Leather Tanning

Chromium Oxide Green (Cr₂O₃) is an important high-efficiency tanning agent in the leather tanning industry, capable of imparting excellent physical properties and unique color to leather.

1. Tanning Mechanism

1.1 Coordination Bonding

Chromium oxide green forms trivalent chromium ions (Cr³⁺) in water, which coordinate with the carboxyl groups of leather collagen to form a stable cross-linked structure. This cross-linking makes leather fibers tighter, improving shrinkage temperature and mechanical strength.

1.2 Tanning Process

Pickling: Treat delimed pelt with sulfuric acid and salt, adjust pH to 2.5-3.0
Chrome tan liquor preparation: React chromium oxide green with sulfuric acid to form basic chromium sulfate
Main tanning: Add chrome tan liquor, gradually raise alkali to pH 3.8-4.2
Washing and neutralization: Remove unbound chromium, adjust pH

2. Application Advantages

2.1 Physical Property Enhancement

Shrinkage temperature increase: From 65°C of raw hide to 100-120°C
Tensile strength enhancement: Increase by 30-50%
Elongation improvement: Maintain good flexibility while improving strength
Wet heat resistance: Not easily shrunk or deformed in hot water

2.2 Appearance Quality

Imparts pale green tone, suitable for dyeing dark leather
Flat and fine grain surface, full hand feel
Good dyeing uniformity, high color fastness

3. Typical Applications

3.1 Garment Leather

Chrome tanned leather is soft, thin, and breathable, suitable for making leather clothing, skirts, etc.

3.2 Upper Leather

Chrome tanned leather has high strength and flex resistance, suitable for various leather shoe uppers.

3.3 Furniture Leather

Chrome tanned leather is wear-resistant and aging-resistant, suitable for sofas, car seats, and other furniture.

4. Product Specifications

CRL-98: Cr₂O₃≥98%, Leather Grade
Basicity: 33-50% (select according to process)
Water insolubles: <0.5%
Iron content: <0.5% (to avoid affecting color)

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