GB1134629A - Scorch-resistant blacks - Google Patents

Abstract

1,134,629. Treating carbon black. CABOT CORP. 1 Feb., 1966 [2 Feb., 1965], No. 4303/66. Heading C1A. Furnace carbon black is rendered scorch resistant when used in vulcanizable rubber compositions by uniformly mixing 100 parts by weight of the black with 0À1 to 1.0 part by weight of either an ammonium salt of an oxyacid of nitrogen or an ammonium salt of an oxy-acid of a halogen and heating the mixture at a temperature of 100-300‹ C. until the ammonium salt has been removed from the mixture. The preferred proportion of ammonium salt is between 0.2 and 0.6 parts per 100 parts by weight of black and suitable salts are given as ammonium nitrate, ammonium nitrite, ammonium chlorate, ammonium perchlorate and ammonium hypochlorite, the preferred salt being ammonium nitrate. A preferred temperature range is between 115‹ and 200‹ C. The ammonium salt may be dissolved or dispersed in a liquid before being mixed with the carbon black, and the preferred liquid is water. The mixing step may be carried out either before or during pelleting, the heating step being carried out either during or after the pelletizing and in the first case an amount of liquid is used such that no liquid surplus to that required for producing the pellets is used and in the second case an excess of liquid may be used in pelletizing which excess is removed during the heating step. To the mixture produced above there may also be added prior to the heating step a minor amount, not to exceed 0.5 part by weight per hundred parts of black, of a Mg, Zn or Al salt of an oxy-acid of nitrogen or a Mg, Zn or Al salt of an oxy-acid of a halogen, the proportion of said metal salt always being less than the proportion of ammonium salt used. The preferred metal salt is the nitrate.