US3361680A

US3361680A - Use of ultrasonic vibrations to disperse a liquid in another liquid

Info

Publication number: US3361680A
Application number: US280079A
Authority: US
Inventors: Byron B Bohrer
Original assignee: Sun Oil Co
Current assignee: Sunoco Inc
Priority date: 1963-05-13
Filing date: 1963-05-13
Publication date: 1968-01-02
Anticipated expiration: 1985-01-02

Description

United States Patent 3,361,680 USE OF ULTRASONIC VIBRATIONS T0 DISPERSE A LIQUID IN ANOTHER LIQUID Byron B. Bohrer, Rosemont, Pa., assignor to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey No Drawing. Filed May 13, 1963, Ser. No. 280,079 16 Claims. (Cl. 252-314) This invention relates to processes for dispersing one liquid in another by the use of ultrasonic vibrations. The invention provides a method for utilizing such ultrasonic vibrations more efiiciently than has been possible heretofore.

It is well known to disperse one liquid in another by the use of either ultrasonic vibrations or motor driven agitators. An advantage of using ultrasonic vibrations is that this technique generally results in smaller size dispersed phase particles, i.e., a more stable dispersion. For example, a dispersion of hexadecane in water free of emulsifying agents and stable for, say days can be prepared by means of ultrasonic vibrations. If a motor driven agitator were used, however, an emulsifying agent would generally have to be employed to obtain the same stability. Another advantage of using ultrasonic vibrations is that the dispersion is usually effected in a shorter time than when a motor driven agitator is used. A disadvantage of the use of ultrasonic vibrations to effect dispersion is that the power consumption is generally higher than that which results when a motor driven agitator is employed.

The present invention provides a method for reducing the power requirements in a process for dispersing one liquid in another by the use of ultrasonic vibrations. Such reduction is accomplished, according to the invention, by dissolving in the liquid to be dispersed a small amount of an additional liquid, the vapor pressure of said additional liquid being higher than the vapor pressure of the liquid to be dispersed and being within 360 mm. Hg of the pressure at which the dispersion is to be carried out.

Before describing the invention in detail several terms used in such description will be defined. As used herein the term dispersion applies not only to stable dispersions of one liquid in another, i.e., to emulsions, but also to unstable dispersions of one liquid in another. In an unstable dispersion the dispersed liquid will settle out and result mtwo distinct liquid layers within a few minutes after the agitation or other dispersing mechanism is shut off, While in a stable dispersion, i.e., in an emulsion, such separation generally will not occur for days or weeks. In

some applications, such as solvent extraction, it is important to intimately disperse one liquid in another and then rapidly separate the liquids. In other words, it is important to form an unstable dispersion.

The liquid to be dispersed, i.e., the dispersed or discon- :tinuous phase of the resulting dispersion, is referred to herein as liquid A. The liquid in which liquid A is to be dispersed, i.e., the continuous phase of the resulting dispersion, is referred to herein as liquid B. For example, in a dispersion of oil in water, A is oil and B is water.

The temperature and pressure at which the dispersion takes place are referred to herein as the system temperature and system pressure respectively. Thus if oil is dispersed in water in a tank which is open to the atmosphere and maintained at 30 C., the system temperature is 30 C. and the system pressure is atmospheric.

With reference to two given liquids, the term immiscible means that mixtures of equal volumes of the two liquids will contain two distinct layers. Similarly the term miscible means that a mixture of equal volumes of the two liquids is a single homogeneous phase.

As described, the present invention provides a means for reducing power requirements in a process for ultrasonically dispersing liquid A in liquid B. Liquids A and B can be any two liquids so long as one of them (A) can be dispersed in the other (B). Liquids A and B will, of course, be immiscible at the dispersion conditions, i.e., at the system temperature, for this is inherent in the concept of dispersion. Preferably the solubility of liquid A in liquid B is less than 0.1% by weight at the system temperature. Typical dispersion processes to which the invention is applicable include processes for dispersing an organic liquid in water (e.g., oil in water), an organic liquid in an organic liquid (e.g., oil in methanol), an inorganic liquid in an organic liquid (e.g., water in oil), an organometallic compound in Water (e.g., dirnethylsilicone in water), etc.

Since certain types of dispersions are in frequent use the invention is preferably applicable to processes for creating such dispersions. One such dispersion is a dispersion or an organic liquid in water. For example, oil in water dispersions are used as spray oils to protect fruit, etc. against insects. Similarly chemical reactions involving hydrocarbons and effected by biological techniques often employ a dispersion of the hydrocarbon in water. Thus fermentation of hexadecane is effected by placing certain bacteria in a dispersion of hexadecane in water. Another common dispersion is a dispersion of water in oil. This type finds frequent use in, for example, hydraulic fluids.

The relative amounts of liquids A and B is not critical and will vary depending upon the nature of the specific liquids employed, the ultimate use to which the dispersion is to be put, etc. Normally the amount of A will be 0.5 to 50.0% of the total Weight of A and B. All percentages in this specification are by weight.

As previously described the power required to ultrasonically disperse A and B is reduced by adding a small amount of an additional liquid, hereinafter referred to as liquid C, to liquid A prior to said dispersing. Liquid C has certain characteristics as follows: it should be mis cible with A at the system temperature. In addition, it should be immiscible with B at the system temperature. Preferably the solubility of liquid C in liquid B is less than 0.1%. Liquid C should also be inert to liquids A and B, i.e., it should not react with either during the dispersion process. In addition to the above characteristics, liquid C also has certain vapor pressure characteristics. It should have a vapor pressure at the system temperature higher than the vapor pressure of the liquid to be dispersed, i.e., higher than liquid A. Furthermore, the vapor pressure of C at the system temperature should be within 360 mm. Hg of the system pressure. For example, when the dispersion is to be carried out at 1 atmosphere pressure (760 mm. Hg) the vapor pressure of liquid C at the system temperature should be at least 400 mm. Hg. If the dispersion is to be efiectcd at 1 /2 atmospheres (1140 mm. Hg) the vapor pressure of liquid C should be at least 780 mm. Hg at the system temperature.

While liquid C should be a liquid at the temperature and pressure at which the dispersion of A in B is carried out, liquid C does not necessarily have to be a liquid at room temperature and pressure. For example, in dispersing oil in water butane can be employed as liquid C so long as the system pressure is sufficient to maintain the butane in the liquid phase. Once the dispersion is effected the pressure can then be removed and the butane will, of course, vaporize and leave the system. Similarly a particular liquid may not have sufiicient vapor pressure at room temperature to be suitable as liquid C whereas if the temperature at which the dispersion is effected is raised somewhat it may be suitable as liquid C. For example, in a process for dispersing oil in Water at 22 C. and 760 mm. Hg, benzene is unsuitable as liquid C because its vapor pressure at this temperature is only about 100 mm. Hg. However, if the same process is carried out at about 5560 C. benzene becomes a suitable liquid C because at this higher temperature its vapor pressure is within the aforementioned vapor pressure requirements.

Since the vapor pressures and solubilities of various liquids are readily available in the literature, the criteria for selecting liquid C are readily available to one skilled in the art. Where mineral oil is being dispersed in water, a preferred embodiment of the invention, compounds which can often be utilized as liquid C include butane, pentane, carbon tetrachloride, diisopropyl, butylethylene, etc. Preferably liquid C is a hydrocarbon. Where water is being dispersed in oil, compounds especially suitable as liquid C include low molecular weight (1-8 carbon atoms) alcohols, ethers, and ketones such as methanol, acetone, and ether. Where hydrocarbons such as decane, hexadecane, etc. are being dispersed in water, compounds generally suitable as liquid C include pentane, butane, diisopropyl, etc. Preferably liquid C is a hydrocarbon.

The amount of liquid C employed should be in the range of 0.01 to 2.0% by weight of liquid A. Within this range the amount will vary depending upon such factors as the amount of liquid A being dispersed and the vapor pressure of liquid C. As the amount of liquid A increases, the amount of liquid C is preferably increased. Likewise, as the vapor pressure of liquid C decreases the amount of liquid C is preferably increased. In most cases the amount of liquid C will be, and preferably is, 0.1 to 1.0% by weight of liquid A.

Since most dispersion processes are carried out at approximately atmospheric pressure, the invention is preferably applicable to such a process.

The magnitude of the reduction of power required to ultrasonically disperse A in B which is effected by adding C to A depends primarily upon the differences in vapor pressure of liquids A and C. Where this difference is large the power reduction accomplished by the invention is relatively large. As this difference decreases the power reduction decreases. In view of this the invention is particularly applicable to processes for dispersing A in B wherein A has a low vapor pressure, Le, a vapor pressure less than 20% of the system pressure. An example of such a liquid A is oil since most oils have vapor pressures of almost zero at room temperature. As already described, the invention is preferably applicable to, inter alia, processes for dispersing oil in water.

Although the invention has been described with reference to effecting dispersions solely by the use of ultrasonics, the invention is also applicable to dispersion processes utilizing both mechanical agitation and ultrasonics. Thus it is desirable in some cases to form a very gross dispersion with a motor driven agitator after which this gross dispersion is subjected to ultrasonic vibrations to complete the dispersion. The reason for this is that it is sometimes more economical from a power standpoint to form the initial dispersion mechanically even though ultrasonics must subsequently be used to achieve the desired stability, dispersed particle size, etc. The present invention is applicable to such a combination process. In such a case liquid C should usually be added to liquid A prior to the mechanical dispersion step.

The dispersion processes to which the invention is applicable, namely, processes for dispersing A in B ultrasonically, are well known in the art. Such processes are carried out in conventional equipment utilizing conventional means for generating ultrasonic vibrations. The most common such means is the piezoelectric transducer although other means such as the magnetostrictive transducer are also used. The frequency of the utrasonic waves generally employed in the dispersion of one liquid in another is 10,000 to 20,000,000 cycles per second. Although the ultrasonic range technically begins at about 20,000

c.p.s., frequencies of l0,00020,000 c.p.s. are often used in liquid dispersion processes, hence this range is included in the term ultrasonic as used herein.

The dispersion processes to which the invention is applicable can also utilize an emulsifying agent in order to increase the emulsion stability. Conventional emulsifiers such as triethanolarnine stearate can be used although the particular emulsifier employed will depend upon the particular liquids A and B.

The advantage gained by the use of the invention in a process for dispersing one liquid in another is illustrated by the following.

Seventy-five parts water and twenty-five parts of a mineral oil having a viscosity of S.U.S. at 100 F. and an A.P.I gravity of 23 is charged at 30 C to a mixing vessel open to the atmosphere and equipped with a piezoelectric tranducer. The oil-water mixture is subjected to untrasonic vibrations having a frequency of 30,000 c.p.s. for 3 minutes. The power input to the transducer is watts. After 3 minutes the oil is thoroughly dispersed in the water. The dispersion is stable for 36 hours and is useful as a cutting oil.

Next the above procedure is repeated except that 0.125 part of n-pentane is mixed with the oil before charging the oil to the mixing vessel. After subjecting the mixture to utrasonic vibrations (30,000 c.p.s. and 150 watts input) for 2 minutes a dispersion stable for 36 hours is obtained. Thus the former requirements are reduced by 33%.

The invention claimed is:

1. In a process for dispersing a liquid, A, in another liquid, B, immiscible therewith by subjecting a liquid mixture of A and B to ultrosonie vibrations, the temperature and pressure at which said subjecting takes place being the system temperature and system pressure respectively, the improvement which comprises adding to liquid A, prior to said subjecting, 0.012.0%, by weight of A, of an inert liquid, C, which is miscible with A and immiscible with B, the vapor pressure of C being higher than the vapor pressure of A and being within 360 mm. Hg of the system pressure, all said vapor pressures and all said miscible and immiscible criteria being determined at said system temperature.

2. Method according to claim 1 wherein the solubility of both (1) A in B, and (2) C in B is less than 0.1%.

3. Method according to claim 1 wherein the vapor pressure of A is less than 20% of the system pressure.

4. Method according to claim 1 wherein the amount of C is 0.1-1.0% by weight of A.

5. In a process for dispersing an organic liquid in water at approximately atmospheric pressure, said organic liquid being immiscible with water, by subjecting a liquid mixture of said organic liquid and water to ultrasonic vibrations, the temperature and pressure at which said subjecting takes place being the system temperature and system pressure respectively, the improvement which comprises adding to said organic liquid, prior to said subjecting, 0.01-2.0%, by weight of said organic liquid, of an inert liquid C which is miscible with said organic liquid and immiscible with Water, the vapor pressure of C being higher than the vapor pressure of said organic liquid and being within 360 mm. Hg of the system pressure, all said vapor pressures and all said miscible and immiscible criteria being determined at said system temperature.

6. Method according to claim 5 wherein said organic liquid is a hydrocarbon.

7. Method according to claim 5 wherein said organic liquid is oil.

8. Method according to claim 5 wherein liquid C is a hydrocarbon.

9. Method according to claim 5 wherein the solubility of both 1) said organic liquid in water, and (2) C in water is less than 0.1%

10. Method according to claim 5 wherein the vapor pressure of said organic liquid is less than 20% of the system pressure.

11. Method according to claim wherein the amount of C is 0. 11.0% by weight of said organic liquid.

12. In a process for dispersing water in oil at approximately atmospheric pressure by subjecting a liquid mixture of said oil and said water to ultrasonic vibrations, the temperature and pressure at which said subjecting takes place being the system temperature and system pressure respectively, the improvement which comprises adding to said water, prior to said subjecting 0.01-2.0 by weight of said water, of an inert liquid C which is miscible with water and immiscible with said oil, the vapor pressure of C being higher than the vapor pressure of said water, and being within 360 mm. Hg of the system pressure, all said vapor pressures and all said miscible and immiscible criteria being determined at said system temperature.

13. Method according to claim 12 wherein liquid C is selected from the group consisting of low molecular Weight alcohols, ethers, and ketones.

References Cited UNITED STATES PATENTS 1,734,975 11/1929 Loomis et al 252314 1,992,938 3/1935 Chambers et a1 252314 2,158,374 5/1939 Merrill 252-312 2,304,125 12/1942 Shutt et a1 252-309 2,407,462 9/ 1946 Whiteley 23 14 LEON D. ROSDOL, Primary Examiner. JULIUS GREENWALD, Examiner.

R. D. LOVERING, Assistant Examiner.

Claims

1. IN A PROCESS FOR DISPERSING A LIQUID, A, IN ANOTHER LIQUID, B, IMMISCIBLE THEREWITH BY SUBJECTING A LIQUID MIXTURE OF A AND B TO ULTROSONIC VIBRATIONS, THE TEMPERATURE AND PRESSURE AT WHICH SAID SUBJECTING TAKES PLACE BEING THE SYSTEM TEMPERATURE AND SYSTEM PRESSURE RESPECTIVELY, THE IMPROVEMENT WHICH COMPRISES ADDING TO LIQUID A, PRIOR TO SAID SUBJECTING, 0.01-2.0%, BY WEIGHT OF A, OF AN INERT LIQUID, C, WHICH IS MISCIBLE WITH A AND IMMISCIBLE WITH B, THE VAPOR PRESSURE OF C BEING HIGHER THAN THE VAPOR PRESSURE OF A AND BEING WITHIN 360 MM. HG OF THE SYSTEM PRESSURE, ALL SAID VAPOR PRESSURES AND ALL SAID MISCIBLE AND IMMISCIBLE CRITERIA BEING DETERMINED AT SAID SYSTEM TEMPERATURE.