Application of Subcritical Water Hydrolysate from Thermosetting Polyester Resin to Aqueous Agents

Thermosetting polyester resin used in fiber reinforced plastic (FRP) is very difficult to be recycled since it cannot be re-molded like thermoplastic resin. In recycling thermosetting polyester resin, subcritical water with alkali was applied to hydrolyze ester bonds to obtain styrene-fumaric acid copolymer (SFC). SFC, subcritical water hydrolysate from thermosetting polyester resin, has a molecular structure of functional polymer. Alkali salt of the SFC has a same molecular structure as alkali salt of styrene-maleic anhydride copolymer (SMA) which is widely used in various kinds of high performance additives for aqueous applications. In these applications, dispersing agent, detergent builder, and surface sizing agent were selected for application of alkali salt of the SFC . The reaction product liquid contains sodium salt of SFC (SFC-Na). It was evaluated as dispersing agent and detergent builder. Ammonium salt of SFC (SFC-NH4) was evaluated as surface sizing agent for paper. The evaluation results were compared with that of commercial additives to verify the possibility to substitute them. The reaction product liquid showed superior dispersing effect to commercial dispersing agent for hydrophobic powder. It also showed superior alkali buffering capacity to commercial detergent builder. SFC-NH4 showed higher sizing effect than commercial sizing agent.