Speed ​​printer ink analysis (on)

1. Ink type attribution
The digital integrated shuttle printer is mainly produced in Japan. After more than ten years of marketing in our country, it has been widely used in schools, government agencies, large and medium-sized enterprises, and street printed media. The most popular models in the current market are the ideal series, the Ricoh/Gestet series, the Depot series, and the Century series. Different models are equipped with the corresponding special inks and packaging containers, but all the inks are of the same composition. Water-in-oil emulsion ink. Because only water-in-oil inks can meet the basic requirements for fast printing and on-board placement, other names (such as water-based inks) are not exactly cut.

2Ink Technical Analysis
The use of printers is based on two points: rapid and low cost, and the inks that are matched with them should have the characteristics of “fast-drying, stable, low-cost, and environmental protection”. It has been pointed out above that the printer ink is a water-in-oil type emulsion ink. The technical formula design and manufacturing process of the ink is performed according to the water-in-oil system. The ink formulation should satisfy: A, the inherent rationality between formula ingredients; B, the machinability of the material (different base ink formulas use different processing equipment); C, the applicability of the printing press (the nature of different printing inks Not the same); D, paper applicability (ink requirements on the paper is printed clearly, black is good, not through the bottom, not dirty, can not erase the writing).

(1) Formula design
Speed ​​printer inks are penetrating/volatile drying inks. The ink consists of an oil phase and an aqueous phase. The oil phase is basically similar to traditional inks. The process of emulsifying the oil phase into ink by adding water is similar to the production of cosmetics. When the ink is printed, the oil phase penetrates into the crevices of the paper fiber, moisture, etc. Volatilize to complete the printing and drying process.

A, oil phase
The oil phase consists of binders, pigments, auxiliaries, emulsifiers, etc. In consideration of the flowability and the filter platenability of the ink of the printer, no filler is generally added. The binder is made of solvent oil to dissolve the resin. Solvent oil satisfies its own characteristics of no peculiar smell, strong paper permeability, good resin solubility and release properties, and low viscosity-temperature degeneration. Mineral oils, vegetable oils and synthetic oils can be selected. Mineral oil can choose engine oil (22 #, 32 #, 46 #, etc.), high boiling point kerosene (260 #, 270 #, 280 #, 290 #, etc.), lubricating oil, spindle oil and liquid paraffin, the best choice for environmental protection Resin-soluble naphthenic oils. The aromatic oil is poisonous and it is best not to use it. Vegetable oil can be selected from coconut oil, castor oil, soybean oil (soybean oil is soybean oil added to the ink as a solvent oil), rapeseed oil, you can also add a small amount of linseed oil and tung oil, but be sure to properly add antioxidants or anti-crust Agent. The ink made from vegetable oil is more ink-friendly than mineral oil, and the ability to prevent the ink from escaping is also strong, but it is necessary to prevent the vegetable oil from oxidizing the conjunctival crust while the ink does not move and jam the drum. Furthermore, the use of several oils in the oil phase is a good choice.

Resins used in paper inks are mainly solid rosin phenolic resins and liquid alkyd resins. The inks of the printers are also mainly of the above two types, and the use of them in combination is more effective. The two resins are the most able to provide ink and ink. The choice of the rest of the resins may include polymeric oils, rosin-based resins, polyester resins, petroleum resins, rubber derivatives, and the like. It is best to mix several resins. The key to the choice of resin is that it can disperse pigments well and dissolve well in solvent oils. The resin itself or the produced resin oil does not form a film in the air and does not precipitate out. The quality requirements of each batch of resin are close to each other.

Commercially available resins are difficult to meet the requirements of the ink, it is best to chemically modify the resin, improve the overall performance of the resin.

The speed of the printing machine ink is mainly black, the pigment is mainly carbon black, carbon black is recommended to use furnace carbon black, and carbon black is selected as the small oil absorption value. Furnace carbon black dust and dispersion are good. Want to do a little high-end ink, it is recommended to use imported carbon black. Foreign companies include Cabot in the United States, Degussa in Germany, Colombia in the United States, and Mitsubishi in Japan.

The general ink can use domestic No. 6 carbon black, the company has Shanghai Coking, Shanghai Wusong, Tianjin Dagang, Liaoning Fushun and Dandong, Henan Qichang, Fujian Nanping. The amount of domestic ink carbon black is 6-8%, the amount of export ink carbon black is 5-7%, the domestic ink requirements are black, and the amount of carbon black is a little more, but the increase of carbon black needs to modify the ink formulation as a whole.

Among all the coloring pigments, carbon black is the most difficult to disperse, and it is easily flocculated and coarse after dispersion. Carbon black dispersants are recommended. Dispersants are selected from alkyl amines, polyesters, polycarboxylic acids, phosphate esters, alcohol amine salts and alkyd resins. The type and amount of dispersant is best determined by a small test screen. Carbon black special hyperdispersants available on the market can be considered, but they are more expensive. The good use of dispersant can significantly reduce the number of grinding, increase the color strength, improve and stabilize the product quality, and save the overall cost.

To obtain a pure black color, a colorant is generally added to correct red and brown carbon black bands. The colorant may be phthalocyanine blue or holland.

The best method is to chemically modify carbon black and graft carbon black molecules to increase the compatibility in the oil phase.

The emulsifier is generally used in Span 80, with an amount of 3-5%. Span 83, composite emulsifier can be considered.

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.