How Do Melt-Phase PET Bottle Resin Lines Handle SIBUR (Polief) PTA?

Bottle-grade polyethylene terephthalate is produced from purified terephthalic acid and ethylene glycol by direct esterification rather than DMT transesterification. The PTA-to-MEG molar charge in the paste preparation system is maintained between 1:1.15 and 1:1.20 before recycle ethylene glycol is introduced; this corresponds to a PTA mass fraction of approximately 69–70 wt% in the initial monomer feed. Antimony trioxide is added at 190–250 ppm Sb on polymer yield, and a phosphorus-based stabilizer is introduced after esterification at 10–40 ppm P. Esterification proceeds at 260–270°C and 1.0–1.7 bar in agitated vertical reactors; polycondensation follows at 275–285°C under 0.5–1.5 mbar absolute. The resulting amorphous melt is pelletized and then solid-state polymerized to an intrinsic viscosity of 0.80–0.84 dL/g measured by ASTM D4603-18. Free acetaldehyde in the finished pellet is held below 1 ppm to meet preform injection requirements; preforms are injection molded with barrel temperatures of 270–290°C and stretch blow molded at reheating temperatures of 100–115°C. Production-scale lines monitor water content in the recovered ethylene glycol stream; a shift from 0.2 wt% to 1.0 wt% can alter diethylene glycol formation and downstream preform color. Food contact compliance is governed by FDA 21 CFR 177.1630 and EU Regulation 10/2011, with migration testing under EN 1186-1 where applicable; supplier documentation should confirm 4-carboxybenzaldehyde below 25 ppm and p-toluic acid below 150 ppm per ASTM D8062-23 or GB/T 32685-2016. Finished article categories include carbonated soft drink bottles, still water containers, edible oil containers, and hot-fill beverage containers.

In staple fiber manufacturing, the same PTA is processed through a continuous polyester melt train but the final polymer design differs from bottle grade in melt viscosity, diethylene glycol tolerance, and delustrant loading. The esterification formulation uses a PTA-to-MEG molar ratio of 1:1.18–1:1.25; titanium dioxide suspension is metered into the paste or prepolymer at 0.3–0.5 wt% TiO₂ on polymer mass to produce semi-dull or dull fiber luster. After polycondensation to an intrinsic viscosity of 0.64–0.68 dL/g, the melt is filtered through 20–40 µm pore size screen packs and extruded through spinnerets at 285–295°C. Filaments are cooled by quench air at 16–20°C and 45–55% relative humidity, drawn in multiple stages to a total draw ratio of 3.0–4.5, crimped, and cut. A spin finish is applied at 0.1–0.3 wt% on the tow. Diethylene glycol content is held below 1.2 wt% to preserve tensile strength and dye uptake. Textile-market conformity requires REACH Annex XVII, OEKO-TEX Standard 100 product class II for direct skin contact, and ISO 105-B02 for light fastness when package-dyed or solution-dyed. Commercial PTA supplies typically show bulk density between 700–900 kg/m³ and mean particle size between 100–180 µm; these values support dense-phase conveying and slurry mixing. Published data for SIBUR (Polief) PTA performance in staple fiber lines is limited to general industrial practice. Final fiber outputs include needle-punched nonwoven staple, geotextiles, automotive interior textiles, and high-loft filling fiber.

Biaxially Oriented Film Resin from High-Purity TPA Feedstock

Film-grade PET derived from PTA is subjected to a stricter diethylene glycol ceiling than bottle resin because even 0.1–0.2 wt% excess DEG shifts the crystallization rate and can generate film haze after biaxial stretching. The molar charge ratio of PTA-to-MEG is controlled at 1:1.15–1:1.18, and silica slip additive is introduced at 0.1–0.3 wt% on polymer. Polymerization proceeds in a continuous train to an intrinsic viscosity of 0.63–0.68 dL/g; the pellet is then dried to below 50 ppm moisture at 160–170°C for at least 4 h before extrusion. Extrusion takes place at 270–280°C through a flat die onto a chilled casting drum held at 20–30°C, followed by sequential or simultaneous biaxial orientation at machine-direction draw ratios of 3.0–4.0 and transverse-direction draw ratios of 3.5–4.5 with stretching temperatures between 95°C and 115°C. Heat setting at 210–225°C stabilizes film dimensions. Electrical and food-contact grades are verified against IEC 60674-3-2, FDA 21 CFR 177.1630, and EU Regulation 10/2011, with overall migration verified by EN 1186-1. Converted film grades are supplied as flexible packaging laminates, capacitor dielectric film, thermal transfer ribbons, and photovoltaic backsheet core layers.

When PTA is routed into polybutylene terephthalate production, direct esterification with 1,4-butanediol proceeds under narrower thermal control than PET because tetrahydrofuran formation accelerates sharply above 225–230°C in the presence of acidic species. The formulation charge is a PTA-to-BDO molar ratio of 1:1.3–1.5, with tetrabutyl titanate added at 50–120 ppm Ti. Esterification is operated at 220–230°C under atmospheric pressure or slight vacuum, and polycondensation follows at 245–255°C below 1 mbar. PTA for PBT must have low 4-carboxybenzaldehyde and p-toluic acid content to limit color body formation; typical incoming specification flags 4-CBA below 25 ppm. The resulting PBT compound is often mixed with 20–30 wt% glass fiber on a twin-screw extruder with an L/D ratio of 40:1 and barrel temperature profile of 230–250°C. Injection molding of PBT parts uses melt temperatures of 250–265°C and mold temperatures of 60–90°C. Material qualification for electrical and automotive parts requires UL 94 V-0 flame rating, ISO 527-2:2012 for tensile modulus, and ASTM D648-16 for heat deflection temperature. Molded article applications include high-temperature electrical connectors, automotive sensor housings, power tool housings, and pump impellers.

When DOTP Replaces Ortho-Phthalates in Flexible PVC Compounding

Conversion of PTA to dioctyl terephthalate proceeds by direct esterification of two moles of 2-ethylhexanol per mole of terephthalic acid, with the alcohol charged in a molar ratio of 1:2.1–1:2.3 to drive the reaction to completion; this corresponds to a PTA mass fraction of roughly 36–38 wt% in the initial reactant mass. A titanium alkoxide catalyst is used; the reaction is run at 180–220°C under reflux with continuous water removal, followed by neutralization, washing, and vacuum stripping to leave a plasticizer with acid value below 0.1 mg KOH/g and moisture below 0.1 wt%. In flexible PVC dry blends, DOTP is added at 40–80 phr depending on Shore hardness: soft wire and film compounds use 60–80 phr, while harder profiles use 40–50 phr. The dry blend is mixed in a high-speed mixer to 100–120°C before twin-screw extrusion or injection molding. DOTP is not an ortho-phthalate and falls outside the current REACH Annex XVII entries that restrict certain phthalate plasticizers. Plasticizer quality acceptance testing uses ASTM D1045 for acid content and ASTM D257 for volume resistivity, with a typical volume resistivity above 1×10¹² Ω·m in PVC insulation. End-use PVC articles include building wire insulation, vinyl flooring, automotive interior skins, and garden hose compounds.

Powder Coating Polyester Resins Proceed via Acidolysis with Terephthalic Acid

For powder coating polyester resins, PTA content is balanced against neopentyl glycol and trimethylolpropane to raise the glass transition temperature of the cured film without generating excessive melt viscosity. Typical PTA addition is 25–45 wt% of total resin solids, with neopentyl glycol supplied in molar excess to control acid value and hydroxyl number. The synthesis is a two-step melt polycondensation in a batch reactor under nitrogen; the first step drives out water while the second step is held at 230–250°C under reduced pressure until the acid value reaches 20–35 mg KOH/g and the softening point reaches 100–110°C. The solidified resin is ground with a curing agent, either TGIC at 93:7 weight ratio or β-hydroxyalkylamide at 95:5, then extruded, milled, and classified to a particle size distribution with mean diameter 30–45 µm. Finished powder coatings are applied electrostatically and cured at 180–200°C for 10–20 min. Architectural powder coating specifications are governed by Qualicoat Class 1 or Class 2 and ISO 8130-5 for gelling time; exterior-durable coatings are tested for UV resistance by ASTM G154. Coated article categories include aluminum window profiles, ceiling panels, outdoor furniture coatings, and automotive underhood components.