Production of PET preforms, plastic bottles

The product

The PET preform, better known as preform, is accomplished through a molding process. The fused PET injected into a mold become a preform, which, by an additional processing step (blowing), takes the form of bottles for beverages for elementary, oil or detergents use.
A preform is made by a “finish” (bottleneck), which will not change in the blowing process.
“Finish” diameter and thread type are the main features of the preform, features that determine the kind of screw bottle cap and the use of the bottle (for still water, sparkling water, oil, milk).
On the other hand, the tubular structure, will form the bottle in the blowing and molding processes and it determines the basis weights of the final product; diameter, length and shape are the key elements that give the main features to the blown container.
The PET polymer, used for the production of preforms doesn’t have a colour, it’s almost transparent, but once mixed with colouring additives, it can have different shades of colour according to customer requirements.

Storage

The polymer is transported in tankers or in Big Bags. The material, once entered into factory, is piped into 19 storage silos from which it’s taken depending on the production requirements.

Drying of PET

PET, by its nature, absorbs humidity from the atmosphere, in order to give a perfect product, it has to stand to a drying and dehumidification process. The process consists in maintaining the storage silo connected to the feeding of the PET machine for a certain period of time (which may vary depending on the nature of PET from 4 to 10 hours) during this time it’s heated with a stream of hot air at a temperature of 170°. The air heating is produced by a system that uses the thermal oil heated by a heat exchanger connected to a group of cogeneration for the production of electric power.

Plasticization of the PET

Once dried PET is routed through a screw in the injection chamber. During this phase, the PET is heated to a temperature of about 285° and stands to the lamination phase passing from the solid state (granules) to the liquid state.
Before entering into the cochlea the granule can pass through a pre-mixer where it’s mixed with a colouring that, with the specific amount, gives the shade as required by the customer.

Injection molding.

PET in liquid state is conveyed by the rotating screw in an injection chamber in such quantity as to fill the total cavity installed on the mold. When the mold is closed, the molten PET is injected into the cavities where once in contact with the matrix will solidify and form.
The temperatures of cavities and punches are cooled by a system that allows the PET to solidify before being ejected from the mold through a system of extractors.

Cooling

The solidification process ends when the preforms are ejected from the mold by a cooled automated gripper.

Packing

Once completed the cycle of cooling, the preforms are deposited on conveyor belts and sent in suitable containers called OCTABINS.

Handling and Storage

The OCTABINS are taken by an automated system made by 3 AGV shuttles and stored in the warehouse ready to be shipped, a dynamic system that effectively ensures full compliance with the hygiene standards required in the transformation process.