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Towards an interesting biosourced binder for high-performance materials

INRA scientists and their colleagues have explored the mechanisms involved in the formation of covalent bonds between glucose derivatives and waste from the paper industry, or lignosulfonates, during heating in the presence of nitrogen oxide catalysts. These reactions caused the formation of a non-pollutant binder for the manufacture of high-performance materials.

Miscanthus en culture et détail de la morphologie de la plante : feuille.. © INRA, MAITRE Christophe
Updated on 06/19/2017
Published on 05/11/2017

An interesting alternative to fossil energy, plant biomass can also be used to manufacture valuable biosourced products; in recent years, considerable research efforts have recently focused on improvements in biomass quality and the exploration of efficient bioconversion tools. Alongside the cellulose and hemicelluloses in biomass, lignin (a complex, aromatic polymer) displays a broad range of properties that can be of value to the design of environmentally-friendly materials.

So-called industrial lignins are by-products of the fractionation of plant resources, either from delignification during traditional paper-making or from new processes developed in the context of biorefining. In the former case, they mainly arise from the black liquors that result from a bisulfite process used to obtain water-soluble polyphenol polymers because of the presence of numerous sulfonate groups, ammonium lignosulfonates.

 

The formation of homogenous films or webs from non-woven mineral fibres with good mechanical resistance which can, for example, be used as insulation substrates in construction, requires the use of a binder to ensure cohesion of the material. The binders used traditionally in these applications are of the phenol-formaldehyde type and pose the problem of a potential release of toxic substances in the form of volatile organic compounds. Studies by industry have demonstrated that the hot mix of saccharide derivatives and ammonium lignosulfonates, in the presence of nitrogen oxide catalysts, offers a real and non-pollutant alternative to formaldehyde resins.

Research scientists at the Institut Jean-Pierre Bourgin (INRA-AgroParisTech-ELR CNRS), working in collaboration with Saint Gobain Recherche, have explored the chemical mechanisms that underlie the formulation of these binders, evidencing the true originality of this process compared with its chemical counterpart.

Ammonium lignosulfonates and sugars

By using synthetic molecules endowed with the different structural characteristics of ammonium lignosulfonates during heating experiments in the presence of reducing sugars and ammonium phosphate, the scientists were able in particular to use two-dimensional NMR studies to characterise the covalent bonds that formed between the lignosulfonates and a thermal degradation product of glucose, enabling a clear differentiation between this type of resin and those of the phenol-formaldehyde type.

From synthetic molecules to lignosulfonates

Using model molecules, transposition of these studies to lignosulfonates required the development of methods for the analytical monitoring of the transformations undergone by lignosulfonates. Results similar to those obtained using model molecules were also achieved with lignosulfonates.

 

The methodological studies have now been published and this type of formulation is already the subject of patent filings. Study of the influence of the different structural parameters of lignosulfonates, and the type of catalyst, raise hopes that this process can now be optimised.

Find out more

Broussard O., Petit M., Elie N., Baumberger S., Arnaud A., Ducrot P-H., Allais F. Monitoring of free phenol content in lignosulfonates by ClO2 titration and UV difference spectroscopy. Holzforschung 2016, 70, 719.

Patents

  • FR3032197

Composition d'encollage pour laine minérale a base de sel de metal alcalin ou alcalino-terreux d'acide lignosulfonique et d'un composé carbonylé, et produits isolants obtenus.

  • FR3032196

Composition d'encollage pour laine minérale a base de lignosulfonates d'ammonium et d'un composé carbonylé, et produits isolants obtenus.

  • FR3032195

Liant pour fibres minérales a base de sel de métal alcalin ou alcalino-terreux d'acide lignosulfonique et d'un composé carbonylé, et mats obtenus.

  • FR3032194

Liant pour fibres minérales a base de lignosulfonates d'ammonium et d'un composé carbonylé, et mats obtenus.

  • Wo2016120575

Liant pour fibres minérales a base de lignosulfonates et d'un composé carbonylé, et mats obtenus

  • Wo2016120576

Composition d'encollage pour laine minérale a base de lignosulfonates et d'un composé carbonylé, et produits isolants obtenus

Allais Florent, Ducrot Paul-Henri,  Broussard Orianne, Petit Morgane, Silioc Christelle