Introduction to the basic knowledge of the most po

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Introduction to basic knowledge of ink additives (III)

II. Anti desiccant (anti desiccant)

anti desiccant (anti oxidant, antioxidant, anti scaling agent) has the opposite effect with desiccant. Its main function is to prevent (inhibit) oxidation drying. It is an oxidation inhibitor. Is a negative catalyst

sterol and tocopherol in dry oil are all natural antioxidants. Their presence makes dry oil have an induction period before oxygen absorption and drying

most macromolecules can react with oxygen, leading to degradation or cross-linking. Especially under the action of heat and light, the rate of oxidation is faster

the oxidation of polymers is a free radical chain reaction (i.e. chain reaction). The function of anti desiccants is (1) to combine with free radicals to destroy the chain reaction of oxidation (generally speaking, they do not combine with free radicals of hydrocarbons); (2) Decompose hydroperoxide into stable substances that are no longer involved in chain reaction. It can also be considered that antioxidants are substances that can capture active free radicals and generate inactive free radicals, so as to stop the chain reaction, or can decompose the hydroperoxide produced by the polymer in the oxidation process to generate non free radical products, so as to interrupt the chain reaction

there are many kinds of antioxidants, including amine, phenol, ester, hydrazine, oxime, acid, etc., of which amine and phenol are the main

according to the action mechanism, there are two types of antioxidants: free radical inhibitor and peroxide decomposing agent. Free radical inhibitors, also known as main antioxidants, include two series of amines and phenols. Amine antioxidants are almost all derivatives of aromatic secondary amines, mainly including diaryl secondary amines, p-phenylenediamines, ketoamines, aldehyde amines, etc. Most of them have good anti oxygen performance, but the pollution is serious. Phenolic antioxidants are mainly hindered phenols, and their anti-oxidation efficiency is generally worse than that of amines, but the pollution is relatively light

peroxide decomposing agents, also known as auxiliary antioxidants, are mainly thioesters such as thiodiesters and phosphites

antioxidants also include copper inhibitors (also called metal passivators) and anti ozone agents, mostly hydrazine derivatives, oximes and aldehyde amine condensates. Some amine antioxidants have excellent anti ozone effect, but the Deyang bolixun battery he created by himself ended at the end of September, 2014 due to his arrest

among amine antioxidants, N-substituted derivatives of para isomers have the best effect. The activity of substituted p-phenylenediamines can be summarized as follows:

1. if the N-substituent is a secondary alkyl group, the trisubstituted compounds are more potent than the disubstituted compounds. If both substituents are secondary alkyl, the result is opposite

2. the activity of the secondary substituted alkyl group is greater than that of the primary group

3. if it is a trisubstituted compound, only one secondary substituted alkyl is more effective

4. the substitution of aromatic ring will reduce the activity of disubstituted and trisubstituted compounds

5. for disubstituted compounds, the activity of one substituent per nitrogen atom is higher than that of two substituents

6. when one alkyl group in the disubstituted compounds is replaced by one aryl group, the activity is greatly improved

among phenolic antioxidants, the effect of alkyl substituted phenols is better, and its application has an upward trend

alkyl substituted phenols are characterized by the space barrier to hydroxyl groups due to the alkyl substituents in both adjacent positions. These products are mainly obtained by butylation of phenols. For example, isobutylene reacts with cresol to obtain 2,6-di-tert-butyl-4-methylphenol. When treated with 2,4-dimethylphenol, 2,4-dimethyl-6-tert-butylphenol can be obtained

the potency of alkylphenols is related to the position and properties of substituents. Compared with phenol, the activity of mono substituted compounds on phenol ring is not significant. Binary substitution has a great influence, but the substitution effect at position 2 and 6 is better. The effect of ternary substitution is obvious when the position of 2,4,6 is used

amine antioxidants are more effective than phenols in overcoming induction period. Because the research and development of this kind of products is really very fast. In particular, the research on phenolic antioxidants is more active, and new varieties appear one after another. High efficiency, low toxicity and low price are the development direction of antioxidants in the future

butylated hydroxytoluene (bht-butylatedhydroxytoluene, antioxidant 264) is commonly used in China's ink industry

oxime antioxidants generally include Acetaldoxime, etc. Among them, butyraldehyde oxime is especially suitable for the application of phenolic resin dispersed in tung oil

to prevent ink peeling in the tank, in addition to antioxidant, dispersant can also be added to overcome it, such as acid dispersant (benzoic acid, crotonic acid, etc.), solvent dispersant (cyclohexanol, methyl cyclohexanol, turpentine, dipentene, etc.)

the most effective anti wrinkle agent is acetyleniccarboxylieacid.

since the anti desiccant can prevent the continuous action of the desiccant, it can increase the durability of the drying film. The use of antioxidant in the ink can prevent the film from wrinkling and reduce its peeling in the tank and on the machine

the use of antioxidant can also overcome the discoloration problem caused by metal dry oil. However, phenols have the disadvantage of discoloration in the presence of iron

their dosage is generally less than 2%, so as not to affect the printing drying

when using the anti desiccant, it should be taken with caution. It will be harmful if used improperly. If volatile oximes and hydrazine are used, there will be no worry

the above description is about chemical antioxidants. If you want to prevent ink scaling and drying on the printing machine, there is also a physical isolation method, that is, spray film-forming substances on the part of the printing machine with ink to isolate the ink from the air to prevent ink drying. Obviously, this layer is extruded and expanded - no matter when the film material is miscible with the ink

III. reverse gelling agent

the gelling, thickening and clumping of the ink system are roughly caused by the following factors: the soap is formed by the reaction of basic pigments with binders with high acid value or containing free fatty acids. Or because the binder itself coagulates and gels, the ink system absorbs water, and the pigment content in the ink system is too high; The binder used is inappropriate, and the miscibility of resin and grease in the binder is poor. In high polymer systems, the absorption of acid soluble structure by pigments will also promote gelation and so on

gelatinization caused by too thick or too high polymerization degree of binder can be overcome by adding appropriate diluted and soluble substances (aliphatic hydrocarbons, esters, ketones, etc.)

for the gelatinization type of reaction soap, high acid value substances such as rosin acid (rosin or calcium rosin acid dissolved in linseed oil), linseed oil fatty acid, maleic acid or maleic anhydride resin with high acid value (dissolved in linseed oil) can be added to hydrolyze. It is safer to add naphthoic acid metal salt to dissolve the gel, because the side effects of this material are small. For example, after adding many fatty acids, the ink may become oily, hydrophilic, and dry slowly in lithography, while adding naphthoic acid metal salt is more reliable. When making ink, sometimes add some aluminum naphthenate to increase the stability of the ink, which is the reason

substances that can restore the rheological properties of colloidal inks can be generally called anti gelling agents

the addition amount of degumming agent shall not exceed 5%

it is better to use the gelled ink in time after adding the anti gelling agent for degumming, otherwise it may still return

IV. diluting agent

diluting agent is also called diluting agent. Its function is to reduce the color intensity of the ink without basically changing the viscosity, other rheological properties and printing properties of the ink

glue, white oil and transparent oil in lead printing ink, ink blending oil and diluent in gravure printing ink, and some transparent and translucent base inks all play these roles

white oil is used for matching light color (commonly known as small color) during printing. Its main function is to dilute ink. Of course, it may also bring some changes in other features

formula example:

inking oil (4) 16%

wax oil 38%

aluminum hydroxide 29%

barium sulfate 15%

titanium dioxide 2%

wax oil is composed of 15% wax and 85% No. 4 inking oil

in the white oil system, there is also an emulsified water white oil, which is made by emulsifying (soaping) the vegetable oil type binder with sodium hydroxide aqueous solution, adding magnesium carbonate, aluminum hydroxide, wax, ester and other substances to disperse and roll. The advantage is low cost, but it has many disadvantages, such as instability and poor printing performance. With the development of emulsification technology, it may also be improved

transparent oil (commonly known as Weili oil) is a paste like transparent body formed by dispersing and rolling aluminum hydroxide and dry vegetable oil binder. It is generally expected that it will increase the luster of the ink by 2020, but in fact it is mainly used to fade. When diluting ink with binder alone, it will be too thin. Diluting with transparent oil will not have this disadvantage

formula example

inking oil (3) 10%

inking oil (4) 41%

inking oil (6) 4%

aluminum hydroxide 45%

recent transparent oils have tended to be made of synthetic resin binder and stable aluminum hydroxide (or some transparent calcium carbonate). This type of transparent oil has good drying performance and gloss

transparent oil can sometimes be used as finishing oil because of its good transparency. Of course, it is different from the varnish

clear oil is also a kind of colorless ink with excellent printing performance

The transparency index of transparent oil is one of its main quality indexes. Generally speaking, when the water content of transparent oil is about 20%, its transparency is good. If the quality of aluminum hydroxide meets the requirements (the water content should generally be about 25%), the temperature of the three roller mill can be controlled to control the water content of the transparent oil during rolling to ensure its transparency

in the factory that produces aluminum hydroxide by itself, if conditions permit, the extrusion method can be used to produce transparent oil. In this production method, the extruded base ink of aluminum hydroxide is first rolled twice on a three roll machine, then finely rolled, and then put

into an open pot with a steam jacket. At a temperature higher than 100 ℃, it is continuously stirred to order it to be dehydrated and transparent. Its dehydration control system software is WindowsXP operating system platform. Generally, it should be mastered a little too much to ensure transparency after cooling

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