Diisocyanates: The 0.1 % limit
Why does the EU want to regulate the processing and handling of diisocyanates in the polyurethane industry?
Joachim Petzoldt: In 2012, the German Federal Institute for Occupational Safety and Health (Bundesanstalt für Arbeitsschutz und Arbeitsmedizin) looked at monomeric diisocyanates as substances that can have a respiratory or skin sensitising effect if appropriate protective measures are not adhered to. Although the number of corresponding occupational illnesses has been declining for years, for example in Germany, the German and later the European REACH authorities saw a need for action. Of course, Covestro and other manufacturers also have a keen interest in ensuring that diisocyanates are handled responsibly.
I would like to emphasise in particular that handling cured polyurethane products such as coatings or adhesives does not lead to respiratory or skin diseases. Only reactive polyurethane raw materials can cause such diseases if they are handled improperly.
REACH has several tools to protect human health and the environment. In the case of diisocyanates, the issue concerns a restriction, not a conceivable authorisation (approval). What’s the significance of that?
Dr Joachim Petzoldt
Petzoldt: The authorisation procedure is used for substances of very high concern (SVHC). Such substances must not be used for the time being. Applicants must convince ECHA that the risks of the chemical are under control and that the socio-economic benefits of its use outweigh the risks. However, even if ECHA subsequently approves the chemical, it is approved on a temporary basis and subject to the proviso that the substance in question is gradually replaced by alternatives. Nevertheless, ECHA has not classified diisocyanates as being of very high concern but has only established certain requirements for handling and use. It has thus chosen the instrument of restriction which is also supported by diisocyanate producers and the PU industry.
What restriction is planned for diisocyanates?
Petzoldt: Basically, only trained personnel will be allowed to handle diisocyanates. Consequently, anyone working with PU hardeners whose residual monomer content of free monomeric diisocyanates is greater than 0.1 % by weight must be trained. Trained employees receive a Europe-wide certificate that is valid for four years. After that, the respective employee must participate in a training course again. With this restriction, the authorities are imposing responsibility on the entire PU industry. What is already required in the chemical industry – in Germany via the Hazardous Substances Ordinance and in other European countries via similar laws – is now being extended to the entire supply chain.
Are there no exceptions to the 0.1 % rule?
Petzoldt: In principle, yes. An applicant will then have to prove to the authorities, on an application-specific basis, that the product in question with a free diisocyanate content of over 0.1 percent poses no hazard in the process. A possible example could be the repair of small defects in windscreens using a 2K PU adhesive applied with a double cartridge. The risk of diisocyanate exposure is very low. On the other hand, it will be impossible to obtain an exemption for the spray application of 2K PU systems, for example.
When will the restriction start to apply?
Petzoldt: We assume that the EU Commission will issue the restriction somewhere in 2019. The obligation to use only trained personnel when handling diisocyanates will then be subject to a transition period of four years. This means that we expect every employee to be trained by a key date in 2023. The transitional period is imperative because the industry, through its associations, must define the concept and content of the training courses and organise them throughout the EU.
As a major isocyanate producer, how does your company assess the restriction?
Dr Stefan Sommer
Stefan Sommer: We welcome the restriction – mainly for two reasons. First: Covestro stands for the safe handling of hazardous substances. In the past, we have been particularly involved in this through the ISOPA and ALIPA associations. One example is the “walk the talk” program, which improves safety behavior in the European PU industry and among professional PU users through training and ongoing dialog.
Secondly, we and the entire industry will benefit from a uniform regulation throughout Europe. Different national occupational health and safety regulations would ultimately hinder free trade and jeopardise the success of PU chemistry without actually increasing occupational safety.
Will it be checked whether the restriction will increase occupational safety?
Petzoldt: Yes. Of course, this can only be assessed in the medium term. Initially, a two-year study is planned, which is intended to examine the situation: Is it feasible and sensible to put together a cohort of several thousand workers who deal with products containing diisocyanates and to accompany it scientifically? If this study is positive, a main study will collect data over five years on exposure levels, protective measures and the number of cases of disease.
Now it seems obvious that the industry is switching to isocyanate-free PU systems. How do you rate these systems?
Sommer: First of all, it has to be said that Covestro also offers such systems. PU dispersions, for example, have no free monomeric diisocyanates because they have already been completely reacted in the reactor under precisely controlled conditions during the production of the dispersions. Thermoactivatable PU hardeners are also free of monomeric diisocyanates. For a number of applications, dispersions or thermo-activatable hardeners are an efficient and often even advantageous alternative.
On the other hand, it must be said that there are many applications in which reactive 2K PU chemistry is clearly superior to other systems in terms of performance. By the way, the Socio-Economic Assessment Committee (SEAC) of the European Chemicals Agency ECHA came to a similar conclusion in the context of preparing the regulation. Besides, I’d like to point out reactive technologies, which are not based on diisocyanate hardeners, are also associated with a certain hazardous substance potential – especially in spray applications, where there is a high probability of exposure of the processor.
PU hardeners with a residual content of less than 0.1 % diisocyanate are not subject to the restriction. Does this make them attractive for processors and users? Sommer: Yes. The authorities are also in favor of such PU hardeners in the context of the restriction. Of course, these hardeners are also hazardous substances which require protective measures as described in the safety data sheets. It is essential that the extremely low values of free diisocyanate monomers do not impair the performance of the hardeners.
Do such PU-hardeners exist?
Sommer: We are constantly working on improving the technical performance of the hardeners and at the same time reducing the residual diisocyanate content. We have a high level of research expenditure and have invested in state-of-the-art production facilities. That is why we have been providing products with a reliable diisocyanate content of less than 0.1 % for almost a year now. These hardeners of the so-called ultra line are already replacing a high-revenue portion of our portfolio because they are at least as effective as the corresponding products with higher diisocyanate contents. We guarantee this to the users.
So will there one day only be products with ultra-low monomer content?
Sommer: We expect that the demand of European coating and adhesive manufacturers for products with a very low monomer content will be considerable. For this reason, we will continue to work on converting products and product lines to ultra-low monomer content. On the other hand, this will not be possible with every PU hardener known today. In such cases it would be necessary to develop completely new ultra-hardeners for the respective applications. Ultimately, it is the market that will decide the extent to which this will happen.