Ecological and economical advantages of anti-soiling leather protection

Market assessment:
The market for leather in light colours is increasing, especially in the upholstery sector. From both the aesthetic and psychological points of view, car manufacturers tend to use more light brown, beige and even white leather seats for their luxury cars. Even furniture leather for dining room chairs and lounge suites are marketed more and more in light colours.
Today light coloured upholstery leather represents an estimated market share of 20% of the total upholstery market. Approximately 450 million ft2 of furniture leather and 320 million ft2 of automotive leather are produced in light colours with the trend increasing.

Environmental aspect:
The lifetime of a lounge suite upholstered with light coloured leather depends very much on the anti-soiling and the cleanability performance of the leather employed. Also from the environmental point of view this is of major importance.
Modern life cycle assessments of articles do not only include the evaluation of the manufacturing process of the leather and the subsequent furniture production. Even the lifetime of an
article as well as the after life use is playing an important role nowadays and will have an even more important role in the future. This highly complex topic can be put into simple words though:
If the lifetime of an article can be doubled due to an improved longevity the environmental impact is reduced by 50%.
Compared to how much effort needs to be made in order to improve a manufacturing process to achieve a better life cycle rating, respective efforts in a given article’s development are often much more efficient.
Since a positive environmental profile of an article is more and more valued, from our point of view it is worth it to further establish and develop best practice technologies in terms of anti-soiling and cleanability.

Economic aspect:
As mentioned above, the market for high quality and light coloured upholstery leather is worth approximately 770 million ft2 per year and is increasing in demand.
High qualitative characteristics require high performance chemicals and additives which improve the anti-soiling and cleanability performance of such articles.
Those products are true speciality chemicals which may increase the cost of a finishing formulation noticeably. However, if you value the additional performance versus the additional cost, the final consumer’s willingness to spend more money on such high quality products should not be underestimated.
The market price of a high quality leather lounge suite easily ranges from approximately €3,000 up to €10,000. A typical SUV vehicle fitted out with leather costs between approximately €2,000 and €8,000 more than a standard textile fitted edition.
Comparing the additional cost of some €5–10 per unit (lounge suite or car seats) for a best possible anti-soiling/cleaning performance and the enhanced longevity of such articles with the commercial value of those items, the cost can be considered of minor importance.
Today, it is possible to produce leather with a long lasting anti-soiling/cleanability performance which remains or can be kept clean over an extended period of time while still maintaining its initial value.
Promotional packages which include, for example, warranties for the final consumer would even overcompensate for the additional cost of such articles and substantially improve the image of leather as a durable material.

Best practice technology:
Due to this economical and ecological assessment, LANXESS have dedicated significant R&D resources in the field of anti-soiling/cleanability in recent years.
New chemicals have been developed, formulations have been screened and optimised and test procedures have been established. The resulting products and the application technology are marketed under the brand Aquaderm X-Shield. During these studies it became clear that a perfect anti-soiling and cleanability performance is not just an additional criterion which can be achieved by simply adding certain chemicals into a topcoat formulation.

Anti-soiling characteristics
As described in various articles1–3 it must be differentiated between anti-soiling and anti- staining performance. This is due to the fact that different contaminants have a different impact on the degree of damage they may cause on the leather.
Soiling is the constant and regular exposure of the leather to contaminants throughout its daily use. The most common contaminants are dust, carbon compounds, oils and dyestuffs from textiles, just to name a few.
Other than soiling, the so-called staining can be seen as the accidental and occasional contamination of leather products. Such contaminants can be of any origin. Wine, coffee, lipstick, ball or felt pens represent only a small yet very important extract of a myriad of substances which can contribute to a significant loss in value or even the destruction of precious leather items.
Due to this fact it was of need to develop different testing methods focusing on the required performance characteristics of the respective leather articles.
In the case of soiling, which is an important issue in the automotive industry, standardised fabrics, contaminated with different pollutants, are rubbed over the leather by means of the Martindale abrasion tester. The degree of soiling is measured after the treatment as well as after a cleaning process the leather has to undergo after the exposure to different climatic conditions.
In the case of staining the contaminants are applied directly onto the leather and wiped off after a certain residence time.
During the development phase of the Aquaderm X-Shield system it became clear that such a wide variety of potential contaminants along with an even bigger number of different leather properties require individual anti-soiling systems. Although a ‘one can do all’ system does not exist it was found that polymers with built-in TFE (tetrafluoroethene) units prove to be the best suitable substances for such applications. This is based on the fact that these substances have a performance profile which is very similar to PTFE* (polytetrafluoroethene).
In practice there are two ways of using this chemistry in the leather field namely in so called comb polymers or in linear copolymers.
Comb polymer based products such as Aquaderm X-Shield L are used as an additive in special topcoats and provide outstanding dirt repellency and cleanability. Nevertheless crosslinking is only partly possible which leads to a limitation of the durability of such systems.
In the case of linear TFE-copolymers such as Aquaderm X-Shield G and Aquaderm X-Shield M2 the TFE groups are permanently built into the polymer backbone. Combined with additional functional groups such products offer a versatile application field to the leather industry.
In cooperation with Daikin from Japan, LANXESS have developed a water based linear TFE copolymer for use in leather applications. Finishing systems based on this unique chemistry can be pigmented and crosslinked with isocyanate which leads to an excellent film formation. At the same time, different gloss levels can be adjusted and suitable feel agents can be added. The end result means that a superior and long lasting anti-soiling resistance along with an outstanding cleanability performance can be achieved.

Conclusion
Aquaderm X-Shield technology can provide leather articles with outstanding performance in terms of anti-soiling and long term cleanability, generally summarised under the term ‘anti-soiling’. Depending on the requirements, formulations can and must be customised for each individual purpose. Specially developed high performance polymers based on fluorocarbon are used in carefully balanced recipes to provide anti-soiling performance without sacrificing other physical requirements.
The additional cost for this chemistry is not negligible. They stand, however, in a reasonable ratio to the additional value for the end consumer because they extend the longevity of a high performance article.
*Remark by the author: PTFE, commonly known as Teflon, is a trademark of DuPont

References.

1) Soil resistant leather comes of age, by Dietrich Tegtmeyer, Tillmann Hassel, Juergen Reiners, Stefan Wildbrett, Michael Franken, Leather International, April 2009 page 22–24
2) Die neue X-Shield Generation: ein überzeugendes konzept auf Fluorpolymerbasis, Dietrich Tegtmeyer, Tillmann Hassel, Michael Franken, Pro-Leder, December 2008
3) Use of Novel Tetrafluoroethane Copolymer Dispersions as Protective Finish for Leather by J Reiners, T Hassel, R Maier,
S Wildbrett, D Tegtmeyer, M Maeda, K Imoto, A Ueda. JALCA, Volume 102, Number 10, Page 322–336, 2007