Characteristics of glycolysis products of polyurethane foams made with polyhydric alcohol liquefied Cryptomeria japonica wood

Liquefied wood-based polyurethane (PU) foams were made by mixing polyethylene glycol liquefied wood of Cryptomeria japonica with 4,4″-diphenylmethane diisocyanate (PMDI). Glycolysis of PU foams was conducted by using diethylene glycol (DEG), ethylene glycol (EG), and propylene glycol (PG) as solvent with a weight ratio of PU powders to glycol as 0.5/1, 1.0/1, and 1.5/1. The reaction was undergone at 150-190 °C for 140 min in the presence of diethanolamine (DEA) as a catalyst. The effect of reaction conditions on the efficiency of glycolysis was evaluated by the residue content, viscosity, hydroxyl value, molecular weight, and FTIR analysis of the glycolysis products. The results showed DEG, EG, and PG could be used as a solvent for glycolysis. It had the undissolved residue lower than 1%. Both transesterification and thermal decomposition simultaneously occurred during glycolysis, but the relative opportunity was depended on the weight ratio of PU powders to glycol. During glycolysis, the structure of urethane and urea in PU foams were decomposed followed by the formation of new alcohol and amine compounds. To summarize, the best suitable conditions for glycolysis of liquefied wood-based PU foams is conducted in DEG with a weight ratio of 0.5/1, and heated at 190 °C.