1.Classified by printing method

-Gravure water-based ink

Gravure printing is one of the commonly used methods in flexible packaging printing. Water-based inks for gravure printing are mainly used in this printing method. Its characteristic is that the ink is transferred from the grooves of the gravure cylinder onto the flexible packaging material. The pigments and resins in these inks need to have good transferability to ensure that the ink can accurately be transferred from the grooves during high-speed printing and form clear and fine patterns on the flexible packaging film (such as plastic film). For example, in the printing of high-end food packaging (like the aluminum foil composite packaging of imported chocolates), water-based inks for gravure printing can present exquisite patterns and rich color gradations.

-Flexographic water-based ink

Flexographic printing also holds a certain share in the field of flexible packaging. Flexographic water-based inks have good fluidity and elasticity, and can adapt to the deformation of the elastic printing plates used in flexographic printing. Their viscosity is relatively low, allowing them to better transfer onto various flexible packaging materials during the printing process, such as paper and plastic films. These inks are often used in some flexible packaging products that do not require extremely high precision in patterns but need large-area color printing, such as simple food packaging bags and tissue packaging bags.

-Water-based ink for screen printing

Screen printing can achieve thick ink layer printing. The water-based ink for screen printing can pass through the mesh holes of the screen and form a relatively thick ink layer on the surface of the flexible packaging material. The particle size of this ink is relatively large, and it has good covering power. For example, on some flexible packaging that requires highlighting brand logos or special effects (such as local UV effects), water-based ink for screen printing can well meet the requirements, like some creative gift packaging bags or handmade flexible packaging products.

2. Classified by drying methods

-Natural drying water-based ink

Natural drying water-based inks mainly achieve drying through the natural evaporation of the ink's moisture in the air. These inks are generally used in situations where the printing speed is slow or where the drying time requirement is not strict. For example, in some small-scale manual soft packaging workshops, when printing simple product labels or small batches of soft packaging samples, natural drying water-based inks are more suitable. However, their drying speed is greatly affected by environmental humidity and temperature. In high-humidity environments, the drying time will significantly increase.  

-Thermosetting water-based inks

Thermal curing water-based inks require heating to accelerate the drying process. After printing, the flexible packaging materials will pass through heating devices, such as hot air drying channels or infrared heating equipment, allowing the moisture in the ink to evaporate rapidly. At the same time, the resin components undergo cross-linking reactions, forming a firm ink film. This type of ink is widely used in industrial-scale flexible packaging printing because it can ensure the timely drying of the ink at a high printing speed, thereby improving production efficiency. For example, in the high-speed intaglio printing production line of large food packaging bags, thermal curing water-based inks are a common choice.

-UV-curable water-based ink

UV-curable water-based ink is a relatively new type of ink. When exposed to ultraviolet (UV) rays, the photoinitiator in the ink will trigger the polymerization reaction of the resin, causing the ink to solidify rapidly. This ink dries extremely fast and the cured ink film has excellent properties such as wear resistance and chemical resistance. However, it requires a dedicated UV curing equipment, which makes the cost relatively high. In some printing scenarios where packaging quality is highly demanded, such as for high-end cosmetic soft packaging or electronic product soft packaging, UV-curable water-based ink can demonstrate its advantages and achieve high-quality printing results.

3. Classification by Usage

-Food packaging water-based ink

The water-based ink used for food packaging has extremely high safety requirements. It must comply with strict food packaging hygiene standards and must not contain any harmful substances to the human body, such as heavy metals (lead, mercury, etc.) and harmful organic solvent residues. This ink undergoes strict ingredient screening, and the pigments and additives must ensure that no harmful substances are transferred during contact with food. For example, for printing inside food packaging bags (such as printing product instructions and other contents inside the bag), this highly safe food packaging water-based ink is required.

-Pharmaceutical packaging water-based ink

The water-based ink for pharmaceutical packaging not only needs to ensure safety but also must possess good chemical stability. It needs to prevent chemical reactions with the drugs and be able to maintain the integrity of the printed information on the packaging under certain storage conditions (such as different temperatures and humidity). For example, in the printing of drug bags and drug blister packaging, the water-based ink for pharmaceutical packaging can ensure that the names, dosages, etc. of the drugs are presented clearly and accurately, and will not fade or produce harmful substances during the shelf life of the drugs.

-Water-based ink for ordinary household product packaging

The water-based inks used for packaging common daily necessities mainly focus on printing quality and cost control. They need to provide excellent color representation and adhesion to meet the appearance requirements of daily packaging products (such as shampoo packaging bags, toothpaste boxes, etc.). The composition of this type of ink is relatively flexible and can be adjusted according to different cost requirements while maintaining basic performance. For example, in some daily packaging products with more affordable prices, the water-based inks used may make some compromises in certain performance aspects to reduce costs.

source:https://www.hzdsk.com/news/802.html