1. Standard process parameters
1. 1 key combination parameters:
Oven temperature: 50-60%; 60—70℃; 70—80℃;
Temperature of compound roll: 70-90℃;
Compound pressure: The compound roller pressure should be increased as much as possible without damaging the film.
About a few specific situations:
(1) When the transparent film is laminated, the temperature of the oven and laminating roller, as well as the ventilation (air volume and wind speed) in the oven have great influence on the transparency, and the upper temperature limit is adopted when the printed film is PET; When the printing film is BOPP, the lower limit of temperature is adopted.
(2) When laminating aluminum foil, if the printed film is PET, the temperature of laminating roller must be higher than 80℃, usually adjusted between 80-90℃; if the printed film is BOPP, the temperature of laminating roller cannot exceed 80℃.
1.2 curing:
Curing temperature: 45-55℃;
Curing time: 24-72 hours;
Two-component adhesive does not have ideal bonding strength immediately after compounding. It needs to be sent to the curing room for curing at 45-55℃ for 24-72 hours (24 hours for ordinary transparent bags, 48 hours for aluminum foil bags, and 7 1 hour in retort pouch). In addition, the ventilation of the curing room is also very important. Adequate ventilation can reduce curing time and further reduce solvent residue.
2. Preparation of glue solution
Standard preparation method: first, pour the main agent into the rubber mixing barrel, dilute it with 1/3 solvent, then add the curing agent while stirring, and then add the remaining solvent.
At present, the general practice is to add the main agent, pour all the solvents, and then add all the curing agents to stir. This is very simple, but the performance of the prepared glue solution depends largely on the solvent used. At present, most domestic ethyl esters are produced by formaldehyde method, and the alcohol content is quite high. Sometimes manufacturers will find that nothing has changed and the peeling strength of the composite film suddenly becomes worse. I have encountered this situation in many manufacturers, so the strength will be better if we change the glue making method.
3. The use of residual glue
Dilute the remaining glue solution twice, seal it, and add it to the newly prepared glue solution as a diluent when working the next day. When making demanding products, don't exceed 20% of the total. If the water content of the solvent is qualified, the prepared adhesive will not change much after storage for 1-2 days. However, because the qualified membrane can not be judged immediately, the direct use of the remaining glue solution may cause great losses.
4. Reasons that affect transparency
4. 1 Improper selection of adhesive:
The adhesive itself is dark;
The adhesive has insufficient fluidity and poor leveling, and cannot be fully spread on the basement membrane.
Generally speaking, the higher the solid content of the main agent, the better the fluidity, which is conducive to spreading on the membrane. Therefore, the transparency effect of 75% glue is better than that of 50% glue, and 50% is better than 40%. For the composite film with high transparency, 50% and 40% are difficult to meet the requirements.
4.2 Technical problems:
The temperature of the drying tunnel group is too high or there is no temperature gradient, and the inlet temperature is too high and drying is too fast, which makes the solvent on the surface of the adhesive layer evaporate quickly and the surface crusts. Then, when the heat goes deep into the glue layer, the solvent under the film evaporates, breaking through the glue layer, forming a ring like a volcanic spout, which also makes the glue layer opaque.
The composite cots or scrapers are defective, so they can't be pressed up at a certain point, forming a gap and being opaque.
There is too much dust in the ambient air, and there is dust in the hot air blown in the drying channel after gluing. Sticking to the surface of the adhesive layer, sandwiched between two basement membranes when compounded, there are many small spots, which cause opacity. Solution: The air inlet can use a high mesh filter to remove the dust in the hot air.
Insufficient glue application, blank space and small bubbles, resulting in mottling or opacity. Please check the application of glue to make it full and uniform.
No coated cots or dirty coated cots.
4.3 Due to the substrate, the surface tension is not high, and the wettability of the glue solution is not enough, which leads to the uneven film after drying, commonly known as "hemp film".
5. The composite membrane has small bubbles.
5. 1 raw materials:
5. 1. 1 basement membrane has low surface tension and poor wettability.
5. 1.2 The water content in the diluent is too high, and the water reacts with NCO in the curing agent to generate CO2 and form bubbles.
5.2 Process:
5.2. 1 The pressure of composite cots is insufficient or the surface temperature of steel rollers is too low, the adhesive is not activated, and the fluidity is insufficient. Dotted colloidal particles flow unevenly, and tiny gaps cause tiny bubbles.
5.2.2 The angle between the compound roll and the film is not suitable, and the wrapping angle is too large. Try to enter the compound roll in the tangential direction.
5.2.3 The air humidity is too high, the workshop environment is messy, and dust adheres to the film surface. Dust particles push up the second film and form a circle of gaps around it. At first glance, it looks a bit frothy. Look carefully, there is a black spot in the middle.
6. Composite film wrinkling problem
The composite products appear transverse wrinkles, especially at the two ends of the drum. Most of these folds are flat on one substrate and protruding "tunnels" on the other.
6. 1 material:
6. 1. 1 Insufficient initial adhesion.
6. 1.2 The surface tension of the substrate is insufficient.
6.2 Technically:
6.2. 1 basement membrane two kinds of unwinding tension are not suitable, one is too large and the other is too small. For example, BOPP/AL composite, for example, the tension of BOPP is too large, and the tension of AL cannot be too large when it is heated and stretched in the drying channel. In addition, the elongation is small. After recombination, the cooling and shrinkage of BOPP led to the aluminum foil protruding and the "tunnel" appeared laterally.
6.2.2 Inadequate and uneven gluing leads to poor local adhesion and wrinkling.
6.2.3 The winding tension is too small, the winding is not tight, and there is relaxation after compounding, which provides the possibility of shrinkage for the base material. If the winding tension is high, it should be tightly rolled and compacted, and then sent to the curing room for curing immediately after getting off the machine. Even if the process is somewhat inappropriate, wrinkles will not appear.
6.2.4 The oven temperature is too low, the oven is not ventilated, the residual solvent is too much, and the adhesive is not dry enough, which may lead to the mutual displacement of the two basement membranes.
7. Poor composite fastness
7. 1 material:
7. Selection of 1 and 1 adhesives. Composite manufacturers want all composite materials to use one adhesive. In fact, the so-called universal model is also a wish of rubber manufacturers. YH2000 and YH2000S are relatively successful. For example, YH2000S can be used in all composite materials except cooking, including AL composite materials. However, compared with the special adhesive, there is still a big gap in peel strength. Usually, the combination of cooking film, aluminized film and anti-dielectric film requires special glue.
7. 1.2 When the substrate, PE and CPP film are compounded, the surface tension should not be less than 38 dynes. When PE and CPP leave the machine, their surface tension is above 43 dynes. However, PE and CPP have one characteristic, that is, the surface tension drops very quickly after leaving the machine. Generally, they can maintain 38 dynes in one month and 35-36 dynes in three months, so in addition to buying less and saving less, for PE and CPP, we should insist on testing the dynes before going on the computer. Sometimes, when we get off the machine, the composite strength is ok, but the strength drops the next day. What is the reason? When PP and PE are processed or made into films, we need to add heat stabilizers, antioxidants, anti-sticking agents, slip agents and so on. These substances will continuously transfer and penetrate from the inside of the film to the surface. If the addition amount is large, the peeling strength will be greatly reduced, which can generally appear in 7 days at room temperature.
7.2 Ink:
7.2. 1 The ink fastness is poor, and the ink is transferred in a large area during color stripping. Reason: The permeability of glue to ink is poor, or the resin in ink is unqualified, or the coating amount of glue is insufficient, so it should be replaced by high-viscosity glue with low viscosity or ink. When the experienced manufacturer prepared the base ink, the coating amount increased by 10%.
7.2.2 The fastness of the ink is ok, but the peeling strength of the surrounding non-ink parts is low. Reason: This batch of ink release agent is too much.
7.3 Process:
7.3. 1 The coating amount of glue can't go up.
7.3.2 The laminating roller temperature is too low, the adhesive activation is insufficient, and the ink penetration is not good, which is quite obvious when AL is laminated at the bottom.
7.3.3 Different technologies shall be adopted for special structures: PET/Al/PE and PET/VMPET/PE.
8. How to make aluminized composite film
8. 1 Select the appropriate glue: YH50 1S (patented product).
8.2 Select the appropriate VMCPP and VMPET. When our company developed and promoted YH50 1S, we tracked all the product quality of domestic famous paint factories and found that the combination of VMCPP and VMPET from different manufacturers was very different. Foshan Sun, Wuxi, Danyang Daya, Anhui.
8.3 Process:
The temperature of that oven and the compound roll are respectively reduced by 5-65438 00 DEG C;
The curing chamber temperature does not exceed 45℃;
Pet/VMPET/PE (CPP) was compounded for the first time, then vulcanized for 1-2 hours, and then compounded for the second time.
If the weather is dry, please reduce the curing dose 10%.