US2954678A

US2954678A - Method of dispersing materials

Info

Publication number: US2954678A
Application number: US672786A
Authority: US
Inventors: Thomas J Mahon; Albert L Edelstein; Glickstein Joseph
Original assignee: ASS FOR PHYSIOLOGIC RES Inc
Current assignee: ASS FOR PHYSIOLOGIC RES Inc; ASSOCIATION FOR PHYSIOLOGIC RESEARCH Inc
Priority date: 1957-07-18
Filing date: 1957-07-18
Publication date: 1960-10-04
Anticipated expiration: 1977-10-04

Description

T. J. MAHON EFAL METHOD OF DISPERSING MATERIALS Oct. 4, 1960 Filed July 18, 1957 BY Why ATTORNEYS.

FIG. 7

FIG. 5.

United tes Patent METHOD OF DISPERSING MATERIALS Thomas .I. Mahon, Englewood, N.J., and Albert L. Edelstein and Joseph Glickstein, New York, N .Y., assignors, by mesne assignments, to Association for Physiologic gesiarch, Inc, New York, N.Y., a corporation of New Filed July 18, 1957, Ser. No. 672,786

4 Claims. (Cl. 62-50) This invention relates to a novel and improved method for maintaining thermal equilibrium of liquid propellants and more particularly to a novel and improved method, in which liquid and/or solid materials are dispersed, e.g. sprayed, atomized, or nebulized by the action of an evaporating and/or gasifying propellant. The invention also relates to means for stabilizing or lengthening the propelling action of propellants used in dispersing, spraying, atomizing and nebulizing, or as a source of energy for operating devices and the like.

In certain devices known from the art, materials are sprayed, atomized, nebulized, or converted into aerosols, by the propelling action of gas evolved from a charge of 'a propelling medium consisting for example of a liquefied gas which has a considerable vapor pressure at ordinary room temperature, such as a mixture of fluorinated hydrocarbons, or equivalent materials, such as certain petroleum hydrocarbons, e.g. propane, butane or their mixtures. The duration of gas evolution from such liquefied gas (aerosol propellant) is limited by the cooling resulting from the evolution of gas, whereby the liquid may be cooled to the point of inadequate vapor pressure. For

example, if the propellant is dichlorodifiuoromethane (known in commerce also under the trademark Freon-12), a quantity of heat of the order of 35 cal. must be supplied per gram to the propellant liquid if the temperature is to be maintained in the range at which the propellant has the vapor pressure necessary for spraying, atomizing or the like.

It has now been found that this heat can be supplied by the presence in the liquefied propellant of a substance which is liquid for example at ordinary room temperature, e.g. 1525 C., and becomes solid at lower temperatures, whereby the heat necessary for maintaining the temperature of the propellant at the desired level is supplied by the crystallization heat or solidification heat of such substance.

It is one object of the present invention to secure a substantially constant level of the propelling action for an extended period of time, by maintaining the temperature of the liquid propellant at a predetermined level by the crystallization heat or solidification heat of a liquid substance present in the liquid propellant.

Another object of this invention consists in prolonging the propelling action of the liquid propellant by replacing the heat consumed by the evaporation and/or gasification of the liquid propellant and thereby providing for a substantially uniform evolution of gas from the liquid propellant which is maintained at a substantially constant temperature.

A further object of the invention is to provide a dispersing method, in which propellant media of different pressure characteristics can be used during extended periods of time. Still another object of the invention is to avoid cooling of the propellant fluid below a predetermined temperature during the evolution of gas from the liquid propellant.

2,954,678 Patented Oct. 4, 1960' ice It is likewise an object of the present invention to maintain the temperature of the propellant liquid at a predetermined level by a method which is applicable to vari-' ous propellants, devices and systems of dispersing, atomizing, nebulizing and the like.

A further object of the invention consists in providing an improved nebulizing or atomizing method by which the material to be dispersed is dispensed with the desired uniform particle size, e.g. in the form of aerosol particles.

Other objects and the advantages of the invention will be apparent from the appended claims and drawings and the following specification which describes by way of example and without limitation some embodiments of and best modes of carrying out the invention.

In carrying out the present invention, the substance which is used for supplying its crystallization heat or solidification heat to the liquid propellant can be placed in the latter in the form of relatively small individual units, e.g. sealed capsules, packages or the like. Such units, which contain for example 2-3 grams of the molten substance, present a large surface so that rapid heat exchange between said units and the propellant medium and satisfactory maintenance of the desired temperature during the evolution of gas are attained. A large surface area for the supply of heat to the propellant liquid is important, because undesired cooling of the liquid propellant can occur if heat is supplied too slowly, as it could happen if the heat exchange between the substance to be solidified and the propellant liquid, takes place on a too small surface.

If the specific gravity of the molten substance is substantially lower than that of the propellant liquid, the units or packages may be weighted, if desired, in order to keep them well submerged in the propellant liquid. This can be done for example by using a packaging material of sufiiciently high specific density or by including ballast in the molten substance sealed in the packages or units. As examples of such Weighting agents, pulverized pigments, e.g. iron oxide, bronze, red lead oxide, chalk and metal powders and/or shots, wires, slugs or other particles, are mentioned.

As a material adapted to supply solidification heat according to the present invention to the liquid propellant to be evaporated and/or gasified, any substance can be used which is liquid at ordinary room temperature, becomes crystalline or solid at a somewhat lower temperature, has no toxic, corrosive or other undesired elfect and has a substantial crystallization or solidification heat.

Very satisfactory results have been obtained in the use of fatty substances, as a preferred exampleof which methyl myristate is mentioned. This substance, which is the methyl ester of myristic acid, has a melting point of 19 C., a high heat of fusionabout 45 cal. per gram-, is inexpensive, nontoxic and readily available. The methyl myristate can be used in units containing 2-3 grams thereof packaged and sealed, e.g. in suitable metallic materials, or capsules, tubes and the like of gelatine or plastic.

Other examples of materials for supplying solidification heat according to the present invention are: methyl laurate, methyl palmitate, caprylic acid, oleic acid, ricinoleic acid, coconut oil, tricaprylin, trilaurin, 1,2,4-trichlorobenzene.

Mixtures of fats having the above mentioned preferred melting range (i.e. a melting point at ordinary room temperature) and a substantial solidification heat can be also used with advantage. As examples, mixtures of methyl launate and tricaprylin, and mixtures of caprylic acid and oleic acid, containing in each case e.g. equal amounts of the ingredients, are mentioned. Mixtures of methyl esters of several fatty acids can also be used. Certain parafiin hydrocarbons can be likewise used with advantage in carrying out the present inveniton. For example n-hexadecane, which has a heat of fusion of 55 cal./ g. and a melting point of 18" C. can be satisfactorily used. Molten crystallizable inorganic salt hydrates can also be used for supplying heat according to the present invention.

The appeided drawings illustrate by way of example and without limitation some embodiments and best modes of carrying out and using the invention.

In the drawings:

' Figs. 1-3 diagrammatically illustrate some of the various forms of scaled units or packages containing the heat supplying and stabilizing substance used according to the present invention;

Fig. 4 diagrammatically illustrates a sealed unit which is similar to those shown in Figs. l-3, but has an elongated tubular shape;

Fig. illustrates a perforated can or container in which a plurality of capsules are enclosed;

Fig. 6 diagrammatically illustrates a modification of the perforated container shown in Fig. 5, in which the sealed units are placed in a Wire gauze container;

Fig. 7 illustrates a device which can be used for nebulizing a liquid by means of a self-pressurizing liquid propellant, the temperature of which is maintained at a substantially constant level by the solidification heat of molten substances placed in said propellant.

Referring now to the drawings in detail, in Fig. 1 reference numeral 1' denotes a cylindrical package or unit containing about 2-3 grams of a molten substance 2' and also .containing weighting material denoted by reference symbol 21. Figs. 2 and 3 diagrammatically illustrate similar packages of rectangular and spherical shape, re spectively, the container and propellant liquid being denoted 1", 2" and 1", 2 in Figs. 2 and 3, respectively. The sealed unit shown in Fig. 4 is substantially similar to those shown in Figs. 1-3, but has an elongated cylindrical shape. In Fig. 4 the heat-supplying liquid is denoted 32 and the sealed wrapping 31. The sealed wrappings shown in Figs. 1-4 may consist e.g. of foil or sheet of metal, paper, thin plastic, or gelatin.

In Fig. 5, reference numeral 3 denotes a can which is provided with perforations 4, and in which units or

packages

2, 2 containing the heat-supplying molten substance are placed, said perforated can being adapted to be immersed in ,the propellant fluid for supplying heat to it during dispersing, atomizing or the like. A modification of the assembly shown in Fig. 5 is shown in Fig. 6 in which a container 33, consisting of wire gauze is shown instead of the perforated can.

In the device diagrammatically illustrated in Fig. 7, 41 denotes a container for a self-pressurizing liquid propellant 42, in which a plurality of perforated cans 3 of the type shown in Fig. 5 is immersed, each of said perforated cans containing a plurality of sealed units of the type shown in Figs. 1-3. Each of these units contain, for example, 2-3 grams of liquid methyl myristate. The propellant used may be, for example, the above mentioned mixture Freon consisting of fluorinated hydrocarbons. Container 41 is provided on its top with discharge means which are generally denoted 43 and include an adjustable valve 44 of conventional type, for regulating the discharge of propellant gas. Upon opening valve 44, propellant gas evolved in container 41 will escape through conduit 45 and will cause the discharge of the liquid 45 to be atomized or nebulized from container 47 through tubes 48 and 45 and nozzle 49.

In using a device of the type shown in Fig. 7 as a nebulizer in the treatment of pulmonary disorders of one patient, it has been established that the nebulizer operation requires e.g. 10-13 grams of the propellant Freon per minute. At the rate of 13 grams per minute, the heat loss is 450 calo-ries per minute, so that for each 10 minutes of operation at this rate (13 grams propellant per minute) the stabilizer, i.e. the liquid methyl myristate about 110 minutes.

should supply a minimum of4500 calories. This amount of heat is supplied by about grams of methyl myristate. Twenty minutes of operation require about /2 lb. of methyl myristate and about 4 lb. of the Freon propellant. The container 41 can be repeatedly used until the propellant is exhausted, provided it is allowed to warm up between periods of operation with evolution of the propellant gas. The time necessary for sufficiently warming up the propellant container 41 and its contents can be easily determined by some preliminary tests in the use of a specific apparatus. It depends on the specific room temperature, on the amount of the evolved propellant gas and the amount of liquid propellant remaining in the container after operation.

In carrying out the present invention, the amount of aerosol or other dispersed material produced per unit of time and propellant corresponds to the amount produced according to known methods and in known devices under otherwise equal conditions, but the duration of continuous operation is considerably increased. For example, it has been found that in a conventional nebulizing device which could be continuously' operated with Freon 12 for about 4 minutes, continuous operation with heat supply by methyl myristate could becarried out for In other tests, a popular nebulizer which includes a first container for the propellant and a second container which contains the substance to be nebulized by the propellant, and contained in the first container 2 pounds of Freon 12, in which 160 capsules, each containing 3 grams of methyl myristate, were immersed, could be continuously operated for minutes with an output of liquid material of 2% times the minimum requirement. The output of such nebulizer can be varied by the patient with a simple adjustment of the device. Under equal conditions, but in the absence of methyl myristate in the propellant, the device could be continuously operated for about 4 minutes only at suitable pressure.

It will be understood from the above that the present invention is not limited to the steps, conditions, systems, devices and other details specifically described above and illustrated in the drawings and can be carried O t with various modifications. For example, the invention can be applied to all dispersing or the like systems in which in the course of the dispersing step evaporation and/ or gasification of a liquid medium takes place, i.e. in systems in which spraying or the like is brought about by a selfpressurized liquefied gas, e.g. Freon, placed in a first container, while the liquid to be dispersed is placed in a second container, as well as in single-container systems in which a gasifiable liquid, e.g. trichlor monofiuor methane or its mixture with methylene chloride, contains the solid or liquid substance to be dispersed in solution or suspension. Furthermore, the invention can be also applied to spraying devices provided with two containers for the propellant liquid and an additional container for the substance to be dispersed, in order to facilitate continuous maintenance of a sufficient gas pressure during an extended period of time. The dimensions of the sealed units containing the heat-supplying stabilizer liquid, and the dimensions of the above described perforated cans and similar containers for said sealed units, can, of course, vary. Sealed units each containing fractions of grams to 5 grams of the molten liquid and cylindrical containers for such units, having a diameter of about and a length of about 3" have been found to give very satisfactory results. Such containers can be fabricated from perforated sheet metal, from pipes or from wire gauze and the containers can be weighted e.g. by washers, if necessary. The sealed capsules or units for holding the methyl myristate (or any other substance used in carrying out the invention) can be made e.g. of aluminum foil, tin foil, lead, paper, gelatin, or a thin plastic foil. The capsules can be used repeatedly and it will be understood that any material meeting the above described conditions can be used in the capsules or units. The invention can be applied to spraying varied materials, e.g. insecticides, germicides, bactericides, medicaments, fumigants, deodorants, paints, lacquers, to liquids and finely divided solids and can be used in any device of suitable construction. The stabilizer can be placed in the propellant liquid also without the use of a container, e.g. a capsule, for the stabilizer. When the propellant filled in the nebulizer or like device is used up, the device can be refilled with the propellant and the stabilizer used again.

The propellants used in carrying out the present in-' vention can be, for example, fluorinated hydrocarbons such as trichlorofluoromethane, dichlorodifluoromethane, chlorotrifluoromethane, chlorodifluoromethane, 1.1.2- trichloro-l.1.2-trifluoroethane, sym-dichlorotetrafluoroethane and their mixtures. Equivalent other materials, e.g. propane, butane, and their mixtures can also be used. In addition to the substances mentioned above as heat suppliers upon their solidification, other simularly acting substances can be used, e.g. molten inorganic salts which evolve heat during their solidification and/ or crystallization, for example Na B O .10H;,O, MgSO .7I-I O, AlCl .6H O and the like.

These and other modifications can be made without departing from the scope of the invention, as defined in the appended claims.

What is claimed is:

1. Apparatus for dispersing, spraying, atomizing, and nebulizing a liquid medium by the action of a gas evolved from an organic liquid, self-pressurizing propellant, comprising a closed, propellant container, a body of said liquid organic self-pressurizing propellant within the propellant container and partially filling the container providing an evolved gas space over the propellant liquid, a valve mounted atop the container efifective upon actua tion thereof to open the valve to communicate the gas space with the outside of the container, whereby upon actuation of the valve to open it, gas is evolved from the liquid propellant and issues through the valve, and a plurality of scaled individual packages disposed in said body of liquid propellant and having heat permeable Wrappings and containing methyl myristate, whereby there is provided a liquid substance adapted to solidify with the evolution of heat upon cooling thereof by said propellant and resulting from vaporization and gasification of propellant, in order to maintain the temperature of the liquid propellant at a predetermined level during delivery of propellant from the container.

2. Apparatus for dispersing, spraying, atomizing, and nebulizing a liquid medium by the action of a gas evolved from a liquid self-pressurizing propellant, comprising a closed, propellant container, a body of said self-pressurizing liquid propellant within the propellant container and partially filling the container providing an evolved gas space over the propellant liquid, a valve mounted atop the container effective upon actuation thereof to open the valve to communicate the gas space with the outside of the container, whereby upon actuation of the valve to open it, gas is evolved from the liquid propellant and issues through the valve, and a plurality of sealed individual packages disposed in said body of liquid propellant and having seat permeable wrappings and containing a liquid substance adapted to solidify with the evolution of heat upon cooling by said propellant and resulting from vaporization and gasification of propellant, in order to maintain the temperature of the liquid propellant at a predetermined level during delivery of propellant from the container, and a second container disposed within the first-mentioned container and immersed in the liquid propellant, said sealed packages being deposited in said second container, said second container having openings retaining said sealed packages therein while permitting circulation of liquid propellant therethrough.

3. Apparatus for dispersing, spraying, atomizing, and nebulizing a liquid medium by the action of a gas evolved from an organic liquid, self-pressurizing propellant, comprising a closed, propellant container, a body of said liquid organic self-pressurizing propellant within the propellant container and partially filling the container providing an evolved gas space over the propellant liquid, conduit means for communicating said gas space within the propellant container with the atmosphere, valve means disposed in said conduit effective upon actuation thereof to open the valve to permit flow of evolved gas from the propellant container to the atmosphere, a closed container for said liquid medium, means communicating said conduit and the closed container for said liquid medium for aspiration of liquid medium from the liquid medium container by evolved gas passing through the conduit to the atmosphere, whereby to obtain said dispersing, spraying, atomizing, and nebulizing of said liquid medium, and a plurality of sealed individual packages disposed in said body of liquid propellant and having heat permeable wrappings and containing methyl myristate;

whereby there is provided a liquid substance adapted to solidify with the evolution of heat upon cooling by said propellant and resulting from vaporization and gasification of propellant, in order to maintain the temperature of the liquid propellant at a predetermined level during delivery of propellant from the container.

4. Apparatus for dispersing, spraying, atomizing, and nebulizing a liquid medium by the action of a gas evolved from a liquid self-pressurizing propellant, comprising a closed, propellant container, a body of said self-pressurizing liquid propellant within the propellant container and partially filling the container providing an evolved gas space over the propellant liquid, conduit means for communicating said gas space within the propellant container with the atmosphere, valve means disposed in said conduit effective upon actuation thereof to open the valve to permit flow of evolved gas from the propellant container to the atmosphere, a closed container for said liquid medium, means communicating said conduit and the closed container for said liquid medium for aspiration of liquid medium from the liquid medium container by evolved gas passing through the conduit to the atmosphere, whereby to obtain said dispersing, spraying, atomizing, and nebulizing of said liquid medium, and a plurality of sealed individual packages disposed in said body of liquid propellant and having heat permeable wrappings and con- References Cited in the file of this patent UNITED STATES PATENTS 1,929,511 Mulkey Oct. 10, 1933 2,289,425 Hogan July 14, 1942 2,362,784 Ward Nov. 14, 1944 2,677,367 Telkes May 4, 1954 2,866,324 Bruno Dec. 30, 1958 FOREIGN PATENTS 1,112,085 France Nov. 9, 1955