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A safer alternative replacement for thiourea accelerators in the production process of chloroprene rubber.

Thanks to their balance of cure rate, scorch and physical properties,  thiourea based accelerators have hitherto represented the best cure system for chloroprene rubber. The problem is their inherent toxicity. Now the SafeRubber project has identified an alternative accelerator.

Thiourea based accelerators are used in the vulcanisation of polychloroprene rubber, primarily ethylene thiourea (ETU). To date they have been proven to produce the highest performance rubber cure system. However, ETU is inherently toxic, being classed as a Category 2 carcinogen by the EU  classification, IARC and EPA.

Objectives

The SafeRubberprojectaims to develop a safer altrnative accelerator to replace the carcinogenic ethylene thiourea(ETU) baseda.ccelerators to be used in themanufacturingofrubbers such as polychloroprene (CR) and epichlorobydrin (ECO).

CMR substance

Under the REACH regulation, it is believed that such accelerators will be classified as a CMR substance (Carcinogenic/Mutagenic/toxic for Reproduction). This is likely to lead to a statutory ban on its use, which would have a serious impact on the rubber industry. »

Reduced competitiveness

An additional problem is that as Asian countries do not have to meet EU Health and Safety regulations, they enjoy a lower cost base. They export over €80 million of chloroprene rubber in to the EC per annum, and a ban on the use of ETU in the EU could further reduce the competitiveness of  the EU SME members.

New and safe

The synthetic rubber processing sector consists of over 6,000 SMEs, employing over 360,000 people and turning over €3.2 billion within Europe. Working on behalf of the sector, the SafeRubber project had one simple aim: to develop a new, safer, multifunctional curing molecule which can replace thiourea-based accelerators in the  vulcanisation process.

Problem overcome

While there is virtually no risk from ETU in the finished product, dust and volatiles created during processing is where the harmful effects are created. This is particularly so during the curing cycle. Based on the fact that the dust problem can be eliminated by using a polymer bound dispersion, and backed byfunding of over €2 million from the EU FP7 programme, the SafeRubber project  has been developing a safe alternative.

Chemical mechanism

Initially, the SafeRubber project concentrated on the chemical mechanism of the vulcanisation of polychloroprene. This enabled the consortium to design 12 alternative molecules which, by applying Quantitative Structure Activity Relationship (QSAR) evaluation techniques, were expected to be  safer than ETU.

These tests resulted in two suitable  accelerator molecules being identified that have curing  characteristics similar to ETU- one of these has been selected for scaling up to an industrial process.

Companies involved

  • Associaziane Nazionale Costruttoridi Macchine E Stampi Per Materie Plastiche E Gomma
  • European Tyre and Rubber Manufacturers´Association
  • Mgn Transformanciones Del Caucho SA
  • Universita´Degli Studi Di Milano-Bicocca
  • The UK Materials Technology Research Institute Limited (A Pera Technology Company)
  • Robinson Brothers Limited
  • Grand Synthesis
  • Association Des Producreurs D´articles En Matieres Plastiques Et Elstomeres ASBL
  • Clwyd Compunders Limited
  • Norner AS
  • Mixer SPA
  • Norner Innovation AS

Funding

Seventh Framework Progranune (FP7)