PET …the most popular plastic today
Polythylene terepthalate or PET is one of the most popular packaging materials available today. PET being hygropscopic has a very high affinity towards moisture and so it is very important to dry it thoroughly and properly to ensure a quality finish.
Moisture a major irritant during PET processing
Moisture in PET if not reduced up to 0.003%, the residual moisture can change the molecular weight and IV value. This might lead to haziness in pre-form and other serious defects.
Silver streaking and splay are not the only defects caused by moisture, the more serious defects which are not visible are:
These serious invisble defects can result in major costs for the end user.
Hence, Bry-Air recommends drying of PET as the first critical step towards final quality of the moulded product.
Parameters of resin drying
Temperature – 160°C – 80°C
Time of Drying – 4-5 hr. CMH / Kg
Air Flor 205 CMH/Kg
Dew Point -40°C and below
Dew point plays a very critical role in creating a lower vapour pressure around the surface of the resin. This lower vapour pressure forces the moisture in the molecular chain of the resin to dissipate out to its surface.
Only Bry-Air dehumidifying Plastic Dryers can guarantee -40°C to -65°C as consistent dewpoint.
What happens it PET resins are dried at -20°C
The PET resins dried at -20°C dewpoint retain 10 times more moisture than PET resins dried at -40°C dewpoint.
Method of Bry-Air Resin Dryer with BryWheel
The generation next Bry Wheel rotor works on the principle of the Honeycomb technology which results in 25% more energy savings, 100% reliability and zero downtime. This ensures a much better control over dewpoint and temperature. This rotor is specially crafted for a very low dewpoint upto(-) 65°C. Other than this the rotor combines the advantages of maximum surface area for drying, higher efficiency, light weight, amazing structural strength, lower drying cost with unlimited options for stand alone, single station operation as well as multi station centralized installation.
The biggest challenge to PET moulders today is to run the machine at better cycle time. The most time consuming process in PET moulding cycle is cooling time. To bring the cooling time down as possible to refilling time (dosing time) the mould needs to be cooled with chilled water as low as possible. During this process of bringing down chilled water temperature of the mould, due to higher moisture surrounding the mould, condensation occurs. This condensation can lead to rusting of mould, water marks on pre form and pre-form not getting ejected out properly.
To prevent the condensation, the area around the mould needed to be maintained with Dry-Air at the dew point of minimum -10°C and less. Bry-Air offers the solution through Mould Dehumidification Systems-MDS and PMD where the dewpoint of the surrounding air around the mould can be maintained up to -10°C.
Dabur is manufacturer of the popular herbal hair oil “Dabur Vatika”. This herbal oil is packaged in PET bottles. Dabur has its own captive PET processing plant where PET bottles for packaging this new brand of oil are manufactured. Dabur uses Nissei moulding machines to process virgin PET resins and has installed Bry-Air Ecodry Dehumidifying Dryers, of different models, for ensuring proper drying of resins prior to processing.
Dabur has totally automated the conveying between the storage bins and moulding machines with a 4-station Bry-Air Centralised Conveying System. The system helps Dabur to save on time as well as labour, increase productivity and maintain a clean shop floor. The Bry-Air Centralized Conveying Systems provide all the benefits of a central system with the added convenience of portability, low maintenance and incorporation of the latest technical features. This complete Conveying System provides automatic loading (upto 8 stations) of 3000 lb/h (1350 kg/hr), and also for a maximum conveying distance upto 240 ft (73 metres).