Polyurethane turf adhesive is a two-component system formed by reacting diisocyante and petroleum-based polyether polyol. This polyol can be replaced by soybean oil as one of the main economical and common oils. In this article, soybean oil was epoxidized followed by oxirane ring-opening in the presence of methyl alcohol and orthophosphoric acid as a catalyst in order to create hydroxyl groups in the soybean oil which are responsible for reaction with the diisocyanate molecules. The epoxidation step was confirmed by ATR-FTIR spectroscopy and iodine value measurements. Iodine value was decreased from 135.6 g/100 g of neat soybean oil to be 5.98 g/100 g of epoxidized soybean oil. In addition, the effect of orthophosphoric acid contents (0.6%, 0.8%, 1.0%, 1.2%) on the ring-opening steps was investigated, considering the same reaction time, the same alcohol concentration and constant temperature. Successful oxirane ring-opening was confirmed by oxirane oxygen content (OOC) values which were decreased from 6.72% to 2.93%, 1.45%, 0.60% & 0.04% respectively. Hydroxyl value of oil-based polyols (OHV) were increased from 131, 180, 208 & 229 mg KOH/g respectively. Meanwhile, ATR-FTIR showed disappearance of the oxirane rings and appearance of hydroxyl groups as indication of polyol formation in the four samples. The four polyol samples were applied as modified natural binders in polyurethane turf adhesive formulations and showed comparable results against the standard and commercially used product SubFix 411.