Faults and Countermeasures in the Compounding Process of Aluminum Foil and Aluminized Film

【China Aluminum Industry Net】 In recent years, due to the oxygen permeability of PET, the permeability of PET, the poor adhesion of PE ink and the migration of color difference, the tensile elongation is large, and it is easy to wrinkle. It is difficult to overprint and most of PVC is toxic, such as The use of PVC requires high frequency heat sealing and the film tends to be broken. PT's tear resistance is poor, and it shrinks at high temperatures, decreases its strength, or becomes brittle. Packaging materials are the existence of the above-mentioned different defects, AL and aluminized films have become the more frequently used and fashionable substrates. However, AL and aluminum-plated films may cause quality problems if they do not pay much attention in the processing and compounding process. If the more common composite products have quality problems such as “spots” and “white spots”, these two quality problems are more likely to occur than the plastics/plastic and aluminum/plastic or aluminum/paper composite processing problems. It is a headache for many flexible packaging manufacturers. In response to this failure, the author was invited to conduct serious research on the quality problems that occurred in the composite processing of aluminum-plated films in color printing and ink printing plants in Hangzhou, Wenzhou, Zhejiang, Jiangsu Wuxi, Jiangyin, Henan Zhengzhou, Xinxiang, etc. The reasons and solutions are systematically introduced for the reference of colleagues in packaging and printing. First, the aluminized film composite products produce "speckled" phenomenon After the composite aluminum film produces obvious white or gray spots, these spots are more common in the process of full-print printing ink composite, mainly due to three aspects: 1, the quality of the aluminized film itself is poor, the coating is easy to peel off and the aluminized film, rolling film is not flat / especially when the adhesive coating is uneven, after the composite appears dense or messy white spots are more easy to produce . The adhesive strength of ink and adhesive on the surface is different, and the adhesion between the ink layer and the coating at the spots where the spots are produced is low (due to the uneven dispersion of the ink or adhesive) and the tightness between the layers is poor; Spotless plating has been significantly transferred with good inter-layer tightness. Reflected by the aluminum layer reflective intensity, the formation of white spots or gray spots, the degree of speckle depth and ink hiding power and the amount of sizing, especially glue leveling are very much related. Good hiding power, light spots; good leveling and uniform coating, less white spots; on the contrary, there are many spots and serious white spots. 2, the ink itself is not good tightness and poor hiding power. After the printing film is coated, the ink layer is infiltrated by the ethyl acetate in the adhesive and some of it is dissolved. After the composite ink layer/gel layer is easily infiltrated and destroyed by the solvent of the adhesive system, the depth is different. Caused by the difference in color, it forms so-called spots. 3, poor adhesive quality. This is not to say that the adhesive itself, but the affinity of the adhesive to the aluminized layer is poor, especially the uneven adhesive in the OPP printing film and BOPP printing film and the aluminized film composite, this adhesive performance is more Obviously. This is mainly due to the high surface tension of the adhesive, poor coating performance, uneven coating of the glue, and “spotting”. At the same time, the glue generally has high initial tack, poor solvent release, and due to the influence of residual solvents after aging, the strength is not as good as the initial tack. After the printing film is compounded, the ink layer and the ink layer are infiltrated by the residual solvent, and there is also the possibility of spotting. The above phenomenon will be more obvious when such adhesives are used at a high speed on a roller with more than 150 lines. If the adhesive coating fails to produce slight solubility with the printing ink, no white spots will be visible on the surface. However, after the composite process, the adhesion between the adhesive layer and the ink layer or even the printing film layer cannot reach the actual value of the packaged product. Demand and easily stripped. In general, there are more “spots” caused by the above three reasons, but we can use the following methods to eliminate this phenomenon: 1. The use of inks with better hiding power is a more fundamental method to eliminate the phenomenon of spotting caused by the first and second reasons. In addition, it is possible to dip the deep-printing line roller to increase the thickness of the ink layer, but this will increase the cost. For the flexible package manufacturers, it is a method that they do not wish to adopt. However, it may be considered in the absence of other good measures. 2. The use of suitable adhesives for aluminized films is an effective way to eliminate the speckle phenomenon caused by the three causes. The special adhesive for the aluminized film is moderate in molecular weight and uniform, and the initial adhesive force is not very high, but the coating performance is excellent, the solvent release is good, and the peel strength after aging is good. In addition, if you do not have a good adhesive for aluminized film, you can use a deeper anilox roller, at the same time reduce the operating concentration, slow down the speed, you can also reduce or solve the phenomenon of spots. 3, if it is caused by the pigment in the ink, there are often spots in the three cases: (1) titanium dioxide and other fight mixed and the particle size is not equal, and one of the pigments in the flocculation state, but the same density, Spots will appear; (2) titanium dioxide and other particles of the same size, and one of the pigments in the flocculation state, but the density is different, there will be spots; (3) titanium dioxide and other particles are not equal in size, but the density is not The same, the same will also appear spots. These three types of failures are more likely to occur after the addition of silica to the floccules or to the “active particles” produced by the long grinding time of the ink. For this phenomenon, as much as possible, all the dry powders should be mixed before being put into dispersion, or the amount of white carbon black can be reduced, or the dispersant or antistatic agent can be increased, or the grinding time can be shortened (since most of the failures occur at the outlets are shallow or fundamental Unengraved large-area layouts) to prevent the competition between abnormal colors and fillers - gathers and adheres to the plate roller and is distributed on the printing surface by a doctor blade. Second, the general composite film white point generation and processing methods in the aluminum composite film white spots, there are other composite film also will appear on the white spots, the white spots can be randomly distributed, uneven size. There are two kinds of situations, one is: When the machine is down, but it basically disappears after aging; the other is: There is a time when the machine does not disappear after curing. The latter is the larger issue that affects appearance. Such spots are more likely to appear in white or light yellow prints. In fact, it should be said that as long as such a white point appears, it is generally full version (except for equipment reasons), but the difference between white and light yellow hiding power is easy to see. There are many reasons for the phenomenon of white spots. There are three main reasons: 1. The ink particle size is large and the particle size distribution is too wide. Generally, the size of the white ink has a great influence. The ethyl ester in the adhesive is a good solvent for the ink. The result of invading the ink particles with different particle sizes is different. The color change after heating or compounding or drying in the oven will be reduced and may disappear. 2. The surface tension of the adhesive is high, and the effect of infiltrating and spreading on the aluminized film is poor. This is the "white spot phenomenon" of the current aluminized film, and it is also the main reason for the occurrence of spots on other composite films. The coating effect of the adhesive is not good, and after the printing layer is covered, the color of the different parts changes, and the same effect as above occurs, and sometimes a large spot is generated. 3, equipment process reasons. On the one hand, the reason for this is that the workers are not aware of the special characteristics of the aluminized film composite, and the aluminized film compound has its unique place; on the other hand, the pressure of the equipment on both sides during the sizing process is inconsistent, even in the drying and coating systems. The problem itself cannot ensure that the adhesive is sufficiently uniformly coated or that sufficient volatilization of the ethyl ester cannot be guaranteed. There are other reasons, such as full-bottom printing line roller is too shallow, reducing the hiding power of ink and so on. The following measures can be taken to eliminate “white spots”: 1. Different batches of inks will increase drug detection indicators and be strictly controlled. In particular, the size and fineness of full-bottom inks will not be used outside the standard range. 2, the use of aluminum film special adhesives. The surface tension of the aluminum-plated composite special adhesive is low, and the effect of coating and spreading on the surface of the aluminized layer is obviously better than that of the general-purpose adhesive. The use of aluminized film adhesives makes it very easy to control the leveling of the glue and has an ideal coating state. From the adhesive coating state alone, the use of aluminized adhesive can eliminate white point phenomenon. 3. The viscosity of the glue has a certain matching relationship with the king's first roll number. Exceeding the match range too much will destroy the coating state of the glue, causing the occurrence of “white point” and other serious failures, but on the aluminum film. It seems that the main reason for the emergence of "white spots" is even more concern. 4, using aluminum film coating method. The commonly used coating process is a printing film (protective layer) coating, where a special coating method is used to avoid the problem of inhomogeneity of the ethyl ester to the ink layer, but this process has a great limitation on it. First of all, it is limited to the compounding of VMPET; second, it will sacrifice a certain peel strength. 5, manufacturers must adhere to the regular cleaning of the coating roller system, to master the correct coating roller cleaning method. In the production of white or light yellow printing film, we should pay attention to two points: First of all, before the production of the scraper, coating roller, flat roll and other thorough cleaning; Second, for the old domestic dry machine, speed than normal Slower speed to ensure the drying effect. Third, the pitting on the aluminized film is often caused by the pinhole in the ink (blank point / pit) failure, the general exclusion method: First, adjust the composite roller; second is to increase the amount of plastic coating; third is to increase Defoamer dimethyl silicone oil-201; four is to use a straight blade as far as possible, and increase blade edge 1-2mm, or use a soft blade (such as steel tape instead), and the blade angle is adjusted to not less than 45 ° angle; fifth is to add a piece of eraser on the back of the scraper, which can effectively scrape off the spots caused by the oxidized crust in the printing and graphic ink system due to poor dispersion; and add white to the printing ink. Carbon black, to promote the printing ink ink film thickening and increase the hiding power of the white ink ink film; seven is to re-print again, to increase the thickness of the ink film; eight is to choose the deep engraving gravure to improve the ink transfer rate; Nine is A stirrer is placed in the ink fountain to ensure the uniformity of the printing ink during transfer. The tenth is to replace the printing ink with high viscosity and anti-static printing or to slow down the printing speed in an attempt to eliminate pitting, pinholes, spots and white spots. the goal of. It has been known that both the pure aluminum foil (AL), the vacuum aluminized film, or the homoepitaxial growth of the aluminized film on the surface/that is, the surface aluminum, directly demonstrate the "deposition" from experimental production in practice and theoretically. The up-diffusion motion of this atom that the atom's atoms can climb up during growth - the formation of quantum dots with certain crystal phases / is also a phenomenon that we cannot imagine in the growth mechanics of some aluminum products, aluminum foils, and aluminized films. In the past few years, China's packaging and printing industry has poor adhesion to the ink and ink film, and spots, white spots, etc. that appear after compounding cannot be accepted as a technical problem—causality. We can only improve the quality of packaging and printing products in China by actually relying on high-efficiency additives and new materials to make up for deficiencies in their aluminum-plated composite printing products.