Acrilyc DMAc Process

PROCESS CHARACTERISTICS

 

The DMAc process features the polymerization reaction in aqueous suspension, followed by the drying of the polymer obtained from water slurry and, after its dissolution in DMAc solvent, by the spinning of the polymer.

The polymerization in water offers the advantage of a higher reaction rate, meaning smaller reactor volumes if compared with the other process.

A further advantage consists of having an intermediate storage of dried polymer, which provides for high flexibility.

This allows polymerization and spinning to remain independent. In fact the spinning lines can also be fed continuously during the polymerization shut-down for reactor cleaning and maintenance.

 

PROCESS DESCRIPTION

 

Polymerization

The polymerization mixture consisting of AN and VA is continuously prepared by dosing the fresh monomers together with the recovered ones in the storage tank.

The polymerization reaction takes place in agitated reactors, in parallel. The catalyst is of redox type. The reaction temperature is kept constant, while a proper dwell time and suitable water-monomer ratio are maintained.

The slurry produced in the reactor is fed to a stripping column, where the polymer is separated from the residual monomers; the latter are then recycled to the monomers mixture preparation.

The polymer collected at the bottom of the stripping column undergoes a double filtration through vacuum rotary filters to remove most of the water.

The residual water is completely removed from the wet polymer by means of a proper drying system.

The dried polymer is stored in suitable storage bins, from where it is continuously fed, together with the DMAc solvent, to a vessel, where the polymer dope is prepared.

The dope undertakes a filtration and, after the dosing of additives and a further filtration to remove the last impurities, is sent to the spinning department.

 

Spinning

The main characteristics of the spinning line (one-front type) is the simplicity and the reliability.

The washing modules feature a specially designed device which allows a thorough washing of the tows.

Thanks to the proper setting of temperatures in the washing section the stretching of the tow is obtained with a minimum utilization of mechanical devices.

After the washing and the stretching the fibre is treated with application of finishing product, then it is dried under tension in a calender type dryer, then crimped and finally collected in cans.

A discontinuous annealing is mandatory to remove the high residual shrinkage so as allowing high flexibility towards different fibre types for different end uses.

 

Circulation of spinning bath and solvent recovery

The solvent is recovered in a triple effect evaporation plant. The water DMAc solution coming from the spinning plant is fed to the third effect where the complete separation of DMAc from water is carried out; the DMAc is sent back to the process.

The bottom products from the solvent recovery plant are sent to the solids removal system.

 

© Ing. A. Maurer S.A.

 

 

 

 

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