Water-Based Gravure Inks for Paper

Executive summary

Paper gravure — gift wrap, paper bags, wallpaper, laminates for furniture and flooring, cigarette and confectionery wraps — was the first gravure segment to go water-based, and it remains the segment where water-based inks deliver the best combination of speed, quality and cost. This paper reviews the demands of high-speed paper gravure, the formulation of the UniLux water-based gravure ink range, and the increasingly important question of what happens to the printed paper at end of life.

1. The paper gravure brief

Paper gravure runs fast — 200 to 400 m/min on wide webs — on absorbent, sometimes rough substrates, and the printed product is handled hard: bags are filled and carried, wrap is folded and taped, decor paper is impregnated with resin and pressed at 150 °C. The ink must dry instantly, hold colour strength on an absorbent surface, resist rub and scuff, and for decor paper survive melamine impregnation without bleeding. Water-based inks meet this brief naturally: the water carrier is absorbed as well as evaporated, so drying is faster on paper than on film, and the absence of solvent makes the printed paper odour-free for food wraps and safe for children’s products.

2. Formulation principles

Binder. UniLux inks are built on a blend of alkali-soluble acrylic resin, which gives resolubility on the cylinder and gloss, and acrylic emulsion polymer, which gives rub resistance and water resistance once the amine has left the film. The ratio is set per grade: more resin for high-gloss gift wrap, more emulsion for bags and wraps that are handled wet.

Pigments. Colour strength on absorbent paper is protected by dispersing pigments at high concentration in resin-bearing grinding bases; the ink then holds out on the surface rather than soaking in. Light-fastness grades from BWS 3 (short-life promotional wrap) to BWS 7 – 8 (decor and outdoor bags) are available across the palette.

Rub and slip. Wax dispersions and slip agents migrate to the surface during drying and give the dry-rub and wet-rub resistance that bag handling demands; grades for decor paper are formulated without them so that the melamine resin wets the print.

pH and stability. A volatile amine keeps the ink at pH 8.5 – 9.0 on press; a pH stabiliser is supplied for long runs and hot pressrooms, where amine loss would otherwise raise viscosity and reduce resolubility.

Figure 1 – Resin / emulsion ratio: the resolubility–rub resistance trade-off tuned per grade (illustrative).

3. Running water-based ink on a paper gravure press

Cylinders: engrave 15 – 25 % shallower than for solvent inks; 70 – 100 lines/cm electro-mechanical or laser engraving.

Viscosity: 16 – 20 s (Zahn 2) at 25 °C; reduce with water or the recommended water/alcohol reducer.

Drying: 60 – 90 °C impingement air; the more absorbent the paper, the lower the temperature needed.

Doctor blade: water-based inks are slightly more abrasive than solvent; use coated steel blades and check wear.

Press hygiene: flush the system with water on shutdown and clean cylinders before ink dries in the cells; dried water-based ink needs an alkaline cleaner.

4. Decor paper: the special case

Decor paper for laminate flooring, furniture and doors is printed with wood grain or unicolour designs, then impregnated with melamine-formaldehyde resin and pressed. The ink must be transparent enough to let the resin penetrate, colour-fast under 150 °C pressing, resistant to the resin’s acidity and to light for the life of a floor. UniLux decor grades use inorganic and high-performance organic pigments with BWS 7 – 8, binders that leave the fibre open to impregnation, and no waxes.

Figure 2 – EPRC de-inkability scores: water-based acrylic gravure ink against UV systems (illustrative).

5. End of life: de-inkability

Paper’s environmental advantage depends on it being recycled, and recycling depends on the ink being removed by flotation de-inking. Water-based gravure inks with acrylic binders generally de-ink well: the alkaline pulper redissolves the binder, the pigment particles are released at a size the flotation cells capture, and the recycled pulp reaches the brightness paper mills require. Tests to the INGEDE Method 11 protocol and the EPRC de-inkability scorecard confirm this for the UniLux range on standard papers. As the EU Packaging and Packaging Waste Regulation moves recyclability from a preference to a requirement, de-inkability data is becoming part of the ink specification.

6. The UniLux range

UniLux comprises gift-wrap and publication gravure inks (high gloss, fast drying), bag and wrap inks (high rub resistance, food-wrap odour-free), decor-paper inks (high light-fastness, impregnation-compatible), and cigarette and confectionery inner-wrap inks (low odour, low migration), with extenders, reducers, pH stabiliser, defoamer and wax additive. Colours are matched in our laboratory to customer standards and supplied with technical data sheets covering engraving, viscosity, drying, resistance and de-inking data.

Key takeaways

Water-based gravure on paper is faster, not slower, than solvent because the paper absorbs the carrier.

Binder balance sets the trade-off between resolubility and rub resistance and is tuned per end use.

Decor paper needs transparency, heat and light-fastness, and no waxes.

De-inkability is measurable, and water-based acrylic inks score well.

References: INGEDE Method 11; EPRC De-inkability Scorecard; ISO 105-B02 (light fastness); DIN 16524 / ISO 2836 (resistance of prints).