N-methyl-2-pyrrolidone (NMP)
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Product Description
N-methyl-2-pyrrolidone (NMP) is a clear, colorless liquid with a "fishlike" odor and a density greater than water. It is a polar aprotic solvent belonging to the class of pyrrolidine-2-ones, where the hydrogen attached to the nitrogen is replaced by a methyl group. While NMP is widely used in industrial applications for its excellent solvent properties, it has been classified as a developmental toxicant by the U.S. Environmental Protection Agency (EPA) and is known to cause severe irritation and health risks upon contact or ingestion. Despite its toxicity, NMP is valued for its ability to dissolve various polymers and is commonly used in the manufacturing of lithium-ion battery electrodes and in the decapsulation of waste photovoltaic laminated modules.
Synthesis Methods
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High-Pressure Synthesis: From acetylene and formaldehyde.
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Reaction with Methylamine: Gamma-butyrolactone reacts with an excess of pure or aqueous methylamine in a high-pressure tube reactor.
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Hydrogenation: N-hydroxymethyl-2-pyrrolidone or mixtures of maleic or succinic anhydride and methylamine.
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Acrylonitrile Reaction: Acrylonitrile reacts with methylamine in the presence of a peroxide radical initiator.
Uses and Applications
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Industrial Solvent:
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Used in lubricant refining, polymer synthesis, and insulation material manufacturing.
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Widely used in petrochemicals for extracting aromatics from naphtha.
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Solvent in battery manufacturing (e.g., lithium-ion battery electrode production).
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Used in coatings, paints, and adhesives.
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Electronics Industry:
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High-purity (99.9%) electronic-grade NMP is used for semiconductor cleaning.
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Photoresist stripping in semiconductor manufacturing.
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Cleaning agent for precision parts.
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Pharmaceuticals:
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Solvent for drug formulation and polymer processing.
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Used in transdermal drug delivery systems.
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Polymer Processing:
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Solvent for polyimides, polyamides, and other high-performance polymers.
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Used in fiber spinning and membrane production.
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Surface Coatings:
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Used in specialty paints, coatings, and inks where high solvency and a slow evaporation rate are required.
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Properties and Characteristics
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Chemical Structure: A five-membered lactam (pyrrolidone) ring with a methyl group on the nitrogen atom.
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Appearance: Colorless to slightly yellow liquid.
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Odor: Slight amine-like or fishy odor.
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State: Liquid at room temperature.
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Polarity: Aprotic polar solvent.
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Hygroscopicity: Absorbs water from the atmosphere.
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Boiling Point: ~202°C (396°F).
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Melting Point: -24°C.
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Density: 1.028 g/cm³ (20°C).
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Solubility: Miscible with water and most organic solvents.
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Dielectric Constant: High (~32), excellent for dissolving polar and ionic compounds.
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Chemical Stability: Stable under neutral and basic conditions, but can hydrolyze slowly in acids.
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Toxicity: Moderately toxic; can cause skin irritation, eye damage, and reproductive toxicity with prolonged exposure.
Safety and Handling
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Toxicity: Moderately toxic; can cause skin irritation, eye damage, and reproductive toxicity with prolonged exposure.
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Regulations:
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European Union (EU): NMP has been restricted under REACH since 2020. Its use in concentrations above 0.3% is prohibited for most consumer and professional applications.
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United States: The EPA has listed NMP as a priority for risk evaluation and potential regulation under the Toxic Substances Control Act (TSCA).
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Handling: Use in well-ventilated areas with proper PPE (gloves, goggles).
Environmental Impact
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Biodegradability: Poor; persists in the environment.
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Vapor Pressure: Low, reducing volatile organic compound (VOC) emissions but complicating recovery.
Safer Alternatives
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Dimethyl sulfoxide (DMSO).
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Dimethylformamide (DMF) - though also hazardous.
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Dimethyl isosorbide (DMI).
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Proprietary "green" solvent blends.
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Cyrene, γ-valerolactone.