According to Maier, the chemical industry has by no means exhausted its potential. The latest developments even show that it is possible to improve fastness properties without sacrificing the natural qualities of the leather.
Q The automotive industry is constantly increasing its requirements on upholstery leather. How are tanners and seat manufacturers expected to keep pace?
A It’s certainly not easy for them, because not only have the demands made on the physical fastness properties increased significantly worldwide over the past years, they have also become much more diversified. Each individual car manufacturer has his own set of requirements and that naturally means a whole raft of different test procedures and performance specifications.
The only way tanners and seat manufacturers can fulfill all these demands is by keeping their eyes open, staying abreast of technological developments and insisting that their suppliers and partners in the chemical industry do likewise. However, the new developments we have in the pipeline at LANXESS mean we should have no problem satisfying the demands of the automotive leather market today and also tomorrow. The chemical industry has by no means exhausted its potential.
Q Why are there regional differences?
A There are various reasons. For example, US manufacturers react quite differently from their European counterparts to minor defects and the resultant complaints – often by replacing the entire seat. And of course corporate philosophies differ too. One major Asian car manufacturer, for example, tests leather seats at -40°C, even though only a fraction of the vehicles will be exposed to such low temperatures.
If coatings have a tendency to develop hairline cracks under these conditions, they are rejected. But there are solutions to all these problems. Our low-temperature-resistant coatings based on Bayderm DLV-N or Bayderm Bottom CTR, for example, display good fastness properties at particularly low temperatures. And there will be more developments shortly!
Q Are you referring to your sales and research agreements with Rohm and Haas in the United States?
A Exactly! We carry out joint research with Rohm and Haas on some products. In this way we can pool our complementary strengths. Our partner handles the acrylate side, while we concentrate more on the polyurethane business. Together, our portfolio of poly- urethanes and Rohm and Haas’s highly developed acrylate chemistry make an outstanding combination.
Over the past few years, this cooperation has led to the development of products with performance properties that would have been unthinkable ten years ago: Primal SB-300, for example, or Hydrholac CL-1. These are acrylates with excellent cold resistance that we now use in coatings that require good low temperature flexibility. A particularly interesting advantage of this partnership is that, by using acrylates, we are better positioned to combat the price pressure on OEMs today.
Q You mentioned the regional differences in the requirements of automotive OEMs. What exactly are these requirements?
A Firstly we have the rub fastness tests that are required, especially in Europe. These tests involve rubbing a weighted piece of white felt repeatedly over the leather surface. The coating must not visibly stain the felt. One major German manufacturer of top-of-the-range limousines stipulates 300 cycles, while another now specifies 1,000 cycles wet on wet, ie on wetted leather.
By comparison, 50 to 200 wet cycles are considered sufficient for furniture upholstery leather! The flex resistance is also very important. 100,000 flexes on the Bally flexometer at room temperature – and 10,000 at -30°C – are standard and feasible.
American and Asian manufacturers also demand dry rub fastness tests such as the Taber test, which is also used for testing the scratch resistance of kitchen work surfaces. Here, too, the requirements differ widely.
The required abrasiveness of the Taber wheels ranges from CS-10 to H-18, while the number of revolutions may be anything from 300 in five minutes to 800 in the case of ‘high-wear’ specifications. Such fastness requirements would have been unthinkable even a few years ago yet, today, we can satisfy the needs of the market without any problem. And our share of the market is growing all the time.
Then there is the hydrolysis resistance. Leather must now be able to withstand exposure to heat and moisture for twenty days – it used to be seven. To test the fastness to heat and yellowing, leather is now placed in an oven at 120°C for seven days. When it comes to measuring the flexibility, most OEMs use the Bally flexometer or Newark flex but, here too, there are individual differences. Some are happy with -10°C, while others insist on -30°C. The Asian manufacturer I mentioned earlier, for example, uses the cold impact method, in which a metal pin is shot onto leather which has been cooled to -40°C.
Q Who, in your opinion, makes the toughest demands?
A It’s difficult to say. Perhaps people here in Europe attach more importance to good breathability. But that doesn’t mean that the demands in Europe are less stringent. After all, exports to the United States are one of the mainstays of business for European OEMs. It’s simply that the criteria used for assessing leather vary from one region to another. On the whole, however, the required standard is comparable worldwide and extremely high.
That’s not a problem for us and our customers. LANXESS has leather experts all over the world and laboratories almost everywhere – for example, in Brazil, Argentina, China, Italy and Germany – which our technical advisors can use. In Leverkusen alone, we recently invested a considerable amount in expanding the physical testing laboratory where we can carry out all the tests required by the various OEMs on equipment bought specifically for that purpose.
It is used not just to test our own recipes but to help our partners meet, as far as possible, all the different requirements in the relevant market. So in addition to supplying chemistry and know-how, we also offer ‘tested reliability’, which safeguards our customers and ourselves against complaints. After all, a ‘field failure’ in the automotive sector can cost millions.
Q Are products that have these fastness properties still ‘leather’? Are the demands not excessive?
A Good question. The secret is to give the surface these extreme fastness properties without sacrificing the typical properties that people look for in leather. But why shouldn’t manufacturers demand maximum values? We’re not here to take issue with new requirements but to satisfy the wishes of our customers. We grow with challenges. So far we have always managed to keep pace and we and our customers will continue to do so in the future, too.
Q You mentioned furniture upholstery leather. Do other sectors also benefit from the demands of the automotive industry? Or to put it another way: are there synergies in a company with such an extensive portfolio as LANXESS?
A In my opinion, it’s not so much a question of whether our automotive experts can learn from the furniture people – although naturally they can – as a question of whether the leather experts and the chemists who are responsible for developing the coatings generally understand one another. Because after all, these coatings often involve highly sophisticated chemical processes and only outstanding chemists are capable of working out the recipes and conditions which will ensure that our coatings give optimal results.
At the same time, leather technologists sometimes use a language of their own which the chemists have to be able to understand and interpret. For this reason, we at LANXESS use experienced leather experts who have got to know our customers over the years and are able to tell the chemists in the development laboratory precisely what is required, what is important and what isn’t. That is to say: we always tailor our products exactly to our customers’ needs and not vice versa! We respond to the challenges that the market presents us with.
The problems that arise in the various sectors are often very similar. Take, for example, the methods and processes for concealing grain defects in leather coating. The rule of thumb is that the poorer the quality of the raw material, the more important it is to apply a good finish. Nobody wants to see pinholes, insect bites or cracks.
For some time now, we at LANXESS have been using expanding microcapsules to tackle this kind of problem, with outstanding results. It wasn’t easy to transfer this technology to automotive leather because of the required fastness properties in this sector. However, with our X-Grade system we have been able to achieve amazing results.
This system does not consist of classical foams but of special microcapsules that expand to 40 times their size under the influence of heat – for example, during plating or embossing – and reliably fill the defective areas. In this way, the proportion of full grain leather that can be utilised is significantly increased and there is less wastage.
At the same time, the print retention and uniformity are improved. And as the walls of the X-Grade microcapsules are considerably more robust than the pores of a foam, it is possible to obtain much better fastness properties with this system. For all these reasons, X-Grade is proving highly successful – and not just in the furniture industry but in the automotive sector as well.
Q Can you give us any more examples of innovative developments?
A Yes. Over the past few years, we have, for example, succeeded in reducing the VOC emissions (Volatile Organic Compounds) of finished leathers by a substantial amount.
The emission levels we have today would have been unimaginable in the past! And there is still plenty of room for improvement. As you know, the crosslinking agents that are indispensable in many coatings are still solvent-based but we are currently working on 100% products that function without these volatile components. The initial results are extremely promising!
Q What challenges lie ahead?
A There is a pronounced tendency towards pale leathers in the automotive sector: pale gray, pale beige, pastel colours, even white. These are the colours that customers will be asking for in the coming years.
Q What are the implications of this trend for leather processing?
A In addition to outstanding resistance to yellowing even on long-term exposure to intensive sunlight, which can be achieved today by using aliphatic polyurethanes for example, these leathers will naturally also have to have excellent anti-soiling properties. This is especially true in the case of matt surfaces – which incidentally are currently more popular in Europe than they are in the United States, where people tend to go more for shiny surfaces.
Obviously, the paler the leather, the more susceptible the top coat is to staining and soiling. Unfortunately, there is as yet no uniform test method that is used worldwide for measuring the degree of staining. There are some useful tests, however, such as the dye ingress test, which is based on test methods used in the textile industry and carried out on Martindale test equipment.
In this test, a piece of denim fabric impregnated with alkaline perspiration solution is rubbed repeatedly over a leather surface. The degree of staining is then measured. This test is used by some manufacturers of top-of-the-range cars.
At this point I would like to mention – not without a certain amount of pride – that through its close cooperation with Rohm and Haas LANXESS can offer a viable solution to the staining problem in the form of a fully acrylic top coat system for automotive leathers – as far as we know the only such system available to date – that meets the demands of the dye ingress test as stipulated by the Ford Group. The combination of Hydrholac AD-1, Hydrholac CL-1 and the new development Opti-Matt A-1000 gives light-coloured leather finishes with outstanding anti-soiling properties.
Q Can you tell us more?
A Gladly – although unfortunately I can’t reveal too much at this stage. I can say, however, that the special feature of Hydrholac AD-1 – AD stands for acrylic dull – is not so much the fact that it can be used to adjust the gloss level of the coating, as the fact that, by combining it with Opti-Matt A-1000, it is possible to obtain a matt finish with a reduced amount of silicate, or even without using silicate at all. Our colleagues at Rohm and Haas have succeeded in producing the refractive effect that is responsible for the matt surface appearance without silicate. This system, too, involves highly sophisticated chemical and process engineering that you probably won’t find so easily elsewhere.
Q What are the benefits of doing without silicate?
A Firstly, silicate-free acrylates have excellent anti-soiling properties, which makes them ideal for light-coloured leathers. But they also have another special advantage and that is the fact that leathers coated with these products ‘creak’ noticeably less than most conventional coatings.
Q Why is that?
A It’s quite simple, really. The unpleasant and undesirable creaking noises are caused by the rough-surfaced silicate particles becoming entangled and rubbing against one another when the leather moves. As we now use less silicate, there is less creaking. So leathers treated with Hydrholac AD-1 and Opti-Matt A-1000 perform quite differently in the slip-stick test.
And together with Rohm and Haas we are constantly working on improving the technology. We also hope to introduce a silicate-free polyurethane matting agent and a new, innovative anti-soiling system onto the market in the near future, so that we can really satisfy all the demands made on us and our customers.
Q So leather has a future?
A Absolutely! There’s still plenty of scope for development. Products such as the ones I just mentioned show that the constant further development of technology on behalf of our customers can help to make leather increasingly robust and meet market requirements, while still preserving the natural character of the oldest material in the world. As a devoted fan of leather, I am particularly pleased about that.
Rodger Maier can be contacted at rodgermaier@lanxess.com
