Ink Binder (also known as binder or vehicle) is one of the core components of ink, and its performance directly affects the printability, dryness, adhesion and final color rendering effect of ink. As the "skeleton" of ink, the binder mainly plays the following roles in ink:
1. Disperse and carry pigments
Binder is the carrier of pigment, which can uniformly disperse solid pigment particles and stably suspend them in the system to prevent them from aggregation or precipitation. By wetting the surface of the pigment, the binder ensures the uniform transfer of the pigment in the printing process, thus ensuring the color uniformity and saturation of the printed matter. If the dispersion of the binder is insufficient, it may lead to poor ink fluidity or printing color difference.
2. Determine the rheological properties of ink
The viscosity, thixotropy and viscoelasticity of the binder directly affect the fluidity, transferability and printability of the ink. For example, offset printing ink needs a high viscosity binder to avoid emulsification, while gravure printing ink needs a low viscosity binder to quickly fill the net holes. In addition, the leveling of the binder affects the smoothness of the printed surface.
3. Promote ink drying and film formation.
The binder forms a solid film by physical or chemical means to fix the pigment on the surface of the substrate. The drying mechanism includes:
Volatilization and drying (e.g., solvent-based connecting materials are volatilized by solvents);
Oxidative polymerization (such as cross-linking and curing of vegetable oil binder by absorbing oxygen);
UV curing (photosensitive resin polymerizes under ultraviolet light).
The drying speed needs to match the printing process, too fast will lead to plate blocking, too slow will affect the production efficiency.
4. Enhance adhesion and durability
The bonding material should be firmly combined with the printing material (paper, plastic, metal, etc.) to ensure that the imprint is wear-resistant and weather-resistant. For example, plastic printing requires the use of polarity-matched binders to improve adhesion; The binder of food packaging ink also needs to have the characteristics of non-toxicity and migration resistance.
5. Adjust printability and special functions
By adjusting the components of the binder (such as the ratio of resin, solvent and additive), the ink can be endowed with specific properties, such as water resistance, high temperature resistance and gloss. For example, water-based binders are environmentally friendly and suitable for flexographic printing; UV binder can achieve instant drying and high gloss effect.
summary
Ink binder is the key medium to balance the printing process requirements and the quality of printed products, and its selection needs to comprehensively consider pigment characteristics, printing methods, printing materials and environmental requirements. With the strict environmental protection laws and regulations, the development of high performance and low VOC binders has become an industry trend, and the application of new materials such as water-based and bio-based resins is gradually expanding.
