US2954935A - Means for pressurizing a container - Google Patents

Description

Oct. 4, 1960 c. L. STEARNS ETAL 2,954,935

MEANS FOR PRESSURIZING A CONTAINER Filed June 3. 1957 INVENTORS CARL LOUIS STEARNS BY LLOYD FRANK HANSEN FIG. 2

ATTORNEY States Patent Patented Oct. 4%, lS'SO 2,954,935 MEANS non PRESSURIZING A CONTAINER Filed June 3, 1957, ser. No. 663,238 4 Claims. (Cl. 239-373) This invention relates to a dry propellant consisting essentially of a porous desiccant absorbent such as calcium silicate, preferably compacted to a solid cake, having absorbed therein a readily liquefiable volatile propellant gas such as a haloalkane. The dry propellant is particularly suitable for aerosol bombs.

Pressure propellant dispensers, sometimes called aerosol bombs, are in common use and becoming increasely important commercially. Pressure dispensers often use such materials as the haloalkanes as propellants, which haloalkanes are normally gaseous at room temperature and pressure but which can be condensed to a liquid by either raising the pressure at room temperature, or by reducing the temperature. hese propellants are used to propel liquids and solids. The materials to be propelled have been either dissolved in the propellant or suspended in the propellant or formed into a mixture which is compatible with the propellant as either a dissolved or dispersed phase.

The methods of loading such pressure dispensers have been based upon either chilling all components and loading the chilled components into the container, and sealing the assembly at reduced temperature, or the containers have been loaded with the propellant under pressure. When loading under pressure some of the components may be loaded into the container before the container is pressurized.

Either method has marked disadvantages. For example, when chilled, certain emulsions are caused to separate, some materials are temperature sensitive, and the cost of chilling, both the first cost of the equipment and the cost of maintaining under chilled conditions while filling, has been comparatively high. Similarly, when loading under pressure, special equipment is required to control the filling operations and it is difficult to measure the exact filled quantities to insure reliably reproducible results. It is commercially disadvantageous to produce non-uniform products when these products are to be sold to a discerning clientele; even if the non-uniformity has no functional disadvantages.

It has now been found that pressurized containers can be loaded at room temperatures by using a propellant absorbed in an absorbent. A good desiccant, with a large absorptive capacity which is preferably easily compressible to a solid cake, or otherwise formed into a solid cake, as for example using a binder, which compressed cake readily absorbs comparatively large quantities of the propellant in liquid form, is-soaked in the liquid propellant at a low temperature, and the cold propellant containing cake may then be used at room temperature and pressure as an insert in the system to be pressurized, and the system is sealed before the propellant evaporates.

The cake may conveniently be of calcium silicate or mixed calcium alkali silicates or of silicon dioxide in finely divided form. The cake may be compressed at from 500 to 10,000 pounds per square inch to a desired suitable shape. At such pressures the finely divided silicate or silicon dioxide or mixtures thereof are compacted into an 2 easily handled cake. The cake is then placed in the chilled propellant. By keeping the propellant cold, losses are minimized. The cake absorbs more than its own weight, and frequently at least four times its own weight, of the propellant. Other propellants such as nitro gen dioxide maybe used but the more convenient commercially obtainable propellants are the haloalkanes such as monoch-lortrifluoromethane, dichlorodifluoromethane, trichloromonofiuoromethane, monochlorodifluorornethane, dichloromonofluoromethane, monochloropenta-fluoroethane, dichlorotetrafiuoroethane, trichlorotrifluoroethane, tetrachlorodifluoroethane, methyl chloride, methylene chloride, ethyl chloride, trichloroethylene, etc, and theirmixtures.

The haloalkanes may be mixed with hydrocarbons having similar volatility characteristics, such as the four and five carbon alkanes, including butane, isobutane, and pentane. The hydrocarbons which are readily liquefiable gases may be used as the propellants, however such hydrocarbons are quite flammable, and present the possibility of a fire hazard if used alone. Where such a fire haz ard may be of minor importance, and where the lower cost of the simple alkanes is an advantage, their use becomes of economic importance, and is Within the scope of this invention. In many instances a blend of the alkanes with the haloalkanes gives a mixture which is more economical than the haloalkanes alone, and this mixture may be blended to have the desired temperature, pressure, and solubility relationships, by those skilled in the art of pressurized container fabrication and filling.

Such a choice of the haloalkanes and/or alkanes is made that the pressure of the mixture is Within desired limits. The choice of low, medium and high pressure propellants for particular applications and containers requiring such pressures is'known to those skilled in the aerosol industry.

The size of cake varies with the requirements for the amount of propellant gas. For non-soluble liquid systems, a small amount of propellant is adequate. For liquids in which the propellant is soluble, comparatively large amounts are required. It is desirable that the propellant gas be soluble in the material to be dispensed when aerosols are to be produced, as the dissolved gas propellant flashes, thus giving finer particle sizes. Slightly soluble systems tend to give foams, and insoluble systems tend to eject the material to be dispensed, if a liquid, as a liquid stream. The release valve can be chosen to give greater or less dispersion as preferred. The material to be dispensed and propellant system are chosen to have a.desired solubility, and the propellant is chosen to have preferred pressure characteristics. The higher the pressure, the greater the dispersion accomplished. Usually lower pressures are desired to permit the use of lower cost containers.

The present propellant. cake is particularly useful for pharmaceutical ointments, creams and greases; and for food products such as catohup or mayonnaise. The haloethanes are in general more soluble in oil systems than in aqueous systems, although the solubility varies from member to member of the series.

The propellant cake may be formed with a hole in the middle to slide over a dip tube in the container or the cake may be fastened by a retaining bracket, or allowed to remain freely suspended in the container. Similarly, the propellant cake may be allowed to contact the material to be dispensed or it may be separated therefrom by a flexible diaphragm or piston. Where a solid liquid stream is desired, preferably a combination is used such that the propellant is not readily soluble in the material to be dispensed, or a diaphragm or piston is used to separate the material. If the propellant is soluble in the m-ate-.. rial to be dispensed, a larger quantity of propellant is.

- and allowed to remain therein until it has absorbed a desired quantity of propellant-normally a matter of not more than about a minute is necessary, though a longer period guarantees more complete absorption. The cake may bestor'ed in the chilled propellant until needed; The

propellant containing cake is removed from the chilled liquid propellant bath, rapidly positioned in the container, and the container ispromptly sealed. On standing, part of the propellant evaporates from the cake, and pressurizes the container until equilibrium conditions are obtained. Part of the propellant remains in the cake. At

the time of use as more propellant in vapor form is re-- quired to maintain pressure as the material to be dispensed is discharged, additional propellant is released from the cake.

Although not limited thereto, as illustrative of certain embodiments of this invention a detailed description of these embodiments is shown in the accompanying drawings and the description thereof in which:

Figure 1 shows a pressurized container having a cakesupported on the dip tube;

Figure 2 is an embodiment in which the cake is loose in the container;

Figure 3 is a detail of one form of valve suitable for dispensing liquids.

In Figure 1 is shown a container body 11 having a valve assembly 12. From which valve assembly extends a siphon tube 13 leading towards the bottom of the container body. Surrounding the siphon tube and supported thereby is a propellant impregnated cake 14. In the container body is the material to be dispensed '15. The container body may be any of the conventional types used for pressure dispensing, but conveniently, as illustrated, is a round can having an inwardly dished top 16 and bottom 17.

Many different valves may be used depending upon the state of division desired, the type and characteristics of the material to be dispensed, and the pressure; One

type of valve suitable for liquids is shown at Figure 3.

The valve body 18 has flange '19 for attachment to the container top, and interiorly of the valve body a shoulder 29. Held against this shoulder is a valve washer 21 which rests on a flange 22' on the operating pin 23. The operating pin bearing the washer is held against the shoulder by a spring 24 which in turn is held in place by the siphon tube 13 or a retaining pin. Above the valve body is the spray head- 25 in which is a spray orifice '26 which is in communication with the liquid passage 27 in the valve body. The valve body holds plastic release button 28 in place against the valve body. of rubber or a plastic and when depressed in turn depresses the operating pin-which lifts the washer from the shoulder of the valve body and permits the material to be dispensed, to flow through the siphon tube, the liquid passage and the spray orifice. Valves of this type and others which may be used are known to those in thetrade and the details of the valve do not form an essential part of this invention.

A larger orifice is used for more viscous materials. A smaller orifice normally gives a finer degree of dis-' persion to the discharged material, and should such dis persion be desired, such a small orifice is used.

This release button is In loading the container conveniently the sides and bot' tom. of the container body are assembled, the material to-be dispensed loaded intoithe container body, and the cake is placed about the siphon tube. The cake may be a placed about the siphon tube before Or after the cake is impregnated with the propellant. Conveniently, the cake is pressed on the siphon tube and the top containing the valve and siphon tube is chilled at the same time the cake is impregnated, and placed on the rest of the con tainer body and sealed thereto to form thecomplete assembly.

Figure 2 illustrates an embodiment in which the propellant cake '29 is placed loose in'the' container before the top is assembled. thereto. Whereas aholder forthe cake maybe used, it is normally unnecessary.

Example, 1

A container body large enough to hold 4 ounces of water and known in thetrade as. a 3 ounce can because cium silicate of the grade sold asMicro-Cel by Johns Manville Sales Corporation is compressed with a pressure of 1000 lbs. into a disc about inch in diameter and V2 inch thick with a hole large enough to be placed around the siphon tube. The compressed cak is placed in a liquid mixture of 50% trichloromonofiuoromethane and 50% diehlorodifiuoromethane which mixture is chilled in a Dry Ice -acetone bath. The cake is allowed to remain in the haloalkane mixture for about 5 minutes during which time it absorbs about four times its own weight of the propellant mixture. Using tongs to keep from freezing the fingers, the cake is placed over the siphon tube and thevalve assembly is placed over the filled container body and sealed thereto rapidly. The complete assembly is permitted to attain temperature equilibrium and is then ready for use. The pressure developed in the can is about 32 poundsper square inch at F. The complete assembly is stable for a period of at least several months.

By pressing the releasebutton the catchup is forced from the spray head as a thin solid ribbon which may be applied as desired.

. Example 2 Theprocedure of Example 1 is repeated using 3 ounces of a mastitis ointment such as described in Patent 2,640,- 801,'Burkhart and Vance, Aureomycin OintmentjJune 2, 1953. The resultant dispenser is storage stable and releases a thin uniform ribbon of the ointment when the release button is pressed.

Example 3 i Example 4 minutes, placed about thie'siphonfltube of a valve and cover assembly, .and sealed in the container body. After attaining temperature equilibrium, the insecticide may be I sprayed in conventional fashion. f

We claim:

1. Means for pressurizing a container comprising: a container body, and inside the container body, a porous desiccant power cake impregnated with a readily liquefiable volatile propellant which is normally gaseous at room temperature and pressure.

2. Means for pressurizing a container comprising: a container body, and inside the container body, a porous desiccant powder comprising calcium silicate cake impregnated with a readily liquefiable volatile haloalkane propellant which is normally gaseous at room temperature and pressure.

3. A method of assembling a pressurized container having a dispensing valve and a material to be dispensed which comprises: (a) filling an open container body with the material to be dispensed at substantially normal room temperature and pressure, (b) separately compressing a porous desiccant powder into a cake, (0) impregnating said cake at low temperature with a readily liquefiable volatile propellant which is normally gaseous at room temperature and pressure but which is in chilled liquid form, and (d) comparatively rapidly transferring the chilled liquid impregnated cake to the container body and sealing the container.

4. A method of assembling a pressurized container having a dispensing valve and a liquid to be dispensed which comprises: (a) filling an open container body with the References Cited in the file of this patent UNITED STATES PATENTS 1,936,848 Masury Nov. 28, 1933 2,748,984 Seymour June 5, 1956 2,772,922 Boyd et a1 -Dec. 4, 1956 FOREIGN PATENTS 654,045 Great Britain June 6, 1951 OTHER REFERENCES Propellants for Low-Pressure Liquified Gas Aerosols" (Fulton), published in Industrial and Engineering Chemistry, April 1948 (pages 699-700 relied on).

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