Influence Of PET Recycling Machine And Cleaning Process On Melt Filter

PET, as a renewable resource, has now been widely used in the regeneration of polyester filament, staple fiber, polyester film and food grade, bottle grade and packaging raw materials, and the dosage is still growing rapidly.  With the intensification of market competition, the demand for sustainable development strategy of global brand manufacturers, the demand for recycled PET application is increasing, and also the emphasis on the quality of PET products is increasing day by day.  

Whether it is food grade regenerated slices, or ultrafine fiber grade application of ester particles, all need to be from the PET whole bottle after consumption, through a series of cleaning process, to produce clean bottle slices, and then through granulation processing into slices.  With the continuous improvement of granulation technology, the accuracy of melt filter is also greatly improved. For the downstream recycled PET bottle level application of slice production needs 40-60μm filter sieve, ultra-fine denier filament grade slice requires impurity filtering accuracy of 15-20μm.  In such a precise dimension, the impurities mentioned above are the main factors causing the decline of the life of the melt filter.  

Compared with Virgin PET granulation, the melt mesh changer/filter, filter or component replacement cycle is short and the frequency is high, which increases the production cost and material loss, and the stability of physical property index is poor, including viscosity uniformity, slice hue and so on.  In the production process from recycled PET bottle flakes to slices, the removal of impurities in the cleaning process has a great influence on the service life of the melt filter in the later pelleting process.  In the PET cleaning section, as much as possible to remove the impurities in the bottle chip, will greatly improve the service life of the melt filter and the quality of the finished product.  

The influence of different impurities on the melt filter

The amount of dirt attached to the surface of polyester bottle chip is high, inorganic impurities and polyolefin are mixed in the bottle chip.  Inorganic impurities, such as mud, sand, metal directly plug the filter, polyvinyl chloride in polyester melting temperature to form carbide, partly plug the filter and components, part of the screw is crushed and mixed in polyester fiber whiteness.  Polyethylene, polypropylene during polyester melt, part of the formation of condensed particles clogged filters and components, the glue bottle did not wash the surface in the processing temperature of 270 ℃ or so mass of carbide, clogged filters and components, not clean the surface of the oil, sugar, mould at high temperature, make polyester crosslinked, forming condensed particles clogged filters and components.   

The effectiveness of PET bottle recycling and cleaning process for impurity removal:

Dry trommel screening:

sand, stone, small pieces of metal, etc., can be through the drum screen, dish screen or to cover the screen and other equipment directly without water sieve. 

Label remover:

PET bottle label in heat shrinkable labels, not through the bottle cleaning to wash it, and heat shrinkable labels for PVC material, special heat shrinkable label marking machine, a blade of special design, can have longer wear resistance and excellent scale efficiency, and the characteristics of low damage bottles, can remove the tags at the same time, reduce the loss of PET raw material;  

Whole bottle pre-washing:

stubborn mud stains, sticky labels, self-adhesive labels, etc., can be injected into the whole bottle pre-washing equipment with hot agent water heated to 85 degrees C, and most of them can be removed through a certain time of drum cleaning;  

The hot washing unit generally contains the following functions:  

Stir and clean with PET flakes hot washing 

Cold water floating washing  

Strong friction cleaning washing

Through the above cleaning process, due to adhesive attached to the bottle body PP label and paper label, these adhesives and small impurities mixed in the bottle sheet will have an important impact on PET recycling.  Hot agent stirring will soften the glue, high-speed eddy current will use the force of the vortex to separate the label and glue from the bottle sheet.  The role of the friction machine is to separate these adhesives and small impurities from PET bottles by friction and centrifugation, so as to obtain more pure raw materials.  

Air separation dust removal unit:

through negative pressure gas extraction, the film type of plastic (such as BOPP, PVC, PET, LDPE, etc.) and dust impurities are separated, the film and fine impurities to a minimum;  The usual form is Z type air separator.  

Metal separation unit:  

There are a variety of devices for metal detection and separation, which may include:  

Magnetic separation device: it can be in the form of magnet block, hanging iron strip and iron drum. Iron metal in the material will be absorbed by magnetic force and separated from the material.  

Pass-through metal detector: During material handling, this detector can be installed to detect whether metal is mixed.  When metal is detected, it can be removed manually by stopping material movement or automatically removed by a linkage mechanism.  

Eddy current sorting: automatic separation equipment for non-ferrous metals;  The high-speed magnetic roller repulses the non-ferrous metal (mainly aluminum) and changes its direction of travel to separate it from the raw material.  

Optical sorting:  

Automatic sorting equipment using spectroscopic detection and camera technology is often used in the plastic recycling industry to distinguish metals, non-PET plastics and miscellaneous plastics in raw materials and automatically remove them using high-pressure injection devices.  This technology has corresponding design devices for the plastics before and after crushing, which can avoid the impurities caused by human negligence to the greatest extent.  

About ReTech

We are committed to PET recycling and have more than 15 years of equipment manufacturing experience.  ReTech offers a full range of plastic recycling and cleaning systems, total solutions for polyester staple and textile equipment, as well as bottle-to-bottle equipment supply and engineering services.  If you have any need for plastic recycling machine, please do not hesitate to contact us.