Discussion on some technical problems in the most

2022-08-12
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Discussion on several technical problems in water-based packaging printing ink (Part 2)

usage method

evenly spray or directly add pigments or fillers (without external heating) in high-speed mixing with tm-200 phthalate coupling agent diluted by solvent ≥ 1:1 or without dilution, stir for about 10min (the specific time depends on the speed and dispersion effect), then discharge the material for standby or add other additives and binders, and continue to operate in the third turbine Grind and disperse with ball mill or sand mill until it is qualified. If you use the above pretreatment and then grind and disperse, the effect is better. When we are packaging and printing, we can directly add this product to the ink bucket, and the effect is slightly lower. Because the dilution solvent of this product has wide selectivity - such as liquid paraffin (white oil), solvent oil, engine oil, isopropanol, ethanol, water, etc. Just pay attention to heat dissipation. When the viscosity increases in winter, the viscosity will drop rapidly when the water bath is heated (material temperature) 50 ℃

III. Influence on ink quality and elimination measures

1. Relationship between printing conditions and drying speed and gloss

water soluble flexible relief and intaglio printing inks and silk screen printing inks for printing packaging paper bags, books, periodicals and cartons, with low cost and poor gloss. The gravure carton water tank produced with high polymer acrylic resin has been used for more than a decade, but it is still a long way from meeting the requirements of users for gloss and brightness. Because of the paper density of carton packaging materials and the large water molecules of ink, only adding coupling agents to improve its branching degree is the focus of research

in addition to the above, the temperature and humidity of the printing workshop are also related to the dryness and gloss of the printed parts, which are mainly due to the high quality and low price of materials such as thermal insulation and sound insulation. Temperature is the main condition to promote the formation of oxidative polymerization and volatile solid ink film, so in summer and winter, the dry gloss of ink in the southern coastal and northern plateau areas is about twice as high

the temperature of the printing workshop can block the oxidation polymerization and the formation of volatile solid ink film on the drying of printing products. When the relative humidity reaches 95% and 65%, the drying time almost differs by more than two parts. At the same time, the dry humidity of paper, plastic and fabric will also directly affect the drying time of printing products

acidity will delay the oxidative polymerization and volatilization of ink, and the formation of solid ink film, while excessive alkalinity will lead to internal dampness and external dryness (skin scorched bones) and affect the adhesion of products. For example, the drying time of paper with pH value of 4.5 is 3-5 times longer than that of paper with pH value of 7. For the same reason, the pH value of water-based ink system is often reduced from 8 to 3.5, and the drying speed of printed products will also be extended by 3-4 times

because oxygen or blowing is a factor to promote oxidative polymerization and the formation of volatile solid ink film, the ventilation degree of the printing workshop and the stacking method of prints are also related to the drying speed of printed products. If the printing drying speed is too slow, it will make it difficult to overprint or cut in the next process, resulting in sticky back, light color and other phenomena. On the contrary, it will also make the second printing ink difficult to adhere

ink liquids with different specific gravity can coexist peacefully together after adding tm-200 coupling agent to bridge the binder. This unique architecture environment is very beneficial to today's new material processing, new product manufacturing, and fast high-performance packaging and printing

ph value is the key to the success or failure of ink manufacturing and printing adaptability technology - if it is not adjusted well, high-quality prints cannot be obtained. First of all, from the analysis of the components of ink, due to the combination of alkali soluble binder and lotion polymer, and even excessive dispersion, resulting in a large number of foam, can also promote the stability of ink, and expand the range of ink functions and printing and decoration characteristics. The stability of colorant and color carrier system depends on the pH buffer and the coating effect of coupling agent, which can resist the interference of foreign acids and bases, and maintain the stability of water-based ink pH within a certain range. Whether alkali (amine) and ammonia are added to the resin to neutralize the acid and dissolve it, or the latex manufacturing technology is very different (the resin is an insoluble continuous liquid) polymerization in water, even the water-insoluble matter of starch still accounts for as much as 26%. We know that it is dispersed by fine particles, but it is not completely dissolved. These millions of small particles wander in the water without conflict, because each particle is charged, and the ink formed on the common surface inhibits the merger between them, which is the result of the help of surfactants, protective adhesives and additives

when the ink is in the manufacturing or printing cycle, the volatile alkali is evaporated, which often causes the pH value to drop, so that the color carrying system begins to be unstable, loses the ability to exist stably in the ink system, and begins to solidify, and the viscosity increases significantly. The operating staff often mistakenly believes that it is caused by water shortage, and wants to use the method of water replenishment to adjust and remedy. Who knows, this dilution and low pH state will further aggravate the instability of the ink system, It often loses its transferability or discoloration, or even loses its stable state and precipitates. Generally, the pH value is controlled at 8 3

second, when the pH value of the ink in the ink bucket is too low, it can cause the drying of the metallic ink roller and the plate. During the transfer process, the ink will volatilize some alkali (amine) and ammonia, and the ink will recoil from the inking hole and the plate to figure 2 There is a problem with the software of the experimental machine; On the text plate, the printed matter is stained or the metal roller is blocked, that is, the ink volume is insufficient. Usually, after printing with rotary diaphragm vacuum pump ink, it is difficult to clean the printer with water

there is also a situation that the pH value of the ink bucket is too high, which is often caused by the adjustment of the operating staff. These remaining alkalis cannot be eliminated in the printing process. Even if the amount of alkalis is small, no matter how long the time is, the water resistance of the ink film is difficult to reach a high value. This is because the alkali is physically sealed after the ink film is formed, so the ink film will never achieve sufficient water resistance, adhesion and gloss

pH value of ink in addition to the above factors, the pH value of printing carriers such as paper surface, plastic surface, fabric surface (such as rosin ester, clay, etc. used in paper sizing agent in production, and each has its own characteristics) also has an impact on ink or dry, shiny ink. When the ink is printed on the surface of the paper, it will be affected by the pH value of the paper. When the paper is highly acidic, the coupling agent used as a drying agent in the ink does not work, and the alkali in the ink is neutralized, so that the dryness is advanced. While the tensile elongation at break of the paper keta spirekt (8) 10 is about 50%, the alkali is high, and the ink dries slowly, sometimes limiting the ink to achieve complete water resistance

2. Fault causes and troubleshooting of ink

inaccurate hue: the ink viscosity is too low or the pigment content in the system is small or the color purity is deviated, the ink separates and precipitates during printing, the ink is not stirred evenly, and cannot be transferred. Add the original ink, adjust the viscosity, mix the ink evenly before printing, and check whether the printing plate and ink roller are aging

unstable viscosity: the ink has thixotropy and foaming, and the solvent is volatile. The ink should be stirred evenly before reuse. Add an appropriate amount of Tao foaming agent (0. It is often used in scientific research institutions, testing institutions, new product development, etc. 2%), and add an appropriate amount of solvent to achieve the balance of volatilization speed

poor dryness (in addition to the above): when the imprint is not dry or even sticky within the expected time; The ink viscosity is high, the contour edge is not dry, the ink drying is poor, the absorption of base paper or plastic, fabric is too poor, dilute the ink, adjust the printing pressure, pay attention to the pad, use fast drying ink, or adjust the dryness, and replace the substrate. (to be continued)

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