[China Aluminum Industry Network] The composite aluminum film can be described as white point phenomenon. The composite product apparently has obvious white spots. The white spots can be randomly distributed and have uneven sizes. 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 on white or light background printing effects. In fact, it should be said that as long as such a white point occurs, it is generally full version (except for equipment reasons). Only the poor hiding power of white and light background 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 or the particle size distribution is too wide, and the white ink generally has a large influence on the particle size. The ethyl ester in the adhesive is a good solvent for the ink, and the results of infiltration of ink particles with different particle sizes are different. The color change after drying in the oven will produce a difference, and it seems that a “white point” occurs. In this kind of situation, when the machine is down, the white point phenomenon will be lessened and may disappear after curing.

2. The surface tension of the adhesive is high, and the effect of infiltration and spreading on the aluminized film is poor. This is one of the main reasons for the current "white point phenomenon" of aluminized films. The effect of the adhesive coating is not good. After the printing layer is covered, the color of the different parts will change, resulting in the same effect as before, and sometimes large spots will be produced.

3. Equipment process reasons. On the one hand, the reason for this is that workers are not aware of the special characteristics of the aluminized film composite, and the aluminized film composite has its unique place; on the other hand, the equipment drying, coating, and the system itself cannot guarantee the full uniformity of the adhesive. Coating or can not guarantee the full volatilization of ethyl ester.

There are other reasons, such as full-bottom printing network roller roller mesh is too shallow, reducing the hiding power of ink and so on.

Take the following measures to eliminate white spots:

1. Different batches of inks will increase the particle size detection index and be strictly controlled. In particular, the particle size and particle size distribution of full-bottom inks will not be used outside the standard range; select excellent stable suppliers.

2. Use aluminum foil special adhesive. The special adhesive for aluminized films has a lower surface tension, and the effect of coating and spreading on the surface of the aluminized layer is significantly better than that of a general-purpose adhesive. The use of aluminized adhesives makes it very easy to control the leveling of the glue and has an ideal coating state. From the state of adhesive coating alone, the use of aluminized adhesive eliminates the possibility of white spots.

3. The viscosity of the glue has a certain matching relationship with the number of roller lines of the cable. Exceeding the matching range too much will destroy the coating state of the glue, resulting in the occurrence of “white spots” and more serious other effects, but in the aluminized film. It seems that the main cause for the "white point" is more concern.

4. Using aluminum film coating method. The commonly used coating process is the printing film (ink surface) gluing. A special coating method is used here to avoid the problem of uneven infiltration of the ink layer by the ethyl ester, and the coated adhesive can cover the coating sufficiently uniformly. The aluminum layer surface, which can eliminate white spots. But this kind of craft has its very big limitation, first of all, is only limited to VMPET compoundes, but other aluminized film influences the heat under the influence of the tension under the influence of the tension in the oven, will cause the tensile deformation; Second, will sacrifice a certain peeling strength .

5. Flexible packaging companies must adhere to the regular cleaning system of the coating roller and grasp the correct cleaning method of the coating roller. In the production of full-white or light-bottomed printing films, two points should be noted. First, the scraper, coating roll, spreading roll, etc. should be thoroughly cleaned before production.

6. The adhesive should be thoroughly dried. Due to the better barrier property of aluminum plating, if the bonding in the composite film is not completely dry, then after the composite film enters the curing chamber, the residual large amount of solvent needs to be released quickly. Under the barrier of the aluminum plating film, bubbles will inevitably form. . Even if there is no white point when leaving the machine, white spots will appear after aging.

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