BOPP is a biaxially oriented polypropylene film designed for flexible packaging and label applications.

The production process of BOPP is based on the main extruder forwarding hot melt through the filter required to prevent foreign particles and other waste from getting into the die. The die spreads the melt over the surface of the chill roll rotating in the water bath. Melt for external layers comes from coextruders connected with the die through the filter. The film takes shape while being stretched from the die through the casting unit.

Then comparatively thick film goes through heating rolls and up there to the machine direction orientatier (MDO). There film is stretched in the longitudinal direction. Then  film is caught with the clips and forwarded to transverse direction orientier (TDO) to be stretched in the transverse direction and chilled. Film comes through a number of thermal zones to get required properties.

After leaving TDO film goes to PRS-unit where the edge trim is being cut, film thickness is being measured by a special gauge, film surface is being corona treated to acquire tension.

Then film goes to the winder to be winded. Finished rolls are stored  for 24 hours in the mill roll area before slitting.

 

Coextrusion

Coextrusion is a process of producing multi-layer materials which is a combination of several polymeric layers at a given production cycle.

Coextrusion makes possible to produce wide range of film types with various properties which can’t be acquired when film is produced by means of ordinary mono-layer extrusion.

Coextrusion method contributes to production of the so-called barrier films serving as a barrier to gas and moisture as well as providing for required chemical and mechanical stability, shrinkage, rupture, impact and puncture resistance, sealability, resistance to thermal effect, elasticity or stifness, aroma  barrier, etc.

Coextrusion method is rather efficient for it decreasing production costs by allowing to use less expensive polymers and regranulate in the inner layers of film. More over it takes place during one production cycle.

On its DMT line Biaxplen produces mono-layer films as well as three-layer coextruded films.

At present Biaxplen has purchased the 2nd line capable to produce seven-layer coextruded  BOPP films. A new line will be installed next 2007 year.

 

Additives

Additives are used to give film a number of special  properties.

Slip additives are friction modifiers.

Anti-block additives reduce the coefficient of friction and prevent self-adhesion of film for easier handling.

Anti-static additives enchance anti-static properties.

Anti-fog agents prevent condensating  on the film surface  by high humidity.

Optical brightners increase gloss and transparency, improve a number of mechanical properties.

Compound additives have a  systematic impact.

Films need to be modified in order to improve properties such as barrier, transparency, stiffness, twist retention and so on.

Additives contribute to the production of innovative films with added value.