The preform of the bottle blowing machine
Blow Molding Machine? Hollow blow molding machine? Preform mold? You should be aware of these products. What I want to introduce to you today is the related knowledge of the product blow molding machine-preform. If you are also troubled by this problem, then the following introduction hopes to help you.
The preform of the bottle blowing machine is also called the parison. It is made of PET pellets by injection molding. It requires that the proportion of recycled materials cannot exceed 10%, and the number of recycling cannot exceed twice. The preform after injection molding or the preform used after heating must be cooled for more than 48 hours, and the storage time of the used preform cannot exceed 6 months. Different production dates, especially preforms with too long intervals, cannot be mixed, the main reason is The type of raw material used in the preform, the proportion of the mixed secondary material and the residual stress in the preform are different. These factors have a significant impact on the molding process of the bottle blowing, and should be treated according to the actual situation. Because PET has strong water absorption, special attention must be paid to moisture prevention during storage, and it must be effectively dehumidified and dried before processing. The drying conditions are usually 150～180℃ for 4 hours, and in order to prevent the plastic particles from absorbing moisture again, it must be Keep the temperature above 140℃. In order to prevent the plastic from turning yellow when shutting down, the desiccant dryer needs to be cooled to 100℃ without dehumidification and only keep warm. In addition, if the material temperature is too high, the screw shearing force is too high, or the rotation speed is too fast during PET injection molding, acetaldehyde is likely to be produced and cause acidification. Generally, the acetaldehyde content of the PET bottle after molding must be less than 3ppm, and the preform is before crystallization. A certain moisture content is required, generally about 1000 ppm, and at least 900 ppm or more. Therefore, the preform needs to be placed for a period of time before it can be crystallized after the moisture content reaches the required moisture content.