Performance and Use of Offset Ink Cleaning Agents (Part 2)

Eight, ink cleaner species and development

According to information published at home and abroad, there are mainly four types of new printing ink cleaning agents used for replacing gasoline and kerosene: mixed solvent type, water-based cleaning agent, oil-in-water emulsion-type and semi-water-based cleaning agent. The following describes the performance of various types of printing ink cleaners, their preparation and use characteristics.
1, mixed solvent type cleaning agent.

This kind of ink cleaning agent still mainly uses the dissolving and cleaning effects of gasoline and kerosene, but in order to reduce its volatility and reduce its risk of flammability and explosiveness, a non-volatile high boiling point solvent is added to the formula, so that no Under the premise of influencing the cleaning effect, the safety in the cleaning process is improved. For example, an ink cleaning agent developed by Gong Guangfen et al. of the Hubei Provincial Chemical Research and Design Institute basically belongs to this type. They add a higher boiling point, less volatile hydrocarbon solvent to gasoline to form a mixed solvent. The added hydrocarbon solvent has an aromatic odor and is a kind of easily biodegradable. It can be used in the pharmaceutical industry. The environmentally friendly product of the agent (turpentine meets these conditions very much).

Since gasoline dissolves the ink faster, it has a lower boiling point and is more volatile. The other solvent added dissolves the ink at a slightly slower rate, but its boiling point is higher. When the two solvents are combined in a certain proportion, It can achieve the purpose of quickly dissolving ink and reducing volatility. Studies have shown that the distillation range can be increased to 260 degrees Celsius to 320 degrees Celsius when the two solvents are mixed 1:1, but the dissolution rate of the ink is greatly slowed down and is not suitable for use. When the ratio of gasoline to the added solvent is 3:1, the distillation range can be increased to a higher range of 150 degrees Celsius to 250 degrees Celsius, and there is better performance of dissolving the ink. Therefore, they believe that the 3:1 mixing can achieve the purpose of both dissolving the ink and reducing the solvent volatility. Because the ink composition is very complex, they also added some other ingredients in the mixed solvent to further improve the cleaning effect of this cleaning agent (better than a single component cleaning agent such as gasoline). For this purpose, they added the gasoline evaporation inhibitor N-1 produced by Wuhan Changjiang Chemical Plant into the formula. The surface film was formed by a combination of a polymembrane and a liquid monolayer. When it was added to volatile solvents such as gasoline, it was Can gather on the liquid surface to play a barrier role, so that the volatility of gasoline is greatly reduced. On the one hand, this greatly increases the flash point of gasoline (when it is more than 1 mm thick on the surface of the gasoline, the use of lighters will not ignite the gasoline), on the other hand, it will also greatly reduce the amount of gasoline lost during storage and transportation. In order to improve the cleaning efficiency, they also added surfactants to the formulation. The surfactants have wetting, penetrating, emulsifying, and dispersing effects on the ink and its film-forming substances, which can cause the ink and its film-forming substance to deviate from the printing roller. And blankets reach the purpose of cleaning. They found that the use of surfactants such as OP-10 (alkyl phenol ethoxylate) ABS-Na (sodium alkyl benzene sulphonate) did not work well (poor placement stability, poor cleaning results), and they added flat Although the cleaning effect is good, but the placement stability is very poor, for which they use a homemade sulfate surfactant (presumably alcohol ether sulfate AES), when the amount of up to 8% can achieve satisfactory cleaning effect and Good placement stability.

According to foreign data, the cleaning agent obtained by adding surfactant to this type of solvent-based cleaning agent has an advantage: it can be rinsed with water, and the oily soil is solubilized into the micelles of the surfactant during rinsing. It will not be deposited on the surface of the object to be cleaned, so it can avoid re-contamination of the object being cleaned. In order to reduce the damage of the cleaning agent to the printing machine and the rubber roller, they also added a mixture of anti-aging agents to improve the anti-rust ability on the one hand, and on the other hand to prevent the swelling, shrinkage and aging of the roller, so that the printing press and glue The service life of the roller is extended.

2, water-based cleaning agent.

The biggest advantage of water-based cleaning agent is that it is completely non-flammable, so it is very safe in use, its cleaning effect is achieved through the joint action of surfactant and alkaline additives. The mechanism of action has been described in detail in many articles and will not be further described here. A formula for printing ink cleaning agent is: 40% sodium silicate 75g, 97% NaOH 8g, octylphenol polyoxyethylene ether 30g, coconut oil dimethyl benzyl ammonium chloride 2g, add water to 1000g. In the preparation, the first two components are first dissolved in proportion to water, and then mixed with the latter two components. This is a cleaning agent that has strong detergency and does not have a detrimental effect on the pattern of the printing plate. The lithographic printing plate is placed on it. Soaking in this cleaning agent for 30 seconds, then scrubbing can be completely decontamination, printing will not appear stains 30,000 times.

3, oil-in-water emulsion liquid detergent.

This type of cleaning agent is an oil-in-water emulsion formed by adding a complex surfactant and other additives to a mixture of flammable organic solvents such as gasoline and water. Because the formula contains a large amount of non-flammable water, this kind of cleaning agent overcomes the disadvantages of the original cleaning agent flammable and explosive.

Other advantages of the oil-in-water emulsion cleaner include: reducing the amount of oil solvent in the formulation, avoiding its environmental pollution, and maintaining the good cleaning performance of the organic solvent on the ink; Oil-in-water emulsions, oils are dispersed, wrapped in water, greatly reducing its volatility; surfactants play a variety of functions such as wetting, infiltration, emulsification, and dispersion, which can increase the detergency of cleaning agents; The presence of water greatly improves the ability to clean water-soluble dirt.

Because the oil-in-water emulsion-type cleaning agent has the characteristics of low cost, simple and convenient preparation process, good cleaning effect, non-flammability, and safe use, it is causing widespread concern and research on this type of cleaning agent. For example, the type of cleaning agent developed by Yu Qiang et al. of Nanchang University is to add water-soluble fatty alcohol polyoxyethylene ether and oil-soluble dehydration to common solvents such as esters, ketones, ethers, alcohols and aromatics. Sorbitol fatty acid ester two surfactants (two surfactants formulated at a ratio of 1:3 to 1:4) Mixed surfactant emulsifier, addition of 5% to 10% aromatic alcohol additives It is made by dispersing with water for 30 to 40 minutes. Their study showed that the emulsifier was mixed with emulsifiers in the aqueous phase method (ie, the emulsifier was first added to the water and then the oil phase was added to obtain the most stable emulsion). The amount of emulsifier has an effect on the stability and cleaning effect of the emulsion, and the effect is best when the amount of emulsifier is 7%. The content of the organic solvent in the emulsion is 20% to 25% (volume ratio), and the stability and cleaning power are the best.

Another oil-in-water emulsion liquid detergent developed by Wang Yimin, of the Chemical Engineering Department of Tangshan University, Hebei Province, uses an oil solvent that is a mixture of 310# color ink solvent oil and 200# solvent oil. The distillation range of this mixed solvent is wider. It also has better solubility than a single solvent. The surfactants used were OP-10 (alkylphenol polyoxyethylene ether) and LAS (sodium alkyl benzene sulphonate). In order to reduce the corrosion of the cleaning agent on the printing machinery, triethanolamine and benzotriazole were also added. Anti-rust agents, triethanolamine have a role in regulating PH value, emulsion stability, and cleaning ability. A small amount of n-butanol is also added to enhance the stability and penetration of the cleaning agent. The specific formula is: 310# special solvent oil 25%, 200# solvent oil 15%, OP-10 1.5%, LAS 2.5%, other additives 5%, add water to 100%. In the preparation, the solvent oil and OP-10 are mixed to form phase A, LAS, triethanolamine and water are mixed into phase B, phase B is heated to 55 degrees Celsius and added to phase A under stirring, and formed under high-speed stirring or colloidal grinding Emulsion. The final addition of other additives is the finished product.
4, semi-water-based ink cleaner.

In foreign countries, semi-water-based cleaning agents are often used to clean printing inks. Semi-water-based ink cleaning agents are similar to emulsion-based cleaning agents in terms of composition and performance. Both are organic solvents, water, and surfactants. Three main components. All have the advantages of simultaneously dissolving and removing oily dirt and water-soluble dirt, and overcome the disadvantages of poor safety of flammability and explosiveness of the original solvent.

The difference between the two are as follows: From the outside, the semi-aqueous cleaning agent is transparent, while the emulsion is white and opaque; the semi-aqueous cleaning agent contains less water, generally between 5% and 20%. Between, while the water content in the emulsion can vary within a wide range. Since the emulsion contains less organic solvent, its ability to clean the ink is not as good as that of the semi-aqueous base cleaner. Since the emulsion is a metastable state, the emulsion sometimes breaks in use. Layering and other phenomena. In addition, the semi-water based cleaning agent can not be diluted by using the original liquid produced by the manufacturer, and the manufacturer of the oil-in-water emulsion type cleaning agent sometimes produces concentrated liquid, which can be diluted with water according to actual needs in the application.

Semi-water based ink cleaning agent also has good cleaning performance, due to its high content of solvent oil in the composition of the strong cleaning ability of the ink, and can be used in conjunction with ultrasonic cleaning, and overcome the disadvantages of solvent oil flammable and explosive (semi-water base The flash point of the ink cleaning agent can be increased to more than 100 degrees Celsius) so it is welcomed abroad. However, compared with the emulsion-type cleaning agent, the cost is relatively high, and the management in use is complicated, so it has not been widely applied in China.

Nine, the use of ink cleaning agent

The method of using the ink cleaning agent is basically the same as the method of cleaning with gasoline and kerosene. Before use, the bottled ink cleaning agent is shaken several times, then poured into a mineral water bottle and covered with the dispensing nozzle (don't screw the mouth too Tight) for cleaning operations.

1, when cleaning, let the machine automatically overrun, as far as possible with a black ink scraper scraping the ink fountain roller and ink roller, and then use sponges, cloth and other substances absorb ink cleaning agent, wipe the ink on the fountain and the ink fountain roller.
2. When cleaning the ink roller, do not press down the blade first, and evenly spray the ink cleaning agent on the rotating ink roller. To ensure smooth rotation of the ink roller, spray as much as possible. With the rotation of the ink roller, the ink cleaning agent dissolves and emulsifies the ink on the ink roller in about 30 seconds. At this point the blade is pressed down, the dissolved and emulsified ink is scraped off, and then rinsed with water. Depending on the cleaning situation, repeat this 1-3 times to clean it. The final flush volume is based on cleanliness.
3. When using an ink cleaner to clean the plate, it should be carried out according to the normal cleaning agent's operating procedures.
4. Note: When using the ink cleaning agent, please check whether the squeegee on the printing machine is good, and use the hard paper towel to scrape off the residual ink at the time of cleaning so as to accelerate the cleaning speed. Save on cleaning and reduce cleaning costs.

X. Insufficiency and Development Direction of Ink Cleaning Agents

In summary, cleaning agents traditionally used for cleaning printing inks are gasoline or kerosene. In order to overcome the disadvantages of its flammable and explosive pollution environment, people have developed a variety of new printing ink cleaning agents, including mixed solvent type and oil-in-water. Emulsions and semi-water based cleaners not only maintain the original solvent's strong ability to clean the ink, but also overcome its inflammable and explosive disadvantages to a large extent. The water-based cleaning agent is completely non-flammable, but the cleaning effect of some inks is not ideal, so it should be selected according to actual needs in use.

Ink cleaning agent is a cleaning agent specially used for cleaning ink. Compared with gasoline and kerosene, the qualified ink cleaning agent has good cleaning effect, high safety performance, and little harm to the human body and the environment, but the price is relatively high. Although ink cleaning agents are safe and less polluting than steam and kerosene, they do not mean that "ink cleaning agents" are perfect.

First of all, although most of the qualified ink cleaners have a flash point of over 40 degrees and a maximum of 200 degrees, they are still flammable. If the process is not properly performed, there is still the possibility of explosion. Secondly, although the ink cleaning agent itself produces less pollution to the human body and the surrounding environment than steam and kerosene, it does not mean that he does not pollute; like ink and kerosene, the ink dissolved in the "ink cleaning agent" And other substances created for the human body and the surrounding environment