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Nylon production


Nylon, a thermoplastic, is one of the most important synthetic
polymers. About four million tonnes per year is produced worldwide. Much of the nylon
is made into fibres for ropes, clothing and for reinforcing tyres. Nylon is made from two monomers. Adipic acid, more properly called hexanedioic acid, has a chain of six carbon atoms. Just
concentrate on the ends of the chain Hexamethylene diamine, more properly called 1,6-diaminohexane, also has a chain of six carbon atoms. Again, just concentrate on the ends of the
chain. When the two monomers react together a molecule of water is produced as each
link is formed. These two monomers continue to link
together to form long chains called nylon. The raw materials used to make the two monomers are cyclohexane and adiponitrile. These are both derived from crude oil. Cyclohexane is oxidised, first by air and then by nitric acid, to
give adipic acid. Adiponitrile is hydrogenated to give hexamethylene diamine. The two monomers first react to form a salt. Heating the salt to drive out water produces nylon. On this site, cyclohexane arives by pipeline and is stored here. It is first oxidised here and then further oxidised, with nitric
acid made from ammonia, in this plant. The product is adipic acid. The hydrogenation of the adiponitrile to produce hexamethylene
diamine takes place here and the two monomers are mixed in this
building. Polymerisation is carried out in this plant and nylon stored for delivery to customers. Cyclohexane is oxidised to form adipic acid in two stages, first with air and then
nitric acid. This is what happens in these reactions. Adipic acid, one of the two monomers, is a white
powder. Adiponitrile is reacted with hydrogen to give hexamethylene diamine, the second of the two monomers. The two monomers are mixed together and react to give
nylon salt. This, and all other processes, are monitored and controlled remotely. Nylon is produced from nylon salt by driving out the water. These are the tops of the autoclaves in which the salt, at a pressure of 18 atmospheres, is heated to a temperature of 280 degrees Celsius. At this stage additives and pigments are added and the conditions can be changed to produce polymers with different
properties. When the white nylon is produced it’s
molten and is forced through holes to form laces of nylon The laces are cooled in water and chopped into short lengths about three to four millimetres long
called granules. Nylon leaves the site in lorries as granules. The granules which are thermoplastic will be remelted and
moulded, or forced through fine holes to make nylon fibres.

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