| 摘要 |
A method is described for controlling the expansion properties of thermally expandable sulfuric acid-graphite particles, wherein the sulfuric acid-graphite particles, produced by the reaction of graphite particles with sulfuric acid in the presence of an oxidizing agent, are washed with an aqueous washing liquid, containing the compounds affecting the expansion properties, to a pH ranging from 2 to 8 and preferably from 3 to 7, measured in the washing liquid separated from the washed sulfuric acid-graphite particles, and then dried. Furthermore, the use of the thermally expandable sulfuric acid-graphite particles, obtainable by the method of claims 1 to 9, as intumescing fire-retarding additives for producing fire-retarding compositions especially for the fire-preventing sealing of through holes, wall bushings and other openings in walls, floors and/or ceilings of buildings, is described.
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