Analysis of several delamination phenomena of the

2022-07-24
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Analysis of several delamination phenomena of aluminized composite film

the delamination phenomenon of aluminized composite film has always troubled packaging enterprises. There are two kinds of delamination phenomena of aluminized composite film, which are analyzed one by one as follows:

first, the phenomenon of "transfer" of aluminized layer

the "transfer" of aluminized layer means that most of the aluminized layer is transferred to other films when the aluminized composite product is stripped between layers, resulting in the decrease of stripping strength, The resistance of the product to contents is reduced, and the product quality is affected. This is a phenomenon often encountered by many composite flexible packaging manufacturers, and it is also a difficult problem to solve. VMCPP and vm-pet are the most widely used aluminized films. In practical application, pet/vm-cpp has more transfer, because polyester (PET) has certain polarity and stronger fastness to contact with aluminum. At present, the aluminized films on the market can be divided into coated aluminized films and uncoated aluminized films. In the production process of aluminized films, the coated aluminized film is coated with a layer of connecting material on the film. The coating is used to enhance the bonding strength between aluminum and the film. The quality of this layer of coating will also affect the degree of transfer of the aluminized layer. Most of the coated aluminized films are used in product packaging with boiling requirements or certain tolerance requirements, Mainly aluminum plating on pet

most of the "transfer" of the aluminized layer occurs on the composite of the aluminized film without coating. Therefore, in addition to the quality factors of the aluminized film wood body, there are also factors affecting the adhesive, dilution solvent, inner layer material and processing technology

to fundamentally solve the problem of "transfer" of aluminum coating, the following points must be paid attention to in the operation of composite process:

1. Ensuring the best quality of aluminum coating itself is the prerequisite for solving other problems. If the quality of the aluminized film itself is the worst, the best composite process and the best adhesive in the above content are powerless

2. Selecting appropriate adhesive is the most effective method to solve the transfer of aluminum coating. In the composite aluminum coating, the adhesive with slightly larger molecular weight, more uniform molecular weight distribution, good solvent release and good coating performance should be selected. Although the adhesive with the smallest molecule has good coating performance, it has strong intermolecular activity and is easy to erode the aluminum coating and damage the aluminum coating. Do not choose adhesives with large molecular weight, uneven molecular weight distribution and poor solvent release, because the solvent has strong penetration ability, which will damage the coating and affect the bonding strength. At the same time, the molecular weight of adhesives with large molecular weight is bound to be uneven in the production process. (the low purity of diluted solvent affects the aluminum plating layer as well.

3. Enhance the flexibility of the adhesive film. When preparing the adhesive solution, appropriately reduce the amount of curing agent to reduce the degree of cross-linking reaction between the main agent and the curing agent, so as to reduce the brittleness of the adhesive film, keep it flexible and extensible, and help to control the transfer of the aluminum plating layer. At the same time, the coating amount is related to the peel strength of the product. Too much or too little is not enough Will affect the quality of products; Too little will result in small composite fastness and easy peeling; Too much will increase the cost. At the same time, the coating amount is large. It is completely fixed that in recent years, the medical reform has gradually increased the support for medical devices. The time will be long, and the bonding molecules will have enough activity capacity to damage the aluminum coating. The gluing amount is generally controlled at 2.8~3.5g/m2

4. Reduce the ripening time. In principle, the ripening temperature of ordinary films is generally controlled at about 45 ℃, while the ripening temperature of composite products coated with aluminum film should be increased in principle. The high-temperature short-term ripening method is adopted, and the general ripening temperature is 50 ℃; Do not ripen at low temperature for a long time

5. Influence of inner film. When some manufacturers composite pet//vm-pet//pe, they often composite pet with vm-pet after curing, and then composite PE. However, the aluminized layer does not transfer after pet//vm-pet is cured. After PE is compounded, the aluminized layer transfers. Some manufacturers whose biggest silver carp is more than half a meter long are pet and vm-pet, which are directly compounded with PE without curing, and the phenomenon of aluminum coating transfer will also occur. The occurrence of the first phenomenon is directly related to the temperature and curing time of various films, adhesive layers and drying channels. The occurrence of the second phenomenon is directly related to the thickness of the inner film and the control of tension and temperature in the composite processing process. Special subsidies will be given to key coal enterprises for transformation and upgrading projects such as independent innovation, technological transformation, energy conservation and emission reduction in non coal industries. Generally, when three-layer aluminized composite film is compounded, it is better to directly compound the third layer after the second layer is compounded

II. Most of the ink layers are delaminated

after the composite products are matured, most of the ink layers are transferred to the aluminized surface, resulting in poor peel strength. This phenomenon mostly occurs on pet printing film, and the probability of occurrence on OPP printing film is relatively small. The influencing factors are as follows:

1. This phenomenon of OPP printing film is mostly related to the polyamide type ink used. As long as the chlorinated polypropylene ink is used, this phenomenon will be solved; In addition, poor surface treatment of OPP will also lead to this phenomenon

2. There are three factors affecting the situation of pet printing film:

a. it has a certain relationship with the chlorinated polypropylene ink used. The solution is to change the ink with a large amount of ink to the ink dedicated to polyester and nylon, and continue to use the chlorinated polypropylene ink with a small amount of ink

b, it is related to the influence of residual solvent. As long as the residual solvent is reduced, the transfer phenomenon will be reduced

c. it is related to the quality of PET film products. The surface treatment of some PET films is very good. One side can reach 45 dyne, and the printing surface can reach 50 dyne. The surface quality is very good. If polyester and nylon special inks are selected, the printing fastness of the printing surface is not as good as that of the printing surface at 45 dyne. After compounding, the printing surface will be transferred on the printing surface, but the printing surface on the reverse side will not. The main reason is that the film manufacturers pursue the surface treatment degree of the film too much. In the production and treatment of the film, the corona treatment of the film is too much, which has a destructive effect on the film surface

III. the peeling strength of aluminum coated composite products is poor.

the peeling strength of aluminum coated composite products is poor. Most of the existing phenomena are opp//vmcpp and opp//vmpet. The newly compounded products have good initial peeling, but the peeling strength decreases after aging, which cannot meet the standard requirements. This phenomenon can be directly detected during bag making. Specifically, there is no "migration" of the aluminum coating, and the printing ink has not been pulled down. There are two factors influencing this phenomenon:

1. The influence of ink mainly uses polyamide ink modified by surface printing, which has poor compatibility with polyurethane glue (poor binding fastness)

2. It is related to the quality of the aluminized film itself, and the poor quality of the aluminized film is prone to such quality problems

however, another kind of separation phenomenon, which seldom occurs but is often ignored, tends to lose a lot once it occurs. It is mainly manifested in BOPP printing//vm-pet. After composite processing, the initial adhesion of the two is quite good, and the peel strength after aging is also good, but it can be shown after one week or more days. This phenomenon also means that the aluminized layer has not "migrated" and the printing ink has not been pulled down, but the loss is also serious after it occurs. The loss is even greater when the packaging bag packages the items. The main reason for this phenomenon is that the residual solvent in the ink layer destroys the bonding effect of the adhesive. The specific analysis is as follows:

1. The apparent analysis of the separated products shows that the separated phenomenon occurs in the parts with thick ink layer, which is not obvious in the places with thin ink layer, and the single white ink printing place does not separate

II. The ink (color ink) diluent formula used by the manufacturer is equipped with isopropanol and butanol. Most of the inks formulated with this kind of solvent are polyamide modified composite inks. The alcohol solvent is the real solvent. These two kinds of alcohols are very easy to remain, and the alcohol has a certain destructive effect on the adhesive. White ink is mostly chlorinated polypropylene compound ink, which does not exist

III. The phenomenon is not obvious because the amount of ink is small and the residual solvent is relatively small in the light colored parts

IV. The adhesives used are usually some polyurethane adhesives with strong rigidity or fast curing polyurethane adhesives. The products are rigid and brittle. When there are many residual solvents, the damage effect to the adhesive is the best. However, the special adhesive for aluminizing film still retains certain viscosity after curing, the molecular chain is relatively soft, and the residual solvent is more, which does not have a great impact on it

v. this phenomenon often occurs when the ambient temperature is high and the humidity is high, and the residual solvent is relatively retained

through analysis, this phenomenon is often related to ink, adhesive and environmental factors. Therefore, chlorinated polypropylene composite ink is used as much as possible in the selection of ink, and modified polyamide composite ink is not recommended. Try not to print when the environment humidity is high. When selecting adhesives, try to use softer adhesives or special adhesives for aluminum plating film. In addition, the amount of curing agent can be appropriately reduced. As long as the above points are achieved, this phenomenon will be avoided. In actual production, there are many ways to solve the problem of poor peel strength. First of all, the quality of the selected composite substrate and the quality of the dilution solvent should be guaranteed. Second, the appropriate adhesive and printing ink should be selected. Secondly, the production process conditions, such as the temperature and air volume of the drying channel, the tension adjustment, the temperature and pressure of the compound roll, and so on, must also be paid attention to

Author: Xiao Haiyi

from: Zhejiang New Oriental ink Group Co., Ltd

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