Several Common Ink Aids in Offset Printing

In offset printing work, we often encounter various kinds of printing problems. Among them, many printing problems are solved by adding different auxiliary agents to the ink. In addition, when factors such as process conditions, substrate materials, and changes in the external environment change, we will often improve the printability of the ink by adding certain types of auxiliary agents to the ink. Therefore, it is very necessary to understand the role that different auxiliary agents can play in printing inks and to master their usage methods and rules. In the following article we will introduce some of the more common adjuvants.
Drying Regulator Because we often encounter the difference between the drying properties of the ink itself and the ones we hope to obtain in the production, we often use dryness modifiers. Dryness modifiers can generally be divided into two types, drying agents and antidrying agents.
1. Drying agent. Drying agents commonly known as dry oil, also known as desiccant directly, if you encounter in the production of printing speed, poor absorption of the surface of the substrate and other reasons caused by the slow drying of the ink layer or the back of the dirty phenomenon, often Add the appropriate amount of dry oil to the ink.
Main components of dry oil The main components of dry oil are cobalt, manganese, lead and other metal organic acid soaps.
The Drying Principle of Dry Oil The drying principle of dry oil has not been clearly defined. It is still widely debated. The following two are relatively convincing explanations: The first one is that the ink contains dry vegetable oil, and in the dry vegetable oil, there are often some phospholipids that are easily oxidized. Such substances will be dried during the ink drying process. The preferential combination with the oxygen in the air causes the dry oil in the ink to reduce the drying rate due to "oxygen deficiency." When the dry oil is added, the metal in the dry oil is reduced to a low price and the phospholipids are oxidized by oxygen. Before it has been oxidized and lost its "antioxidant" effect, it can effectively reduce the ink drying time. The second explanation is that it can promote the formation of free radicals. In the stage of hydroperoxide production, since the hydroperoxide is very unstable, it will rapidly decompose under the catalytic action of cobalt to generate free radicals, and the cobalt ions themselves will not Changes can continue to function, and the formation of active radicals will continue to occur polymerization.
Types of dry oil White dry oil: Its main composition is lead, manganese, cobalt soap, which is characterized by the ability to make the ink dry from the inside out. White dry oil can be used alone or in combination with red dry oil. The addition and release time of dry white oil should be added before the printing, otherwise it will be conjunctiva or gelation due to the long time of adding. In addition, due to the presence of harmful metals in dry white oil, it cannot be used in the printing of food packaging.
Red dry oil: The main active ingredient of red dry oil is cobalt, which has extremely strong drying performance. The drying process is that starting from the surface with too much dry weight will cause the ink to be conjunctiva on the printing press. In addition, the redness of the red oil itself will have a certain influence on the hue of the ink, so be cautious in use (see below for specific dosage).
New desiccant: Because it does not contain toxic heavy metals, the use effect is also better than the former two, so it is widely accepted and used.

The amount of dried oil Through some of the above analysis of the principles, we will find that the role of dry oil in the ink drying process is to promote, rather than change the nature of the ink drying. In addition, no matter which kind of explanation will explain a problem, it is that the amount of dry oil added in the ink is not as good as possible. When the dry oil is added to a certain extent, it will not play any benign role anymore. Instead, it will be dry. The emulsification of heavy metals in the oil results in over-emulsification of the ink, and the antioxidant effect of the water particles and water film accumulated in the ink will cause the ink to further dry out.

So how much desiccant in the ink can meet the requirements? See the table below

The amount of dry white oil (%) The amount of red dry oil (%)
Black 5 to 10 2 to 5
Product 5 2～5
Green yellow 3～4 1～3
Yellow 3~4 1~3

2. Anti-Drying Agents Anti-drying agents are also known as antioxidants, sometimes due to excessively high ambient temperature, or the drying nature of the ink itself is too strong, in order to prevent the ink from oxidizing on the printing press, affecting the ink transmission, and adding a suitable amount of anti-dryness to the ink. The agent can play a role in delaying the drying of the ink. Its main component is a strong reducing agent (hydroquinone, catechol, etc.) that can be preferentially oxidized before the ink receives oxygen. The amount of anti-drying agent should be strictly controlled below 1%, otherwise it would be harmful and unprofitable for printing. Since the use of anti-drying agents in printing is not very much, we do not introduce too much here.
Fluidity and Viscosity Adjuster Fluidity adjusters are auxiliaries used to adjust the ink's flowability, tackiness (VISC), and viscosity (VISCOSITY).
Commonly used such adjuvants are:
1. Remover. Release agent is a paste material, the main components of aluminum salts (such as aluminum stearate, aluminum octacarbonate), linseed oil, low viscosity alkyd resin and paraffin oil. The release agent is thick and loose and soft, with no adhesiveness. The main effect of the detackifier in the ink is to reduce the tackiness (TACK value) of the ink without changing its fluidity. In the process of lithography and letterpress printing, if the paper is pulled due to low surface strength of the paper, poor water resistance, and excessive adhesion of the ink, problems such as stencil and stack rubber may occur, and proper addition may be improved. Also note that the release agent only changes the viscosity of the ink without changing the flow of the ink. When the fluidity of the ink is more than 32mm and the viscosity is too large at the same time, the use of a paste-like release agent can ensure the body of the ink and maintain the integrity of the dots.
The use of remover: Remover should not exceed 5% in use. If it is used too much, it will form a layer of wax on the ink layer of the ink to hinder the normal transfer of ink and hinder the contact between ink and oxygen. Due to its inherent porosity, the cohesion of the ink can be reduced, and the emulsification of the ink can also be exacerbated. This is not good for the gloss of the ink or the drying speed. Therefore, the use of the detackifier in the ink must be strictly controlled.
2. No. 6 varnish is a mixture of dry vegetable oils and high boiling point petroleum solvents. The use of No. 6 varnish in ink can reduce the adhesiveness of the ink and improve the flow of the ink. When the ink roller dry transfer ink performance is not good, the appropriate amount of No. 6 oil can be significantly improved.
The use of oil No. 6: The use of No. 6 oil has no obvious ratio limit, and is mostly added according to the experience of the operators in use. However, the excessive addition and release of the No. 6 oil will slow down the fixation of the ink on the printed matter, causing back-scratching of the printed matter, and excessive penetration of the surface of the printed matter due to the thinness of the ink, and surface crystallization.
3. Diluent (high boiling point oil)
Its main component is high boiling point petroleum solvent. Belong to mineral type varnish, adding in the ink can reduce the viscosity of the ink and improve the fluidity without affecting the fast fixing ability of the resin ink.
Use of Mineral Type Diluent: Since the mineral oil type diluent and the resin in the ink are soluble and insoluble (releasability), they should be gradually added under stirring to avoid resin precipitation. Generally, the effect of removing the thinner from the thinner is good. Generally, adding 1% can reduce one sticky unit. The same applies to the amount used in use.
4.0# varnish (0 oil)
Is a kind of varnish, its composition and the ink itself is similar to the connection material, so the application of varnish only changes the physical properties of the ink (fluidity), and the role of 0 # varnish is to be Improve the cohesion of the ink.
When the following situations occur, it is necessary to add 0 # varnish 1 to the ink. It is necessary to increase the fixing force of the ink on the paper surface, so that the imprinting is strengthened and the firmness is enhanced;
2 control ink emulsification and overcome dingy;
3 to reduce the penetration of the connection material on the paper to prevent oil seepage, powdering, increase the gloss of printed products.
4 Used to overcome the heap phenomenon.

0 # use of varnish: As 0 # varnish viscosity is very large, so when mixed with ink often have some difficulties. The ink should be used to slap the thick-bodied ink thoroughly, and then the ink to be adjusted should be taken in a small amount and added to the ink. Then continue tapping and stirring.
Tone adjuster 1. Dilution agent (disposal agent)
The use of a diluting agent dilutes the color of the printing ink while maintaining its tackiness. The main components are aluminum stearate, dry vegetable oil, phenolic resin, beeswax, high-boiling point kerosene and other materials. It is a kind of paste-like transparent material. It is specially designed for glossy resin inks. It is used as a color adjuster and has excellent gloss and good printing adaptability.
The use of diluting agent: There is no limitation on the amount of diluting agent in the process of blending with the ink. The specific proportion should be determined according to the color tone of the ink to be obtained. In the process of blending the extremely light color ink, attention should be paid to the adjustment sequence and a small amount should be taken. The addition of the ink to the diluting agent will make the dispensing operation more convenient and accurate.
2. Transparent oil (dimensional oil)
The main components of Weili oil are aluminum hydroxide and polymeric oil. The good printing performance is generally mixed with the resin ink, in addition to reducing the color saturation of the ink, but also effectively reduce the vitrification problem, the amount should not exceed 1/3, try not to use the force of oil in the last color printing , so as not to reduce the ink layer gloss.
Try to avoid the use of dimensional oil in fast-drying bright ink, otherwise it will cause the ink layer to lose luster, reduce dryness, and even cause gelation, and other ills.

3. White ink is generally not recommended, because the white ink itself is relatively coarse pigment particles, poor printability, very easy to stack rubber, paste version, emulsification in the printing process, the use of white ink deployment of pale ink, in the printing In total, people have headaches. However, sometimes some of the more special circumstances, such as the need for a thicker, more opaque ink layer, also need to use. In order to change the printability, we often use white ink and bright paste together to maintain the unique white ink properties and improve the printability of the ink. At the same time, we also have a certain degree of improvement in the gloss and adhesion of the ink. benefit.
The specific usage is the same as the usage of diluent.
4. Bright paste The main components of bright paste are high-grade synthetic resin, refined dry vegetable oil, gelation agent and solvent, etc., which are made of high-temperature refining and are made of transparent ointment paste. It is mainly used for diluting the fast-setting light offset printing ink, but it can also be used for diluting various types of oil-type resin glue and lead printing ink, and is often used as an excellent auxiliary agent for improving ink gloss.
Compared to the above auxiliary agent, the bright paste has the following features:
1 can make the diluted ink has better printability.
2 After the bright ink diluted ink, can have a strong luster, moderate dryness and print parts clear features.
5. White oil White oil is a diluting agent made of magnesium carbonate, stearic acid, polymeric oil and other raw materials emulsified by heating, and is a milky white translucent ink paste. The printability is not good, but the biggest advantage of white oil is that it is cheap, so white oil is often used as a diluting agent for low-grade light-colored offset printing inks. The light-colored ink that is adjusted into it is sometimes better. The print is used to render the bottom.
Concluding remarks Because the ink itself is configured according to scientific formula before leaving the factory, each component has undergone a relatively rigorous inspection. In addition, there is a balance among the various components of the ink, and the addition of foreign components will inevitably break the original balance and affect the quality of the ink. In the process of using ink additives should not be blind, and must follow the "add as little as possible, can not add without adding" principle, easily do not believe that the various additives provide the advantages above.
Of course, the right amount of scientific use of various additives