(This article is an original article from Bisheng. It is forbidden to reprint, and reprinting must be corrected)
In offset printing work, we often encounter a variety of different printing problems, many of which are solved by adding different auxiliary agents to the ink. In addition, when the process conditions, substrate materials, external environmental changes and other factors change, we will often add certain types of auxiliary agents to the ink to improve the printability of the ink. Therefore, it is necessary to understand the role of different auxiliary agents in printing inks, and to master the methods and rules of their use. In the following article we will introduce some of the more common adjuvants.
Dryness adjuster
Since we often encounter the drying performance of the ink itself different from what we want, we often use the drying modifier. Drying adjusters can be generally divided into two types, desiccant and anti-drying agent.
1. Drying agent. Drying agents are commonly known as drying oils, and some are also directly called desiccants. In the production process, if the ink layer drying speed is slow or the back side is smeared due to other reasons such as fast printing speed, poor surface absorption of the substrate, etc. Add an appropriate amount of dry oil to the ink.
Main ingredients of dry oil The main ingredients of dry oil are organic acid soaps of cobalt, manganese, lead and other metals.
The principle of drying oil drying The principle of drying oil drying has not been clearly characterized and is still widely debated. The following two are relatively convincing explanations: The first one is that the ink contains dry vegetable oil. In the dry vegetable oil, there are often some phospholipids that are easily oxidized. Such substances will be dried during the drying process of the ink. It preferentially combines with oxygen in the air, which causes the drying oil in the ink to reduce the drying speed due to "lack of oxygen". When the drying oil is added, the metal in the drying oil is reduced to a low price, and the phospholipids are oxidized by oxygen It has been oxidized before and lost the "antioxidant" effect, so it can effectively reduce the drying time of the ink. The second explanation is that it can promote the formation of free radicals. In the stage of hydroperoxide generation, due to the unstable hydroperoxide, it will decompose quickly under the catalysis of cobalt to generate free radicals, but the cobalt ion itself will not The change can continue to function, and the formation of active free radicals will continue the polymerization reaction.
Types of dry oil: White dry oil: its main composition is soaps of lead, manganese, and cobalt, and its characteristic is that it can make the ink dry from the inside to the outside. White dry oil can be used alone or mixed with red dry oil. The addition time of the white dry oil should be controlled before the printing, otherwise it will cause conjunctiva or gelation due to the long time of addition. In addition, due to the presence of harmful metals in the dry oil, it cannot be used in the printing of food packaging.
Red dry oil: The main effective component of red dry oil is cobalt, which has extremely strong drying performance. The drying process starts from the surface and excessive amount of drying will also cause the ink to form a film on the printing machine. In addition, because the red color of the red dry oil itself will have a certain influence on the hue of the ink, it should be cautious in use (see below for specific dosage).
New desiccant: Because it does not contain toxic heavy metals, the use effect is also more ideal than the first two, so it is being widely accepted and used.
The amount of dry oil through some analysis of the above principles, we will find that the role of dry oil in the ink drying process is to promote, rather than change the nature of ink drying. In addition, no matter what kind of explanation will explain a problem, that is, the amount of dry oil in the ink is not as good as possible. The emulsification of heavy metals in the oil leads to excessive emulsification of the ink, and the anti-oxidation effect of the water particles and water film accumulated in the ink will cause the ink to dry further.
So how much desiccant can be added to the ink to meet the requirements? See table below
2. Anti-drying agent
Anti-drying agent is also called antioxidant. Sometimes due to the high ambient temperature or the drying property of the ink itself is too strong. It can delay the drying of ink. Its main component is a strong reducing agent (hydroquinone, catechol, etc.), which can be preferentially oxidized before the ink receives oxygen. The amount of anti-drying agent should be strictly controlled below 1%, otherwise it will be harmful and unfavorable to printing. Since the use of anti-drying agents in printing is not much, so I will not make too many introductions here.
Fluidity and viscosity modifier
The fluidity adjuster is an auxiliary agent used to adjust the fluidity, adhesion (TACK) and viscosity (VISCOSITY) of the ink.
Commonly used such adjuvants are:
1. Remove adhesive. The debonding agent is a paste-like substance whose main components are aluminum salts (such as aluminum stearate and aluminum octacarbonate), linseed oil, low viscosity alkyd resin and paraffin oil. The adhesive remover is thick, loose and soft, and has no adhesion. The main function of the debonding agent in the ink is to reduce the adhesion (TACK value) of the ink without changing its fluidity. In the process of lithography and letterpress printing, if the paper is roughened due to the low surface strength of the paper, poor water resistance, and excessive ink adhesion, and other problems such as paste printing and rubber stacking, the appropriate addition can be improved. In addition, it should be noted that the debonding agent will only change the viscosity of the ink but not the fluidity of the ink. When the fluidity of the ink is above 32mm and the viscosity is too large, the use of paste-like debonding agent can ensure the body of the ink and keep the isolation of the dots intact.
Use of debonding agent: Try not to exceed 5% during use. If it is used too much, it will form a wax layer on the surface of the ink layer of ink to hinder the normal transmission of ink and hinder the contact between ink and oxygen. Due to its loose nature, it will reduce the cohesion of the ink, and it is also easy to increase the emulsification of the ink. This is not good for the gloss of the ink or the drying speed. Therefore, the use of the debonding agent in the ink should be strictly controlled.
2. No. 6 ink
The ingredient is a mixture of dry vegetable oil and high boiling petroleum solvent. The use of No. 6 ink in the ink can simultaneously reduce the adhesion of the ink and increase the fluidity of the ink. When the ink transfer performance of the machine ink roller is not good, the proper addition of No. 6 oil can be significantly improved.
Use of No. 6 oil: There is no obvious proportional restriction on the use of No. 6 oil. Most of the use of No. 6 oil is based on the experience of the operator. However, the excessive addition of No. 6 oil will slow down the fixation of the ink on the printed matter, make the printed matter smeared on the back, and excessive penetration on the surface of the printed matter due to too thin ink, and surface crystallization.
3. Thinner (high boiling oil)
Its main component is high boiling point petroleum solvent. It is a mineral-type ink, and the addition of 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 diluent: Because the resin in mineral oil diluent and ink is soluble and insoluble (releasing), it should be added gradually under stirring to avoid precipitation of resin. Generally, the thinner's debonding effect is good. Generally, adding 1% can reduce a viscous unit. Note on the dosage in use as above.
4. 0 # Adjusting ink (No. 0 oil)
It is a kind of ink-adjusting oil. Its composition is similar to that of its own binder. Therefore, the application of ink-adjusting oil only changes the physical properties (fluidity) of the ink, and the role of 0 # 调 墨 油 is to Improve the cohesion of ink.
When some of the following situations occur, you need to add 0 # tune ink to the ink
â‘ It is necessary to improve the fixing force of the ink on the paper surface to make the imprint strong and strengthen the firmness;
â‘¡ Control ink emulsification and overcome floating dirt;
â‘¢ Reduce the penetration of the connection material on the paper, prevent oil penetration and powdering, and increase the gloss of the printed product.
â‘£ Used to overcome the pile-up phenomenon.
Use of 0 # Ink Adjusting Oil: Due to the high viscosity of 0 # Ink Adjusting Oil, there are often some difficulties when mixing with ink. The thick ink should be patted thoroughly with an ink knife, then add a small amount of the ink to be added to the ink, and then continue to pat, stirring in the ink.
Hue adjuster
1. Dilution agent (withdrawing agent)
The use of diluting agent is to dilute the color of printing ink and maintain its adhesion. The main components are aluminum stearate, dry vegetable oil, phenolic resin, beeswax, high boiling point kerosene and other materials. It is an ointment-like transparent substance specially designed for bright resin inks. Used as a color adjuster, it has excellent gloss and good printability.
Use of diluting agent: There is no limit to the proportion of the diluting agent in the preparation process of the ink. The specific ratio should be determined according to the hue of the ink to be obtained. In the preparation process of the extremely light color ink, the adjustment order should be paid attention to. The ink needs to be added to the diluent, which will make the deployment operation more convenient and accurate.
2. Transparent oil (dimensional force oil)
The main components of Veli oil are aluminum hydroxide and polymer oil. It has good printing performance and is generally mixed with resin ink. In addition to reducing the color saturation of the ink, it will also effectively reduce the vitrification problem. The amount should not exceed 1/3. Try not to use Velcro oil when printing the last color. , So as not to reduce the gloss of the ink layer.
Try to avoid using Velvet oil in quick-drying bright ink, otherwise it will cause the ink layer to lose luster, reduce dryness, and even cause gelation, etc.
3. White ink
Generally, it is not recommended to use, because the white ink itself has coarse pigment particles and poor printability. It is very easy to stack rubber, paste, emulsify during the printing process. The use of pale ink mixed with white ink will always make people It's a headache. But sometimes in some special cases, such as the need for a thicker, lighter ink layer with better hiding power, it is also needed. In order to change the printing suitability, we often mix white ink and gloss paste together, which can maintain the unique properties of white ink, can also improve the printing suitability of ink, and at the same time improve the gloss and adhesion of ink. benefit.
The specific method of use is the same as the usage of diluent.
4. Bright pulp
The main components of the bright pulp are high-grade synthetic resin, refined dry vegetable oil, gelling agent, solvent and other raw materials, which are refined at high temperature and are transparent paste-like pastes. It is mainly used for the dilution of fast-setting bright offset printing ink, but it can also be used as a dilution for various types of oil-based resin glue and lead ink, and is often used as an excellent auxiliary agent to improve the gloss of the ink.
Compared with the above adjuvant brightener, it has the following characteristics:
â‘ It can make the diluted ink have better printability.
â‘¡Ink that has been diluted with light paste can have the characteristics of strong gloss, moderate drying and clear dots of printed parts.
5. White oil
White oil is a diluent made from magnesium carbonate, stearic acid, polymer oil and other raw materials emulsified by heating and mixing. It is a milky white translucent ink-like paste. The printing suitability is not good, but the biggest advantage of white oil is that it is cheap, so white oil is often used as a diluent for low-grade light-color offset inks used by printing plants. The light-colored inks are sometimes printed better. Is used as a primer on the print.
Conclusion
Since the ink itself is configured according to a scientific formula before leaving the factory, each component has undergone strict inspection. Moreover, there is a balance between the ink components, and the addition of foreign components is bound to break the original balance, which will affect the quality of the ink. Avoid blindness in the process of using ink additives, and you must follow the principle of "add as few additives as possible, and do not add them if you can." It is easy not to believe the advantages provided by various additives.
Of course, the appropriate amount of scientific use of various additives can bring many benefits to the printing work and printing quality.
This article gives a brief introduction to the more common auxiliary agents in the production of offset printing. Of course, there are many ink auxiliary agents that can change and improve the ink properties to a certain extent in the offset printing work, such as spices, anti-smudge agents, etc. Because the use of these adjuvants is limited to relatively special purposes, or the application has gradually disappeared, it will not be introduced here.Backpack,Decorated with Shiny Letters,Fashion and Cute Kids Bag,Suitable For Computer Or Book
TAIZHOU ORCHIDLAND IMPORT&EXPORT CO.,LTD , https://www.orchidlandgifts.com