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The drying process and mechanism of different types of inks are completely different. At present, common ink drying methods are classified into:
Physical drying a. Ordinary drying, including natural volatilization drying, osmotic drying, dusting fixed drying b. Aqueous polymerization drying chemical drying a. Heat drying, including combustion heating and drying, infrared drying, microwave drying b. Radiation drying, including UV drying, Electron beam drying c. Reaction drying, including drying of oxidized conjunctiva, drying rate of the two-liquid reactive drying ink is related to the drying mode of the ink, and the drying mode of the ink depends on the components of the ink connecting material. Most of the inks are often not single due to the bonding material, so the fixing drying of the ink is based on a certain dry form, and is accomplished with other drying forms.
Different printing methods, substrates, and printing machinery have different requirements for the fixation and drying of inks.
Second, the current commonly used ink drying method Introduction 1. Infiltration drying The infiltration drying method is mainly the drying method of some mineral oil solvents. The drying principle is mainly due to the absorption properties of the paper and curing, adhesion. The mineral oil solvent is easily absorbed by the absorbing paper, so that the pigment and resin left on the paper are quickly fixed, but they cannot form a tough film and the gloss is also poor. Therefore, this ink is only suitable for printing newspapers and general journals.
2. Oxidative conjunctival drying A method of drying the binder obtained by refining vegetable oils such as linseed oil is oxidative conjunctiva drying. This kind of connecting material is made by drying and oxidative polymerization of dried vegetable oil under heating. It is mainly used for laser engrave and electronic engraving gravure printing ink. It has a certain degree of dryness, and the conjunctiva layer is firm and wear-resistant.
3. Volatile Drying If the solvent in the binder evaporates during the drying process of the ink, the remaining resin and pigment form a solid film layer that is fixed on the surface of the substrate. Then, the drying of the ink depends on the volatilization of the solvent from the film layer. To complete, called volatile drying. Common volatile drying inks are petroleum-, cellulose-, vinyl chloride-, polyamide-, epoxy-, and other resins used as binders for inks. Therefore, volatile drying is physical drying. Solvent inks such as photogravure inks, flexographic inks, and plastic printing inks are volatile dry inks.
4. Two-liquid reactive drying The two-liquid reactive ink refers to the preparation of the main agent and the curing agent separately, and the ink used in the printing is mixed again. It is commonly used for the printing of printing materials that are difficult to adhere to volatile drying inks. Mostly used for metal surface coating, hardened resin products, glass and other printing.
Third, a number of new ink drying technology 1. Photopolymerization drying Photopolymerization drying can be divided into infrared radiation drying and ultraviolet radiation drying method.
The infrared radiation drying method was first applied to a web offset press. Ink ink film obtains energy under infrared irradiation, and the atoms or groups in the organic matter molecules vibrate, accelerating the progress of thermal polymerization reaction and achieving the purpose of accelerated drying. With this drying method, since the ink film itself does not absorb enough infrared energy to complete the polymerization, the entire drying process is accompanied by other drying methods to accelerate the drying of the ink film. The spectrum used in the infrared drying process can be divided into near-infrared, midline and far infrared. The advantages are: the ink is solidified and dried faster. Generally, the printed product that takes 2 hours at room temperature can be dried. It can be dried in just 15 minutes to 30 minutes under infrared irradiation, which improves the printability of the printed product and reduces the amount of spray. Powder or not dusting; can increase the gloss of printed products by 20%-30%, infrared irradiation makes the ink layer flash hardening, improve wear resistance; low investment in equipment, ink roller, blanket, cleaning fluid and other special requirements, Post-print scrappage can be recycled.
UV drying is the use of ultraviolet light to decompose light-sensitive material molecules into active groups (photopolymerization initiators). These groups contain a series of chain reactions due to the presence of unsaturated groups, and the reaction process takes only a few seconds. Or a few tenths of a second, so that it becomes the polymerization state of the transaction, which also achieves the purpose of solidification and drying.
2. Electron Beam Curing and Drying Electron beam curing ink is an ink that can rapidly change from a liquid to a solid state under the irradiation of a high-energy electron beam. Also known as EB ink, it is a new environmentally-friendly ink developed in recent years. The application of this ink for electron beam curing printing has been applied at home and abroad, and it has been applied in the food and beverage packaging industry.
The same material as the ultraviolet ink was used as the binder for the electron beam curing ink. Since the energy of the electron beam is much greater than that of the ultraviolet ray, there is no need to use a photoinitiator like the ultraviolet ray ink, and the molecular monomer can be directly polymerized by the irradiation of the electron ray to cause the macromolecularization reaction to be solidified. Electron beam curing inks enable users to produce high value-added products at a lower cost, with low energy consumption, high production speed, low operating costs, solvent-free, and environment-friendly, making EB ink a promising production method. .
Several new ink drying technologies (1)
First, the basic conditions of ink drying technology Ink drying process can be divided into two phases: the first phase of the ink from liquid to semi-solid, can no longer transfer, known as the "fixed" stage, with "initial dry"; In the second stage, the physical and chemical reactions of the binders in the semi-solid inks completely dry the conjunctiva and are represented by "dryness."