Devulcanization

Pitt Consol 500 aryl disulfides in petroleum oil peptizer shortens devulcan-izing time by oxidizing mbber bonds... 

In the Reclaimator, a high pressure extmder, fiber-free mbber is heated to 175—205°C with oils and other ingredients. High pressure and shear between the mbber mixture and the extmder barrel walls effectively devulcanize the mixture in one to three minutes. In the Lancaster-Banbury method, high temperature, pressure, and shear are appHed to the mbber in a batch process that is otherwise similar to the Reclaimator process. In another high pressure process, scrap mbber is devulcanized at 5.5—6.9 MPa (54—68 atm) for ca five minutes. The product is milled, baled, or pelletized as in other processes. 

Entteerung, /. tar removal, tar separation, enttruben, v.t. uncloud, clear (up). Entvulkanisation, /. devulcanization, entvulkamsieren, v.t. devulcanize. entw., abbrev. (entweder) either. 

Isayev, A.I., Continuous ultrasonic devulcanization of vulcanized elastomers, US Patent, 5,258, 413, 1993. 

Luo, T. and Isayev, A.I., Rubber/plastic blends based on devulcanized ground tire rubber, J. Blast. Plast., 30, 133, 1998. 

Hong, C.K. and Isayev, A.I., Blends of ultrasonicaby devulcanized and virgin carbon black fibed NR, J. Mater. Sci., 37, 385, 2002. 

Scission of Polysulfide Crosslinks in Scrap Rubber Particles. Throughout this study, we used a single lot of scrap rubber peelings having the average composition described in the Experimental Section. We began our studies with Aliquat 336 as the phase transfer catalyst because of its proven effectiveness in simple systems and its commercial availability. When devulcanization is performed in a refluxing benzene/aqueous NaOH mixture, the chemical crosslink density (M... 

Origin of Catalyst Decomposition. The dependence of crosslink density reduction on catalyst concentration suggests that the catalyst decomposes during devulcanization. The Hofmann reaction (Equation 1) is a prime suspect under these conditions. 

Figure 2. Molecular weight distribution for soluble rubber produced from the devulcanization of a model BR vulcanizate.

Devulcanization in the Presence of Benzyl Chloride and Methyl Chloride. The above results suggest that catalyst efficiency might be improved when devulcanization is carried out with added alkylating agent. We find that this is, indeed, the case. Added benzyl chloride or methyl chloride further decreases the crosslink density for a given concentration of catalyst (Table 11). However, 1- and 2-chlorobutanes appear to be ineffective, possibly because of dehydrochlorination. 

Devulcanization of Rubber Peelings. Rubber peelings (10 g)(8) were charged into a 3-neck, 250 mL flask fitted with a water-cooled condenser and paddle stirrer. A solution of catalyst in 50 mL of... 

A sample of the sieved particles was also devulcanized by the phenyllithium method (4). An oven-dried 200 mL beverage bottle was charged with 1 g of 18-60 mesh particles and 40 mL of dry benzene. The bottle was capped with a 1-hole cap (extracted neoprene liner) and 10 mL of 2 M phenyllithium added. The mixture was shaken for 6.5 h at room temperature, then 1.5 mL of methanol added. Finally, 4 mL of methyl iodide was injected. At thi point the mixture comprised a rubber solution and a suspension of salts. An aliquot of the solution was taken for gpc analysis. 

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