Adhesives containing formaldehyde are, compared to other suitable types of adhesive, extremely economically-priced and are therefore indispensible for the wood-based materials industry in terms of the economical aspect. The reaction requires a surplus of formaldehyde which, in the form of gas, causes undesired emissions both during the production process and from the finished boards
The first step took place at the ISC, where assorted zeolites were compiled and partially synthesised, from which an absorption and/or degradation effect in connection with formaldehyde could be expected. Included in this selection were natural, synthetic and modified zeolites. To this end, a zeolite Y was modified with (3-aminopropyl)-triethoxysilane with the aim of binding the formaldehyde through the formation of a so-called Schiff base (Fig. 1 and 2). Theses zeolites were examined at the WKI, where their ability to bind formaldehyde from the air was compared. A relevant effect was observed for all the zeolites, whereby the synthetic forms – and, in particular, their modifications – proved to be especially effective (Fig. 3). In an initial test, these zeolites were introduced into particle boards, whereby the proportion of zeolites was 5% respectively. The zeolites were thereby interspersed either evenly or in layers. For the fresh samples, a reduction in formaldehyde emission of up to 30% was determined.
In further tests, the effect should be further optimised through variation of both the zeolites and the board production methods. At the end of the current pilot project, practical implementation through project partners from the industry will be pursued. The developed wood-based materials have been registered for a patent under the title “Lignocellulosehaltige Werkstoffe mit geringer Formaldehydabgabe” (Lignocellulose-containing materials with low formaldehyde emission).