The problem of printing and coating of aluminum foil for pharmaceutical packaging needs to be paid attention to
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In recent years, the quality of pharmaceutical PTP aluminum foil packaging has been continuously improved, and the application range has been continuously expanded, such as food packaging and health care product packaging. However, some problems have appeared in the PTP aluminum foil printing process, causing different degrees of loss and adverse effects. In order to improve the quality of aluminum foil printing and its use, this paper selects the feedback quality problem of most users and summarizes several common frequency. High, influential, and urgently needed to be discussed with colleagues, the purpose is to enable managers who use aluminum foil packaging machinery to better cope with the quality problems caused by them.
2 concept of medicinal aluminum foil
The metal foils used in pharmaceutical packaging applications are aluminum foil, which is called aluminum foil for pharmaceutical packaging (commonly known as PTP aluminum foil), and PTP aluminum foil is from English PressThrough Packaging (literally: packaging by pressure). The more formal term in the industry is for pharmaceutical packaging. Aluminum foil, also known as aluminum foil for blister packaging. China's title for PTP aluminum foil used in pharmaceutical packaging materials and container registration certificates: PTP aluminum foil for pharmaceutical packaging.
One of the main raw materials for the production of PTP aluminum foil is industrial hard pure aluminum foil, which is used in pharmaceutical packaging materials.
It is customary in the industry to be called "original aluminum foil" or original foil. When used as a pharmaceutical packaging material, aluminum foil is the only metal material in the packaging material. The aluminum foil has: (1) non-toxic, odorless; (2) excellent electrical conductivity and light-shielding property; (3) extremely high moisture resistance, gas barrier property and taste-keeping property, and can most effectively protect the packaged article. Therefore, it is a packaging material that has not been replaced so far, and neither the vapor-deposited metal film nor the coated special film can completely replace the aluminum foil. In the field of modern packaging and decoration, almost all composite flexible packaging materials that require opacity or high barrier are made of aluminum foil as a barrier layer. Since the aluminum foil has the above advantages, and has the characteristics of light weight, good strength and good printability, various characters or patterns can be printed thereon. When the blister pack is made, it can be crushed with a little pressure, and the patient takes convenience and is convenient to carry.
3 Common quality problems in aluminum foil printing
In the process of printing aluminum foil, there are often some quality problems, which are summarized as follows.
3.1 Aluminum foil printing quality does not meet the standard requirements
Common problems with print quality that do not meet the standard requirements are: ambiguous printing, misprinting, especially overprinting of aluminum foil.
3.1.1 Printing font blur
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 not appropriate; (4) the tension of the aluminum foil is not well adjusted; (5) the ink is dried too slowly (6) The running speed is not coordinated. Control and improvement methods: According to the above problems, we should treat them specifically: (1) improve the viscosity of the ink; (2) level or replace the scraper as much as possible; (3) adjust the angle of the scraper and carry out the whole line of the scraper; (4) adjust or confirm Tension; (5) Change to quick-drying solvent and increase heat to increase drying speed; (6) Confirm whether the plate cylinder and aluminum foil are running at a coordinated speed.
3.1.2 Overprint aluminum foil font misalignment
Cause: Because the overprint is printed with multiple plates, 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 out, such as the bending of the printing shaft, the shaft sleeve is not oiled to cause wear, and the unevenness of the traction roller will cause the font to be misaligned in the overprint; (2) Printing version The uneven pressure of each set of rollers, the uneven pressure on the left and right sides of the plate roller, the looseness of the printing roller and other factors cause the overprinting to be inaccurate, the font is misplaced; (3) the technical problems, the unwinding of the unwinding and winding tension of the raw materials, Mistakes in operation, improper heat transfer, misalignment of tension, etc. affect the misplacement of overprinted fonts; (4) misalignment of overprinting fonts due to different specifications (over normal error range); (5) high viscosity of ink, affecting overprinting, font Misalignment; (6) The performance change of the aluminum foil raw material (uneven thick book) affects the constant tension, causing the font to be misaligned.
Solution: (1) Equipment should be established with a circuit inspection system to regularly refuel the operating system. The worn equipment parts should be replaced regularly, and the replacement date record should be established for searching; (2) The post-operation method should be established in the process technology, and the opening and winding tension values required for the operation, as well as the hot air temperature, air volume, and blowing time should be established. It is detected by the operator on time. And there are inspection records; (3) plate making should conform to the actual sample provided by the user and compare with the actual proofing of the overprinting roller. If it meets the requirements, it can be put into production by the quality inspector. (4) The viscosity of the ink should be changed according to the climate temperature. The viscometer is adjusted at any time; (5) the performance of the original aluminum foil varies greatly, and it is necessary to coordinate the replacement of raw materials.
3.2 The color of the ink is different
Generally, the color of the first-produced aluminum foil after printing has a slight color difference with the reference sample, mostly due to the difference in the ink material or substrate. If necessary, the buyer can confirm at the supplier's site, and the production and printing process must be strictly controlled.
3.2.1 The color is too light
(1) The printing density of the same batch is not enough: the cause is: 1) too much solvent in the ink; 2) ink precipitation; 3) the gravure engraving is too shallow. Solution: 1) add new ink, adjust the ink to the appropriate viscosity; 2) fully stir the ink before putting it into the ink tray, and preheat the appropriate temperature in the northern winter.
(2) The printing color of the same batch is too rich: the cause is: 1) the viscosity of the ink is too large; 2) the ink concentration is too large; 3) the intaglio engraving is too deep or damaged. Solution: 1) Add a specified amount of solvent to the ink, adjust the ink to the appropriate viscosity; 2) Add the diluent; 3) Re-create the gravure cylinder or fill the dent.
3.3 Printing aluminum foil to wrinkle
There are many reasons for the wrinkles, such as wrinkles appearing in the printing process, the reason for the aluminum foil of the raw materials, the wrinkles caused by improper adjustment of the pharmaceutical packaging equipment, and the wrinkles caused by the unevenness of the aluminum foil heat sealing material. Only the wrinkles that appear during the printing process are analyzed below.
The reasons for wrinkles during printing: (1) the edge of the aluminum foil material is loose; (2) the central portion of the material is loose; (3) the printing tension is not appropriate, or the substrate itself has wrinkles;
(4) The angle at which the aluminum foil is wound on the guide roller or the rubber roller is too large; (5) the hardness of the rubber roller is insufficient; (6) the machine or the roller and the guide roller are improperly arranged.
Solutions for wrinkles during printing: (1) use of eccentric roller shafts; (2) use of bow rollers, tension adjustment rollers; (3) appropriate adjustment of tension; (4) adjustment of aluminum foil winding angle; (5) use of high hardness Rubber roller; (6) Study the assembly position of the machine and the drum.
3.4 Problems that seriously affect the quality of pharmaceutical packaging
3.4.1 Printing substrate aluminum foil pinhole exceeds the standard
According to GB 12255-1990: "The pinhole diameter on PTP aluminum foil is more than 0.3 mm, and the diameter of 0.1 to 0.3 mm should not exceed 1". PTP aluminum foil pinholes are due to penetrability defects, which affect the barrier properties (gas barrier, moisture barrier, and opacity) of aluminum foil, so that the packaged drugs are affected by oxygen, water vapor or light to reduce the efficacy. Even deterioration can not be used. Since water vapor permeation and oxygen permeation are important indicators of aluminum foil as a packaging material, the specified value is generally low. At the same time, the aluminum foil itself, especially the aluminum foil having a thickness of 0.02 mm or less, is easily wrinkled, easily broken, and easily pinholes. Therefore, the detection of the water vapor transmission amount and the oxygen permeation amount of the pure aluminum foil is quite difficult, and the dispersion of the detection data is large. Aluminum foil pinholes are the only factor in the transparency of aluminum foil. In general, only the size and number of aluminum foil pinholes can be used to illustrate the problem. According to relevant research, the gas permeation amount of pure aluminum foil is proportional to the difference of gas concentration. When the pinhole radius of aluminum foil is larger than the thickness of aluminum foil, it is proportional to the radius of pinhole. Therefore, the quality of the original aluminum foil should be inspected before the aluminum foil is printed, especially the pinhole, tear strength and tensile strength of the original aluminum foil are sampled. At present, China's aluminum foil manufacturers have reached the national standard for aluminum foil pinhole requirements and can ensure stable quality, but some small PTP aluminum foil manufacturers often simply to reduce costs, seize the market at low prices, often use some unqualified original aluminum foil, so that The pinhole is out of specification. 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, streaks, etc., which not only affects the printing quality of characters and patterns, but also affects the coating quality of the protective agent and the adhesive, thereby affecting the pharmaceutical packaging. Sealing performance.
The method for judging the number of pinholes is to take a piece of the original aluminum foil and observe the presence or absence of pinhole leakage with the naked eye. Professional testing aluminum needle pinhole with detection equipment for pinhole table, using 800 mm × 600 mm × 300mm or appropriate volume wooden box, 30 W fluorescent lamp installed in the wooden box, a glass plate placed on the wooden box, the glass plate is black The paper is left with a space of 400 mm × 250 mm to inspect the sample pinhole. Take 20 sheets of 400 mm × 250 mm specimens in the finished aluminum foil, place them one by one on the pinhole inspection table, and inspect the pinholes in the dark. The requirements for the aluminum foil pinholes are: (1) There should be no dense, Continuous, periodic pinholes; (2) There must be no pinholes with a diameter greater than 0.3 mm, and pinholes with a diameter of 0.1 to 0.3 mm should not exceed one per square meter. Aluminium foil pinhole 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 Applying protective layer after printing
According to the process requirements, the surface of the aluminum foil after printing needs to be coated with a protective agent for protecting the printed text pattern. Of course, the protective layer also prevents the aluminum foil from being in contact with the adhesive of the inner layer when the aluminum foil is wound up, thereby causing the drug to be contaminated. It can also prevent the self-oxidation and deterioration of the surface of the aluminum foil and prevent the abrasion and detachment of the ink layer on the surface of the aluminum foil, and also improve the heat resistance of the blister charge when pressed. Some manufacturers reduce the cost, cut corners, and do not apply protective agents. As a result, pharmaceutical manufacturers often find that the printed text pattern is illegible when the blister is heat-sealed, which is easy to deink and cause losses.
In fact, the user can easily determine whether the aluminum foil used is coated with a protective layer before use. The method is: cut a piece of aluminum foil, and then use a lighter to bake the protective layer for a few minutes. If the surface of the protective layer is found to be unchanged or has black smoke stains, once Wipe off, which is an unqualified aluminum foil product without a protective layer; if the protective layer is found to be yellow, and a pattern like a halo is found, it will not fall off after wiping, that is, a product coated with a protective layer. However, in order to ensure the quality of use, the best method is to use the heat sealer to detect the heat resistance of the protective layer, and the heat resistance index of the protective layer determines whether the hot roll (version) of the packaging machine of the PTP aluminum foil is packaged. The surface of the aluminum foil is damaged. During the test, a 2 kg pressure heat sealer was used to heat and press the surface of the aluminum foil at 200 ° C for 1 s to observe whether the printed image was obviously peeled off.
3.4.3 Aluminum foil coating adhesive uneven
The aluminum foil printing surface is coated with a protective agent, and the other side is coated with an adhesive. Whether the adhesive coating is uniform or not, the leakage coating will directly affect the sealing quality of the blister package, that is, the sealing performance.
Simple method of discrimination: in a well-lit
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 level of qualified products should be very smooth and flawless. Detection and quantification method: Analyze the balance with one ten thousandth, take 5 pieces of 100 mm × 100 mm sample in the finished product, weigh them separately, then wipe off the adhesive with ethyl acetate, methyl ethyl ketone or other solvent, then weigh The difference between the two masses is the coating amount, and the average value of the five coating amounts is determined, and the difference between the coating amount and the average value of each sheet should be no more than ±12.5%. In addition, the thickness of the adhesive layer has a great influence on the degree of bonding firmness, and the adhesive layer is too thin to be applied. When the PVC hard sheet is hot-pressed, the bonding fastness is lowered due to lack of material. Using a heat sealer to detect the heat seal strength of the adhesive layer, it is possible to determine whether the quality requirement is met. When testing, a 100 mm square is die-cut, and a pressure of 2 kg, a temperature of 150 ° C, a heat sealer, aluminum foil and the like are used. The PVC sheet is heat sealed for 1 s. It was cut into 15 mm strips using a special 15 mm die cutter. The size of the tensile force measured 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.