Classification and necessary conditions of ink for plastic screen printing

(1) Classification by substrate

According to the substrate chemical name can be divided into: polyethylene, polypropylene (non-polar) ink. PVC, polystyrene, ABS polycarbonate (polar) ink. According to the form of substrate can be divided into soft plastic ink and hard plastic ink.

(2) Classification by drying method

There are volatile drying ink, UV curing ink, oxidation drying ink.

① Volatile dry ink: it is a kind of ink used in screen printing. The composition of ink film is mainly high polymer material. After printing, the solvent volatilizes, and the polymer material forms ink film. This evaporation drying process is reversible, that is, the drying ink film can be redissolved with solvent.

Ink transfer to substrate, there will be solvent ink film, the first solvent evaporation. The solvent in the ink diffuses in the atmosphere due to the effect of vapor pressure, forms a liquid film on the surface of the ink film, and then volatilizes through the liquid film. In this drying process, the internal drying is generally slow, and sometimes the air blowing is needed to accelerate the drying process.

Volatile ink, easy to use, drying generally faster, is widely used.

② UV curable ink (UV ink): UV ink can produce photochemical reaction. It can be completely cured in a few seconds. It is used more and more in plastic printing. The main components of the ink are photopolymer resin, initiator, pigment and additives, in principle will not use organic solvents.

③ Oxidation drying ink: ink contains small molecular weight polymer, oxidized in the air, through the chemical reaction of heat, light or reactive substances to form a polymer film. After printing to the substrate surface, the ink generally needs to be heated to promote hardening.

2. The necessary conditions for plastic screen printing ink

① The ink should not dry conjunctiva on the plate, and when printing to the substrate surface requirements can be fast fixed drying, and has a good adhesion fastness.

② The ink should be loose, short, thin and slippery to ensure that the ink is easy to spread evenly on the plate. Under the condition of small force, it is easy to cross the net. The printing is required to be clear, no sticky dirt.

③ When the ink is coated on the plate, the viscosity, viscosity and consistency of the ink should be stable to ensure the consistency of printing quality and the smooth progress of printing.

④ After printing, the ink on the plate should be easy to clean to ensure that the plate can be reused.

⑤ To ensure that the print has a certain color density. For color patterns, to ensure that it has a normal tone.

3. Main components of plastic screen printing ink

(1) Pigment

It includes pigments and dyes. Pigment in addition to the role of color in ink, but also make the ink with covering power. In addition, the light resistance, heat resistance, solvent resistance and drug resistance of the ink are also affected.

(2) Linking material

Binder is the fluid component of ink. It plays a linking role, so that pigments, fillers and other solid substances are dispersed in it, printing is conducive to the uniform transfer of ink. It's another important role is to make the ink dry, fixed and film-forming on the substrate surface.

In general, different types of ink are the key factors in the selection of binder. The binder includes resin, grease, solvent, etc.

(3) Auxiliaries

Auxiliaries are various auxiliary agents added to improve the printability of ink, mainly including defoamer, diluent, plasticizer, UV absorber, drying regulator, etc. When printing, it usually only needs to be added.

Related links: flash dryer, spray drying equipment, vibratory fluidized bed, drum scraper dryer, disc dryer, hollow pulp dryer, hot stove, rotary kiln belt dryer.