B, water phase

The water phase consists of pure water, water-based resin, anti-evaporation agent, anti-freeze agent, anti-corrosion and anti-mold agent, and electrolyte. Simply, only water can also be found in the aqueous phase. Water can be regarded as a volatile component and can be regarded as a filling material in the ink, which increases the structural viscosity of the ink and prevents the ink from flowing out of the printer. The more water is added, the thicker the ink is (it is wrong to think that the ink is leaner than water). The amount of water is 50-70%, the amount of water is less, the ink is not faster, the amount of water is not much black, the printed sheets are not enough, and the water is not easy to be unstable. The water is preferably purified and the water must not contain trivalent iron ions. Trivalent iron ions have a strong catalytic ability and can easily damage the ink structure.

The role of the aqueous resin is to balance the viscosity difference between the aqueous phase and the oil phase, making the ink stable. Waterborne resins include gum arabic, cellulose (eg, cmc), acrylic resins, and the like. The dosage is 1-3%.

The water in the ink is easy to evaporate in the summer and freezes easily in winter. Anti-evaporation agents and anti-freezing agents can reduce this tendency. You can use ethylene glycol or glycerin. However, ethylene glycol is slightly toxic. Special attention should be paid to the processing of European and American inks. The recommended amount of anti-evaporation and anti-freeze agent is 3-6%.
Magnesium sulfate is preferably used as the electrolyte, and its double layer stability and solubility are good. Use 1%.

Preservatives and mold inhibitors prevent the growth of bacterial molds in the aqueous phase. At an appropriate temperature, the mold in the ink breeds very rapidly under aerobic and anoxic conditions, resulting in odor and deterioration of the ink. Use less than 1%.

(2) Process production

The process of producing the ink of the printing machine is closer to the cosmetic process, and the experience of the traditional printing ink has little advantage in the ink of the printing machine. When the ink is made, the oil phase containing the emulsifier is prepared first, and then the aqueous phase is slowly added thereto, and the mixture is stirred under vacuum until the viscosity is reached. Do not mix air when filling ink.

A, oil phase production

The selected solvent oil is used to dissolve the resin to make the linking material (this process can chemically modify the resin), add carbon black (or modified carbon black), additives, emulsifiers, etc., mix and grind, then stir The adjustment of oil compensation to an appropriate viscosity requires that the oil phase is delicate, uniform, and stable. The fineness of the oil phase is required to be less than 10m at least, preferably less than 5m (but the finer the surface, the finer the surface energy, and the more unstable the ink). We must note that the fineness of the oil phase and the fineness of the emulsion ink are two different things. The fineness of the emulsion ink is the fineness of the latex particles, and the fineness of the oil phase is mainly the fineness of the pigment carbon black. The fineness of the oil phase does not meet the requirements and the ink is particularly prone to water discharge. One of the main reasons for the short shelf life of domestic inks and the widespread availability of water is the inhomogeneity of the oil phase. In the production of ink can be left a small amount of oil phase placed 2 to 6 months, observe whether there is settlement, thickening, conjunctiva, agglomeration, flocculation and other undesirable phenomena.

The equipment for oil phase production is mainly a stirring and dispersing machine. Dispersing equipment is commonly used three-roller, ball mill, sand mill and so on. We hope to use imported equipment to manufacture high-grade ink. Domestic equipment is generally difficult to finely ground, and product fineness is difficult to meet.

B, emulsification

Emulsification is a key to the production of ink for quick printing machines. Require uniform emulsification, no bubbles, the fineness of the latex particles is less than 15u, it is best to emulsify the ink in a vacuum state (In the conventional state, the ink in the ink must be removed, the ink in the ink is thicker, and the static Removing air bubbles is difficult.) The uniformity of the emulsion ink can be burned by picking a little ink, and the sound of burning can be used to judge whether the emulsification is uniform or not. The relatively large blast sound is emulsified unevenly.

C. Inspection

The inspection indicators for inks include viscosity, fineness, blackness, fluidity, environmental protection, quick-drying, stability, fluidity, number of prints, and print fastness. Among them, viscosity is the most important indicator. The viscosity can be measured with a rotational viscometer (eg NDJ-79) (different instruments can be used, the values ​​measured by different instruments are different). The viscosity is in the range of 15-30 Pa.S/25°C. Recently, the viscosities of the ideal, Ricoh/Gestner, Depot ink market are basically 20 Pa.S/25°C, and the fluidity is good. The ink requires outer thick inner pine, the ink surface looks thick, the ink does not flow in the printing cylinder, does not drip, does not overflow the ink, does not throw the ink. The interior of the ink is loose, and the ink is easily suctioned from the packaging container. The ink is evenly coated on the roller, and is easy to pass through the wax paper plate, and the printed writing is clear.

Environmental protection is judged by the smell of ink smelling on the nose, and the ink is required to have no odor, no odor, and no irritating odor.

The stability is judged by the cold and heat experiments and the drop of ink on the paper. The ink is alternately placed in a hot and cold environment at -20 to 60°C, and then the viscosity of the ink is measured at room temperature. Observe whether the water is out of thinning or not. Soften, whether slag. Pick a little ink on copy paper or stencil paper. The shape is pagoda shape. After a certain period of time, observe the penetration of the oil ring (the oil ring is allowed to have brown color), the oil ring size is moderate, the ink is cracked, slag, surface Solidification and hardening of the crust, darkening of the color, and other unpleasant phenomena. The good ink basically sees only one oil ring, and the rest remains as it was.

Quick-drying, number of prints, and print fastness are judged by trial printing one or several inks on a printer, usually according to the standard test version carried by the printer itself. Printed parts require clear and unclear handwriting. The back is not dirty, and the writing cannot be erased. The number of printed sheets is close to the original ink.