How to prevent excessive emulsification of ink?

February 20, 2023
February 20, 2023 Longchang Chemical

How to prevent excessive emulsification of ink?

1, the impact of ink emulsification on printing

If the ink emulsification is just right, indicating that the water and ink in a relatively balanced state, creating good printing conditions for offset printing, graphic ink can achieve the transfer of ink, so as to obtain the network glossy, neat, clear images, rich layers, bright colors, saturated printing effect, and to ensure the accuracy of overprinting and promote the drying of printed materials, while also ensuring that the non-printing area of the blank part clean and tidy.

Therefore, whether the correct mastery and control of ink emulsification, is to ensure that the water and ink balance, stable printing quality of the key. If the ink and water mastery is not appropriate, resulting in excessive ink emulsification, will inevitably lead to ink and water imbalance, the printing quality has a negative impact. In practice, if the water and ink is not properly mastered, it is easy to over-emulsification of ink, which is extremely harmful to the quality of printing.


Ink over-emulsification, meaning that the ink dispersed into the tiny droplets too much, more than a certain proportion, the nature of the ink then changed, such as color lightening, color saturation decline, viscosity decline, adhesion weakening, etc., thus causing the process and print quality instability.

For example: the gray balance is broken, the color is not restored, the print color gray, the level is not clear; ink transfer deterioration, ink color suddenly big and small, the product before and after the ink color difference; easy to appear floating dirty, paste plate and other process failures, the drying performance of the print greatly slowed down, easy to cause the back sticky dirty, etc. Therefore, to control the quality of printing, to try to prevent the appearance of excessive ink emulsification situation.


2, the causes of excessive ink emulsification and prevention

The factors that cause excessive emulsification of ink are many, mainly paper, fountain solution, ink, watering down agent and desiccant, etc. Therefore, to avoid excessive emulsification of ink should be for the different factors affecting the right remedy, and to prevent it before it happens.


2.1. Paper factors

As paper, such as some offset paper, coated paper, white paper, the surface of the adhesive, paint or other filler contains more or less surface active substances, they have a certain water solubility, if the combination with the paper is not firm, in the printing process by the wetting solution and after the blanket squeeze and peel, these surface active substances off and through the printing plate passed to the ink rollers, water bucket, and ink fusion, so that The viscosity of the ink is greatly reduced, water absorption increases, water resistance is affected, causing excessive ink emulsification.

The greater the moisture on the plate, the more dissolved filler, the more serious emulsification; sizing is not good, loose paper, powder, the more serious the paper, the more likely to emulsify excessive.


Preventive measures: ① change to better quality paper, fundamentally eliminate the excessive emulsification of ink caused by paper; ② diligent washing rubber, printing plate, timely removal of fallen paper powder, paper hair; ③ add a small amount of additives in the ink, and reduce the page moisture and reduce the pressure of the water roller, to reduce the paper off powder and hair.


2.2. Fountain solution factors

Fountain solution dispersion is one of the conditions that cause ink emulsification, the water film on the surface of the printing plate, under the extrusion of mechanical force, the formation of tiny droplets dispersed into the ink, causing ink emulsification, so the amount of fountain solution is too large, the plate water film is too thick, along the ink rollers to spread the water increased, after the roller, the mutual extrusion of the ink rollers, the ink emulsification accelerated and excessive emulsification. The greater the amount of water, the thicker the water film, the smaller the PH value, the more serious excessive emulsification.


Preventive measures: ① control the amount of fountain solution, in order to ensure that the printing plate is not dirty, the print meets the level, density, color and other quality requirements, reduce the amount of ink, reduce the amount of water; ② control the ratio of fountain solution, PH value should not be too small, it is best to try to use alcohol fountain solution.


2.3.Ink factors

Ink viscosity is the main factor that produces emulsification, regardless of viscosity size, can produce different degrees of emulsification. Ink viscosity, its molecular cohesion, strong water resistance, emulsification value is small; conversely, if the ink viscosity is small, strong mobility, intermolecular cohesion, poor water resistance, it is easy to emulsify. In general, the ink viscosity is inversely proportional to emulsification, while the fluidity is directly proportional to emulsification.

The difference in the ability of the pigment itself to repel water will also cause changes in the emulsification value of the ink, for example, black ink, red ink, water resistance is better than green lotus, peacock blue ink, emulsification value is also smaller.


Preventive measures: ① choose the ink with good water resistance; ② for easy emulsification of the ink, increase the viscosity of the ink, ③ re-exchange with new ink.


2.4. Washout agent and desiccant factors

Commonly used diluting agents are mainly withdrawing agent, white oil, white ink, Vili oil, etc., which withdrawing agent is an amphoteric oxide, hygroscopicity, emulsification value is larger, the emulsification value of white oil is also larger, very easy to cause the emulsification of the ink, if you add these diluting agents in the ink, must make the ink emulsification accelerated; drying agent such as white dry oil, red dry oil, its emulsification value is larger, adding the right amount of drying agent can accelerate the drying of ink, but Such as excessive addition, but will reduce the drying speed of the ink, and at the same time will make the ink emulsification deterioration.


Preventive measures: to add watering down agent or drying agent according to the specific circumstances, can not blindly add, try to control within a certain amount, generally in about 2%-3%, can not exceed 5%.


2.5. Excessive emulsification caused by other factors

Other factors such as workshop temperature, humidity, speed and water roller, ink roller pressure and other factors, will also have a certain impact on the ink emulsification.

For example: the higher the workshop temperature, the higher the temperature of the roller, ink roller surface, the thinner the ink, and the greater the fluidity, the smaller the viscosity, water resistance is weakened, if the speed is high, the interaction force is large, these factors play a strong catalytic effect on the excessive emulsification of ink, the greater the workshop temperature, the easier the ink emulsification.


Preventive measures: ① workshop as far as possible to install air conditioning, the workshop temperature control between 20 ℃ -26 ℃, humidity control between 53%-65%; ② pay attention to adjust the water roller, ink roller pressure, so that it is within the appropriate range, to ensure that the transmission of water, ink smoothly; ③ in the shutdown idle, should shut down the water supply, ink supply, to avoid water and ink to accelerate the ink emulsification.


Affect the ink emulsification factors are many, and many times, the cause of excessive ink emulsification is often several factors work together, for example: small graphic area, ink consumption, ink contact with water for a long time is easy to produce emulsification, if the poor water resistance of the ink, too much water, more likely to over-emulsification of ink.


Therefore, the problem of ink emulsification, we should analyze and exclude one by one from many aspects, we must establish the idea of prevention before it happens, focusing on prevention, in addition to the quality of raw materials to keep a good check, usually also need to develop good working habits, standardize the process operation, such as: do a good job “three flat”, ” Three diligent” work, timely detection and problem solving, and pay attention to the accumulation of experience, as far as possible to grasp the right degree of ink emulsification, control the ink balance, print out clear dots, clear layers, bright colors of high-quality printed materials.


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