Introduction of PET plastic bottle blowing process

Update: 2021/12/22

With the continuous progress of science and technology […]

With the continuous progress of science and technology and the scale of production, the degree of automation of PET blow molding machines is getting higher and higher, and the production efficiency is getting higher and higher. The production capacity of the equipment has increased rapidly, from the previous production of several thousand bottles per hour to the current production of tens of thousands of bottles per hour. The operation is also changed from the past manual and button-type development as the current full computer control, which greatly reduces the difficulty of the process operation and increases the stability of the process.

At present, the major manufacturers of PET automatic blow molding machines imported from abroad include SIDEL from France, KRONES from Germany, and Fujian Quanguan Quinko, etc., which are domestically produced. 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.

PET bottle blow molding process.

Important factors affecting the PET bottle blow molding process include preforms, heating, pre-blowing, molds, and production environment.

When preparing blow-molded bottles, the first PET chip injection molding is used as the preform. It requires that the proportion of secondary recycled materials must not be so high (below 5%), and the number of recycling must not exceed twice, so the molecular weight and viscosity must not be so low (Molecular weight 31000-50000, intrinsic viscosity 0.78-0.85cm3/g). According to the National Food Safety Law, secondary recycled materials shall not be used for food and medical packaging. The injection-molded preform needs to be stored for 24 hours to exceed its capacity. The preforms that are not used up after heating must be stored again for 48 hours to exceed the items before being reheated for use. The storage time of the preform must not exceed six months.

The pros and cons of preforms depend to a large extent on the pros and cons of PET materials. Materials that are easy to inflate and easy to shape should be selected, and a reasonable preform molding process should be formulated. Experiments have shown that the imported raw materials for PET preforms of the same viscosity are easier to be blow molded than domestic ones; and the same batch of preforms have different production dates, and the blow molding process may also be quite different. The pros and cons of the preform determine the difficulty of the blow molding process. The requirements for the preform are purity, transparency, no impurities, no different colors, the length of the injection point, and the proper surrounding halo.

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