Printing Offset Ink Auxiliaries Types and Usage

First, viscosity and fluidity modifier

There are many kinds of them, the role is to adjust the ink's fluidity and viscosity, mainly including the ink varnish and remover and so on. The traditional varnish is mainly composed of zero oil (ie, external oil) and six oils of six varieties. The viscosity is the largest in the zero oil, and then decreases to the sixth oil, but some are not commonly used. Of course, there are other varieties of varnish.

The main introduction is as follows:
1. No.6 oil

It is one of the most commonly used ink auxiliary agents. It is mainly used to increase the fluidity of the ink, and at the same time, it can also reduce the viscosity of the ink. The amount of resin ink formulated is generally less than 5%. After adding it will reduce the ink dryness and gloss.

2. No. 0 transfer ink (also known as external oil)
The one with the highest viscosity in the varnish, with almost no fluidity, is a transparent elastic fluid with a relatively high viscosity. Mainly used to increase the viscosity of the ink, reduce the degree of emulsification, adjust the viscosity of the ink before and after the color group, so that the viscosity of the printing ink is slightly larger, and the transferability of the ink is improved. The amount is generally less than 5% so as not to affect the dryness.

3. Resin varnish

Viscosity is greater than that of No. 6 oil and is used to adjust the flowability of the ink, but it does not affect the viscosity of the ink. The amount is generally about 3%. The addition of the varnish does not affect the gloss and adhesion of the ink, and has little effect on the drying properties.

4. Thinner

Viscosity is smaller than that of No. 6 oil, which can increase the fluidity of the ink and reduce the viscosity. It has the characteristics of small amount but obvious effect. The amount is generally less than 3%, after adding basically does not affect the gloss and dryness of the ink.

5. High boiling point kerosene (aviation kerosene)

Its boiling point is 250～290°C. It is an excellent ink adjuvant and has good miscibility with ink. It can be used directly in ink to reduce the viscosity of the ink and increase the fluidity to a certain extent. The effect is obvious. The amount is generally 1% to 2% to meet the requirements, of course, can also be increased or decreased as appropriate. After adding, it will not affect the gloss and adhesion of the ink, and has little effect on the drying property.

6 . Remover (also known as detackifier)

It is a paste-like body and it is also one of the traditional commonly used ink adjuvants. It has the effect of lowering the viscosity of the ink but does not substantially increase the flowability. It can be used with resin varnish, No. 6 oil, etc., and can also be used alone. The amount is generally less than 5%, too much can easily lead to dirty version and reduce the ink gloss, dryness and adhesion. Need to cover the film should more strictly control the amount of use, otherwise it will cause film lamination and poor adhesion and other ills.

7. Ink improver (also called ink additive)

Paste is a new type of ink adjuvant. With the ink has a very good miscibility, adding ink does not dilute the ink. Both can reduce the viscosity of the ink, but also increase the fluidity, the amount is usually between 3% to 8%, but also increase or decrease, as appropriate. Under normal circumstances will not affect the ink drying, but the excess will reduce the ink's gloss and adhesion.

8. Antidrying agent

Also known as antioxidants. When the ink formulation uses some pigments with strong drying properties, such as iron yellow, chrome yellow, etc., the filming occurs during rolling, and thus it is difficult to perform fine rolling; when the ink is stored, if the surface part is in contact with air, it will be Oxidized crusts, even dry, cause the ink to be unusable; during the printing process, the ink will also dry on the printing press. Therefore, the proper amount of anti-drying agent added to the ink can retard the dry oil. Oxidative polymerization process. Anti-drying agents are strong reducing agents, such as hydroquinone, catechol, etc. They can be preferentially oxidized, delaying the oxidation process of dry oils. They are commonly used as polymerization inhibitors during the polymerization of high molecular substances because they are easily reacted with free radicals to form stable compounds, thus preventing the radical chain growth reaction.

Second, driers

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

1. Desiccant

Also known as driers, are a very important class of additives in inks. It is a catalyst for the oxidative polymerization of dried vegetable oils. In high-gloss inks, due to the high content of the resin, it is necessary to rely on the desiccant in order to accelerate its thorough drying.

, radiation, water, auxiliaries, pigment desiccants are cobalt, manganese, lead and other metal organic acid soaps. In high-gloss inks, cobalt and manganese organic acid soaps are mainly used. They are all oxidative driers, have a very strong drying ability, can make the ink surface quickly and uniformly dry. The role of desiccants is to shorten the induction period, accelerate oxidation, and promote polymerization.

2. 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.

3. 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.

4. 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.

4. Adhesive back agent

Also known as anti-dirty agent. When printing, the ink on the printed matter can sometimes be smeared onto the back of another print; when the printed matter is piled together, it can also stick together. For high-gloss inks, the drying time is slow and it is more prone to smudging. In printing, dusting is mostly used to prevent scumming.

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.