To get an idea about coverage, importance and complexity of the polyester industry, some basic information about polyester or polyethylene terephthalate (PET) at first:
What is polyester? Polyester is a synthetic polymer made of purified terephthalic acid (PTA) or its dimethyl ester dimethyl terephthalate (DMT) and monoethylene glycol (MEG). It ranges after polyethylene and polypropylene at the third place in terms of market size.
The main raw materials are described as follows:
- Purified Terephthalic Acid – PTA – CAS-No.: 100-21-0
Synonym: 1,4 Dibenzenedicarboxylic acid,Sum formula; C6H4(COOH)2 , mol weight: 166,13
- Dimethylterephthalate – DMT- CAS-No: 120-61-6
Synonym: 1,4 Dibenzenedicarboxylic acid dimethyl esterSum formula C6H4(COOCH3)2 , mol weight: 194,19
- Mono Ethylene Glycol – MEG – CAS No.: 107-21-1
Synonym: 1,2 EthanediolSum formula: C2H6O2 , mol weight: 62,07More information about polyester raw materials one can find for PTA 
and MEG 
, at the webpage INCHEM "Chemical Safety Information from Intergovernmental Organizations".
To make finally a polymer of high molecular weight one needs a catalyst. The most common catalyst is antimony trioxide
(or antimony tri acetate)Antimony trioxide – ATO – CAS-No.: 1309-64-4
Synonym: non, mol weight: 291,51 Sum formula: Sb2O3
In 2008 about 10 000 t Sb2O3 are used to produce around 49 Mio t polyethylene terephthalate.
Polyester is described as follows:Polyethylene Terephthalate CAS-No.: 25038-59-9
Synonym / abbreviations: polyester, PET, PES Sum Formula: H-[C10H8O4]-n=60-120 OH, mol unit weight: 192,17
What are the success factors of the unbroken capacity growth of polyethylene terephthalate?
- The relatively easy accessible raw materials PTA or DMT and MEG
- The very well understood and described simple chemical process of polyester synthesis
- The low toxicity level of all raw materials and side products during production and processing
- The possibility to produce PET in a closed loop at low emissions to the environment
- The outstanding mechanical and chemical properties of polyester
- The recycle ability
- The wide variety of intermediate and final products made of polyester
All these facts are making this polymer one of the key elements of our daily life.
In table 1 we see the estimated world polyester production for textile
polyester, bottle polyester resin, film polyester mainly for packaging
and specialty polyesters for engineering plastics, which are the main fields of application. According to this table, the world's total polyester production might exceed 50 million tons per annum before the year 2010.
Table 1: World polyester production
Market size per yearProduct Type
2002 [Mio t/a]2008 [Mio t/a]Textile-PET2039Resin, Bottle/A-PET916Film-PET1.21.5Special Polyester12.5TOTAL
With its production volume and product diversity, polyester ranges after polyethylene
(19,5%) with a market share of about 18% in third position among all plastic materials produced worldwide.
The polyester production chain, and the relative polyester industry chain, will now be explained in greater detail and step by step.
 Raw material producer
The raw materials PTA, DMT and MEG are mainly produced by large chemical companies which are sometimes integrated down to the crude oil refinery where p-xylene is the base material to produce PTA and liquefied petroleum gas (LPG) is the base material to produce MEG.
Large PTA producers are for instance BP, Reliance, Sinopec, SK-Chemicals, Mitsui and Eastman Chemicals. MEG production is in the hand of about 10 global players which are headed by MEGlobal a JV of DOW and PIC Kuweit followed by Sabic.
Let us assume the average production capacity of a single polyester plant is about 200 t/day: we are talking about nearly 500 polyester plants around the globe. Adding to this figure the continuously-growing polyester recycling industry, which is estimated to have processed about 3 million t polyester waste in 2007 alone (5 million T/a in 2010 estimated) and where each plant produces on average about 10 000 t/a, we have another 500 plants. This is 1000 polyester production plants, all needing specific and polyester-dedicated engineering and equipment, machinery, process technology and know-how, producing, processing and recycling polyester.
Among the world's largest polyester producers are the following companies:
Artenius, Advansa, DAK, DuPont, Eastman/Voridian, Hyosung, Huvis, Indorama, Invista, Jiangsu Sanfangxian, M&G Group, Mitsui, Mitsubishi, NanYa Plastics,Reichhold, Reliance, Rongsheng, Sabic, Teijin, Toray, Tonkun, Tuntex, Wellman, Yizheng Sinopec and Sanfanxiang.
One should notice that China's capacity to produce and process polyester in more than 500 plants is nearly half that of the world's polyester capacity meanwhile. More information about polyester in China can be found under the web site of China Chemical Fiber Economic Information Network .
 Polyester processing
After the first stage of polymer production in the melt phase, the product stream divides into two different application areas which are mainly textile applications and packaging applications. In figure 2 the main applications of textile and packaging polyester are listed.
Table 2: Textile and packaging polyester application list
POLYESTER-BASED POLYMER (MELT or PELLETS)TextilePackagingStaple fiber (PSF)Bottles for CSD, Water, Beer, Juice, DetergentsFilaments POY, DTY, FDYA-PET FilmTechnical yarn and tire cordThermoformingNon-woven and spunbondBO-PET Biaxial oriented FilmMono-filamentStrapping
Abbreviations: PSF = Polyester Staple Fiber; POY = Partially Oriented Yarn; DTY = Draw Textured Yarn; FDY = Fully Drawn Yarn; CSD = Carbonated Soft Drink; A-PET = Amorphous Polyester Film; BO-PET = Biaxial Oriented Polyester Film;
A comparable small market segment (<< 1 million t/a) of polyester is used to produce engineering plastics and masterbatch.
In order to produce the polyester melt with a high efficiency, high-output processing steps like staple fiber (50–300 t/d per spinning line) or POY /FDY (up to 600 t/d split into about 10 spinning machines) are meanwhile more and more horizontal, integrated, direct processes. This means the polymer melt is directly converted into the textile fibers or filaments without the common step of pelletizing. We are talking about full horizontal integration when polyester is produced at one site starting from crude oil or distillation products in the chain oil -> benzene -> PX -> PTA -> PET melt -> fiber / filament or bottle-grade resin. Such integrated processes are meanwhile established in more or less interrupted processes at one production site. Eastman Chemicals introduced at first the idea to close the chain from PX to PET resin with their so-called INTEGREX® process. The capacity of such horizontal, integrated productions sites is >1000 t/d and can easily reach 2500 t/d.
Besides the above mentioned large processing units to produce staple fiber or yarns, there are ten thousands of small and very small processing plants, so that one can estimate that polyester is processed and recycled in more than 10 000 plants around the globe. This is without counting all the companies involved in the supply industry, beginning with engineering and processing machines and ending with special additives, stabilizers and colors. This is a gigantic industry complex and it is still growing by 4–8% per annum, depending on the world region. Useful information about the polyester industry can be found under  where a “Who is Producing What in the Polyester Industry” is gradually being developed.
Synthesis of polyesters is generally achieved by a polycondensation reaction. See "condensation reactions in polymer chemistry". The General equation for the reaction of a diol with a diacid is : (n+1) R(OH)2 + n R´(COOH)2 ---> HO[ROOCR´COO]nROH + 2n H2O
 Azeotrope esterification
In this classical method, an alcohol and a carboxylic acid react to form a carboxylic ester. To assemble a polymer, the water formed by the reaction must be continually removed by azeotrope distillation.
 Alcoholic transesterification
See main article on transesterification.
O \ C - OCH3 + OH[Oligomer2] /[Oligomer1][IMG]http://upload.wikimedia.org/math/1/b/1/1b18a4c4fc578ef4cfd1cc0eb0daa473.png[/IMG] O \ C - O[Oligomer2] + CH3OH /[Oligomer1](ester-terminated oligomer + alcohol-terminated oligomer) (larger oligomer + methanol)
 Acylation (HCl method)
The acid begins as an acid chloride, and thus the polycondensation proceeds with emission of hydrochloric acid (HCl) instead of water. This method can be carried out in solution or as an enamel.
Silyl methodIn this variant of the HCl method, the carboxylic acid chloride is converted with the trimethyl silyl ether of the alcohol component and production of trimethyl silyl chloride is obtained
 Acetate method (esterification)
Silyl acetate method
 Ring-opening polymerization
Aliphatic polyesters can be assembled from lactones under very mild conditions, catalyzed anionically, cationically or metallorganically.