胶印油墨 化学品

Offset ink varnishes are typically rosin-modified phenolic (RMP) alkyd resins dissolved in mineral oil and vegetable oil. Hard-set varnishes use high-molecular-weight RMP resins for rapid setting by oil absorption into the substrate. Gel varnishes based on aluminum octoate-modified linseed or soy oil provide body and tack. Heatset inks use petroleum solvent that evaporates in the dryer tunnel.

Ink tack is measured with an Inkometer and expressed in Tack Units (TU) — typically 12–20 TU for commercial sheet-fed inks at 32°C. Tack determines ink splitting behavior and paper picking resistance. Modifiers such as low-tack varnishes, mineral oils, and phenolic or hydrocarbon resins allow formulators to adjust tack for different printing conditions and substrates.

Vegetable oils (linseed, soy, tung) are renewable, low-VOC vehicles that contribute to oxidative drying in sheet-fed inks. High soy oil content reduces VOC and is preferred for environmental compliance. Mineral (petroleum) oils are the primary carrier in heatset web inks but face restriction in sheetfed inks due to mineral oil migration regulations (EU 2023/2006 and related standards).

Sheet-fed offset inks dry primarily by oxidative polymerization (linseed/soy oil) and ink absorption — drying takes hours to days. Heatset web offset inks dry by solvent evaporation in a 150°C dryer followed by chill rolls — instant drying allows speeds up to 60,000 impressions/hour. Heatset binder is typically rosin-modified hydrocarbon resin in petroleum solvent designed for that drying mode.

Food-safe sheet-fed offset inks use mineral-oil-free (MOSH/MOAH-free) varnishes — typically vegetable-oil and rosin-modified phenolic systems with renewable raw materials. Photoinitiators in UV offset inks for food packaging must comply with the Swiss Ordinance positive list and migration limits. Migration is verified by simulant testing (ethanol, isooctane) per EU Regulation 10/2011 before commercialization.

Process color offset inks use standardized pigments: Pigment Yellow 12/13/14 (diarylide), Pigment Red 57:1 (lithol rubine) for magenta, and Pigment Blue 15:3 (phthalocyanine cyan), with carbon black for K. Spot inks use Pantone color masters with single-pigment formulations for color accuracy. Premium offset inks for cosmetics packaging use lightfast organic pigments rated 7–8 on the wool scale.