Blanket: It is more suitable to use UV. Because UV varnish makes it easier for the rubber to expand than UV inks, it is recommended to use UV-specific ones.
Cleaning fluid: Oily cleaning fluid cannot be used. After the cleaning operation, it should be cleaned by cleaning. If it is directly coated with cleaning fluid, it will greatly affect the drying time of the varnish. Therefore, it is better to use a more volatile cleaning fluid.
UV curing device: According to the drying mechanism of UV varnish and other various conditions required to select the appropriate UV lamp. It should be noted that the UV varnish uses a homogenous initiator with little yellowing. The initiator absorbs ultraviolet rays at a wavelength of 365 nm, and ultraviolet rays having a wavelength of 253 nm must be used. From the curing efficiency point of view, high-pressure mercury lamps are generally better than metal halide lamps, and metal halide lamps are better than no-ozone lamps (there is no use of ozone-free lamps, and the efficiency of the use of ozone lamps is greatly affected, so do not use them as much as possible).
Storage: Use UV light to avoid direct sunlight and store in a cool place below 30 degrees Celsius. When adjusting the viscosity by heating, avoid high temperatures or prolonged heating so as not to cause gelation or deterioration of the varnish.
Labor protection: UV varnish is irritating to the skin, and is non-volatile. When it is attached to the skin or clothes, it may enter the skin and cause inflammation with sweat if it is in the hot summer weather. Therefore, if the skin is stained with UV Varnish, it should be washed with soapy water as soon as possible, and change the clothes.
VI. Problems to be solved and future development directions
UV coating materials have the advantages of high processing speed, high gloss, abrasion resistance, and blocking resistance. In the box making process or circulation process is not easy to damage, product appearance, rapid development in recent years. Initially subject to price constraints, but as the amount increases, prices gradually decline. If all aspects of processing speed and quality are taken into consideration, the overall cost will not be much worse than that of general varnish coating or calendering, and thus it will be accepted by customers. Currently, the proportion of UV varnish in the paper printing industry is increasing. Gradually increase. However, the following problems still need to be solved in UV varnish.
1) Although the odor is gradually developing toward a low odor, odor problems still exist. In the future, it is necessary to increase the molecular weight and reactivity of prepolymerization, monomers, etc., and develop odorless materials including photoinitiators.
2) Safety The currently used sharp diluent, although the skin irritation (pH) is 3 or less, it is necessary to further develop a reactive diluent with a PH value of 1 or less to improve product safety.
If we can produce more environmentally friendly Varnish in the future, I believe that the demand will increase.
In addition, UV varnish is inferior to water varnish in terms of odor and food hygiene. UV coatings have not been approved by the FDA (US Food and Drug Administration) and cannot be in direct contact with food.
3) Adhesion on oxidative polymerization ink Printing trays and publications generally use oxidized polymeric offset inks. Some printers also use relatively high-priced UV inks to reduce dusting processes and improve station attachment.
Applying UV varnish to an oxidative polymerization type ink may cause odor, low gloss, and the like, and the adhesion to an oxidative polymerization type ink is not ideal. Although off-line processing can be applied in the middle of the coating, and then coated with UV light oil, but the two-layer coating to increase the cost, so need to improve the compatibility of UV Varnish and oily ink.
4) Recycling of UV-Coated Paper Although UV-processed paper has good film properties, there are still some problems with paper regeneration. In particular, the solvent-free UV varnish coating is required to be improved in the future due to the high cross-linking density and difficulty in recycling the paper.
5) Reducing costs In recent years, although it has dropped a lot, it is still too high compared with the general inks, and it is necessary to further reduce the operating costs of varnish, coating cost, and irradiation equipment.
On the whole, UV light oil has the above problems. However, UV varnish has great advantages in protecting the environment, saving energy, simplifying operations, and increasing the added value of products. With the advent of UV technology, there will be greater development in the future.
Cleaning fluid: Oily cleaning fluid cannot be used. After the cleaning operation, it should be cleaned by cleaning. If it is directly coated with cleaning fluid, it will greatly affect the drying time of the varnish. Therefore, it is better to use a more volatile cleaning fluid.
UV curing device: According to the drying mechanism of UV varnish and other various conditions required to select the appropriate UV lamp. It should be noted that the UV varnish uses a homogenous initiator with little yellowing. The initiator absorbs ultraviolet rays at a wavelength of 365 nm, and ultraviolet rays having a wavelength of 253 nm must be used. From the curing efficiency point of view, high-pressure mercury lamps are generally better than metal halide lamps, and metal halide lamps are better than no-ozone lamps (there is no use of ozone-free lamps, and the efficiency of the use of ozone lamps is greatly affected, so do not use them as much as possible).
Storage: Use UV light to avoid direct sunlight and store in a cool place below 30 degrees Celsius. When adjusting the viscosity by heating, avoid high temperatures or prolonged heating so as not to cause gelation or deterioration of the varnish.
Labor protection: UV varnish is irritating to the skin, and is non-volatile. When it is attached to the skin or clothes, it may enter the skin and cause inflammation with sweat if it is in the hot summer weather. Therefore, if the skin is stained with UV Varnish, it should be washed with soapy water as soon as possible, and change the clothes.
VI. Problems to be solved and future development directions
UV coating materials have the advantages of high processing speed, high gloss, abrasion resistance, and blocking resistance. In the box making process or circulation process is not easy to damage, product appearance, rapid development in recent years. Initially subject to price constraints, but as the amount increases, prices gradually decline. If all aspects of processing speed and quality are taken into consideration, the overall cost will not be much worse than that of general varnish coating or calendering, and thus it will be accepted by customers. Currently, the proportion of UV varnish in the paper printing industry is increasing. Gradually increase. However, the following problems still need to be solved in UV varnish.
1) Although the odor is gradually developing toward a low odor, odor problems still exist. In the future, it is necessary to increase the molecular weight and reactivity of prepolymerization, monomers, etc., and develop odorless materials including photoinitiators.
2) Safety The currently used sharp diluent, although the skin irritation (pH) is 3 or less, it is necessary to further develop a reactive diluent with a PH value of 1 or less to improve product safety.
If we can produce more environmentally friendly Varnish in the future, I believe that the demand will increase.
In addition, UV varnish is inferior to water varnish in terms of odor and food hygiene. UV coatings have not been approved by the FDA (US Food and Drug Administration) and cannot be in direct contact with food.
3) Adhesion on oxidative polymerization ink Printing trays and publications generally use oxidized polymeric offset inks. Some printers also use relatively high-priced UV inks to reduce dusting processes and improve station attachment.
Applying UV varnish to an oxidative polymerization type ink may cause odor, low gloss, and the like, and the adhesion to an oxidative polymerization type ink is not ideal. Although off-line processing can be applied in the middle of the coating, and then coated with UV light oil, but the two-layer coating to increase the cost, so need to improve the compatibility of UV Varnish and oily ink.
4) Recycling of UV-Coated Paper Although UV-processed paper has good film properties, there are still some problems with paper regeneration. In particular, the solvent-free UV varnish coating is required to be improved in the future due to the high cross-linking density and difficulty in recycling the paper.
5) Reducing costs In recent years, although it has dropped a lot, it is still too high compared with the general inks, and it is necessary to further reduce the operating costs of varnish, coating cost, and irradiation equipment.
On the whole, UV light oil has the above problems. However, UV varnish has great advantages in protecting the environment, saving energy, simplifying operations, and increasing the added value of products. With the advent of UV technology, there will be greater development in the future.
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