The ornamental design for a heatpreservationcontainer, as shown and described.
FIG. 1 is a first perspective view of a heat preservation container showing my new design;
FIG. 2 is a second perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a back view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a right side view thereof;
FIG. 7 is a top view thereof;
FIG. 8 is a bottom view thereof; and,
FIG. 9 is an exploded view of the claimed design.
The broken lines shown in the drawings depict portions of the heat preservation container in which the design is embodied that form no part of the claimed design.