BY

R.Prasanth

• Recycling is processing used materials (waste) into new products to prevent waste of potentially useful materials, reduce the consumption of fresh raw materials, reduce energy usage, reduce air pollution (from incineration) and water pollution (from landfilling) by reducing the need for "conventional" waste disposal, and lower greenhouse gas emissions as compared to virgin production.

• Recycling is a key component of modern waste reduction and is the third component of the "Reduce, Reuse, Recycle" waste hierarchy.

The major steps involved in recycling Nylons are,

Identifying the source Segregation of waste Nylon products Separating from impurities Size Reduction Depolymerization OR Processing the waste directly to

pellets

Nylon waste arises from various products, but not all are easily recycled, the ones which can be easily recycled are as follows,

Nylon fishnet scraps Nylon carpet wastes Nylon fiber or yarn waste Nylon waste generated during

polymerization and few other automobile parts made out of Nylon can be recycled. Nylon tyrecord being adhered to the rubber of the tyre is very difficult to separate. Old carpets may also be used as a feedstock to produce other products, such as auto parts, plastic lumber, parking stops, and carpet pads.

The waste nylon products are bought for a very low cost and dumped in a place to be recycled later.

All the waste materials are identified and collected from various places and stored for recycling purpose

Before being processed or sent for depolymerization the waste polymer must be separated from impurities like metals or even some times other polymers or some other impurities.

This is done in order to maintain the efficiency of the process and so that the material and the recycling effort should not be wasted.

If such impurities are present they will lower the mechanical properties of Nylon and thus make it unusable.

It is not possible to feed the whole plastic waste as such to the extruder or the reactor.

Hence it is being reduced to smaller size in size reduction machines.

The smaller size Nylons can be easily processed in the extruder.

Now we are going to see two MNC’s as an example on behalf of Nylon waste recycling on the concern of Depolymerization.

The first industry being BASF(Badische Anilin- und Soda-Fabrik).

This plant is in Arnprior. They manufacture Nylon 6 which is being used for carpet applications as well as other engineering applications. The waste this industry uses for recycling is Nylon carpets.

The next industry is SRF Ltd ( Sri Ram Fibers ) which is in Manali.

SRF manufactures Nylon 6 which is being used for various applications such as tyrecord and automobile parts.

The recycling material that they use are Waste Nylon Fishnets Waste Nylon 6 polymer

The process of depolymerization

involves a series of steps, they are as follows,

Waste feed Melting Cracking Chemical Treatment Distillation

Melting : The waste nylon after being feed is melted

in a reactor at 260-270°C to form a melt.• Cracking : To the melt steam at 400°C is passed

inorder to crack the polymer nylon to form the monomer caprolactum.

The catalyst used for cracking is ortho phosphoric acid (H3PO4).

• Chemical Treatment : As the monomer is obtained from waste

nylon its colour will be brown or dull yellow colour. Hence chemical treatment must be done. Potassium permanganate and carbon is passed through the monomer to remove oxidisable impurities to improve colour.

Distillation : The monomer will be mixed with

water and hence the mixture is distilled to separate the monomer caprolactum and water.

In some cases depolymerization is not required for recycling.

In those cases the waste nylon is been size reduced and feed in to an extruder.

The extruder melts the waste polymer and gives in form of molten strands which is cooled using a cooling bath arrangement and cut in to small pieces using a pelletizer.

Recycling is the term which is going to play a vital role in conservation of the world.

Recycling becomes the responsibility of each and every individual in this earth.

There are a lot of recycling methods and recycling centres being developed for each and every thermoplastic material, everyone of us should use the facility to benefit out of it.