수성 그라비어 잉크의 누적 증발량에 따른 pH 및 점도 변화의 연구 = Study on pH and Viscosity Changes of Water-based Gravure Inks as a Function of Cumulative Evaporation

다국어 초록 (Multilingual Abstract)

Gravure printing dominates food packaging, yet conventional solvent-borne inks emit VOCs. This study quan- tifies pH and viscosity drift of water-based gravure inks under open-system evaporation using cumulative evaporation (E%) as a state variable. A base ink (S-A1) and two amine-adjusted inks with the same base formulation were examined: S-B1 with ammonia (bp −33°C) and S-B2 with AMP-95 (bp 163-165°C). Samples (350 g) were evaporated at 40°C/40% RH in identical beakers (6.5 cm i.d.) with 650 rpm stirring, and mass loss was recorded to compute E%. After rapid cool- ing and temperature control (25 ± 0.5°C), pH was measured at 0, 30, and 60 s and viscosity at 25°C (120 s, duplicate mean). Stabilization rates in the 30-60 s interval (SR=58.3% and 72.7% at ε=0.05) justified using the 60 s pH value. For S-A1, pH decreased quasi-linearly (slope −0.065 pH/%; r=−0.90) with a three-stage pattern, while viscosity increased (η=55.59+14.04E; r=0.95) and accelerated beyond E≈3%. For S-B1/S-B2, pH followed pH=8.97−0.176E (r=−0.94) and viscosity followed η=65.21+10.33E (r=0.98), with a similar transition near E≈3%. Surface observations indicated aggre- gation/skin at E≈3% and gelation near E≈5%. These results define an E%-based control window and support evaporation- stage correction rules considering amine volatility.