Aluminum foil ink application characteristics

With the development of the market and the improvement of the economic level, the higher the people's demand for product packaging and decoration, the more colorful the product packaging. More and more beer packaging using aluminum foil bottle sealing and thin aluminum foil bottleneck labels, such as Zhujiang Beer, Blue Ribbon Beer, Tsingtao Beer, Shengli Beer, Kingway Beer, Draft Beer and so on. With so many aluminum foil bottle-sealing and thin aluminum foil bottleneck labels, it is inevitably necessary to have special inks for aluminum foil package printing, so that gravure aluminum foil ink came into being.

The gravure aluminum foil ink has good printability, easy operation, bright colors, high gloss, good frost resistance and water resistance, and good light resistance. Moreover, after printing with this type of ink, the printed products are well-cut and the alkali-cooking performance is excellent, and can be applied to different depths and speeds. The following is a brief analysis of the characteristics of the application of this kind of aluminum foil ink from the point of view of ink design and production, for reference by the printing manufacturer when using this type of ink.

First, the classification of aluminum foil ink

The binders used in aluminum foil inks are typically nitrocellulose and polyamide resins, so aluminum foil inks can be divided into nitrocellulose systems and polyamide systems.

The nitrocellulose system ink film is hard and brittle, drying fast, easy to absorb water. However, the ink is stable, the storage time is long, and the printability is good. Because the ink film is hard and its adhesion to the aluminum foil is poor, sometimes the polyamide resin is added to reduce its hardness, increase the flexibility, and improve the attachment fastness.

Polyamide system is contrary to nitrocellulose system, ink film is soft and sticky, drying speed is slow, and water resistance is better than nitrocellulose system. However, a single polyamide resin cannot make its application on aluminum foil perfect, but also need to add some phthalate ester plasticizer in the ink formulation to improve the toughness of the ink film, but the added amount should be controlled well. Otherwise, sticking will occur.

In fact, the nitrocellulose system and the polyamide system of aluminum foil ink each have their own strengths and shortcomings. In the process of doing the ink, the components of the two systems will be properly matched to each other, and the advantages and disadvantages of the inks will be taken into account in order to facilitate the printing of the ink.

Second, the vividness of aluminum foil ink

To improve the vividness of the color of aluminum foil ink prints, it is necessary to first print the ink and then apply a layer of varnish. However, doing so will increase the printing cost, unless a special printer is required to do so. Another method is to print color ink on the glossy side of the aluminum foil. This requires the surface treatment of the aluminum foil to be high and requires the ink to have good adhesion on the aluminum foil. What is more, a transparent type ink using a dye powder as a coloring material has excellent vividness and transparency.

Third, the aluminum foil ink cutting

Pure aluminum foil is relatively brittle and its flexibility is not enough. It is usually printed with a varnish or aluminum foil ink, which can improve the flexibility of the aluminum foil and improve the cutting effect. Under normal circumstances, after the ink is printed, the ink can not be printed, and the cutting requirements can also be achieved. That is, by separately printing the varnish or ink, the cutting requirements can be achieved. The fact that the print surface is too hard or soft is not conducive to slitting, and that the print surface is too slippery or blunt is not conducive to slitting. Usually by adjusting the content of nitrocellulose inside aluminum foil ink to meet the requirements, the number of seconds of nitrocotton is directly proportional to the hardness. If a single nitrocellulose cannot meet the requirements, two types of nitrocellulose can be used to meet the requirements. The smoothness of the surface can be adjusted with wax powder to meet the requirements. Usually also add some leveling additives to improve the printing effect, prevent orange peel, smooth ink layer to facilitate cutting. One thing to note is that the leveling agent should not be added too much, because some leveling aids have a counteracting effect of extinction, which will affect the brightness and adhesion of aluminum foil ink prints.

Fourth, aluminum foil ink freeze resistance and water resistance

The aluminum foil sealer and thin aluminum foil bottleneck labels are often used as beer labels. In the summer, the beer is generally frozen in the refrigerator and has water droplets on the surface. Therefore, aluminum foil inks generally require frost resistance and water resistance. An ink ink layer made of a polyamide resin having a lower softening point has a better low-temperature resistance, and an increase in the amount of the polyamide resin used in the production of the ink formulation or the ink distribution may increase the frost resistance; while using oleic acid amide or wax Powder can improve water resistance.

Fifth, the printability of aluminum foil ink

When printing, adjust the pressure and temperature of the printer before starting printing. When printing on the machine, it is necessary to adjust the viscosity of the aluminum foil ink with the relevant solvent first: the viscosity of the ink at the high speed printing should be lower, and more solvent should be added; the viscosity of the ink at the low speed printing should be higher, and less solvent should be added. The ink fountain should be often stirred to evenly ink, and the proper solvent should also be frequently added to make up for the volatilized solvent so that the viscosity of the ink can be kept constant. Preferably, there is a circulating ink pump. Alcohol-soluble inks are more likely to foam during the printing process, which is caused by the greater surface tension of alcohol-soluble solvents, and the addition of defoamers can often act as a defoamer.

Some prints stick together when they are put down, or the ink layer separates and sticks to the back of another layer of prints. This is adhesion because the surface of the ink layer is dry when it is dry and there is solvent residue inside. Re-dissolves the ink layer in a humid environment. To solve this problem, one way is to add acid amide and wax powder to resist adhesion; another is to dilute the ink with a special quick-drying solvent (such as 12 gasoline, isopropyl alcohol, toluene, ethyl ester, butanone, etc.) ), to reduce the occurrence of ink film false dry; or else to change the resin to improve the ink solvent release and dryness.

Six, aluminum foil ink printing case analysis

There were complaints from customers that when our aluminum foil ink was used to print external packaging foils for packaging chocolates, we found that our ink prints were easily discolored. The reasons for the analysis are: chocolate is a substance containing a cream component, and butter is also a type of oil and fat. The polyamide resin and other ingredients used in our ink binders are easily soluble in oils and fats, so when the ink film comes into contact with chocolate, Will be dissolved away. In order to prevent the contact between chocolate and ink, a layer of varnish (alcohol soluble) is printed after the color ink is printed, so that the contact between the chocolate and the ink can be avoided, and the problem of easy fading of the external packaging aluminum foil film printing product can be prevented.

After receiving customer feedback, our aluminum foil was whitened when printing a spot color ink. The on-site analysis showed that the printing conditions were as follows: 1 The printing speed was about 15m/min; 2 The dilution solvent used was: Propyl alcohol: butyl ester: 6:4, which is a medium dry solvent; 3 The heating equipment temperature is 35°C. Analysis of reason: Because of its slower printing speed, the diluent solvent used is a relatively quick-drying type, because the speed is slow, the solvent volatilizes quickly, the heat is not heated in time, and the printed product easily absorbs water and whitens. Recommendation: Because the speed of the printing press cannot be changed, ie, the speed is about 15m/min; 1 Dilution solvent is changed to slow drying, it is recommended to use: xylene: butanol: butyl ester 5:2:3; 2 heating equipment The temperature is increased to about 50°C. According to the above method, the printing effect is significantly better

Reprinted from: Packaging Expo