How Rubber Reclamation Works
This article describes How Rubber Recycling or Rubber Reclamation is done. It describes in brief the types of process and steps involved.
Rubber recycling is the most energy efficient means of disposing rubber tires. Because of lower price compared to natural rubber, the demand of reclaimed rubber has been increasing all over the world. The natural rubber / synthetic rubber consumption ratio in India is 75:25, while globally the ratio stands at 44:56. The future of reclaimed rubber industry in India with its large population is likely to grow significantly in the years ahead.
Uses of Reclaimed or Recycled Rubber
Reclaimed rubber is used in making products such as mats, artificial grounds, weights, tires, automobile and military parts, belts and beltings, sheeting etc.
Types of processes involved in rubber recycling
1. Ambient processing
2. Cryogenic processing
1. Ambient process
This is the most commonly used method for rubber reclamation with significant cost benefits over other methods. The scrap rubber tires are cut with the help of cutter in small pieces which are further reduced to smaller size material by passing them through cracker mill. The material from cracker mill is then fed to grinder mill which crushes the material
into fine particles. The rotating drums with blades shear the rubber to smaller pieces. However the rubber has to be cycled a number of times to reduce it to desirable sized particles. The rubber which comes out after processing from grinder mills is called crumb rubber. This crumb has textile contamination in it. The textile can be separated from rubber using air aspirator.
Crumb rubber is further processed in autoclave rotary where it is mixed with processing oils and reclaiming agents. The rubber is baked at 160-180oC and high pressure (21kPa) for approximately 3 hours in the rotary. This rubber is called cured rubber or de-vulcanized rubber. It further goes to milling where the de-vulcanized rubber is fed to extruder which
converts the powdered material into solid mass. The solid mass is then passed through strainer where thin sheets of rubber are produced. Thin sheets bundle are then fed into refiner for refining process. The finished product comes out in the form of sheets which is known as reclaimed rubber.
2. Cryogenic process
Cryogenic process is a relatively new technology in rubber processing. It is the only economically feasible technology for processing of steel-belted tires. Pre-sized chunks of rubber are passed through a freezing unit where it is sprayed by liquid nitrogen. The rubber is cooled from -60 and -100oC. The frozen and embrittled rubber is fed to hammer mill where it is smashed into small pieces. Thereafter steel and textile particles are separated and the rubber is sent to de-vulcanization and reclamation processes which are similar to ambient process.
Rubber recycling yields carbon black, nylon fiber, steel and reclaimed rubber if the resources are completely recovered and each of these by products can be sold in the market.