Plastic film printing

Plastic film as a printing material, its history is still relatively short, after printing it as a package, with a light and transparent, moisture resistant oxygen, good air tightness, toughness, folding, smooth surface, can protect the goods, and can reproduce the goods The shape, color and other advantages. With the development of the petrochemical industry, there are more and more types of plastic films. Commonly used plastic films include polyethylene (PE), polyvinyl chloride (PVC), polystyrene, polyester film (PET), and polypropylene (PP). , nylon and so on.

The performance of various plastic films is different, the degree of difficulty in printing is also different, and the use as a packaging material is also different.

Polyethylene film is a colorless, odorless, odorless, translucent non-toxic insulating material, used in a large number of bags; food bags, but also a variety of containers. It is an inert material, so it is more difficult to print and must be processed to produce better results.

The polyvinyl chloride film has good light resistance and aging resistance, good tear resistance, breathability, and is a clean, colorless, transparent film. It is generally added with a plasticizer, and it is soluble in acetone. Cyclohexanone and other solvents. Therefore, it can be printed with a polyvinyl chloride resin ink. Suitable for bags, book covers, etc.

Polystyrene film is a soft and tough film, clean, colorless and transparent, without plasticizer, the film is always soft, resistant to freezing, storage is not aging, the use of oxidative polymerization of synthetic binder ink, can be printed The imprinting fastness is better.

Polyester film is a colorless, transparent, moisture-resistant, airtight, soft, high strength, acid and alkali resistant oil esters and solvents, is not afraid of high and low temperature materials, after the EDM treatment, has a better surface fastness to the ink . For packaging and composite materials.

Polypropylene film has good luster and good transparency, heat-resistant acid and alkali, solvent resistance, friction resistance, tear resistance, and air permeability. It can not be heat-sealed below 160°C.

Nylon film is stronger than polyethylene film, odorless, non-toxic, impervious to bacteria, oil, ester, boiling water and most of the solvent, generally used for load, wear-resistant packaging, and cooking packaging (reheat of food) It can be printed without surface treatment.

Polyethylene is basically free of polar groups and is a non-polar high molecular weight. In polypropylene, each structural unit contains a methyl group, which is divided into weak polar groups. Also belong to non-polar macromolecules, so their affinity for the ink is relatively poor, so before printing can be processed before printing to get a satisfactory print.

Most of the treatment methods are through oxidation, making it more polar, so that the surface structure changes. Specific treatment methods are discharge (commonly known as corona, EDM), flame, ultraviolet radiation, acid (sulfuric acid, chromic acid) treatment and several other. The discharge method is relatively simple and popular.

The effect of the corona treatment is related to the output power of the processing equipment, the distance between the two electrodes, the discharge area of ​​the electrode, the processing speed, and the treatment method (heat treatment or cold treatment) and the number of times, and the treated film. It must be printed immediately or it may still fail.

In EDM treatment, the polymer may crosslink due to the radical reaction generated by the corona discharge, and the surface becomes rough and increases its wettability with polar solvents. In general, the plastic film is rarely processed. Printing can be improved by thirty aspects (Performance: antistatic additives can be used (China's use of trihydroxy dodecanoyl ethyl quaternary ammonium perchlorate, in order to improve the reduction of static charge strong ink adhesion effect of thick gravure In the case of chiral printing, the wettability of solvent inks has been improved.

Plastic film printing methods can be flexo, gravure and screen printing. Printing inks are required to have high viscosity and strong adhesion, which can make the ink molecules firmly adhere to the surface of dry plastics. Shangtuo is very easy to be contaminated with oxygen in the air and dry. In general, the gravure used for gravure plastic film is composed of synthetic resin such as phenylamine, organic alcohol-based solvents and pigments, which have been thoroughly ground and dispersed to form a gel fluid with good fluidity. It is a volatile drying ink. , With good printing performance, with strong fastness, bright color, rapid drying and other characteristics, suitable for printing with gravure web printing machine in the aggregation of ethylene, ene film.