Carton paper printing common faults and solutions (in)

Sixth, the paper surface strength caused by the powder off, hair loss, bubble and skinning failure phenomenon

When the surface strength of the whiteboard paper is poor, the phenomenon of falling powder, lint, blistering and peeling occurs easily during printing. Falling powder refers to the fact that the paper surface falls off the powdery material, such as paint, fillers, pigments, etc., from the paper surface. Lint off means that the fibers on the paper are peeled off from the surface of the paper during the printing process. Paper blistering and peeling means that during the printing process, the outer surface of the paper, under the action of external forces such as the peeling force of the printing and the viscosity of the ink, causes the coating layer of the paper to be split with the underlying fibrous tissue and blisters or peels off. phenomenon. From a print quality point of view, the use of paper with high surface strength and good quality is the best choice for avoiding the problems of powder falling, pulling, blistering and peeling on the paper surface and improving the printing quality of the product. However, what kind of paper is used for printing is often not unilaterally determined by a printing factory. Some common products, customers only require the use of low-end white paper to print. This requires that some necessary measures be taken from the printing process in order to prevent the occurrence of printing quality failures. According to the experience of the printing production process, the following measures can be taken for the paper with poor paper surface strength to reduce or avoid the occurrence of powder failure, nap, blistering, and peeling quality failures.

1. Adjust the viscosity of the ink. Papers with poor surface strength on paper, if printed with high-viscosity inks, are most prone to powder failures, naps, blisters, and peeling quality problems. In this regard, additives suitable for the printing process conditions may be selected to adjust the flowability and viscosity of the ink in order to reduce the adhesion and stripping tension of the ink layer to the paper surface during the printing process. In the past, the author had encountered serious powder dropping, blistering, and peeling failures when printing whiteboard paper (field layout) in the practice of letterpress printing. I first used a de-adhesive and an oil-adjusting ink to adjust the viscosity of the ink. Liquidity, resulting in powder off, lint, blistering and peeling problems have been resolved, but the printing ink effect is very unsatisfactory, layout is very obvious, and the drying speed is slow. Later, the use of bright oil to adjust the ink flow, not only play a role in reducing the viscosity of the ink, but the printed product is full of ink, high brightness, good visual effects, and drying speed. Therefore, the selection of suitable additives according to the printing characteristics is a very important technological measure.

2. Adjust the printing pressure. If the printing pressure is too light or uneven, the ink layer on the plate cannot be completely and evenly transferred to the surface of the paper, and the printing defects of the printing are likely to occur. However, if the printing pressure is too high, the coating layer and the fiber structure on the paper surface are easily destroyed, and powder falling, linting, blistering, and peeling quality defects are likely to occur. Therefore, the use of uniform and appropriate printing pressure is an important condition for good ink transfer, and it is also one of the technical measures to prevent the occurrence of undesirable problems.

3. Adjust the printing speed. In the daily production, if the cardboard with poor surface strength is printed at a higher speed, the phenomena of falling powder, pulling hair, blistering and peeling quality will be obviously exacerbated. On the contrary, if the speed of the machine is lowered for printing, this failure phenomenon will be significantly reduced. This is because the printing speed is high, and the peeling tension during the printing process is also large. In this way, the adhesive ink layer on the printing surface is not quickly, evenly and completely absorbed by the paper surface during printing and separation, but it is easy to put on the paper surface. The partial coating or fiber pulls off. Therefore, paper with poor printing surface strength should be printed at a lower speed, which is beneficial to reduce or avoid the occurrence of powder failure, nap, blistering, and peeling quality failures.

4. Choose the right machine for printing. For a paper with poor surface strength, what structure of the printer is used for printing has a great influence on the printing quality. For example, the letterpress process is used as an example. If a flat and flattened machine is used to print, the ink layer on the print sheet and the plate surface are in contact with and separated from each other at the same time. Thus, the greater the separation area, the greater the tension when peeling. The coated layer or fiber on the surface is easily pulled off. In a circular press or circular press structure, the contact between the printed sheet and the ink layer on the plate is linear, and the tension when the printed sheet is peeled off after absorbing the ink is also small, and it is not easy to destroy the paper surface. Therefore, for the paper with poor surface strength, printing with a circular press structure will help improve the printing quality of the product.

5. Reasonably arrange the printing color sequence. The reasonable arrangement of the printing color sequence is an important part of preventing the paper from falling off or fluffing. Therefore, for the paper with poor surface strength, a small layout should be printed first and a large layout should be printed first; first, the low viscosity printing ink should be printed. Large ink (non-color overlay printing plate products). If multi-color printing is used, if there are extra color groups, the front color group may not be used, so that the printed sheets can be left empty past the previous color group, or the blank sheet can be imprinted or "overwatered" by the preceding color group. This can greatly reduce the print off or pull the hair phenomenon.

6. The paper with poor surface strength was adjusted for small printed products. For some paperboards with poor surface strength, despite various methods, they still cannot solve the problems of powder and paper blistering. This is because the adjustment of the ink viscosity and the peeling tension is, after all, limited, and there is no certain sticky ink, and it is difficult to achieve normal printing. For example, when we once printed a batch of whiteboard paper with full ink absorption (beerboard paper), the viscosity of the ink has been adjusted to the minimum limit. However, there are still blisters on local paper when printing, which seriously affects the quality of the product. Later, we adjusted this kind of paperboard to print products with less ink absorption, and no paper blisters appeared. Therefore, choosing the right cardboard for printing according to the characteristics of the printed product is one of the important measures to prevent quality failures.


Seven, ink bad bow I from the print quality failure

1. Bad ink drying. If the ink is dried too fast, it will cause the phenomenon of early conjunctiva formation in the ink layer, and the ink may be unevenly colored and the paste may be damaged during printing. This is mainly due to the excessive use of dry oil in the ink and the excessive drying of air humidity. For the above reasons, the ink is crusted on the ink roller, and an appropriate amount of dry oil can be added to suppress the drying speed.

2. The discoloration of ink on the printed page caused poor coloration. Due to the poor pigment performance of inks, inferior organic pigments are used, or heterogeneous pigments are mixed in and used, so that a chemical reaction causes discoloration. This ink is not suitable for color printing.

3. The ink on the printed page fades. If too much ink is added to the ink or the detackifier is added, and the water content of the plate is too large, the sensory quality of the printing plate graphic portion will be reduced, and the ink color of the printing product will be faded. In this regard, the ink should be re-adjusted, that is, adding some of the original ink to the thin ink, so that the concentration of the ink is increased; the moisture of the printing plate is reduced to improve the coloring power of the ink.

4. The back of the printed product is dirty. When the printing ink layer is thick, or when the amount of the auxiliary agent is not properly adjusted, the drying speed of the ink is reduced, and the back surface is easily dirty. At this time, a certain amount of desiccant and anti-adhesive agent can be added to the ink. , to eliminate the back of the printed material dirty phenomenon.

5. The layout ink lacks gloss. Due to the poor texture of the varnish, the insufficient amount of varnish, and the excess water on the plate, the printing ink layer will lack luster. For color printing products, bright ink can be used for printing, or an appropriate amount of brightener can be added to the ink to increase the gloss of the printed ink layer.

(to be continued)