Bulk concentrates commercial terms

An extensive screening of structure-activity relations revealed ( 1 ) the outstanding properties of N,N -disubstituted PD. It is generally accepted that the presence of N-sec.alkyls accounts for better antiozonant protection than that of N-prim. and N-tert.alkyls or N-aryls (21). This may be one of the clues to decipher the chemical pathways of the antiozonant mechanism. The final effect is moreover fully dependent on the composition of the vulcanizate. The structure of commercially used antiozonants is an optimum compromise of efficiency, physical properties and toxicity. N, N -Disec.alkyl-1-4-PD are used in the U.S.A., N-sec.alkyl-N -aryl-l,4-PD are preferred in Europe. N,N -Diaryl derivaties are not applied as antiozonants in NR, BR, IR, or SBR. One of the reasons may be their low solubility in rubber vulcanizates (22). It does not allow them to reach a concentration level in the rubber bulk which is able to act as a long-term operative store of a stabilizer ready to supply the rubber surface slowly but continuously with active compounds by migration and to maintain the protective effect without inefficient quick blooming of an incompatible PD. A chemical reason accounting for the minority antiozonant role of N,N -diaryl PD is discussed later. 

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