CA1125493A

CA1125493A - Supercooled fluids and methods of producing such supercooled fluids

Info

Publication number: CA1125493A
Application number: CA312,863A
Authority: CA
Inventors: Donald E. Truelock
Original assignee: Individual
Current assignee: Allegiance Corp
Priority date: 1977-10-31
Filing date: 1978-10-06
Publication date: 1982-06-15
Also published as: JPS6229475B2; FR2408808A1; FR2408808B1; GB2008554A; DE2844810A1; JPS5488871A; DE2844810C2; GB2008554B

Abstract

Abstract of the Disclosure This invention relates to a method of producing articles which generate heat at a substantially constant temperature for an extended period of time ? which are able to remain in a stable state until such time as the generation of heat is desired. The method also relates to supercooled fluids produced by such methods. The method involves the processing of supercooled fluids such as hypo to produce this stable state. As a first step, a suitable material such as ethylene glycol may be added to the super-cooled fluid to stabilize the supercooled fluid and to decrease the generation of heat in the supercooled fluid to obtain a desired temperature. The mixture is then heated to a relatively high temperature considerably above the melting temperature of the supercooled fluid. With the mixture at the high temperature, water is added to provide a particular specific gravity and an alkali is added to provide a particular pH.

The mixture may then be poured into rupturable pouches while being maintained at the high temperature.
The mixture in the pouches is then allowed to cool slowly to ambient temperatures and is placed in a separate container with a triggering material.

Description

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~ e illvelltion relates ~o a mctho(l or ~)roc(~;sin(3 supercooled fluids before the supercooled fluids are packaged. The invention particularly relates to methods of processing supercooled fluids to assure that the fluids will be retained in a fluid state until such time as it is desired to generate heat from the supercooled fluid. The invention further relates to a method of processing super-cooled fluids to assure that the generation of heat ~rom ~` the supercooled fluid will occur at a particular temperature.
~10 ~ The method also relates to supercooled fluids produced by such methods.
There are many different instances where it is desirable to generate heat for an extended period of time at a substantially constant temperature. For example, it is desixable to generate heat at a particular temperature for an extended period of time w}ien babies are to be bathed or otherwise administered to~in a hospital. It is further des1rable to generate heat at~a~particular temperature at the heél of a baby in order to facilitate the withdrawal 20~ of~b~1ood from the~véi~n or a~rte~ry of a baby for purposes of testlng the physlcal well-being of the baby. ~ -Various attempts have been made in the past to enerate heat at a predetermined and 5ubstantially constant temperature for an extended period of time. Until recently, ; it has~been difficult to provide such a generation of heat.
For example, chemicals have been mixed to produce an exothermic chemical reaction but the heat generated has peaked quickly at a relatively high value above the temper-, --1 .

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` 1125493 1 ature desired and has then decreased progressively to a

2 temperature below that desired. When the temperature of

3 the chemical reaction is above that desired, the patient

4 can become burned or produce other detrimental effects.
When the temperature of the chemical reaction is below 6 that desired, the patient does not receive beneficial 7 results of an optimal nature.

9 Supercooled fluids have been known for some time to generate heat at a substantially constant temperature.

I
11 The supercooled fluids melt from a solid state to a liquid I2 state at a particular temperature and then become triggered 13 from thé liquid state to a solid crystalline state at the 14~ particular temperature. During the time that the supercooled fluid becomes triggered to the crystalline state, it generates 16 heat~.

r ~ 17 18 Although the desirable characteristics of supercooled l9~ fluids have been known for some time, supercooled fluids have 20 ; had limited use. This has resulted~from certain disadvantages 21 ~in the supercooled 1uid. For example, although supercooled 22 fluids theoretically generate heat at a substant~ally constant ; 23 temperature, the temperature cannot always be pre-established . ~ ~
24~ with great accuracy. As an illustration, under some conditions, 25 ~ a supercooled fluid wlll generate heat at a temperature of 26 118F. and at other times the supercooled fluid will generate 27 heat at a temperature of approximately 120F. When a precise 28 temperature is to be provided such as for medicinal purposes, 29 such variations ln temperature can cause great concern and be somewhat detrimental to the well-being of a patient.

1125~93 1 There are other disadvantages to the use of super-2 cooled fluid. Supercooled fluids tend to be somewhat unstable, 3 particularly when subjected to relatively low temperatures.
4 For example, when supercooled fluids tend to be subjected to temperatures below the freezing point of water, they tend to 6 become automatically triggered from the fluid state to the solid crystalline state.

~, g This invention provides a method of processing supercooled fluids to overcome the above difficulties. When li processed by the method constituting this invention, the fluid 12 tends to remain stable in the liquid state for extended periods ~ 13 of time, even when the fluids are subjected to temperatures ;~3~ 14 below the freezing temperature of water. Furthermore, the fluids become triggered from the liquid state to the solid 16 crystalline state at a substantially constant temperature, 17 the value of which can be predetermined. The supercooled 18 ~ f~luid may constitute sodium thiosulfate pentahydrate.

20 ~ When supercooled~fluid lS processed by the method constituting this ~invention, a suitable material such as 22 ethylene glycol may be added to the supercooled fluid to 25~ enhance the stability of the supercooled fluid and to provide 24 for the generation of heat in the supercooled fluid at a desired temperature less than the melting temperature of the 26~ supercooled fluid. The mixture of the ethylene glycol and 27 the supercooled fluid is then heated to a relatively high 28 temperature considerably above the melting temperature of :
29 the supercooled fluid. With the mixture at the particular temperature, water is added to provide a specific gravity of : . .
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~-~ i llZ5493 a particular value and a suitable material such as sodium hydroxide or sodium carbonate is added to provide a particular pH.
The mixture may then be poured into rupturable packages while being maintained at the particular temperature.
The mixture is then allowed to cool slowly in the rupturable packages to ambient temperatures and a trigger is added in a separate container after the cooling of the mixture to ambient temperature. The container then holds the package of the supercooled fluid and the triggex in isolated relationship to each other. The trigger may constitute a suitable material such as sodium borate pentahydrate.

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More particularly, this invention provides a method of producing thiosulphate having properties of crystallizing in an aqueous solution in more than one crystalline phase and having superior energy-transferring properties in the pentahydrate phase and having properties of melting and crystallizing in a particular temperature ;range to provide the pentahydrate phase and having properties~of providing a second crystalline phase 20; with a second range of melting temperatures different from the particular temperature range, including the following steps:
' heating the sodium thiosulphate to a temperatuxe of at ; ~ least 16SF. for a suf~iaient period of time to melt all of the crystals in the sod~um thiosulphate, ,~, .
maintaining the pH of the fluid at a particular alkaline value, and ~
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maintaining the specific gravity of the fluid at a particular value.

In the drawings:

Figure 1 is a perspective view, partially broken away, of one embodiment of the invention; and Figure 2 is a sectional view substantially on the .
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: ' . , , `~ llZ5493 line 2-2 of Figure l; and Figure 3 is a schematic view showing apparatus used to provide the method constituting this invention.

In one embodiment of the invention, a pouch or packet 10 contains a supercooled fluid 12. The pouch is provided with a rupturable seal 14 along one edge, the seal being ruptured when subjected to a particular pressure such as results from a manual pounding or a manual squeezing ~ of the pouch. The pouch 10 is disposed in a container 16 S- ~ 10 which also contains a trigger material lB for the super-~cooled fluid. As will be seen, the trigger material 18 is disposed in isolated relationship to the supercooled fluid ~
; in the pouch 10.~ -1 . ~, ~,:

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11~5493 1 A number of different materials can be used as the 2 supercooled fluid 12. These materials include sodium sulfate 3 decahydrate, sodium thiosulfate pentahydrate (hypo), sodium 4 hydrogen phosphate, sodium chromate decahydrate, calcium chloride hexahydrate, magnesium chloride with water, magnesium 6 nitrate hexahydrate and urea/ammonium nitrate. The trigger material 18 in the container 16 may be sodium borate.

g When the pouch 10 is ruptured, the supercooled fluid 12 in the pouch is mixed with the trigger material 18 and 1i becomes triggered from the liquid state into a solid crystalline 12 state. This causes heat to be liberated at a substantially 13 constant temperature during the time that the supercooled fluid 14 is being converted into the crystalline state. The conversion f the supercooled fluid into the crystalline state occurs 16 over an extended period of time so that the temperature produced 17 at the surface of the container 16 is substantially constant . ~
for this extended period of *ime.
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20~ The particular temperature obtained ~y the triggering 21~ Of the supercooled fluid to the crystalline state can be con-22 trolled by the addition of another material into the supercooled 23 fluid to form a mixture. ~or example, when ethylene glycol is 24 added to hypo, the temperature produced decreases in accordance ':: ~:-~ 25 with the amount of the ethylene glycol added. When the mixture ~: :
i~ 26 of the hypo and the ethylene glycol contains approximately ten 27 percent ~10%) of the ethylene glycol by weight, the temperature 28 produced from the triggering of the hypo into the crystalline 29 state is approxlmately 104F. This constitutes a decrease from a temperature of approximately 116F. which is produced _5_ 1125~93 1 when the fluid in the pouch 10 is substantially only hypo.
2 A relatively small amount of ethylene glycol such as less 3 than approximately two percent (2%) by weight is also effective in the hypo to limit the size of the crystals produced from the hypo when the supercooled fluid is 6 triggered into the solid state. The amount of ethylene 7 glycol to approximately two percent (2%) tends to control '~ .
8 the size of the crystals produced by triggering the super-9 cooled fluid. The use of ethylene glycol for the above ~0 purposes is disclosed in co-pending application Ser ,; 3~ ~9 1i No. ~r64~ filed by Gustaf O. Arrhenius on l~ Lr-12 ~ and assigned of record to the assignee of record of 13 this application.
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In order that the mixture in the pouch 10 is stable 16 under a wide range of conditions and that it will produce a -~:
~ 17 ~ predetermined temperature when triggered, the mixture is , ~ :
18 processed by the method constituting the invention. As a lg~ first step, the mixture is disposed in kettles 20 made from a ;20~ suitable material such as stainless steel so that the super-21 cooled fluid in the mixture will not become contaminated.

22 The kettle~ 20 may be electrically heated and may be provided :
23 with closed tops to assure that contaminants are not introduced 24 into the kettles while the mixture in the kettles is processed.

The kettles are then heated electrically so that the mixture 26 in the kettles reaches a suitable temperature considerably 27 above the melting temperature of the supercooled fluid. For 28 example, the mixture may be heated to a suitable temperature 29 such as approximately 180F. An agitator 22 may be operated - , . : ,, ~:~ " , ~ -llZ5493 1 from the time that the melting of the supercooled fluid in 2 crystalline form is initiated. By heating the mixture 3 containing the supercooled fluid to a temperature consider-4 ably above the melting temperature of the supercooled fluid ~ 5 and agitating the mixture during the heating operation, the ; 6 melting of all crystals, even those of minute size, is 7 facilitated. This assures that the supercooled fluid will 8 remain in liquid form even after being cooled since the g minutes crystals might otherwise operate to initiate the 0 process of crystallization. Furthermore, by heating the 11 supercooled fluid at a temperature of approximately 180F., `~ ~ 12 the supercooled fluid tends to become pasteurized and thereby 13 inhibit bacterial growth.

When the temperature of the mixture has reached a 16 value such as approximately 180F. and the melting of the 17 crystals in the supercooled fluid at substantially that 18~ ~temperature has been completed, water is added at that ~l9~ temperature to~adjuYt the specific gravity to a particular 20 ; value~such as 1.595 + 0.005. ~The specific gravity of the 2~ mixture is adjusted in this manner to assure that the super-22~ cooled fluid will remain in the supercooled state after the 23 fluid has been cooled to ambient temperatures. If insuffiaient 24 water is added to the mixture to provide the particular value 25~ desired for the specific gravity, the supercooled fluid will 26 tend to become self-triggered into the crystalline state, 2~ particularly when the supercooled fluid becomes cooled.
28 Furthermore, the insufficiency of water in the mixture causes 29 the supercooled fluid in the mixture to become crystallized at a temperature of approximately 120F. instead of 118F.
31 which is normally the melting and crystallizing temperature 32 of hypo.
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11~5493 1 It has been recently found that minute crystals 2 f the hypo in the dihydrate phase normally exist in hypo 3 which has been supercooled. Such minute crystals tend to serve as nuclei in triggering the supercooled fluid into crystals at times when the triggering is not desired. This 6 causes the supercooled hypo fluid to be unstable when the 7 minute crystals of hypo dihydrate exist in the supercooled 8 hypo.

. 9 0 It has also recently been found that the minute 11 crystals of the hypo dihydrate have a melting temperature of 12 approximately 74C. (167F.). In accordance with this 13 invention, a sufficient amount of water is added to the hypo 1~ to insure that aIl of the hypo will be in the e-pentahydrate phase. It is desirable to maintain the hypo in the -pentahydrate 16 phase since the production of crystals in the -pentahydrate 17 phase causes five (5) to ten (10) times more heat ta be 18 liberated than the production of crystals in any other phase :
l9 including the dihydrate phase.

;21 As will be appreciated, only a sufficent amount ~22 of water is added to insure the maintenance of the hypo in 23 the i-pentahydrate phase If additional water is added 24 above the amount required, some additional assurance may be provided of maintaining the hypo in the ~-pentahydrate phase 26 but the hypo is diluted so th:at the heat generated by 27 crystallizing a specified amount of fluid is decreased. The 28 hypo is then heated to a temperature of at least 74C. (165F.) 29 for a sufficient period of time to melt all of the minute crystals of hypo in the dihydrate phase.

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;~5493 1 The hypo is then cooled in air to ambient 2 temperatures and the hypo is maintained in a stable state 3 at ambient temperatures until it is desired to generate 4 heat by triggering the hypo in the crystalline phase after such heat has been liberated and utilized. The hypo is 6 converted to the liquid state in the ~-pentahydrate phase 7 by heating the crystals to a temperature of at least 74C.
8 (167F.~ for a specified period of time. No water has to 9 be added if the hypo is maintained in a closed container.
0 In this way, the hypo can be recycled between the liquid li s`tate with the ~-pentahydrate phase and the crystalline state ~ 12 with the -pentahydrate phase as many times as desired without ll 13 the addition of any water.

The pH of the solution is also adjusted to a parti-16 cular value during the time that the temperature of the mixture ~, , 17 is maintained at the particular temperature such as approx- ~ `
18 imately 180F. For example, the pH of the mixture is adjusted 19~ to a value of approximately 8 to 8.5. By adjusting the pH to 20~ a value of approximately 8 to 8.5, the hypo is maintained 21~ n the~solution.~ For example, unless the pH of the hypo is 22 maintained at the specified value, the hypo may decompose 23 chemically and ~orm a colloidal suspension of sulfur. ~I~his 24, colloidal suspension of sulfur is capable of nucleating the hypo at undesired times so that the solution of hypo becomes 26 unstable. Furthermore, a pH of 8 to 8.5 inhibits recrystal-27 lization of the fluid after the temperature of the fluid has 28 returned to ambient values. The maintenance of the hypo at a 29 pH of approximately 8 to 8.5 has been obtained by adding controlled amounts of a suitable material such as sodium "
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llZ5493 ., 1 hydroxide or sodium carbonate to the mixture. The sodium 2 hydroxide may have a concentration of approximately twenty-five 3 percent (25~) with the remainder constituting water. The sodium 4 carbonate may have a similar concentration.

6 The mixture is then pumped at the elevated temperature 7 of approximately 180F. through pipes 30 made from a suitable 8 material such as stainless steel to prevent contamination of the 9 mixture. The fluid is then introduced to a storage tank 32 also lO made from a suitable material such as stainless steel to inhibit 11 the introduction of contaminants lnto the mixture. The 12 temperature of the storage tank 32 is controlled to maintain the ., 13 solution at a suitable temperature considerably above the melting 14 temperature of the supercooled fluid. For example, the }~ temperature of the storage tank may be maintained at a suitable 16 temperature of approximately 185F. + 5F.

17~
. ~, , 18~ The storage tank 32 is disposed above a packaging l9~machine 34~to Lntroduce the mixture into the packagin~ machine.

20~The packaglnq machlne introduces the fluid into the pouches 10 21~and~fills the pouches with the mixture of the supercooled fluid, 22;water~ sodium hydroxide and ethylene glycol and then seals the 23 packages. The fIuid passing through the packaging machine into 24 the pouches is mai~ntained at a suitable temperature such as 25~approximately 180F. to inhibit bacterial growth in the fluid 26 during the fillin~ and sealing of the pouches 10 and to prevent 27 the reformation of minute crystals which subse~uently serve as 28 nuclei for produclnq crystallization of the supercooled fluids at 29 undesirable times~

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~ . . .. , . ~, :, llZ5493 1 The pouches 10 are allowed to cool slowly under 2 ambient conditions to room temperature. This cooling process 3 may last for a period as long as four (4) days. One purpose 4 of this long cooling process is to provide ample opportunity to determine integrity of the seals provided on the pouch 10.
6 Another purpose is to prevent the supercooled fluid from 7 forming small nuclei for subsequently producing crystallization 8 of the supercooled fluids at undesirable times. If the pouch 9 10 is introduced into the container 16 with the triggering material 18 during the time that the mixture is above ambient li temperature, there is a tendency for the supercooled fluid 12 12 to become triggered into the crystallized state. By insuring 13 that the supercooled fluid 12 has been cooled to ambient 1~ temperature before the pouch 10 and the trigger material 18 are inserted into the container 16, any tendency for the 16 supercooled fluid to become triggered into a state of crys-17 tallization in the presence of the trigger material becomes `~
18 inhibited.

The material constituting this invention has certain 21 important advantages.~ It provides a supercooled fluid which 22 produces a substantially constant and predetexmined temperature ~3 to any temperature desired. Furthermore, the material is 24 quite stable at ambient temperatures even when the ambient temperatures are below 32F., the freezing point o~ water.
26 In this way, the supercooled fluid can be shipped through 27 long distances and can be retained in the supercooled state 28 during such long shipments so that it is ready to be used 29 to generate heat at the end of such shipments. The advantages of such material result in part from the methods used to 31 produce such materials.

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llZ5493 1 Although this application has been disclosed and 2 illustrated with reference to particular applications, the 3 principles involved are susceptible of numerous other applica-4 tions which will be apparent to persons skilled in the art.

The invention is, therefore, to be limited only as indicated 6 by the scope of the appended claims.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of producing sodium thiosulphate having properties of crystallizing in an aqueous solution in more than one crystalline phase and having superior energy-transferring properties in the pentahydrate phase and having properties of melting and crystallizing in a particular temperature range to provide the pentahydrate phase and having properties of providing a second crystalline phase with a second range of melting temperatures different from the particular temperature range, including the following steps:
heating the sodium thiosulphate to a temperature of at least 165°F. for a sufficient period of time to melt all of the crystals in the sodium thiosulphate, maintaining the pH of the fluid at a particular alkaline value, and maintaining the specific gravity of the fluid at a particular value.

2. A method as set forth in Claim 1 wherein the fluid is allowed to cool for an extended period to ambient temperatures after being heated.

3. A method set forth in Claim 2 wherein the particular pH is above approximately 8.

4. The method set forth in Claim 2 wherein the particular specific gravity is approximately 1.595.

5. The method set forth in Claim 4, including the step of:
disposing the sodium thiosulphate in a container while the sodium thiosulphate is at the elevated temperature of at least 165°F.

6. The method set forth in Claim 1 wherein the elevated temperature is approximately 180°F.

7. The method set forth in Claim 2 wherein the elevated temperature is approximately 180°F. and water is added to the sodium thiosulphate to maintain the specific gravity at a value of approximately 1.595.

8. The method set forth in Claim 2 wherein sodium hydroxide or sodium carbonate is added to the sodium thiosulphate to maintain the pH above approximately 8.

9. A method of producing sodium thiosulphate having properties of crystallizing in an aqueous solution in more than one crystalline phase and having superior energy-transferring properties in the pentahydrate phase and having properties of melting and crystallizing in a particular temperature range to provide the pentahydrate phase and having properties of providing a second crystalline phase with a second range of melting temperatures different from the particular temperature range, including the following steps:
adding to the sodium thiosulphate a chemical for lowering the melting point of the fluid and for limiting the size of the crystals in the solid state,

Claim 9 - continued heating the mixture of the sodium thiosulphate and the chemical to a temperature of at least 165°F. for a sufficient period of time to melt all of the crystals of sodium thiosulphate in the solution, adding water to the mixture to maintain the specific gravity of the mixture at a value of approximately 1.595, and adding an alkali to the mixture to maintain the mixture at a pH above approximately 8.

10. The method set forth in Claim 9, including the step of disposing the mixture in a container while the mixture is maintained at substantially the elevated temperature of at least 165°F.

11. The method set forth in Claim 9, including the step of cooling the mixture in air to ambient temperatures.

12. The method set forth in Claim 11 wherein the elevated temperature is approximately 180°F.

13. The method set forth in Claim 9 wherein sodium hydroxide or sodium carbonate is added to the mixture to maintain the pH of the mixture above a value of approximately 8.

14. The method set forth in Claim 13 wherein glycerol or ethylene glycol is the chemical added to the mixture to lower the melting temperature of the mixture and limit the size of the crystals produced from the sodium thiosulphate when the melt of sodium thiosulphate is nucleated.