The brief process flow is: aluminum foil unwinding â†’ gravure printing â†’ drying â†’ coating protective layer â†’ drying â†’ coating adhesive layer â†’ drying â†’ 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 the process operations. Need to strictly grasp. Therefore, in the "Aluminum Foil for Pharmaceutical Packaging" national standard, there is a clear requirement for the surface quality of printed aluminum foil for medicinal use, and there are physical and chemical indicators for the performance of the protective layer and the adhesive layer, so as to protect the medicinal PTP aluminum foil with good barrier properties. , Hygiene safety, heat sealability and good physical and mechanical properties. To achieve the above-mentioned requirements in the PTP aluminum foil printing and coating production process, it is still necessary to be familiar with the applied raw material properties, and the following issues should be noted in the operation process:
1. Master 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 rupture strength. The surface is clean, smooth, no wrinkles, no indentation damage, and no fluorescent material. The surface wetting tension is not less than 32. The requirement for the pinhole degree of medicinal aluminum foil is that the pinholes with a diameter of 0.1-0.3 mm are not more than 1/m2. Since the pinhole in aluminum foil is a penetrating defect, the penetration of oxygen, water vapor, and light by medicines will reduce or deteriorate the efficacy of the drug. Therefore, the requirements for pinhole degree are very strict; in addition, if the thickness of aluminum foil exceeds the required deviation ( When 10%), the coating amount of the adhesive layer and the protective layer is affected, and the operator's attention needs to be paid.
Printing inks for aluminum foils are currently mainly divided into two categories: one is polyamide inks. This type of ink has good adhesion, dispersibility, gloss, abrasion resistance, good solvent release, and softness for printing on various types of materials, and is often used for the printing of 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 based on vinyl chloride vinyl acetate copolymer resin / acrylic resin as the main ingredient of aluminum foil ink, its holding point is bright color, high concentration, and aluminum foil adhesion is particularly strong, with good transparency, but Because it is used for gravure printing, the volatility of the solvent is large, and it is easy to cause the ink of the gravure roll ink to dry and deposit in the intaglio printing ink foil when it is used for printing the medicinal PTP aluminum foil, resulting in stencil printing 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.
2. The amount of solvent added to the ink should be appropriate
When a large-viscosity 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 is selected based on the speed of the aluminum foil coater and the depth of the ink in the gravure roll.
3. 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.
4. Drying temperature and time should be mastered during printing and coating
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 coating machine rolling up. The relationship between 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 surface discoloration. Drying temperature is generally 170-210 Â°C.
5. Printing and coating speed, coating tension, coating thickness and adhesive quality
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 dry operation time. Therefore, it must be controlled within a proper thickness range. The coating thickness of the adhesive layer is affected by the binder concentration, coating tension, coating speed, and the number of anilox roller lines. In the case of the shape, depth, number of lines per inch, and line pressure setting between the rollers, the greater the adhesive concentration, the lower the coating tension, and the faster the coating speed, the thicker the coating. . 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. Generally, the thickness of the coating should be controlled within 3.5-7.0mm. 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.
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