Key points of production process quality of alumin

2022-08-12
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Key words: pharmaceutical packaging PTP aluminum foil intaglio printing

at present, blister packaging is more and more common for pharmaceutical tablets and capsules. Blister packaging of drugs, also known as PTP (press through packaging), uses gravure printing technology to print text patterns on the surface of aluminum foil, and coating protective layer, and coating adhesive layer on the other side of aluminum foil. The brief process flow is: aluminum foil unwinding → gravure printing → drying → coating protective layer → drying → coating adhesive layer → drying → aluminum foil winding

in the national standard aluminum foil for pharmaceutical packaging, there are clear requirements for the surface quality of printed words of pharmaceutical aluminum foil, and there are physical and chemical indicators for the performance of protective layer and adhesive layer, so that the pharmaceutical PTP aluminum foil has good barrier property, health safety, heat sealing property and good physical and mechanical properties. In order to meet the above requirements in the production process of PTP aluminum foil printing and coating, it is necessary to be familiar with the properties of the applied raw materials, and pay attention to the following problems in the operation process

1. Grasp 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 required to be 0.02mm, the tensile strength is 98mpa, the rupture strength is 90kpa, the surface is clean and flat, without wrinkles, indentation damage, no flake fluorescent substances, and the surface wetting tension is not less than 32. The requirement for the pinhole of medicinal aluminum foil is that the pinhole with a diameter of 0.1 ~ 0.3mm is not more than 1/m2. Because pinholes in aluminum foil are penetrating defects, drugs will reduce or deteriorate due to the invasion of oxygen, water vapor and light, so the requirements for pinholes are very strict. In addition, if the thickness of aluminum foil exceeds the required deviation (10%), it will affect the coating amount of adhesive layer and protective layer, which should be paid attention to by the operator

at present, the printing inks used for aluminum foil are mainly divided into two categories: one is polyamide inks, which are mostly used for the printing of plastic films, and their heat resistance meets the requirements of aluminum foil printing. The other is the special ink for aluminum foil, which is mainly composed of vinyl chloride vinyl acetate copolymer synthetic resin/acrylic resin. It is characterized by bright color, high concentration, strong adhesion to aluminum foil and good transparency. However, due to its high solvent volatility, it is easy to cause ink drying and deposition in the ink hole of intaglio roll when printing on the surface of PTP aluminum foil, resulting in paste phenomenon. Therefore, it is necessary to carry out necessary pretreatment for the deposition and freezing of the ink. The method is to stir the deposition and freezing of the ink or heat it in a water bath. If the storage time of the ink is too long, the ink will deposit, resulting in more resin solution in the upper layer, more pigments in the lower layer, light color in the upper layer and deep color in the lower layer. It should also be mixed evenly before use

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

when the ink with high viscosity is diluted with diluent, it should be stirred while adding diluent to make the diluent evenly distributed in the whole ink, and it should be measured between 20 ~ 30p by viscometer. The ink concentration detector is used to determine the amount of solvent added, and the ink concentration is measured at regular intervals according to the changes of temperature and humidity. When using intaglio printing to print aluminum foil products, the ink concentration is too low, which will cause the color of printed words and patterns to be not bright, and the paste phenomenon will occur at the graphics and texts; If the ink concentration is too high, the image and text will be cracked, which not only wastes ink, but also easily causes the uneven and unsightly surface of the plate brush. In addition, the best ink concentration should also be determined according to the speed of the aluminum foil printing coater and the inking hole depth of the printing gravure roller

3. The adhesive shall 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 can be firmly pressed, so that the drugs in the plastic hard sheet Blister are separated from the outside, so as to achieve the purpose of sealing the drugs. In the process of loading drugs for heat sealing, the adhesive layer is activated by heating and firmly bonded with PVC plastic hard pieces. This requires that the adhesive layer and PVC resin should have good heat sensitivity and compatibility with the substrate

4. In the process of printing and coating, we should master the drying temperature and time. 1. The rubber pulling machine must be installed in a clean, dry and non corrosive place. Time

the printed graphics and text, as well as the adhesive layer and protective layer, need to be dried in the coating process. There needs to be a process for the drying of the coating on the surface of aluminum foil, so it needs to stay in the drying channel of the equipment for a certain time, which depends on the winding speed of the coating machine and the temperature selected in the drying channel, The two should maintain a corresponding relationship. Due to the different thickness of aluminum foil materials, there are differences in physical and mechanical properties, and there are certain differences in the thermal expansion, contraction and elongation of materials when they are running in the equipment, so they should not stay at a very high temperature for too long, otherwise the aluminum foil is also prone to wrinkling and surface discoloration. Generally, the temperature of drying channel should be controlled at 170 ℃ ~ 210 ℃

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

the coating thickness of the bonding layer in the process of printing and coating has a great influence on the bonding fastness of plastic PVC hard films. If the bonding layer is too thin, the bonding fastness will be reduced due to lack of material when hot pressing PVC hard films; If the adhesive layer is coated too thick, it will not only increase the cost, but also prolong the drying time, so it needs to be controlled within the 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 roll lines. When the shape, depth, number of lines of the coating roll and the pressure of the contact line between the two rolls are set, the greater the adhesive 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 adhesive and the tension of the coater. Different kinds of aluminum foil have different requirements for the thickness of the bonding layer. Generally, the coating thickness should be controlled within 3.5 ~ 7.0um. In the printing and coating of aluminum foil, the machine speed, temperature and tension are not only related to each other, but also contain each other. The cooperation between them is directly related to the printing and coating quality of aluminum foil

the cause analysis of product quality problems caused by changes in the machine speed of the printing machine, the temperature in the drying channel and the tension of the equipment during the printing and coating of aluminum foil is shown in the table below

quality cause analysis of printing and coating quality problems ① uneven thickness and depth of printing and coating adhesive layer, inconsistent changes in machine speed and tension control ② printing, adhesive layer and protective layer appear surface drying, internal drying, too slow machine speed, low drying temperature, special alloy for high-end equipment ③ material thermal deformation is too large, discoloration, wrinkle machine speed is too fast, and drying temperature is low ④ left and right deviation, wrinkling, tearing tension is too large The machine speed is slow (baibingshan our Jinan experimental machine factory has good product quality, many customers, and the level of service naturally has to keep up with the East Pharmaceutical Packaging Research Institute)

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