The Chemical Resistance Of The Pigment
In the manufacture of water-based ink, the choice of the right pigment is very important, most manufacturers will provide several different properties of the pigment, so you can choose a special system for the pigment. Hue is the primary consideration for pigment selection, followed by gloss, chemical resistance, ease of dispersibility and compatibility with other components, and finally the dispersion equipment selection, if the most efficient dispersion equipment can not achieve the appropriate dispersion of ink, then You can consider selecting a filter cake or dispersing the pigment as a pigment. In addition to the choice of pigment, Pigment but also consider the economic factors, for the ink recipe, when the required ink suitability, the price is always selected pigment to consider the factors. Most pigment manufacturers will announce the specifications and technical parameters of their products to help the ink dispenser choose the best pigment.
In the preparation of an ink system, we should first consider the use of the form of paint and long-term stability. Alternative pigments are dry pigments, filter cake and disperse pigments. One advantage of selecting dry pigments is that the dry pigment is a 100% dry product, so that the concentration of the pigment in the ink is not used; for the filter cake or the dispersion pigment, it is necessary to experiment to determine the concentration of the pigment in the ink. And dry pigments are also easier to handle than the other two forms of pigments. Pigment Dry paint in a certain period of time or even a few years its nature will not change, select dry paint another reason is its wide range of manufacturers.
① opaque pigments opaque pigments can be used in certain water-based inks where transparency is not required. Ink-based inks for printing paper, paperboard, polyethylene, polypropylene, corrugated paper and label paper can use opaque pigments. The opacity of the pigment provides a good hiding power to the pigment, Pigment so the opaque pigment is often used in the printing of corrugated and wrapping paper. The opaque pigment particles are large in size, easy to disperse, have good fastness and low rheology.
② transparent pigment printing high-quality printing products, such as metal foil, labels and paper, need a transparent and shiny good printing ink, often use the particles school pigments do pigment. In many packaging areas, transparent pigments can provide better gloss, Pigment high printing strength and dyeing strength. Due to the small size and transparency of the particles, the transparent pigment has a lower fading property than the opaque pigment.
In the preparation of water-based ink, the pigment is very important. The addition of resin during or after the pigment coupling can prevent the growth of the crystals, thereby contributing to the dispersion and transparency of the pigment. The resin can also wrap the pigment particles to make the pigment more easily dispersed during the pre-dispersion process. Resin-based pigments can produce more transparent inks than non-resinable pigments. Pigments developed in aqueous ink systems can provide excellent transparency, gloss and low rheology, but these pigments are not suitable in solvent inks.
The use of highly resinous pigments in aqueous ink systems tends to produce unstable rheology, mainly due to the incompatibility of the resin and ink grinding in the pigment manufacturing process and the acrylic resin in the formulation. Highly resinous pigments such as C.I. Pigment Yellow 83 should be carefully selected to avoid the above problems. In the water-based ink system can also be observed in the metal azo red calcium salt pigment instability. Such as C.I. Pigment Red 48: 2 or C.I. Pigment Red 57: 1, in which the proton proton is attached to the benzene molecule, and when the crystal water is removed from the molecule, discoloration can be observed. When these pigments absorb water after the color moves to the yellow phase, dry water when the water is moved to the blue phase. If the pigment is stable, the hue should return to the primary color. For some amine protons are attached to the naphthalene molecules on the pigment, such as C.I. Pigment Red 49: 2, the calcium salt, barium salt and strontium salts in aqueous solution are hue stable pigments.