Aluminum foil and printing ink characteristics

In the "Aluminum Foil for Pharmaceutical Packaging" national standard, there are clear requirements for the surface quality of printed texts for health foods and pharmaceutical aluminum foils, as well as physical and chemical indicators for the properties of the protective layer and the adhesive layer, so that the protection of PTP aluminum foil has better barrier properties. , Hygiene safety, heat sealability and good physical and mechanical properties. In order to achieve the standard performance in the production process of PTP aluminum foil printing and coating, it is still necessary to be familiar with the applied raw material properties, and should pay attention to some problems in the operation process.

At present, the use of blister packs for health foods and pharmaceutical tablets and capsules is becoming more and more common. The blister pack is also called PTP (Press Through Packaging). It is a pure aluminum foil for industrial use. It uses a gravure printing technique and a roller coating method to print text patterns on the surface of aluminum foil on pharmaceutical PTP aluminum foil coating machines. Protective layer, the adhesive process of coating the adhesive layer on the other side of the aluminum foil.

The brief process flow of PTP aluminum foil packaging is: aluminum foil unwinding, gravure printing, drying, coating protective layer, drying, coating adhesive layer, drying, aluminum foil winding. During the entire production process, the surface quality of the gravure printing text pattern and the heat seal strength to be achieved by the adhesive layer, the adhesion of the protective layer and the drying temperature, and the speed and tension control of the coating machine operation are needed in the process operation. Strictly grasp.

Grasp the characteristics of aluminum foil and printing ink

The raw material used to produce PTP aluminum foil is industrial pure aluminum foil. The general requirement is 0.02mm in thickness, 98kPa in tensile strength, and 90kPa in breaking strength. The surface is clean, smooth, no wrinkles, no indentation damage, and no fluorescent material in the surface. Wetting tension not less than 32. The requirements for the pinhole degree of aluminum foils for pharmaceutical and health food products are not more than one pinhole per mm2 with a diameter of 0.1-0.3 mm. Since pinholes in aluminum foils are penetrating defects, health foods and medicines are affected by oxygen, water vapor, and light, which may reduce or deteriorate the efficacy of the drug. Therefore, the requirements for pinhole degree are very strict; if the thickness of aluminum foil exceeds the requirements, A deviation of (10%) will affect the coating amount of the adhesive layer and the protective layer.

Printing inks for aluminum foils are currently mainly divided into two categories: one is polyamide inks. This kind of ink has good adhesion, dispersibility, gloss, abrasion resistance, and good solvent release, and is soft and is used for printing plastic films. When used in the printing of aluminum foil materials, the excellent performance of the ink can be expressed, and its heat resistance can also meet the requirements of aluminum foil printing. The other type is an aluminum foil ink mainly composed of vinyl chloride-vinyl acetate copolymer/synthetic resin/acrylic resin. Its characteristics are bright color, high concentration, particularly strong adhesion with aluminum foil, and good transparency, but due to its When gravure is printed, its solvent volatility is large. When used for health foods and pharmaceutical PTP aluminum foils, it is easy to cause the gravure roll ink to dry and deposit the ink in the ink hole to produce a paste plate phenomenon. Therefore, it is necessary to perform necessary pretreatment on the deposition and freezing of the ink by stirring or increasing the temperature (water bath) of the deposited and frozen ink. If the ink storage time is too long, the ink will appear to deposit, resulting in more ink on the upper resin solution, the lower layer of pigment, the upper layer of light color, the lower color, it should also be used after stirring.

The amount of solvent added to the ink should be appropriate

When a large-dense ink needs to be diluted with a large amount of diluent, it should be stirred while adding a diluent so that the diluent is evenly distributed throughout the ink. The degree of measurement is about 20-30s. Indoor temperature and humidity have an influence on the ink concentration. It is best to use an ink concentration detector to determine the amount of solvent added, and determine the ink concentration at regular intervals according to changes in temperature and humidity. When gravure printing is used to print aluminum foil products, the ink concentration is too low, which will cause the printed text pattern color to be not bright, and the graffiti will produce stencil printing; when the ink concentration is too high, cracks will appear at the map, which not only wastes ink, but also Can easily cause the printing surface to be uneven and not beautiful. In addition, the best ink should be formulated according to the speed of the aluminum foil coater and the ink hole depth of the gravure roll.

Adhesives should meet requirements

The adhesive of PTP aluminum foil is coated on the inner side of aluminum foil. Its function is to enable the aluminum foil and the medicinal PVC hard sheet to be firmly pressed together, so that the medicine in the plastic hard film blister is isolated from the outside and the medicine is sealed. purpose. In the process of loading the medicines for heat sealing, the adhesive layer is activated by the heat and pressure, so that it is firmly bonded with the PVC plastic hard sheet, which requires that the adhesive layer and the PVC resin have good heat-sensitive properties and the substrate Compatibility.

Print coating to grasp the dry temperature and time

The printed graphic and the adhesive layer and the protective layer need to be dried in the coating process. The drying of the aluminum foil surface coating needs a process, so it needs to stay in the drying tunnel of the equipment for a certain period of time, depending on the rewinding of the coating machine. Both the speed and the temperature selected in the drying tunnel should maintain a corresponding relationship. Due to the different thickness of aluminum foil material, physical and mechanical properties are all different, and the thermal expansion, contraction, and elongation of the material when running in the equipment are also somewhat different, so it should not stay too long at very high temperatures, otherwise aluminum foil It is also prone to wrinkling and discoloration. Drying temperature is generally 170 °C -210 °C.

Printing and coating speed, coating tension, coating thickness and adhesive quality analysis

The coating thickness of the adhesive layer in the process of printing and coating has a great influence on the firmness of the adhesion of the plastic PVC hard sheet, and the adhesion layer is too thin. When the PVC hard film is hot pressed, the fastness of the adhesive is reduced due to lack of material; If the layer is too thick, it will not only increase the cost but also increase the drying time. Therefore, it must be controlled within a proper thickness range. The coating thickness of the adhesive layer depends on the concentration of the binder, the coating tension, the coating speed, and the anilox roll. The number of lines. In the case of the roller roll shape, depth, number of lines per inch, and contact line pressure setting between the two rollers, the greater the adhesive concentration, the smaller the coating tension, and the faster the coating speed, the more the coating becomes. thick. Therefore, the thickness of the adhesive layer is generally adjusted by the concentration of the adhesive and the tension of the coater.

Different types of aluminum foil have different requirements for the thickness of the adhesive layer, and the general coating thickness should be controlled at 3.5-7um. In the printing and coating of aluminum foil, the speed, temperature, and tension of the aluminum foil are related to each other and pinned each other. The quality of the aluminum foil is directly related to the quality of printing and coating of the aluminum foil.

Source: Sugar and Alcohol News