1. Definition and Chemical Properties of Antioxidant TNP

Antioxidant TNP, chemically known as tris(nonylphenyl) phosphite (abbreviated as TNPP or anti-aging agent TNPP), is a highly efficient phosphite antioxidant. Its molecular formula is C₄₅H₆₉O₃P, with a molecular weight of 668 (some literature reports 689.03, possibly due to structural isomers).

At room temperature, TNP appears as a light yellow to amber viscous liquid with a freezing point of -19°C and a boiling point of 530–540°C. It is soluble in organic solvents such as acetone, ethanol, and benzene but insoluble in water. It decomposes easily in acidic media. Key characteristics include odorless, tasteless, low toxicity, and excellent storage stability.

2. Key Technical Specifications of TNP

Quality standards for TNP (e.g., enterprise standard Q/SFQ-005-2024) typically include the following parameters:

1. Color (Pt-Co scale): ≤250

2. Acid value (mg KOH/g): ≤0.3

3. Phosphorus content (%): ≥3.8

4. Refractive index (nD²⁵): 1.5230–1.5265

5. Relative density (d₁₅²⁵): 0.980–0.992

6. Viscosity (20°C): 2500–5000 mPa·s

Industrial production also focuses on yield (90–95%) and free nonylphenol content (≤7%).

3. Applications of Antioxidant TNP

Due to its excellent antioxidative performance, thermal stability, and non-polluting properties, TNP is widely used in:

1. Synthetic Rubber & Latex

   • Acts as a stabilizer, inhibiting gelation during rubber processing and preventing resinification/viscosity increase.

   • Synergizes with phenolic antioxidants (e.g., BHT) to enhance heat-oxidative aging resistance in vulcanized rubber (e.g., SBR, NBR).

2. Polyolefin Plastics & Polymers

   • Used in PVC, HIPS, ABS resins, and polyesters to prevent oxidative discoloration and gelation during processing.

   • In PE and PP, it serves as a secondary antioxidant, synergizing with primary antioxidants to improve weather resistance and color stability.

3. Industrial Oils & Adhesives

   • Inhibits oxidative degradation in lubricants and industrial greases.

   • Maintains long-term stability of adhesives, preventing aging-induced failure.

4. Other Fields

   • Enhances light stability in epoxy resins and fluoroethylene polymers.

   • Functions as a chelating agent in food packaging materials (subject to regulatory compliance).

4. Production Process & Technological Innovations

The mainstream synthesis involves the esterification of nonylphenol with phosphorus trichloride (PCl₃), featuring:

• Low-temperature PCl₃ addition.

• Stepwise temperature/pressure control.

• A one-step synthesis without post-treatment.

Recent advancements, such as catalytic transesterification (using triethyl phosphate), have improved yield and environmental friendliness.

5. Safety & Storage

• Packaged in galvanized iron drums (200 kg/drum).

• Store in a cool, dry place, avoiding heat, light, and moisture.

• While TNP has low toxicity, proper handling precautions are still required.

Conclusion

As a versatile polymer additive, TNP plays an indispensable role in rubber, plastics, adhesives, and beyond. Future development will focus on:

• Green synthesis technologies.

• Synergistic composite systems.

• High-end applications (e.g., food-grade packaging) to meet stricter environmental and performance demands.