pores is small, particle diameters are distributed in a narrow range and thus homogenous emulsions can be obtained. When the average diameter of the membrane pores is increased, however, particle diameters become distributed over a wide range so that homogenous emulsions cannot be obtained. In addition, in the laminar-flow dripping method using a nozzle or a porous plate, particle sizes become 1,000 &mgr;m or more and are distributed over a wide range so that homogenous emulsions cannot be obtained.
In the method using microchannels having a predetermined width described in—JAOCS, 74, 1997, pp. 317-321—, homogenous emulsions can be obtained. However, as the method is a batch-type method, emulsions cannot be continuously produced. When the diameter of the channels is increased, the size of produced emulsions becomes large, and the emulsions cannot travel and unite with each other, so that homogenous emulsions cannot be obtained.
Therefore, the inventors of the present invention formerly proposed an apparatus which can continuously produce homogenous emulsions in International Publication No. W)97/30783.
The structure of this apparatus is shown in FIG.
14
. In this apparatus for producing emulsions, a supply port
101
for a continuous phase (W) is formed in a side wall of a body
100
, a supply port
103
for a dispersed phase (O) is formed in the center of a lid
102
which closes an upper opening of the body
100
, and one or more withdrawal ports
104
for emulsions (E) are formed at a place apart from the center. A bulkhead member
106
formed between the lid
102
and a base
105
separates the supply port
103
for the dispersed phase (O) from the withdrawal ports
104
for emulsions (E). In addition, a supply port
107
for the dispersed phase (O) is formed in the center part of the base
105
, a gap
109
is formed between the base
105
and a plate
108
placed opposite the base
105
. In a boundary section
110
formed in the base
105
the dispersed phase (O) and the continuous phase (W) are separated, and, in a microchannel
111
formed in the boundary section
110
, the dispersed phase (O) and the continuous phase (W) are mixed.
The dispersed phase (O) supplied to the inside of the bulkhead member
106
via the supply port
103
enters the gap
109
between the plate
108
and the base
105
via the supply port
107
and this dispersed phase (O) enters the continuous phase (W) through the boundary section
110
, thereby forming emulsions.
With the above-mentioned apparatus, homogenous emulsions can be continuously obtained. However, it is necessary to supply power in order to withdraw emulsions and there is room for improvement with respect to the cost.
SUMMARY OF THE INVENTION
To solve the above-mentioned problems, there is provided in accordance with the present invention a method for continuously manufacturing microspheres comprising the steps of: transferring a pressurized dispersed phase into a continuous phase by force via a plurality of microchannels having a predetermined width to produce emulsions and withdrawing microspheres in the form of produced emulsions and fine particles suspended in liquid, etc., with the microspheres floating and sinking in response to their specific gravity.
There is also provided in accordance with the present invention an apparatus for continuously manufacturing microspheres comprising: a base oriented in a substantially vertical direction or inclined, a plate placed opposite the base, a supply port for a dispersed phase formed in the base and a boundary section formed in the side opposite to the plate of the base for dividing the space into which the dispersed phase is supplied and the space into which the continuous phase is supplied, wherein a plurality of microchannels having a predetermined width are formed at a position from which microspheres can be withdrawn by floating and sinking in response to their specific gravity, and further wherein the dispersed phase comes into contact with the continuous phase via the microchannels.
It is possible to make the plate placed opposite the base transparent. As a result of this, it is possible to directly visually observe the motion of the dispersed phase in the microchannels and the contact condition of the dispersed phase with the continuous phase, and to control the production of microspheres based on such observations.
It is also possible to efficiently produce microspheres according to the present invention by providing a boundary section in which a plurality of microchannels are formed to surround the supply port of the dispersed phase.
For use in the apparatus of the invention, it is possible to form a plurality of microchannels having arbitrary form and a predetermined width in the base by adopting an etching process used in the process of forming integrated circuits for semiconductors as the method of forming the microchannels.
In general, as disclosed in International Publication No. WO97/30783, the microchannels may be formed by subjecting the base to an etching treatment, irradiation of electron rays, or a precision processing technique, such as a CVD method or the like.
REFERENCES:
patent:
Kawakatsu Takahiro
Kikuchi Yuji
Kobayashi Isao
Nabetani Hiroshi
Nakajima Mitsutoshi
Blackman William D.
Carrier Joseph P.
Carrier Blackman & Associates P.C.
Japan as represented by Director of National Food Research Insti
Lovering Richard D.
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