Preh-werke Gmbh Co. Kg

Franz Kissner

Peter Ambros

Hugo Johannes

The invention relates to a method for producing powdery, vitreous carbon, and a paste made therefrom for producing resistive films having predetermined electrical conductivity. In production methods known in the art, pyrolysis of acrylamides is performed in mixture with water-soluble salts and, following pyrolysis, the powdered portion of the vitreous carbon is recovered by dissolving the salt component in water. The vitreous carbon is then dried, and the powder obtained in this manner is pulverized once again, as needed. A disadvantage of this method is that it is very time-consuming. In the solution now recommended, a preferably aromatic polymer is cured into a resin that is cross-linked in three dimensions, and in this state is ground to a powder prior to pyrolysis. Pyrolysis of the resulting powder is performed in a nitrogen atmosphere, so that powdered, vitreous carbons having different resistivities are obtained by using different final pyrolysis temperatures in each pyrolysis process. The vitreous carbon having a specific electrical resistivity obtained through pyrolysis is then dispersed into a binding agent and is ground in a mill together with the binding agent to a grain size of <10 &mgr;m. Then the viscosity of the paste with the vitreous carbon obtained in this manner for producing a resistive film is established by addition of a quantity of solvent for thinning. It is then possible to produce various resistive films from the paste produced in this manner, with a set but constant packing density of the vitreous carbon, having maximum mechanical and electrical stability that is very sturdy and abrasion-resistant in comparison to the surrounding area.

Method for manufacturing powdery, vitreous carbon useful for making pastes having predetermined electrical conductivity

The invention relates to a method for producing powdery, vitreous carbon, and a paste made therefrom for producing resistive films having predetermined electrical conductivity. In production methods known in the art, pyrolysis of acrylamides is performed in mixture with water-soluble salts and, following pyrolysis, the powdered portion of the vitreous carbon is recovered by dissolving the salt component in water. The vitreous carbon is then dried, and the powder obtained in this manner is pulverized once again, as needed. A disadvantage of this method is that it is very time-consuming. In the solution now recommended, a preferably aromatic polymer is cured into a resin that is cross-linked in three dimensions, and in this state is ground to a powder prior to pyrolysis. Pyrolysis of the resulting powder is performed in a nitrogen atmosphere, so that powdered, vitreous carbons having different resistivities are obtained by using different final pyrolysis temperatures in each pyrolysis process. The vitreous carbon having a specific electrical resistivity obtained through pyrolysis is then dispersed into a binding agent and is ground in a mill together with the binding agent to a grain size of &lt;10 .mu.m. Then the viscosity of the paste with the vitreous carbon obtained in this manner for producing a resistive film is established by addition of a quantity of solvent for thinning. It is then possible to produce various resistive films from the paste produced in this manner, with a set but constant packing density of the vitreous carbon, having maximum mechanical and electrical stability that is very sturdy and abrasion-resistant in comparison to the surrounding area.

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Hohenroth, Germany

Franz Kissner