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PET bottle blowing process

Update:23-01-2021
Summary:

Beverage bottle is a modified PET bottle blended with p […]

Beverage bottle is a modified PET bottle blended with polyethylene naphthalate (PEN) or a composite bottle of PET and thermoplastic polyarylate. It is classified as a hot bottle and can resist heat above 85℃; water bottle is cold Bottle, no requirement for heat resistance. The hot bottle is similar to the cold bottle in the forming process.
1 equipment

At present, the manufacturers of PET full-automatic blow molding machines mainly import from France SIDEL, Germany KRONES, and domestically produced Fujian Quanguan Company. Although the manufacturers are different, their equipment principles are similar, generally including the blank supply system, heating system, blowing system, control system and auxiliary equipment.
2 Blow molding process

PET bottle blow molding process.

The important factors that affect the PET bottle blow molding process are the preform, heating, pre-blowing, mold and production environment.

2.1 Preform

When preparing a blow-molded bottle, firstly, the PET chip is injection molded into a preform. It requires that the proportion of secondary reclaimed material cannot be too high (below 5%), the number of retractions cannot exceed two, and the molecular weight and viscosity cannot be too low (molecular weight 31000- 50000, intrinsic viscosity 0.78-0.85cm3/g). According to the National Food Safety Law, secondary reclaimed materials shall not be used for food and medical packaging. The injection-molded preforms must be stored for more than 24 hours before they can be used. The preforms that are not used up after heating must be stored for more than 48 hours to be reheated for use. The storage time of preforms cannot exceed six months.

The quality of the preform largely depends on the quality of the PET materials. Materials that are easy to inflate and shape should be selected, and a reasonable preform molding process should be drawn up. Experiments have shown that the imported raw materials for preforms formed by PET materials with the same viscosity are easier to blow-mold than domestic materials; while the same batch of preforms has different production dates and the blow molding process may be quite different. The quality of the preform determines the difficulty of the blow molding process. The requirements for the preform are pure, transparent, free of impurities, no different colors, suitable for the length of the injection point and the surrounding halo.

2.2 Heating

The heating of the preform is completed by a heating oven, and its temperature is manually set and adjusted automatically. In the oven, the far-infrared light tube announces that the far-infrared radiates and heats the preform, and the fan at the bottom of the oven performs heat circulation to make the temperature in the oven uniform. The preform moves forward in the oven and rotates together to make the preform wall evenly heated.

The placement of the lamp in the oven is generally in the shape of a "zone" from top to bottom, with more ends and less in the middle. The heat of the oven is controlled by the number of open lamps, the overall temperature setting, the power of the oven and the heating ratio of each section. The opening of the lamp tube should be adjusted in conjunction with the pre-blowing.

To make the oven work better, the adjustment of its height, cooling plate, etc. is very important. If the adjustment is improper, it is easy to swell the bottle mouth (bottle mouth becomes larger) and hard head and neck (the neck material cannot be opened) during blow molding. And other defects.

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