Gel composition comprising a phase change material
The present invention provides a composition comprising a) a phase change material; b) 1 to 10 wt % of a silica gelling additive; and c) a styrene co-polymer gelling additive; wherein the composition is in the form of a gel and wherein the weight ratio of b) silica gelling additive to c) styrene co-polymer gelling additive in the composition is in the range from 0.6 to 5:1. The invention also provides a method of making the composition and an article and a product comprising the composition. Finally, the invention provides the use of a combination of a silica gelling additive and a styrene co-polymer gelling additive to make a gel composition comprising a phase change material with one or more improved properties.
1. A composition comprising:
a) a phase change material;
b) 1 to 10 wt % of a silica gelling additive;
c) a styrene co-polymer gelling additive;
wherein the composition is in a gel form and wherein a weight ratio of b) silica gelling additive to c) styrene co-polymer gelling additive in the composition is in a range of from 0.6 to 5:1; and
d) 0.05 to 10 wt % of a diol, wherein the diol is a polyethylene glycol.
2. A composition according to of claim 1 wherein the phase change material is a fatty acid, a fatty alcohol, a fatty amine, a fatty acid ester, a fatty alcohol ester, a fatty acid amide, or mixture thereof.
3. The composition of claim 1 wherein the phase change material comprises an ester.
4. The composition of claim 1 , wherein the composition comprises at least 60 wt % of phase change material.
5. The composition of claim 1 , wherein the silica gelling additive is a fumed silica.
6. The composition of claim 1 , wherein the styrene co-polymer gelling additive is a styrene-(ethylene-propylene)-styrene (SEPS) tri-block co-polymer, a styrene-(ethylene-butylene)-styrene (SEBS) tri-block co-polymer, or a mixture thereof.
7. The composition of claim 1 , further comprising a nucleating agent, wherein the nucleating agent has a melting point at least 15° C. higher than that of the phase change material.
8. The composition of claim 1 , where the composition exhibits a flow at rest (FAR) period at 25° C. of at least 30 minutes, wherein the flow at rest period is defined as a time needed for 85 wt % of a sample of the composition to flow out of a conical funnel through a lower circular aperture, when the sample is placed into the conical funnel, the conical funnel being defined by a circular lower outlet aperture having a 0.9 cm diameter, a circular upper inlet aperture of 6.8 cm diameter, and a height of 5 cm.
9. The composition of claim 1 , wherein the composition is a shear thinning gel composition.
10. The composition of claim 9 , wherein the composition exhibits a shear thinning value (STV) at 25° C. of at least 20, wherein the shear thinning value (STV) is defined as:
STV=viscosity at 0.2s −1 /viscosity at 59s −1
and the viscosities at 0.2 s −1 and at 59 s −1 are measured at 25° C. on a rheometer with a 40 mm stainless steel parallel plate geometry.
11. An article comprising a sealed container containing the composition of claim 1 .
12. The article of claim 11 wherein the sealed container is a pouch or panel.
13. A product comprising the composition of claim 1 , wherein the product is a textile product, a foam product, a medical product, an electronic product, a packaging product, an automotive system, a refrigeration system, an HVAC system, or a construction material.
14. A method of making a composition of claim 1 , the method comprising:
i) mixing the phase change material, the silica gelling additive, and the styrene co-polymer gelling additive at a sufficient temperature and for a sufficient time to allow the styrene co-polymer gelling additive to completely dissolve in the composition; and
ii) stopping mixing to allow the composition to rest and to form a gel.