Green Production of Rubber Accelerators NS & CBS (by Plasma site)

The development of rubber accelerators is gradually moving toward environmental friendliness, multi-functionality and high efficiency. Sulfenamide vulcanization accelerators are important varieties, with typical representatives NS and CBS (CZ), which offer both excellent anti-scorching safety and fast vulcanization speed. They are widely used in the production of rubber products such as natural rubber, styrene-butadiene rubber, cis-polybutadiene rubber and isoprene rubber, especially in tire manufacturing, with slight discoloration and pollution.

There are four oxidative condensation synthetic routes for NS and CBS worldwide: sodium hypochlorite oxidation, chlorine oxidation, catalytic oxidation, and electrolytic oxidation.

At present, the sodium hypochlorite oxidative condensation method is widely adopted for industrial production at home and abroad. In the first step, mercaptobenzothiazole is converted into its sodium salt with sodium hydroxide solution; in the second step, it undergoes oxidative condensation with tert-butylamine or cyclohexylamine to produce NS or CBS.

This process features mature technology, mild reaction conditions, good product quality and high yield. Its disadvantages include solvent separation and recovery, as well as the generation of a large amount of industrial wastewater. Solvent recovery is difficult in the oil-phase process, and recovery of tert-butylamine or CBS is also challenging in the aqueous-phase ratio method.

The patented technology “Synthesis of Rubber Accelerators NS and CBS by Plasma One-step Oxidation” adopts activated oxygen (ozone) generated from compressed air or oxygen through an ozone plasma generator to directly oxidize raw materials for the preparation of NS or CBS. This process features simple, stable, mature, safe, environmentally friendly and energy-saving production, no pollution, excellent product quality (initial melting point >106 °C and 98 °C respectively), high yield (99%), low production cost and easy industrialization.

Technical Characteristics and Innovations:① Activated oxygen generated from air or oxygen via a plasma generator directly oxidizes reactants without oxidant compounds, catalysts or organic solvents, producing no salt-containing industrial wastewater and no pollution;② Water is used as the only reaction medium;③ A one-step reaction directly yields a pure product, greatly simplifying the production flow and reducing production costs.

In other words, integrated innovation of materials, technology, processing, production equipment and products is realized.

Two authorized invention patents have been granted for this technology. It has won 2 first-class municipal awards for technological invention, 1 second-class municipal award, and 2 third-class provincial and ministerial awards. The technical level of the achievement is internationally leading.Subsequently, the annual output value is about 200 million RMB, with products also exported.