a. Different film formation mechanism of water-based ink
The composition of the water-based ink is: water-soluble resins, pigments, various additives and water. Water-soluble resin as a key component of water-based inks - film-forming substances must be used directly in the form of an aqueous solution in their production process, so the water-soluble resin water solubility is an extremely important performance, its molecular weight will not be too Large, or water-soluble, therefore, as a polymer material used mostly made of thermosetting. In the heat curing process, an insoluble and infusible network structure is formed by the cross-linking reaction between the reactive groups in the resin system or the active groups of the cross-linking agent, thereby providing excellent ink film properties.
In order to increase the water solubility of the water-soluble resin, the water-soluble resin is present in the form of carboxylate or amine salt. Therefore, in the film curing process, ammonia or amine volatilizes first. Of course, in the heating process, an amine derivative is formed and an ammonia-zirconium ion complex is used as a cross-linking agent for the carboxylic acid-type polymer. When the water and ammonia in the resin are volatilized at room temperature, the acidic polymer and zirconium become acidic. Ions can be cross-linked to form ions and can be dried at room temperature.
However, due to the large latent heat of evaporation of water, the drying rate is slowed down, and at the same time, the ammonium salt is decomposed due to unstable heat, so it is mainly volatile and dry, and it is reactive and solidified and dried. Once the ink film is dried, it becomes water-insoluble. Now. The drying process is as follows: RCO-NHCH2CH2OH---RCO-OH+H2NCH2CH2OH b. The surface tension of water-based ink and oil-based ink is different
Compared with oil-based ink, the surface tension of the ink is much higher, and too high surface tension will cause the ink to not wet the surface of the substrate material. This will cause the ink film to be uneven, due to the large surface tension of the ink. The ink film will form a contracted state on the surface of the substrate, causing the ink film to show a clear mesh shape, which will also cause the ink to be unable to be uniformly transferred from the inked ground to the surface of the substrate.
However, the surface tension can be reduced, which requires careful selection of the appropriate surfactant or a small amount of alcohol. The other is that the surface tension of the ink is matched with the surface of the substrate. After the surface treatment (anion, non-ion), the surface tension and polarity of the water can be improved, and the toner is dispersed in the water. The water-based resin is an ink. The heart, which determines the adhesion to the substrate, is ideal for a surface area of ​​44 dyne.
c. Different printing dot reproduction curves
The printing dot reproduction curve reflects the range of the tone that the printing can reproduce. The number of engraving lines for electric engraving is generally 40 to 120 lines/in, and the screen angle is 30° to 60°. Before adjusting the level curve of the electric carving, the basic data such as network lines, screen angles, network point percentages, and cell width must be determined first. The development of these data should take into account the types of substrates, the effects of prints, the transfer of ink, water lines, and moiré.
In the process of printing and copying, there will be different degrees of error in the transfer of outlets. The dot reproducibility of water-based ink is good, water-based ink can reach 70~80, and solvent ink can only reach 50.
Water-based inks are slower to dry and less viscous than oil-based inks. Therefore, the ink in the cells is hardly dry. The viscosity of the ink does not increase from the time after the scraping of the blade to the transfer, and the transfer of high-profile parts is extremely good.
d. There are different reasons for ink fog
Because the surface tension of the water-based ink is too large, a fog plate is easily generated at high-speed printing. The main reason for producing ink fog version:
1) The evaporation speed of the water-based ink is slow, and the ink film attached to the surface of the gravure cylinder is easy to transfer to the paper;
2) Water-based ink is easy to affect the surface of the paper, so that paper powder and other mixed in the ink, the blade resistance is easy to become large;
3) When the re-solubility of the ink is poor, the ink dried on the plate will increase the resistance of the blade.
Solve from the following aspects:
1) The version has to improve the grinding accuracy of the version;
2) to improve the ink flow, low viscosity printing, reduce the impact of the ink on the blade, so that the blade can be very clean scraping blank part of the ink;
3) In the formulation, an organic pigment (such as ultra-fine powder, ultra-fine barium sulfate, etc.) is filled in the resin that encapsulates the pigment, which further enhances the body of the ink, reduces the viscosity of the ink under the same printing viscosity, and improves the scraping of the blade. Ink performance
4) Wax powder and matte powder are effective auxiliaries to reduce the problem of fog plate. The particles are easily detached on the surface of the ink and enhance the squeegee performance of the squeegee. After the fineness of the ink grinds is passed, high-speed dispersion is added and grinding is not performed, which will reduce the effect of solving the fog plate problem;
5) Wetting and dispersing aids are added to the formula to solve the problem that the pigments are not well wrapped by various synthetic resins and the stability of the system itself is poor, otherwise fog problems will occur.
The composition of the water-based ink is: water-soluble resins, pigments, various additives and water. Water-soluble resin as a key component of water-based inks - film-forming substances must be used directly in the form of an aqueous solution in their production process, so the water-soluble resin water solubility is an extremely important performance, its molecular weight will not be too Large, or water-soluble, therefore, as a polymer material used mostly made of thermosetting. In the heat curing process, an insoluble and infusible network structure is formed by the cross-linking reaction between the reactive groups in the resin system or the active groups of the cross-linking agent, thereby providing excellent ink film properties.
In order to increase the water solubility of the water-soluble resin, the water-soluble resin is present in the form of carboxylate or amine salt. Therefore, in the film curing process, ammonia or amine volatilizes first. Of course, in the heating process, an amine derivative is formed and an ammonia-zirconium ion complex is used as a cross-linking agent for the carboxylic acid-type polymer. When the water and ammonia in the resin are volatilized at room temperature, the acidic polymer and zirconium become acidic. Ions can be cross-linked to form ions and can be dried at room temperature.
However, due to the large latent heat of evaporation of water, the drying rate is slowed down, and at the same time, the ammonium salt is decomposed due to unstable heat, so it is mainly volatile and dry, and it is reactive and solidified and dried. Once the ink film is dried, it becomes water-insoluble. Now. The drying process is as follows: RCO-NHCH2CH2OH---RCO-OH+H2NCH2CH2OH b. The surface tension of water-based ink and oil-based ink is different
Compared with oil-based ink, the surface tension of the ink is much higher, and too high surface tension will cause the ink to not wet the surface of the substrate material. This will cause the ink film to be uneven, due to the large surface tension of the ink. The ink film will form a contracted state on the surface of the substrate, causing the ink film to show a clear mesh shape, which will also cause the ink to be unable to be uniformly transferred from the inked ground to the surface of the substrate.
However, the surface tension can be reduced, which requires careful selection of the appropriate surfactant or a small amount of alcohol. The other is that the surface tension of the ink is matched with the surface of the substrate. After the surface treatment (anion, non-ion), the surface tension and polarity of the water can be improved, and the toner is dispersed in the water. The water-based resin is an ink. The heart, which determines the adhesion to the substrate, is ideal for a surface area of ​​44 dyne.
c. Different printing dot reproduction curves
The printing dot reproduction curve reflects the range of the tone that the printing can reproduce. The number of engraving lines for electric engraving is generally 40 to 120 lines/in, and the screen angle is 30° to 60°. Before adjusting the level curve of the electric carving, the basic data such as network lines, screen angles, network point percentages, and cell width must be determined first. The development of these data should take into account the types of substrates, the effects of prints, the transfer of ink, water lines, and moiré.
In the process of printing and copying, there will be different degrees of error in the transfer of outlets. The dot reproducibility of water-based ink is good, water-based ink can reach 70~80, and solvent ink can only reach 50.
Water-based inks are slower to dry and less viscous than oil-based inks. Therefore, the ink in the cells is hardly dry. The viscosity of the ink does not increase from the time after the scraping of the blade to the transfer, and the transfer of high-profile parts is extremely good.
d. There are different reasons for ink fog
Because the surface tension of the water-based ink is too large, a fog plate is easily generated at high-speed printing. The main reason for producing ink fog version:
1) The evaporation speed of the water-based ink is slow, and the ink film attached to the surface of the gravure cylinder is easy to transfer to the paper;
2) Water-based ink is easy to affect the surface of the paper, so that paper powder and other mixed in the ink, the blade resistance is easy to become large;
3) When the re-solubility of the ink is poor, the ink dried on the plate will increase the resistance of the blade.
Solve from the following aspects:
1) The version has to improve the grinding accuracy of the version;
2) to improve the ink flow, low viscosity printing, reduce the impact of the ink on the blade, so that the blade can be very clean scraping blank part of the ink;
3) In the formulation, an organic pigment (such as ultra-fine powder, ultra-fine barium sulfate, etc.) is filled in the resin that encapsulates the pigment, which further enhances the body of the ink, reduces the viscosity of the ink under the same printing viscosity, and improves the scraping of the blade. Ink performance
4) Wax powder and matte powder are effective auxiliaries to reduce the problem of fog plate. The particles are easily detached on the surface of the ink and enhance the squeegee performance of the squeegee. After the fineness of the ink grinds is passed, high-speed dispersion is added and grinding is not performed, which will reduce the effect of solving the fog plate problem;
5) Wetting and dispersing aids are added to the formula to solve the problem that the pigments are not well wrapped by various synthetic resins and the stability of the system itself is poor, otherwise fog problems will occur.
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