Hoechst Aktiengesellschaft

Hans Peter Beu

Franz-Josef Dany

Joachim Kandler

Joachim Wortmann

Antistatic properties are imparted to rubber by admixing it with conductive carbon black, vulcanizing the resulting blend and forming the rubber. More specifically, the rubber is admixed with about 5 to 40 weight % of conductive carbon black which has an AS-number of 15 to 35, a specific electric resistance of 10.sup.-1 up to 10.sup.-3 ohms .times. cm under a moulding pressure of 100 to 180 atmospheres absolute, a bulk density of 100 to 180 g/liter, a BET-surface area of 100 to 1000 m.sup.2 /g. The carbon black is made by a process wherein an aqueous suspension of carbon black with an AS-number higher than 15 and prepared by subjecting hydrocarbons, which are liquid at room temperature, to thermal conversion at 1200.degree. to 2000.degree. C, under pressures within the range 1 and 80 atmospheres absolute, and in the presence of oxygen or an oxygen-containing gas, and water scrubbing the resulting carbon-black-containing reaction gas, is intimately blended at 5.degree. to 120.degree. C, under pressures of 1 to 20 atmospheres absolute, in liquid phase at a pH-value of 7 to 10, and for 1 to 20 minutes, with vaporizable liquid aliphatic or cycloaliphatic hydrocarbons, the carbon black is separated from liquid matter, then heated and thereby freed from hydrocarbons and water, and finally annealed for 20 to 30 minutes at 200.degree. C up to 2200.degree. C.

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Erftstadt, Germany

Hans Peter Beu