May 27, 2020

The use of common ink additives and precautions (2)

Second, driers

Used for adjusting the dryness of the ink. There are two main types:

1. White dry oil

It is a mixed desiccant that promotes simultaneous drying of the inner layer and the surface of the ink. It can be used alone or in combination with red oil. Strong drying performance, and can improve the gloss of the print to some extent. The amount is preferably less than 5%, and no more than 10%. Adding too much will cause problems such as quit, dirty, and dry rubber rollers. If this type of failure occurs, you can reduce the amount of white dry oil (3% or less) and add a small amount of red dry oil (about 0.5%). solve. It needs to be noticed that white dry oil contains heavy metal lead which is harmful to the human body. Therefore, it cannot be used in printed food packaging and other sanitary articles. In case of such prints, red dry oil or mixed desiccant can be used.

2. Red dry oil

With a small amount, the effect is obvious, can make the ink surface quickly dry the conjunctiva, and can improve the gloss of the print. Usually used in conjunction with white dry oil, and sometimes can also be used alone, the amount is generally about 1%, excessive easy to produce "dry roller" phenomenon. In the "dry overprint" (ie, wet-press dry printing), the first two colors cannot be used or used as little as possible to avoid crystallization of the ink layer. In addition, red dry oil, although dark red or purple, but because it is transparent and the amount is very small, it will not generally affect the color tone of the ink, even light yellow ink, white and other commonly used.

3. Mixed desiccant

In addition to the above two types of desiccants, another new type of advanced desiccant is a product recently developed by an ink manufacturer and belongs to a mixed desiccant. With the characteristics of prompting the ink to be fully and rapidly dried from the surface and inside, it can improve the glossiness of the print and the fastness of the ink to some extent. Because it does not contain heavy metals that are harmful to the human body, it can be used as an alternative to white dry oil for printing food packaging and other sanitary requirements. Generally used alone to meet the requirements, if there is no health requirements on the print can also be used with dry white oil. When used alone, the amount is generally controlled below 2%. In addition, the mixed desiccant itself is dark red or magenta, but since it is transparent and its amount is small, it generally does not affect the hue of the ink as does red dry oil.

Third, dilute agent (dilute ink)

The auxiliary agent for formulating light ink mainly includes white ink, lighter agent and the like.

1. White ink

It is a kind of lightening agent commonly used for light-colored ink preparation. The light-colored ink formulated with it has a good hiding power, and the ink is thick and white and has a strong powdery texture, and has the effect that other diluting agents cannot match. However, due to the fact that the white ink pigment has a large specific gravity and coarse particles, the printability is not very satisfactory. In some cases, problems such as ink transmission and poor transfer are easily caused, and the adhesion of the ink is also relatively low. Prints that require lamination sometimes suffer from poor adhesion. To avoid such failures, brighter paste or lighter may be used instead. For prints that must use white ink as a diluting agent, it is recommended to choose a white ink with good quality, or a combination of both white ink and bright-light paste. This will not only maintain the unique quality of white ink, but also improve the printability of ink and improve the The gloss and adhesion of the print.

2. Diminishing agent (also known as diluting agent)

It is a transparent diluting agent and has good miscibility with the ink. Adding ink only plays the role of diluting the color without affecting the original ink color tone. The lower grade dipgents have somewhat poorer dryness and gloss, and desiccants must be added as appropriate. The higher-grade lighter has the characteristics of high gloss, good printability, and moderate dryness, and usually does not require the use of a desiccant. Generally used alone, can also be used with white ink.

3. Bright light

Is an excellent ink dilute agent, in addition to the same advantages with the lighter, but also has a higher transparency and gloss, better printability and drying characteristics. In addition to use as a dilute agent, it can sometimes be used as a gloss coating surface, has a good gloss, but the friction resistance is not high.

Fourth, offset printing oil

It is a printing type glossy oil that can be directly applied on the surface of a print using a printing press. It has excellent transparency, gloss and rub resistance, water resistance and solvent resistance. It is mainly used for polishing the surface of the prints, and it can also be used as a diluting agent. Dilute inks have higher gloss and rub resistance and have good printability. However, light oil will reduce the life of the ink roller and blanket, so it should be avoided as a diluting agent, and the use of bright light as well. Offset bright oil is divided into light type and matte type, and should be distinguished when used.

The above is only a part commonly used in the ink adjuvant, in addition to anti-drying agent, anti-sticking agent, anti-friction agent, etc., which will not be described here.

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