Tuesday, 31 March 2015

Itac use Copper for colour and catalysis

Elizabeth Henderson
Product Development Manager

Copper and Itac overlap in the worlds of colour and catalysis. Copper phthalocyanine is the starting point for all phthalocyanine pigments, as copper bonds readily with the nitrogen atoms in phthalonitrile (1,2 dicyanobenzene) to form a stable complex. Treatment with acid removes the copper from the centre of the molecule, leaving the phthalocyanine copper-free. This can subsequently be reprocessed (for instance by recrystallization from sulphuric acid) to refine its colour and dispersion properties. Itac uses dispersions of phthalocyanine pigments to provide strong blues and greens for our coatings products.
Just as copper is a catalyst in the production of these colours (the metal used initially is recoverable from the process), copper saccharinate can be used as a co-catalyst for the polymerisation of methyl methacrylate to form structural acrylic adhesives. In the presence of cumene hydroperoxide and N,N-dimethyl-p-toluidine, the Cu(II) is reduced to Cu(I). This free Cu(I) complexes with N,N-dimethyl-p-toluidine to form a complexed ion which is a strong reductant for cumene hydroperoxide, whose decomposition is further catalysed by saccharine. The copper saccharinate thus initiates the creation of free radicals from cumene hydroperoxide which in turn initiate polymerisation of methyl methacrylate.
As well as providing useful copper compounds, copper metal itself has been mined and refined for millennia. The Manchester Museum is home to the Alderley Edge shovel which was found in the exhausted copper mines, along with various stone tools, in the nineteenth century. Radiocarbon dating has shown that it was made around 1750 BC. Malachite is the green copper ore found at Alderley Edge – it is copper carbonate, with the characteristic brittleness of ionic solids. It crystallises in space group P21/a, and as well as being found in Cheshire, there are major deposits in the Ural Mountains, southern Africa and Latin America. Cornwall’s tin mines also yielded copper as a by-product.
Copper’s excellent electrical conductivity and malleability have been exploited by its use for power and communications delivery systems. Until the advent of fibre optic cable and wireless transmission (the clue’s in the name) all ‘instant’ communication was made using electrical impulses sent down copper wires. Copper is still a component of modern under-sea cables.
Copper has made another contribution in the maritime world, by its use as an outer shell for the hulls of timber ships. It is impermeable to teredo worms, resistant to corrosion by sea water, and its chemistry limits the growth of marine life on the vessel.