2-Anilino-6-Dibutylamino-3-Methylfluoran CAS 89331-94-2 Thermal paper colorant

2-Anilino-6-Dibutylamino-3-Methylfluoran: Uses and Synthesis Methods

I. Basic Physical Parameters

Molecular Weight: 532.67

Appearance: White to off-white crystalline powder

Melting Point: 179–184 ℃

Solubility:

Almost insoluble in water (solubility in water at 20℃ is only in the μg range);

Easily soluble in toluene, xylene, esters, aliphatic hydrocarbons, and other organic solvents;

Density: 1.23 g/cm³; Extremely low vapor pressure at room temperature, weak volatility

Storage Requirements: Store in a sealed, light-protected, dry place at room temperature.

II. Core Chemical Properties

1. Core Color Development Mechanism (Reversible Ring Opening of the Lactone Ring)

The molecule contains a spirocyclic lactone structure, which is the fundamental reason for its color change:

At room temperature/neutral environment: The lactone ring closes, the conjugated molecular system breaks, and it becomes colorless;

In the presence of acidic color-developing agents (bisphenol A, phenols, zinc salicylate, etc.) or under heat (80–120 ℃) or pressure: The lactone ring breaks, forming a large conjugated planar cation, which absorbs visible light and appears as a deep, pure blue-black;

Cooling/ 1. **Reversible Temperature Change:** After eliminating acidity, some systems can revert to colorless (colorless after reversible temperature change).

2. Thermochemical Properties:

High thermal sensitivity: Printing temperature approximately 80–90℃, fast color development, clear and high blackness of printed text;

Thermal stability: Stable at room temperature for a long time, only slowly decomposing above 200℃;

Excellent whiteness of the base color: Almost no yellowing on blank paper, resistant to storage and does not easily develop spontaneous color.

3. Light and Environmental Stability:

Superior resistance to sunlight/UV light compared to most fluorescein black dyes, printed text is resistant to sunlight and does not easily fade;

Resistant to grease, weak alkali, and mild friction, suitable for long-term preservation of labels and tickets;

Stable under weakly acidic conditions, strong inorganic acids will permanently destroy the spirocyclic structure, which cannot be restored.

4. Solvent and Compatibility Characteristics

Excellent compatibility with paraffin, plasticizers, resins, and various phenolic color developers;

Can be compounded with yellow and red leuco dyes to adjust gray, brown, dark blue, and other complex hues;

The molecule contains dibutylamino and phenylamino hydrophobic groups, making it resistant to water migration and preventing coatings from easily smudging.

Main Industrial Applications

1. Thermal Paper (Largest Application Area)

As the primary black colorant, almost all commercial thermal papers use ODB-2 as the core raw material:

Cashiers' receipts, supermarket price tags, express delivery slips, ATM receipts;

Medical test reports, ECG charts, ECG recorders;

Fax paper, industrial barcode thermal labels, warehouse logistics labels.

Advantages: High blackness, good resolution, clean background color, long shelf life.

2. Carbonless Copy Paper (Pressure-Sensitive Dye)

ODB-2 is microencapsulated to form a pressure-sensitive coating. When the paper is pressed, the microcapsules rupture, and the dye comes into contact with the underlying acidic coating to develop color. Used for: multi-part forms, contracts, invoices, and logistics copy forms.