HETEROGENEOUS REACTIONS BETWEEN ZINC OXIDE AND 2-MERCAPTOBENZOTHIAZOLE (M)

Shizuka H., Azami T.

doi:10.2324/gomu.40.467

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Other Title

有機加硫促進剤2-メルカプトベンゾチアゾールと亜鉛華との不均一系反応
ユウキカリュウソクシンザイ 2-メルカプトベンゾチアゾールトアエンカトノフキンイツケイハンノウ
HETEROGENEOUS REACTIONS BETWEEN ZINC OXIDE AND 2-MERCAPTOBEN-ZOTHIAZOLE (M)
加硫促進機構に関する研究 (第5報)

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Heterogeneous reactions between ZnO and M were studied, by means of tracer method (S³⁵ or Zn⁶⁵), in xylene and in rubber, respectively. Zinc mercaptobenzothiazole (MZ) was produced by these reactions. Heterogeneous reactions in xylene were observed as zero order and their rates had a nearly constant value at every temperature (120, 130 and 138°C). The rate-determining step does not consist in the reaction process, but in the dispersing process of the product (MZ) from ZnO surface. The effect of addition of small amounts of ZnO or MZ on the exchange reaction between M and S* was investigated. The reaction rate was remarkably increased. The exchange reaction between MZ and S*, in xylene heterogeneous system, reached quickly the exchange equilibrium. MZ and radioactive M were easily exchanged. The curing of rubber gave a large quantity of MZ (yield, 73%). The results of these re-actions can be represented by the following schemes (1), (2), (3) and (4). 2M+ZnO→MZ+H₂O (1) MZ+S₈^*ring→k₂M^*Z+·S_n^*·(2) M^*Z+M→MZ+M^* (3) M+S₈^*ring→k₄M^*+·S_n^*· (4) k₂>k₄ From these studies, it is concluded that the reaction product (MZ) promotes the ring opening action of elementary sulfur (S₈ ring structure) and active sulfer (· S_n ·) enables the curing of rubber.

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