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.

1 . 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. 
   
   
       2 . 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. 
   
   
       3 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 1 , wherein the shaping of expanded graphite sheets is carried out by at least one method selected from the group consisting of working on a slitting machine, punching using a Thomson die, water jet working, and laser working. 
   
   
       4 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 2 , wherein the shaping of expanded graphite sheets is carried out by at least one method selected from the group consisting of working on a slitting machine, punching using a Thomson die, water jet working, and laser working. 
   
   
       5 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 1 , wherein the expanded graphite sheet before purification treatment has a thickness of 0.2 to 1.0 mm. 
   
   
       6 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 2 , wherein the expanded graphite sheet before purification treatment has a thickness of 0.2 to 1.0 mm. 
   
   
       7 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 1 , wherein the expanded graphite sheet after purification treatment has an impurity content not exceeding 10 ppm. 
   
   
       8 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 2 , wherein the expanded graphite sheet after purification treatment has an impurity content not exceeding 10 ppm. 
   
   
       9 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 5 , wherein the expanded graphite sheet after purification treatment has an impurity content not exceeding 10 ppm. 
   
   
       10 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 6 , wherein the expanded graphite sheet after purification treatment has an impurity content not exceeding 10 ppm. 
   
   
       11 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 5 , wherein the thickness is 0.3 to 0.9 mm. 
   
   
       12 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 6 , wherein the thickness is 0.3 to 0.9 mm. 
   
   
       13 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 5 , wherein the thickness is 0.5 to 0.8 mm. 
   
   
       14 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 6 , wherein the thickness is 0.5 to 0.8 mm. 
   
   
       15 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 1 , wherein the bulk density is 0.8 to 1.3 g/cm 3 . 
   
   
       16 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 2 , wherein the bulk density is 0.8 to 1.3 g/cm 3 . 
   
   
       17 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 1 , wherein the bulk density is 0.9 to 1.3 g/cm 3 . 
   
   
       18 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 2 , wherein the bulk density is 0.9 to 1.3 g/cm 3 . 
   
   
       19 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 1 , wherein said purification treatment comprises heating the sheet at 2,000° C. or above in a halogen atmosphere. 
   
   
       20 . The method of producing flexible, high-purity expanded graphite sheets as defined in  claim 2 , wherein said purification treatment comprises heating the sheet at 2,000° C. or above in a halogen atmosphere.