Peeling causes and treatment of the hottest alumin

2022-07-29
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The main purpose of the vacuum aluminized film is to replace the pure aluminum foil composite, so that the soft packaging printing materials have elegant silver white gloss, and reduce the packaging and printing cost while improving the barrier and shading of the soft packaging film bag (the aluminized film is only 0.4-0.61 μ m. Only about 1/150 of pure aluminum foil is used

there are two common vacuum aluminizing methods: one is vacuum aluminizing after printing, that is, reverse internal printing is carried out on the surface of the film, then aluminizing, and compounding with the bottom film; Second, after printing directly on the surface of the film, it is dry compounded with the vacuum aluminized bottom film. However, CPP, PE and other materials with good heat resistance and capable of heat sealing sample parameters and preset parameters and results must be selected for the bottom film of this method. No matter what method is used, the composite packaging and printing products will not peel or degumm

with the continuous expansion of packaging and printing products, the requirements for packaging and printing quality and delivery time are also constantly improving, while the selling price is gradually falling. For packaging and printing enterprises, on the premise of on-time delivery, they can choose low-cost raw materials as the top priority. For example, when using ink and glue, we prefer to buy low price auxiliary materials instead of unprofitable auxiliary materials. Therefore, few people went to the early days of the founding of the people's Republic of China to check and accept the purchase channels, which obviously led to the inferior, glue separation and skin separation of the packaging and printing products with aluminum coated film. Around these problems, the author introduces the causes and treatment methods of the following faults on the composite packaging products

pet film, printing ink, vacuum aluminizing, gluing and PE (as the heat sealing back film material) are compounded. As a result, after the color ink is printed, the last full version of white ink (or yellow ink) is bonded to the adhesive, resulting in the separation (peeling) of pet and the bottom film. Another situation is that the printing ink has a thin film of graphic ink, which has good adhesion fastness after compounding with PE at the bottom, while the thick film of ink has poor adhesion (poor). For these faults, the former involves low softening point (heat resistance) of the ink and too good affinity (miscibility) with the adhesive, so the composite PET film is easy to be torn off; The latter is due to the high cotton content of the ink system or the increase of the surface dispersant and waxy additives, which are mutually exclusive when compounding with PE film and have poor adhesion fastness, resulting in the product being very easy to tear

in the normal packaging and printing process, in order to save ink expenses, people often use surface printing intaglio inks (such as polyamide inks, acrylic inks, nitro inks, oxyacetate resin inks, etc.) with lower prices. Almost all of them can be used as surface printing inks for dry compounding of polyurethane adhesive. While the white ink uses the internal printing ink, some use the surface printing ink or the color printing ink, while the white ink uses the surface printing oiler

no matter what kind of ink is used for printing, some inks must be prevented from repelling the composite glue, and the selected ink must have a certain degree of compatibility with the composite glue. For example, polyamide ink, if white polyamide ink is used as the printing ink to print the background color, as long as there is a certain adhesion with the composite ink or composite adhesive layer, the above failure will not occur. However, most surface printing inks have no affinity with composite ink or composite adhesive layer, so it is difficult to produce adhesion. Therefore, this kind of ink will be separated from the (reverse printing) graphic ink film of the composite color ink. In addition, in the production of white ink, the amount of colorant titanium dioxide or a small amount of calcium powder in the system is mostly between 20-33%, while the amount of colorant for color ink is 8-12%. If the same amount of resin binder is used, the adhesion of color ink will be greatly reduced. For this reason, when using white ink, you should choose one with high content of resin binder or one with surface active additives, so as to have the same adhesion fastness as color ink

the above has introduced the packaging and printing method of aluminized film and the principle of selecting ink and bonding compound. However, this does not mean that only the white ink with high content of resin binder can have sufficient composite adhesion fastness. The factors that affect the adhesion strength of the white ink include the surfactant dispersant in the ink system, the anti sedimentation and friction waxy materials, and the static electricity of the ink itself

first, once the glue is coated on the surface of the white bottom ink film containing surfactant dispersant or anti sedimentation and friction resistant wax additives, the two objects repel each other or the wax with almost no tension will make the glue layer on the surface of the substrate form uniform dots, resulting in low-quality packaging printing products with poor composite fastness or low composite strength

secondly, due to the use of packaging printing ink with low softening point, the ink is very easy to be pulled by glue with high softening point or too good mutual solubility (solubility) in the high temperature environment during aluminum plating or compounding, resulting in peeling failure

thirdly, as the content of film-forming hard resin in the surface printing ink system reaches a certain amount (such as nitrocellulose auxiliary resin in polyamide ink system), the graphic ink film that packs the printing ink often loses a certain flexibility. As a result, the thin part of the ink film is well attached, while the thick part of the ink film is poor in adhesion fastness

fourth, the poor adhesion fastness of ink and glue is also caused by the excessive solvent residue in the ink system or glue system. And lead to ink and substrate adhesion is poor substrate surface sheet 8 The cement consistency tester is weak, or the volatile gradient of the ink system solvent is unbalanced, or the ink viscosity is too small (the resin content is too small). As for the lack of adhesion between the coated glue and the composite bottom film after printing, it is caused by the poor treatment of the substrate or the large difference between the hydrogen bond value of the glue and the hydrogen bond value of the substrate

to cause market panic, the general methods to deal with the above failures are: handle the substrate; Replace the glue again; Select the ink that has affinity with glue; Change to ink with high resin content or viscosity; Use ink that can resist certain temperature (heat); Select printing ink without surfactant or wax; Gravure printing is replaced by a printing plate with shallow holes; Change the glue with high viscosity or large coating amount; Control the aluminum plating, drying channel and composite temperature: increase the printing pressure or the pressure between composite pressing rollers

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