US2917386A - Homogenizing method and apparatus - Google Patents

Description

Dec 15, 1959 J. B. JONES ETAL 2,917,386

HOMOGENIZING METHOD AND APPARATUS Filed Sept. 9, 1955 Fig.

INVENTOR. I JAMES B. JONES ,9. 2 KENNETH H. YOCOM v MAW ATTORNEY 2,917,386 HOMOGENIZING METHOD AND APPARATUS B. Jones and Kenneth H. Yocom, West Chester, Chester, Pa.,

James Pa., assignors to Aeroprojects, Inc., West a corporation of Pennsylvania Application September 9, 1955, Serial No. 533,279 13- Claims. (Cl. 99-63) The present invention relates to a method for forming stable homogenized mixtures, and more particularly, to a method for forming emulsions, suspensions, and colloidal mixtures. For example, the method of the present invention may be applied to the production of emulsions consisting of a plurality of liquids which do not appreciably dissolve in each other, but in which one of the liquids is suspended in the form of minute droplets in the other liquid; or a mixture of minute solid particles suspended in a liquid; or colloidal mixtures consisting of a dispersed phase of minute solid or fluid particles surrounded by a dispersion medium consisting of another fluid. The present invention is also directed to apparatus for forming homogenized mixtures.

There are numerous emulsion, suspension and colloidal systems of great commercial importance, as for example dispersions of silver halide particles in gelatin and water colloidal systems; various dairy products such as milk and cream; mixtures comprising oil and water;

beverages; paints and pigments; etc. A desirable attribute of each of the foregoing emulsion, suspension, and colloidal systems, is that such systems remain stable; namely that the dispersed phase must not separate from the dispersion medium, or tend to coagulate, or precipitate.

The formation of stable colloidal, suspension and emulsion systems by conventional means has frequently proved to be most costly and difficult. Emulsions having great utility in which this problem is present are aqueous emulsions of gelatin and silver halide used as the photosensitive medium in photographic films. With such emulsions the silver halide should be evenly dispersed as minute suspended particles in order that a photoemulsion of desirable properties may be obtained. Elaborate mechanisms and complex procedures have heretofore been adopted for breaking up or, preventing the formation of agglomerates of silver halide in order to form stable photoemulsions.

Similar difficulties are encountered with the wetting of other solid particles, such as barium sulfate, dried food particles, etc.

The problem is acute with certain paints, wherein the wetting of the pigment by the paint vehicle is effected only with great difliculty.

This invention has as an object the provision of a method whereby stable homogeneous emulsions, or suspensions or colloidal systems may readily and quickly be formed from substances which are substantially insoluble in each other.

This invention has as a further object the provision of a method whereby emulsions or suspensions are formed from agglomerates. I

This invention has as another object the provision of a method whereby emulsions or colloidal solutions containing dispersed particles of uniform and very small size may be obtained, and recovered.

This invention has as another object the provision of atent ice apparatus useful for homogenizing emulsions, colloids, suspensions and the like.

The above and other objects are accomplished by the process of the present invention in which a mixture, such as a mixture of a solid and a liquid, or a mixture of mutually insoluble liquids is formed into a stream. This stream is impinged upon a coaxially rapidly moving stream of a gas whose direction of movement is changed shortly after the impingement, thereby effecting radial displacement of the liquid. The radially displaced liquid is broken up into very minute particles and is then collected on the surface of a surrounding collection vessel and drained downwardly to yield a stable homogenized mixture.

The apparatus of the present invention comprises a shell having a plurality of inlets, such as inlets for gas and liquid which pass through the shell into an aerosol generator disposed within the shell. By aerosol generator is meant a generator capable of generating particles having very small diameters, such as particles having a size range of the order of 60 microns in diameter, or smaller; preferably, below 10 microns. The shell is provided at its base with means for collecting the homogenized product, and removing the same; and with a vent, for removing the aerosolizing or propelling gas from the shell, which vent is provided with means for separating entrained particles from the vented gas from the shell.

For the purpose of illustrating the invention there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

Referring to the drawings wherein like referencecharacters refer to like parts:

Figure 1 is a schematic elevational view of an embodiment of apparatus suitable for practicing the method of the present invention.

Figure 2 is a longitudinal section through a nozzle useful for the practice of the present invention.

Referring to the drawings and initially to Figure 1, wherein an embodiment of apparatus suitable for the practice of the present invention is shown, the mixture to be homogenized is introduced into the apparatus through line 10. In the specific embodiment of the present invention here-illustrated, such mixture comprises a mixture to be used as a photoemulsion, namely 3 weight percent of gelatin and 10 weight percent of a silver halide, such as silver bromide, dispersed in distilled water.

It has been found by microscopic examination of superior photoemulsions, that such photoemulsions comprise minute particles of the silver bromide individually coated by the colloidal gelatin, which occupies the interstices between the individual grains of silver bromide.

While the process of the present invention is illustrated for the preparation of photoemulsions, it is, of course, to be understood that the process of the present invention is applicable to the homogenization of other suspensions, emulsions, and/or colloids, or the stabilization of such mixtures, as for example the stabilization of dairy products such as milkand cream containing milk fats, water and oil dispersions, paints, pigments, etc.

The slurry mixture is fed through line 10 to generator 12, which is disposed within a substantially closed vessel 14, spaced beneath the ceiling 16 thereof. The free edge of vessel 14 is received on an elastomeric or like base 18, such as synthetic rubber or like, whose outer edge has been rabbetted to provide a tight seal with the free edge. Base 18 is provided with a drain 20 having a valve 22 disposed therein through which the homogenized product 38 may be removed from vessel 14.

The mixture from line 10 enters the generator head designated 24, passing therein from line through channel 26 and thence through annular opening 28.

The propellent gas is introduced through line 30. The propellent gas should be an inert gas, where as in the subject example, interreaction between the mixture in line 10 and the propellent gas is undesirable. In the subject example, a satisfactory propellent gas to be introduced through line 30 is air at room temperature. The propellent gas namely air, is pressurized to above about 1.5 atmospheres, preferably above 1.7 atmospheres and moves from line 30 through line 32 and issues from generator head 24 through outlet 34 at supersonic or nearly supersonic velocity, drawing the slurry mixture from concentric. annular opening 28 into a sleeve-like envelope about it.

The rapidly moving gas stream carrying the envelope of liquid is impinged onto barrier 36. Impingement of the gas stream drastically distorts the gas stream from a unidirectional or axially moving stream into a substantially radial or disk-like pattern which radiates outwardly.

The sleeve-like liquid mixture surrounding the gas stream undergoes enormous blending forces upon distortion of the gas stream, resulting in an intimate degree of mixing of the mixture components, and subdividing of such mixture components into minute discrete particles of substantially uniform size suspended in the liquid (e.g. the silver bromide particles are broken into minute grains suspended in the gelatin and water colloidal system). Simultaneously the liquid mixture is dispersed onto the surrounding wall of vessel 14 as fine droplets having aerosol dimensions.

The generator 12, described in the present embodiment is the excellent aerosol generator disclosed in the co-pending application for United States Letters Patent Serial No. 441,039, filed July 2, 1954, entitled Apparatus and Method for Generating Aerosols, in the name of James B. Jones. While this form of generator is to be preferred, other forms of aerosol generators capable of generating an appreciable percentage of fine droplets within the aerosol size range and preferably within the size range of droplets having diameters of 10 microns or less may be substituted for generator 12.

The fine droplets of the homogenized mixture are collected on the wall of the vessel 14 in the form of a film. This film moves downwardly along the inner surface of the wall of vessel 14 and collects in a pool 38 at the base thereof.

The vessel 14 is provided with a vent 40 in ceiling 16 for removing the pressurized propellent gas. Vent 40 includes an angular conduit terminating in a single orifice discharge nozzle 42. A barrier 44 consisting of a metal plate having a face juxtaposed to discharge nozzle 42, is spaced from discharge nozzle 42, and deflects any droplets issuing therefrom into entrapment vessel 46 which is provided with a collector outlet shown diagrammatically at 48 through which collected homogenized material may be removed. The vented gas is removed from entrapment vessel 46 through vent opening 50, which may be provided with an additional deflector roof or barrier 52 for deflecting any entrained liquid carried thereby onto the outside of vessel 46. Such deflected liquid may be conveyed along the outer surface of collector outlet 48, and retained in the same receiver into which collector outlet 48 is discharging.

A separator vessel 46, or other separating or coagulating means such as a filter or an electrostatic precipitator, such as a Cottrell precipitator, must be utilized in the apparatus of the present invention because we have found that aerosol droplets, particularly those droplets having diameters of 10 microns or less will tend to become entrained with the rapidly moving propellent gas, even to passing around a corner with such gas, so that a significant portion of such droplets may be lost unless the auxiliary separating means, namely entrapment vessel 46 is provided.

In fact, in some cases, particularly where a high percentage of the generated droplets have very small diameters, it may be advisable to employ a plurality of entrapment vessels in series to avoid loss of material through entrainment with the propellent gas.

Under the aforesaid operating conditions homogenization of the sprayed material into a stable photoemulsion having a uniformly distributed dispersion of fine grains of silver bromide coated with gelatin may be achieved.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

We claim:

1. A method for homogenizing a mixture of a plurality of generally mutually insoluble materials including a liquid medium, which method comprises contacting a rapidly moving stream of gas with a coaxially enveloping stream of such mixture, impinging the rapidly moving stream of gas upon a barrier and deflecting it at an angle to its normal direction of movement, said deflection of the gas stream effecting an intimate degree of mixing between the components of the mixture and simultaneously breaking the mixture into aerosol droplets and subdividing the materials carried by the liquid medium into minute discrete particles uniformly distributed within the liquid medium, capturing said droplets upon a surface, and collecting said captured droplets to form a pool.

2. A method in accordance with claim 1 in which the mixture includes solid particles.

3. A method in accordance with claim 1 in which the mixture consists of a plurality of liquids which are substantially insoluble in each other.

4. A method in accordance with claim 1 in which the gas stream is moving at a supersonic velocity.

5. A method in accordance with claim 1 in which the mixture comprises an aqueous gelatinous medium and particles of a silver halide.

6. A method in accordance with claim 1 in which the mixture comprises an aqueous mixture of milk fats.

7. A method in accordance with claim 1 in which the mixture comprises a water and oil dispersion.

8. A method in accordance with claim 1 in which the mixture comprises a mixture of pigment materials and a vehicle therefor.

9. A method in accordance with claim 1 in which the surface of one of the materials of the mixture is thoroughly wetted by the liquid medium component.

10. A method for homogenizing a mixture of a plurality of generally mutually insoluble materials including a liquid medium, which method comprises contacting a rapidly moving stream of gas with a coaxially enveloping stream of such mixture, impinging the rapidly moving stream of gas upon a barrier and deflecting it at an angle to its normal direction of movement, said deflection of the gas stream effecting an intimate degree of mixing between the components of the mixture and simultaneously breaking the mixture into aerosol droplets and subdividing the materials carried by the liquid medium into minute discrete particles uniformly distributed within the liquid medium, capturing a portion of said droplets upon a surface, collecting said captured droplets to form a pool, entraining the remainder of the droplets in a gas stream, capturing entrained droplets from said gas stream upon a surface, and collecting said last-mentioned captured droplets.

11. A method for homogenizing a mixture of a plu- 'rality of generally mutually insoluble materials including a liquid medium, which method comprises contacting a rapidly moving stream of gas with a coaxially enveloping stream of such mixture, impinging the rapidly moving stream of gas upon a barrier and deflecting it at an angle to its normal direction of movement, said deflection of the gas stream efiecting an intimate degree of mixing between the components of the mixture and simultaneously breaking the mixture into aerosol droplets and subdividing the materials carried by the liquid medium into minute discrete particles uniformly distributed within the liquid medium, capturing a portion of said droplets from the gas stream upon a surface, collecting said captured portion of the droplets to form a pool, removing the gas stream and the remainder of the droplets from the region of the barrier, capturing entrained droplets from the remainder of the droplets carried by the removed gas stream upon a surface, and collecting said last-mentioned captured droplets in a pool.

12. A method in accordance with claim 11 in which the captured entrained droplets from the remainder of the droplets carried by the gas stream is formed into a pool which is discrete from the pool formed from the first-captured droplets.

13. In homogenizing apparatus for continuously producing a homogeneous mixture of a plurality of generally mutually insoluble materials comprising a liquid, the improvement which comprises a generally closed vessel, a propellant gas inlet extending through the wall of said vessel into the interior thereof, a separate liquid inlet extending through the wall of said vessel into the interior thereof, an aerosol generator disposed within said vessel and spaced from the walls of said vessel, said aerosol generator comprising a plurality of concentric conduits, the innermost conduit being in communication with the propellant gas inlet, and an outer conduit being in communication with the liquid inlet, a barrier juxtaposed to and spaced from the discharge orifices of said conduits, the discharge orrifice of said innermost conduit being at least as close to the juxtaposed face of said barrier as the discharge orifice of said outer conduit, means for collecting homogenized product at the base of said vessel, means in communication with the base of said vessel for withdrawing homogenized product from said vessel, and venting means for removing gas from said vessel, said venting means including means for separating and collecting entrained liquid aerosol droplets from said vented gas.

References Cited in the file of this patent UNITED STATES PATENTS 1,152,456 Vogelsang Sept. 7, 1915 1,839,193 Blanchard Jan. 5, 1932 1,878,052 Wilson et al. Sept. 20, 1932 2,069,455 Massa Feb. 2, 1937 2,284,023 Scripture May 26, 1942 2,323,877 Turbett July 6, 1943 2,597,422 Wood May 20, 1952 2,605,088 Dautrebande July 29, 1952 2,709,577 Pohndorf et a1. May 31, 1955

Claims (1)

1. A METHOD FOR HOMOGENIZING A MIXTURE OF A PLURALITY OF GENERALLY MUTUALLY INSOLUBLE MATERIAL INCLUDING A LIQUID MEDIUM, WHICH METHOD COMPRISES CONTACTING A RAPIDLY MOVING STREAM OF GAS WITH A COAXIALLY ENVELPING STREAM OF SUCH MIXTURE, IMPINGING THE RAPIDLY MOVING STREAM OF GAS UPON A BARRLIER AND DEFLECTING IT AT AN ANGLE TO ITS NORMAL DIRECTION OF MOVEMENT, SAID DEFLECTION OF THE GAS STREAM EFFECTING AN INTIMATE DEGREE OF MIXING BETWEEN THE COMPONENTS OF THE MIXTURE AND SIMULTANEOUSLY BREAKING THE MIXTURE INTO AEROSOL DROPLETS AND SUBDIVIDING THE MATERIAL CARRIED BY THE LIQUID MEDIUM INTO

Images