Water resistant lignosulphonate-phenol-formaldehyde resin for mineral wool

Mineral wool is a common insulation material, where phenol-formaldehyde (PF) resins are frequently used as binders. Still, the high cost and toxicity of these resins have made phenol alternatives, such as technical lignins, increasingly more attractive. However, they were commonly applied merely as extenders, to reduce the resin’s costs and decrease emissions of toxic chemicals. In the current study, a softwood sodium lignosulphonate sample was used as a direct phenol alternative, considering 20, 30, and 40 %(w/w) substitution rate. A commercial resin formulation, specific for mineral wool, was used as a reference. Successive improvements in the synthesis procedure were performed to improve the performance of the lignosulphonate-phenol-formaldehyde (LPF) resins and enable a significant degree of phenol substitution. The binding performance of the resins was assessed on glass fibre samples, by dry and wet tensile strength testing. For the best-performing formulation, 20 %(w/w) of phenol was substituted by methylolated LS. The methylolation significantly improved the resin’s water resistance. Formaldehyde content was reduced to account for LS’ low reactivity and condensation time was decreased by 70 %, maximizing the resin’s water tolerance. The LPF resin yielded dry and wet performances equivalent to those of the original commercial resin, as well as high water tolerance.