Application of cold stamping hard sheet for bliste

2022-06-22
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Application of blister packaging cold stamping hard film

aluminum plastic blister packaging of drugs is also called blister eye packaging, or PTP packaging for short. The packaging material diaphragm is formed by heating, vacuum forming or cold stamping to form grooves suitable for tablets, capsules and other shapes, and then filled with drugs. Then, the drug packaging with heat sealable coating is heat sealed with aluminum foil to form unit packaging

the covering material for the aluminum-plastic blister packaging of drugs is generally aluminum foil (called the aluminum foil for drug blister packaging), while the foam forming base material is generally polyvinyl chloride (PVC) hard sheet. However, with the continuous development of the pharmaceutical industry, the traditional packaging method has exposed its defects. Due to the limited barrier performance of PVC hard sheets, it is difficult to ensure that the quality of drugs will not change during their service life. In view of the limited barrier performance of ordinary blister packaging, people developed cold stamping and pressing hard films in the early 1980s with a new concept. The cold stamping forming uses stamping forming instead of the vacuum blister forming of the original ordinary blister packaging, so that the blister packaging sheet can use pure aluminum foil composite as the foaming material. The application of high-strength alloy aluminum foil in cold stamping forming hard sheet also makes the cold stamping forming hard sheet have extremely high water vapor, oxygen and light barrier properties that can not be achieved by any other material

figure 1: aluminum plastic blister packaging of drugs

cold stamping formed hard films are generally composed of three functional layers: surface support strength layer, intermediate aluminum foil barrier layer and inner surface heat sealing layer. The surface support layer can be printed with the color or pattern required by the customer, and the layers are bonded together to form a composite film. The surface supporting strength layer of the cold stamping hard sheet shall be smooth, flat, transparent, with high mechanical strength, excellent impact resistance, and certain wear-resisting and puncture resistance, which plays a mechanical protection role for the whole package. Biaxially oriented nylon film (BOPA) with high strength and excellent impact resistance is generally used as the surface support layer of cold stamping hard sheet. Due to the great impact and tensile force on the cold stamping formed hard sheet during the cold stamping and foaming process of the packaging, the 15 μ M-thick BOPA can not meet its requirements. Except for shallow stamping, 25 μ M thick BOPA as surface support strength layer. For shallow stamping occasions, in order to save costs, biaxially stretched polyester film (BOPET) or biaxially stretched polypropylene film (BOPP) can also be used to replace biaxially stretched nylon film

in addition to the barrier function, the intermediate aluminum foil barrier layer used for cold stamping forming also has the functions of strength support, stamping tensile resistance and so on. Therefore, it is different from the intermediate aluminum foil barrier layer used for cold stamping forming of general flexible packaging. In addition to the barrier function, it also has the functions of strength support, stamping tensile resistance and so on. Therefore, it is different from the general flexible packaging composite aluminum foil. The aluminum foil used for cold stamping is not ordinary pure aluminum foil, but alloy aluminum foil with high strength and good extensibility. Because the cold stamping forming hard sheet needs to be stamped. Therefore, the thickness of aluminum foil used is much thicker than that of ordinary composite film, generally 45 μ For m-thick aluminum foil, the thickness of aluminum foil can be appropriately reduced for the occasion of stamping shallow bubbles, generally the minimum can be reduced to 3 μ The thickness of aluminum foil can be appropriately increased to 70 for the occasions where the foam forming depth is very deep (≥ 15mm) or where the cold stamping hard sheet is required to have good stiffness μ m。

polyvinyl chloride (PVC) hard sheets are generally used as the heat sealing layer on the inner surface of cold stamping hard sheets, so that the cold stamping hard sheets can be heat sealed with PTP aluminum foil for drug packaging like PVC hard sheets for ordinary blister packaging. The PVC used for cold stamping hard sheet is different from ordinary PVC. Considering the factors such as compounding and stamping, ordinary plasticizers and lubricants are usually not used, but internal plasticization and internal lubrication are carried out by grafting plasticizer factors into PVC molecular chain segments. At the same time, in order to improve the impact resistance of PVC, more reinforcing agents are added to PVC hard sheets than ordinary PVC hard sheets, so that it has good composite properties and stamping forming properties. The thickness of PVC in cold stamping hard sheet is generally 60 μ m. When the product is required to have high rigidity and stiffness, the thickness of PVC can be increased appropriately, up to 100 μ M thick, polypropylene and polyethylene can also be used in some special occasions; Polyester and Surlyn resin are used as heat sealing layer

figure 2: PVC hard sheet for cold stamping

the surface support strength layer, aluminum foil barrier layer and inner surface heat sealing layer in the cold stamping forming hard sheet are bonded by adhesive, which organically combines them into a composite material. In order to ensure that the cold stamping hard sheet will not separate or break under the strong impact forming force, the selection and use of the adhesive is very critical. Generally, the adhesive strength between the aluminum foil and the surface support strength layer and the heat sealing layer after bonding is required to reach more than 8n/15mm. The ratio of the soft segment and the hard segment of the molecular chain in the polyurethane adhesive should also be controlled during the formulation design process; To meet the requirements of cold stamping. It is difficult for ordinary adhesives to meet the above requirements, so the adhesives used for cold stamping hard films are generally special adhesives specially prepared for

although the cold stamping blister packaging has good appearance and extremely high barrier performance, the product has many characteristics different from other packaging materials in the process of use, and the following problems often occur in the process of use:

1. Cracks and pinholes of aluminum foil occur on the blisters of the cold stamping hard sheet during foaming; As well as the separation between composite membranes, the causes of these defects mainly include the following three categories:

the first category is the quality problems of cold stamping hard films. Cold stamping forming hard sheet is a product with high technical content, which has many special requirements for raw materials and production process. If all links in production are not well controlled, it is very easy to have quality problems. The quality problems of cold stamping formed hard films can be easily determined by replacing cold stamping formed hard films of different batch numbers or even different manufacturers

the supporting strength layer of the cold stamping hard sheet is mainly 25% of the biaxial tensile strength layer of the outer surface layer μ M thick nylon film. The hardness of nylon membrane is low; Easily scratched by hard objects; Once the nylon surface is scratched, even if it is a very slight scar; Will greatly reduce the strength of the nylon film, resulting in the fracture of the aluminum foil and nylon film at the scratched part of the cold stamping hard sheet during the stamping process. In the actual production process, it is difficult to find the scratch, especially the slight scratch, on the hard sheet formed by cold stamping with the naked eye, and it is often found when it is stamped into bubbles; Thus causing losses. The scratch of the cold stamping hard sheet is generally caused by the inflexible rotation of the guide roller during the operation of the composite film, the foreign matters on the guide roller, and the contact of the composite film with the fixed part of the equipment (such as the electrostatic brush). The scratch may be caused by the manufacturer in the production process, or by the user on the packaging equipment

figure 3: biaxially stretched nylon film on the outer surface of cold stamping formed hard sheet

cold stamping formed hard sheet contains hygroscopic nylon material. After nylon absorbs moisture, it is easy to cause separation between nylon film and aluminum foil during the stamping process of cold stamping formed hard sheet, resulting in rupture of tin foil or pinholes, thus reducing the foaming rate of cold stamping formed hard sheet. Even for the finished products of cold stamping forming blister packaging, the foam forming part is easy to cause separation between nylon and aluminum foil after being parked in a humid environment (the nylon and aluminum foil do not separate when they are just produced, but after being parked in a humid environment for a period of time), so the cold stamping forming hard sheet and its double aluminum blister packaging products. Store in a dry environment

the second type is that the stamping die design is defective. The cold stamping forming hard sheet uses mechanical stamping to generate a blister. During the stamping process, the cold stamping forming hard sheet has great stress and tensile deformation, which is almost close to the limit of the material. If the stamping die is not designed properly, it may lead to the cracking of the aluminum foil in the stamping process. Die design includes die material and punch geometry

generally speaking, polyoxymethylene molds have lower friction coefficient and better stamping performance than stainless steel molds, and polytetrafluoroethylene molds have lower friction coefficient and better stamping performance than polyoxymethylene molds. The low friction coefficient is conducive to reducing the friction in the process of pressing under the intact technical state of the punching protection machinery, avoiding the uneven stress of the cold punching forming material, and greatly avoiding the aluminum foil crack and the separation of the composite film during the stamping process. For the drugs of the same size, reducing the friction coefficient can have a larger stamping drawing ratio, so as to effectively reduce the area of packaging materials and reduce the cost. The friction coefficients between the three moulds of polytetrafluoroethylene, polyformaldehyde and stainless steel and the PVC surface of the cold pressed hard sheet are 0.4, 1.2 and 2.1 respectively. For the same drugs packed to the same depth, the required foaming area ratio is 1:1.2:1.4. The use of polytetrafluoroethylene punches can effectively prevent the aluminum foil from cracking and the composite film from separating during the stamping process, and can also save packaging materials. Therefore, except for very shallow stamping occasions, polytetrafluoroethylene is generally used as the stamping die. Of course, polytetrafluoroethylene also has a disadvantage, that is, the hardness is not high enough, and the stamping die head is easy to be damaged and scratched. Using the damaged die head to punch bubbles is easy to cause aluminum foil pinhole cracking and increase the scrap rate

in addition to material, the size and geometry of the cold stamping die have a great impact on the cracking of aluminum foil and the separation of composite film. There are generally two types of stamping die heads: smooth transition type and stepped transition type. The blister produced by the smooth transition die is beautiful, but its punching depth resistance and punching fracture resistance are relatively poor. The stepped transition die head is divided into several angular steps, which are stretched by stages during the stamping process. The cold stamping formed hard piece has less contact area with the stamping die head during the stamping process, which is conducive to uniform stretching and foaming. Because the size and shape of the stamping die have a great influence on the foaming rate of stamping forming, people have specially developed the corresponding computer software, which can automatically design the best geometric shape of the stamping die according to the overall dimensions of the packaged tablets. So as to avoid excessive local stress and tension in the process of cold stamping forming

the third type is improper stamping process control. The cold stamping hard sheet is formed into bubbles by mechanical stamping and stretching. As a metal layer material, the elongation of aluminum foil in cold state is limited. Although the aluminum foil used for cold stamping is a special alloy aluminum foil, its elongation is only about 20%. If the stamping is too deep and the aluminum foil is stretched too much, it is easy to produce aluminum foil cracking and composite film separation. The stamping depth of the general cold stamping forming blister packaging machine is designed to be adjustable. The stamping depth should be reduced as far as possible under the condition that the drug can be contained and the PTP aluminum foil does not stick to the drug during heat sealing. The cracking of aluminum foil in the stamping process is related to the thickness of aluminum foil. If it is really necessary to punch deep bubbles, in addition to increasing the area of die holes, it can also appropriately increase the thickness of aluminum foil material in the cold stamping hard sheet to improve. Cold stamping process小孩子消化不良吃什么好
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