Polyester; PET polyester, whose chemical name is polyethylene terephthalate, was discovered by Whinfield and Dickson and was first commercially produced in 1941. Hoechst, Du Pont and Eastmann are the world’s largest companies producing polyester. The growth in the production of polyester fiber will increase further in the very near future. Polyester fiber is a very important fiber in the world. Although it was not used much at first, its use has become widespread and developed further over time. As the fiber itself has been developed, the dyeability properties of the fiber and new dyeing methods h

 

Production of Polyester Fiber

Today, polyethylene terephthalate (polyester) is produced in two ways in the world.

DMT + MEG – PET + Methanol
TPA + MEG PET + Water
PET production from DMT (dimethylterephthalate) and ethylene glycol is the oldest method in this field. Here, DMT and MEG are recharged or continuously polymerized.

a) Esterification Reaction:
b) Polycondensation Reaction:
The continuous process has technological and economic advantages over the charging process. As it is known, many foreign substances are formed as undesirable by-products during polycondensation. Diethylene glycol (DEG) comes first among these. The main factors in the formation of DEG are temperature, residence time of the components in the reactor, glycol concentration and catalysts. The amount of by-products in question can be minimized by selecting the operating conditions in the continuous process in the most appropriate way. In addition, the homogeneity of the polymer obtained in the continuous process is better than the charging process. In the charging method process, 

In the charging method process, the difference between the two charges is more pronounced. Another important point is that the standard capacities in the continuous process are higher than the charging process. In the charging process, the polymer is first isolated as chips

Then it is melted and pressed into production manifolds for fiber production. In the continuous process, the polymer is pressed directly into the production manifolds without the chips forming phase. Today, this is the preferred way, especially in staple fiber production facilities.

The first PET facilities established in our country have applied the charging method process. However, in some newly established facilities, a continuous polymerization process has been applied to provide more economical operating conditions.

As for the production of PET from pure terephthalic acid; Due to the difficulties in producing pure TPA, DMT was used in production for the first time. However, the small molecular weight of TPA compared to DMT and therefore the polyester product corresponding to the unit raw material input is more, and the formation of less problematic water instead of methanol as a by-product in the reaction encourages studies to obtain TPA with sufficient purity. has.
Today, the rate of increase in the use of TPA in PET production is higher than DMT. In PET production, pure TPA and MEG are polymerized by charging method or continuously, as in DMT. Again, as in processes using DMT, the continuous polymerization process is more economical and technologically superior than the charge method process.

Fiber Production

Two ways are used to produce staple fibers. These ;

Production from Chips (Indirect Production)
This old method of production often applies a charge polymerization method.
It is used in facilities. In continuous processes, the direct production method, which is considered to be more modern, is preferred for staple fiber production.

It comes from the chips feed boiler to the dryer and from there to the extruder. The polymer melted under nitrogen atmosphere in the extruder is pressed into the production manifolds with the help of a spiral. After that, the polymer is sprayed from 1200 perforated nozzles and cooled by a constant temperature and speed air flow. Cables are formed by combining solidified fibers with an antistatic material.The cables are lined up in creels in the gater circle. The stacked fibers are passed through hot oil baths for drafting. Later, it is passed through the crimping unit in order to obtain the curl feature of natural fibers. After the fixing unit, it is cut in various lengths and baled. During the process, the fiber has a fixed cross-section and internal structure that can be used in textiles. The next process consists of finishing the fiber. The product is evaluated as TOPS or TOW.

 

Polyester Yarn Production

Chips Production
Polyester chips come to the dryer and from there to the extruder. From here, the melting polymer is pressed into the production manifolds. It is sprayed from nozzles and frozen with cold air and wrapped in bobbins by lubricating with special preparations. Production speed is 3200-4000 m / min. The production speed reaches 4000-6000 m / min in the newly developed high speed production machines.
Yarns wrapped in bobbins (POY-Preoriented Yarn) are subjected to denier control and pre-control process. POY yarns are supplied to textile machines to be produced as texturized or flat yarn.

Direct Production
Here, the melt polymer coming out of the last polycondensation boiler is filtered and directly pressed to the production manifolds. ^ The next processes are as in the technology of producing yarn from chips.