Thermoforming Packaging Technology (I)

Thermoformed packaging is also called card packaging abroad. The blisters, cavities, and disc trays formed after the thermoplastic plastic sheet is heated and formed are transparent, and the appearance of the product can be clearly seen. At the same time, the card as a substrate can be printed with exquisite designs and instructions for use of the product, facilitating display. and use. On the other hand, the packaged goods are fixed between the blister and the substrate, and are not easily damaged during transportation and sales, so that some products with complex shapes and pressure and fragile products are effectively protected. Protecting goods for a longer period of time can also serve to promote the sale of goods. Thermoplastic packaging imported from abroad in the 1970s was mainly used for packaging of tablets, capsules, suppositories, etc. However, due to the superiority of this packaging method, it has been widely used in the packaging of foods and daily necessities. At present, thermoformed packaging is mainly used in the packaging of pharmaceuticals, food, cosmetics, stationery, gadgets and mechanical parts, as well as toys, gifts, decorations and other aspects.
Thermoformed packages include blister packs and body packs. Although they belong to the same type of packaging method, there are still many differences in principle and function.
Blister packaging technology This packaging method was first invented and promoted in Germany in the late 1950s. It was first used for the packaging of tablets and capsules. It was to change the inconvenience of bottled tablets such as glass bottles and plastic bottles, and the investment in packaging production lines was large. Disadvantages, coupled with the development of dose packaging, the demand for small packages of pills is increasing. When a blister-packed tablet squeezes a small bubble by hand, the tablet can break out of the aluminum foil, and it is sometimes referred to as foamed or press-through packaging.
This package has a light weight, convenient transportation; good sealing performance, can prevent moisture, dust, pollution, theft and damage; can package any special-shaped products; packing does not use another buffer material and beautiful appearance, easy to use, easy to sell and so on In addition, there are advantages such as the fact that the tablet packaging will not be mixed with each other and will not be wasted. Therefore, this type of packaging has recently developed rapidly.
First, the common blister packaging structure Due to the rapid development of blister packaging, there are more and more blisters on the market, as shown in Figure 11-1, the figure:
a. The blister is sealed directly on the substrate.
b. The substrate is inserted into a special slot.
c. Pressure wear blister.
d. The bubble is sealed on the punched substrate.
e. After the blister or tray is inserted into the slotted substrate, it is sealed.
f. The substrate has a cover sheet that can be closed.
g. Half of the substrate is foldable, allowing the product to stand on the shelf.
h. Free access to the product without opening the blisters.
i. Double-sided blister, substrate punching.
j. All plastic without substrate strip packaging.
k. Double-layered blister package.
l. Separate multiple blister packs.
m. All plastic or double bubble caps without substrate blister packs.

Second, the choice of blister packaging materials From the blister packaging structure, it is mainly composed of thermoplastic plastic sheet and substrate, and some also use adhesive glue or other auxiliary materials.
1. There are many types of plastic sheets that can be used in blister packs for plastic sheets. Each of these types of plastic sheets, in addition to all the features and properties of the main material itself, also impart other characteristics, such as thickness, to the plastic sheet due to differences in the manufacturing process and additives used. , tensile strength, elongation, light transmittance, moisture permeability, aging, electrostatic, heat sealing, easy to cut and so on. At the same time, the size, weight value and impact resistance of the packaged articles and the shape of the packaged articles, such as the presence or absence of sharp edges and corners, will affect the effectiveness of the blister packs. Therefore, plastic sheets must be considered when selecting materials for blister packs. And the adaptability of the packaged goods, that is, the selection of materials to achieve the technical requirements of blister packaging, while minimizing the cost.
In general, there are three types of hard plastic sheets for blister packaging: cellulose, styrene, and vinyl. Among them, cellulose is most commonly used, including cellulose acetate cellulose, cellulose butyrate, and cellulose propionate. They all have excellent transparency and best thermoformability, good heat sealability and resistance to oil and grease penetration. However, the heat sealing moisture of cellulose is generally higher than that of other plastic sheets. Oriented styrene has excellent transparency, but it has poor impact resistance and is easily broken. At low temperatures, it is more visible, but it has better heat sealing properties. Vinyl resins are generally cheaper than styrene, and they are hard and soft. It can be heat-sealed with coated paperboard. Transparency is affected by additives. Some are excellent and some are excellent. Adding plasticizer can improve cold resistance and impact strength. There are also plastic sheets of composite materials such as polyvinyl chloride/polyvinylidene chloride, polyvinyl chloride/polyethylene, polychlorotrifluoroethylene/polyvinyl chloride, polyvinyl chloride/polyvinylidene chloride/polyvinyl chloride Wait. When packaging products requiring high gas barrier properties and light shielding, plastic sheets and aluminum book composite materials should be used; for foods and tablets, non-toxic plastic sheets should be used.
2. The substrate substrate is also the main component of the blister package. Like the plastic film, the size, shape and weight of the packaged item must be taken into consideration when selecting the substrate.
Substrates are mainly white cardboard, B-type and E-type coating (mainly coated heat-seal coating) corrugated sheet, coated aluminum foil and a variety of composite materials, of which the most commonly used is white cardboard. White paperboard is made from bleached sulfite pulp. It is also useful for waste paper and waste newsprint papers on the base paper. The surface of the paperboard substrate must be white and shiny, good printability, can firmly apply the heat seal coating, and must also have good tear-resistance binding force after being sealed with the blister. The thickness of the white paperboard substrate ranges from 0.35 to 0.75 mm; the commonly used one is 0.45 to 0.60 mm.
Third, the choice of blister packaging methods Blister packaging blister, cavity, disk box, etc. are different, the shape varies depending on the shape of the packaged items; useful substrates, there are no substrates. At the same time, due to the diversity of the forming part, the heating part, and the heat sealing part of the packaging machinery, the types of packaging machinery are numerous, so there are various kinds of blister packaging, but we can divide the blister packaging into manual operations and machinery according to the operation method. Operate two major categories.
1. This method of manual operation is suitable for the production of multiple varieties and small batches in areas with insufficient funds and sufficient labor. The blister and the substrate are pre-formed, printed and punched, and the product is manually placed in the blister, covered with a substrate, and then sealed on a heat sealer. Some products are not sensitive to moisture and drying and can be stapled directly with a stapler.
2. Automatic machine operation Although there are many types of packaging machines, their design principles are generally the same. Typical blister packaging machines must have thermoforming material supply sites, heating sites, molding sites, filling sites, sealing sites, and punching sites. The output of the molded container and the part where the excess material is collected are shown in Figure 11-2.
(a) The sheet is first conveyed from the roll of plastic film to an electric heater and heated to soften it.
(b) Place the heat-softened sheet on the mold (only the female mold). Then, the mold is filled with compressed air from above to attach the sheet to the mold wall to form a blister or a cavity. If the blisters or cavities are not deep and the film is thin, vacuum is drawn from the bottom of the mold to form a plastic film.
(c) Take out the cooling after molding, fill the packaged goods, and cover the printed card substrate.
(d) Heat sealing around substrates and blister.
(e) Punching into a single finished product. In addition to the above operations, the fully automated production line also includes filling inspection and reject removal devices, printing devices, and assembly instructions and cartoning, so that the production becomes more complete. Fully automatic machine operation is suitable for mass production of a single type, not only high productivity, low cost, but also meets hygienic requirements, so pharmaceuticals and small items are the most used for packaging.

(To be continued)