How To Choose Pigment For Water-based Ink
Like other printing inks, water-based inks are a combination of pigments, linkers and ink additives. Selecting the right pigment is very important when producing aqueous inks, and most pigment manufacturers offer a wide range of pigments with different properties in order to select pigments for specific systems.The manufacturer of pigment yellow 74 says that when selecting pigments for aqueous inks, attention should be paid to the pigment’s alkali resistance, relative density and pigment mixing properties. Sometimes it is necessary to make the pigment into an aqueous dispersion of pigment particles, i.e. pigment slurry, which is then mixed and dispersed with linkers and additives to make aqueous inks. The following are the considerations for choosing pigments for water-based ink:
Pigment Resinification
It is very important to resinify the pigment when formulating water-based ink. Adding resin during or after the pigment coupling process can prevent the crystal growth, which can help the pigment dispersion and transparency. The resin also encapsulates the pigment particles, making the pigment easier to disperse during the pre-dispersion process. Resinned pigments produce more transparent inks than non-resinned pigments. Pigments developed in water-based ink systems can give excellent transparency, gloss and low rheology, but these pigments are not suitable in solvent inks.
Combination Of Pigments
When formulating an ink system, first of all, the stability of pigment placed for a long time should be considered, and secondly, different pigment fillers it’s physical and chemical properties, such as relative density, acidity and alkalinity, polarity and crystalline condition are not the same. Therefore, in the process of manufacturing ink, if many kinds of pigments and fillers are used, due to the difference of their physical and chemical properties, even if they are strongly stirred, they can only be temporarily dispersed in the ink, but if they are stored for a long time, there will be phenomena such as precipitation of pigments and floating colours, etc. Therefore, in the process of manufacturing water-based ink, it is necessary to make pigments and fillers in the ink for a long time. Therefore, the types of pigments and fillers used in the production of water-based ink should be as few as possible.
Base Resistance of Pigment
Pigment gives water-based ink the colour characteristics and meets the printing requirements of colour. The linker resin of water-based ink is mostly alkali-soluble, the viscosity and pH value of the ink need to be precisely controlled. pH value is generally controlled between 8.0 and 9.5, when the pH value is higher than 9.5, the alkalinity is too strong, and the viscosity of the ink will be lowered, which leads to slower drying speed and poorer water-resistant performance. When the pH value is lower than 8.0, the alkalinity is too weak, the viscosity of the ink will rise, the ink will be easy to dry, and it will cause defects such as dirty plate, paste plate and blistering, etc. Therefore, when selecting pigments, it is necessary to use pigment with high alkaline resistance. Therefore, the pigment with good alkaline resistance should be used when choosing the pigment.
Relative Density of Pigment
If the relative densities of the pigments used in water-based ink differ greatly from each other, the pigments with small relative densities are easy to float on the top, which is easy to produce phenomena such as floating colours, blossoming and precipitation. When the relative density is too large, it is easy to precipitate and destroy the stability of water-based ink.
To sum up, when choosing pigment for water-based ink, it is necessary to pay attention to the several aspects of pigment’s resinification, alkali resistance, relative density and pigment’s collocation. When choosing pigment, the water-based ink manufacturers should also consider the factors of pigment’s luster, chemical resistance, ease of dispersibility and the compatibility with other components, and lastly, the choice of dispersing equipment. If the dispersing equipment can not reach the suitable dispersing ink, then it can be considered as the choice of If the dispersing equipment can not reach the suitable dispersing ink, then we can consider choosing filter cake or dispersing pigment as the colour material.
In addition, economic factors should be considered when choosing pigment. For ink manufacturers, when the required ink suitability is satisfied, the price is always an important factor to be considered when choosing pigment. Therefore, knowing the specifications and technical parameters of the pigment products is beneficial for water-based ink manufacturers to choose the best pigment.