Pigment gives the ink color characteristics, meet the printing requirements of color.General organic pigments and inorganic pigments can be used for water-based ink.As a result of water-based ink resin is mostly alkali soluble, so the choice of pigments, must be able to use alkaline pigments.However, the distribution of pigment density in ink than solvent inks are much larger, and the surface tension and polarity of water and solvents are different, making it difficult to disperse pigment, directly affect the stability of ink, viscosity and pH value.Surfactant can increase the affinity of resin and water and the affinity of pigment and water-soluble binder, so as to solve the problem of ink stability.The viscosity and pH value of water-based printing inks need to be precisely controlled.When the pH value is higher than 9.5, alkaline too strong, the viscosity of the ink will reduce, drying speed becomes slow, water resistance becomes poor;When the pH value is less than 8, alkaline and too weak, ink viscosity, drying speed, will cause dirty version, paste version, foaming defects.In the process of printing pigments, should choose domestic pigments bright color, low viscosity, stable system of advanced pigments to produce water-based ink.
Ester - soluble polyurethane compound ink
In order to improve the performance of water-based inks need to add a variety of additives, and water-based inks used additives more important than solvent inks.Commonly used water-based ink additives have the following:
Used to eliminate the water - based ink foam, the amount of 1% ~ 2%.
Mainly prevent ink in storage, transportation, coalescence, moldy, reduce ink viscosity and adjust the pH value of ink, the general use of ammonia water or ethanolamine and other additives.
Dispersants, preservatives, leveling agents, thickeners, slip enhancers and crosslinking agents.Through the scientific use of these additives to improve the water - based ink weaknesses, can improve the stability of water - based ink.
The solvent used
Solvent used for water-based ink should have: (1) dissolved resin, give ink;(2) adjust the viscosity, give printing adaptability;(3) adjust the drying speed.Alcohol-soluble composite ink also requires non-toxic characteristics, so its solvent is mainly pure water and a small amount of alcohol, such as water, ethanol, butanol, isopropanol, etc.These solvents can assist water to enhance the ability to dissolve the resin, improve the dispersion of pigments, and accelerate penetration and inhibit foaming.
Alcohol - soluble composite ink
The basic formula
Water-soluble acrylic resin 25% ~ 35%
Water 15% ~ 25%
Ethanol 5% ~ 15%
Triethylamine 5% ~ 10%
Pigment 10% ~ 30%
Additives 1% ~ 3%