Peeling Reasons and Treatment of Aluminized Composite Packaging Products

The main purpose of vacuum aluminum plating film is to replace the pure aluminum foil composite, so that the soft packaging printing material has an elegant silver-white gloss, and to improve the barrier property and light-shielding property of the flexible packaging film bag, at the same time, reduce the packaging printing cost (Aluminum-plating film only 0.4-0.61μm, which is only about 1/150 of pure aluminum foil, about 25%.

There are two typical methods of vacuum aluminum plating. One is vacuum aluminum plating after printing, that is, the first reverse printing on the surface of the film, followed by aluminum plating and composite with the bottom film; the other is directly on the film surface. After printing in India, it is dry-composited with vacuum-plated aluminum backing film. However, the base film of this method must use materials such as CPP and PE that have good heat resistance and can be heat-sealed. Regardless of the method used, the combined packaging and printing products are not peeled or degummed.

With the continuous expansion of packaging and printing products, the requirements for package printing quality and delivery time are constantly increasing, and the selling price is gradually falling. For packaging and printing companies, on the premise of on-time delivery, the choice of low raw material costs is a top priority. For example, in the use of ink, glue, rather cheaper to buy, will not purchase after-use materials without profit. Therefore, almost no one to check, check the purchase channel, obviously led to the poor quality of the aluminized film packaging and printing products, from the plastic, peeling. Focusing on these issues, the author introduced the causes and treatment methods of the following faults in the composite package.

The PET film, printing ink, vacuum aluminum coating, and adhesive coating were combined with PE (as the heat-sealable bottom film material). As a result, after the color ink was printed, the full-printed white ink (or yellow ink) was completely adhered to the adhesive, resulting in PET. Separation from the base film (skinning), the other case is: the printing ink graphic ink film layer is thin, and the attachment fastness is good after being compounded with the PE of the bottom mortar, and the adhesion (bad) of the ink film layer thickness is poor. . In response to these failures, the former involves the low softening point (insufficient heat resistance) of the ink, and the affinity (miscibility) with the adhesive is too good. The composite PET film is easier to tear open; the latter is due to the ink system Cotton content

High or increased surface dispersants and wax additives, when recombined with PE film repulsion and poor adhesion, resulting in the product easily tear.

In the ordinary packaging printing process, in order to save the expense of ink, color inks often use lower-priced surface printing intaglio printing inks (such as polyamide ink, acrylic ink, nitro ink, oxalic resin ink, etc.) Polyurethane adhesive dry composite printing ink printing. The white ink is printed on the ink, but also all use the surface printing ink or the color ink used in the printing ink, and the white ink is printed using the table printer.

No matter what kind of ink printing is used during printing, some inks must be prevented from being repelled with the compound glue. Therefore, the ink must be selected to have certain compatibility with the compound glue. For example, polyamide ink, if white polyamide ink is used as the printing ink to print the background color, the above failure will not occur as long as the composite ink or composite layer has a certain adhesive force. However, most surface printing inks have no affinity with the composite ink or composite adhesive layer, and it is difficult to produce adhesive force. Therefore, this type of ink is detached from the (anti-printing) ink film layer of the composite color ink. In addition, in the production of white ink, the amount of the colorant titanium dioxide or a small amount of calcium powder in the system is mostly between 20-33%, and the amount of the color ink colorant is 8-12% if the same amount of resin is used. The binder, for color inks, the bond strength will be greatly reduced. For this reason, when the white ink is used, it should use a large amount of resin binder or a surface-active agent, so that there will be a large adhesion of the color ink.

The packaging and printing method of the aluminized film and the principle of selecting the ink and the bonding and recombination have been introduced above. However, this does not mean that only the white ink with a large content of resin binder can have sufficient adhesion fastness, and the surface active dispersant and anti-settling and friction-resistant wax in the ink system are also affected. The material and the ink itself are static and other reasons.

First, once the glue is applied on the surface of a white ink film containing surface-active dispersants or anti-settling, anti-friction wax additives, waxes that are repelled by the two materials or hardly pull will make printing possible. The glue layer on the surface forms a uniform dot, resulting in a low-quality packaging printing product with poor composite fastness or low composite strength.

Second, due to the use of packaging printing inks with a lower softening point, the ink can be easily pulled by a glue with a higher softening point or miscibility (solubility) when the aluminum plating or compounding is performed in a high temperature environment. Causes the appearance of peeling faults.

Thirdly, due to the fact that the content of the film-forming hard resin in the table printing ink system reaches a certain amount (such as the nitrocellulose auxiliary resin in the polyamide ink system), the graphic ink film packaging and printing ink often loses certain flexibility. As a result, the ink film has a good adhesion at a thin place, and the ink film has a poor adhesiveness at the place where the film is thick.

Fourthly, the reason why the adhesion of the ink and the glue is not good is that the residual amount of the solvent in the ink system or the glue system is also a cause. The poor adhesion between the ink and the substrate is caused by the small surface tension of the substrate or the unbalance of the volatilization gradient of the solvent in the ink system or the low viscosity of the ink (too little resin content). As for the adhesion of the glue after coating with the composite backing film, the substrate is not treated well or the hydrogen bond value of the glue is too different from the hydrogen value of the substrate.

The methods to deal with the above-mentioned failures are generally as follows: handling the substrate; repurposing the glue; selecting the ink with affinity for the glue; changing the ink with high resin content or high viscosity; using the ink resistant to certain temperature (heat); Printing inks containing surfactants or waxes; Gravure printing using shallow printing plates; Replacing glues with high viscosity or large amount of coating; Controlling aluminum plating, baking, compounding temperature: Increasing printing pressure or compounding Pressure between rollers.

(Liu Jiaju)