1. Chemical Structure and Properties
Molecular Formula: C₁₀H₂₂O₃
Structural Formula:
HO-(CH₂CH₂O)₂-CH₂(CH₂)₄CH₃
A branched glycol ether composed of two ethylene oxide units linked to a hexyl group, terminated by a hydroxyl group.
Physical Properties:
Appearance: Clear, colorless to pale yellow viscous liquid with a mild ether-like odor.
Boiling Point: 245–250°C; Density: 0.93–0.95 g/cm³; Vapor Pressure: <0.01 mmHg at 25°C.
Solubility: Partially miscible with water (0.5% w/w at 25°C); fully miscible with alcohols, esters, and hydrocarbons.
Chemical Properties:
Hydrolysis Stability: Resistant to hydrolysis under neutral conditions; degrades in strong acids/bases to ethylene glycol and hexanol.
Thermal Stability: Stable up to 200°C; decomposes above 250°C, releasing aldehydes and ethylene oxide.
Flammability: Combustible (flash point: ~110°C).
2. Industrial Applications
Coatings & Inks:
High-Boiling Solvent: Enhances flow, leveling, and gloss retention in high-temperature industrial coatings (e.g., automotive, aerospace).
Coalescing Agent: Improves film formation in waterborne latex paints and adhesives.
Cleaning Products:
Heavy-Duty Degreaser: Removes oils, greases, and waxes in machinery, engines, and metal surfaces.
Personal Care:
Emollient & Stabilizer: Used in cosmetics (e.g., creams, lotions) for its non-greasy texture and skin compatibility.
Chemical Synthesis:
Intermediate: Produces surfactants and specialty esters for lubricant additives.
3. Safety and Toxicology
Health Hazards:
Acute Exposure:
Skin Contact: Mild irritation (rabbit skin LD₅₀: >2,000 mg/kg); negligible systemic absorption.
Inhalation: Low volatility minimizes risk (TLV-TWA: Not established); handle as nuisance vapor.
Ingestion: Low toxicity (oral LD₅₀ rat: >5,000 mg/kg); gastrointestinal discomfort.
Chronic Effects:
Reproductive Toxicity: No teratogenicity observed in OECD 414 studies.
Organ Toxicity: Negligible hepatotoxicity or nephrotoxicity in subchronic rodent studies.
Protection Measures:
PPE: Nitrile gloves, safety goggles, and general ventilation.
Storage: Stable in HDPE containers; store away from oxidizers.
4. Environmental and Regulatory Compliance
Environmental Impact:
Biodegradability: Slow (OECD 301F: <30% in 28 days); moderately persistent in soil and water.
Aquatic Toxicity: LC₅₀ (fish, 96h): >100 mg/L; EC₅₀ (daphnia): >50 mg/L.
Bioaccumulation: Moderate (log Kow: ~3.0).
Regulatory Frameworks:
EU:
REACH: Registered with no SVHC listing; CLP classification Not Hazardous.
USA:
EPA: Exempt from VOC status under 40 CFR 51.100(s)(1); TSCA-listed.
China:
GB 13690-2009: Classified as General Chemical (non-hazardous).
Waste Management:
Incinerate in approved facilities; landfill disposal permitted for neutralized residues.
5. Case Studies and Application Insights
Case 1: Sustainable Automotive Coatings (Axalta, 2023):
Challenge: Reduce VOC emissions in solvent-borne automotive clearcoats.
Solution: Diethylene glycol hexyl ether replaced 20% of xylene in formulations.
Result: Achieved 30% lower VOC emissions (ASTM D6886) and maintained scratch resistance (ASTM D3363).
Case 2: Green Industrial Cleaners (Ecolab, 2022):
Process: Formulated a bio-based degreaser using diethylene glycol hexyl ether and plant-derived surfactants.
Impact: Reduced solvent waste by 35% and met EU Ecolabel criteria.
Comparative Analysis:
DGHE vs. Ethylene Glycol Hexyl Ether:
Pros: Lower volatility, higher thermal stability, and reduced dermal absorption.
Cons: Higher viscosity (~25 mPa·s) limits use in spray applications.
DGHE vs. Propylene Glycol Ethers (PGE):
Pros: Superior solvency for non-polar contaminants; better compatibility with hydrophobic resins.
Cons: PGE offers faster evaporation and lower chronic toxicity.
Specifications:
Used as a solvent for lacquers, paints, resins, dyes, oils and lubricants, as well as coupling and dispersing agents.