US2363937A - Method and apparatus for preparing dispersions - Google Patents

Description

Nov. 28, 1944. D. G. BRANDT ETAL' 2,363,937

' METHOD AND APPARATUS FOR PREPARING DISPERSIONS Filed Oct. 9,- 1941 INVENTOR JAM/A64 J 14 y/v/v DAV/0 6 a 07' BY a V ATTORNEY Patented Nov. 28, 1944 METHOD AND APPARATUS FoR PREPARING nrsraasrons David G. Brandt, Westfleld, and Samuel J. Wynn, River-ton, N. J., assignors to Cities Service Oil Company, New York, N. Y., a corporation of Pennsylvania Application October 9, 1941, Serial No.114334 8 Claims.

This invention relates to the preparation of dispersions, and is particularly concerned with improvements in method and apparatus for preparing finely dispersed emulsions and suspensions.

Colloid mills and other high speed rotary impeller type mixers and disintegrators, such as have been heretofore generally used commer cially for continuous formation of fine dispersions, operate on the principle of developing intense centrifugal forces and hydraulicshear effects within a zone of restricted cross-section through which the dispersion'constituents are forced. Because of the high stresses which are developed this type of apparatus is essentially complicated and expensive, and any process based on the indicated operating principle is limited as to the rate at which dispersions are formed, has a low power, utilization efllciency, and hasthe additional disadvantage of a substantial frictional heating effect on the dispersion constituents.

, Among the principal broad objects of the present invention are: to provide improved method and apparatus which is adapted for continuous formation of fine dispersions economically at a comparatively high rate; and to provide improved method and means forforming fine dis-, persions without the disadvantages above in- -tion energy is transmitted directly to the dispersion constituents; To insure intimate contact between the dispersion constituents and the diaphragm, and to increase the vibration tension of the diphragm, the invention in its preferred form further contemplates the use of high superatmospheric pressure (at least five pounds per square inch, and in some cases upwards of 200 pounds per square inch). on the dispersion constituents within the dispersion- I forming zone. In order to insure that the pres-' sure thus obtaining in the dispersion-forming zone shall have no vibration-damping effect and balance such pressure.

no distorting effect on the diaphragm, the invention further features a diaphragm mounting including a spring support for the diaphragm under a tension which is adjustable to counter- The combined use of superatmospheric pressure and a counterbalancing spring support at opposite sides of the diaphragm serves the important function of amplifying the natural vibration period of the diaphragm by increasing the stress tension thereof without at the same time damping the amplitude of the vibrations developed.

Thus an important feature of the invention resides in the use of the metal diaphragm both as a vibrationenergy transmitting element and as a vibration frequency amplifying element adapted for amplifying the vibration frequencies within the sonic and supersonic range. In order that the diaphragm may function as a frequently amplifier it is an important feature of the invention to mount the diaphragm in such a way that it is free -to develop independent vibration frequencies and so that it is physically independent from.the power hammer or other energy] source by means of which vibration energy is applied to the diaphragm for trans- I mission thereby to the dispersion constituents.

When the solid or liquid to be dispersed has a higher specific gravity than the liquid dispersion medium, the metail diaphragm is preferably mounted as the charge supporting base of the chamber in which the treatment is carried out. With this construction the natural inter face between the heavier material to be dispersed and the dispersing medium is located by gravity pull at a point adjacent the diaphragm base, where ,the greatest vibration effect is developed. It has been observed that the vibra-,

tion energy developed adjacent the diaphragm is sufficiently intense to insure disintegration of any solid material (including lead shot), into very fine particle size. When the liquid or solid to be dispersed is of lighter gravity than the liquid dispersing medium, the diaphragm is located as the top of the treating chamber where gravity classification will be operative to estab- .lish. the normal interface between the constitsign is the use of at least of two physically connected spaced diaphragms. one of which may form the liquid sealed base for the treatingchamber while the other diaphragm is connected by a central stem to the base of the diaphragm and has its peripheral edge free to develop independent vibration frequencies within the treating chamber.

With the above and other objects and features in view, the invention consists in the improved method of and apparatus for preparing fine dispersions which is hereinafter described, and particularly defined by the accompanying claims.

In the following description of the invention, reference will be had to the accompanying drawing, in which:

Fig. 1 illustrates diagrammatically, partly in longitudinal section, apparatus embodying the preferred features of the invention; and

Fig. 2 illustrates a modified form of apparatus having a more restricted field of application.

Referring to Fig. l, the preferred form of apparatus therein illustrated comprises a chamber l within which fine dispersions of a finely divided solid or liquid in a second liquid dispersion medium are produced as a result of subjecting the materials to the action of a vibrating metal diaphragm l2. In the particular apparatus which is illustrated in Fig. 1, chamber is shown as formed within an upright cylinder l4 having an integral dome i6. Diaphragm I2 is detachably mounted to form the charge supporting base of chamber Ill. The peripheral rim of the diaphragm is clamped between ground bearing surfaces of a flange joint having as elements an annular detachable flange ring l8 secured to the lower end of cylinder l4, as a second clamping flange ring 20. A spacing ring 22 may be inserted between clamping ring 22 and diaphragm l2. The two flange rings l8 and 29 are clamped together by bolts 24 which are provided with extensions serving as spacing bolts where by to adjustably space and align external vibration energy source and balancing spring elements with the center of diaphragm l2.

The liquid or finely divided solid substance which is -to be dispersed, and the liquid dispersing medium, may be introduced successively or simultaneously into chamber I0 through-an inlet pipe 26. An outlet pipe 28 having a regulating valve 29 is provided for removal of completed fine dispersion, and the mouth of pipe 28 can be adjusted vertically within chamber H! by mounting pipe 28 in a packing gland 30 in the dome l6. An important feature of the present invention is that of holding the' constituents of dispersion under controlled superatmospheric pressure within the dispersion-forming zone. Pressure may be developed within the chamber I 0 by the use of pumps 3|, 32 and connections whereby to supply a preformed coarse dispersion of the liquid-liquid or liquid and solid materials to the chamber. An alternative method for developing controlled pressure within thejchamber consists in supplying a gas such as nitrogen to the dome of the chamber under controlled superatmospheric pressure by means of a compressor 33 and a pipeconnection 34.

Energy for vibrating diaphragm l2 may be supplied by an electro-magnetic or solenoid-vibrator 36 which is illustrated diagrammatically as mounted in adjustably spaced and aligned relation to the center of diaphragm l2 by means of a collar 31 and extensions of bolts 24. Vibrator 36 is provided with a' magnetized reciprocating core 'rod hammer 38 which is. aligned with the center of diaphragm l2 and the vibrations of which are transmitted to the center of the diaphragm through 'the medium of a plunger 40. The upper end of plunger 40 is held in striking contact with a metal target 42 which is rigidly aflixed to the center of diaphragm l2. A coil spring 44 is mounted between a collar 45 engaging a shoulder 46 below the head of plunger 40 and a spring supnuts 48. The spring 44 thus is disposedtocoun- \terbalance any distorting and vibration damping effect of pressure obtaining in chamber Ill on the diaphragm, so that the center of the diaphragm is free to vibrate with full amplitude and frequency. Hammer 38, acting through plunger 49, imparts upward impacts to the center of diaphragm l2 at a frequency which may be 60 per second when the energizing current for the solenoid is a 60-cycle A. 0. current.

To further insure against undue distortion of diaphragm l2 outwardly as a result of superatmospheric pressure in chamber l0, and the vibration harmonics'of the diaphragm, the central aperture in flange ring 20 is threaded to demountably engage a cylindrical stop sleeve 49. A lock nut 50 is mounted on sleeve 49 below ring 20 and is used to lock the sleeve in predetermined suitable stop position below the diaphragm.

To increase the area of vibration transmitting surface in contact with the liquid dispersing medium in chamber ID, a second metal diaphragm disc 52 is mounted within chamber Ill in parallel spaced relation to diaphragm l2.

'Diaphragm 52 is circular and of smaller diameter than the internal diameter of the chamber. The center of diaphragm 52 is rigidly con,- nected to a stem extension 43 of target plug 42, while the peripheral rim of the diaphragm 52 is free to develop its own independent vibration frequencies within the dispersion-forming zone.

end of the discharge pipe 28 is adjustable vertically within the chamber l0. As previously indicated, the apparatus design illustrated is adapted for preparing dispersions of a material of high specific gravity in a liquid dispersion medium of lighter'gravity; and the apparatus may be operated so as to only partially fill the chamber II) with the dispersion constituents, while trapping gasunder pressure above the surface of the dispersion liquid. On the other hand it may be advantageous to completelyfill chamber [0 with the dispersion constituents and to elevate pipe 28 so that its inlet is adjacent the top of the dome. By this arrangement disintegration of the solid or liquid disperse material to fine particle size takes place at or adjacent the surfaces of the diaphragms, and vibration-gravity classification of the dispersion thus formed takes place in the upper portion of chamber l0, so that only the finest dispersion leaves the chamber through hastens the speed with which the coarser particles of disperse material are classified and returned by gravity settling to the bottom disintegration zone of the chamber.

In that modification of the apparatus which has been illustrated in Fig. 2, certainadvantageous features of the preferred design have been sacrified in order to' meet a particular problem which is sometimes encountered-when, for example, it is desirable to carry out the dispersionforming operation at a relatively high temperature and to simultaneously effect removal of liberated gases or vapors of volatile liquid from the zone of dispersion formation. The change in de sign of apparatus to meet problems of this type includes connection 35 whereby to maintain a partial vacuum within the chamber l; and other modifications made necessary by the use of such vacuumfor limiting the effects thereof on the vibration transmitting efllciency of the diaphragm l2. Thus, in this modification, the plug stem 43 which connects the two diaphragms l2 and 52 is provided with a long threaded extension rod 60 which is encircled by a collar 62 on which there is in turn supported the lowerend of a coil spring 64. The upper end of the spring 64 is held in place by the top .of a cylindrical sleeve 58. Sleeve 86 has external threads which engage matching threads in the bore of flange ring 20.

The position of collar 62 is adjustable by means of an adjusting nut 68 on rod 60, and the lower end of extension rod 60 is provided with a target cap which receives and transmits to the diaphragms the impacts of a hammer rod 38 which is vibrated at the frequency developed by an electro-magnetic vibrator 36. Thus it will be noted that in this construction the spring 64 is set up to resist and counterbalance the pull of vacuum in tank It tending to distort diaphragm l2.

tinuous throughput of dispersion constituents in sufficient volume to insure production of fine dispersion at a commercially practical rate. The rate at which fine disintegration and dispersion is effected is primarily a function of thedia The preferred apparatus is adapted for conphragm area and tension, and the diaphragm tension is in turn a function 'of the pressure which is maintained in the treating chamber I0 and of the counterbalancing pressure of spring 44. The diaphragm I2 is preferably constructed of a high tensile steel having suflicient strength to stand up under the operating conditions and having sufiicient hardness to possess a high natural period of vibration. Diaphragm 12 should also have a high diameter to thickness ratio (at least 100 to 1) in order to provide a large vibration surface in combination with sufficient flexibility as to be adopted for developing and transmitting vibrations of substantial amplitude. Another important contributing factor is that of having the As evidence of the intensity of vibration energy which is developed and transmitted to the dispersion constituents, substantial cavitation has been observed while preparing dispersions in apparatus of the general form described, but difiering therefrom by employing a single plane diaphragm disk I 2 having no central plug target 42. The cavitation thus developed was sufficiently intense to rapidly release metal from the central portion of the hard steel diaphragm face where the greatest cavitation is developed. It was because of the thus noted erosion effect of cavitation 0n the diaphragm surface that the bored stem 54 and additional diaphragm 52 were added to more widely distribute the area of high vibration intensity, and to provide passages around the second diaphragm and through the bores of the stem whereby to utilize'the forces evidenced by cavitation to promote circulation of the dispersion constituents in the zone between the parallel spaced diaphragms;

The dispersion constituents are preferably delivered to the dispersion-forming zone in the form of a preformed coarse dispersion which is preferably proportioned with a large excess of dispersion liquid. The solid or liquid which is to form the disperse phase is naturally drawn by gravity pull to the immediate vicinity of the vibrating diaphragm surface where it is subjected to the intense vibr'ation'turbulence which (level-- ops throughout the liquid, and particularly in the zone adjacent the diaphragm surfaces. The metal diaphragms are under suflicient tension so that'the sharp high frequency hammer blows imparted thereto by the hammers 38 and 4t develop within the diaphnagms supplemental vibrations having. frequencies within the sonic and supersonic range. The supplemental vibrations thus developed in the diaphragms are entirely out of phase with the vibrations imparted thereto by the hammer, so that interfering vibration waves are transmitted through the liquid in the treating zone and develop therein vibration waves of i also been applied with success to the production of suspensions of graphite or sulphur in lubrivibration energy source] i. e., the hammenby which vibrationimpacts are imparted to the diaphragm, physically independent of the diaphragmQso that the diaphragm is free to vibrate and to develop its natural vibration frequencies independently of the hammer. By providing a second diaphragm physically attached to'the main diaphragm by a central stem and having an unsupported rim free to develop its own independent vibration frequencies within the treating zone, the area of vibrating surface is multiplied, the zone of maximum vibration is also enlarged, and the range of vibration periods is multiplied.

cating oil. The present process issalso adapted for effecting dispersions of lead suboxide or other chemical treating agents in gasoline. Also the process is suitable for securing uniform dispersions of anti-knock agents such as triphenylguanidine in gasoline. The vibrations developed are of suchfrequeney and amplitude as to thoroughly break down flocculent adherence of solid 7 particles and promote disintegration and dispersion of the solid throughout the liquid dispersing medium in apparently ultimate fine particle size. Another field of application for the invention is in. the field of cosmetics, such as, for example, in the preparation of finely dispersed stable suspensions or emulsions of greatly improved stability as compared to present day hand lotions and the like.

-The invention having been thus described. what is claimed as new is:

1. An apparatus for preparing dispersions in liquids, comprising a chamber in which the dispersions are prepared, said chamber having as one wall thereof a metal diaphragm of relatively large area having its rim anchored and its center free to vibrate, means for supplyingliquid to .be treated to the chamber in contact with said diaphragm, means outside said chamber for vibrating said diaphragm including a reciprocating hammer movable independent or the diaphragm and mounted in a position to impart a succession of sharp impacts at high frequency to the central portion of said diaphragm, and means for transmitting the hammer impacts to the central portion of the diaphragm. 2. An apparatus for preparing dispersions in liquids, comprising a chamber in which the dispersions are prepared, said chamber having as no wall thereof a diaphragm of relatively large area, means for vibratingsaid diaphragm, means for fsupplying liquid to be treated to the chainber'in .contact with said diaphragm, a conduit for removing formed dispersion from the chamber, and means for adjusting the -spacing of the.

inlet of said conduit from the diaphragm a distancesumcientto permit vibration-gravity clas siflcation of the formed dispersion prior to its removal from the chamber.

3. An apparatus for preparing dispersions in liquids, comprising a chamber in which the dispersions are prepared, said chamber having as one wall thereof a diaphragm of relatively large area,. means for supplying liquid to be treated to the chamber, a second diaphragm .mounted within. the-chamber in closely spaced parallel relation with respect to the first diaphragm and having its center attached by a stem to the center of thefirst diaphragm for vibration therewith, an aperture in'said stem whereby liquid may circulate between the zones on opposite sides of said diaphragm, and means for vibrating said diaphragms.

4. An apparatus for preparing dispersions in liquids, comprising a chamber in which the dispersions are prepared having as one wall thereof a metal diaphragm of relatively'large area, means for supplying liquid to be treated to the chamber in contact with said diaphragm, a second thin metal diaphragm secured to the center of the first diaphragm in spaced parallel relation thereto within the chamber for free vibrational movement therewith, a communication channel from the space between the diaphragms to the space on the opposite side of the second diaphragm, and means tor vibrating said diaphragms.

5. An apparatus for preparing dispersions in liquids, comprising a chamber in which the dispersions are prepared, said chamber having as one wall thereof a diaphragm 01' relatively large area, means for vibrating said diaphragm, means for supplying liquid to be treated to the chamber in contact with the diaphragm, and a counterbalancing spring mounted on the diaphragm outside the chamber and arranged to counterbalance the diaphragm against the pressure maintained in the chamber, thereby preventing damping of the diaphragm.

6. An apparatus for preparing dispersions in liquids, comprising a chamber in which the dispersions are prepared, said chamber having as one wall thereof a metal diaphragm of relatively large area having its rim anchored and its center free to vibrate, a second metal diaphragm secured to the central portion of the first diaphragm in spaced parallel relation thereto within the chamber having its rim spaced slightly from the chamber wall and free to vibrate, means for supplying liquid, to be treated to the chamber in contact with said diaphragms, and means for vibrating said diaphragms.

7. Apparatus for preparing a fine dispersion of a fluid or solid with a liquid, comprising a transmitter of vibration in the form ,01- a metal diaphragm of relatively large area having its rim anchored and its center free to vibrate, a dispersion-forming chamber having the diaphragm as one wall thereof, means for maintaining a suitably proportioned mixture of the fluid or solid and liquid under superatmospheric pressure in contact with the chamber side of the dia-- phragm, a metal target attached to the center of the diaphragm and a source of vibration energy mounted at the other side of the diaphragm having a hammer in position to impart successive sharp impact at high frequency to the target to develop vibration of the diaphragm.

' 8. The dispersion apparatus defined in claim 7-in. which a second diaphragm is supported by the target and spaced from the metal diaphragm and a circulation channel is formed in the target to permit circulation of fluid from above the target into the space-between thediaphragms.

DAVID G. BRANDT. SAMUEL J. WYNN.

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