1 Question raised
In recent years, the quality of pharmaceutical PTP aluminum foil packaging has continued to improve, and the scope of applications has also continued to expand, such as food packaging, health care product packaging and other applications. However, some problems also occurred in the process of PTP aluminum foil printing and coating, and caused varying degrees of loss and adverse effects. In order to improve the quality of aluminum foil printing and its use, this article chose most users to report quality problems and summarized several common frequency of occurrence. High, big impact, and need to be solved urgently to discuss with colleagues, the purpose is to allow managers using aluminum foil packaging machinery to better deal with the quality problems arising from it.
2 The concept of medicinal aluminum foil
The metal foil used in pharmaceutical packaging is aluminum foil, which is called aluminum foil for pharmaceutical packaging (commonly known as PTP aluminum foil). PTP aluminum foil comes from English PressThrough Packaging (literally translated as: packaging by pressure). The more formal name in the industry is for pharmaceutical packaging. Aluminum foil is also called aluminum foil for blister packaging. China's term for PTP aluminum foil used in drug packaging materials and container registration certificates: PTP aluminum foil for drug packaging.
One of the main raw materials for the production of PTP aluminum foil is industrial hard pure aluminum foil.
It is used in the industry as "original aluminum foil" or original foil. When used as pharmaceutical packaging materials, aluminum foil is the only metal material in packaging materials. Aluminum foil has: (1) non-toxic and odorless; (2) excellent electrical conductivity and light-shielding properties; (3) extremely high moisture resistance, gas barrier and taste retention, which can protect the packaged objects most effectively. Therefore, it is a packaging material that has not been replaced so far. No matter what kind of vapor-deposited metal film or coated special film can completely replace aluminum foil. In the field of modern packaging and decoration, almost all composite flexible packaging materials that require opacity or high barrier use aluminum foil as the barrier layer. Because aluminum foil has both the above advantages, the characteristics of light weight, certain strength and good printability, various characters or patterns can also be printed on it. When it is made into a blister pack, it can be crushed with a little pressure during use, which is convenient for patients to take medicine and carry.
3 Common quality problems of aluminum foil printing and coating
In the process of printing aluminum foil, some quality problems often occur, and the following common defects are summarized.
3.1 The quality of aluminum foil printing does not meet the standard requirements
The common problems that the printing quality does not meet the standard requirements are: fuzzy printing, misprinting, especially overprinting aluminum foil.
3.1.1 Printing fonts are blurred
Causes: (1) The viscosity of the ink is too low; (2) The blade has corrugated deformation; (3) The angle of the blade to the plate cylinder is inappropriate; (4) The tension of the aluminum foil is not adjusted well; (5) The ink dries too slowly ; (6) The running speed is not coordinated. Control and improvement methods: According to the above problems, we should treat it specifically: (1) increase the viscosity of the ink; (2) try to level or replace the scraper as much as possible; (3) adjust the angle of the scraper and make the entire line of the scraper; (4) adjust or confirm Tension; (5) Switch to quick-drying solvents and increase the heat to increase the drying speed; (6) Confirm whether the running speed of the plate cylinder and aluminum foil are coordinated.
3.1.2 Overprinted aluminum foil fonts are misplaced
Cause: Because multiple printing plates are used for overprinting, there are many influencing factors. (1) The reason of the equipment, in the long-term production process, some main parts of the equipment are worn, such as the bending of the printing shaft, the shaft sleeve is not lubricated, and the unevenness of the traction roller will cause the misalignment of the font in the overprint; (2) the printing plate Uneven registration pressure of the rollers, uneven pressure on the left and right ends of the plate roller, loose printing rollers and other factors caused inaccurate overprinting and misaligned fonts; (3) technical problems, unbalanced unwinding and winding tension control of raw materials, Operation errors, improper blowing heat, and tension imbalance affect the misplacement of overprint fonts; (4) The mismatch of the specifications of the plate making sets (beyond the normal error range) causes the misalignment of overprint fonts; (5) The viscosity of the ink is large, which affects the inaccurate overprints and font Dislocation; (6) The performance change of aluminum foil raw materials (thickness unevenness) affects the constant tension, causing the font to be dislocated.
Solutions: (1) The equipment should establish a patrol inspection system for equipment and regularly refuel the operating system. Worn equipment parts should be replaced regularly, and a record of the replacement date should be established for easy search; (2) In the process technology, a post operation method should be established to set the opening and winding tension values ​​required for operation, as well as the temperature, air volume, and blowing time of hot air blowing And the operator will detect on time. And there are inspection records; (3) The plate-making should be in accordance with the actual samples provided by the user and compared with the actual proofing of the overprint cylinder. If it meets the requirements, the quality inspector can sign and pass the production before being put into production; The viscometer can be adjusted at any time; (5) The performance of the original aluminum foil changes greatly, so it is necessary to coordinate the change of raw materials.
3.2 The color of the ink is different
Generally, the color of the aluminum foil produced for the first time after printing will be slightly different from the reference sample, mostly due to the difference in ink raw material or substrate. If necessary, it can be confirmed by the demand side at the supplier's site, and the production and printing process must be strictly checked.
3.2.1 The color is too light
(1) Insufficient printing color density in the same batch: Causes: 1) Too much solvent in the ink; 2) Ink precipitation; 3) Intaglio engraving is too shallow. Solutions: 1) Add new ink and adjust the ink to an appropriate viscosity; 2) Stir the ink thoroughly before placing it in the ink tray, and preheat it at an appropriate temperature in winter in the north.
(2) The printing color of the same batch is too thick: the reasons: 1) the viscosity of the ink is too large; 2) the ink concentration is too large; 3) the gravure engraving is too deep or damaged. Solution: 1) Add a specified amount of solvent to the ink, adjust the ink to an appropriate viscosity; 2) Add a thinner; 3) Remake the gravure cylinder or fill the dents.
3.3 Wrinkle of printed aluminum foil
There are many reasons for wrinkles, such as wrinkles during printing, aluminum foil for raw materials, wrinkles due to improper adjustment of pharmaceutical packaging equipment, and wrinkles caused by unevenness of aluminum foil heat sealing materials. The following only analyzes the wrinkles that occur during the printing process.
The causes of wrinkles during the printing process: (1) the edge of the aluminum foil raw material is loose; (2) the central part of the raw material is loose; (3) the printing tension is not appropriate, or the substrate itself is wrinkled;
(4) The angle at which the aluminum foil is wound on the guide roller or rubber roller is too large; (5) The rubber roller is not hard enough; (6) The machine or roller and the guide roller are not properly arranged.
Solutions for wrinkles during printing: (1) Use eccentric roller shaft; (2) Use bow roller and tension adjustment roller; (3) Adjust tension appropriately; (4) Adjust aluminum foil winding angle; (5) Use high hardness Rubber roller; (6) Study the assembly position of the machine and roller.
3.4 Problems that seriously affect the quality of pharmaceutical packaging
3.4.1 The pinhole of the aluminum foil on the printed substrate exceeds the standard
According to the provisions in GB 12255-1990: "PTP aluminum foil with a pinhole diameter greater than 0.3 mm cannot be present, and a diameter of 0.1 to 0.3 mm per square meter cannot exceed one". The pinhole of PTP aluminum foil is due to penetrating defects, which affects the barrier properties of the aluminum foil (gas barrier, moisture barrier, light barrier), so that the packaged drugs are affected by oxygen, water vapor, or light to reduce the efficacy. Even the deterioration can not be used. Since water vapor transmission and oxygen transmission are important indicators of aluminum foil as a packaging material, its specified value is generally very low. At the same time, the aluminum foil itself, especially the aluminum foil with a thickness of less than 0.02 mm, is easy to wrinkle, break, and generate pinholes. Therefore, it is quite difficult to detect the water vapor transmission rate and oxygen transmission rate of pure aluminum foil, and the detection data is highly dispersed. Aluminum foil pinholes are the only factor that causes aluminum foil permeability. In general practical applications, only checking the size and number of aluminum foil pinholes can explain the problem. According to related researches: the gas permeability of pure aluminum foil is proportional to the difference in gas concentration. When the pinhole radius of the aluminum foil is greater than the thickness of the aluminum foil, it is proportional to the pinhole radius. Therefore, before the aluminum foil printing, the quality of the original aluminum foil should be inspected, especially the sample inspection of the pinhole, tear strength and tensile strength of the original aluminum foil. At present, China's aluminum foil production enterprises have reached the national standard for aluminum foil pinhole requirements and can guarantee stable quality, but some few PTP aluminum foil production enterprises often seize the market at low prices simply to reduce costs, often using some unqualified original aluminum foil, so that The pinhole is out of standard. In addition, there are many crystal points on the surface of the aluminum foil, and there are many oil stains on the surface. The original aluminum foil has a lot of wrinkles, indentations, stripes, etc. This not only affects the printing quality of characters and patterns, but also affects the coating quality of the protective agent and adhesive, which affects the packaging of medicines. Time sealing performance.
A simple way to judge the number of pinholes is to take a piece of original aluminum foil against a place with sufficient light and observe with naked eyes whether there is any pinhole light leakage. The professional testing equipment for aluminum foil pinholes is a pinhole table. A wooden box of 800 mm × 600 mm × 300 mm or an appropriate volume is used. A 30 W fluorescent lamp is installed in the wooden box. A glass plate is placed on the wooden box and the glass plate is lined with black. Paper and leave a space of 400 mm × 250 mm to check the pinhole of the sample. Take 20 samples of 400 mm × 250 mm in the finished aluminum foil, place them one by one on the pinhole inspection table, and check their pinholes in the dark. The requirements for the aluminum foil pinholes are: (1) There should be no dense, Continuous, periodic pinholes; (2) No pinholes with a diameter greater than 0.3 mm, and no more than one pinhole with a diameter of 0.1 to 0.3 mm per square meter. The pinhole of aluminum foil is a very important technical indicator for PTP aluminum foil inspection. It will be related to the sealing performance of packaged drugs, so this inspection should be highly valued.
3.4.2 Apply protective layer after printing
According to the process requirements, a layer of protective agent to protect the printed text pattern needs to be coated on the surface of the aluminum foil after printing. Of course, the protective layer also prevents the outer layer ink from contacting the inner layer adhesive when the aluminum foil is wound and causing the drug to be contaminated. It can also prevent the oxidative deterioration of the aluminum foil surface and prevent the ink layer on the aluminum foil surface from being worn off and at the same time improve the heat resistance of the blister pack when pressed. In order to reduce costs, some manufacturers cut corners and do not apply protective agents. As a result, pharmaceutical manufacturers often find that printed text patterns are blurry and susceptible to deinking during blister heat sealing, resulting in losses.
In fact, users can simply determine whether the aluminum foil used is coated with a protective layer before use. The method: cut a piece of aluminum foil, and then use a lighter to grill the protective layer for a few minutes. If there is no change in the surface of the protective layer or there are black smoke stains, once After wiping off, it is an unqualified aluminum foil product without a protective layer; if the protective layer turns yellow and has a halo-like pattern, it will not fall off after wiping, it is a product with a protective layer. However, in order to ensure the quality of use, the best way is to use a heat sealer to detect the heat resistance of the protective layer, and whether the heat resistance index of the protective layer is good or bad determines whether the hot roller (version) of the packaging machine is correct for the packaging of PTP aluminum foil when packaging drugs The graphics on the surface of the aluminum foil cause damage. During the test, use a 2 kg pressure heat sealer to heat and press the surface of the aluminum foil graphics and text at 200 ℃ for 1 s to observe whether the printed graphics and text are obviously off.
3.4.3 Uneven coating of aluminum foil
The surface of the aluminum foil printing is coated with a protective agent, and the other side is coated with an adhesive. Whether the adhesive coating is uniform and whether there is a missing coating will directly affect the sealing quality of the blister package, that is, the sealing performance.
Simple discrimination method: in the light
The place is observed with the naked eye, if it is found that there are clear linear straight stripes, or very short intermittent or uninterrupted straight horizontal stripes, it is a substandard product. The bonding layer of qualified products should be very smooth and flawless. Detection and quantification method: Analyze the balance by 1 / 10,000, take 5 pieces of 100 mm × 100 mm samples in the finished product, weigh them separately, then wipe off the adhesive with ethyl acetate, methyl ethyl ketone or other solvents, and then weigh The difference between the two is the coating amount, and the average value of the coating amount of 5 pieces is obtained. The difference between the coating amount of each piece and the average value should not be greater than ± 12.5%. In addition, the thickness of the adhesive layer has a great influence on the firmness of the adhesive. The adhesive layer is coated too thin. When the PVC hard sheet is hot pressed, the adhesive fastness will be reduced due to lack of material. Using a heat sealer to detect the heat seal strength of the adhesive layer can determine whether it meets the quality requirements. During the test, a square of 100 mm is die-cut, and the aluminum foil and the same size are used with a heat sealer with a pressure of 2 kg and a temperature of 150 ℃. The PVC sheet is heat sealed for 1 s. Then use a 15 mm special die cutter to cut into 15 mm strips. The magnitude of the tensile force tested on the tensile tester is the heat seal strength. The heat seal strength of the aluminum foil adhesive layer and PVC should be ≥7.0 N / 15 mm.
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