Composite rollers, guide rollers, and rollers play a crucial role in packaging and printing composite films. Uneven rollers can cause black spots on the glue, while uneven guide rollers and composite rollers can cause wrinkling of the composite film due to uneven aluminum rollers.
1. The insufficient compressive strength of the composite film detached from the aluminum roller can be classified into the following situations: the strong adhesive is not completely dried and solidified, and even when detached, there is still adhesion on the surface of the adhesive.
Reason: 1) The preparation of the adhesive is incorrect, and the proportion of epoxy curing agent is not sufficient, resulting in incomplete drying and solidification.
When configuring adhesives, it is necessary to follow the main parameters required by the adhesive manufacturer for preparation; 2) The purity of organic solvents is insufficient, and the presence of water or aldehydes in organic solvents exceeds the standard. Water or aldehydes react with the epoxy curing agent in the strong adhesive, resulting in incomplete drying and solidification of the strong adhesive due to the reduced proportion of epoxy curing agent.
The organic solvent used for drying and compounding is ethyl ester, so each batch of ethyl ester must be sampled and inspected when entering the factory. If it is found that the purity is insufficient, it cannot be applied; 3) The high residual organic solvents in the ink in the packaging printing film cause insufficient drying and solidification of the strong adhesive.
Part of the residual organic solvents in ink, especially PET ink, will react with the epoxy curing agent in the strong adhesive, thereby consuming the epoxy curing agent and causing insufficient drying and solidification of the strong adhesive.
Preventive measures: ① It is best not to immediately composite plastic film packaging after printing. If time permits, it can be left for 1-2 days before composite; ② After the packaging printing film is processed at a high speed, residual organic solvents can be inspected. If the residual organic solvents are high, the proportion of epoxy curing agent can be moderately increased during composite; ③ Using strong adhesive that quickly dries and solidifies.
4) The composite film has a low maturation temperature and insufficient maturation time, resulting in insufficient chemical cross-linking and incomplete drying and solidification of the aluminum roller.
Preventive measures: Increase the ripening temperature or use strong adhesive that quickly dries and solidifies.
2. Difficulty in conductivity of composite plastic films: 1) Small ink dots.
The probability of appearing immediately after lamination is generally low, unless it is residue or residue.
After a period of time after lamination, the PET film may experience such a situation due to the etching of aluminum by the ink. When the ink exhibits a certain acidity or alkalinity, and the clamping force is small, which cannot produce a connecting layer, it is very likely to cause such a situation.
2) Small gray dots.
There are two possibilities for small gray spots to appear: one is the uneven roller causing black spots on the glue, and the other is the uneven ink causing black spots on the ink that have not been compacted.
Both probabilities are related to the processing technology and can be adjusted according to the processing technology to improve the thickness of the upper clamping force.
3) White dots.
It is very easy for the ink on the surface to fade.
It often appears in the composite of pet films.
There are two reasons for this: firstly, the adhesion of the ink primary color paint is weak or uneven in covering, especially with white ink, which causes the color of aluminum to seep out, and areas without aluminum tone to seep in produce white spots; The second reason is due to processing technology. If the temperature of the curing furnace (especially the first stage curing furnace) is too high or the clamping force is too thick, it will cause the surface layer of the adhesive in the first stage curing furnace to solidify. When the ethyl ester is washed out in the second and third stage curing furnaces, it will squeeze out the strong adhesive and highlight the original color of the ink.
The solution is to improve the adhesion of ink and paint or adjust the appropriate temperature of the first, second, and third stage curing furnace aluminum rollers to gradually increase the temperature.
Prevent the first level temperature from being too high.
4) Small crystal dots.
There are more small crystal dots generated on the protective film, there are two types: convex and concave, and the causes are different: most of the protruding small crystal dots are due to glue mixing, and it is also very likely that the equipment is not cleaned properly.
The way to remove small crystal dots is to strictly follow the appropriate glue mixing method, and the equipment must be cleaned and tidy after application; The concave small crystal dots, when carefully observed with a high-power magnifying glass, will reveal small bubbles inside, which is mainly caused by insufficient moisture.
5) Small scar spots.
The main reason is that the membrane activity solves the problem of uneven membranes, and the same scars also appear throughout the packaging and printing process, which is likely due to the long activity time.
6) Wave shaped.
Waves are very likely to occur on the white film, mainly due to uneven adhesive content. After undergoing thermal curing in a furnace and hot rollers, the polymer material chains with extensibility will collapse, and the molecular structures with different contents will collapse unevenly. This type of uneven internal contraction leads to wave shapes.
Such situations should be considered due to the adhesive.
7) The harm of plastic film to process performance.
Due to various reasons such as the smoothness and uniformity of the surface of plastic films, it is highly likely that these six conditions will be similar.
To determine whether the difference is due to plastic film or the six conditions described, it is possible to carefully observe plastic film without aluminum roller film using a high-power magnifying glass. This is because the fully transparent strong adhesive is placed in the middle of the double-layer aluminum roller and forms a composite film with the double-layer film. Using a high-power magnifying glass can enlarge the black spots, wavy lines, and other areas on the originally small plastic film. In many cases, careful observation is necessary to identify the problem.
3. The construction status of composite membrane tunnels.
After composite, due to the folding of the plastic film, a part of the edge or the middle part resembles a loach like delamination, which is called the construction condition of the composite film tunnel.
The key reasons for such situations are as follows: 1) Poor tension sensors during the entire composite process cause the composite board to collapse after composite and the proportion of collapse is large, which damages the adhesion of the strong adhesive layer of the composite film. The solution to the tunnel construction situation is to set appropriate support forces based on the stretching characteristics of different composite boards during composite.
2) The plastic film is wrinkled and uneven in thickness. In order to better prevent wrinkling of the composite film and increase support, the composite is carried out, resulting in tunnel construction of the composite film.
The solution is to check the condition of the plastic film during unwinding during lamination, and not apply it if there are wrinkles, shaking edges, etc. on the plastic film.
3) The low content of adhesive results in low initial adhesion of the composite film, which in turn leads to tunnel construction conditions of the composite film.
The solution is to use adhesive with high content, high team cohesion, and rapid drying and solidification.
4) Due to the insufficient amount of adhesive applied, the composite film is not completely cooled after being heated by the hot melt roller, and the adhesive aluminum roller layer also has a certain degree of fluidity, which leads to tunnel construction conditions of the composite film.
The solution is to moderately reduce the amount of adhesive applied.
4. The smoothness of composite films is poor.
The smoothness of the composite film is poor, and the sliding friction force in the middle of the film is high, which reduces the opening and practical operation characteristics of the composite film.
The key reason for the poor smoothness of the composite film is that: 1) the maturation temperature of the composite film is too high.
Solution: Reduce the ripening temperature, and it is best not to exceed 50 ℃. If time permits, the ripening process can naturally be stronger.
2) Composite panels have poor smoothness.
Solution: Composite film powder spraying.
3) The composite film is damp.
Solution: Pay attention not to stick water during storage and transportation, and pay attention to the safety protection of the composite film when the indoor humidity is too high.
5. Composite film wrinkles.
The reason for the wrinkling of the composite film.
1) Composite panels wrinkle themselves.
Solution: Pay attention to checking the condition of the composite film during lamination. If there are uneven thickness, lotus leaf sleeves, wrinkles, etc., do not apply.
2) The imbalance between the guide roller and the composite roller causes wrinkling of the composite film.
Solution: Check and adjust the balance of each guide roller and composite roller.