Dioctyl Terephthalate (DOTP) has emerged as one of the most important non-phthalate plasticizers in the modern plastics industry. This comprehensive guide explores our advanced production technology and quality control systems for premium DOTP, manufactured at Shandong Changxing's ISO 9001:2015 certified facility.
Chemical Reaction Principle
The production of DOTP involves the esterification of terephthalic acid with 2-ethylhexanol in the presence of a titanium-based catalyst. The overall chemical reaction can be represented as:
C₆H₂COOH)₂+ 2 C₈H₁₇OH →C₆H₂COOC₈H₁₇)₂+ 2 H₂O
(TPA) + (2-Ethylhexanol) →(DOTP) + (Water)
Manufacturing Process Overview
Raw Material Selection and Quality Control
The production of high-quality DOTP begins with careful selection and testing of raw materials according to strict specifications:
- Terephthalic Acid (TPA): Purity ≥9.9%, moisture content <0.1%, particle size optimized for rapid dissolution
- 2-Ethylhexanol (2-EH): Purity ≥9.5%, water content <0.1%, distillation range within 1°C
- Catalyst System: Proprietary titanium-based catalyst (tetrabutyl titanate), concentration precisely controlled at 0.05-0.15% by weight
Esterification Reaction Stage
The core of our DOTP production involves a carefully controlled continuous esterification process in multi-stage reactors:
- Temperature Control: Precisely maintained at 220-250°C using advanced PID controllers with ±0.5°C accuracy
- Pressure Management: Operated under vacuum conditions (-0.08 to -0.095 MPa) to facilitate water removal
- Reaction Time: Optimized residence time of 4-6 hours for complete conversion (>99.8%)
- By-product Removal: Continuous azeotropic distillation removes water, driving equilibrium toward product formation
- Nitrogen Blanketing: Inert nitrogen atmosphere prevents oxidation and maintains product color stability
Purification and Finishing
After esterification, the crude DOTP undergoes multiple purification steps:
- Neutralization: Residual acidity neutralized with sodium carbonate solution
- Stripping: Unreacted alcohol removed under high vacuum (<1 mmHg) at 180-200°C
- Filtration: Multi-stage filtration through 10μm, 5μm, and 1μm cartridge filters
- Quality Testing: Every batch tested against 15+ quality parameters before release
Comprehensive Quality Parameters
Our DOTP product meets or exceeds international industry standards including ASTM D5208 and ISO 10502. For a detailed comparison between premium grade and qualified grade DOTP, see our premium DOTP specifications guide.
| Parameter | Premium Grade | Qualified Grade | Test Method |
|---|---|---|---|
| Ester Content | ≥8% | ≥8% | GC (ASTM D5208) |
| Color (APHA) | ≥50 | ≥50 | ASTM D1209 |
| Acidity (% as TPA) | ≥.035 | ≥.035 | ASTM D974 |
| Moisture Content | ≥.1% | ≥.1% | Karl Fischer |
| Density (20°C) | 0.980—.985 g/cm³ | 0.980—.985 g/cm³ | ASTM D4052 |
| Volume Resistivity | ≥×10¹² Ω·cm | ≥×10¹² Ω·cm | ASTM D257 |
| Flash Point | ≥10°C | ≥10°C | ISO 2592 |
Key Application Areas
DOTP's superior properties make it the preferred choice for demanding applications across multiple industries:
- PVC Wire and Cable Compounds: Excellent electrical insulation properties (volume resistivity ≥×10¹² Ω·cm), low volatility ensures long-term performance. Learn more about DOTP in wire and cable applications.
- Medical-grade Flexible PVC: Non-phthalate formulation, biocompatible, complies with EU REACH and FDA regulations
- Food Packaging Films: Low migration rate, odorless, suitable for direct food contact applications
- Synthetic Leather Production: Superior flexibility at low temperatures (glass transition temperature <-40°C), excellent abrasion resistance
- Automotive Interior Materials: Fogging resistance, UV stability, meets OEM specifications for interior components
- PVC Flooring: Non-phthalate compliance for indoor air quality, meeting global flooring regulations
References and External Resources
- ASTM International —Plasticizer Test Standards
- ISO 9001 —Quality Management Systems
- PubChem —Dioctyl Terephthalate (DOTP)
Conclusion: Advanced Technology Ensures Consistent DOTP Quality
Shandong Changxing's DOTP production technology combines continuous esterification with titanium-based catalysis, multi-stage purification, and rigorous quality control to deliver plasticizers that meet the highest international standards. Key advantages include:
- High conversion efficiency (>99.8%) through optimized temperature and pressure control
- Consistent batch quality via 15+ parameter testing and full DCS automation
- Circular economy integration —waste PET recycling into DOTP reduces environmental impact
- Comprehensive regulatory compliance —REACH registered, FDA compliant, SGS triple-tested
Frequently Asked Questions
What is the production process of DOTP?
DOTP is produced through continuous esterification of terephthalic acid (TPA) with 2-ethylhexanol using a titanium-based catalyst at 220-250°C under vacuum. The process includes raw material purification, multi-stage esterification, neutralization, high-vacuum stripping, and multi-stage filtration to achieve ester content ≥98% and volume resistivity ≥2×10¹² Ω·cm.
What catalyst is used in DOTP production?
Tetrabutyl titanate (TBT) is the primary catalyst, used at 0.05-0.15% by weight. This titanium-based catalyst provides high selectivity and conversion rates exceeding 99.8%, while producing minimal side reactions compared to traditional acid catalysts.
What are the key quality parameters of DOTP?
Key DOTP quality parameters include ester content (≥98%), color/APHA (≤150 for premium grade, ≤450 for qualified grade), acid value (≤0.035% as TPA), volume resistivity (≥2×10¹² Ω·cm), flash point (≥210°C), and moisture content (≤0.1%). Each batch is tested against 15+ parameters before release.
What is the difference between PET-based and TPA-based DOTP production?
TPA-based production uses virgin terephthalic acid as feedstock, while PET-based production recycles waste PET plastic through transesterification with 2-ethylhexanol. Both routes yield chemically identical DOTP. The PET route supports circular economy and reduces landfill waste. Learn more in our PET-to-DOTP recycling article.
What production capacity does Shandong Changxing have for DOTP?
Shandong Changxing group's total DOTP production capacity reaches 450,000 metric tons per year, including the 150,000-ton Wan Sheng facility using continuous esterification technology with fully automated DCS monitoring and ISO 9001:2015 certified quality management.
Source Premium DOTP from a Leading Manufacturer
Shandong Changxing Plastic Additives operates a state-of-the-art facility with a group annual production capacity of 300,000 metric tons of DOTP, manufactured under ISO 9001:2015 certified processes using continuous esterification technology with fully automated DCS monitoring.
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