It has been known for at least 4 decades, e.g. from French Pat. No. 906,893, that the degradation (as shown by a deterioration in tensile properties) of polyamides, i.e. nylon fabrics, by exposure to light, has been improved by the addition of copper in the form of cupric compounds, and it has also been known for a long time that their dye-lightfastness has been improved by use of copper compounds. These cupric stabilizers have made it possible to use nylon upholstery fabrics in automobiles, where exposure to heat and sunlight are severe. Other compounds which absorb uv (utraviolet) light have been evaluated in nylon, but none have been found to be as effective as the copper compounds.
As the use of nylon fabrics in automotive upholstery has increased, the range of available shades has multipled, and the automotive industry has become more demanding in its requirements for dye-lightfastness. For instance, a requirement in 1945 that dyed fabrics be able to withstand 80 hours exposure (in a standard test using the carbon arc Weather-Ometer with minimal dye fading) had been increased to 300 hours exposure, by 1978, as the use of selected dyes, improved dyeing procedures, and copper compounds as light stabilizers enabled such advances to be achieved.
It is believed that the automotive industry will require dyed fabrics to withstand 488.8 kilojoules/meter.sup.2 (KJ/m.sup.2) exposure in the Xenon arc Weather-Ometer (the current preferred exposure method), which corresponds to approximately 600 hours exposure by the carbon arc test, i.e. about double the 1978 standard. This presents a serious problem, as such a high level of dye-lightfastness cannot be achieved with currently available dyes, dyeing technology, and stabilizer technology.