Ink classification
Feb 03, 2023
Overview
Ink is an important material used for packaging material printing. It displays the patterns and characters on the substrate through printing. The ink includes the main components and auxiliary components. They are evenly mixed and rolled repeatedly to form a viscous colloidal fluid. It is composed of pigments, binders, additives and solvents. It is used for printing books and periodicals, packaging and decoration, building decoration, etc. With the increase of social demand, the variety and output of ink have also expanded and increased accordingly.
Ink classification
1. Inks are mainly divided into four categories according to type:
(1) Letterpress ink
A type of ink used for printing books, periodicals, newspapers, picture albums, receipts, account books, etc. The main feature of letterpress printing is that the inked part of the printing plate protrudes from the non-inked part. The letterpress ink can be divided into lead printing ink, copperplate ink, letterpress rotary ink and flexible letterpress ink according to the type of printing machine and the purpose of printing products.
(2) Lithographic ink
A type of ink suitable for lithography. Each part of the layout of lithographic printing is basically on the same plane. The pattern is hydrophilic and the non-pattern is hydrophilic. The lithographic ink must have water resistance because it uses the principle of mutual exclusion between oil and water. It can be divided into offset printing ink, web offset printing ink, flat offset printing ink, anhydrous offset printing ink, iron printing ink, stone printing ink, and collodion? Edition ink.
(3) Gravure ink
A type of ink suitable for intaglio printing. When printing, ink is applied to the image part recessed in the layout, and the ink on the non-image part is wiped or scraped, and then printing is carried out. There are engraving gravure ink and photographic gravure ink.
(4) Mesh printing ink
A type of ink that is leaked to the printing surface through the mesh of the printing plate for printing. Mesh printing ink is divided into transcription printing ink and screen printing ink.
The ink manufacturing process can be divided into two stages: stirring pre-dispersion and grinding fine dispersion. The former mixes the prepared pigment and binder in the container to form a paste; The latter still needs to be grinded and finely dispersed in the stirred slurry to overcome the cohesion of the pigment with greater mechanical pressure and shear force, and finally become a suspended colloidal ink.
2. Classification of environment-friendly ink:
At present, according to the actual use requirements, environmental protection requirements are put forward for the ink. First of all, the composition of the ink should be changed, that is, using environment-friendly materials to prepare new ink. There are mainly water-based ink, UV ink, water-based UV ink and some alcohol-soluble ink.
(1) Water-based ink
The biggest difference between water-based ink and solvent-based ink is that the solvent used is water rather than organic solvent, which can significantly reduce VOC emissions, prevent air pollution, do not affect human health, is not easy to burn, has stable ink property, bright color, does not corrode the plate, is simple to operate, cheap, has good adhesion after printing, strong water resistance, and rapid drying, so it is especially suitable for food, beverage, medicine and other packaging printing materials, It is recognized as an environmentally friendly printing material in the world, and is the only ink recognized by the American Food and Drug Association among all printing inks at present.
(2) UV-curable ink
Ultraviolet curable (UV) ink refers to the ink that is filmed and dried by ultraviolet light of different wavelengths and energies under ultraviolet radiation. Different UV spectra can produce different energies to polymerize the monomers in different ink binders into polymers, so the color film of UV ink has good mechanical and chemical properties. The main advantages of UV ink are: (1) no solvent; (2) Fast drying speed and low energy consumption; (3) Good gloss and bright color; (4) Water resistance, solvent resistance and good wear resistance. The photoinitiator in UV ink is a compound that is easily excited by light. After absorbing light, it is excited to form free radicals, and the energy is transferred to photosensitive molecules or photocrosslinking agents to make UV ink undergo photocuring reaction. At present, UV ink has become a relatively mature ink technology, and its pollutant emission is almost zero. In addition to solvent-free, UV ink has the advantages of not easy to paste, clear dot, bright color, excellent chemical resistance and low consumption.
(3) Waterborne UV ink
Water-based UV ink is a new research direction in the field of UV ink. The viscosity of prepolymer in ordinary UV ink is generally large, and it needs to be diluted with active diluent. However, the diluent acrylate compounds currently used have different degree of skin irritation and toxicity. Therefore, while developing low viscosity prepolymer and low toxicity active diluent, another development direction is to study water-based UV ink, that is, water and ethanol are used as diluents. At present, water-based UV ink has been successfully developed and applied in some printing.
In addition, alcohol-soluble ink, which mainly plays a role in flexographic printing, is also a kind of ink with very little pollution, mainly used in food, medicine, beverage, tobacco and alcohol, and packaging and printing of daily necessities in contact with human body.
3. Introduction to main equipment and functions
The ink processing system is mainly composed of raw material storage system, metering and transportation system, dispersion system, grinding system, mixing system, filtering and packaging system and control system. It can be small-scale stand-alone production, or large-scale production with ink production equipment.
The production equipment mainly includes high-speed disperser, basket grinder/horizontal grinder, low-speed mixer, filter, filling machine, etc.
