Cryogenic processing of used tires and other materials

Old tires are cut into strips (49), cryogenically cooled in liquid nitrogen (60) to make the rubber brittle, and the frozen strips fed through a pair of pinch rollers (50A). One of the rollers has a grooved and knurled surface. The rollers are pushed together by hydraulic rams; the pinch force is large enough to shatter the surface of the rubber, but small enough to leave the bulk of the strip intact, and the pinch force remains the same even if the thickness of the strip varies. The strip passes progressively through successive pairs of rollers, each time the surface of the strip is shattered and the fragments fall clear. With this treatment, the steel wires and textile cords in the tire separate or delaminate very easily, and without being crushed or damaged. All the components of the material composite are recoved and separated for recycling. The rubber crumb thus separated is treated with a suitable chemical treatment for breaking down the molecular cross-links, mixed with plastic material and then repolymerised.