The business of waterproofing

13 October 2019



With over two decades of industry knowledge, Lionel Champanhet joined Stahl following its acquisition of the BASF Leather Chemicals division in 2017 and is now senior technical manager. Carl Friedmann sat down with him during APLF in Hong Kong in March to discuss how he is helping the company to break new ground, in particular with a pioneering 100% polymeric waterproofing system.


Renowned Netherlands-based leather chemicals company Stahl is in lockstep with the future of leather as a progressive and dynamic material created from an environmentally conscious supply chain. Its acquisition of the BASF Leather Chemicals division in 2017 represented a massive knowledge injection in terms of capabilities, and major strides have subsequently been made in terms of optimising operations and reducing costs.

Continuously upgrading its production sites and laboratory facilities to achieve better efficiencies that lead to an improved environmental footprint, Stahl is able to employ new tools that rapidly turn concepts into reality. An example of this is the company’s 100% polymeric waterproofing system, which is a boon for the industry across the entire supply chain.

Here, we sit down with Stahl’s senior technical manager to discuss the new full polymeric waterproofing technology, Stahl’s commitment and where it strives to be.

Can you describe how the expertise you brought from your 20-plus years at BASF have informed Stahl’s solutions?

Lionel Champanhet: The task is to take the synergies from both worlds and make the best possible solutions. What is special about our approach in polymeric waterproofing leather is that BASF leather waterproofing was the benchmark in the industry since 1977, and that was a big benefit for Stahl.

“In the whole leather chemicals industry, we are the only one to be able to offer waterproofi ng products that are 100% polymeric with no oil inside, or paraffin.”

Then we looked at what were the other synergies and there was a big opportunity to do polymeric leather with a greater range of possibilities and products. From the retanning part and the waterproofing part, we have the optimum because in the whole leather chemicals industry, we are the only one to be able to offer waterproofing products that are 100% polymeric with no oil inside, or paraffin – so we make a cleaner leather.

We also make effluent cleaner because with polymer you have nearly 100% natural uptake by processing, which is not the case with conventional waterproofing where you have paraffin and silicone, which has to be treated. With our new polymeric waterproofing generation we almost have nothing; it is 100% fixed. Also, when you work with paraffin in the drum to make waterproofing, you have to use water that’s 60–65°C. With polymeric, you can use water that is 40–45°C, so the energy consumption and carbon footprint of the factory is greatly improved. Then the drying of the leather is also much faster because you don’t have any oil or paraffin inside. Plus, you save BTUs and drying time, and you can dry at a lower temperature. Then, because you don’t have oil, you don’t need to wash as much, so you don’t have as much float, so you use less energy and a shorter running time on the drum, which can take a long time to empty and refill if there is paraffin involved. This is the way we see the future, and with the BASF and Stahl synergies we can do a big range of leathers and waterproofing for garments, bags and shoes.

What adjustments were necessary and how did Stahl meet these challenges?

Tanneries don’t have to change any of their equipment; they can use the same processes. They just have to change the chemicals and adjust the water temperatures, running times and drying. So the most difficult part was because we don’t use conventional syntan powder in this full polymeric process, so where we struggled a bit was the dye penetration.

“There is a significant positive impact on the productivity and production costs of a tannery using a 100% polymeric solution.”

This is where we have to be careful and where we focus when we run trial projects for the customer. We put all our attention on the dye selection to get it through. The polymeric re-tanning that is used does require more attention, because the dyes react stronger to such substrates compared to more conventional leathers re-tanned with synthetic tanning agents, vegetable extracts and auxiliaries. With full polymer, we have to take greater care of dyeing.

On the other side, because we don’t use syntan or veg extract, we have more brilliant, bright and clean colours because we don’t have the colour shift due to the vegetable extract that changes the purity of the colours. So there are points you have to address and adjust, but I have been working with this for nearly three years and see great positives, including better tensile strength. The waterproof performance is also very good and customers are very pleased.

In terms of humidity, you don’t see whitish mould coming out, so it is cleaner. So in certain climates, this helps to keep footwear cleaner for longer. With one customer, we sold the polymeric system because they had major salt-migration complaints from shoe brands. Now, even with nubuck, in a 100% polymeric system, there is no salt migration.

Can you explore possibilities knowing that you are unique in the market, or are you vigilant of competition?

This is what tanneries that have been doing waterproofing for decades have been striving for – to have a cleaner leather, less rejection, because if you have a product with paraffin you always have the risk of instability of emulsions, which is normal because if you don’t have instability you don’t have waterproofing since you have to break the stability to become waterproof. So you can’t make it too stable. So when you break that stability, then you have the risk of oil staining or oily surfaces. So tanneries have been wanting to eliminate this rejection. With polymer, you don’t have that, so this is very interesting for customers and it gives Stahl an edge on the competition.

Can you explain what exactly the polymer is?

The polymer waterproofing reacts with the leather fibres; as you run the process, it self-exhausts. You don’t have to bring excess water like when you use paraffin or acid to trigger the fixing. With the polymer, if you run the fatliquoring step, and after two hours, the self-exhaustion is at 95%. So when we bring in 40°C or 45°C temperature – plus the standard amount of formic acid at the end of the process to fix the dye – then the exhaustion is complete, and because of that we have the guarantee that it is repeatable. How we measure that is by the BOD or COD, and then the tanneries measure their effluent and they find that the load of the raw effluent is much less.

What are the added costs of going 100% polymeric?

There is a significant positive impact on the productivity and production costs of a tannery using a 100% polymeric solution. Drums can be filled earlier and faster. We are very close to the customer, to conduct trials and audits to assure their waterproof performance. Our ongoing mission is to deliver solutions. Although I am an expert, I don’t spend more than two weeks without doing a trial of the same leather and the same colour for the same customer. I have been doing this for 30 years.

Moving forward we are continuing and targeting to deliver the highest quality standards as Stahl and to be promptly available with technical service and advice for our valued customers.



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