White spots are one of the common problems in flexible packaging plants when they are solvent-free compounding. The so-called white spots refer to the white spots that are different from other parts where there is ink after compounding. Once the white spot is generated, it is more difficult to solve. This article introduces in detail the causes of abnormal white spots in the solvent-free compound process, for reference by colleagues. 1. Ink is not compatible with glue Especially full-page ink printing is easier to produce. This is due to the poor compatibility and poor matching of the ink and the adhesive. 2. The surface finish of the glue roller and composite roller is too poor or there is foreign matter sticking At this time, it appears as spots appearing repeatedly. You can determine which roller has a foreign object by measuring the distance between the two spots that appear repeatedly, just clean it. 3. The difference in ink coverage rate produces white spots At this time, white spots appear in white and light-colored ink, and the dark part looks good. The solution is to improve the hiding power of white ink, such as checking the fineness of white ink, grinding ink with good fineness, and improving the hiding power. The simplest method is to reprint white ink once. It can also be tested for fineness and hiding power when purchasing ink, and then used after passing the test. 4. Uneven application of adhesive, low glue application There are not enough adhesives that can penetrate the entire ink to produce white spots, or the compatibility of the adhesive with the ink is too poor. White spots are more likely to appear on the composite aluminum-plated film or aluminum foil. The light reflected by the aluminum-plated and aluminum foil surfaces meets the cross-section when passing through the bubbles, which will cause refraction or diffuse reflection and form white spots. Solution: The amount of coating can be increased appropriately to control the composite tension to make the coating even. 5. Uneven tension of substrate film The tension of the base film is uneven, and it is discounted before entering the composite roller, resulting in poor local composite effect, bubbles appear, and the macroscopic performance is white spots. 6. Compounding and gluing pressure Inadequate pressure setting in compound parts or glued parts is big or small. The uneven pressure prevents the air in the glue from being expelled during the compounding process. In addition, the angle between the second base material and the composite pressing roller during compounding should not be too large, otherwise air is easily formed to form bubbles. 7. The roughness of the film surface of the two substrates is too large, and the additives float In the past, the surface roughness of the substrate film was generally 0.08 ~ 0.16um (the surface roughness of the solvent-free adhesive film should be lower). If it is higher than this roughness, the unevenness of the film surface is serious, and the unevenness is difficult. It is difficult for the ink and the adhesive to fill the uneven holes, resulting in composite bubbles. If the quality of the base film additives is poor or rises when heated, white spots will also occur. Anti Pigmentation Mesotherapy,Mesotherapy For The Face,Mesotherapy For Skin Pigmentation,Mesotherapy For Acne Before And After Treatment Shijiazhuang Asa Technology Co., Ltd. , https://www.asaantiwrinkle.com