CA1119404A

CA1119404A - Heat storage material

Info

Publication number: CA1119404A
Application number: CA000326625A
Authority: CA
Inventors: Gustaf O. Arrhenius
Original assignee: Individual
Current assignee: Allegiance Corp
Priority date: 1979-04-30
Filing date: 1979-04-30
Publication date: 1982-03-09

Abstract

Abstract of the Disclosure A liquid melt becomes converted to crystalline from at a particular temperature either spontaneously or when artificially nucleated. The liquid releases heat at crystallization. If the liquid is in a supercooled state when it begins to crystallize, its temperature will rise from the particular temperature at which it is nucleated.

Another liquid material is mixed with the liquid to be crystallized. The liquid additive has properties of forming a metastable solid together with the crystallizing material. When the liquid additive exsolves, the crystalline aggregate is weakened and is easily decomposed into fragments of small size. The liquid additive materials may include monohydric alcohols, diols and triols. The liquid additive material may be included in the liquid to be crystallized, in small amounts, amounts to two percent (2%) to five percent (5%) being typical. The amount and relative metastability of the liquid additive material in the solution contributes to control of the size of the crystals which are ultimately produced when the supercooled fluid crystallizes. A small amount of surface active material may also be included to modify the character-istics of the metastable solid solution, the exsolution process, and the texture of the exsolved crystal aggregate.

* * * * * * * * * * *

Description

L3L99LO~ , This invention relates to heat storage materials particu-larly useful for recyclable hot pads or containers for generating heat at a controlled temperature for extended periods of time. t More particularly, the invention relates to such materials in a form during the generation of heat such that heat pads contain-ing the materials can be comfortabl,y~applied to the body of a patient for an efficient transfer of heat to the patient's body.
The invention also relates to a method of forming such materials. I
As medical science becomes advanced, it is increasingly important to apply heat at control}ed temperatures to a patient for extended periods of time in order to optimize the benefic- `
ial ef~ects of such hea`t on the'`patient. For example, it is often difficult to obtain bloQd from a baby for performing tests on the ba~y, rt~has been found that blood can be withdrawn most easily from the''heel' of a ~aby, particularly when the heel ; has been heated to a particulax temperature. Since the baby 5 cannot express in any eas~ly identifiable way when the heat becomes excessive, babies sometimes become burned by the applIcation of excessive'heat.
~; 20 A,s another examplel it IS often desirable to dispose a baby on a mattress which~'ha's been heated to a particular temper-atuxe~ Th;e mattress has to be comfortable to the baby at the , same't~me that heat is being applied at the particular tempera-ture to the baby. For example, the mattress should not be lumpy or provide`sharp projections since the lumps or sharp projections affect the''c`om~Qrt qf the baby.
': 3:
`; 3 !

; ~

, .

1 Preferably the heat pads or containers should be

2 recyclable. In other words, the pads should be capable of

3 being used more than once to generate heat at -the particular temperature. In this way, the cost of the pads can be amortized over a number of uses so that the cost per use is 6 relatively low.

8 Heat pads have been provided in the prior art which meet a number of the objectives discussed above.
For example, heat pads have been provided whi~h are able 1i to operate on a recyclable basis. Such heat pads have 12 used supercooled melts which are nucleated at a particular 13 temperature to become crystallized and to generate heat as 1~ the melts crystallize. Such heat pads employing supercooled liquid melts have been recyclable since the crystalline 16 solid can be heated at the particular tempera-ture to change 17 the crystals to liquid state and the liquid state can lû then be retained in a metastable form at temperatures 19 below the particular melting temperature. ~owever, it has been difficult to provide for the material a melting 21 temperature which provides optimal results. For exarnple, 22 when the material is to be used as a hot pack for babies 23 to facilita-te the withdrawal oE blood from the babies, a 24 melting temperature of approximately 104~F. for the crystalline solid is considered as optimal. Such a 26 temperature has been difficult to obtain in a heat pack 27 having the desired metastable charac-teristics. Furthermore, 28 it has been difficult to inhibit the spontaneous crystallization 29 of the supercooled melts at low temperatures such as temperatures below 32F.

~L19~(~4 l It has also been difficult to provide the crystals with a uniformly small size. It has ~urther been difficult to provide the crystals with a size which is predetermined in accordance with the use to be made o~ the crystals. For example, crystals of one size may be desired ~or heel pads for babies and crystals of a different size may ~e desired for baby mattresses.
This invention provides a novel heat storage material which is particularly suitable for heat pads or containers and f which overcames the above difficulties. More particularly, the novel material comprises a melt having properties of crystalliz-ing into a monolithic mass when nucleated, and a liquid additive material having properties' of`occlusion in the growing crys-tals and exsolving to separate the resulting crystallites and limit their size'and of~con'trolling the' temperature of the mixture during the' time that t~e melt becomes crystallized. A container of such material can be'cantrolled to produce crystallization , . i of a liquid in the`container at any pre-selected temperature ' between the mel`ting point and the temperature o~ spontaneous nu-"~ cleation. The`crystallization can also be controlled such that ~ crystals in any desired size range can be produced. In this way, ; 20 the size of the crystallites can ~e adapted to the particu}ar ~
use that is to be made a~ the article containing the material~ L
As the~e~ crystallizes',- it liberates heat so that the tempera- ~, ture'rises from the particular temperature to a max.~mum tempera-ture, which may co.incide with,' but daes not exceed, the melting temperature. Heat pads ca~ntainillg the novel materlal are re- ¦~
cyclable'since`the`y include'liquids which become crystallized in the'part~cular temper`ature'range "to generate heat and which , ~

':
~`:

become converted back to liquid form by the subsequent applica-tion of heat a-t or above the melting temperature. The melt in the heat pads has characteristics of remaining as a liquid in ', a metastable form at temperatures below the particular melting temperature until such time as the generation of heat is again desired.
: According to a further embodiment of the invention, ~-there is provided a method of forming crystallites or crystal aggregates of a controlled s~ze and generating heat, including the steps of providing a meIt having properties of crystallizing into a monolithic aggregate when nucleated without the addition of additional materials and having a liquid additive material having properties of adsor~ing on the surface of the crystals s~
and being o~cluded.~in th.e crystals to control the size of the r crystallites ultimately produced,- mixing the melt and the liquid additive material, and nucleating crystallization of the melt i:
to form the crystallites of tHe controlled size and to generate heat~

, i 1.

- 4a -i, .,:

Preferably the liquids are supercooled and different liquid phases may be used depending upon the particular tem-perature interval in which the heat is to be generated.
The liquid additive material may be pre~erably selected from a group consisting of monohydric alcohols, diols and triols.
The liquid additive material has properties of dissolving meta-stably in the crystals an~ to exsolve so as to limit the ulti-mate size of the crystallites. The amount and chemical pro-perties of the liquid additive material in the supercooled melt contribute to control of the size of the crystallites that are produced when the supercooled fluid is nucleated to form one or several crystalline solids. Preferably, the amount of the liquid additive material in the supercooled melt for controlling the size and tex~ure of the crystallites produced from the supexcooled fluid should no~ exceed approximately two percent (2~) to five percent (5~) by weight.
~ It will be appreciated, however, that amounts of the - liquid additive material in excess of two percent (2%) to five percent (5~) may be included in the li~uid melt, particularly when it is desired to control the amount of heat generated by the melt. Under some circumstances, an amount of liquid-phase material in excess of two percent (2~) to five percent (5%) in the li~uid melt may be advantageous in controlling the ~ize and texture of the crystallites.

~1 The liquid-additive material is also advantageous in controlling the particular maximum temperature which the super-cooled melt reaches at crystalliza~ion. When the liquid additive material is used to provide such control of the melt-ing temperatuxe interval, it may exceed the preferably criterion of two percent (2~) by weight specified above, depending upon the particular temperature desired. The liquid additive material is also advantageous in inhibiting the uncontroLled - and unintended spontaneous nuclea~ion of the supercooled melt into incipi nt crystallization at low temperatures such as temperatures in the range of 0~. to 35F. Such control over such unintended nucleation into crystallization of the super-cooled melt is especially important when the heat storage material of the invenkion is used in heat pads shipped to distant destinations through winter climates with the melt in a supercooled state.
The effect of the liquid additive material in limiting ; the size of the crystals results fxom two diferent but related actions of the liquid additive material. In one action, the liquid additive material adsorbs to specific surfaces of the crystals so as to inhibit their growth. In another action, the adsorbed liquid additive material forms a metastable solid solution or dispersion in the crystals. This metastable solu-tion or dispersion subsequently exsolves to form oriented vesicular liquid inclusions, which weaken tha crystals and cause the crystals to break. The liquld inclusions also tend to cluster together and grow in size and thereby contribute to breaking up the crystals into fragmen~s. These fragments , can be given various sizes ~ .

~ - 6 . . ..

~1~9~(~4 1 in the overall range of the order oE ten (10) to one thousand 2 (1,000~ micrometers (~ m) with consistency corresponding to f,n;~ r/~/
3 that of sand or silt. If the-bea~-~R~ is gently agitated as

4 the crystals form, the achievementof this ultimate consistency

5 is accelerated.

~e~ f/~l ~ The ~a~-~a~ may also include a small amount of a 8 surface active material which is provided with properties of 9 lowering the surface tension of the crystals produced from 10 the melt such as -the supercooled melt. The surface active 11 material may be selected from a group consisting of sulfates, 12 phosphates, phosphonates and sulfonates. The surface active 13 material is preferably used when the liquid phase material 14 constitues particular ones of the liquid phase materials such 15 as monohydric alcohols.

17 When the surface active material is used, the 18 characteristics of the surface active material modify the 19 rate of absorption and occlusion of the liquid addi-tive. As a result, the texture of exsolved crystals aggregate, and the 21 crystallites, can be modifi.ed beyond the limits imposed by 22 the liquid additive. In those cases where the liquid additive 23 has a limited solubility in the melt, such as in the case of 2~ certain monohydric alcohols as liquid additives, the use oE
appropriate surface active agents contributes to the stabiliza-26 tion of the liquid additive as a colloidal suspension in the 27 melt.

29 The ability of the surface active material to affect the texture of the crystalline solid results from 1119~04 1 certain characteristics of such material. For example, the 2 surface active material characteristically consists of long-3 chain molecules with the terminal group on one end of the molecule having a high affinity for one or several of the components of the supercooled mel-t, and the other end having ~ an affinity for the liquid additive. The distribution of 7 the surface active material at the phase boundary between the 8 supercooled melt and the liquid additive phase changes the ~ ~ surface energy of the system and causes the liquid additive :: ~o to enter the supercooled melt, and the crystals forming from ll the melt, in a colloi.dal suspension. This colloidal suspension, `. 12 when occluded in the crystalline phase, is in a metas-table 13 state, and tends to coalesce into larger exsolution vesicles, 14 oriented on preferred crystallographic planes. The formation of these oriented exsolution vesicles weakens and disrupts 16 the crystals so as to form small crystallites of size and 17 shape dependent upon the combination of liquid additive material 18 and surface active material on one hand and supercooled melt l9 material on the other.

21 As will be seen from the above discussion, the use of 22 a liquid additive material alone or -the combination of a surface 23 active material and a liquid additive material in a mixture with 2~ a heat-generating material such as a supercooled melt constitutes ,..,~
one feature of this invention. This combination provides a 26 distinct advantage over such prior art as patent 3,770,390 27 issued to Teet on November 6, 1973 and patent 3,653,847 issued 28 to Abelson on April 4, 1972, since neither of these patents 29 discloses or contemplates the inclusion of additional material . 30 into a liquid such as a supercooled melt to limit the size 31 of the crystals produced from such a melt.

~32 ~ ' !
~1~9~L04 The invention will now be described further by way of example only and with reference to the accompanying drawings, wherein:
Figure 1 is a side elevational view of a hot pad when used as a baby mattress, such hot pad containing the novel material of the invention;
Figure 2 shows in an exploded perspective relationship, partially broken away, the different members included in the baby mattress of ~igure l;
Figure 3 is a sectional view of the baby mattress of Figures l and 2 and illustrates t~e relative size of the crystals produced in such a mattress when the liquid melt in the mattress crystallizes to generate heat;
Fi-~ure 4~1s a side`elevational view, partially broken ~.
away, of a heel pad appl~ed to a baby to facilitate the withdraw- i al of blood from the ~aby~ and Figure S is a perspective view, partially broken away, of the heel pad of Figure 4 whbn applied to the heel of a baby.
Cansidering, f~rs:tly, the embodiment of the invention whereih the liquid meIt has supercooled properties, it may be noted that a supercooled liquid meLt has properties of crystal~
lizing at a particular temperature to liberate heat. The L
crystallization occurs over an extended period of time, starting ¦
at th.e particular temperature and culminating at a temperature at or belo~ the melting interval of the particular phase system so that the particular range Q~ temperatures is produced for the L

_ g _ ,..................................................................... ~:
.1. t~
~ . ' .

~, .

1 extended period of time. When heat is subsequently applied 2 to the resulting solid at or above its melting temperature 3 interval, the solid returns to a liquid form and (unless nucleated) remains in the liquid form even at temperatures below the melting -temperature interval. When the supercooled

6 melt again becomes nucleated, it crystallizes again, while

7 liberating heat. In this way, the melt is able to store heat

8 until such time as it is desired to liberate the heat.
g Furthermore, the system can be recycled through a number of successive cycles to store and then liberate heat.
1i .
12 ~ number of different materials can be used to store 13 and liberate heat of crystallization. These materials are 14 hereinafter referred to as "the melt". These materials include sodium sulfate decahydrate, sodium thiosulfate pentahydrate 16 (hypo), sodium chromate decahydrate, calcium chloride hexa-17 hydrate, magnesium chloride hexahydrate, magnesium nitrate 18 hexahydrate, ureajammonium nitrate, disodium hydrogen 19 phosphate dodecahydrate, sodium acetate trihydrate and calcium nitrate trihydrate.
... .

22 A liquid additive material is included in the super-23 cooled melt. The liquid addi-tive material is preferably a 24 monohydric alcohol or a diol or a triol. When a monohydric alcohol is used, -tertiary butyl alcohol or cyclohexanol are 26 preferable. Both of these compounds, due to their molecular 27 structure, have enhanced solubility in salt hydrate melts and 28 low surface tension relative to molten salt hydrates. When a 29 diol is used, ethylene glycol or propylene glycolis preferred.

Glycerol is preferred when the liquid additive material is a 31 triol.

.

~, .

94~4 l When diols or triols are used as the liquid additive 2 material, the liquid additive material provides an optimal 3 effect at a concentration by weight of approximately two percent (2%) to Eive percent (5~) of the.supercooled melt. In this concentration range, and below it, a major fraction of the 6 liquid additive material becomes occluded in the crystals and contributes to the textural control. Below a concentration in 8 the supercooled melt of approximately two percent (2%), the textural ef~ect of the exsolution of liquid additive material ln.the crystals tends to decrease. As a result,as the con-ll centration of such liquid.additive material decreases below 12 approximatel~ two percent (2%), the size of the crystalli.tes 13 produced by exsolution of the liquid-additive material, and 14 the force needed to separate the crystallites becomes larger.
Above a concentration of approximately two percent (2%) to 16 five percent (5~) by weight or volume in the supercooled melt, 17 the liquid additive material has only a minor added effect on 18 the exsolution process compared to that provided at a con-19 centration in -the range of two percent (2~) to five percent (5%). Furthermore, the heat produced per unit volume of the 21 system decreases because the liquid additive material does ::
22 not generate any heat when the supercooled melt crystallizes ~ 23 and because the liquid additive material in concentra-tions 24 above about five percent (5%) causes the solidus temperature of the phase system to drop rapidly. In view of this, except 26 for special purposes, it is desirable to include as little as 27 possible of the liquid additive material in the supercooled 28 melt, consistent with the amount of liquid additive material 29 needed to obtain the desired textural control of the crystalline material formed from the supercooled melt.

.

- 1. 1 -1~L94()4 As ~ill be appreciated t the supercooled melt tends to crystallize into one single mass or a few large ma~ses in the heat pad if the liquid additive material is not included. The liquid additive material tends to inhibit the formation of such a large mass or such large masses. This results from the formation of adsorbed layer~ of the additive on the surface of the crystals as they are being formed. This thin film has properties which inhibit the growth of specific faces of the crystals. As a result, the crystals forced to grow ~y the strong supersaturation in the supercooled melt, overgrow the liquid additive, thereby causing liquid inclusions to foxm in the crystals. These liquid inclusions coalesce to form laminar vesicles~ intersecting segments of the crystals. The formation of the exsolution vesicles causes the crystals to crack and, at slight agitation, to fall apart into smaller crystallites.
The mechanical effect of exsolution on the texture of the crystals formed at nucleation of the supercooled melt is enhanced by gently agitating the heat pads containing the mixture of the supercooled melt and the liquid additive material. This has the efgect of accelerating the formation of cracks, releasing the stress on the crystalline material introduced by the exsolution of the liquid additive. Thus, when the material is used in a heat pad, by gently agitating the heat pad as the melt solidifies, the crystalline solid tends to have the texture of sand or silt.
The liquid additive material contributes other impor-tant advantages when included in the supercooled melt. For example, when the supercooled melt consists of sodium thio-sulfate pentahydrate, the melting temperature and hence thepeak temp-- ~194(~`~

1 erature of the crystallizing supercooled melt is approximately 2 118 F. This temperature is hi~her than that desired for many 3 applicatlons. For example, when the supercooled melt is to be 4 used in heel packs for babies, it preferably should have a melting temperature of approximately 104 Y. At this temperature, 6 the heel pack provides an optimal effec-t in insuring that blood 7 can be drawn effectively from the baby for diagnostic purposes 8 hy a heelstick. This temperature is also sufficiently low to g prevent overhea-tiny of the baby's skin.

11 The production of an optimal temperature by the 12 nucleation of the supercooled mel-t is obtained by adding a 13 material such as propylene glycol to the material from which 1~ the supercooled melt is produced. For example, when propylene glycol is added by wei~ht in an amount of approximately ten 16 percent (10~) to a supercooled melt such as sodium thiosulfate 17 pentahydrate, the solidus temperature decreases to approximately 18 10~ F. from the mel-ting point of the pure salt hydrate at I9 lla F. Furthermore, the resultant melt is able to exist in a liquid state for extended periods of time at temperatures in the 21 range down to approximately lOnF. This is lmportant in commercial 2Z shipments since crystallization of the supercooled melt would 23 otherwise occur at approximatley ~0 F during shipmen-t throuyh 24 cold climates. As will be appreciated, spontaneous crystallization of the sUperCooled melts in the heat packs duriny shipment is ~ ...... ..
26 undesirahle since it prevents the heat packs from being used at 27 the destination until the crys-tallized material has been recycled 28 by melting in the case of heat packs designed for recycling; in 29 the case of heat packs without this provision, the damage is irreversible.

-l3-~ 9~

1 In additionto the materials specified above, other ~^ 2 materials then monohydric alcohols and diols and triols may be 3 used as the liquid additive materials, particularly when surface active materials are also included in the system. For 5 example, complex amines may be used. Ilowever, such materials 6 tend to be -toxic. They also tend to diffuse through the plastic 7 laminates used as containers in current types of heat packs.
8 Certain ketones (such as methyl isobutyl ketone) and esters .r ~` 9 (such as butyl phthalate, ethyl acetate and oleic acid esters) 10 may also be used~
11 ' 12 As previously described, a surface active ma~terial may 13 be included in the melt, particularly when the liquid additive material is a monohydric alcohol or some other compound with :
15 limited solubility in the melt. The surface active material is ., 16 provided with properties of solubility both in the salt hydrate 17 melt and in -the liquid-additive material and with capability 18 for absorption on one or several crystallographic faces of the 19 salt hydrate crystals. Because of these properties, the surface- `
20 absorption material becomes fixed -to the different faces of the 21 growing crystals, thereby changing the habit of the crys-tals and 22 the configuration ratio of the exsolution vesicles forming in 23 the crystals. In this way, the shape and separation of the ,2~ ultimately forming crystal fragments, and the tex-ture of the aggregate material, can be changed at will within certain limits.
26- ~s will be seen, the size of the molecules of the surEace 27 active material and the structure of their functional groups 28 affect the growth and combination of crystal faces. In effect, 29 the growth of specific crystal faces is being inhibited by the addition of the surface-active materials. As a result, such ~: , :

~19~0~

1 faces become well developed in the crystals, while fast growing 2 faces become eliminated.

4 The molecules used as the surface active material may be formed as chains of atoms which may be chosen in different 6 lengths. For example, the surface active molecules may be formed 7 from chains of as many as twelve (12) to twenty-two (22) carbon 8 molecules. When such long chains of atoms are desired, the surface active materials may comprise alkyl sulfatest sulfonates, phos-phates or phosphonates.
li 12 The surface active material also h~s the properties 13 Of lowering the surface tension between the melt phase and the 14 liquid additive phase so that the latter can be dispersed in the melt and stabilized there as a colloidal suspension which 16 becomes occluded in the growing crystals and eventually e~solves 17 to form texture-controlling vesicles in the crystals. Preferably 18 the surface active materials have hydrophilic properties to 19 accompllsh this. When such properties are deslred, the surface active materials are preferably alkali salts of acids of the 21 desired molecular types. For éxample, sodium alkyl sulfate or 22 sulfonates may be used. Such materials are soluble in the salt 23 hyclrate melt, and ligate with the water molecules in the melt 2~ and on the surface of the salt hydrate crystals.
26 Alkyl sulfates and phosphates, inorganic phosphates 27 such as polyphosphates, organic phosphates, phosphonates and 28 sulfonates may be used as the surface active material. For 29 example, le¢ithin (an organic phosphate) and Victawet 12 (a complex organic phosphate manufactured by Victor Chemical ' .

, 5_ 1 Company) may be used.

3 In addition to being soluble in water, the surface-4 active material may be soluble in the li~uid phase m~teri~l.
For example, lecithin is soluble in pentanol or amyl alcohol 6 isomers (alcohols containing 5 carbon a-toms) or cetyl morphol-7 inium ethoxy sulfate made by ~mperial Chemical Industries and t ~7Lra~le ~narf~
~8 designated by that company as Atlas G-263.

When both are used, the surface active material and 11 the liquid additive are included in the ma-terial such as the 12 supercooled melt in suitable proportions. For example, approx~
13 imately ten (10) milliliters of the liquid additive material and 14 three (3) milligrams of the surface active material may be mixed in approximately one hundred ~100) milliliters of a melt 16 such as the material later providing the supercooled liquid to 17 provide the desired result. However, as li-ttIe as two (2) to 18 five (5) milliliters of the liquid additive material may be mixed 19 with one half (1/2) of a milligram of the surface active ma-terial in approximately one hundred (100) milliliters of a mel-t such as 21 the material later providing the supercooled liquid to obtain 22 the desired results. Such a mixture provides a minimal dilution 23 of the material to be melted and crystallized. It also tends to 2~ insure that the temperature of the melting and crystallization of the mixture corresponds substantially to the temperature of 26 melting and crystallization o~ the pure phase or phase system used 27 to produce the supercooled melt. For example, sodium thiosul-2~ fate pentahydrate mel-ts at a temperature of approximately 4~C.

29 However, this salt hydrate with small amounts of the surface active material, and with two per cent by weight of propylene I ~
. ~ .

409~

l glycol as a liquid additive material, starts -to melt at a temp-2 era-ture of approximately 47C. and melts completely at a temp-3 erature of approximately 4~.5C.

Various combinations of -the above materials provide ; 6 particularly desirable results. For example, cetyl morpholinium 7 ethoxy sulfate may be used as a liquid additive material in ; 8 combination with sodium lauryl sulfate as a surface active material g or in combination with lecithin as a surface active material;
cyclohexanol may be used as a liquid additive material in com-1l bination with sodium lauryl sulfate dissolved in propylene glycol, 12 or with Victawet ll, as a surface active ma-terial; 2-pentanol 13 may be used as a liquid additive material in combination with 14 lechithin as a surface active material; and tertiary butyl alcohol may be used as a liquid additive material in combination 16 with Victawet 12 as a surface active material.

18 The combinations disclosed above have certain important 19 advantages. They provide a crystallization of the material such as the supercooled melt as an aggregate forming small lubricated 21 particles which provide an e~ficient transfer of heat to a pa-tient 22 or other animate or inanimate object receiving the heat. This 23 results in part from the fact that the container holding the 24 crystals is pliant because of the small size and mobility of the crystallites and can accordingly be bent to any desired ` 26 shape corresponding to the shape of the object to receive the heat.
27 For e~ample, when the mixture lO is disposed in a container 12 28 to form a heel pad generally indicated at 14 (Figures 4 and 5), 29 the heel pad can be bent into a shape correspondiny to the heel of a baby so that the heat released during the crystallization of ~2 ~;

1 the material can be applied uniformly over the entire heel area 2 of the baby.

4 The mixture also has certain other advanta~es of some importance. For example, ~he mixture 20 can be disposed in a 6 baby mattress generally indicated at 22 in Figures 1, 2 and 3 q to warm a baby a-t a substantially constant temperature for an ext~-rlded perio~ of tirne aS the ~b~ liea Gn the r~,attress.
g By providing for the crystalliz.a-tion of the supercooled mel-t systems into an aggregate, formillg par-ticles of a small size, -the 11 mattress 22 is able to adapt to the contour of the baby so that the 12 baby continues to remain comfortable as heat is liberated from 13 the mattress.
:La, The size, shape and aggregation of the crystallites 1~ can be controlled by adjusting the concentration and composition 17 of the liquid additive material in the system. For example, if 18 the liquid additive material forms a relatively concentrated 19 solution in the melt, the crystallites produced are ~uite . ~ .
small in size. If the liquid additive material is low in con-21 centration, the size of the crystals becomes correspondingly 22 increased. The size of the crystals may be controlled to vary 23 from microscopic size through the size of sand particles to the 2~ size of large aggregates. Furthermore, the agitation of the -25 supercooled melt with additives after nucleation facilitates 26 -the disruption of the crystalline aggregate, leading to the 27 formation of a large number of small embryonic crystals.

29 The systems described above can be recycled through a multiple number of uses. For examplel the baby mattress 22 l described above can be provided wlth a valve 40. After the 2 supercooled melt in the mixture 20 in the mattress has been 3 produced by heatinc3 -the mixture to the liquidus temperature 4 of the systems, a nozzle 42 may be inserted into the mattress to nucleate crystallization of the supercooled melt. The 6 nozzle 42 may form a part of -the syringe 44 which contains a 7 crystalline powder of sodium thiosulfate pentahydrate. This 8 material has properties of initiating crystallization of the g melt into the same form as the nucleating crystals as disclosed and claimed in patent 3,951,127 issued to Susan l~atson and ll William Keith Watson and assigned oE record to the assignee 12 of record of this application.

1~ The baby mattress 22 is preferably disposed in a 16 cover 46, which offers certain advantages when used with the 16 mattress. The cover 46 may include an outer layer formed from a suitable material such as vinyl and an inner layer l~ formed from a suitable material such as polyurethane so that ~9 the cover prevents diffusion of any of the compounds of the system and is pliant. In this way, the sterility oE the 21 mattress 22 can be maintained at the same time as the baby 22 lying on the mattress remains comfortable. The cover 45 23 offers the further advantage that it limits the heat con-2~ ductivity and thus the temperature applied to the baby if 26 -the tempera-ture produced by the melt system is too high Eor 26 unimpeded application to the skin.

28 The following constitutes the compositions which 29 have been treated with sodium thiosul~ate pentahydrate as the supercooling material:

- 19 _ 1 IL~941~4 1 Liquid Additive Conc. Surface Active Conc. Weight la erlal Vol.% ~aterial _ Vol.~ %

3 Ethylene glycol 1 ---.. ..
2 ___ .

4 __ :. 7 " ll : 5 ___

9 " " 2 Victawet 12 0.1 ' " 2 Victàwet 12 1.0 11 Propylene glycol 1 . ___ ~`~ 12 " " ~ 2 ---. ~ ~ - ..
: 3 __ ` lg 4 ___ " 5 _ _ 16 " " 10 Victawet 12 0.1 , ~ , 17 2 Victawet 12 1.0 1~ " " 2 ~---19 Glycerol 1 ---" 2 ---23 " 2 Victawe-t 12 0.1 24 " 2 Victawet 1.~ 1.0 25 Triethylene glycol 2 ---26 1, 5 pentane diol 2 ---27 n-amyl alcohol 1.5 ---28 " ll 1.5Sodium lauryl sulfate 0.01 29 1.5 Lecithin 0.1 ~ ~' 1.5 Sodium propyl sulfonate 0.01 - ~rr~le m~
:
~ - I9a - ~

J.. ~ 0~ , 1 Li~uid Additive Conc. Surface Active Conc. Weight Material Vol.~ aterial Vol.

3 t-butyl alcohol 2 Victawet 12 1.~
4 " " 2 Sodium lauryl sulfate 0.01 " " 2 I.ecithin 0.1 6 Cyclohexanol 1.5 ---7 " 1.5 Sodium lauryl sulfate 0.01 " 1.5 Lecithin 0.1 9 " 2 Sodium propyl sulfonate 0.01

10 ' 2 Victawet 12 1.0 1i Atlas Chem Co G 263 2 ---12 2 Sodium lauryl sul~ate 0.01 13 " " " " " 2 Victawet 12 1.0 1~ ' .

17 Although this application has been disclosed and 18 illustrated with reference to particular applications, the 19 principles involved are susceptible of numerous other , applications which will he apparent to persons skilled in 21 the art. The invention is, thereore, to be limited only 22 as indicated by the scope of the appended claims.
, ~6 ... ~ "
, 32 : , .

; ~ 19b

Claims

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

1. In combination, a melt having properties of crystallizing into a monolithic mass when nucleated, and a liquid additive material, in a weight to approxi-mately ten percent (10%) by weight, having properties of occlusion in the growing crystals and exsolving to separate the resulting crystallites and limit their size and of controlling the temperature of the mixture during the time that the melt becomes crystallized.

2. The combination set forth in Claim 1 wherein the melt is a salt hydrate and the liquid additive material has properties of being dispersed throughout the salt hydrate melt.

3. The combination set forth in Claim 1 wherein the liquid additive material is selected from a group consisting of monohydric alcohols, diols and triols.

4. The combination set forth in Claim 1 wherein the liquid additive material has the properties of inhibiting the crystallization of the melt during the time that the ambient temperature is below the freezing temperature of water.

5. The combination set forth in Claim 3 wherein the melt material is selected from a group including sodium sulfate decahydrate, sodium thiosulfate pentahydrate, disodium hydrogen phosphate dodecahydrate, sodium acetate trihydrate, sodium chromate decahydrate, calcium chloride hexahydrate, magnesium chloride hexahydrate, magnesium nitrate hexahydrate, urea/ammonium nitrate, and calcium nitrate trihydrate.

6. In combination, a melt having properties of melting at a particular temperature interval and of remaining in the melted state at temperatures below the particular temperature interval and of being nucleated into a crystalline state as a monolithic aggregate at the particular temperature interval and of generating heat when nucleated into the crystalline state at the particular temperature interval, a liquid additive material having properties of being occluded in the crystals to subsequently exsolve and disrupt the crystals and prevent the crystals from growing beyond a particular size, and a surface active material having properties of reducing the surface tension of the liquid additive material on the crystalline material produced from the melt.

7. The combination set forth in Claim 6 wherein the surface active material and the liquid additive material have properties of providing for the melting and crystallization of the phase system including the supercooled melt at substantially the particular temperature.

8. The combination set forth in Claim 6 wherein the surface active material has hydrophilic properties and the liquid additive material has properties of being preferably absorbed on specific surfaces of the growing crystals and being occluded in the crystals to control the texture of the crystalline aggregate in accordance with the chemical character-istics of the surface active material in the supercooled melt.

9. The combination set forth in Claim 6 wherein the surface active material is selected from a group consisting of sulfates, phosphates, phosphonates and sulfonates, and the liquid additive material is selected from a group consisting of monohydric alcohols, diols, triols, ketones and esters.

10. The combination set forth in Claim 9 wherein the melt is selected from a group consisting of sodium sulfate decahydrate, sodium thiosulfate pentahydrate, sodium chromate decahydrate, calcium chloride hexahydrate, magnesium chloride hexahydrate, magnesium nitrate hexahydrate, sodium acetate trihydrate, disodium phosphate dodecahydrate, urea/ammonium nitrate and calcium nitrate trihydrate.

11. A method of forming crystallites or crystal aggregates of a controlled size and generating heat, including the steps of:
providing a melt having properties of crystallizing into a monolithic aggregate when nucleated without the addition of additional materials and having a liquid additive material

Claim 11 - continued having properties of absorbing on the surface of the crystals and being occluded in the crystals to control the size of the crystallites ultimately produced, mixing the melt and the liquid additive material, and nucleating crystallization of the melt to form the crystallites of the controlled size and to generate heat.

12. The method set forth in Claim 11 wherein the liquid additive material has a concentration and structural characteristics to control the size and texture of the crystallites formed when the occluded liquid additive is exsolved in the crystals.

13. The method set forth in Claim 12 wherein the phase system is heated to a temperature above the melting temperature interval to convert the crystals to the liquid state for a recycling of the system to generate additional heat.

14. In combination, a melt having properties of crystallizing into a monolithic mass when nucleated, and a liquid additive material, in a weight to approxi-mately ten percent (10%), having properties of occlusion in the growing crystals and exsolving to separate the resulting crystallites and limit their size and of controlling the temperature of the mixture of the melt and the liquid additive material during the time that the melt becomes crystallized,

Claim 14 - continued the liquid additive material being selected from a group consisting of monohydric alcohols, diols and triols.

15. The combination set forth in Claim 14 wherein the liquid additive material inhibits the crystal-lization of the melt at temperatures below the freezing temperature of water.

16. In combination, a melt having properties of crystallizing into a monolithic mass when nucleated, and a liquid additive material, to a weight of approxi-mately ten percent (10%) in the mixture, having properties of occlusion in the growing crystals and exsolving to separate the resulting crystallites and limit their size and of controlling the temperature of the mixture during the time that the melt becomes crystallized.
the liquid additive material being selected from a group consisting of monohydric alcohols, diols and triols, the melt material being selected from a group con-sisting of sodium sulfate decahydrate, sodium thiosulfate pentahydrate, disodium hydrogen phosphate dodecahydrate, sodium acetate trihydrate, sodium chromate decahydrate, calcium chloride hexahydrate, magnesium chloride hexahydrate, magnesium nitrate hexahydrate, urea/ammonium nitrate, and calcium nitrate trihydrate.

17. The combination set forth in Claim 16 wherein the liquid additive material also inhibits the formation of crystals during the time that the ambient temperture of the mixture is below the freezing temperature of water.

18. In combination, a melt having properties of melting at a particular temperature interval and of remaining in the melted state at temperatures below the particular temperature interval and of being nucleated into a crystalline state as a monolithic aggregate at the particular temperature interval and of geneating heat when nucleated into the crystalline state at the particular temperature interval, a liquid additive material having properties of being occluded in the crystals to subsequently exsolve and distrupt the crystals and prevent the crystals from growing beyond a partic-ular size, and a surface active material having properties of reducing the surface tension of the liquid additive material on the crystalline material produced from the melt, the liquid additive material being selected from a group consisting of monohydric alcohols, diols and triols.

19. The combination set forth in Claim 18, including, the surface active material being selected from a group consisting of sulfates, phosphates, phosphonates and sulfonates.

20. The combination set forth in Claim 19, including, the melt being selected from a group consisting of sodium sulfate decahydrate, sodium thiosulfate pentahydrate, disodium hydrogen phosphate dodecahydrate, sodium acetate trihydrate, sodium chromate decahydrate, calcium chloride hexahydrate, magnesium chloride hexahydrate, magnesium nitrate hexahydrate, urea/ammonium nitrate, and calcium nitrate trihydrate.

21. The combination set forth in Claim 18 wherein the liquid additive material has a concentration of approximately two percent (2%) to five percent (5%) by volume in the melt.

22. The combination set forth in Claim 20 wherein the liquid additive material has a concentration of approximately two percent (2%) to five percent (5%) by volume in the melt.

23. The combination set forth in Claim 22 wherein only very small amounts of the surface active material by weight are included in the melt.

24. The combination set forth in Claim 22 wherein the amount of the surface active material in the melt is considerably less than one percent (1%) by weight.

25. The combination set forth in Claim 24 wherein the melt constitutes hypo and propylene glycol is included in a range to approximately ten percent (10%) by weight to control the melting temperature of the melt and to enhance the ability of the melt to continue as a liquid at temperatures below the melting interval.

26. The method set forth in Claim 13 wherein the liquid additive material has a concentration in the melt of approximately two percent (2%) to five percent (5%) by volume.

27. The method set forth in Claim 13 wherein the melt is selected from a group consisting of sodium sulfate decahydrate, sodium thiosulfate pentahydrate, disodium hydrogen phosphate dodecahydrate, sodium acetate trihydrate, sodium chromate decahydrate, calcium chloride hexahydrate, magnesium chloride hexahydrate, magnesium nitrate hexahydrate, urea/ammonium nitrate, and calcium nitrate trihydrate.

28. The method set forth in Claim 27 wherein the liquid additive material has a concentration in the melt of approximately two percent (2%) to five percent (5%) by volume and wherein the mixture is agitated lightly during nucleation to facilitate the disruption of the crystalline aggregate.

29. A method of forming crystallites or crystal aggregates of a controlled size and generating heat, including the steps of:
providing a melt having properties of crystallizing into a monolithic mass when nucleated, providing a liquid additive material having properties of occlusion in the growing crystals and exsolving to separate the growing crystals and limit their size, providing a surface active material having properties of reducing the surface tension of the liquid additive material on the growing crystals, mixing the melt, the liquid additive material and the surface active material, and heating the mixture to a temperature to convert the melt to the melted state.

30. A method as set forth in Claim 29 wherein the liquid additive material is selected from a group consisting of monohydric alcohols, diols and triols.

31. A method as set forth in Claim 30 wherein the melt is selected from a group consisting of sodium sulfate decahydrate, sodium thiosulfate pentahydrate, disodium hydrogen phosphate dodecahydrate, sodium acetate trihydrate, sodium chromate decahydrate, calcium chloride hexahydrate, magnesium chloride hexahydrate, magnesium nitrate hexahydrate, urea/ammonium nitrate, and calcium nitrate trihydrate.

32. A method as set forth in Claim 30 wherein the surface active material is selected from a group consisting oE sulfates, phosphates, phosphonates and sulfonates.

33. A method as set forth in Claim 32 wherein the surface active material is selected from a group consisting of sulfates, phosphates, phosphonates and sulfonates and the liquid additi.ve material has a concentration by volume in the melt of approximately two percent (2%) to five percent (5%).

34. A method as set forth in Claim 32 wherein the surface active material has a concentration in the melt of less than one percent (1%) by weight.