PH meter and conductivity meter accurate measurement reduce printing cost

2020-08-19 04:12:30

In the printing industry, what role can industrial PH meters and industrial conductivity meters play? What benefits can it bring to the printing industry? Why should the printing industry accurately control the PH value and conductivity? The following is a brief introduction to the above issues .

1. Measurement and monitoring of paper pH value

1. The PH value affects the printing attributes such as water and ink balance

In offset printing, the pH of paper and fountain solution will directly affect the water-ink balance, ink drying performance and ink layer quality of the printing process. Therefore, when controlling and adjusting the balance of water and ink, it is necessary to understand the acidity and alkalinity of paper and fountain solution, and industrial PH meters can help measure and monitor the change of PH value. In order to understand its impact on the printing process.

2. PH value is the most important to improve printing quality

Due to the increasingly higher requirements for printing quality in the market, and the advancement of printing technology, the impact of paper characteristics and printability on printing quality has begun to attract attention, and paper pH is a factor that should be controlled.

3. The effect of too low PH value

When the pH of the paper is too low, the acidity of the fountain solution will be significantly enhanced, thereby inhibiting the oxidative polymerization reaction and drying speed of the ink, resulting in poor drying of the printed matter.

4. The best PH range for printing

If the pH value of the printing paper is neutral, the printing quality can be greatly improved. However, due to the influence of raw materials and processing technology in paper production, absolutely neutral paper with a pH value of 7 is not available. The printed paper surface or coating layer often has a certain acidity or alkalinity. When the pH value is 7, the paper The surface is alkaline. At present, China's papermaking mainly adopts alkaline pulping and uses NaOH as a cooking agent, so most papers are slightly alkaline. If the alkalinity is too large, the acidity of the fountain solution will obviously change, and the acidity of the hydrophilic glue layer of the non-graphic part of the printing plate will be weakened. If it cannot be adjusted in time, it will inevitably cause the hydrophilicity of the non-graphic part to decrease, and the ink and ink will be unbalanced. , The coloring power of the ink is reduced, resulting in the dullness of the printed graphics and text, and even causing the plate, paste and ink roller deinking and other phenomena. At the same time, the weak alkaline fibers that fall off the paper coating will be transferred to the blanket, and then transferred to the printing plate through the blanket, resulting in dirty printing plate and reduced durability. It is very necessary to use industrial PH meter to accurately control the printing quality.

2. Why measure and monitor the pH value of fountain solution

1. The necessity of controlling pH

Traditional offset printing materials rely on the principle of oil-water repulsion to achieve ink image transfer, fountain solution is indispensable, and its acidity and alkalinity have a significant impact on the printing plate and water-ink balance. It is necessary to effectively use industrial PH meters for measurement and monitoring.

2. Too strong acidity

The aluminum oxide film layer formed during the offset printing plate base treatment is amphoteric oxide. If the fountain solution is too acidic, it will increase the corrosion of the printing plate sand, destroy the blank part of the printing plate, and cause the printing plate to become dirty;

3. Too strong alkaline

Will not play a role in protecting blank parts, and will corrode ink and paper.

4. Benefits of control to weak acidity

The offset fountain solution is generally weakly acidic, and the ideal pH value is between 5 and 6. The industrial pH meter can meet the requirements of such precise control. This acidity and alkalinity can ensure clear printing dots, stable hydrophilicity of non-graphic parts of the printing plate, help to prolong the life of the printing plate, and can also inhibit the fountain solution from being invaded by bacteria and other impurities, and better maintain the balance of water and ink.

Third, the industrial PH meter to monitor and control the fountain solution

1. Main components of fountain solution

The components of the fountain solution are mainly buffers, preservatives, printing plate protection agents, desiccant algae inhibitors, etc., of which the buffering agent has the greatest influence on the pH value of the fountain solution.

2. The role of buffer

a) The function of the buffer is to stabilize the acidity of the fountain solution because the tap water is usually neutral. In order to achieve the pH value (5 to 6) required for normal printing, it is necessary to add acid to the fountain solution to make the fountain solution pH The value remains weakly acidic, and the carbonate in the water will react with the added acid to increase the pH. At this time, a buffering agent must be added to maintain the pH of the fountain solution at a stable level.

b) At the same time, the buffering agent has a significant effect on alleviating the influence of cleaning agents and other factors on the fountain solution. However, as the amount of buffer added changes, the pH of the fountain solution will fluctuate greatly. Inappropriate amount of addition will also affect the service life of the printing machinery and will also hinder the drying of ink, especially inks containing metal pigments.

3. The influence of water on PH value

Water also has a great influence on the pH of fountain solution. The quality of tap water is soft and hard. Water with a high content of metal cations is hard water, and water with a high content of anions is soft water. The high hardness of water will increase the pH of the fountain solution. When preparing fountain solution, the softness and hardness of water should be adjusted according to actual needs, preferably 10 Â° dH. It is also important to note that changes in water temperature will affect the concentration of ions in the water. Therefore, it is necessary to control the hardness and temperature of the water to achieve the best effect of the fountain solution.

4. The necessity of using industrial conductivity meter

1. Control the conductivity to ensure a stable PH value

In order to ensure that the pH of the fountain solution is relatively stable, an advanced method is to monitor the conductivity of the fountain solution while controlling the amount of buffer added and the hardness of the water.

2. Conductivity meter measures and monitors fountain solution

Because with the increase of the concentration of fountain solution, the hardness of water and the increase of water temperature, the conductivity of fountain solution will increase and the pH value will decrease; on the contrary, if alcohol is added to fountain solution, the conductivity of fountain solution The rate decreases and the pH increases. Tested by industrial conductivity meter, the conductivity of fountain solution should generally be controlled at (1400 Â± 200) Î¼s / cm, but due to the influence of dust, ink and other mixed materials, the conductivity is also within 800Î¼s / cm ï½ž 2000Î¼s / cm Allowed, but when the fountain solution appears to be contaminated, it must be reconstituted.

In summary, before printing production, we can take more precise methods, such as measuring the surface pH of the paper with a surface acidity meter, measuring the pH value and conductivity of the fountain solution with a liquid pH meter and a conductivity meter, and comparing it with Control within a relatively reasonable range, effectively avoid the occurrence of pH-related problems in the printing process, improve the quality of printed matter, and reduce printing consumables. This is a very important thing for printing houses.

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