Analysis of the Operational Points of Aluminum Foil Printing for Pharmaceutical Packaging

At present, the use of blister packs for pharmaceutical tablets and capsule packaging is becoming more and more common. Pharmaceutical blister packaging, also known as PTP (Press Through Packaging), is based on industrial pure aluminum foil as the substrate, in the pharmaceutical PTP aluminum foil coating machine, using gravure printing technology and roller coating method to print text patterns on the surface of aluminum foil, Coated with a protective layer and coated with adhesive layer on the other side of the aluminum foil. The brief process flow is: aluminum foil unwinding? Gravure printing? dry? Coating protection? dry? Coated layer? dry? 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. 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 thickness, tensile strength is 98 kPa, and burst strength is 90kPa. The surface is clean, smooth, wrinkle-free, no indentation damage, and no fluorescent material. The surface wetting tension is not less than 32. The requirement for the pinhole degree of the medicinal aluminum foil is that the pinholes with a diameter of 0.1-0.3mm 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-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 20-30 s. 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.

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 process

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 surface discoloration. The general drying temperature is controlled at 170 ~ 210 °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 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. Generally, the thickness of the coating should be controlled at 3.5 to 7.0um. 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.
The speed of the printing machine, the temperature in the drying tunnel, and the tension of the equipment during the printing and coating of the aluminum foil cause the cause of the product quality problem to be analyzed in the following table:

Quality Analysis of Printing and Coating Quality Problems

Printing and coating Cohesive layer thickness uneven, inconsistent depth and speed Inconsistent speed and tension control inconsistent printing, adhesive layer, protective layer appear dry in the surface dry speed too fast, low drying temperature material thermal deformation is too large, discoloration, wrinkle machine speed Too slow, high drying temperature around the left and right deviation, wrinkles, tear tension is too large, speed is slow