Basic knowledge of ink additives (1)

Additives (adjuvants) refer to some materials added around the ink and added to improve the properties of the ink during printing. Also known as additives. That is to say, inks formulated according to their basic composition still cannot meet the requirements in certain characteristics, or cannot be satisfied due to changes in conditions (such as deterioration of ink after long-term storage, air temperature conditions, printing conditions, paper conditions, etc.). When printing requirements are applied, a small amount of auxiliary materials must be added to solve the problem. This material is called additive.

Their contents are quite extensive, and almost every type of ink has its own unique additives. Of course, many of them are mutually versatile. Additives are sometimes called adjusters.

The names of the additives are numerous. Some of them are listed below:

1. Desiccant (Drier).

2. Anti-desiccant - anti-oxidants, anti-skinning agents (Anti-Oxidant, Anti-Skinning Agents).

3. Anti-Gelling Agents.

4. Withdrawal (Diluents, ExtendingVarnishMedium).

5. Reducer (TackReducingCompound).

6. Thinner.

7. Anti-Off-Set Agents (Non-offsetCompound).

8. Anti-foam agents (Antifoam Agents).

9. Plasticizers.

10. Perfume.

11. Preservatives.

12. Stabilizers.

13. Surfactants - Dispersants, Wetting Agents (Surface Active Agents, Surfactants, rsion Agents, Wettng Agents).

14. Thickeners - anti-settling agents, suspending agents (Thickening Agents, Suspension Agents).

15. SlipComPound.

16. Non-skid compound (Non-Skid Compound).

17. Anti-Pinho1eComPound.

18. Anti-dirty agent (Non-scum Compound).

19. UV Absorber - UV Absorber.

In the past, due to the influence of Western culture, some additives in the ink industry have been literally translated into ComPound, which is actually not appropriate.

The main components of naphthalene acid are:

1. Saturated cyclic carboxylic acid, its general formula: CnH2n-1COOH.

2. Saturated bicyclic carboxylic acids having the general formula: CnH2n-3COOH.

3. Aliphatic carboxylic acids have the general formula: CnH2n+1COOH.

The carbocyclic ring in the saturated monocyclic carboxylic acid is a five-membered ring. The metal soap formed from naphthenic acid is relatively stable and has good solubility. The disadvantages are dark color, odor, and low metal content. Refined naphthalene acid is lighter in color.

In addition to naphthalene acid, synthetic acids containing 8 to 13 carbon atoms are also widely used for the production of desiccants. The acidity of this type of acid is relatively high, the quality is consistent, the color is light, and there is no unpleasant odor. For example, octacarbonic acid (Oetoate), namely 2-Ethyl Hexoic Acid, abbreviated as caprylic acid. In addition, there are neo-decanoic acid eodecanoate etc. Desiccants made with such acids have a relatively high metal content. Its solubility, mixability, etc. are also very good. It is more effective than naphthalene and octadecyl.

The metals used to make desiccants are roughly the following: drilling, manganese, lead, antimony, vanadium, niobium, iron, lithium (the above belongs to oxidation-oxidation polymerization catalysts); aluminum, zirconium (above belongs to the value-added dry type) Calcium, zinc, phenanthroline (above, auxiliary drying type).

Among the metals that are of general interest are cobalt, manganese, and lead.

The most active metals are cobalt, vanadium, and manganese. The activity of nickel and copper is zero. Delaying the dry metal is almost impossible. Each metal has its own unique effect, and its properties vary, in addition to its activity.

Cobalt is purple, its main function is to promote the surface oxidation, that is, the surface energy quickly forms a layer of film, so after a lot of use there will be severe dry skin, wrinkles. Therefore, drilling dry oil known as "surface dry oil" is the most powerful desiccant.

Manganese is a brown substance, and its performance is somewhat like that of a drill, but its effect is small. It can accelerate drying (oxidation) of oil and the effect of peeling is not obvious. Dryness is poor at low temperatures, often with a large amount of lead.

The oxidation of lead is poor, and its characteristics are that the layer film thickens together. So the dry oil is called "through" dry oil. The surface of the film dried with lead does not have a skin. It is less sensitive to temperature, which means that heating will not promote lead to play a greater role. Often used with manganese.

The effect of calcium is poor, and the effect is acceptable when used with cobalt. There is instability in the use of lead dry oil in some of the binders, but when using calcium dry oil, the situation is much better.

Iron is darker in color.

First, desiccant

Desiccant, also known as reminder 1000, or simply dry oil, dry oil, etc., is a positive catalyst. Adding unsaturated substances such as lipids to self-oxidation accelerates drying of the conjunctiva of these unsaturated substances. Dry oils have the property of unsaturated double bond, which is the key to enable it to change from a liquid to a solid after oxygen absorption, and to dry from a small molecule to a large molecule. Desiccant is used to shorten the process of this change.

Although the mechanism of the desiccant in unsaturated oils and fats and their binders is not very clear at present, there have been some fairly consistent statements in recent years.

For example, adding salt to the linoleic acid methyl ester can form an unstable complex of different components with the unsaturated esters, thereby accelerating the proportion of oxygen absorbed, and the activation energy after adding cobalt can be Increase about eight times. With the constant absorption of oxygen, the number of hydroxyl groups and/or hydroperoxide groups also increase accordingly, thereby increasing the conjugation and shifting from cis to trans, and polymerization occurs later.

It has also been considered that the contact oxidation of unsaturated soaps by metal soaps proceeds through the production of free carboxyl groups by metal salts, and the (generally) hydrogen atoms on these α-methylene carbon atoms initiate the chain reaction. From the “self-oxidation” of commonly used oils, it can be seen that polyvalent metals can accelerate the decomposition of hydroperoxides, which is the function of desiccants.

Materialist dialectical method believes that external cause is the condition of change, internal cause is the basis of change, external cause works through internal factors, and the drying performance of grease (or linking material) mainly depends on its own performance. Desiccant is only a condition. In a saturated fat, even if a desiccant is added, it does not work. This is the reason.

After adding the desiccant to the grease (or binder), the following objectives can be achieved:

1. Before induction of oxygen, overcome or shorten the induction period.

2. Increase oxidation rate.

3. Change the type and amount of volatile oxidation products.

4. Change the nature of molecular orientation in the membrane.

(a) The composition of the desiccant

Desiccants can generally be divided into two major categories: (1) dissolved (metal) desiccants; (2) dispersed desiccants.

In the first category, there are mainly heavy metal soaps of organic acids whose composition is organic acids and metals.

Among organic acids, linolenic acid, resin (rosin) acid, and wood pulp oleic acid are oxidizable acids and change during storage. Naphthenic acid and octacarbonic acid are relatively stable because they are saturated organic acids.

It is very important that the system (or solution) of the compound formed by metal and organic acid maintains good solubility and stability, and this has a great relationship with organic acids. Now we tend to use saturated organic acids instead of easily oxidized acids, that is from this point of view.

On the other hand, since the desiccant is easy to leach out of the ink and chemically react with the offset ink in the offset printing, thereby reducing the dryness of the ink, the selection of the organic acid in the desiccant is very important. In general, the new synthetic acids are ideal. They are easy to form organic metal bonds without making the metal leach out. The wood pulp oleic acid, naphthoic acid, etc. are relatively large because of their organic groups, and they are unlikely to form organic metals. chain. Petroleum acid (naphthoic acid, naphthenic acid) is present in crude oil, and is industrially treated with alkali to treat crude oil and then separated, acidified, and then subjected to fractionation, the composition of which varies depending on the oil source.