US3891147A - Process for storing a liquid for its distribution in the gaseous state - Google Patents

Abstract

A method of storing liquified gas under pressure in a container from which the liquid is released as a gas into an atmosphere or region at a lower pressure than the storage pressure. This container additionally contains a solid polymer on which the liquid acts as a swelling agent so that the polymer becomes a gel which releases the liquid stored therein as a gas.

Description

United States Patent n 1 m1 3,891,147

Kleine June 24, 1975 l l PROCESS FOR STORING A LIQUID FOR i561 References Cited ITS DISTRIBUTION IN THE GASEOUS UNITED STATES PATENTS STATE worms 7 :934 Gardner 239/6 [75] Inventor: Jean Jacques Kleine, Letruz-Sevrier. 3/293 W964 S r 239/55 Frurmc 3.729.289 4/1973 Bouvler 43l/344 3.8l5,828 6/l974 Engel 239/6 [73] Assignee: S.T. Dupont, Paris, France I22] Filed: Jan. l0, I974 [2| 1 Appl. No.: 432,329

Primary [imminer-Lloyd L. King Attorney, Agenl. or FirmWaters Schwartz & Nissen Related U.S. Application Data l57l P T [62] Division Ur Scr, NU. zmm e Sept, 12, 1972. Par. A mellmd of i f f Pressure a N container from whlch the hquld is released as a gas into an atmosphere or region at a lower pressure than |3U| Foreign Appficalion priority Data the storage pressure. This container additionally contains a solid polymer on which the liquid acts as a Sept, I3. I97! l'runcc 7|.32946 .Iunc r m2 Fr'tlncc .4 7120346 l l the polymer. hemmes gel WhlCh releases the llqllld stored therein as a gas. I52] US. Cl. 239/6 [51 I lm. Cl. A6lL 9/04 [58} Field of Search 239/6, 34; 53/4; 206/7; 8 Claims, 7 Drawing Figures 1 PROCESS FOR STORING A LIQUID FOR ITS DISTRIBUTION IN THE GASEOUS STATE CROSS-RELATED APPLICATION This Application is a division of Ser. No. 288.396. tiled Sept. 12. 1972 and issued as U.S. Pat. No. 3.813.04] on May 28. I974.

The invention relates to a process for storing a liquifiable product in the liquid state. with a view to its distribution in the gaseous state.

A certain number of methods for distributing liquifia ble products in the gaseous state are known.

Depending on the vapor pressure of the liquid to be distributed. very line droplets of the liquid must be dispersed in a jet of gas. under pressure for example. The drawback of this distribution method is that the distribution device must be under this pressure.

The vapour pressure permitting. the gaseous distribution of the liquid can be sufficiently ensured by using merely the gaseous air located at the top of the storage enclosure. Depending on the desired distribution. it is necessary that the outlet be provided with either a pressure reducing device or with a device limiting the rate of flow. or with both. The main drawbacks of this storage and distribution method is that the auxiliary membcrs considerably increase its cost price.

This is why it has been proposed to provide the storage enclosure with a double chamber: a so-called storage chamber and a distribution chamber into which is introduced a predetermined amount ofliquid which vaporizes therein before being distributed. However. this distribution method has the drawbacks of necessitating a device for determining the amount of liquid admitted into the distribution chamber. of being discontinuous and of resulting in a non-constant distribution of each vaporized amount and of reducing the volume available for storage. due to the existance of the distribution chamber.

lt has also been proposed to direct the liquid to its distribution point by capillary means for example. by means of a wick or a capillary tube. However. the draw back of this distribution method is that it necessitates, in addition to a pressure reducing device and/or a device limiting the rate of flow. a transformation device from the liquid to the gaseous state.

In another proposed solution. the liquid storage enclosure is filled with a porous material such as cotton or polyurethane foam. By capillary action. the porous material keeps the liquid in its pores. which liquid is therefore never. in its liquid state. in contact with the pressure reducing device. if there is one. or with the device limiting the rate of flow. This distribution method is thus more advantageous. but it has the drawback of reducing the useful capacity of the storage enclosure.

Finally. it has been proposed to dispose. in the stor age enclosure of the liquid. a polymeric foam with open cells. for example a polyurethenc foam. As the liquified product is introduced under pressure. this foam is soaked with liquid like a sponge and is also compressed so that it acts mechanically. by elasticity. at the moment when the product is distributed in the gaseous state. the amount of product stored however remains about the same as that which would be stored if a foam with open cells was not being used. and contrary to statements by certain authors. a storage method of this type does not make it possible to eliminate the auxiliary cut-off apparatuses so that this storage method has never been used successfully in practise. for example for supplying gas lighters from a reservoir of liquified fuel gas.

An object of the present invention is to remedy these drawbacks by providing a method of storing a liquifiable product in the liquid state with a view to its distribution is the gaseous state and make it possible to eliminate the auxiliary cut-off members for the gases.

There is provided according to the invention a process for storing a liquifiable product in the liquid state with a view to its distribution in the gaseous state into an atmosphere whose pressure is less than the storage pressure. said method comprising disposing in the storage enclosure. in conjunction with the liquid product to be distributed. a solid polymer with respect to which this liquid acts as a swelling solvent.

Certain liquid products act. with respect to certain polymers. as swelling solvents. i.e. as solvents which cause the elastomer in question to swell. by acting on the intermolecular connections (or bridges) between chains without causing the complete dissolution of the polymer. the latter being. after the action of said swelling solvent. in the form of a gel. but again finding the integrality of its initial products after removal of said liquid product. Polymers having this property have been previously described in the prior art and it is known that it is a question of polymers having crosslinks which. in the absence of these cross-links would be soluble in the solvent in question but which. due to these cross-links. swell and form gels until the osmotic pressures balance the resilient tensions of the lattice. The bridges between the chains of the polymers may be made by covalent connections. by ionic co-ordination connections by hydrogen connections or by crystallites.

The many tests carried out by the applicant have. however. proved that. for a given liquid. stored according to the present invention and intended to be distributed in the gaseous state. the polymers which can be used must have a solubility parameter which differs at the maximum by i 2.0 and preferably by i 0.5 from that of the stored product in question. Moreover. the temperature for transformation to the viscous state of these polymers must be at the most equal to 50C.

Only polymers which fullfil this definition will there fore be considered as lying within the scope of the in vention. the present description and the claims which will follow.

Thus. for example, polysiloxanes which have a solubility parameter of 7.3 can be used for storing liquified butane. the solubility parameter of which is 6.75.

The process according to the invention results in findings by the applicant during numerous tests which have proved that by placing. in the storage enclosure of a liquified product and in conjunction therewith. a polymer. with respect to which it acts as a swelling solvent. the gel obtained has the surprising property of releasing the stored product only in its gaseous state at the moment when it is distributed into an atmosphere whose pressure is less than that of the storage enclosure.

A first advantage of the process according to the invention lies in the fact that the presence of a gel in the.

storage enclosure permits the use of the latter both as a stationary reservoir as well as a movable reservoir.

A second advantage lies in the fact that the discharge of the liquid in the entirely gaseous state makes it possible to remove the devices intended to transform the fuel from its liquid to its gaseous state.

A third advantage relates to the amount of liquid which can be stored in a given reservoir. Indeed. tests have been carried out by the applicant to determine the liquified amount of gaseous hydrocarbons which could be stored. on the one hand in an empty reservoir and on the other hand in the same reservoir containing a porous material and thirdly in the same reservoir con taining a polymer according to the invention. These tests have proved that the process according to the in vention makes it possible to store greater quantities of liquified products. all things being equal.

The storage process according to the invention has numerous applications.

A particularly important application relates to stored gas combustion devices such as lighters for smokers. luminous gas lamps or gas heating apparatuses wherein Iiquified hydrocarbons. particularly aliphatic hydrocarbons such as butane. propane. pentrane or the like are used individually or in combination as a fuel. these by drocarbons having the property of causing certain polymers to swell.

Another application relates to the transportation. over great distances. by vehicles provided with tanks or by ships of the type designed to carry liquified natural gas. of these liquified hydrocarbons the importance of which is becoming increasingly greater.

Another application. always in the case of liquified hydrocarbons. relates to the storage of these hydrocarbons in vehicles with a combustion engine. with a view to supplying these engines. In fact. it is known with refercnce to the fight against atmospheric pollution that the liquified hydrocarbons tend to replace the liquid hydrocarbons. the combustion of which results in much more harmful products (unburnt products. carbon monoxide. etc

Another application relating to other types of liquified compounds distributed in the gaseous state into the ambient atmosphere. relates for example. to deodorizing products or insecticides.

The numerous examples which will be described in the following description relate particularly to the case of liquified hydrocarbons. which is very important as hasjust been indicated. This application. however. only aims to illustrate the process according to the invention and must not be regarded as Iimitative.

However. it will be pointed out again that for liquified hydrocarbons stored in the liquid state with a view to their distribution in the gaseous state. the preferred polymers which can be used are divided into seven large classes of products. namely: polysiloxanes (so-called "polymers of silicons"); polyisoprenes. natural (latex) or synethetic; polyolefins with transverse connections. obtained by action of radiations or peroxides; polyalkylstyrenes with cross-links; block polymers. at least one constituent part of which has a maximum affinity for the solvent: polymcthylpentenes'. butyl rubber with weak links between the chains.

The polymer used may be introduced into the storage enclosure in the solid state. It may also possibly be pt Iymerized in the storage enclosure before it is filled with the compound in the liquid state intended to be distributed in the gaseous state. This latter modification for carrying out the invention may be found to be advantageous for certain applications (formation of liqui ficd fuel gas cartridges which cannot be refilled for gas lighters. for example).

Various devices for carrying out the invention will also be described in the following. but they will not be Iimitative.

The accompanying drawings given merely by way of a non-limiting example. illustrate various embodiments of an enclosure for storing a liquified fuel gas utilizing these advantages of the storage process according to the invention. In these drawings:

FIG. I is a vertical section showing a first embodimcnt according to the invention.

FIGS. 2. 3. 5 and 6 are respectively views similar to FIG. I of four variations. and

FIGS. 4 and 7 are detail views illustrating other variations.

In the embodiment shown in FIG. I. a hollow body I. which cannot be refilled. contains a plurality of pieces 2 of a solid elastomer with respect to which the liquified fuel gas to be stored acts as a swelling solvent. An aperture 3 formed at the top of the body I makes it possible to supply a burner with fuel gas without the interposition of a cut-off system.

In the modification. according to FIG. 2. the hollow body 4 is divided into two separate chambers 5 and 6 respectively by a grid. latticework or more usually a support 7 provided with apertures. secured in the body I and through which communication between the two chambers is effected. A filling valve 8 provided in the base ofthe body 4 makes it possible to fill the chamber 5 with a liquified fuel gas. the liquid passing through the support 7 so as to impregnate a solid polymeric mate rial contained in the chamber 6. A burner (not shown) is supplied with fuel gas by way of the aperture 9 formed at the top of the body 4.

The embodiment according to FIG. 3 is derived directly from that of FIG. 2. The hollow body 10 is divided into two chambers 11 and 12 by a grid 13 or the like. however. the elastomer intended to be impregnated with liquified gas is constituted by a simple membrane 14 held against the grid I3 by a ring I5 force fitted into an inner groove of the body I, the grid itself bearing against a shoulder of the inner walls of the container. The chamber II which may be filled with liquified gas by a valve 16 has a much greater volume that in the case of the embodiment shown in FIG. 2, whereas the chamber 12 has a minimum volume in communication with the distribution aperture I7. The membrane 14 ensures a continuous distribution of gas. releasing the latter through the face located opposite the aperture I7. whereas through the opposite face. it absorbs an amount of liquified gas which may or may not be equal to the amount of gas released.

FIG. 4 is a detail view ofa modification of the device of FIG. 3. wherein the elastomeric membrane I411 surrounds the grid 131:.

In the embodiment according to FIG. 5. the hollow body 18 comprises a main chamber 19 which can be filled with liquifed gas by the valve 20. The liquified gas impregnates a polymeric material which fills a tubular member 21 made of gridding and connected to the distribution aperture 22.

As shown in FIG. 7. the tubular element ZI made of gridding. may be replaced by a tube 23 of any material containing no polymer. but having perforations closed by a suitable macromolecular material 24.

Finally. in the modification according to FIG. 6. the storage enclosure 25 comprises no more than one single chamber 26, whose inner walls, with the exception of the part adjacent the filling aperture 27. are covered with a layer 28 of a solid polymer so as to form a kind of pocket which receives the liquid by way of aperture 27, the gas being released directly through the membrane 28 on a level with the distribution aperture 29.

When a storage chamber of the type which has just been described is intended to supply a gas combustion device. it may he made integral with the device and may be filled with liquified gas either directly by way of the filling aperture or by means of a "refill" constituted by an element of a macromolecular product having a suitable shape and volume. and previously saturated with liquified gas. Detachable enclosures may also be used constituting disposable refills.

EXAMPLE I This example is intended to illustrate the fact that only polymers with weak transverse connections (weakly linked polymers") may be used for carrying out the invention Three types of polymers have been used for this purpose; on the one hand a polystyrene without crosslinks manufactured by the Shell Company, a polystyrene with 2 percent cross-linking (beads sold under commercial name IONAC} and polytert butylstyrene with 0.025 percent cross-linking manufactured by the DOW Company and bearing the commercial name "IMBIBER HEAD P R l7l-7 l The tests have been carried out by dipping samples, for one day. in liquified n-butane or in liquified pentane. greatly in excess. The excess liquid has then been removed and the ratio of the weight of liquid absorbed by the polymer to the ini tial weight of the polymer (ratio designated by the expression capacity of the polymer) was noted.

The results obtained are illustrated in the following Table l.

out the invention with the polymers each belonging to the above-mentioned classes as capable of being used in the case where the stored liquid is a hydrocarbon in the liquid state. The following polymers have been used: I. Polysiloxanes:

la. foam with closed cells and having a low density manufactured by Silicone Engineering Ltd." 2a. RTV foam [abbreviation of Room Temperature Vuleanizing) 558; 2. Polyisoprene:

isoprene foam with closed cells manufactured by Shell (commercial name Latex 700);

3. Polyolefins with cross-links:

3n. cross-linking by peroxide: polyethylene manufactured by Sekisui. Japan (commercial name Softlon BN-30). 3h. cross-linking under radiations: polyethylene manufactured by Furakawa Electric. Japan (commercial name: Minicel L-200);

4. Polyalkylstyrenes with cross-links:

poly-tert-butylstyrcne. manufactured by DOW (com mercial name: lmbiber Bead XE 0l00.3l) with 0.025 percent transverse connections; 5. Black polymers:

olefin styrene manufactured by Shell, of the type of the products Kraton of this Company (commen cialname GXT 0650).

6. Polymethylpentene:

product sold by LC]. under the commercial name TPV RT 20.

7. Butyl rubber with weak linking:

product sold by Polysar Polymer Corp. Ltd, Canada. under the commercial name Polysar Butyl XL-20 Tests for all these samples have been carried out by dipping them for one day into liquified n-butane (except for sample No. 7 which was clipped in a mixture TABLE I POLYMER TEST IN nbutane Test in pentane Appearance of Capacity of Appearance of Capacity of the polymer the polymer the polymer the polymer non-crosslinked dispersed 0.2 dispersed 0.0 polystyrene Polystyrene unchanged 0.0 unchanged 0.0 with 2'4 appearance appearance crosslinking Poly-tert- Swelling I l.4 Swelling 20.0 butyl-styrenc (after 7 days) with 0.015%

CI'DSS- linking This table clearly shows that only polymers with :1

comprising 20 percent by weight n-butane and 80 perlow degree ofcross'linking make it possible to store liq- 55 cent by weight isobutane). or in liquified pentanev As uified nbutane or liquifed pentane efficiently.

EXAMPLE ll This example illustrates different ways of carrying in example I the excess liquid was removed and the appearance and capacity of the polymer was noted. The results obtained are collected in the following Table ll.

TABLE ll Polymer Sample Test in n-hutane Test in pentane Appearance of the Capacity of Appearance of the Capacity of Snelling These tests aim only to illustrate the imention and are not limitative. On the contrary. the applicant has carried out numerous tests. just as conclusive. on a large number of compounds belonging to the various aforementioned classes of polymers.

In the ensuing examples. the operation. which consists of heating the polymer used. three times with excess butane. until complete saturation. before it is used for storage. whether the liquid to be stored is butane or not. is termed extraction. Likewise. the treated polymer is termed the extracted polymer.

EXAMPLE III This example relates to the case where the stored product is butane in the liquid state.

Three storage tests have been Carried out. at C and for 20 hours. with three different polymers respectively a CAF 3 THlXO (registered trademark. abbreviation of colle a froid) polymerized at C for 24 hours. an RTV foam (abbreviation of Room Temperature Vulcanizing; rubber with silicon type) with it) per cent oil. polymerized at 150C for l hour. which has not been subjected to extraction and the same RTV foam after extraction. This foam has been obtained from commercialized products under the following names:

Rhodorsil 10558 Catalyst [0052 14 percent by weight of the preceding] Rhodorsil Oil Y-V-ZO (percent indicated above by weight of Rhodorsil [0558).

1. CAP STHIXO Characteristics of the polymer before absorption: Extract Weight: 100 g Apparent Volume: 97 cm Shape: cylinders having a diameter of 6 mm and a length of 20 mm. Swelling liquid presented (butane) Weight: 300 g Volume: 520 cm" Characteristics of the polymer after absorption:

Weight: 370 g Apparent Volume; 565 cm Shape: substantially the same as that before absorp tion. Swelling liquid absorbed:

Weight: 270 g Volume: 468 cm 2. NOT EXTRACTED RTV FOAM.

Characteristics of the solid polymer before absorption:

Weight: 100 g Apparent volume: 286 cm Shape: Diabolos large diameter of l2 mm small diameter of 8 mm height 20 mm with skin" on each base. Swelling liquid presented (butane):

Weight: 400 g Volume: 694 cm Characteristics of the polymer after absorption:

Weight: 443 g Apparent volume: 694 cm" Shape: maximum swelling in the center. Swelling liquid absorbed:

Weight: 343 g Volume: 594 cm lll 3. EXTRACTED RTv FOAM Characteristics of the solid polymer before absorption:

Weight: g Apparent volume: I43 cm Shape: Diabolos: large diameter l2 mm. small diame ter 8 mm height 2t) mm with skin on each base. Swelling liquid presented (butane) Weight: 800 g Volume: U88 cm Characteristics of solid product after absorption:

Weight: 825 g Apparent Volume: 1356 cm Shape: maximum swelling in the center: Swelling liquid absorbed:

Weight: 715 g Volume: l256 cm EXAMPLE IV This example relates to the case where the stored product is pentane in the liquid state: Three comparative tests have been carried out with the same polymers as in example l. at 20C and for 10 hours.

I. (AF 3THIXO Characteristics of the solid polymer before absorption:

Extract Weight: 100 g Apparent Volume: )8 cm" Shape: cylinder: diameter 6 mm length 20 mm Swelling liquid presented (pentane):

Weight: 200 g Volume: 319 cm Characteristics of the solid product after absorption:

Weight: 227 g Apparent volume: 301 cm Shape: substantially the same as that before absorption. Swelling liquid absorbed:

Weight: 127 g Volume: 203 cm 2. NOT EXTRACTED RTV FOAM 3. EXTRACTED RTV FOAM Characteristics of the polymer before absorption:

Weight: ltltl g Apparent Volume: 1-13 cm Shape: diabolos;

large diameter 11 mm small diameter 8 mm length Zll mm with skin on each base.

Swelling liquid presented (pcntanel Weight: hill) g Volume: 959 cm" Characteristics of the solid product after absorption:

Weight: emu g Apparent Volume: 993 cm Shape: maximum swelling in the center Swelling liquid absorbed:

Weight: 560 g Volume: 893 cm Examples Ill and IV clearly show the importance of the treatment by extraction of the polymers used. before their application to the storage of liquids. The fact that after a first absorption. an increase in the absorp tion rate of the polymers is noted, could be due to the extraction. by the swelling liquid, of soluble matter "present" in the polymer and which are usually added thereto to impart certain mechanical or chemical prop erties thereto. Naturally, this preliminary extraction could be effected by a compound other than butane and could comprise any number of successive absorptions and deposits.

These examples also show the amount of liquid stored varies depending on the polymer used and also on the structure of the polymer. In particular, it is ascertained that the rate of filling of a polymeric foam with closed cells is always greater than that of a compact elastomer. The applicant has also ascertained that macromolecular foams with closed cells have a second advantage which is due to the fact that the liquid is absorbed and deposited more quickly than with a compact macromolecular compound.

In order to determine if the amount of liquid which can be stored in a given macromolecular product is an inverse function not only of the dimensions of the storage container which may hinder swelling but also of stresses peculiar to its structure. two series of tests were also carried out which were made from solid products of identical material, but whose outer characteristics were different. ln the first case (Example V hereafter) the foam with closed cells which constituted the solid products had each of its two bases constituted by a skin. i.e. from a plane surface. evidently less flexible than an alveolar surface. while in the second case (Example Vl) only one of its bases was constituted by a skin. the other being constituted by an alveolar surface.

EXAMPLE V In this test. liquified butane was stored at 20C for 20 hours, using the same RTV foam as in the preceding examples.

The test conditions and results obtained were as follows: Characteristics of the solid polymer before absorption:

Extract Weight: ltlt) g Apparent Volume: 143 cm Shape: diabolos:

large diameter l2 mm small diameter 8 mm height 20 mm with skin on each base. Swelling liquid presented:

Weight: 800 g Volume: I388 cm" Characteristics of the solid product after absorption:

Weight: 690 g Apparent Volume: 1 I22 cm" 10 Shape: maximum swelling in the center Swelling liquid absorbed:

Weight: 590 g Volume: 1022 cm EXAMPLE Vl In this example a test was carried out which is exactly the same as that of Example III. with the single difference that one of the bases of the solid polymer used had a skin while the other base was deprived of a skin. Using the same amount of butane as before. in the same conditions the following results were obtained: Characteristics of the solid product after absorption:

Weight: 860 g Apparent Volume: [417 cm Shape: maximum swelling between the center and the base without skin. Swelling liquid absorbed:

Weight: 760 g Volume: l3l7 cm The comparison of these results with those of example V reveals the fact that the amount of liquid which can be stored by the process according to the invention is directly related to the structure of the solid polymer used for carrying out this process.

Other tests carried out by the applicant for the same purpose have also proved that. for the same solid polymer used. the amount of liquid stored depends on the sum of the volumes of the alveoles per unit of apparent volume.

Various tests. intended to illustrate the various ways of carrying out the invention. will now be described in the following examples, which are not limitative. These examples do not relate merely to the storage, in the liquid state. of compounds intended to be distributed in the gaseous state into the same temperature conditions, but also to the conditioning of products (normally liquid) at the temperature in question and consequently intended to be distributed in the liquid state. Indeed. these tests give valuable information about the function of the solid polymer used in the framework of the invention. Moreover. they prove that, at the limit, the process described in the main patent may also be applied to the storage of liquid products intended to be distributed in the liquid state by increasing the pressure inside the enclosure.

EXAMPLE VII Solid polymer used: Viton (registered trademark; a fluoric elastomer having as a base the copolymcr of fluoridc of vinylidene and of hexafluoropropylenc).

Product stored: acetone Storage temperature: 20C

Duration of storage: 20 hours.

The conditions and results of this test were as follows:

Characteristics of the solid product before absorption: Not extracted: Weight: 200 g Apparent volume: 109 cm Shape: smallplate: length 20 mm width 20 mm thickness l mm Swelling liquid presented:

Weight: Ztltl g EXAMPLE Vlll Solid polymer used: natural rubber Swelling solvent stored: hexane Temperature of the test: 20C Duration of test: 20 hours The conditions and results of the test were as follows: Characteristics of the solid product before absorption:

Not extracted Weight: 100 g Apparent volume: 107 cm Shape:

circular rings: outer diameter: mm inner diameter: 3 mm thickness: 3 mm Swelling liquid presented:

Weight: 200 g Volume: 303 mi Characteristics of the solid product after absorption:

Weight: 270 g Apparent volume: 364 cm Shape: substantially the same as before absorption.

Swelling liquid absorbed:

Weight: I70 g Volume: 257 cm EXAMPLE lX Polymer used: CAF 3 THlXO (registered trademark; product similar to that de' scribed in the preceding examples) Swelling solvent (product stored) hexane Temperature of the test 2ll( Duration of the test Zl) hours The conditions of the test and the results obtained are as follows:

Characteristics of the solid product before absorption:

Extracted Weight: 100 g Apparent volume: 97 cm Shape: cylinder:

diameter 6 mm length 20 mm Swelling liquid presented:

Weight: 300 g Volume: 455 cm Characteristics of the solid product after absorption:

Weight: 368 g Apparent volume: 504 cm Shape: substantially the same as that before absorp tion. Swelling liquid absorbed:

Weight: 268 g Volume: 407 cm EXAMPLE X Polymer used: natural rubber Swelling solvent (Liquid stored I: pentane Temperature of the test: 20C Duration of the test: 2U hours: The conditions of this test and the results obtained are as follows:

Characteristics of the solid product before absorption: Not extracted Weight: lllt] g Apparent volume: 108 cm" W Shape:

circular rings: outer diameter: H) mm inner diameter: 3 mm thickness 3 mm 15 Swelling liquid presented:

Weight: lUO g Volume: lbtl cm" Characteristics of the solid product after absorption:

Weight: l63 g Apparent volume: 208 cm" Shape: substantially the same as that before absorption. Swelling liquid absorbed:

Weight: 63 g Volume: Hit) em" EXAMPLE Xl Solid polymer: CAF 4 THIXO Swelling solvent: butane Temperature of the test: C

Duration of the test: 20 hours.

The conditions of the test and the results obtained are as follows: Characteristics of the solid product before absorption:

Not extracted Weight: 100 g Apparent volume: 9l cm Shape: cylinder:

diameter 6 mm length 20 mm Swelling liquid presented:

Weight: 200 g Volume: 347 cm Characteristics of the solid product after absorption:

Weight: 250 g Apparent volume 35l cm Shape: substantially the same as that before absorption. Swelling liquid absorbed:

Weight: l5(l g Volume: 260 cm EXAMPLE Xll Solid polymer: natural rubber Swelling solvent: carbon sulphate Temperature of the test: 20C Duration of the test: 20 hours The conditions of the test and the results obtained are as follows:

Characteristics of the solid product before absorption:

Not extracted Weight: ltltl g Apparent volume: I07 cm" Shape:

circular rings: outer diameter: H) mm inner diameter: 3 mm thickness: 3 min Swelling liquid presented:

Weight: 400 g Volume: 3l7 cm" (haracteristics of the solid product after absorption:

Weight: 430 g Apparent volume: 309 cm" Shape: substantially the same as that before absorption Swelling liquid absorbed:

Weight: 330 g Volume: 202 cm The above examples clearly show the various polymers which can be used in various physical forms. and the numerous applications of the process according to the invention both to the storage of liquified products and products normally liquid at ambient temperatures.

As has already been emphasized. one of the most important and most advantageous applications of the process according to the invention relates to liquilied fuel gases. in particular liquified. gaseous aliphatic hydro carbons.

ln this application, the storage process according to the invention has surprising advantages which were not evident to the man skilled in the art. These advantages will now be revealed.

Firstly, it is evident that the process according to the invention retains the advantages of processes for storing liquids with spongy supports. namely stabilization of the stored liquid and possibility of using the storage container in any position whatsoever.

With respect to known processes, the process according to the invention also has the advantage of improving the checking of the distribution, which in the case of easily combustible liquids, reduces the risks of explosion.

In order to illustrate the improvement made by the invention, a certain number of tests have been initiated of the combustion of butane either alone. or stored in polyurethane with open cells. or stored in cotton, or stored in RTV elastomer foams with closed cells or finally stored in elastomers of the (AF series.

All these tests were effected in the open air. During each test. the combustion of the same amount of butane was initiated. The supports used all had a thickness of 1cm and had, at the beginning of the test. the same evaporation surface as the free butane.

in these conditions, the results expressed as coefficient of combustion duration were as follows:

- butane along: 1.0; butane stored in polyurethane foam with open cells:

- butane stored in cotton: 1.9;

- butane stored in RTV elastomer foam with closed cells: 2.5;

- butane stored in compact elastomer of the (AF series: 3.0.

A second advantage made by the invention lies in the fact that the pressure ofthe gaseous air above the liquid stored in the storage container is less than that of the gaseous air in a container with liquified gas alone or in a container with gas and cotton or gas and alveolar foam with open cells.

The tests which have been carried out to illustrate this point have been greatly influenced by the variables which could not be exactly identified (probably varia tions in composition both of liquids and elastomcrs I.

Nevertheless. even if the favorable results which cannot be reproduced are excluded to retain only the aver age values of the results obtained, it is established that the process according to the invention is found to be very superior to the conventional processes. This is proved by the following numbers which relate to the value. in bars. at a temperature of 25C. of the relative pressure of the gaseous air in a storage container con taining a mixture of liquified hydrocarbons comprising (in percent by weight) 790 percent n-butane. l9.0 percent isobutane, 1.0 percent propane, 0.5 percent ethane and 0.5 percent pentane and butene:

with this mixture alone: 1.65

with this mixture and a polyurethane foam with open cells: L

with this mixture and a cotton: L65

with this mixture and an RTV elastomer foam with closed cells: l.5l

with this mixture and a compact CAF elastomer: 1.45

It is to be noted that the tests carried out by the applicant have proved that the difference between the gase' ous air pressures in the process according to the invention and in conventional processes is more accentuated for containers with a leakage having a constant crosssection.

Finally. in the application of the process according to the invention to the storage of liquified fuel gases intended to supply a combustion means, an extremely important advantage lies in the fact that the combustion device can be supplied directly without the interposition of a device for transformation from the liquid to the vapor state.

Another advantage peculiar to this application is due to the fact that the device limiting the rate of flow may be removed, which is usually mounted on the supply line of the combustion device so as to keep only a regulating device at the users disposal.

What is claimed is:

l. A process for storing. in the liquid state, a liquefiable product with a view to its distribution in the gaseous state, into an atmosphere whose pressure is less than the storage pressure, said process comprising disposing in the storage enclosure. in conjunction with the liquid product to be distributed, a solid polymer with respect to which the liquid acts as a swelling solvent; said polymer being absorbative of the liquefied gas and having a limited solubility parameter with respect to said liquefied gas so as to undergo swelling and form a gel which releases the liquid only in gaseous state. said solubility parameter of the polymer differing at most from the liquified gas by ED.

2. A process according to claim I, in which said poly mer is a foam with closed cells.

3. A process according to claim I, in which the solid polymer used was previously subjected to a treatment consisting of at least one absorption-deposit cycle with an excess liquid acting like a swelling solvent with respect to said polymer.

4. A process according to claim 3, in which the liquid used during the previous absorption-deposit treatment is the same as the liquid to be stored.

S. A process according to any one of claim I, wherein the polymer is polymerized "in situ in the storage enclosure before it is filled with the liquid to be stored.

6. A process according to claim I. in which the liquid to be stored comprises a major part of at least one liquefied saturated hydrocarbon and the solid polymer is selected from the group consisting of polysiloxanes:

ill

(ill

7. A pmccss according to claim I wherein said pol mcr is weukl cross-linked.

8. A process according to claim I wherein the solubility parameter of the polymer differs at most from the

Claims (8)

1. A process for storing, in the liquid state, a liquefiable product with a view to its distribution in the gaseous state, into an atmosphere whose pressure is less than the storage pressure, said process comprising disposing in the storage enclosure, in conjunction with the liquid product to be distributed, a solid polymer with respect to which the liquid acts as a swelling solvent; said polymer being absorbative of the liquefied gas and having a limited solubility parameter with respect to said liquefied gas so as to undergo swelling and form a gel which releases the liquid only in gaseous state, said solubility parameter of the polymer differing at most from the liquified gas by + OR - 2.0.

2. A process according to claim 1, in which said polymer is a foam with closed cells.

3. A process according to claim 1, in which the solid polymer used was previously subjected to a treatment consisting of at least one absorption-deposit cycle with an excess liquid acting like a swelling solvent with respect to said polymer.

4. A process according to claim 3, in which the liquid used during the previous absorption-deposit treatment is the same as the liquid to be stored.

5. A process according to any one of claim 1, wherein the polymer is polymerized ''''in situ'''' in the storage enclosure before it is filled with the liquid to be stored.

6. A process according to claim 1, in which the liquid to be stored comprises a major part of at least one liquefied saturated hydrocarbon and the solid polymer is selected from the group consisting of polysiloxanes; natural polyisoprenes; synthetic polyisoprenes; cross-lined polyolefins; cross-linked polyalkylstyrenes; block polymers having at least one constituent part with a maximum affinity for the solvent; polymethylpentenes; and butyl rubbers with weak bridging between chains.

7. A process according to claim 1 wherein said polymer is weakly cross-linked.

8. A process according to claim 1 wherein the solubility parameter of the polymer differs at most from the liquefied gas by + or - 0.5.

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