being quilled are treated with an antifriction agent preferably silicone fluid or if desired are cut into staple fibres the graphite is preferably used as a mixture of powdered graphite and natural graphite the departing material for producing the dispersion is a commercial 20 to 70 by weight polytetrafluorethylene dispersion in water containing an emulsifying agent graphite powder is introduced into this dispersion and a small amount of a binder or an additional emulsifying agent respectively can be added thereto until the desired viscosity is achieved which can be 50 to 1 000 cp preferably between 100 and 200 cp this viscosity is considerably higher than the viscosity of commercial polytetrafluorethylene dispersions whose viscosity number is about 10 to 12 cp by adjusting this high viscosity it is possible to keep the portion of solids in the envelope within very wide limits and to keep the envelope 39 s content of the heat conductible pigment very high as was mentioned before the binder used and the added emulsifying agent can be made up on the basis of reaction products of octylphenol and ethylenoxide for instance of the formula c 8 h 17 c 6 h 4 och 2 ch 2 n oh it is sold under the label 34 triton x 155 34 in order to increase the antifriction properties of the threads advantageously 2 to 40 by weight preferably 15 by weight of silicone fluid based on the total weight of the threads can be used thus facilitating quilling the threads according to the invention and the method for producing the same shall now be described in more detail by way of the following examples 4 20 kg of powdered graphite with a powder density of 375 g l and 0 21 kg.