How to eliminate gas smell
(1) The packaging and printing factory shall request the supplier to use the monomers, oligomers and photoinitiators with the least odor in the production of UV varnish, adopt suitable formulas, and have both surface curing and post-curing effects.
(2) On the premise of ensuring quality, packaging and printing plants should use UV varnish with a solid content of at least 99.5:6 to reduce vehicle speed, increase the number of UV lamps, or increase power.
(3) Adjust the ventilation system of the light box and ensure good ventilation in the workshop to prevent the product from absorbing residual odor during the placement.
(4) The paper supplier is required to pre-coat the reverse side of the paper, so that the original fluffy back texture becomes tight and airtight, thereby greatly reducing the chance of odour entering the interior of the paper.
Through these treatments, we quickly solved the odor problem.
Use caution
In fact, there are also some problems in the use of UV varnish in other areas, and we need to pay attention to it during our work. When the use of UV Varnish is used, the following methods can be used for prevention and control.
1. UV lamp inspection
UV light sources generally use high-pressure mercury lamps, and their output power is generally 80-1 20W/cm. For UV lamps, regular inspections are required to ensure the power stability of the light source to ensure the UV varnish coating curing effect.
2. Paper check'
The main reason for the poor adhesion of the prints and the impatience of friction is the unsuitable surface tension of the paper. In addition, the paper used for the UV coating product should be pre-coated to avoid absorption of the UV varnish odor on the back side of the highly permeable paper.
3. UV Varnish Inspection
The ink odor can be checked directly before printing, and inks produced with odor-less monomers, oligomers, and photoinitiators are selected; after printing, UV gloss oil with good flatness and gloss is selected for coating.
4. Varnish control
After the coating of the varnish is exposed to ultraviolet light, the photoinitiator reacts to generate free radicals or ions. These free radicals or ions crosslink with the double bond in the prepolymer or unsaturated monomer to form a monomer base. group. Polymerization of these monomer groups occurs to form a polymer, and the curing process of the coating oil is completed. If the varnish coating is too thick, the curing time is relatively long under the irradiation of the same power source. On the one hand, it affects the curing of the UV varnish, on the other hand, it also reduces the moisture content of the paper, making the paper brittle and brittle. Affects the folding resistance of the UV light oil layer.
5. Varnish coating roll inspection
When the UV light oil layer appears wavy, poor leveling, etc., it is generally because the coating roller is damaged or the viscosity of the coating oil is high. Replace the coating roller or change the anilox roller with a low number of screen lines to reduce the gloss. Oil viscosity.
6. Speed ​​control
During UV polishing, the machine speed should not be too high, because the UV lamp is aging during use, and high speed will affect the degree of UV curing.
7. Temperature control
The normal use temperature of UV varnish is 50-55°C. When it is used in winter, the UV varnish must be heated with constant temperature water, or the UV varnish must be placed in a constant temperature room before use, and the varnish should be used at room temperature before use. In order to make its viscosity reach the designed viscosity, it is beneficial to the leveling and rapid curing of UV varnish.
Source: Print Technology 2005/9
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