What is the effect of water quality on offset printing?

1. The hardness of water

When the hardness of calcium exceeds 200 PPM, it causes it to form saponified calcium when it comes into contact with the resin in the ink, and when it comes into contact with the acidic solution, it produces salts like calcium citrate and calcium phosphate.

Saponified calcium has lipophilic properties that can cause the ink to deposit in undesired areas, such as the water roller and the surface of the water velvet. The calcium salt has good hydrophilicity, which can hinder ink transfer and cause the ink roller to deink.

In addition, if the calcium ion content in the water exceeds the standard, it will directly affect the life of the rubber roller, which will cause the surface of the roller to crystallize.

Conclusion One: Excessive water will exacerbate the emulsification process of the ink, which will lead to the deposition of the ink on the waterway, which will exacerbate the aging of the rubber roller (surface crystallization).

2. Fluctuations in conductivity when entering the water

The dynamic surface tension of the fountain solution depends on the concentration of the fountain solution therein. The higher the concentration, the lower the surface tension.

Some commercial automated conveyors can control the concentration of fountain solution to achieve a predetermined conductivity. When the conductivity of the incoming water is too large, it will cause the concentration of the fountain solution to change. The result is a misalignment of the oil and water, causing an offset failure.

If the proportion of the fountain solution is quantified exactly as other units, the problem may not be significant, but when the conductivity of the supplied water changes greatly, the interaction between the oil and the water can still be unbalanced.

Conclusion 2: When the conductivity of water fluctuates, it will affect the automatic control and detection of dampening fluid in the printing process.

3. For large companies with multiple plants

Some companies have branch factories in several cities and need to carry out standardized management in order to achieve a more uniform quality. This also puts higher requirements on the quality of water used. For example, how hard are the waters in several cities, and what are the impurity rates in several cities? This is a question that must be considered.

Conclusion 3: When the water quality in different regions is different, it will have a certain impact on the quality standardization of printed matter.

Through the above analysis, we have found that the quality of water itself has an impact on the printing process within a certain range. Therefore, the treatment of water is not an irrelevant matter. A competent company is necessary for the treatment of printing water. Water treatment in bad areas is a must.

Water treatment method:

The treatment of water can be said to be performed in a variety of ways, such as: distillation, demineralized water treatment, activated carbon filtration, microfiltration, ultrafiltration, reverse osmosis filtration, and the like.

1. Softened water treatment:

The sodium chloride-infiltrated resin is used to filter the water. When the sodium ions that have been combined with the resin meet the calcium, magnesium, and manganese ions in the water, they will be replaced by these ions, that is, the nano-particles will enter the water and the calcium Magnesium ions are adsorbed on the resin.

This treatment can effectively reduce the hardness of water (ie, reduce the content of calcium and magnesium ions in water), but it is worth noting that the conductivity of water itself does not change because the concentration of ions contained in the water does not change.

2. Ion removal

This method uses a cation resin exchanger and an anion resin exchanger to exchange the anions and cations in water, respectively. When the pressurized water passes through the exchange system, ions in the water are adsorbed by the resin, hydrogen ions or hydroxide ions in the resin are displaced into the water, and the charged resin is also consumed. When the resin fails, the resin can be reduced with strong acids and bases.

There are two main types of equipment for water treatment in this way:

1 Twin bed type resin exchange equipment. This device generally has two resin containers (Yin and Yang).

2 mixed type. The use of anionic and cationic resins is mixed at a certain ratio and used at the same time. If the mixing ratio is appropriate, the treated water quality is very good.

3. Reverse Osmosis:

Under normal conditions, the diffusion of water is diffused from a place where the concentration is low and where the concentration is high. The reverse osmosis method uses a certain material and means to reverse this process, and makes the concentration of water from the high concentration direction low under pressure. The proliferation of places. Reverse osmosis is a relatively thorough impurity removal technique that can remove 90 to 95% of the impurities in our drinking water under normal circumstances. More commonly used filter materials are: cellulose acetate membrane, polyamide membrane and composite membrane.

Note: The measurement of the conductivity of water is a method for characterizing the electrolyte content in water. The unit is S, the reciprocal of the water resistance. There are also smaller units using μS. The conductivity of the dampening fluid required to be used in the printing process is generally 500 to 1500 μS.