On February 4, the phthalic anhydride market in Shandong region showed a weak consolidation trend. The mainstream negotiated prices for ortho-xylene-based phthalic anhydride were in the range of 6,000–6,200 yuan/ton, while naphthalene-based phthalic anhydride was quoted at 5,550–5,900 yuan/ton. The price of raw material ortho-xylene remained stable, while industrial naphthalene prices experienced a volatile decline, leading to a reduction in phthalic anhydride production costs. Downstream plasticizer prices also fluctuated downward. Phthalic anhydride production facilities maintained stable operations, with plant operating rates remaining low but steady. Market supply of phthalic anhydride tightened, while plasticizer manufacturers maintained stable operating loads. However, rigid demand support for phthalic anhydride weakened, and the market outlook is expected to continue in a weak consolidation phase.