Pre-printing of polyethylene bottles
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Printing polyethylene, polystyrene plastic surfaces with a pad printing machine, as well as screen printing, can be printed directly. However, corona and flame treatment must be carried out before printing. Otherwise, the printed image can be easily erased, the printing quality can not meet the requirements, and the quality of prepress processing must be controlled.
First, the surface treatment
1. High frequency discharge treatment method. High voltage (2 ~ 100kV), high frequency (2 ~ 20kHz) is applied to the electrode, corona discharge is generated between the two poles, a large amount of plasma gas and ozone are generated, directly or indirectly interacting with the surface molecules of the plastic bottle to make the plastic surface molecule The chain introduces a polar group to achieve the purpose of surface treatment.
2. Flame treatment method. The flame treatment machine is used to perform flame combustion treatment on the surface of the bottle to oxidize the surface and increase the surface tension. The specific practices are as follows: (1) The ratio of air to gas is between 5% and 15%, so that the gas is completely burned under the most economical use. (2) The distance between the flame tip and the surface of the bottle is 10-15 mm, that is, the outer flame with the highest heat of the flame is the best oxidation effect. (3) The correct contact time between the flame and the bottle can be determined by trial and error. Start the machine and process several samples. If there is no evidence of oxidation on the surface of the sample, or if it is not very hot, the contact time is too short. Conversely, if the bottle is deformed, it means that the time is too long and the contact time needs to be shortened.
Second, the identification of treatment effects
1. Submersible inspection method. Soak the treated bottle with water or rinse for more than 3 seconds, take out the observation and calculate the time that the continuous continuous water film remains on the surface of the bottle. For example, in 4 to 9 seconds, it indicates that it has hydrophilicity, lower than this number. , indicating that the oxidation treatment is not effective; if it is more than 12 seconds, the ink adheres well to the plastic surface. The most appropriate degree of treatment is that the water film remains until the water has completely evaporated.
2. Surface tension test method. Mixing ethylene glycol ether and formamide in a certain ratio to prepare a surface tension test solution of 40 dynes/cm, using a cotton swab to take the test liquid, and coating a certain area on the surface of the treated bottle, if the liquid film If it is kept for more than 2 seconds without breaking, it means that the processing requirement is reached; otherwise, it means that the surface tension of the bottle is not up to standard.
Conclusion
The digital plate making method was applied to the printing and printing, and the digital stencil printing machine was born, and the basic conditions for the production of the plate-making and printing machine were created. In the future, the digital stencil printing machine will attract attention as a high-speed printer that connects to the Internet. As a high-speed image output device for the information society, it is expected to further develop.
Based on the stencil technology of simple plate making, the digital stencil technology is developed according to the requirements of customers, making it a printing machine with clearer graphics, simpler operation, higher reliability, better environmental adaptability and cheaper. As safety production and environmental protection will be paid more and more attention, the low-energy (power saving) and ink-free (environmental) features of digital stencil printing machines that do not require high-temperature fixing are catering to modern trends and continue to enrich peripheral devices. New technologies will be developed in terms of expanding printable paper grades and improving operational performance.