Abstract According to the method of this invention, heat-resistant fibers and flame-retardant fibers are produced from organic fibers by heating the said organic fibers to a temperature between 180*C and 350*C in an atmosphere containing oxygen gas in a concentration of at least 25%, in a high oxygen content atmosphere containing acid vapor, or in a high oxygen content atmosphere and then in an acid-vapor containing, high-oxygen content atmosphere. Furthermore, the heat-resistant fibers having higher heat-resistant property (carbon and graphite fibers) are produced by heating the said flame-retardant fibers to a temperature between 350*C and 3,000*C in a non-oxidizing atmosphere or in vacuum. In accordance with the method of this invention, the duration of the entire operation of heat treatment for producing the said heat resistant fibers can be shortened to a great extent while the said-heat treatment procedure enables the heat-resistant fibers produced to have quality favorably comparable with that of the heat-resistant fibers obtainable by the conventional method.
IN A METHOD FOR THE MANUFACTURE OF HEAT-RESISTANT FIBERS BY FIRST HEATING IN AN ATMOSPHERE AT 180*C TO 350*C AND THEN IN A NONOXIDIZING ATMOSPHERE AT A TEMPERATURE UP TO 3,000*C AN ORGANIC FIBER SELECTED ROM THE GROUP CONSISTING OF ACRYLIC FIBER, THERMALLY DECOMPOSED POLYVINY CHLORIDE PITCH FIBER AND DEHYDRATED POLYVINYL ALCOHOL FIBER, THE IMPROVEMENT WHICH COMPRISES EFFECTING SAID FIRST HEATING IN AN ATMOSPHERE CONTAINING OXYGEN GAS AND AN ACID GAS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN CHLORIDE, HYDROGEN BROMIDE, AND PHOSPHORUS PENTACHLORIDE, THE ACID GAS CONTENT BEING IN THE RANGE OF 0.5% TO 50% BY VOLUME AND THE OXYGEN GAS CONTENT BEING IN THE RANGE OF 25% TO 99.5% BY VOLUME.
Claim 2
Dependent Claim
113 words
IN A METHOD FOR THE MANUFACTURE OF HEAT-RESISTANT FIBERS BY FIRST HEATING IN AN ATMOSPHERE AT 180*C TO 350*C AND THEN IN A NONOXIDIZING ATMOSPHERE AT A TEMPERATURE UP TO 3,000*C AN ORGANIC FIBER SELECTED ROM THE GROUP CONSISTING OF ACRYLIC FIBER, THERMALLY DECOMPOSED POLYVINY CHLORIDE PITCH FIBER AND DEHYDRATED POLYVINYL ALCOHOL FIBER, THE IMPROVEMENT WHICH COMPRISES EFFECTING SAID FIRST HEATING IN AN ATMOSPHERE CONTAINING OXYGEN GAS AND AN ACID GAS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN CHLORIDE, HYDROGEN BROMIDE, AND PHOSPHORUS PENTACHLORIDE, THE ACID GAS CONTENT BEING IN THE RANGE OF 0.5% TO 50% BY VOLUME AND THE OXYGEN GAS CONTENT BEING IN THE RANGE OF 25% TO 99.5% BY VOLUME.
Claim 3
Dependent Claim
20 words
The method of claim 1 wherein during heat-treatment, the fiber is subjected to tension up to 1 gram per denier.
Claim 4
Dependent Claim
34 words
The method of claim 1 wherein the fiber is subjected to heat treatment in an oxygen-containing atmosphere to partly preoxidize the fiber prior to said first heating in oxygen gas and acid gas atmosphere.