In the resin and rosin industry, achieving high purity and a light color tone is crucial for producing quality products used in varnishes, coatings, adhesives, and printing inks. One of the most effective chemicals used for this purpose is Oxalic Acid, known for its strong chelating and decolorizing properties.
Let’s understand how oxalic acid plays a vital role in refining rosin, a natural resin derived from pine trees.
 
 What Is Rosin?

Rosin (also called colophony) is a solid, brittle resin obtained after distilling pine tree resin. When the sticky tree sap (called oleoresin) is heated, it separates into two parts:

• Turpentine – the volatile liquid portion, and
• Rosin – the solid residue that remains after distillation.

However, the crude rosin that results from this process often contains metallic impurities such as iron, calcium, and magnesium, and may have a dark yellow or brown tint due to oxidation. These impurities can lower its grade and limit its applications in high-quality products.
 
 Role of Oxalic Acid in Rosin Refining

Oxalic Acid (C₂H₂O₄) is used during the melting and clarification stage of rosin refining. It serves two key functions — removing metallic impurities and improving color.

Here’s how the process typically works:

1. Melting the Crude Rosin
The crude rosin is heated to a controlled temperature (usually between 120°C and 150°C) until it becomes a uniform molten liquid. This allows the treatment chemicals to mix evenly.

2. Addition of Oxalic Acid
A measured quantity of oxalic acid is added to the molten rosin.

• The acid reacts with metal ions (Fe²⁺, Ca²⁺, Mg²⁺) to form insoluble oxalates.
• These impurities are responsible for discoloration and poor transparency in rosin.

3. Decolorization and Clarification
As oxalic acid reacts, it bleaches the rosin, reducing its dark tint and enhancing its clarity. The result is a pale, transparent rosin suitable for premium-grade applications.

4. Filtration
After the reaction is complete, the molten rosin is filtered to remove the precipitated oxalate impurities. This step ensures a smooth, impurity-free product.
 
 Benefits of Using Oxalic Acid in Rosin Refining

• Removes Metallic Impurities: Chelates and eliminates iron, calcium, and magnesium.
• Improves Color: Produces pale or water-white rosin.
• Enhances Transparency: Gives a cleaner and more attractive appearance.
• Increases Product Value: Suitable for high-end coatings, adhesives, and inks.
• Ensures Stability: Results in a refined, long-lasting product.

 
 Applications of Refined Rosin

Refined rosin treated with oxalic acid finds applications across multiple industries:

• Varnishes and Paints – for a smooth, glossy, and durable finish.
• Adhesives – for paper, packaging, and wood industries.
• Printing Inks – for better color brightness and print quality.
• Rubber Compounds – as a tackifying agent.
• Soap and Cosmetics – as a natural additive for gloss and stability.

 Did You Know?

Rosin and turpentine both come from pine tree resin.
When raw resin is heated, it separates into:

• Turpentine – the liquid that evaporates and is collected as oil, and
• Rosin – the solid residue left behind after the turpentine is distilled.
  This rosin is then refined with oxalic acid to improve its color, clarity, and quality.

 
 Conclusion

The use of Oxalic Acid in rosin refining is a well-established industrial practice that helps produce high-quality, light-colored resin for specialized applications. Its ability to remove metallic impurities and enhance color makes it an indispensable chemical for manufacturers aiming for superior performance and visual appeal in their end products.

At Sampan Enterprises, we supply high-purity LR Grade Oxalic Acid, wihich can be used in the rosin and resin refining industries for consistent performance, superior quality, and reliability.