The process flow of packaging aluminum foil is: aluminum foil unwinding -> gravure printing -> drying -> protective layer coating -> drying -> adhesive layer coating -> drying -> aluminum foil winding. In order to achieve the above-mentioned performance requirements in the PTP aluminum foil printing and coating production process, it is still necessary to be familiar with the properties of the raw materials used, and the following issues should be paid attention to during the operation:
1. Master the characteristics of aluminum foil and printing ink
The raw material used in the production of PTP aluminum foil is industrial pure aluminum foil. Generally, the thickness is 0.02mm, the tensile strength is 98kPa, and the bursting strength is 90kPa. The surface is clean and flat, without wrinkles, and no indentation damage, without flakes of fluorescent material. The wetting tension is not less than 32. The requirement for pinhole degree of medicinal aluminum foil is no more than 1 pinhole/m2 with a diameter of 0.1-0.3mm. Because the pinholes in the aluminum foil are penetrating defects, the drug will be reduced or deteriorated by the intrusion of oxygen, water vapor and light, so the requirements for the pinhole degree are very strict; in addition, if the thickness of the aluminum foil exceeds the required deviation ( 10%), it will affect the coating amount of the adhesive layer and the protective layer, which requires the attention of the operator.
Printing inks for aluminum foil are currently mainly divided into two categories: one is polyamide inks. This kind of ink has good adhesion, dispersibility, gloss, abrasion resistance, solvent release, softness, and is mostly used for printing on plastic films. When used in the printing of aluminum foil materials, the excellent performance of this ink can be shown, and its heat resistance can also meet the requirements of aluminum foil printing. The other type of special ink for aluminum foil is based on the copolymerization of vinyl chloride vinyl acetate into resin/acrylic resin. Its holding point is bright color, high concentration, strong adhesion to aluminum foil, and good transparency. When used in gravure printing, the solvent has high volatility. When used for the surface printing of medical PTP aluminum foil, it is easy to cause the ink to dry up and deposit in the ink hole of the gravure roller, resulting in a paste phenomenon. Therefore, it is necessary to carry out the necessary pretreatment for the deposition of freezing ink, the method is to stir or increase the temperature (water bath) of the deposited freezing ink. If the storage time of the ink is too long, the ink will be deposited, resulting in more resin solution in the upper layer of the ink, more pigment in the lower layer, light color in the upper layer, and dark color in the lower layer. It should also be mixed well before use.
2. The amount of solvent added to the ink should be appropriate
When the ink with high viscosity needs to be diluted with a large amount of diluent, it should be stirred while adding the diluent to make the diluent evenly distributed in the whole ink. The measurement by the meter is about 20-30s. Indoor temperature and humidity have an impact 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 using gravure printing to print aluminum foil products, if the ink concentration is too low, the color of the printed text and patterns will not be bright, and the pattern will be pasted; if the ink concentration is too high, the pattern will be cracked, which will not only waste ink, but also It is easy to cause the printing surface to be uneven and unsightly. In addition, the best ink should be selected according to the speed of the aluminum foil printing coater and the depth of the ink hole of the printing gravure roller.
3. Adhesive should meet the requirements
The adhesive of PTP aluminum foil is coated on the inner side of the aluminum foil, and its function is to make the aluminum foil and the medicinal PVC hard film can be firmly thermocompressed, so that the medicine in the plastic hard film blister can be separated from the outside, and the medicine can be sealed. purpose. In the process of filling the medicine for heat sealing, the adhesive layer is activated by heat and pressure, thereby firmly bonding with the PVC plastic hard sheet as a whole, which requires that the adhesive layer and the PVC resin should have good heat sensitivity and the substrate The compatibility.
4. The temperature and time of drying should be mastered during the printing and coating process
The printed graphics and the adhesive layer and the protective layer need to be dried during the coating process. The drying of the aluminum foil surface coating requires a process, so it needs to stay in the equipment drying tunnel for a certain period of time, depending on the winding of the coating machine The speed and the selected temperature in the drying tunnel should maintain a corresponding relationship. Due to the different thickness of the aluminum foil material, the physical and mechanical properties are different, and the thermal expansion, contraction, and elongation of the material when running in the equipment are also different. Therefore, the residence time should not be too long at a high temperature, otherwise the aluminum foil It is also prone to wrinkling and surface discoloration. Generally, the temperature of the drying tunnel should be controlled at 170-210℃.
5. Analysis of printing coating speed, coating tension, coating thickness and bonding quality
During the printing and coating process, the coating thickness of the adhesive layer has a greater impact on the firmness of the plastic PVC rigid sheet. If the adhesive layer is coated too thin, the hot-pressing of the PVC rigid sheet will reduce the bonding fastness due to lack of material; If the layer is too thick, not only will the cost increase, but the drying time will need to be lengthened, so it needs to be controlled within an appropriate thickness range. The coating thickness of the adhesive layer is affected by the concentration of the adhesive, coating tension, coating speed, and the number of anilox roll lines. When the shape, depth, number of lines per inch and the line pressure between the two rolls are adjusted, the greater the concentration of the adhesive, the smaller the coating tension, and the faster the coating speed, the thicker the coating will be. . Therefore, the thickness of the adhesive layer is generally adjusted by the concentration of the adhesive and the tension of the coating machine. 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 3.5-7.0mm. When printing and coating aluminum foil, the machine speed, temperature, and tension are both interrelated and constrained. The quality of the coordination between them is directly related to the printing and coating quality of aluminum foil.
Henan Huawei Aluminum Co., Ltd. is the leader of many aluminum manufactures and suppliers in China. We strictly control the quality and focus on customers. We hope to have in-depth cooperation with you and provide you with high quality aluminium material products custom OEM services. If you want to get the newest and best prices by per kg or per ton standard weight, please contact us.
Henan Huawei Aluminum Co., Ltd. is the leader of many aluminum manufactures and suppliers in China. We strictly control the quality and focus on customers. We hope to have in-depth cooperation with you and provide you with high quality aluminum material products custom OEM services. If you want to get the newest and best prices by per kg or per ton standard weight, please contact us.