lapping the web subsequently stabilizing the cross lapped web carbonizing and or activating the stabilized web and then felting the resultant web the above mentioned process is capable of efficiently producing a pitch based carbon fiber felt having uniform unit weight and excellent physical properties and well suited for use in high performance thermal insulator cushioning thermal insulator filter media and adsorbent for water purification and solvent recovery etc application_number US 96187992 A description the type of pitch to be employed in the present invention is not limited to petroleum base nor coal tar base but is roughly divided into optically anisotropic type and optically isotropic type an optically anisotropic pitch is the pitch which comprises an anisotropic pitch as the principal component from which is obtained carbon fibers having high tensile strength high tensile modulus of elasticity excellent chemical resistance and excellent resistance to oxidation at elevated temperatures in view of the physical properties of the carbon fiber to be obtained a pitch having an optically anisotropic component of 70 or more is preferable on the other hand an optically isotropic pitch is rich in aqueous gas reactivity and therefore is preferably used as the raw material for activated carbon fiber the pitch based short fibers obtained by melt blow spinning system have usually a fiber diameter of 5 to 30 u03bcm and a fiber length of several centimeters to several meters the pitch fiber web to be employed in the present invention has a unit weight of desirably 15 to 100 g m 2 a unit weight thereof of less.