When it comes to physical requirements, car upholstery leather differs from normal upholstery leather. Out of many, Zschimmer & Schwarz say that two requirements stand out as being particularly important:

1. Evaporation of chemical substances

2. Ageing resistance

The evaporation of substances is determined by carrying out fogging tests, eg according to DIN 75201 or SAE J 1756 and static or dynamic headspace according to VDA 277 and 278. All evaporating or sublimating substances in the leather can be detected with these methods under defined conditions, such as temperature and time.

The ageing of the leather is influenced by heat and light-resistance but also by the resistance to environmental cycles (climatic chamber test).

An important point in order to meet the physical expectations, is the correct choice of fatliquor. Latest results of analysis, made by headspace chromatography, show the responsibility of substances for emissions, especially compounds with a high vapour tension. These can be hydrocarbons and oils, as well as waxes with a relative low boiling point and substances without any linkage to the fibres are risky. Also substances with the tendency to sublimate, such as nitrogen products or ammonia-salts, have to be avoided.

For the ageing of leather, the parts of unsaturated substances in the fatliquor are responsible. In this case, for example, fish oil or vegetable-oils contain unsaturated fatty acids. The high offer of double-bonds makes an oxidation possible. It can result in a yellowing-effect, unpleasant smell and a hardening of the leather.

Out of this experience and knowledge, Zschimmer & Schwarz have developed a range of products for car seat leather.

Prinol CRC is particularly suitable for pre-fatliquoring. The product is based on a synthetic ester sulfonate and shows an excellent stability to all electrolytes. It can be applied in a pH below 2 (eg pickle for unsplit hides). It is easily soluble in cold water and can be added directly to the float. Prinol CRC is able to reduce the emission of volatile substances (fogging, haze, VOC, FOG). Furthermore, Prinol CRC has the following advantages:

* an accelerated even absorption of all chemicals in the pickle and tannage

* a very good exhaustion coupled with a low extractability

* good softness and grain elasticity

* excellent light and heat fastness

Prinol CRC treated wet-blue or wet-white material generally shows an improvement in mechanical processes such as sammying and shaving.

Prinol F-GB is a main fatliquor for all types of car seat leather. The product is based on a combination of polymeric, synthetic and natural softeners not containing any fish oil. It is easily soluble in cold water and can be added directly to the float. The application of Prinol F-GB results in an excellent softness and a pleasant touch. All fogging values such as VOC and FOG are very low. The heat and light fastness, as well as a neutral odour, is also very good.

Provol CAD is a main fatliquor for chrome-free automotive leathers, resulting in a very good softness, body and touch. The product is based on a combination of natural and synthetic oils with special emulsifiers, containing a high amount of high-grade lecithin. It does not contain any fish oil. All emission values such as fogging, VOC and FOG, are very low. In the following figures the influence of the products to the emission of volatile substances is described graphically.