To produce a packing which retains a high sealing capability in long- term use at 400°C or higher in a valve by incorporating a phosphorus-. boron-, or iron oxide-base flame retardant into an expanded graphite-base packing.

Expanded graphite alone or its composite with metal wires is used to prepare the expanded graphite-base packing. The phosphorus-base flame retardant used is ammonium phosphate, etc.; the boron-base flame reatardant used, sodium borate, etc.; and the iron oxide-base flame retardant used, tiiron tetraoxide, etc. The flame retardant is used in an amt. of 0.1-10wt.%. For example, a packing obtd. by cutting an expanded graphite sheet (with a thickness of 0.38mm and a density of 1.0g/cm3) into a tape with a width of 16mm, winding the tape spirally, and press molding the wound tape with a crank press is immersed in a 5% aq. ammonium phosphate soln. and is dried at 100°C to give a ring packing (with an inner diameter of 26mm, an outer diameter of 42mm, and a height of 8mm) impregnated with 0.8wt.% (based on the graphite wt.) ammonium phosphate.