Introduction

Thiourea is an important chemical used in leather manufacturing, especially in wet-end processing stages. It is mainly valued for its reducing properties, which support cleaner unhairing, better bleaching results, and improved dye performance. Many tanneries choose thiourea because it works efficiently while helping reduce environmental and safety risks linked to traditional sulfide-based chemicals.

In modern leather production, thiourea is commonly used in beamhouse and finishing operations. Its stable performance and low dosage needs make it suitable for both small and large-scale tanneries, particularly those aiming to meet stricter environmental standards.

 

Core Chemical Functions of Thiourea

Thiourea acts mainly as a reducing agent in leather processing. During unhairing, it breaks the sulfur bonds in keratin, allowing hair to loosen and separate from the hide. This process avoids the use of lime-sulfide systems that release hydrogen sulfide gas, making the workplace safer and reducing odor issues.

Thiourea is also used as a bleaching and decolorizing agent. It reduces natural pigments, blood stains, and fat residues in hides, helping produce a more even base color before dyeing. This improves final leather appearance and color consistency.

In addition, thiourea helps stabilize pH in certain process mixtures and slows microbial growth in process liquors. These properties support cleaner processing and reduce defects caused by bacterial damage.

 

Use in Leather Processing Stages

Thiourea is widely applied during beamhouse operations, especially in unhairing and liming. Typical use levels range from 0.5 to 2 percent based on hide weight. It works effectively at moderate temperatures between 20 and 30°C, helping dissolve hair roots without damaging the grain layer.

After tanning, thiourea supports bleaching during wet finishing. It removes remaining color from chrome-tanned hides before neutralization, which is important for light-colored or pastel leather products.

In dyeing operations, thiourea helps reduce certain dyes into soluble forms so they can penetrate leather fibers more evenly. This leads to better dye uptake and uniform color. It is usually applied under mildly acidic conditions and moderate heat, fitting well into standard drum dyeing cycles.

Thiourea is also used during neutralization and fatliquoring to keep process liquors clean. It prevents surface scum and residue buildup, which can cause marks or uneven finishes on high-grade leathers.

 

Differences Across Leather Sectors

Thiourea use varies depending on the leather type and end application. In footwear upper leather, it is mainly used for clean unhairing to protect grain quality. For garment leather, bleaching is more important to achieve soft, light shades.

Automotive and upholstery leather producers value thiourea for its preservative role, as it helps prevent mold growth during storage and transport. In glove and bag leather production, lower thiourea doses are used to maintain softness and flexibility.

Heavy leathers, such as belts and industrial leather, often require higher dosages to handle thicker hides. In export-focused tanneries, especially in Asia-Pacific, thiourea formulations are adjusted to meet international regulations, with controlled purity and stabilizers added for safer handling.

 

Operational Value and Efficiency

Thiourea improves overall process efficiency by reducing unhairing time by up to 30 percent compared to traditional methods. Shorter processing cycles mean lower water and energy use, helping reduce production costs.

Its chemical stability across a wide pH range allows consistent results over multiple batches. Low dosage needs also help control raw material costs, while lower chemical loss improves overall yield.

From an environmental perspective, thiourea reduces organic load in wastewater. Lower BOD and COD levels help tanneries meet discharge rules, especially in regions with strict environmental controls. Reduced corrosion in processing equipment also extends drum life and lowers maintenance costs.

Thiourea performs well in high-volume operations, making it suitable for continuous production lines that handle tens of thousands of hides per week.

 

Conclusion

Thiourea plays a valuable role in modern leather manufacturing by supporting cleaner unhairing, better bleaching, and improved dye performance. Its reducing action, low dosage needs, and stable behavior make it an efficient alternative to traditional sulfide-based chemicals. As the leather industry moves toward safer and more environmentally responsible processing, thiourea remains a practical and effective solution for tanneries across footwear, garment, upholstery, and industrial leather sectors.