Composite rollers, guide rollers and rollers play an important role in the printing of composite films . Uneven rollers can cause spots on the glue. Unbalanced guide rollers and composite rollers cause wrinkling of the composite film.
1. The peel strength of the composite film is not enough
Divided into the following situations:
The glue does not cure completely, and it remains sticky on the glue surface when peeled off. the reason:
1) The ratio of the adhesive is wrong, and the insufficient curing agent ratio leads to incomplete curing. When preparing the adhesive, it should be formulated according to the ratio parameters specified by the adhesive manufacturer;
2) The purity of the solvent is not enough. The solvent contains water or alcohol exceeding the standard. The water or alcohol reacts with the curing agent in the glue. The reduced ratio of the curing agent leads to incomplete curing of the glue. The solvent used for dry recovery is ethyl ester, so every batch of ethyl ester should be sampled when entering the factory. If it is found that the purity is not enough, it cannot be used;
3) The high residual solvent of the ink in the printed film causes insufficient curing of the glue. A part of the residual solvent of ink ( especially PET ink ) will react with the curing agent in the glue, thereby consuming the curing agent and causing insufficient curing of the glue. Countermeasures: â‘ It is best not to compound immediately after the film is printed. If time permits, it can be placed for 1-2 days before compounding; â‘¡After the film is printed off the machine, the residual solvent is detected. Proportion of agent; â‘¢ Use fast curing glue.
4) The curing temperature of the composite film is low, the curing time is not enough, the crosslinking is insufficient, and the curing is incomplete. Countermeasure: Increase the curing temperature or use fast curing glue.
2. The apparent problem of composite film
1) Small dots. Generally, it is less likely to appear immediately after lamination, unless it is muddy impurities. This phenomenon may occur in the aluminum plating film for a period of time after lamination, because the ink corrodes aluminum. When the ink exhibits a certain acidity or alkalinity, and the amount of glue is small, it cannot form a connected layer. This may happen.
2) Small gray spots. There are two possibilities for the occurrence of small gray spots. One is the unevenness of the roller causing spots of glue, and the other is the unevenness of the ink causing no spots of compacted ink. Both possibilities are related to the process, which can be solved by adjusting the process to increase the thickness of the amount of glue.
3) Little white dots. Generally, the ink on the surface changes color easily. Mostly appear in the composite of aluminum coating. There are two reasons for this: one is that the original color of the ink is not strong or unevenly covered, especially the white ink, so that the aluminum color penetrates, and small white spots are formed where there is no aluminum color penetration; second, the process reason, the temperature of the drying tunnel ( Especially for the first-level drying tunnel ) Too high or too thick glue amount results in the condensation of the surface of the rubber layer in the first-level drying tunnel. When the ethyl ester rushes out of the second and third-level drying tunnel, the glue is squeezed out, showing the true color of the ink . The solution is to increase the hiding power of the ink or adjust the suitable temperature of the first, second and third drying tunnels, and gradually increase the temperature. Avoid excessive high temperature.
4) Small crystal points. There are many small crystal dots on the transparent film, there are two kinds of bumps, and the causes are different: the small crystal dots that are protruding are mostly due to the glue, or it may be because the machine has not been cleaned. The method to eliminate the small crystal points is to strictly follow the correct method of glue distribution, and the machine must be cleaned after use; the small crystal points recessed, carefully observed with a magnifying glass, you will find that there are small bubbles, which mainly It is caused by too much water.
5) Small scar spots. This is mainly due to the uneven film activation process, and the same scars appear during the printing process. Of course, it may also be caused by too long activation time.
6) Wave pattern. The wave pattern is easy to occur on the white film, mainly because the molecular weight of the glue is uneven. After the hot drying tunnel and the hot roller, the elastic polymer chain shrinks, and the intramolecular shrinkage of different molecular weights is inconsistent. Wavy lines are caused evenly. In this case, the cause of the glue should be considered.
7) The influence of the film on the surface quality. Various reasons for the smoothness and uniformity of the surface of the film may cause similar phenomena of the above six phenomena. To distinguish whether it is the cause of the film or the above six conditions, you can carefully observe the film without the laminating film with a magnifying glass. Since the transparent glue is between the two layers of film, a composite film is formed together with the two layers of film. Spots, waves, etc. on small films magnify, and many situations require careful observation to find problems.
3. Tunneling phenomenon of composite membrane
Due to the shrinkage of the film after compounding, the edge part or the central part delaminates like an earthworm, which is called the compound film tunneling phenomenon. The reasons for this phenomenon are as follows:
1) Poor tension control during compounding causes the composite substrate to shrink after compounding and the difference in shrinkage ratio is large, which destroys the adhesion of the glue layer of the composite film, and the tunnel phenomenon is solved. The solution should be based on different composite substrates during compounding The tensile properties set the appropriate tension.
2) The film is wrinkled and uneven in thickness. In order not to wrinkle the composite film during compounding, the composite film is tunneled by increasing the tension for compounding. The solution is to check the state of the film during unwinding during compounding, such as the phenomenon that the film is wrinkled and edge shaking is not used.
3) The molecular weight of the adhesive is small, resulting in a low initial adhesion of the composite film, thereby causing the tunneling phenomenon of the composite film. The solution is to choose high molecular weight, high cohesive, fast curing adhesive.
4) Due to the excessive coating amount of the adhesive, the composite film is not completely cooled after being heated by the roller, and the adhesive layer still has a certain fluidity, thereby causing the tunneling phenomenon of the composite film. The solution is to appropriately reduce the amount of adhesive applied.
4. The slip of the composite membrane is poor.
The slip of the composite membrane is poor, and the friction between the membranes is large, which reduces the composite. The opening performance and operation performance of the membrane. The main reasons for the poor slip of the composite film are:
1 ) The curing temperature of the composite membrane is too high. Treatment method: reduce the aging temperature, the aging temperature should not exceed 50 ℃ , if time permits, it can be cured naturally.
2) The slip of composite substrate is poor. Treatment method: composite film dusting.
3) The composite membrane absorbs moisture. Treatment method: pay attention not to get wet during storage and transportation, and pay attention to the protection of the composite membrane when the indoor humidity is too high.
5. Wrinkling of composite film and the causes of wrinkling of composite film
1) The composite substrate itself is wrinkled. Treatment method: pay attention to check the state of the composite film when compounding, and do not use it if there are uneven thickness, ruffles, wrinkles and other phenomena.
2) The unbalance of the guide roller and the composite roller causes the composite film to wrinkle. Treatment method: Check and adjust each guide roller and composite roller to balance them.
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