Influence of the hottest printing method on ink ch

The influence of printing methods on ink characteristics and flotation deinking II

1.2.3 photocopying and laser printing inks

photocopying and laser printing inks (i.e. colorants, or pigments) are dry black powders with densities of 1.21g/cm3 and 1.48g/cm3 respectively, and the average particle sizes are about 15 respectively μ M and 25 μ m。 The chemical composition is similar. Styrene acrylate copolymer is used as its connecting agent, and the mass fraction is 60% - 90%. The main difference between them is that laser printing colorants contain ω= 35% iron oxide is used as pigment, while Photocopying colorant contains ω= 12% carbon black is used as pigment. See Table 2 for details

because carbon black and iron oxide will not decompose during pyrolysis, the pyrolysis curves of photocopying and laser printing inks are very similar. There is a single decomposition peak between 350 ℃ and 460 ℃, and the mass spectrum analysis of their decomposition products is considered to be the same, which are all styrene α Monomethyl styrene, toluene, methyl acrylate, benzene, acrolein, dimer and trimer of styrene and acrylate. The printing coloring agent has about after decomposition ω= 20% residue. The decomposition temperature of photoprinting and laser printing colorants is lower than that of pure polystyrene and pure polyethylene ester, which may be due to the presence of pigments and metal additives in the colorants

although there are many kinds of inks, it has been found that the main product of ink decomposition is non-polar compounds, such as hydrocarbons. Therefore, these inks are originally hydrophobic, that is, for water, they have a large contact angle (80 °), as shown in Table 3. The larger the contact angle is, the greater the hydrophobicity is, and the more conducive it is to be floated out of the fiber suspension

these hydrophobic inks are easy to separate from hydrophilic cellulose fibers during flotation

2. Influence of printing method on ink characteristics and flotation deinking

the basic requirement for printing ink is to meet the needs of printing method. For different printing methods, the contact path between ink and fiber is different, and the physical and chemical properties of ink are changed differently. These changes in ink characteristics directly affect the efficiency of flotation deinking

according to the ink solidification mechanism, printing methods can be divided into two categories

the first type is the printing method of ink adhesion through absorption and evaporation. In this case, the ink adapts to different printing needs with different viscosity

lithographic printing method is based on the principle that oil and water cannot be mixed. The image area on the printing plate is made into acceptable oil-based ink rather than water. Lithographic printing ink is often called offset oil-based ink, which is based on the fact that water-resistant color carrier (binder) and pigment cannot flow out in water or ethanol. This method can be used in printing paper, glossy magazines, books and photography, and can provide the measured data to relevant personnel for reference and analysis of products. In this method, the offset cold solid oil-based ink is simply absorbed by the pores of the paper at room temperature without worrying about the prosthetic limb falling off, and the pigment then stays on the surface of the paper without drying. This is that the liquid component of the ink penetrates into the paper, leaving the solid component on the paper. Even if the adhesion is carried out under drying or chemical reaction, it still has absorption effect. Therefore, there is no obvious change in the properties of offset cold set oil-based ink during the printing process

letterpress printing and its improved printing. Aniline letterpress printing is this kind of printing method. Its ink is used for the protruding surface on the printing plate. When the printing plate is pressed on the paper, the ink on the protruding surface of the printing plate is transferred to the paper. Letterpress printing inks have medium or low viscosity and fast drying performance. Oil-based and water-based inks are commonly used. This method is a typical method of printing newspapers and magazines

rotogravure printing uses the recessed area of the printing plate to form an image, and the ink fills the recessed area. The paper is pressed to the recessed area by the elastic rubber roller to contact the ink. Rotogravure printing is typically used to print color newspapers and magazines

in letterpress and gravure printing, water-based ink and oil-based offset thermosetting ink are dried by evaporating volatile solvents (such as water or low boiling organic solvents, such as aromatic hydrocarbons or esters) at 60 ℃, and resins and other materials are combined with pigments and left on paper. Since there is no chemical reaction during printing, the oil-based offset thermosetting ink and the dried water-based ink maintain their original hydrophobic properties after printing

the second important printing method is indirect printing. Printing requires relatively high temperature to make the ink adhere to the fiber. When fine powdery solid ink is used, these printing cylinders will completely fall behind. The methods are photocopying and laser printing. (to be continued)