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Pigment Yellow 194 is an organic pigment used widely in plastics, coatings, inks, and other applications where bright yellow coloration is needed
CAS Number: 84313-90-6
Synonyms:
Benzimidazolone Yellow H6G,C.I. Pigment Yellow 194,PY 194,Monoazo benzimidazolone yellow
Disazo condensation pigment
Pigment Yellow 181 (PY 181), a high-performance organic pigment, is widely used in applications requiring excellent thermal stability, weather resistance, and color strength.
This article delves into its chemical structure, synthesis methods, physicochemical properties, application domains, environmental impacts, and market dynamics.
Through a multidisciplinary approach, the article presents a scientific and technical overview for researchers and industrial users.
Introduction:
Pigment Yellow 181 belongs to the family of benzimidazolone pigments and is known for its strong yellow shade, durability, and resistance properties.
Discovered during efforts to create heat-stable organic pigments, it quickly gained traction in demanding industrial applications.
PY 181 is particularly valuable for plastic coloration, automotive coatings, and high-end printing systems.
Its synthesis and commercialization reflect advancements in heterocyclic chemistry and pigment dispersion science.
Chemical Identity and Structure:
IUPAC Name and Synonyms:
IUPAC: 2-(2-hydroxy-3-oxo-1H-indol-1-yl)-N-(2-methoxyphenyl)acetamide
Synonyms: Pigment Yellow 181, C.I. Pigment Yellow 181, Benzimidazolone Yellow H6G
Molecular Formula and Weight:
Molecular Formula: C17H14ClN3O4
Molecular Weight: ~359.77 g/mol
Chemical Structure:
PY 181 features a benzimidazolone core with functional groups contributing to resonance stabilization and chromophoric behavior.
The inclusion of a methoxyphenyl moiety enhances hue and stability, while electron delocalization over the conjugated system determines its strong yellow color.
This structure also accounts for excellent photostability.
Synthesis and Production Methods:
Synthetic Route:
The typical synthesis involves diazotization of an aromatic amine, followed by coupling with an appropriate heterocyclic component.
Cyclization under acidic or thermal conditions leads to the benzimidazolone ring formation.
Catalysts and pH control are critical for purity and yield.
Raw Materials and Intermediates:
Essential intermediates include substituted anilines, isatoic anhydride, and phenolic compounds. Reaction conditions often require organic solvents (e.g., xylene, toluene) and control of temperature and pH for safe and efficient processing.
Process Flow Diagram:
The industrial-scale process involves:
Nitration and reduction of starting materials
Diazotization at low temperature
Coupling under alkaline conditions
Cyclization and isolation
Filtration, drying, and milling to desired particle size
Physical and Chemical Properties:
Appearance and Colorimetric Properties:
Bright yellow powder with high color strength
CIE Lab* values measured in standard test conditions
Solubility:
Insoluble in water
Soluble or dispersible in certain organic binders and resins
Thermal and Light Stability:
Stable up to 300°C (TGA results)
Excellent lightfastness (>7 on Blue Wool Scale)
pH Stability:
Stable in acidic and mildly basic conditions
Degradation possible in strong alkaline solutions
Particle Size and Surface Area:
Primary particles ~200-400 nm
Surface area ~10-30 m2/g (BET)
Spectroscopic and Analytical Characterization:
UV-Vis Spectroscopy:
λmax: ~440-460 nm
High molar absorptivity in the visible region
FTIR Analysis:
Characteristic bands at 3300 cm^-1 (N-H), 1650 cm^-1 (C=O), 1600 cm^-1 (C=C aromatic)
NMR Spectroscopy:
Distinct peaks for methoxy, aromatic, and amide protons in 1H-NMR
Mass Spectrometry:
m/z peak around 360 confirms molecular weight
Fragmentation pattern supports structure
Chromatography Methods:
HPLC used for purity and impurity profiling
Reversed-phase methods preferred for pigment extracts
Crystalline and Polymorphic Behavior:
6.1 X-Ray Diffraction Analysis:
Sharp peaks indicating crystalline form
Powder XRD used for phase purity
Polymorphic Forms and Transitions:
One primary stable polymorph
Transition observed under high shear or thermal stress
Applications and Industrial Uses:
Plastics and Polymers:
Used in polyolefins, PVC, PET
Low migration and high heat stability
Automotive Coatings:
Provides long-lasting color in OEM and refinish paints
High weather resistance
Industrial Coatings:
Applied in coil coatings, powder coatings, and marine paints
Printing Inks:
Compatible with UV-curable, solvent-based, and water-based inks
Other Specialized Uses:
Art supplies, aerospace components, and high-performance composites
Performance Properties in Applications:
Weather and Light Fastness:
Excellent results in QUV and Xenon arc testing
Resistance to UV degradation
Chemical Resistance:
Resistant to acids, alkalis, oils, and solvents
Dispersibility:
Easily dispersible in polymer matrices
Requires dispersing agents for aqueous systems
Color Strength and Tinting:
High tinctorial strength
Used for color matching and formulation in blends
Regulatory and Safety Aspects:
REACH and Global Registration:
Registered under REACH
Listed in TSCA and compliant with FDA for certain uses
SAFETY INFORMATION ABOUT PIGMENT YELLOW 194
First aid measures:
Description of first aid measures:
General advice:
Consult a physician.
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
If inhaled:
If breathed in, move person into fresh air.
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off contaminated clothing and shoes immediately.
Wash off with soap and plenty of water.
Consult a physician.
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
If swallowed:
Do NOT induce vomiting.
Never give anything by mouth to an unconscious person.
Rinse mouth with water.
Consult a physician.
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment.
Avoid breathing vapours, mist or gas.
Evacuate personnel to safe areas.
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste.
Keep in suitable, closed containers for disposal.
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place.
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles.
Faceshield (8-inch minimum).
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
Skin protection:
Handle with gloves.
Gloves must be inspected prior to use.
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product.
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices.
Wash and dry hands.
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls.
If the respirator is the sole means of protection, use a full-face supplied air respirator.
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions.
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company.
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product
