Overview of ordinary waterless offset printing inks
the composition of waterless offset printing inks is similar to that of general offset printing inks, which are composed of pigments, resin binders, solvents and thinners, additives and additives
the pigment used in waterless offset printing inks is similar to that of ordinary offset printing inks. Except for carbon black pigments, organic pigments plus yellow pigments are used in Tsuen Ben, including benzidine yellow (py-12, py-13, py-14, py-83, etc.), red pigments include lisol red (pr-49:1), 6B magenta, and 50 of them are marked with ecological labels (pr57:1), golden red C (pr-53:1), 2b YONGGU red ((pr-48:1), and blue pigments are phthalein blue (pb-15:1), The green pigment is phthalein, etc. Pigment, accounting for 15-25% of the total ink
2, the main resin used in resin binder
is similar to ordinary offset printing inks in general categories. The commonly used resins for waterless offset printing inks are phenolic resin modified by rosin Colloidal rosin modified phenolic resin and inebriated resin modified with vegetable oil such as linseed oil are the main body, but because there is no evaporation of fountain solution to cool the ink in the process of anhydrous offset printing, the printing process is relatively sensitive to temperature (this has been improved by mechanical devices), so there are special rheological properties requirements for the resins that make up the ink. In particular, the impact on the drill elasticity of resin binder should be paid more attention. Generally, the drill elasticity is higher than that of ordinary offset printing ink, but the properties in it are slightly softer. These two are contradictory, but trying to find a suitable balance range is the focus of ink formula. In addition, the resin binder should have appropriate high cohesive materials, so as to promote the complete and clean stripping and transfer of ink from the printing plate and blanket
there is a complex relationship between the drill elasticity of resin components and the size of their molecular weight, cross-linking and the characteristics of branched chain chemical process equipment. Generally, resins with a molecular weight of 20 million and 400000 can be selected. Higher molecular weight and greater degree of branched chain and literary Union will show higher drill elasticity, but the solubility in plant oil and mineral oil will be reduced. Therefore, great attention should be paid to the accommodation of the resin in the solvent
the commonly used phenolic resins modified by Rosin include bisphenol A, tert butylphenol, octenol, nonylphenol, dodecyl phenol, etc., as well as rosin vinegar resin modified by maleic acid.
in recent years, American Sun Chemical Company and gonglinte ink company have successfully developed water washable and anhydrous offset printing inks. At present, they have entered the stage of industrial test and trial, and they do not have the type of resin they use, However, it can be inferred from the principle of water washable ink that after saponification, the ink can be cleaned from the plate or printing machine. The drive and control system of the stripping tester is introduced. Of course, the introduction of this component can make the printing factory not necessarily use organic solvent cleaning agents, but the alkali resistance grade of the print will certainly decline
ultraviolet (UV) and electron beam (EB) The solidified anhydrous offset printing oil is also under research and development. Cyclic acrylic acid vinegar, polysilacryl acid vinegar and Azotobacter acrylic acid can all be used as the main polymer of binder
3, solvents and thinners
in the printing process of anhydrous offset printing ink, clearly and completely stripping the ink from the image part of the printing plate is one of the key factors to obtain high-quality prints. Over the years, the industry has gradually reached a consensus on the stripping mechanism, and the theory of "interface diffusion boundary layer" has been accepted by many researchers. According to this theory, the solvent in the ink diffuses to the layout to form a very thin liquid film layer, so the adsorption force of the rubber on the ink is much smaller than the cohesion of the ink, which is conducive to the complete stripping of the printing plate by the ink layer and then transferred to the blanket and paper. According to this theory, the choice of solvent in ink is very important, and it will contain many components (including additives). Earlier patents have reported this, such as adding liquid organic polysiloxane to ink solvent. Some patents also reported that adding non-ionic surfactants with HLB value (such as ether of polyoxyethylene camphor or propylene camphor, diethylcamphor II new hydrogel materials with wide application prospects, glycine monoethyl hexyl ether, etc.) would be very effective. Recent studies also proposed that using vegetable oil derivatives such as rapeseed oil vinegar, oleic acid vinegar, etc. as cosolvents, the drillability of ink could be reduced. The drillability value and elasticity value increase
in addition to these functional solvents, mineral oil, soybean oil, flax oil and other vegetable oils commonly used in offset printing inks are still important diluents
4, the varieties of slope materials and additives are similar to those of conventional offset printing inks, and calcium carbonate, calcium barium white, barium sulfate, etc. are still among the choices. Additives include wax wear-resistant additives, with the dosage of 0,5% to 2,0 "/q naphthenic acid diamond, manganese naphthenic acid and other desiccants (added in the formula when necessary) The dosage is 1% to 3% of other additives with special functions
offset lithography is a relatively complex printing method. It eliminates the fountain solution, improves the quality of printed matter, improves production efficiency, and is more environmentally friendly. However, the development of special anhydrous offset printing inks to match the surface characteristics of new plates, and smoothly realizes the transmission, stripping and transfer of inks. There is still a lot of ink formulation work to be done, which requires us to continue to explore this new field that is gradually developing.
reprinted from: Chenyi printing