The most popular blister packaging printing coatin

Blister packaging printing coating quality

blister packaging of drugs is to place drugs in the pits of plastic hard sheets formed by blistering, and then use a printed and coated aluminum foil to bond and seal with the plastic hard sheets, so as to protect drugs and facilitate consumer identification and access. The quality monitoring points for the production of pharmaceutical blister packaging are mainly: the quality of adhesives, the bonding quality of plastic hard pieces and aluminum foil, and the quality of printed text and patterns of aluminum foil. In the production process of blister packaging, the quality of intaglio printing of aluminum foil and the heat sealing strength of the coating adhesive layer should be strictly controlled in production. Therefore, in the national standard aluminum foil for pharmaceutical packaging, there are clear requirements for the appearance quality of aluminum foil after printing, and there are also physical and chemical indicators for the quality of the adhesive layer, so as to ensure that the pharmaceutical blister packaging has good barrier, health and safety, heat sealing and good physicochemical properties

1. Types and properties of adhesives for aluminum foil

at present, adhesives for aluminum foil are divided into two categories: one is made of natural rubber or synthetic rubber and acrylic esters, which is called single component rubber type or rubber resin type adhesives. Its main agent is a kind of elastomer, which is prepared by adding tackifier and organic solvent in the form of lotion. The organic solvent in the adhesive mechanically coated on the substrate volatilizes under the action of strong hot air flow to form a coating. This kind of adhesive has adhesive force to a variety of materials, as long as it reaches the required temperature. It is characterized by low requirements for the surface state of the adherend. Because it is a single component, it will not produce cross-linking. It is simple to use. The unused glue will not deteriorate overnight or even stored for a longer time, as long as it is sealed and stored. The second type of adhesive is two-component polyurethane adhesive, which is composed of main agent and curing agent. Usually, the main agent and curing agent are packaged and stored separately. When used, they are mixed according to a certain proportion, and then diluted with solvent (such as ethyl acetate) to a certain concentration (such as 20%, 30% or 40%) before mechanical coating. The main agent of this adhesive is composed of many active hydrogen, such as hydroxyl, amino and other substances, while the curing agent is composed of polyisocyanate compounds. When the isocyanate group in the curing agent contacts with the active hydrogen in the main agent molecule, it will automatically carry out the addition reaction to form the structure of carbamate, so that the main agent and the curing agent are combined with each other, and the molecular weight is doubled, and even the cross products with branched chain structure and stereoconformation are formed, which have the characteristics of high and low temperature resistance, medium erosion resistance, high adhesion, etc. Because polyurethane molecules contain a large number of polar groups, large dipole moment, and have great affinity for bonded materials, it plays a bonding role for a variety of materials at the same time. In addition, the isocyanate group in the curing agent is a very active reactive group. In addition to reacting with the active hydrogen in the main agent molecule, it can also react with the active hydrogen in the surface substance molecule of the bonded material to form a chemical bond, so that the adhesive molecule can act as a bridge with the bonded two materials at the same time, resulting in a stronger adhesion. This is the reason why polyurethane adhesive can have a good adhesion to all kinds of materials. After full crosslinking and curing, polyurethane adhesive has high cohesion, strong, tough and soft appearance, good heat resistance and medium corrosion resistance, and still has extremely high adhesion at -170 ℃, which is unmatched by other adhesives. Using this kind of adhesive can make the aluminum foil and blister PVC hard sheet firmly hot pressed, so that the medicine is sealed. In the process of heat sealing, the adhesive layer is activated by heating, so that the aluminum foil and PVC hard sheet are firmly bonded together

2. Factors to be controlled in adhesive layer coating

2.1 certain temperature and time should be controlled in adhesive layer coating and drying. The adhesive layer needs to be dried in the process of mechanical coating, which requires three processes, namely, low-temperature blowing to volatilize the solvent; Medium temperature drying process; High temperature drying process. As the drying oven of the equipment is long, the time that aluminum foil needs to stay in the drying channel of the drying oven should be controlled. The degree of drying is related to the winding speed of the coater and the temperature in the oven. The winding speed is fast and the temperature is required to be high; The winding speed is slow, and the temperature is required to be low. Due to the different thermal expansibility and extensibility of aluminum foil, it is not allowed to stay at too high temperature for a long time, otherwise the aluminum foil is prone to wrinkles and surface discoloration. Speed and temperature control. In principle, it is appropriate that the adhesive solvent has volatilized and does not leave peculiar smell

2.2 the thickness of the bonding layer should be controlled within a certain range. The thickness of the adhesive layer has an impact on the bonding fastness. If the adhesive layer coating is too thin, the bonding fastness will be reduced due to lack of adhesive when hot pressing PVC hard sheets; If the coating is too thick, it will increase the production cost and cause waste, so the thickness of the adhesive should be controlled within an appropriate range. In the production process, the adhesive thickness depends on the number of lines of the coating line roller, the pressure of the rubber roller and the angle of the scraper. We call these three factors as fixed factors. Because there are a certain number of rolls in the production process, the pressure and force angle of the cots can also be adjusted by certain instruments. The variable factors are: the mechanical tension, adhesive concentration, coating speed, coating thickness, etc. during the coating process. The relationship between the variable factors is: the larger the adhesive concentration is, the smaller the coating tension is, and the faster the coating speed is, the thicker the coating is relatively; On the contrary, the smaller the concentration, the greater the tension, the slower the speed, and the thinner the coating. Therefore, the thickness of the adhesive layer is adjusted by the concentration of the adhesive and the tension of the coater. Different varieties of aluminum foil have slightly different requirements for the thickness of the adhesive layer. Generally, the thickness should be controlled at 1 Micron is appropriate

3. Quality control of aluminum foil gravure printing

3.1 it is necessary to master the mixing concentration of ink and solvent. According to the speed of the printing coater and the printing concave, the rapid circulation production of large heat-resistant parts under the hood should be improved, and the inking hole depth of the plate roller should be the best printable ink concentration. The factors that affect the ink concentration are mainly temperature and humidity. It is best to use the ink concentration detector to determine the amount of solvent added, and measure the ink concentration every 30 minutes according to the change of temperature and humidity, and adjust it according to the data to ensure the printing quality. If the concentration of gravure printing ink used is too low, it is easy to cause the color of printed text pattern is not bright, and there is a paste phenomenon at the lines; If the ink concentration is high, it is easy to cause no ink at the starting point of the scraping direction; If the ink concentration is very high, the pattern will crack. The ink spots and blocks on the surface of aluminum foil are in pieces, and the surface quality is poor

3.2 properly apply diluent. When a large amount of diluent is needed for the ink with high viscosity, the diluent should be added and stirred to achieve uniformity, and the diluent should be evenly distributed in the whole ink. If the diluent is added, it is fixed locally and rushed in without stirring evenly, it is easy to wrap the local ink around the periphery of the pigment and peel off the resin, resulting in pigment precipitation, especially if the relative density of the pigment is larger. Because the viscosity of the ink and the relative density of the pigment are different, the thickness of each color of ink cannot be treated the same. Generally, it is adjusted to the graphic field without needle sharp ink dots, and the handwriting lines have no broken pens, The scribed line should be clear, and the measurement is about seconds with a viscometer 4# cup

3.3 how to detect the ink coagulation and sedimentation treatment of oil space cotton tension machine. Because the ink binder (polyamide) will be affected by the temperature or the excessive diluent used in the ink will cause the relative density of the solvent and the resin to be small and reduce the solubility of the resin, the coagulated and precipitated ink must be stirred or treated by increasing the temperature. If the ink is stored for a long time, or for other reasons, the ink will precipitate and the resin solution on the upper layer of the ink will appear, so you must remember that there are more pigments on the lower layer; The upper layer is light in color and the lower layer is dark, which leads to poor fastness. Therefore, it should be stirred during use

4. Quality problems and solutions of aluminum foil printing

4.1 color difference of aluminum foil gravure printing. The consistency of printing color can only be relative. It is difficult to strictly control the color difference of the same batch of products, and it is more difficult to strictly control the color difference between large batches or different batches of products. Reason ① ink: ink is the main factor that determines the color consistency of printed products. Ink itself also has the problem of color difference between the same batch and different batches, which is an important indicator of ink quality. To solve the color difference problem of aluminum foil gravure printing, we must first choose inks with stable quality and no deviation in hue. It is best to use the same batch of inks for a batch of prints, because it is difficult to ensure that there is no difference in hue between batches of inks. Secondly, it is required that the amount of ink added to the ink tray each time in the printing process should be less, so as to keep adding new ink frequently. Especially for some patterns with less ink, if the ink is added too much at a time, the ink will be oxidized after being exposed to the air for a long time, which will make the ink color obsolete. For example, the black ink used for a long time is not as black as the new ink; Long used red ink will turn dark red, not as red as new ink. In the printing process, the volatilization rate of the mixed solvent used by the ink should also be strictly controlled. When the volatilization rate is too fast, the transfer rate of the ink may be reduced, thereby affecting the color of the print

4.2 odor problems. When prints are used as packaging, no odor is allowed. The main reason for the odor is that the adhesive protector has incomplete reaction and monomer odor. The adhesive with good quality has no smell except ethyl ester, while the adhesive with incomplete reaction can smell the smell of monomer. Another reason is the smell of the ink. This is because there are too many high boiling solvents in the ink, which do not evaporate completely during the printing process. Although they pass through the composite drying channel, they still do not completely escape. In particular, the smell of toluene solvents is the largest, which can be smelled when opening the roll, and it is also found in the printed matter. The solution can be tailored to the case. The reason is that the adhesive can be replaced. If the adhesive with good quality is adopted, only the adhesive of the sensor can be replaced again; Because of the ink, in addition to using other inks, you can also store the printed matter for a long time. Benzene solvents should not be used when using solvents

4.3 cutter thread problem. Knife wire refers to that part of the ink without pattern lines on the layout is not scraped and transferred to the printed matter, and linear pollution occurs where ink is not allowed. Generally, such problems occur after printing for a period of time and a certain number of prints. Printing ink, printing plate roller and scraper are the main factors for the appearance of knife thread. The reason ① is related to the quality of ink. This phenomenon is less when using high-grade ink, and more when using low-grade ink. In addition, impure substances, coarse particles, foreign matters, etc. in the ink can form knife wires by lifting the scraper or damaging the scraper. ② The printing ink viscosity is too high, the printing ink of the layout is too dry, and the friction between the cylinder and the scraper is relatively increased, so the scraper is difficult to scrape off the printing ink of the layout. ③ The poor gloss and chrome plating quality of the cylinder or the adhesion of hard objects on the plate will directly damage the scraper. Solution: try to reduce the viscosity of the ink, so that the scraper can easily scrape the ink off the non picture part; Try to increase the proportion of using fresh ink; Adjust the scraper (grinding, pressing, hardness, thickness, angle, position, etc.), check whether the scraper is installed smoothly and evenly, and try to use slow drying solvent

4.4 ink drying too fast