Phthalic anhydride

Phthalic Anhydride is an important aromatic chemical intermediate that appears as white crystalline flakes or powder with a pungent, irritating odor.
It is primarily used as a key raw material in the production of saturated and unsaturated polyester resins, PVC plasticizers, alkyd resins, and various pharmaceutical and dye intermediates.

Chemical Structure

Phthalic Anhydride consists of a 1,3-isobenzofuran-1,3-dione ring, obtained by dehydration of phthalic acid.

• Molecular Formula: C₈H₄O₃

• Structure Type: Cyclic anhydride derived from phthalic acid

• Functional Groups: Two carbonyl groups within a fused aromatic ring

Physical and Chemical Properties

Key Advantages

• Essential intermediate in manufacturing saturated and unsaturated polyester resins, widely used in fiberglass, coatings, and industrial paints.

• Primary precursor for phthalate plasticizers used to enhance flexibility and durability in PVC.

• Plays a crucial role in the synthesis of pharmaceuticals, dyes, pigments, and cosmetic raw materials.

• High reactivity and conversion efficiency, enabling cost-effective large-scale production.

Limitations and Hazards

• Strong irritant to skin, eyes, and respiratory system; requires controlled industrial environments.

• Dust explosion hazard: airborne fine particles may ignite — appropriate dust control systems are essential.

• Reacts exothermically with moisture — hydrolyzes to phthalic acid upon exposure to humidity.

• Environmental restrictions apply in some regions due to ecological impact and emission control standards.

Applications

• Unsaturated Polyester Resins (UPR): for FRP, composites, laminates, and industrial coatings.

• Plasticizer Production: synthesis of phthalate esters for flexible PVC applications.

• Paints, Adhesives, and Pigments: intermediate for alkyd resins and colorant synthesis.

• Pharmaceuticals and Cosmetics: used in controlled synthesis of active intermediates.

• Specialty Chemicals: manufacturing of lubricant additives, fertilizers, and functionalized industrial oils.

Safety and Handling

GHS Classification:

• H317 – May cause an allergic skin reaction

• H318 – Causes serious eye damage

• H334 – May cause respiratory sensitization

Personal Protective Equipment (PPE):

• Safety goggles or face shield

• Chemical-resistant gloves and protective clothing

• Respiratory protection where dust formation is possible

Storage Conditions:

• Store in a cool, dry, and well-ventilated area

• Keep containers tightly closed and away from moisture

• Prevent dust accumulation and static discharge

Emergency Measures:

• Skin/Eye Contact: Flush immediately with plenty of water and seek medical attention

• Inhalation: Move to fresh air and consult a physician if irritation persists

• Spillage: Avoid dust dispersion; collect dry material and dispose of safely according to local regulations

Summary:
Phthalic Anhydride (PA) is a high-purity, versatile intermediate essential in the resin, plasticizer, coating, and chemical manufacturing industries.
Its balance of reactivity, performance, and product yield makes it a critical compound in modern industrial chemistry — provided it is handled under proper safety and environmental protocols.