The PET Crystallizer SCR Improvement

PET, with its scientific name polyethylene terephthalate, is also called Dacron, polyester. Featuring excellent resistance of gases, resistance to pressure, shock resistance, transparency and surface gloss, it is widely used in food containers with traits of odorlessness fragrance conserve, the safety of the food hygiene, beautiful shape and easily-forming. It has density of 1.4kg/L, melting temperature of 245℃,and molding temperature between 290℃ and 315℃. Its grain bulk density fluctuates between 0.8 to 0.85kg/L, sheet bulk density between 0.38 to 0.4kg/L. 

PET mainly employed to produce synthetic fiber, PET bottle and thin sheet. With the development of economy in recent years, people’s awareness of environmental protection is under enhancement. Thus PET sheet, as a kind of packaging material shows the favorable development potential as the alternative to replace difficult-recyclable PVC packing material. 

There’re various kinds of PET. When non-crystallized PET contacts with high temperature, it would conglutinate. Crystallize PET can prevent material from conglutinating in high-temperature drying, which usually ways of mixing and uses air flow to make PET boiling in the process. 

The function of crystallizing is to crystallize PET and increases its melting temperature. It prevents PET from lumping at the end of heating process. The non-crystallize PET is usually completed by crystallizer with crystallizing temperature at 120℃~160℃. The heating time is 1~2hr, the pre-crystallization process isn’t finished until PET lost the transparency. PET is heated at even higher temperature after crystallizing process to get rid of the residual moisture. For example, at drying temperature of160℃, the moisture contained in PET would below 0.05% after 4~6 hours rested in the dehumidifying dryer. It helps to avoid PET hydrolysis at high temperature which may lead to molecular weight and the viscosity drops down rapidly in extrusion granulating process afterwards.

Shini PET crystallizer standard equipped with the pre-heating function and constant-speed mixing device which could effectively process crystallizing towards non-crystallized PET materials. It avoids conglutinating in high temperature and improves PET product’s quality. 

In order to enhance the performance of PET crystallizer, ensure machine’s operation as well as machine’s convenient maintenance. We improved the structure of mixing components for the PET crystallizer as below:

The gear motor changed to mixing specialized gear motor with strengthened bearing at output-shaft end. This strengthened bearing not only can bear even much radial load as well as axial load but also can compensate the angle deviation in some degree, which especially good for long mixing shaft application. Compared with previous gear motor, it can bear much more load and with safer coefficient which ensures steady and reliable mixing components.

Remove the middle bracket and bearing of barrel mixing components. It not only simplifies the processing technique and the assembly procedure, but also lowers the wearing of mixing internal components and makes convenient maintenance afterwards as well.

As to prevent the material at hopper bottom from bridge-breaking, the mixing blade at bottom also be lengthened which ensures material discharging smoothly.

The modified PET crystallizers are in stable, safe and reliable operation, and machine’s maintenance is more convenient afterwards. All of these can satisfy the quality, safety and maintenance requirements from the customer, which established the solid foundation of the machine for future clients.