Prevulcanization inhibitors

The inhibition chemistry has been extensively studied. As shown in equation 1, the prevulcanization inhibitor (retarder) reacts with MBT (1) before it can form polysulfides. 

OT,-methionine propane odorant natural gas odorant components water repeUants prevulcanization inhibitor flocculent... 

Longer processing times have commonly been obtained by the use of chemical retarders (77MI11504). These compounds not only delay the beginning of cure, but also affect the rate of cure once it has started. The use of a prevulcanization inhibitor (PVI), on the other hand, delays the onset of vulcanization with only minimal effects on the rate of cure and on the properties of the vulcanizate. The introduction of PVIs represents one of the major developments in the rubber industry in recent years (70USP3546185). 

Although Monsanto can rely on only two of its own raw materials, tertbutylamine and p-nitrochlorobenzene, for its range of additives, it is regarded as an efficient producer and a pioneer in antiozonants based on p-phenylenediamine and prevulcanization inhibitors. It has one of the most complete ranges of additives for rubber and the most modern units to manufacture them. 

Use Manufacture of aspirin and salicylates, resins, dyestuff intermediate, prevulcanization inhibitor, analytical reagent, fungicide. 

Santogard PVL [Monsanto] N-(Cy-clohexylthio) phthalimide prevulcanization inhibitor. 

Hazardous Decomp. Prods. Heated to decomp., emits toxic vapors of NOx and SOx Uses Prevulcanization inhibitor, retarding agent delays onset of accelerated sulfur vulcanization... 

To assist in control of the onset of vulcanization, a retarder or prevulcanization inhibitor (PVI) is used. Retardation of the onset of cure does not mean that the rate of cure is slowed in fact, cure rate may actually be increased. Rather, there is an extension to the induction period prior to cure. 

Electrochemical oxidation and reduction of het-ero atom compounds, such as N, S, and P compounds, has been intensively studied and utilized for synthesis of many fine chemicals [1-4]. Electrooxidative S-S, S-N, S-P, and N-P bond formation is performed successfully by electrolysis of thiols, disulfide/amine, disulfide/phosphate, amine/ phosphate, and so on, affording useful chemicals, e.g., thiuram disulfide [17], sulfenamide [18], sulfenimides [19], phosphorothiolates [20], phosphoramidate [21], and so on. For instance, cross-coupling of phthalimide and dicyclohexy disulfide is performed by electrolysis in acetonitrile containing a catalytic amount of sodium bromide under a ccaistant apphed voltage (3 V, 0.7-0.9 V vs. SCE) to afford N-(cyclohexylthio)phthalimide, an important prevulcanization inhibitor in the rubber industry, in quantitative yield [19] (Fig. 4). 

Torii S, Tanaka H, Ukida M (1979) Electrosynthesis of hetero-hetero atom bonds 3. Sodium bromide promoted electrolytic cross-coupling reaction of imides with disulfide. N-(cyclohexylthio)phthalimide, an important prevulcanization inhibitor. J Org Chem 44 1554-1557... 

The existence of such a delaying process is of considerable technological importance and, as will be shown in the next section, subsequent studies have led to the development of prevulcanization inhibitors. 

A comprehensive review of the chemistry and technology of prevulcanization inhibitors has recently appeared (Trivette et a/., 1977). 

The Mooney scorch times of ENR mixes can be increased by the use of commercial prevulcanization inhibitors (PVI) once the base has been added. The response of these materials depends on the cure system employed and parallels that observed with NR and other unsaturated polymers. 

The vulcanization profiles of a semi-EV black filled (30phr ISAF, N220) ENR-50 compound (Table 1) with and without the addition of a prevulcanization inhibitor are recorded in Fig. 10. The overall response of ENR to changes in accelerator type and level is similar to that observed with NR. The major adjustment that has to be considered is due to the presence of base. 

The addition of a base neutralizes the acids produced during ageing and substantially improves the ageing properties of ENR (Table 11). Sodium carbonate is the most effective base but significant amounts can result in scorch problems (Fig. 9). To control the scorch a prevulcanization inhibitor can be used in conjunction with sodium... 

CTP is an inhibitor commercialized by Monsanto in the 1970s. Monsanto was the sole producer of CTP under their trade name of Santogard PVI (prevulcanization inhibitor). However, with the expiration of their patent, there are several manufacturers of CTP in the world today. 

Cyclohexyl mercaptan is chlorinated to cyclohexyl sulfenyl chloride, which reacts with phthalimide to produce CTP, a prevulcanization inhibitor for rubber. 

Phthalimide reacts with cyclohexyl sulfenyl chloride to produce CTP prevulcanization inhibitor. 

Santogard PVI—or CTP (PreVulcanization Inhibitor) DTDM, Sulfasan R or Vanax A... 

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