GB2033566A - A cooling pack and a process for its production - Google Patents

Abstract

A cooling pack the operation of which is based on an endothermic chemical reaction and a process for its production. The pack comprises two hermetically sealed compartments one of which contains a substance (5) which is endothermically soluble in water such as ammonium nitrate and the second of which contains a substance (9) which is endothermically soluble in water such as decahydrated soda crystals and a saturated aqueous solution thereof (10). On breaking the hermetic seal (6) between the two compartments the contents thereof are mixed and react endothermically to produce a cooling effect. <IMAGE>

Description

SPECIFICATION A cooling pack and a process for its production The present invention relates to a cooling pack, the operation of which is based on a chemical reaction and which preferably comprises two hermetically sealed conpartment, the first of which contains a first substance with is endothermically soluble in water and the second of which contains a second substance which is endothermically soluble in water.

The invention also covers a process for the production of the cooling pack which is described above.

Many different chemical packs are already known which are used to obtain a cooling effect at a required moment. Normally, such so-called cooling packs involve two hermetically sealed compartments. One contains for example ammonium nitrate NH4NO3, which dissolves in water endothermically, that is, by absorbing heat. Usually, a substance which contains a large amount of water of crystallization, for example, soda crystals Na2CO3-1 0H2O, is introduced into the other compartment, while water is contained in a separate pouch. The compartments are separated from each other by a hermetically sealed intermediate seam. When the pack is about to be used, the intermediate seam and the water pouch are opened so that the substances in the pack can be mixed together.

The substances then dissolve in the water absorbing heat and the temperature of the pack falls by several degrees. An example of a cooling pack of this kind is given in the Finnish Patent Application No.

1191/72 amongst others. The presence of water is not essential because of the presence of the water of crystallization of the second component, but the cooling effect is then not quite so effective.

In the known cooling packs, the chemical which provides water of crystalization used mostly consists of soda crystals Na2CO3-10H2O. This is due in particular on the fact that soda crystals when compared with other corresponding substances, are good value and have a relatively high cooling effect.

However, the above mentioned substance also has undesirable characteristics, when it used in the known cooling pack.

It is known that in the soda crystals Na2HC3O 1 0H2O, when they are warmed to a temperature above + 32"C, the dekahydrate begins to decompose to a heptahydrate and when the temperature rises also begins to decompose to a monohydrate. The water which is thus released forms a solution composed of the heptahydrate and the monohy drate. At the relevant temperature, approximately 31.2% of Na2CO3 dissolves in water. When the temperature of the solution falls again, the sodium carbonate again crystallises into dekahydrate according to the law of equilibrium. However, according to the same law, a part of the original water of crystallization remains as a saturated mother liquor.As a part of the water crystallization remains as free water, lower hydrates also arise and the content of the dekahydrate in the pack remains lower than its original content, in this way, portion of the original effect of the pack is irrevocably lost.

In practice, the phenomenon described above is particularly unpleasant when work is being done in tropical and sub-tropical climates, where the day temperatures easily exceed the mentioned +32"C even in the shade. For the functioning of the cooling pack, the decrease in the content of the dekahydrate means a reduction in its effectiveness.

The soda crystals necessary for the known cooling pack can hardly be obtained for technical purposes, at least not at a moderate price. If one wants to produce a pack in large quantities, then it is practically essential to set up a special soda crystal installation. In principle, soda crystals can be produced by a very simple process.

By mixing water and anhydrous soda in suitable proportions, the soda can be dissolved in the water.

The solution takes place exothermically, that is, by giving off heat. The temperature of the mixture thus climbs a little, in general a few ten degrees. Crystallization takes place with the cooling of the solution.

The content of the soda crystals depend on the temperature of the solution. In the process on an industrial scale, the temperature falls slowly because of the exothermic nature of the crystallization and can even last several days. The fall of temperature can be accelerated by artifical cooling. However, the solution is never totally converted into crystals, but rather saturated water, that is, mother liquor always remains. The mother liquor can be utilized a few times in the process, but must then be drained off as waste in a discharge channel. Thus, during the production of soda crystals, unpleasant fluid wastes are formed.

Thus, the formation of the soda crystals installation mentioned above requires rather large investments in the establishment phase. Moreover, it can be established that, although the production process of soda crystals is in principal very easy, the process can meet with unpleasant difficulties which are predominantly associated with the functions of the conveyor and measuring out of the finished soda crystals. This is based particularly on the fact that the crystals shatter very easily under pressure anmd the mother liquor which has been bound between the crystals, is thereby released. From this results a heterogenous mass, the conveyance of which e.g.

with a spiral conveyor can sometimes be extremely difficult. This it is very difficult to completely automate the production process, and the operation of the installation requires operating and controlling staff, to be constantly present.

With the cooling pack according to the present invention, the disadvantages described above in relation to the known packs are avoided.

According to the present invention, there is provided a cooling pack comprising at leasttwo hermetically sealed compartments namely, a first compartment containing a first substance which is endothermically soluble in water, and a second compartment containing a second substance which is endothermically soluble in water both in solid form and in the form of a saturated aqueous solution in an equilibrium concentration.

According to a further aspect of this invention, there is also provided a process for the production of the above mentioned cooling pack, wherein the first compartment of the pack is filled with the first substance which is endothermicallty soluble in water and the compartment is hermetically sealed, and the second compartment is filled with the second substance which is anlydrous and with water in such proportion that a state of equilibrium results after crystallization, in which, apart from the saturated aqueous solution the second compartment contains substantially only crystals having a maximum content of water of crystallization.

An important advantage of the present invention is that a soda crystal installation is not needed. This fact represents a very large saving with regards to investment.

One saves on production space, working capital as well as on the number of the operating staff. At the same time, one is also spared the difficult management, measurement of the finished soda crystals.

Then a preliminary storage and trucks or a conveyor are not necessary.

By consideration of the total production process of the cooling pack, the exemption of the soda crystal installation also means that the limited capacity of a soda crystal installation does not restrict the total production capacity. A soda crystal instalation can naturally only be planned for an approximated average production. Thus, a rapid increase in production, to follow corresponding peaks in demand, is not possible. The crystallization of the soda crystals is always a function of temperature and with production in large quantities, the temperature falls only slowly. With regard to this rate of production, cooling is a critical factor. When one is freed from the limitations of soda crystal installations, extra shifts can easily be arranged for the remaining production.

An important advantage is obtained with this invention in that a special machine for packing the water pouch and a metering machine are not necessary. Thus the whole production process is simplified, which also means improvement in the functional dependability.

if the process according to the invention is com pared with the know processes for the production of a cooling pouch, then it can moreover be established that the precision in measuring out the soda crystals by the process according to the invention, in which they are measured out in fluid form, is clearly greater than with the known methods. It is also to be stated that the consumption of the pack, materials is smaller with the process according to the invention.

A special water pouch is now no longer necessary and further soda crystals in fluid form do not take up so much space as granular soda crystals plus the water pouch in the known packs. Forthe production of the pack itself, less material is needed than for the known cooling pack.

In comparison with the known cooling packs, the cooling packs, according to the inventions is a considerably and decisively different. The cooling pouch produced according to the invention, which therefore contains the mother liquor present at the crystallization reaction, adheres to the law of equilibrium under in all circumstances. Consequently, in the pack there exists only soda crystals (Na2CO 3-10H2O) and water in ratio defined by the law of equilibrium. In other words, other hydrates cannot arise. In the known packs however, a rise in the temperature to above +32"C causes a part of the releasable water, of crystallization to be left over, in the form of free water in the cooling of the pack and by this, a decrease in the proportion of the dekahydrate results.In the packing according to the invention, a 100 - percent crystallization is obtained. This is an extremely important advantage when one is working in a hot climate where the temperature of the packing can rise to above +32"C.

In addition, the absence of a special water pouch has many advantages. The cooling pack produced by the process according to the invention is very much easier for the user because he does not need to break open a particular water pouch in the pack.

Also, this is a measure which requires so much strength that the use of the known cooling packs can be at least difficult or unpleasant for a woman.

The absence of the water pouch also means more freedom in moulding the pack. Because one no longer needs to worry about breaking open the water pouch in side the pack, the pack itself can be moulded in a much more liberal fashion. The dimensions and the form of the pack are then also much easier to alter. The cooling pack produced by the process according to the invention can be used in a much more versatile way than the known chemical cooling packs. As a result of the relatively large masses of the pack according to the invention, the cooling effect by the pack in use be significantly increased.

The present invention will be described in more detail in the following with reference to the accompanying drawings, in which: Figure 1 shows an embodiment of the invention.

Figure 2 shows a second embodiment of the invention.

Figure 3 schematically show a process according to the invention.

According to Figure 1, the cooling pack of the invention comprises a cover 1, of, for example, synthetic laminate. The cover can, for example, be produced by a deep-drawing process. The laminate is preferably composed of a material which is weldable on one side, on which a lid 2 which forms the other side of the pack can be fastened by a welding groove 3,4. The welding groove 3,4 thus surrounds the whole pack and forms a hermetically sealed chamber into one end of this chamber, a solution 5 which is endothermically soluble in water is sealed and which preferably consists of ammonium nitrate. The compartment filled with ammonium nitrate is separated by an intermediate seam 6 from another compartment. The intermediate seam 6 has a construction which is known per se and consists of a closure member 7 which is nearly circular in cross section and of a part 8 which is inserted therein and has the shape of a rod. The walls of the pack surround the rod 8, where the closure member presses them together. By this means the groove is hermetically sealed.

The chamber at the other end of the pack contains a second substance 9 which is endothermically soluble in water. In this case, soda crystals and a saturated aqueous solution thereof which are in equilibrium with each other are used. A substantial part of the water required for the solution of the substances is bound in the form of the water of crystallization in the soda crystals.

Figure 2, represents an embodiment of a pack of the invention, which consists of a single synthetic web 21. It is first reshaped into a flexible tube by a welding seam which is arranged in the longitudional direction. After this, the flexible tube is provided with a welding seam 23 which runs transversely. One end of the pack contains the same chemical substance as described in the previous embodiment e.g. ammonium nitrate 25. After this, the first conpartment is sealed by a welding seam 26. This intermediate seam is weak in comparison with the other seams of the packing so that, for example, by pressing heavily on the pack, it can be broken open. The production of a weakened welding seam of this kind is already known per se and therefore does not come within the scope of the present invention.

Soda crystals 29 and a saturated aqueous solution of the same are introduced into the second compartment of the pack, after which, the pack is sealed by welding a seam 24.

Figure 3 is a schematic presentation of an embodiment of a method of producing the cooling pack according to the present invention. The pack material which consists of a synthetic material which is easily welded and is known per se is carried in the form of a continuous web from a roller 31. The pack material preferably consists of, for example, polyethylene. As a pack material, a many layered laminate can advantageously also be used, wherein only inner most layer consists of a weldable material. In the present embodiment, the pack material 32 is carried from a roller in the form of a simple web, and this is continuously provided with a seam along its length, so that a flexible tube having the width of the pack results. The seam which is formed in the longitudinal direction is produced between welding jaws 33 and 34.The end seam which runs transversely across the pack is produced between the jaws 35 and 36. After this, the required amount of NH4NO3 is measured out through a pipe 37 onto the base of the pack. In between this, a metering device of construction known per se is arranged but cannot be seen from the schematic diagram. If the total weight of the cooling pack amounts to for example, 800 g which is advantageous with regard to use, 270 g ammonium nitrate is introduced into the pack.

Afterwards, the pack is provided with an intermediate seam. The intermediate seam can in principal be formed by various processes. In this embodiment of the invention, a mechanical intermediate seam is used which is preferably of the same type as the same which is disclosed in the Finnish Patent No.

53275. If required, the intermediate seam can also be formed by welding wherein care has to be taken that the intermediate seam can be broken open between the compartment. The preformance of this operation is known per se and for this reason no further explanation is given in this connection.

After the intermediate seam has been formed, water and an hydros soda Na2CO3 is introduced into the second compartment of the pack. In the present example, where a pack is to be produced with a total weight of 800 g, the water which is required amounts to 170 g and the anhydrous soda amounts to 360 g in this embodiment, the water is kept in a special container 30. The anhydrous soda is likewise kept in a special container 41. Both the water and the soda are measured into a mixing container 42 in a ratio which corresponds to the above mentioned quantities by weight. Mixing the water and the an hydros soda together produces the soda in water solution.

During the solution, heat is given off. This is useful for the process, because at a higher temperature, the soda crystal is completely dissolved in the water and crystallization results in the known way only after the temperature has fallen. From the mixing container, the warm mixture of water and soda is introduced through a pipe 43 into the second compartment of the pack. This pipe naturally also has a metering device which is known per se but which is not shown in the diagram and is not described in more detail since per se it comes outside the scope of the invention.

Another advantageous effect is obtained if in addition to the water and soda, small amounts of additives e.g. up to 5%, which contribute to the crystallization of the resulting soda crystals take part in the reaction. If mainly water and soda are mixed together, the resulting soda crystal usually has the form of a rather hard clump and it can make the use of the pack difficult. If for example 0.9 to 1.0% of silicon dioxide is added to the solution described above, the soda crystal crystallizes in the form of a soft crystal mass which is jelly-like or at least can be reduced to small pieces using ones hand. The mentioned oxide can be obtained under the Trade name of CAD-O-SIL.

After measuring the mixture of water and soda, the packing is sealed off by a welding seam which runs transversely between the jaws 35 and 36.

Finally the pack is separated with a trimming blade 44,45. The separated packfalls onto a conveyor 46 and is further carried into a dispatch carton 47 and to a loading area and a warehouse or directly to a delivery truck. It should be noted that the cooling pack which is thereby produced is not as such ready for use. Immediately after packing, the pouch usually has a temperature of approximately 40 to 50"C. After cooling the pack, the crystallization of the soda crystals begins. The cooling effect on the pack is known to be dependent on the degree of crystallization of the soda crystals and the pack is therefore ready for use after crystallization. In practice, this requires several days. In the meantime, the packs can be used for heating the storage rooms. If required, they can also be used for heating the loading room of the vehicles.

When the crystallization is finished, the cooling pack can be used. One end of the pack contains granular ammonium nitrate and the other compartment which is separated by the intermediate seam contains soda crystals mixed with the mother liquor.

When the intermediate seam is broken open, the two substances mix together and after this there follows a chemicaly endothermic reaction which causes the temperature of the pouch and of its immediate surroundings to sink even as far as to about - 1 50C.

The process of the present invention has been described above only with reference to a particularly advantageous embodiment of the same. There is no intention here to restrict the invention in any way, there being many other processes and materials which can also be used in the prodution of the above mentioned cooling packs. It should in particular be observed that the production of such cooling packs comes within the scope of protection, the different compartments of the cooling pack are kept completely separate from each other during the production process and even during storage and are not brought into contact with each other until the moment when the cooling pack is to be used so that the substances which are contained therein can combine together.

In this connection, the installation of one compart mentofthe pack within the other can also be considered, preferably the compartment containing the Na2CO3- solution is placed inside the larger pouch with ammonium nitrate in order to ensure an easier puncturing.

Claims (10)

1. A cooling pack comprising at least two hermetically sealed compartments namely, a first compartment containing a first substance which is endothermically soluble in water, and a second compartment containing a second substance which is endothermically soluble in water both in solid form and in the form of a saturated aqueous solution in an equilibrium concentration.

2. A cooling pack according to claim 1,wherein the first compartment contains ammonium nitrate NH4NO3, and the second compartment contains decahydrated soda crystals Na2CO3-10H2O and a saturated aqueous solution thereof in an equilibrium concentration.

3. A cooling pack substantially as herein described with reference to Figure 1 or 2 with or without reference to Figure 3 of the accompanying drawings.

4. A process for the production of a cooling pack according to claim 1, wherein the first compartment of the pack is filled with the first substance which is endothermically soluble in water and the compartment is hermetically sealed, and the second compartment is filled with the second substance which is anhydrous and with water in such proportion that a state of equilibrium results after crystallization, in which apart from the saturated aqueous solution the second compartment contains substantially only crystals having a maximum content of water of crystallization.

5. A process according to claim 4, wherein the water and the an hydros substance which are to be introduced to the second compartment of the pack are mixed together before being introduced.

6. A process according to claim 5, wherein the aqueous solution and the second substance are introduced into the second compartment at a temperature such that the substance is in a completely dissolved form and the crystallization of the solid substance only takes place in the interior of the pack after the temperature has fallen.

7. A process according to any one of claims 4 to 6, wherein small quantities, of an additive are introduced to the second compartment to prevent clumping of the resulting soda crystals.

8. A process according to claim 7 wherein the additive is introduced in to the second compartment in a quantity of up to 5% of the total weight of the solution therein.

9. A process according to claim 8, wherein the additive comprises silicone dioxide in a quantity of 0.9 to 1.0% of the total weight of the solution.

10. A process for the production of a cooling pack according to any one of claims 1 to 3 with reference to Figure 3 of the accompanying drawings.