Flexible, high purity expanded graphite sheet, method of producing same, and carbon crucible lining using said sheet

Abstract

The invention provides a flexible, highly pure expanded graphite sheet characterized by having an impurity content of 10 ppm or less and such a degree of flexibility that a sample thereof, 10×100 mm in size can withstand at least 10 times of bending in flexibility test comprising repeatedly bending the sample, with a 50-g weight suspended from one end thereof, by means of bending bodies with a diameter of 6 mm.

What is claimed is:  
     
         1 . A flexible, high-purity expanded graphite sheet which has an impurity content not exceeding 10 ppm and such a degree of flexibility that a sample thereof, 10×100 mm in size, can withstand at least 10 times of bending in a flexibility test comprising repeatedly bending the sample, with a 50-g weight suspended from one end thereof, by means of bending bodies with a diameter of 6 mm.  
     
     
         2 . A flexible, high-purity expanded graphite sheet as defined in  claim 1  which has a bulk density of 0.5 to 1.3 g/cm 3 .  
     
     
         3 . A flexible, high-purity expanded graphite sheet as defined in  claim 1  or  2  which has a thickness of 0.2 to 1.0 mm.  
     
     
         4 . A method of producing flexible, high-purity expanded graphite sheets which comprises forming an expanded graphite sheet having a bulk density of 0.7 to 1.3 g/cm 3  into a desired shape and then subjecting the shaped sheet to treatment for attaining high purity.  
     
     
         5 . A method of producing flexible, high-purity expanded graphite sheets which comprises forming a plurality of expanded graphite sheets each having a bulk density of 0.7 to 1.3 g/cm 3  into one and the same desired shape simultaneously in a laminate form, followed by treatment for attaining high purity.  
     
     
         6 . A method of producing flexible, high-purity expanded graphite sheets as defined in  claim 4  or  5 , wherein the shaping of expanded graphite sheets is carried out by at least one method selected from among such methods as working on a slitting machine, punching using a Thomson die, water jet working, and laser working.  
     
     
         7 . A carbon crucible liner comprising a flexible, high-pity expanded graphite sheet as defined any one of  claims 1  to  3 .