REACH Restriction on Diisocyanates: Current Status

TAGS:  Polyurethane Adhesives    

Diisocyanates form the backbone of polyurethane systems. Based on some recent evidence, data analysis and well-known reactivity of diisocyanates, the monomer has been nominated for restriction proposal.

Let's take a look at the reason behind it.

Why the Restriction on Diisocyanates?

Diisocyanates are considered for restriction measures due to the occupational sensitization health effect, they could pose to workers above a certain level of exposure. It is, therefore, a specific use restriction that is envisaged.¹

According to the ecological risk classification of organic substances (ERC), diisocyanates were classified as having a moderate hazard potential owing to a reactive mode of action, and a moderate potential to cause adverse effects on aquatic food webs given its bioaccumulation potential.

The European Commission has classified diisocyanates as a Category 1 respiratory sensitizer (EC 2008). Multiple cases of sensitization to the respiratory tract due to its exposure in occupational settings, including spray painting and polyurethane production, have also been reported - as cited by OCED 2006.

Thus, The Committee for Risk Assessment (RAC) and the Committee for Socio-economic Analysis (SEAC) agreed to restrict the use of diisocyanates at the workplace.

Although, it will take some time to bring the restriction in action.



The main goal is to prevent new cases of occupational asthma from exposure to diisocyanates among industrial workers and professionals.

Discussion on Safe Use of PU at FEICA 2017

FEICA and its members are continually working with all actors in the polyurethane value chain to improve the safe use of PU products and support this restriction as a harmonized solution across Europe.

In the event held last year, specific working groups comprising of FEICA members discussed at length on the upcoming REACH restriction on diisocyanate. Currently, an exception to this restriction exists for PU systems with monomer (diisocyanate) content less than 0.1%. Also, sealants might be outside the purview of restriction as of now.



Some presentations were made on this topic and here are some of the main highlights.

Formulations with Reduced or Eliminated Monomeric Content

Dr. Christoph Thiebes from Covestro gave a technical presentation discussing the possible solutions and way ahead. The approach he presented involved lowering the monomeric content to less than 0.1% and / or eliminating it. Removal of the monomers means high efforts but this has been proved feasible.



Also, he mentioned that ‘No’ monomer systems are also possible with different performance.

Polyurethane Dispersions	Combine high molecular weight & low viscosity
Thermolatent PU	1K systems with 2K properties by heat activation
Carbodiimide Crosslinking	High pot-life and high reactivity
Silane-terminated PU	Hybrid - best of both worlds

He also talked about their new bio-based building block - pentamethylene diisocyanate (launched at ECS 2015). He expects bio-based MDI to be a commercial reality by 2025.

Isocyanate-free Approach - NIPU

The solution Dr. Frédéric Simons from Bostik talked about was that of Non-isocyanate Polyurethanes (NIPU).



Sustainable routes to NIPU involve the use of renewable natural oil polyols (NOPs). The main advantage is that renewable triglycerides (main feedstock) are available in nature in abundance. But the disadvantage is that the molar mass, dictated by natural oil, cannot be fine-tuned. This restricts the range of properties and thus, applications.

Using Arkema’s expertise, Bostik used the metathesis reaction. Their strategy involves synthesizing a,ω-di(glycerol carbonate) telechelic polyesters as the 1st step. Further on reaction with a di or triamine in a polyaddition reaction, they provide polyhydroxyurethanes (PHU). As per tests conducted by Bostik, the properties are comparable or superior to standard PU 2-components adhesives.

The concept is lab ready and opens doors to new materials in the CAS industry. A scale-up with Arkema is planned and they will first start testing with specific customers.

Conclusion

Considering the long-term commitment to PU adhesives, adhesives and sealants industry is convinced that PU products can be handled safely in industrial and professional applications if the recommendations in the safety data sheets are followed.

FEICA acknowledges that diisocyanate producers (Manufacturers/Importers), representing the industry at the start of the chain, should bear the main legal responsibilities and guidance role for the entire process.

FEICA members support a fair sharing of responsibilities and strong collaboration between all actors of the value chain for the preparation of training content.