Pigments include dyes and pigments, the role of which is to make the ink color. Dyes dissolve in water, oil, or organic solvents, while pigments do not dissolve in them; pigments only stain the surface of the object, while dyes can stain the entire object. Therefore, pigments are often used in inks, and sometimes pigments and dyes are used in combination. Dyes are generally classified into reactive dyes, direct dyes, vat dyes, neutral dyes, basic dyes, cationic dyes, ice dyes, sulfur dyes, and food dyes. The role of the linking material is to act as a carrier for the color material. The pigments are evenly dispersed and kneaded together. In the printing, the color material is transferred from the printing plate to the printing material to form a dry ink film. The binders mainly include oils, organic solvents, resins and auxiliary materials. Mineral oil is mainly derived from different fractions of petroleum. Ink is commonly used in inks, high-boiling kerosene and mechanical oils. The organic solvent in the binder is used to dissolve film-forming substances such as resins, so its own dissolution performance, release properties, and volatilization properties are very important. The organic solvent in the binder contains aromatic hydrocarbons, alcohols, ketones, esters, and the like. Resin is the central material of the binder, and its performance directly affects the luster and firmness of the ink film, and also affects the printing process and printability. Resins commonly used in inks include rosin and its derivatives, asphalt, natural resins, modified alkyd resins, acrylic resins, polyamide resins, epoxy resins, polyurethane resins, rubber resins, celluloses and derivatives thereof. The auxiliary materials in the ink include wax and aluminum soap. Waxes can change the rheology, water resistance, and printing properties of the ink. There are many kinds of waxes, such as vegetable wax (Canadian wax), animal wax (insect wax, beeswax), mineral wax (paraffin, ground wax) and synthetic wax (polyethylene wax, polytetrafluoroethylene wax) and so on. Aluminium soap is a gelling agent for the binder. The thickening state occurs when the binder is slightly gelled. Therefore, the aluminum soap is also called a thickener. Its mechanism of action is to react with the reactive groups of the resin in the binder to form macromolecular groups or to form chelates. The network formed forms a dilute part of the binder and forms a gel state. To solve the problem of deinking, it is necessary to understand not only the composition of printing inks, but also the paper properties of different waste papers and the classification of inks. Common waste paper is generally uncoated paper and coated paper. Non-coated paper has light sizing paper and heavy sizing paper. There are two kinds of ink classification methods: First, according to the type of printing plate is divided into lithographic, letterpress, gravure, screen and other inks; Second, according to the ink dry form is divided into osmotic drying ink, photocatalytic drying ink, thermal drying curing ink , rare earth catalytic curing ink. According to the type of paper and ink drying, waste paper can be roughly divided into the following types. Non-coated paper (ink is dry or replaceable) Such waste paper is generally old books and old book paper. Although these papers are not coated, the degree of sizing is relatively high and the fiber absorbs ink poorly. During the printing process, the ink is absorbed on the paper, and the solvent is not immediately absorbed by the fibers, but is dried or cured on the surface of the paper on behalf of the resin. The resin has a chemical curing process. After the curing, the ink has a strong fixing force and the deinking is relatively difficult, but The resin can still be saponified, but requires a higher saponification temperature and a higher alkali concentration. The dissociated ink particles are relatively large, and the addition of a strong oxidant can help separate the fibers and the ink and increase the whiteness of the fiber. Once the resin carrier is saponified to release the reclaimed material, it can be removed by flotation and washing, and the deinking is generally complete without ink dots or ink dots. The deinking design can use high-concentration alkali saponification and high osmotic surface activity. The agent is stripped and hydrogen peroxide is added as a bleaching and stripping aid while a small amount of chelating agent is added to stabilize the hydrogen peroxide.
Source: China Paper Technology Network
Ink composition and paper and ink properties