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A major innovation for the in-depth treatment of timber

After six years of research, researchers in the INRA-INPT-ENSIACET unit in Toulouse, and R&D teams at Lapeyre, have developed a revolutionary treatment for construction timber. The Wood Protect® process, patented by Lapeyre and the INPT, protects timber in-depth against external attack, while endowing it with an unequalled stability and lifespan. This innovative treatment is based on a chemical process which uses natural and non-toxic reagents. It thus naturally forms part of the new high priority objective for research, "green chemistry", which consists in creating more environmentally-friendly chemical products, notably using agricultural resources.

timber for construction. © INRA, CARRERAS Florence
Updated on 04/18/2016
Published on 11/22/2006

Since 1998, researchers in the INRA-INPT-ENSIACET Joint Research Unit for Agro-Industrial Chemistry in Toulouse1 have been working on the treatments applied to construction timber for outdoor use. Although wood is always one of the preferred materials for house construction, it remains particularly vulnerable to attack from the climate or biological agents. After six years of research, INRA and the R&D teams from Lapeyre have designed a chemical treatment which protects the timber in-depth thanks to use of a natural product which is harmless to the environment. It enables the protection of construction timber exposed to the elements but not in contact with the soil, such as shutters.

Hydrophobation of timber

Depending on the species, wood is made up of 40% to 50% cellulose, 25% to 30% hemicellulose and 20% lignin, and is thus particularly sensitive to moisture, rot fungi and xylophagous insects.
The researchers have developed a mixed anhydride-based treatment obtained by a chemical reaction between rapeseed or sunflower seed oil derivatives (fatty acids) and acetic anhydride. This product acts by "chemical grafting", because the mixed anhydride binds to the cellulose fibres. The wood is thus protected from moisture and outside attack, and no longer requires maintenance.
Impregnation of the wood with the mixed anhydride involves two stages: firstly in an autoclave, where vacuum and pressure ensure its penetration to the heart of the wood, and then in a tank where the wood is soaked in a bath of anhydride heated to 140°C, to encourage grafting of the product on the wood.

 © Import
© Import

Dimensional stability of wood treated using the WoodProtect® process and after ageing in a climate chamber, or the equivalent of 3 years of extreme external exposure © LAPEYRE

   

Although the hydrophobation of wood by lipid esterification has been known for many years, the agent used until now was highly toxic. The challenge for the researchers was therefore to achieve the same type of chemical reaction using natural, non-pollutant products of agricultural origin. The mixed anhydride obtained is thus a "green" chemical compound: its reaction with wood does not generate any toxic by-products and has been shown to be entirely recyclable.

The specific properties of the Wood Protect® treatment

The Wood Protect® treatment is intended for pine wood shutters, and endows them with protection which is similar to that of the most resistant hardwoods. Treated timber exhibits a high degree of hydrophobicity. This 100% natural treatment has no harmful effects on fauna or flora, and can be handled safely by humans. It protects the timber against the weather for at least ten years.

In terms of industrial use, treated timber does not undergo any dimensional changes and its mechanical properties remain intact. The machining of hydrophobic-treated timber is not affected. Furthermore, the treatment is totally odourless and colourless, and can be applied to all wood species. However, the protection provided by this treatment requires the use of special finishing products. Thus it has been necessary to develop a new range of glues, coatings and preservatives to accompany the marketing of this treated timber.

An example of "green chemistry"

This innovative natural treatment for wood becomes available at a time when new European regulations, or REACH (Registration, Evaluation and Authorisation of Chemicals) are scheduled to be introduced in 2008, and will thus soon prohibit use of the most toxic chemical substances. These regulations aim to better control the use of chemical products in industry and by end-users, and reduce their associated environmental risks.

More generally, these studies reflect the intention to increase research in the field of "green chemistry". They constitute a response to the steady depletion of fossil fuel resources, by profiting from green and white agricultural biotechnologies, in order to replace fossilised carbon chemistry (petrochemicals) with renewable carbon chemistry (agricultural resources). The aim is to develop sparing and clean chemical processes using natural materials in order to reduce (and in the long term eliminate) the need for chemical substances which are dangerous to health and to the environment.
 

Scientific contact:

Elisabeth BORREDON - Tel: +33 5 62 88 56 56 - MarieElisabeth.Borredon@ensiacet.fr

1Joint Research Unit for Agro-Industrial Chemistry  INRA - INPT - ENSIACET (Institut National Polytechnique de Toulouse – Ecole Nationale Supérieure des Ingénieurs en Arts Chimiques Et Technologiques), Science and Process Engineering of Agricultural Products Research Division, INRA Toulouse.