Flexo Printing 1000 Questions (283-294)

283. How to solve the gel phenomenon of UV varnish?
Failure of UV Varnish to store in the dark, storage for too long, or high storage temperatures can cause gelation. Therefore, UV varnish should be strictly stored in the dark, storage temperature is 5 ~ 25 °C is appropriate, and the storage period should not be too long.

284. How to solve the white point and pinhole phenomenon of UV coating?
Coatings that are too thin, too high anilox roller lines, too much non-reactive diluent, and dust on the print surface can cause white spots and pinholes in UV coatings. In this case, it is possible to increase the coating thickness, add a small amount of leveling agent, use reactive monomers that participate in the reaction when diluting, and keep the production environment and printed surface clean.

285. How to solve uneven UV coating, striped and orange peel phenomenon?
UV coating oil viscosity is too high, poor leveling, drying temperature and lack of hot air, etc. will lead to the above phenomenon. In the realization of production, the viscosity of UV coating can be reduced, the coating amount can be reduced or a small amount of leveling agent can be added.

286. What are the testing indexes for flexographic UV inks?
(1) Color: Approximate standard.
(2) Fineness: 10 to 15 μm.
(3) Viscosity: 200 to 2000CP (25°C).
(4) Viscosity: 2 to 4 minutes (25°C).
(5) Curing speed: 1 to 3 seconds.

287 how to detect the flexographic UV ink viscosity?
Since the flexographic UV ink has a slightly higher viscosity than the flexographic water-based ink, and has a relatively wide range, it is commonly used to measure the viscosity of the Milia viscometer and is expressed in centipoise (CP). The test method is referenced to the lithographic ink viscosity test method QB574.83.

288 how to detect the flexographic UV ink curing speed?
(1) No stickiness. When the ink film is in contact with other surfaces, there is no feeling of stickiness or ink transfer.
(2) Thumb turbulence inviscid. With the thumb rotating on the ink film, the ink film does not break.
(3) No scratches. The ink film was nailed with the nail and the ink film did not break, indicating that the UV ink had completely cured.

289. What should I pay attention to when storing flexographic UV inks?
Since flexographic UV inks are sensitive to light and heat, excessive amounts of light and heat will degrade them. Therefore, such inks should be stored under conditions of low temperature, ventilation, and light protection. The shelf life of the flexographic UV ink is generally 6 months, and the storage temperature is preferably 16 to 25°C. Since the flexographic UV ink is relatively stable and exceeds the storage period, it can be used normally if it is not cross-linked, but it is better to use it out during the storage period.

290. What are the safety hazards in the use of flexographic UV inks? How to protect?
Flexographic UV inks, like other chemicals, can also pose a certain hazard to human health and safety. However, such hazards are not as serious as ordinary chemicals and will be ignored in most cases. At present, there are mainly three problems in the use of flexographic UV inks, and certain protective measures must be taken.
(1) The hazards to the human body of flexographic UV inks. Acrylates in flexo UV inks are skin irritants. Prolonged exposure to the skin can cause allergic reactions, itching, redness, etc. Wear protective glasses and wear protective clothing to minimize flexographic UV inks. The chance to contact the skin. If you accidentally come into contact with the flexo UV ink, wash it with soap and water as soon as possible.
(2) The safety of UV light sources. Flexographic UV inks must be cured with ultraviolet light, but ultraviolet light can cause some damage to human skin and eyes. As long as the operator does not face the UV light directly, there is no need to worry about being exposed to ultraviolet radiation. In order to prevent UV leakage, users can also purchase special instruments to detect the degree of UV leakage.
(3) The flexographic UV ink will generate ozone (O3) during the curing process. Therefore, ventilation should be strengthened, and the ozone should be discharged through the pipeline to maintain a good operating environment.

291. What are the reasons why waterborne gloss is poor and brightness is not enough? How to solve?
The main reasons are as follows.
(1) The paper is too thick and the penetration is too strong.
(2) The amount of waterborne coating is too small.
(3) Water-based polish oil is too thin and its solid content is insufficient.
(4) The quality of waterborne coating is poor.
Solution: Increase the viscosity and coating amount of water-based varnishes; primers must be pre-coated when the paper is too thick.

292. What are the reasons for poor water-based glazing and surface tackiness? How to solve?
The main reasons are as follows.
(1) The water-based coating is too thick.
(2) The viscosity of waterborne coating is too high.
(3) The drying tunnel temperature is too low and the hot air is insufficient.
(4) The pH of the aqueous coating is too high.
Solution: Adjust the viscosity and pH of the water-based coating oil; reduce the coating amount; and increase the drying capacity of the drying system.

293. What are the reasons for the uneven waterborne coating, striped or orange peel? How to solve?
The main reasons are as follows.
(1) The viscosity of waterborne varnish is too high.
(2) The amount of water-based coating is too large.
(3) Pressure adjustment is not suitable.
(4) The leveling property of waterborne coating is poor.
(5) Water-based coating oil dries too quickly.
Solution: Reduce the viscosity of the water-based coating; reduce the amount of coating; add appropriate amount of slow drying agent or a small amount of leveling agent.

294. What are the reasons for the large number of air bubbles in the waterborne glazing process? How to solve?
The main reasons are as follows.
(1) The viscosity of waterborne varnish is high.
(2) The waterborne coating has a low pH.
(3) Excessive circulation stirring.
(4) The glazing speed is too fast.
Solution: properly reduce the viscosity of water-based coating oil; adjust the pH of the aqueous coating oil to keep it at about 9; if necessary, add an appropriate amount of defoamer, but the amount can not exceed 1%.

From - <Printing Technology>

Acetate Sunglasses

Acetate Sunglasses,Italian Designer Sunglasses,Polar Eagle Polarized Sunglasses,Polar One Sunglasses

Fashion Sunglasses Co., Ltd. , http://www.cnsunglasse.com

Posted on