SILICON OXIDE FIBER AND ITS PRODUCTION

PURPOSE:To obtain the titled flame-proofing fiber having excellent heat-resistance in oxidative atmosphere, by placing an infusibilized pitch fiber, etc. in an atmosphere maintained at a specific temperature and containing the decomposition product of an organic silicon compound to effect the deposition of the decomposition product to the surface of the fiber, and introducing the fiber into a gaseous atmosphere containing oxygen gas. CONSTITUTION:A ceramic boat 5 containing infusibilized pitch fiber or carbon fiber 7 is placed in the heating furnace 3. Separately, an organic silicon compound 11 is put into another boat 9. The fiber 7 is heated at 600-1,200 deg.C, preferably 700-900 deg.C while introducing an inert gas such as N2 gas throuth the pipe 13 into the heating furnace 3 to effect the decomposition of the above compound 11. After the deposition of the decomposition product to the surface of the fiber 7, an oxygen-containing gas such as air is introduced through the pipe 15 into the furnace 3 to convert the deposited decomposition product to silicon oxide and obtain the objective fiber composed of plural monofilaments of silicon oxide having fineness of 0.2-4mu and bundled with each other around the fiber axis.