Aluminum Foil Packaging Process And Problem Solution

- May 13, 2019-

The aluminum foil packaging bag may not be well understood by everyone. Simply put, a layer of aluminum foil is plated on it, so the aluminum foil bag generally has a silver appearance, or the inside of the bag is silver, and the aluminum foil is isolated and quite superior to other materials. So it will take longer to save the item. Next, I will introduce the process flow of the aluminum foil bag and some problems that need attention:


The process of packaging aluminum foil is: aluminum foil unwinding → gravure printing → drying → coating protective layer → drying → coating adhesive layer → drying → aluminum foil winding. In the whole production process, the surface quality of the gravure printed character 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 in the process operation. Need to be strictly controlled. Therefore, in the "Aluminum Foil for Pharmaceutical Packaging" national standard, there is a clear requirement for the surface quality of medicinal aluminum foil printed characters, and physical and chemical properties for the properties of the protective layer and the adhesive layer, thereby protecting the medicinal PTP aluminum foil from having good barrier properties. , hygienic safety, heat sealability and good physical and mechanical properties. In order to achieve the above requirements in the PTP aluminum foil printing and coating production process, it is necessary to be familiar with the properties of the applied raw materials, and pay attention to the following problems during the operation:


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1. Master the characteristics of aluminum foil and printing ink


The raw material used for the production of PTP aluminum foil is industrial pure aluminum foil. Generally, the thickness is 0.02mm, the tensile strength is 98kPa, the bursting strength is 90kPa, the surface is clean, flat, no wrinkles, no indentation damage, no flakes, no surface. The wetting tension is not less than 32. The requirement for the pinhole of the medicinal aluminum foil is that the pinhole having a diameter of 0.1-0.3 mm is not more than 1/m2. Since the pinhole in the aluminum foil is a penetrating defect, the drug is degraded or deteriorated by the intrusion of oxygen, water vapor and light, so the requirement for the pinhole is very strict; in addition, if the thickness of the aluminum foil exceeds the required deviation ( When it is 10%), it will affect the coating amount of the adhesive layer and the protective layer, and it is necessary to attract the attention of the operator.


Printing inks for aluminum foil are currently mainly divided into two categories: one is a polyamide ink. This kind of ink has good adhesion, dispersibility, gloss, abrasion resistance, solvent release, softness and is used for the printing of plastic film. When used for printing aluminum foil materials, the excellent properties of the inks can be expressed, and the heat resistance can also meet the requirements of aluminum foil printing. The other type is a special ink for aluminum foil containing vinyl chloride vinyl acetate copolymerized synthetic resin/acrylic resin as the main component. Its holding point is bright color, high concentration, strong adhesion to aluminum foil, good transparency, but due to In the gravure printing, the solvent volatility is large, and it is easy to cause the ink to dry and deposit in the inking hole of the gravure roll when the medicinal PTP aluminum foil is printed, and the paste phenomenon occurs. Therefore, it is necessary to perform necessary pretreatment of the deposition and freezing of the ink by stirring or increasing the temperature (water bath) of the deposited frozen ink. If the storage time of the ink is too long, the ink will deposit, resulting in more resin in the upper layer of the ink, more pigment in the lower layer, lighter color in the upper layer, and darker color in the lower layer. It should also be stirred and used.


 


2. The amount of solvent added to the ink should be appropriate


When a high viscosity ink needs to be diluted with a large amount of diluent, it should be stirred while adding a diluent to evenly distribute the diluent throughout the ink. The meter is measured between about 20-30s. Indoor temperature and humidity have an effect on the ink concentration. It is best to use an ink concentration detector to determine the amount of solvent added, and to determine the ink concentration at regular intervals based on changes in temperature and humidity. When the aluminum foil product is printed by gravure printing, the ink concentration is too low, which will cause the printed text pattern to be not bright and the paste is generated at the web; if the ink concentration is too high, cracks will occur at the pattern, which not only wastes ink, but also It is easy to cause the printing surface to be uneven and not beautiful. In addition to this, the optimum ink is selected according to the speed of the aluminum foil printing coater and the depth of the ink mark of the printing gravure roll.


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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 sheet firmly heat-pressed, so that the medicine in the plastic hard sheet blister is separated from the outside to achieve the sealing of the medicine. purpose. During the heat sealing process of loading the drug, the adhesive layer is activated by the hot pressing action, thereby firmly bonding with the PVC plastic hard piece, which requires the adhesive layer and the PVC resin to have good heat sensitivity and the substrate. Compatibility.


 


4. Dry temperature and time should be mastered during printing and coating


The printed image 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 drying tunnel of the equipment for a certain period of time, which depends on the coating machine winding. The speed and the temperature selected in the drying tunnel should be related to each other. Due to the different thickness of the aluminum foil material, the physical and mechanical properties are different, and the thermal expansion, shrinkage and elongation of the material during operation are also different, so the residence time should not be too long at a very high temperature, otherwise the aluminum foil It is also prone to wrinkles and surface discoloration. Generally, the temperature of the drying tunnel is controlled at 170-210 °C.


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5. Analysis of printing coating speed, coating tension and coating thickness and bonding quality


The coating thickness of the adhesive layer during the printing and coating process has a great influence on the adhesion strength of the plastic PVC rigid sheet, and the adhesive layer is too thin. When the PVC hard sheet is hot-pressed, the adhesion fastness is reduced due to lack of material; The coating is too thick, which not only increases the cost, but also requires a long drying time, 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, the coating tension, the coating speed, and the number of anilox rolls. In the case of the shape, depth, number of lines per inch, and the line pressure between the two rolls, the greater the binder concentration, the smaller 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 binder and the tension of the coater. Different types of aluminum foil have different requirements on the thickness of the adhesive layer. Generally, the thickness of the coating should be controlled at 3.5-7.0 mm. In the aluminum foil printing and coating, the speed, temperature and tension are related to each other and are mutually restrained. The good cooperation between them is directly related to the printing quality of the aluminum foil.


Dongguan Bite Packaging Materials Co., Ltd. is a large-scale company specializing in the production of food-grade composite packaging. It is a professional composite packaging bag manufacturer that uses new equipment to produce packaging bags and film rolls to provide comprehensive, environmentally friendly and safe packaging services for the market. The company produces composite bags, film, fruit bags, aluminum foil bags, nozzle bags, stand-up bags, zipper bags, anti-static bags, shaped bags, etc., suitable for food, daily chemicals, electronics, toys, medicine, cosmetics, industrial products, etc. Internal and external packaging for various industries. We adhere to the business philosophy of good faith cooperation, high quality and considerate service, and have been recognized by the industry. Our products are sold all over the world. Welcome friends from all walks of life to inquire, visit our factory for inspection and business negotiation.