Kraft paper bag is widely used because of its environmental protection and natural characteristics, and in its printing process, ensuring the ink fastness and color vividness is the key.
First of all, the pretreatment of paper is crucial. The surface of kraft paper is relatively rough and has a certain porosity. It needs to be surface treated before printing, such as applying a thin layer of primer or corona treatment to improve the surface properties of the paper, making it easier for ink to adhere, and laying the foundation for improving the ink fastness.
The selection of ink is the core link. Inks with good compatibility with kraft paper and strong adhesion should be selected, such as some water-based inks or alcohol-soluble inks specially developed for paper materials. These inks can form a tough film after drying, which is closely combined with the surface of the paper and is not easy to fall off. At the same time, high-quality inks contain high concentrations of pigments, which can ensure the vividness and saturation of colors, making the printed patterns more vivid and clear.
The parameter adjustment of printing equipment should not be ignored. During the printing process, the printing pressure, speed and ink transfer amount are precisely controlled. Appropriate printing pressure can fully transfer the ink to the tiny pores on the surface of the paper and enhance adhesion, but excessive pressure may cause the ink to penetrate too deeply, affecting the color vividness and pattern clarity; printing speed that is too fast may cause uneven ink transfer, while printing speed that is too slow will affect production efficiency. Through repeated experiments, the best combination of equipment parameters is found to ensure the ink firmness and color effect.
The choice of drying method has a significant impact on the ink firmness. Common drying methods include natural air drying, hot air drying and ultraviolet curing. Natural air drying is suitable for small batch production, but the drying time is long; hot air drying can accelerate the drying process of the ink, but attention should be paid to temperature control to avoid deformation of the paper due to high temperature or too fast conjunctiva on the surface of the ink, resulting in the internal not drying, affecting the firmness. Ultraviolet curing is an efficient drying method that can instantly solidify the ink to form a hard and wear-resistant ink layer, greatly improving the ink firmness and color vividness, but the equipment cost is relatively high.
Post-processing technology can further improve the ink firmness and color effect. For example, lamination or glazing after printing forms a protective film on the surface of the ink, which not only enhances the wear resistance and water resistance of the ink, prevents it from fading and falling off, but also improves the glossiness of the pattern, making the color more vivid and eye-catching.
In addition, the technical level and experience of the operator also play an important role. Skilled operators can accurately debug equipment, control the mixing of inks and various parameters in the printing process, and promptly discover and solve possible problems such as ink accumulation and color deviation, so as to ensure that the ink firmness and color vividness of kraft paper bag printing are optimal, and produce high-quality printed products to meet market demand.
