Patent ID: 8053506

Claim:
A method of producing a carbon nanofiber composite material, comprising: mixing an elastomer which includes an unsaturated bond or a group having affinity to carbon nanofibers with metal particles; and mixing the carbon nanofibers into the elastomer including the metal particles and uniformly dispersing the carbon nanofibers by a shear force at 0 to 50° C. by a method selected from the group consisting of an open-roll method with a roll distance of 0.5 mm or less, a closed kneading method, and a multi-screw extruding kneading method, wherein the composite material is in an uncrosslinked form and the composite material has a first spin-spin relaxation time (T 2 n) of 100 to 3,000 μsec, a second spin-spin relaxation time (T 2 nn) of 1,000 to 10,000 μsec or without the second spin-spin relaxation time, and a fraction (fnn) of components having the second spin-spin relaxation time is less than 0.2, as measured at 150° C. by Hahn-echo method using a pulsed NMR technique with 1 H as an observing nucleus.