Society is increasingly concerned with climate change, biodiversity and consumption exceeding Earth's capacity to regenerate resources. Consumers like to contribute their share to make the world a better place by preferably buying sustainable products. Therefore, consumer goods are monitored for their sustainability profile to ensure they are based on the principles of best practice, which include:
– state-of-the-art technology applied in manufacturing
– use of "Level 3 ZDHC MRSL Version 2.0 – compliant chemicals"
– low CO2 footprint
– high degree of renewable resources
Automotive Leather is a popular choice used in car interiors since it is regarded as durable, strong and natural. Nevertheless, alternative materials are increasingly considered for upholstery, car seats, door panels and dash boards.

What makes automotive leather unique?

The answer is quite simple. It is the collagen, the raw material of leather. Collagen is a renewable, high molecular weight, bio polymer with a very unique structure.
The tanning process protects collagen from decomposing, and the resulting leather features unique properties, such as: physical strength, 3-dimensional stability, breathability and recyclability. No alternative material can combine these features as leather does. However, the most significant difference is the bio-content. Finished automotive leather contains 75 – 85% renewable biomass, whereas alternative materials are made of 85 – 95% fossil fuel based chemistry.

Compliant chemistry "level 3 ZDHC MRSL version 2.0"

Producing automotive leather involves chemicals and these chemicals are under continued and ever increasing scrutiny with regards to their ecological and toxicological profile. The same is true for the final product of this chemical processing, the leather. The product range of TFL is compliant according to "Level 3 ZDHC MRSL Version 2.0" and the resulting leather treated with TFL chemicals can fulfil the RSL specifications of all major brands.

Material Balance Method DIN EN 16785-2

A number of TFL products are based on renewable biomass, which has undergone physical, chemical or biological treatment. These bio-based products contain biomass, but fossil components, minerals, inorganic salts and water may also be present. So, how to calculate the bio-based content of a product: TFL has selected the Material Balance Method, DIN EN 16785-2, to calculate the percentage of renewable biomass in relation to the total dry content of the product. With the knowledge of the bio-content of their wet-end product portfolio, TFL is not only offering compliant chemistry but can also further boost the bio-content of automotive leather, by selecting relevant products.

Wet-end process with renewable resources

By examining the wet end process in detail, TFL aims to show how it can transform a standard recipe into a formulation with a sustainable pedigree.
Below see a "standard" automotive retanning process:

100% water 35°C
1,0% SELLA® Fast Black WB           15 min
3,0% chrome sulphate (26/33)
2,0% CORIPOL® ESU                          30 min
3,0% SELLATAN® RP                            60 min then automatic overnight drain
100% water 30°C
2,0% SELLASOL® NG liq
1,5% sodium formate                           20 min
3,0% MAGNOPAL® SFT-F
1,0% sodium bicarbonate                 60 min
drain, wash, drain
100% water 35°C
1,5% CORIPOL® SLG
2,0% CORIPOL® ESU                     20 min
4,0% MAGNOPAL® TGR              30 min
4,0% SELLATAN® MBS
6,0% SELLATAN® FB liq              40 min
100% water 55°C
6,0% CORIPOL® ESU
1,5% CORIPOL® SLG
1,5% MAGNOPAL® TGR            60 min
1,0% formic acid                               30 min

This recipe gives us:
– bio-index of 6% => 6% of the entire chemistry used is based on renewable biomass
salinity of 6 kg / 100kg shaved weight => 6 kg of inorganic salt will end up in the effluent
COD of 4470 g O2 / l => COD value of entire effluent

By replacing some products with a higher bio-index, the recipe reads as follows:

100% water 35°C
1,0% SELLA® Fast Black WB     15 min
3,0% chrome sulphate (26/33)
2,0% CORIPOL® AV                       30 min
3,0% SELLASOL® Pure M            60 min then automatic overnight drain
100% water 30°C
2,0% SELLASOL® NG liq
1,5% sodium formate 20 min
6,0% MAGNOPAL® Pure A
1,0% sodium bicarbonate               60 min
drain, wash, drain
100% water 35°C
1,5% CORIPOL® LEO
4,0% MAGNOPAL® Pure A            30 min
4,0% tara
6,0% SELLATAN® GS-B liq               40 min
100% water 55°C
6,0% CORIPOL® AV
1,5% CORIPOL® LEO
1,5% MAGNOPAL® Pure A             60 min
1,0% formic acid 30 min

These changes in the recipe now give:
bio-index of 44% => =>44% of the entire chemistry used is based on renewable biomass
salinity of 4 kg / 100kg shaved weight => 4 kg of inorganic salt will end up in the effluent
COD of 4190 g O2 / l => COD value of entire effluent

A factor for consideration when changing a recipe, is that the article and the fastness properties, still stay the same despite changing these products. In this case, the leathers are the same in quality, break and softness. The fastness profiles are also comparable.

Pure Range Products – best in class

All products in the TFL range used in the retanning process have been tested for a bio index score, and that information is available from your TFL representative. Within the TFL portfolio, we have highlighted the best in class products as "The Pure Range", which currently contain the following products:

MAGNOPAL® Pure A – polymeric retanning agent with a bio-index of 93
CORIPOL® Pure F – marine oil based fatliquor with a bio-index of 91
CORIPOL® Pure L – lecithin based fatliquor with a bio-index of 79
CORIPOL® Pure V – fatliquor based on Vegetable oils with a bio-index of 82
SELLASOL® Pure H – protein based filler with a bio-index of 97
SELLASOL® Pure M – protein based filler with a bio-index of 100

Conclusions

In addition, the following important features should be taken into account:
These factors are:
– bio based content using the Material Balance method
– product toxicity using the Global Harmonised System of Classification (GHS)
– biodegradability of residual float
– salinity
These demonstrate both comprehensive and innovative ways of looking at the sustainability of not only the products but also the recipe. This recipe can be used to increase the renewable biomass content of leather – calculated using the recognised Material Balance Method DIN EN 16785-2. With this ‘tool kit’ in mind, we now have the possibility to increase the bio-content of leather for the automotive industry, and subsequently for environmentally conscious consumers.