High temperature, low oxidation stabilization of pitch fibers

Abstract

The present invention provides a process for thermosetting pitch fibers in reduced times, at low concentrations of oxygen and at higher temperatures than previously possible. Additionally, the present invention provides a pitch fiber which has an oxygen diffusion rate to the center of the fiber which is competitive with the rate of oxidation at the fiber's surface. Further, the present invention provides a high density pitch fiber batt which thermosets without loss of fiber structure.

We claim:  
     
         1 . A process for stabilizing a pitch artifact comprising: 
 heating said pitch artifact to an initial process temperature at least equal to the spinning temperature of said pitch artifact while exposing said pitch artifact to an oxidizing agent for a time sufficient to stabilize said pitch artifact.    
     
     
         2 . The process of  claim 1 , wherein said initial process temperature is at least 250° C.  
     
     
         3 . The process of  claim 1 , wherein said oxidizing agent is transported by an inert carrier gas and the concentration of said oxidizing agent in said carrier gas is 8% or less by volume.  
     
     
         4 . The process of  claim 1 , wherein said pitch artifact is heated for period of time ranging from about 1 to about 150 minutes.  
     
     
         5 . The process of  claim 1 , wherein said pitch artifact is heated to a temperature ranging from about 250° C. to about 500° C. in an atmosphere containing 8% or less oxygen by volume for a period of time ranging up to 150 minutes.  
     
     
         6 . A process for controlling the generation of heat during the oxidative stabilization of pitch fibers comprising: 
 heating said pitch fibers to an initial process temperature at least equal to the spinning temperature of said pitch fibers while contacting said pitch fibers with a flowing gas, said gas containing an oxidizing agent,    limiting the production of heat due to oxidation of said fibers;    continuing to heat said pitch fibers and contact said pitch fibers with said flowing gas for a period of time sufficient to stabilize said pitch fibers.    
     
     
         7 . The process of  claim 6 , wherein the generation of heat due to the oxidation of said fibers is controlled by varying the flow rate of said flowing gas and/or the concentration of said oxidizing agent in said flowing gas.  
     
     
         8 . The process of  claim 6 , wherein the flow rate of said flowing gas ranges from about 10,000 standard liters per minute per square meter to about 100,000 standard liters per minute per square meter.  
     
     
         9 . The process of  claim 6 , wherein said flowing gas is a gas which is nonreactive with said pitch fibers and said oxidizing agent is selected from the group consisting of oxygen carbon dioxide, oxides of nitrogen and sulfur and Cl 4 O 3 .  
     
     
         10 . The process of  claim 6 , wherein said flowing gas contains up to 8% oxygen by volume.  
     
     
         11 . The process of  claim 6 , wherein said pitch fibers have a softening point of at least 300° C.  
     
     
         12 . The process of  claim 6 , wherein said pitch fibers are heated to a temperature ranging from about 250° to about 500° C. for a period of time ranging from about 1 minutes to about 150 minutes.  
     
     
         13 . A carbonaceous pitch fiber which stabilizes to the center when placed in an oxidizing environment at a temperature of at least 300° C. but below the instantaneous softening point of said fiber.  
     
     
         14 . A pitch fiber which thermosets without melting when heated to a temperature equal to or greater than said fiber's spinning temperature in the presence of an atmosphere containing 8% or less oxidizing agent by volume.  
     
     
         15 . The pitch fiber of  claim 14  wherein said fiber thermosets in less than 30 minutes.  
     
     
         16 . The pitch fiber of  claim 14  wherein said fiber thermosets in less than 10 minutes.  
     
     
         17 . A pitch fiber which thermosets in less than 10 minutes.  
     
     
         18 . A pitch fiber batt having density of at least 900g/m 2 , said pitch fiber batt thermosets when heated in a flowing gas stream containing an oxidizing agent.  
     
     
         19 . The pitch fiber batt of  claim 18 , wherein said oxidizing agent comprises 8% or less by volume of said flowing gas stream.  
     
     
         20 . The pitch fiber batt of  claim 19 , wherein said flowing stream of gas has a flow rate ranging from about 10,000 to about 100,000 standard liters/min/meter squared.