FLEXIBLE PHASE CHANGE MATERIAL

Abstract

The invention relates to a composition comprising 50-99 wt. % of Na.sub.2SO.sub.4.10H.sub.2O and 0.1-5.0 wt. % of an alginic acid salt. Such composition may advantageously be used as a phase change material since the composition (and a pouch comprising the composition) remains flexible during the phase change. This was also the case when subjected to a high number of subsequent cycles of heating and cooling.

Claims

1. A composition comprising 50-99 wt. % of Na.sub.2SO.sub.4.10H.sub.2O; and 0.1-5.0 wt. % of an alginic acid salt.

2. Composition according to claim 1, wherein the alginic acid salt is selected from the group of sodium alginate, potassium alginate, calcium alginate and magnesium alginate.

3. Composition according to claim 1, wherein the alginic acid salt has a molar mass in the range of 5,000-500,000 g/mol, in particular in the range of 20,000-200,000 g/mol.

4. Composition according to claim 1, further comprising 0.1-5.0 wt. % of a fatty acid salt that has a water solubility at 25° C. of 75 mg/L or less, in particular a water solubility at 25° C. that is in the range of 1-50 mg/L.

5. Composition according to claim 1, wherein the fatty acid salt is a divalent metal dicarboxylate of the formula M(C.sub.xH.sub.2x+1+COO).sub.2, wherein x is in the range of 9-29.

6. Composition according to claim 5, wherein the divalent metal is selected from the group of magnesium, calcium, manganese, zinc, tin and lead.

7. Composition according to claim 4, wherein the fatty acid salt is selected from the group of magnesium caprylate, magnesium caprate, magnesium laurate, magnesium myristate, magnesium palmitate, magnesium stearate, magnesium arachidate, magnesium behenate and magnesium lignocerate.

8. Composition according to claim 1, further comprising 0.5-4.0 wt. % of borax.

9. Composition according to claim 1, further comprising 0.5-4.0 wt. % of sodium carboxymethyl cellulose.

10. Composition according to claim 1, further comprising 0.15-15.0 wt. % of NaCl.

11. Composition according to claim 1, further comprising 0.1-5.0 wt. % of water.

12. Container comprising a composition according to claim 1, wherein the container is impermeable to water.

13. Cooling garment comprising a composition according to claim 1, in particular comprising a container-.

14. Method for cooling a body or an object, comprising the use of a container according to claim 12 or a cooling garment.

Description

EXAMPLE

[0036] The following composition was prepared and put into a pouch of aluminum foil that was sealed afterwards to yield a water-tight container:

[0037] 85.9 wt. % of Na.sub.2SO.sub.4.10H.sub.2O

[0038] 1.6 wt. % of sodium carboxymethyl cellulose

[0039] 1.6% wt. % of borax

[0040] 2.1 wt. % of water

[0041] 8.3 wt. % of sodium chloride

[0042] 0.5% wt. % of sodium alginate

[0043] The pouch was warmed in a water bath of 50° C. and left at that temperature during 15 minutes. The pouch was then flexible and could easily be deformed manually. Thereafter, it was allowed to cool down to 5° C. in a refrigerator and left at that temperature during 15 minutes. The pouch was still flexible and no solid particles could be felt in the pouch. The only difference with the warm pouch was the ductility: the warm pouch was easier to deform than the cold pouch. Such warming and cooling sequence is regarded as one heating cycle.

[0044] The pouch was subjected to 420 heating cycles and weighed before and after each cycle. It appeared that the weight of the pouch had not changed over time, and that the pouch had the same flexibility after each cycle.

[0045] Monitoring of the temperature during the cycles demonstrated that a phase change occurred at 24° C.