Thermoforming packaging technology (Part 1)
thermoforming packaging is also called card packaging in foreign countries. The blisters, holes, boxes, etc. formed by heating and forming thermoplastic plastic sheets are transparent, which can clearly see the appearance of goods. At the same time, the card as the substrate can print exquisite patterns and instructions for goods, which is convenient for display and use. On the other hand, the packaged goods are fixed between the blister and the substrate, which is not easy to be damaged in the process of transportation and sales, so that some goods with complex shapes and are afraid of being crushed can be effectively protected. Therefore, this packaging method can not only protect the goods and prolong the shelf life, but also play a role in publicizing the goods and expanding sales. Thermoforming packaging introduced from abroad in the 1970s is mainly used for the packaging of tablets, capsules, suppositories and other aspects. However, due to the advantages of this packaging method, it has been widely used in the packaging of food and daily necessities. At present, thermoforming packaging is mainly used for sales packaging of medicine, food, cosmetics, stationery, gadgets and machine parts, as well as toys, gifts, decorations and other aspects
thermoforming packaging includes blister packaging and body fitted packaging. Although they belong to the same type of packaging methods, there are still many differences in principle and function
elastic flexion and packaging technology produced by blister package strain
this packaging method was first invented and popularized in Germany in the late 1950s. It was first used for the packaging of tablets and capsules. At that time, it was to change the disadvantages of glass bottles, plastic bottles and other bottled tablets, such as inconvenient to take, large investment in packaging production lines and so on. Coupled with the development of dose packaging, the demand for small packaging of tablets is increasing. The blister packed tablets can break through the aluminum foil by squeezing the bubbles by hand when taking medicine, so some people call it foaming or pressing through packaging
this kind of package has the advantages of light weight and convenient transportation; Good sealing performance, can prevent moisture, dust, pollution, theft and damage; Can pack any special-shaped products; There is no buffer material for packing, and it is beautiful, convenient to use and easy to sell. In addition, the tablet packaging will not be mixed and wasted. So this kind of packaging has developed rapidly recently
I. common blister packaging structures
due to the rapid development of blister packaging, there are more and more blister structures in the market at present, as shown in the figure, In the figure:
a. the blister is directly sealed on the substrate.
B. the substrate is inserted into a special slot.
C. the press through blister.
D. the blister is sealed on the perforated substrate.
e. the blister or shallow dish is inserted into the grooved substrate and sealed.
F. the substrate has a cover sheet that can be closed.
g. half of the substrate can be folded, Products can be placed on the shelf.
h. free access to goods without opening the blister.
I. double sided blister, with perforated substrate.
J. full plastic substrate free strip packaging.
K. blister packaging with double substrates.
L. separated multi blister packaging.
M. blister packaging with full plastic or double blisters without substrate.
II. Selection of blister packaging materials
from from the structure of blister packaging, It is mainly composed of thermoplastic plastic sheets and substrates, and some also use adhesives or other auxiliary materials
1. Plastic sheet
there are many kinds of plastic sheets that can be used for blister packaging. In addition to all the characteristics and properties of their main materials, each kind of plastic sheet is also endowed with other characteristics due to different manufacturing processes and additives, such as thickness, tensile strength, elongation, light transmittance, moisture permeability, aging, electrostatic, heat sealing, easy to cut, etc. At the same time, the size, weight value and impact resistance of the packed items, as well as the shape of the packed items, such as whether there are sharp edges and corners, will affect the effect of blister packaging. Therefore, when selecting the materials for blister packaging, we should consider the adaptability of plastic sheets and packed items, that is, the selection of materials should meet the technical requirements of blister packaging, and try to reduce the cost
generally, rigid plastic sheets used for blister packaging include cellulose, styrene and vinyl resin. Among them, cellulose is the most widely used, including cellulose ester, cellulose butyrate and cellulose propionate. They all have excellent transparency and best thermoformability, good heat sealing and oil and grease resistance. However, the heat sealing humidity of cellulose is generally higher than that of other plastic sheets; The directional stretching distance is measured by the rotating photoelectric encoder. Styrene has excellent transparency, but poor impact resistance and is easy to break. It is more obvious at low temperature, but it has good heat sealing property; Vinyl resins are generally cheaper than styrene, including hard and soft ones. It can be well heat sealed with coated paperboard. The transparency is affected by additives, some are better and some are excellent. Adding plasticizer can improve the cold resistance and impact strength. In addition, there are plastic sheets of composite materials, such as polyvinyl chloride/polyvinylidene chloride, polyvinyl chloride/polyethylene, polyvinyl chloride/polyvinylidene chloride/polyvinyl chloride, polyvinyl chloride/polyvinylidene chloride/polyvinyl chloride, etc. When packaging products that need high gas resistance and light shielding, plastic sheet and aluminum sheet composite materials should be used; Non toxic plastic sheets are required for packaging food and tablets
substrate is also the main part of blister packaging. Like plastic sheet, it is necessary to consider the size, shape and weight of the packaged items when selecting
the substrates mainly include white paperboard, B-type and E-type coating (mainly heat sealing coating), corrugated sheet, coated aluminum foil and a variety of composite materials, among which white paperboard is the most commonly used. White paperboard is made of bleached sulfite wood pulp, and waste paper and waste paper are also used as white paper on the base. The surface of the cardboard substrate must be white and shiny, with good printability, and can be firmly coated with heat sealing coating. At the same time, it must also have good tear resistance after sealing with the blister. The thickness range of white paperboard substrate is 0.35 ~ 0.75mm; Commonly used is 0.45 ~ 0.60mm
III. selection of blister packaging methods
blister high-performance fibers, composites, holes, boxes, etc. in blister packaging are large or small, and the shape varies with the shape of the packaged items; There are those with or without substrates. At the same time, due to the diversity of the molding part, heating part and heat sealing part of the packaging machinery, there are many kinds of blister packaging, but we can divide blister packaging into manual operation and mechanical operation according to the operation method
1. manual operation
this method is suitable for multi variety and small batch production in areas with insufficient funds and sufficient labor. The blister and substrate are pre formed, printed and cut. When packaging, manually place the goods in the blister, cover the substrate, and then seal them on the heat sealer. Some goods are not sensitive to humidity and dryness and can be sealed directly with staplers
2. Automatic machine operation
although there are many kinds of packaging machines, their design principles are roughly the same. Typical blister packaging machines must have hot forming material supply parts, heating parts, forming parts, filling parts, sealing parts, punching parts, molded container output and residual material collection parts. The packaging operation process is shown in the figure
(a) first, the sheet is transferred from the plastic sheet drum to the electric heater for heating to soften it
(b) place the heated and softened sheet on the mold (only the female mold). Then fill the mold with compressed air from the top to make the sheet stick to the mold wall to form blisters or holes. If the blister or hole is not deep and the film is thin, vacuum it from the bottom of the mold to take shape
(c) take out and cool after forming, fill the packaged goods, and cover the printed card substrate
(d) heat seal around the substrate and blister
(E) punching into a single finished product. In addition to the above operation process, the fully automated production line is also equipped with filling detection and waste removal devices, printing devices, instructions and boxes, making the production more complete. Fully automatic mechanical operation is suitable for mass production of a single variety. It not only has high productivity, low cost, but also meets the health requirements. Therefore, the packaging of drugs and small commodities is most widely used
(to be continued)