Chemical reaction

Recently-introduced EU legislation and industry-led initiatives aim to help adhesives manufacturers produce safer alternatives for us and the environment. Julia Pierce reports


In common with other sectors, the adhesives industry is coming under increasing pressure to become more environmentally friendly.

The introduction this month of the EU’s Registration, Evaluation and Authorisation of Chemicals (REACH) regulation aims to improve the protection of our health and the environment through the better and earlier identification of the properties of chemical substances.

Under REACH, manufacturers are required to register the properties of substances used in adhesives on a central database. The regulation also calls for the progressive substitution of the most dangerous chemicals when suitable alternatives have been identified.

‘The purpose of the regulation is to protect both the end users and workers,’ explained Bernard Ghyoot, secretary-general of FEICA, the Association of European Adhesives Manufacturers. ‘The industry has been taking the initiative itself as well as responding to legislation. We have been reducing the use of solvent-based adhesives with water-based versions and reactive curing systems.’

The new legislation will be a big burden on the industry, and implementation will cost millions of pounds. In September, FEICA will be holding a conference in Brussels, where representatives from the European Parliament and the European Commission will speak on the impact of REACH.

However, Ghyoot said that the results should be positive for all concerned. ‘It will contribute massively to the protection of people and the environment. By making safer products it will be a good way to differentiate ourselves from other industries.

‘We are putting a lot of effort into helping members implement REACH by comparing best practice and analysing standard exposure scenarios to help us understand how the adhesives work in reality,’ added Gyhoot. ‘Green really is the colour of the moment. Some interesting breakthroughs have been made in the use of natural adhesives. However, we know that products containing formaldehydes are not good and I would argue that we must find alternatives to replace these first.’

REACH poses concerns that some raw materials will no longer be produced. Formaldehyde, a suspected carcinogen, is used in a number of adhesive resins, such as for bonding timber in the furniture industry in particular. Bisphenol A, used in the manufacture of epoxy resins and widely used in industries such as aerospace and automotive, may disrupt our hormones and is therefore threatened.

There is also a need to limit emissions from organic solvents, which are detrimental to air quality. But an increasing amount of effort has already been made by the adhesives industry over the past few years to develop low-solvent and solvent-free adhesives. As a result, FEICA says bonding is now responsible for less than three per cent of solvent emissions in Europe.

Other positive changes have also been adopted, showing that the industry is more than capable of adapting and moving forward. Natural-based waterborne adhesives such as starch and dextrin-based substances are now used in the packaging industry. These are low-cost, non-toxic and biodegradable. But they are not suitable for all applications.

The use of stronger thermoset resins is now coming under scrutiny, and is where important developments are being made. Around 350,000 tonnes of such resins are used each year in the construction, furniture and automotive industries.

At present all the raw materials are derived from petrochemicals, but by replacing them with a new generation of ‘bio-resins’, manufacturers will be able to meet tighter environmental regulations in a commercially viable way.

Researchers at Bangor University’s Biocomposites Centre (BC) have been working with industry to develop adhesives and resins from plant oils such as rape, soya, sunflower and cashew nut shell liquid. These thermosetting bioresins could be used to glue timber panels and the fibre-reinforced composites that are increasingly being used by the automotive and aerospace industries to reduce weight.

The products have been found to have comparable, and in some cases improved, bond strengths compared to traditional formaldehyde resins.

In the project, known as REPLANT, researchers have worked with contract manufacturer and resin users Cambridge Biopolymers in a scheme supported by the DTI through the Sustainable Technologies Initiative.

The researchers used ozone gas to attack the double bonds present in vegetable oil, turning it into thermosetting resin. Trials demonstrated that the process is capable of working on an industrial scale and commercialisation is expected to follow. The first applications are likely to be in selected insulation products, though the adhesives have potential in industries ranging from electronics to construction materials, foundry and engineered timber products.

‘There is a clear place in the market right now for new, more environmentally friendly resins that are competitive in price and performance, and adaptable to existing processes for manufacturing composites,’ said project manager Dr Paul Fowler. He said an added bonus of a switch to bio-resins would be a cut in carbon emissions as the growing crops absorb greenhouse gases.

‘We’ve succeeded in developing a low effluent manufacturing procedure that’s based on the use of vegetable oil, water, air and electricity and yields formaldehyde-free products with excellent performance characteristics,’ he added.

The project mimics the curing mechanism of the most widely-used synthetic thermosetting resins such as phenol-formaldehyde and melamine- formaldehyde. Treating vegetable oils with ozone gas followed by reduction yields aldehydes that are suitable components for bio-resin formulations.

‘Over the last five years we have been taking the base technology and developing it so that it can be scaled up,’ said Colin Chappell, director of Cambridge Biopolymers.

‘The environmental pull is growing greatly. Customer demands from adhesives used to just be based on cost. Now the market is changing and people want to reduce their carbon footprint.

‘The price is still important, but people will tolerate a small premium for the sake of safety and to create differentiation between their products and others on the market. We have had substantial interest from contract manufacturers.’

Chappell added that in some cases, only part of the adhesive’s petrochemical base may be removed. ‘It is still a move in the right direction, though,’ he said.

By removing dependence on petrochemicals, not only will these adhesives be cleaner and safer — thereby appealing to customers — but the industry will also be less influenced by increased oil prices. This will demonstrate that by making the adhesives sector greener everyone can benefit.

As Chappell explained: ‘There may be two years before we are able to sell the substances in large tonnages, but bio-adhesives are certainly now more than just a research curiosity. We have seen a real change in customer attitudes.’