Update:What are the applications of polyurethane resin in plastics?The liquid part of the ink composition is called the binder;...
What are the applications of polyurethane resin
The liquid part of the ink composition is called the binder; the solid content is the colorant (pigment or dye); and various auxiliaries. The binder is a colloidal fluid with a certain viscosity. Its function is to act as a carrier for pigments, mixing and connecting solid particles such as powdered pigments. The pigments are uniformly dispersed in it, relying on its wetting effect. , it is easier to be ground on the grinding machine; secondly, it acts as a binder, so that the pigment can finally be fixed on the surface of the substrate, so as to achieve the purpose of displaying text, images, marks, decoration and so on. It is also relying on its adhesion that the ink can be transferred and transferred on the printing press. Finally, on the printed matter, the binder also acts as a protective film and exhibits the necessary gloss, and can even protect the substrate.
The dissolving effect of organic solvents on resins is to attract solute molecules through the polarity of solvent molecules, which is commonly referred to as the same kind of compatibility; traditional polyurethane resins have a wide range of compatibility with organic solvents, such as ketones, esters, benzene, etc. Non-alcoholic organic solvents are all good solvents. However, in the process of making ink, in order to adjust the fluidity and viscosity of the ink, the addition of alcohol organic solvents is essential. For traditional polyurethane resins, the addition of alcohol solvents greatly reduces the stability of the resin system, often appearing turbid, Incompatibility such as flocculent precipitation. However, due to the existence of urea groups, the polyurethane resin for ink has made its compatibility with alcohol a reality, but it is worth pointing out that alcohol solvents are still pseudo-solvents. Like a true solvent, because the polarity of the molecule runs through the molecule, the ink made from the polyurethane resin has good fluidity.
In the ink manufacturing process, considering the volatilization gradient of the overall solvent system of the ink, to improve the solvent release of the printing ink and reduce the residual organic solvent of the printing solvent, the solvent used is often a mixed solvent with different volatility. In the ink manufacturing process, the main organic solvents are toluene, butanone, cyclohexanone, ethyl acetate, butyl acetate, n-propyl acetate, isopropanol, etc. Customers can adjust the volatility of the ink according to seasonal changes. adjust.
Due to the large differences in the grades of pigments on the market now, the performance of the same pigment in the polyurethane ink for the same resin from different manufacturers in terms of dispersion, ink stability, etc. will often vary greatly. Therefore, it is recommended that users follow their own actual conditions Customers need to choose pigments carefully.
Wax powder: The wax powder used in the production of polyurethane ink is often low molecular weight polyethylene wax, the relative molecular mass is generally 1000-6000, which has good solubility for organic solvents in the ink, and has affinity with the polyurethane resin itself. It is better, and has good chemical stability at the same time. It is mainly used to increase the abrasion resistance of the ink film surface, and at the same time, it can appropriately alleviate the anti-adhesion resistance of the ink itself.
Dispersant: A type of surfactant, mainly used to wet the surface of the pigment, shorten the ink production time, facilitate the dispersion of the pigment, and sometimes appropriately reduce the oil absorption of the pigment. When making high-concentration ink, it can reduce the yield value of the ink and prevent the aggregation and precipitation of pigment particles in the ink.
Adhesion promoter: The polyurethane resin for ink contains a large number of polar groups. Even if the surface of non-polar substrates such as BOPP and PE is subjected to surface corona treatment, the surface tension is generally 38 dynes to 42 dynes. The adhesion fastness of the surface of this type of substrate often needs to be appropriately added with a titanate coupling agent or a chlorinated polypropylene adhesion promoter.
The ink binder resin is a very critical raw material in the production of ink. It acts as a bridge between the colorant and the substrate, and at the same time, it gives the ink various excellent physical properties. In the production of ink, the selection of the right resin binder directly affects the performance of the ink on various substrates and the process adaptability during the printing process. When selecting the resin, it is necessary to fully consider the physical properties of the resin to match the performance that the ink needs to achieve.