31 August 2010

Reclaimed Rubber

Manufacture of Reclaimed Rubber
The major reclaiming processes are the following.

Sub Topics
  • Heater or Pan Process
  • Wet Digester Process
  • Reclaimator Process        

    Heater or Pan Process

    Any fiber present is separated mechanically and the ground fabric free scrap is blended with reclaiming agents. The same is fed into large horizontal single-shell heater. After devulcanisation, the heater cakes are removed, broken up, milled and refined. The temperature range employed during reclamation is 170-2100C, for a period of 4-12 hours.

    Wet Digester Process

    Coarsely ground scrap mixed with reclaiming and defibering agents and a large excess of water is heated in a digester. After discharge, the devulcanized rubber is washed, dewatered, dried and blended with processing agents such as oil, refined, strained and packed.

    Reclaimator Process

    Whole tires are cracked to a convenient size, and the fibre is removed mechanically. The relatively fiber-free scrap is ground to approximately 30 mesh before being mixed with chemical agents for reclaiming continuously in a reclaimator. The temperature range is 204-260o C and the devulcanization time is 1-4 minutes. Reclaimed material is then mixed and blended with small proportions of reinforcing and processing agents.

    Processing Advantages of
    Reclaimed Rubber
    1. Low power consumption during break down and mixing. During manufacture, reclaimed rubber has already been thoroughly plasticised so that it breaks down and mixes more quickly than the virgin rubber.
    2. Low mixing, calendaring and extrusion temperature.
    3. Non-critical calendaring temperature range. Reclaim is less nervy than virgin rubber and hence builds up less internal heat in the calender bank, imparting more process safety.
    4. Fast, Uniform Calendering and Extrusion.
    5. Improves penetration of fabric.
    6. Improves tackiness and hold the same over a broader range of temperature.
    7. Reduce and retard blooming of sulfur from both cured and uncured stock.
    8. Low swelling and shrinkage on extrusion and calendaring.
    9. Low Thermo plasticity.
      Due to the cross linked structure of reclaimed rubber, its compounds are less thermoplastic than virgin rubber compounds and therefore when extruded and cured in open stream, they tend to hold their shape better.
    10. Low volume cost for the product


    Major Uses of Reclaimed Rubber
    1. Passenger Tire Carcass
    2. In extruded and calendared products
    3. In products such tiles for laying pedestrian concrete areas, Animal mats used in stables, Insulation tiles used in metro railways for reducing the noise level etc.
    4. Inner Tubes: - A moderate proportion of butyl reclaim is used in butyl inner tubes.
    5. Tubeless Tire Liners: - Butyl reclaimed rubber is used widely because of its good air retention property.

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