Offset printing is indirect printing. During the printing process, the blank part of the printing plate is first wetted with water, then passes through the ink roller, and the ink affixes the graphic part, and then the ink on the graphic is transferred to the printing material through the blanket.
At present, most of China's books and periodicals (over 2/3) use offset printing; central and provincial prefecture-level newspapers and periodicals have all eliminated lead printing and achieved offset printing; in the packaging industry, more than 500 offset printing presses have been imported, and the number of them has far exceeded. The number of gravure printing lines is more than 200 units. In the entire printing industry, offset printing has become a very important printing method.
During the offset printing process (after a color change or shutdown) it is often necessary to clean the ink on the ink roller and the blanket. To remove the ink very well, first of all, the composition of the offset printing ink should be solved.
Generally speaking, the upper components of the offset printing ink are: 48% solid resin, 6% liquid resin, 20% colloidal oil, 5% wax, 2% aluminum carbonate, and 15% pigment.
The removal process is actually the use of a suitable solvent to dissolve the resin components to achieve the purpose of removal.
The resin in the printing ink is generally a phenolic resin, and commonly used resins include a rosin-modified phenolic resin, an alkyd resin and a polyurethane alkyd resin. To clear them, find the solvent that will dissolve these resins. According to the principle of similar dissolution (that is, a solvent of a polar gene dissolves a substance having a polar gene, a non-polar solvent dissolves a non-polar substance) and a solubility parameter theory (for non-polar molecular systems, usually the dissolution of a polymer For the solvent and solutes, the solubility parameters are as close as possible to facilitate dissolution.) A solvent can be found. The solvent should have the following properties:
a. Has a high solubility.
b. Faster volatilization rate.
c. Strong permeability.
d. Good adsorption wetting.
e. Harmless to the human body, the use of the party.
f. Basically no corrosion on blankets and rollers.
g. low cost.
The solubility parameters of the phenolic resin are between 8 and 11.5, and the solubility parameters of the main solvent in the cleaning agent should also be in this range. The solubility of ketones, xylenes, diethylene glycol, valerolactone, etc. is in this range, so that one or two of them are selected as the solvent. After testing, using valerolactone and dimethylbenzene as a common solvent for inks and photoresists, the solubility is good, so choose the two components of the mixture as a solvent; you can also choose to use hydrocarbon solvents, such as n-g Alkane, high boiling point kerosene and other solvents adjust the volatilization rate of the entire solution; due to the strong permeability of binary lower halogenated hydrocarbons such as 1,1,1-trichloroethane, they can be used as penetrants for cleaning agents; anions are added. Surfactants improve the wetting and dispersing properties of solutions. OP-10 is a non-ionic surfactant that is easy to disperse and has good hydrophilic oleophobicity. It can be used with an anionic surfactant as oil/water. Emulsifier penetrant. Because its solubility in cold water is greater than in hot water, it is ideal as an emulsifier. The ideal formula for cleaning agents can be this:
Solvent: 45%
Solubilizer: 30%
Penetrant 5%
Thinner: 15%
Emulsifier: 5%
However, the above-mentioned cleaning agent has a significant disadvantage in that the amount of the solvent is high, and the volatilization in the printing shop is very serious, which has a serious impact on the printing environment and the health of workers, and the cost is high. Therefore, many printers simply use gasoline as a cleaning agent. Is this inappropriate? Obviously, the decline in printing costs at the expense of the environment and the health of workers is certainly wrong.
Before and after the 1990s, European countries and European countries passed the Environmental Protection Law (VOC). According to the provisions of the law, all organic fertility must meet the following requirements:
1. There should be no smell of organic solvents outside the job shop.
2. The concentration of volatile substances in the job shop must be lower than:
1) Volatile organic solvents 50 m/m 3 2) Carbon monoxide 100 mg/m 3 3) Nitric oxide 100 mg/m 3 It is clear that this law is closely related to the printing industry.
In the face of VOC law, printing houses in Western countries must strictly abide by it, even at the expense of printing quality and raising costs.
While considering the development of the printing industry, China must also look at the issue from the perspective of environmental protection: In the printing industry, the emission of harmful gases and the use of hazardous liquids and solids and the discharge of waste should be strictly controlled.
In view of the fact that China’s government has already taken environmental protection as a basic national policy and must realize the coordinated development of economic construction and environmental protection and the sustainable development of the national economy, they must consider the issue of environmental protection when formulating plans for the development of the printing industry. Formulate practical and effective measures.
Some of the cleaning agents originally used in the printing industry in China are poisonous in their own right, and all of the solvent's hydrocarbon emissions cause pollution to the atmosphere. At the same time, the cleaning agents used in the offset printing process must be thoroughly reformed.
In order to limit pollution and satisfy the VOC law, printing plants generally use water-in-oil emulsion cleaners to clean rubber rollers and blankets. Water-in-oil emulsion cleaners can not only completely eliminate the dangers of certain harmful substances in solvent-based cleaning agents to printing workers, prevent organic solvents from polluting the atmosphere, but also greatly increase the flash point of cleaning agents and improve the fire safety of printing workshops. To improve the quality of the overall environment. The so-called water-in-oil emulsion type cleaning agent means that the cleaning agent is made into an emulsion, and the external phase is oil (oil or solvent); the internal phase is water; and the interface uses a surfactant as a stabilizer. Due to the presence of water, the volatility of the oil or solvent of the external phase is greatly reduced, and the content of organic volatiles in the air is greatly reduced. And the presence of water greatly increases the flash point of the solution; it increases the fire safety of the printing shop.
The key to the study of water-in-oil emulsion cleaners is to find suitable solvents and surfactants to solve the problems of cleaning speed, protection of blankets and rollers, and emulsion stability. This requires a lot of repeated experiments.
Its reference formula is as follows:
Solvents and Solubilizers: 45%
Surfactant: 5%
Water: 50%
Although water-in-oil emulsion cleaners have some unsatisfactory qualities, such as the best quality cleaner, the drying rate is not as fast as gasoline, but analyzing the advantages and disadvantages, it should be the cleaning agent of the printing shop. .
At present, there are different grades of cleaning agents on the market, and high-grade cleaning agents should have faster cleaning and drying speeds, have no impact on rubber blankets and rubber rollers, and the solvents they use meet the requirements of green environmental protection. Low-grade cleaners are lacking in the impact on the factory's rubber and plastic bottles, or they are slow to clean.
At present, most of China's books and periodicals (over 2/3) use offset printing; central and provincial prefecture-level newspapers and periodicals have all eliminated lead printing and achieved offset printing; in the packaging industry, more than 500 offset printing presses have been imported, and the number of them has far exceeded. The number of gravure printing lines is more than 200 units. In the entire printing industry, offset printing has become a very important printing method.
During the offset printing process (after a color change or shutdown) it is often necessary to clean the ink on the ink roller and the blanket. To remove the ink very well, first of all, the composition of the offset printing ink should be solved.
Generally speaking, the upper components of the offset printing ink are: 48% solid resin, 6% liquid resin, 20% colloidal oil, 5% wax, 2% aluminum carbonate, and 15% pigment.
The removal process is actually the use of a suitable solvent to dissolve the resin components to achieve the purpose of removal.
The resin in the printing ink is generally a phenolic resin, and commonly used resins include a rosin-modified phenolic resin, an alkyd resin and a polyurethane alkyd resin. To clear them, find the solvent that will dissolve these resins. According to the principle of similar dissolution (that is, a solvent of a polar gene dissolves a substance having a polar gene, a non-polar solvent dissolves a non-polar substance) and a solubility parameter theory (for non-polar molecular systems, usually the dissolution of a polymer For the solvent and solutes, the solubility parameters are as close as possible to facilitate dissolution.) A solvent can be found. The solvent should have the following properties:
a. Has a high solubility.
b. Faster volatilization rate.
c. Strong permeability.
d. Good adsorption wetting.
e. Harmless to the human body, the use of the party.
f. Basically no corrosion on blankets and rollers.
g. low cost.
The solubility parameters of the phenolic resin are between 8 and 11.5, and the solubility parameters of the main solvent in the cleaning agent should also be in this range. The solubility of ketones, xylenes, diethylene glycol, valerolactone, etc. is in this range, so that one or two of them are selected as the solvent. After testing, using valerolactone and dimethylbenzene as a common solvent for inks and photoresists, the solubility is good, so choose the two components of the mixture as a solvent; you can also choose to use hydrocarbon solvents, such as n-g Alkane, high boiling point kerosene and other solvents adjust the volatilization rate of the entire solution; due to the strong permeability of binary lower halogenated hydrocarbons such as 1,1,1-trichloroethane, they can be used as penetrants for cleaning agents; anions are added. Surfactants improve the wetting and dispersing properties of solutions. OP-10 is a non-ionic surfactant that is easy to disperse and has good hydrophilic oleophobicity. It can be used with an anionic surfactant as oil/water. Emulsifier penetrant. Because its solubility in cold water is greater than in hot water, it is ideal as an emulsifier. The ideal formula for cleaning agents can be this:
Solvent: 45%
Solubilizer: 30%
Penetrant 5%
Thinner: 15%
Emulsifier: 5%
However, the above-mentioned cleaning agent has a significant disadvantage in that the amount of the solvent is high, and the volatilization in the printing shop is very serious, which has a serious impact on the printing environment and the health of workers, and the cost is high. Therefore, many printers simply use gasoline as a cleaning agent. Is this inappropriate? Obviously, the decline in printing costs at the expense of the environment and the health of workers is certainly wrong.
Before and after the 1990s, European countries and European countries passed the Environmental Protection Law (VOC). According to the provisions of the law, all organic fertility must meet the following requirements:
1. There should be no smell of organic solvents outside the job shop.
2. The concentration of volatile substances in the job shop must be lower than:
1) Volatile organic solvents 50 m/m 3 2) Carbon monoxide 100 mg/m 3 3) Nitric oxide 100 mg/m 3 It is clear that this law is closely related to the printing industry.
In the face of VOC law, printing houses in Western countries must strictly abide by it, even at the expense of printing quality and raising costs.
While considering the development of the printing industry, China must also look at the issue from the perspective of environmental protection: In the printing industry, the emission of harmful gases and the use of hazardous liquids and solids and the discharge of waste should be strictly controlled.
In view of the fact that China’s government has already taken environmental protection as a basic national policy and must realize the coordinated development of economic construction and environmental protection and the sustainable development of the national economy, they must consider the issue of environmental protection when formulating plans for the development of the printing industry. Formulate practical and effective measures.
Some of the cleaning agents originally used in the printing industry in China are poisonous in their own right, and all of the solvent's hydrocarbon emissions cause pollution to the atmosphere. At the same time, the cleaning agents used in the offset printing process must be thoroughly reformed.
In order to limit pollution and satisfy the VOC law, printing plants generally use water-in-oil emulsion cleaners to clean rubber rollers and blankets. Water-in-oil emulsion cleaners can not only completely eliminate the dangers of certain harmful substances in solvent-based cleaning agents to printing workers, prevent organic solvents from polluting the atmosphere, but also greatly increase the flash point of cleaning agents and improve the fire safety of printing workshops. To improve the quality of the overall environment. The so-called water-in-oil emulsion type cleaning agent means that the cleaning agent is made into an emulsion, and the external phase is oil (oil or solvent); the internal phase is water; and the interface uses a surfactant as a stabilizer. Due to the presence of water, the volatility of the oil or solvent of the external phase is greatly reduced, and the content of organic volatiles in the air is greatly reduced. And the presence of water greatly increases the flash point of the solution; it increases the fire safety of the printing shop.
The key to the study of water-in-oil emulsion cleaners is to find suitable solvents and surfactants to solve the problems of cleaning speed, protection of blankets and rollers, and emulsion stability. This requires a lot of repeated experiments.
Its reference formula is as follows:
Solvents and Solubilizers: 45%
Surfactant: 5%
Water: 50%
Although water-in-oil emulsion cleaners have some unsatisfactory qualities, such as the best quality cleaner, the drying rate is not as fast as gasoline, but analyzing the advantages and disadvantages, it should be the cleaning agent of the printing shop. .
At present, there are different grades of cleaning agents on the market, and high-grade cleaning agents should have faster cleaning and drying speeds, have no impact on rubber blankets and rubber rollers, and the solvents they use meet the requirements of green environmental protection. Low-grade cleaners are lacking in the impact on the factory's rubber and plastic bottles, or they are slow to clean.
Alloy Watch,Fashion Style Silicone Band Watch,Fashion Watch
Wooden Watch Co.,Ltd , http://www.nsallwatch.com