Ink Binder is one of the core components of ink. Its main function is to disperse pigments, endow ink with fluidity, and form a uniform film layer after printing, ensuring that the pigments firmly adhere to the surface of the substrate. The material and performance of the binder directly affect key indicators of the ink such as printability, drying speed, gloss and durability. The following are the main material classifications and characteristics of ink binders:
1. Plant oil-based binder
Drying oils: such as flaxseed oil, tung oil and dehydrated castor oil, are rich in unsaturated fatty acids and can be dried through oxidation polymerization. This type of oil is often used in traditional offset printing inks. It dries slowly but forms a flexible film.
Semi-drying oils: such as soybean oil and sunflower oil, have a relatively slow oxidation rate and need to be mixed with other resins to improve their performance.
Modified vegetable oils: Enhance drying speed and film hardness through chemical treatments (such as ester exchange and polymerization), for instance, polymerized linseed oil.
2. Resin-based binder
Natural resins such as rosin and shellac are less used due to performance limitations, but rosin derivatives (such as maleic acid-modified rosin) are still used in some gravure printing inks.
Synthetic resin
Phenolic resin: It has strong water resistance and adhesion and is often used in offset printing inks.
Acrylic resin: The main component of UV curing (UV ink), it dries quickly and is environmentally friendly.
Hydrocarbon resins: Good compatibility with solvents, used in gravure and flexographic printing inks.
3. Solvent-based binder
It is made by dissolving resin in organic solvents (such as toluene, ethanol, esters), and the drying method is solvent evaporation. It is commonly found in gravure and flexographic printing inks, but its use is restricted by environmental regulations.
4. Water-based binder
With water as the dispersion medium and in combination with acrylic or polyurethane emulsion, it is environmentally friendly and non-toxic, and is used in flexographic and inkjet inks. Drying requires heating to evaporate moisture, and the film-forming performance depends on the resin design.
5. Other special binders
Uv-curable resins: such as epoxy acrylate, are instantly cured under ultraviolet light by photoinitiators, with no solvent emissions.
Silicone resin: High-temperature resistant, suitable for special printing scenarios.
Summary
The selection of binder should take into account the printing process, the type of substrate and environmental protection requirements comprehensively. For instance, offset printing inks mostly use a mixed system of plant oil and resin, while packaging inks tend to be water-based or UV systems to meet environmental protection standards. The future development trend is to develop high-performance bio-based resins and low-energy consumption curing technologies to balance functionality and sustainability.
