Encapsulation of phase change materials

DETAILED DESCRIPTION OF THE INVENTION As used herein all parts, percentages, ratios and proportions are on a weight basis unless otherwise stated herein or otherwise obvious herefrom to one skilled in the art.
The solid phase change material can be any suitable material that changes from the solid state to the molten state and vice versa within the desired range of usage, and that has a relatively high heat of fusion.
The melting point of salt hydrates preferably falls within the range of 30.
degree.
to 40.
degree.
C.
and of polyethylene glycols and crystalline paraffins preferably falls within the range of 60.
degree.
to 70.
degree.
C.
Typically solid phase change materials are salt hydrates, crystalline polymers, napthalene, and crystalline paraffins.
The phase change material can be crystalline polymers, such as crystalline polyvinylidene chloride), CARBOWAX.
RTM.
polyethylene glycol 8000 (preferred), and high density polyethylene.
Crystalline polymers such as high density polyethylene are primarily linear without many branches.
Even low molecular weight linear polymers are often crystalline and can be used.
Crosslinking to any degree or significant branching will prevent a polymer from being crystalline.
Semicrystalline materials which have a transition temperature range in the appropriate level can be used.
The phase change material can be the solid polyethylene glycols which are crystalline.
CARBOWAX.
RTM.
is the registered trademark of Union Carbide Corporation for a series of polyethylene glycols.
The polyethylene glycols have the general formula H(OCH.
sub.
2 CH.
sub.
2).
sub.
n OH.
An n of 76 to 80 will provide a solid material at room temperature.
The CARBOWAXs.
RTM.
are followed by numbers which correspond to their average molecular weight.
Useful crystalline CARBOWAXs.
RTM.
include: CARBOWAX.
RTM.
polyethylene glycol 3350, which has a melting point of 54.
degree.
to 58.
degree.
C.
, a heat of fusion of 37 cal.
per g and is solid at room temperature; CARBOWAX.
RTM.
polyethylene glycol 4600, which has a melting point of 57 to 61