| HS Code | |
| Productname | N-Methylpyrrolidone |
| Synonyms | 1-Methyl-2-pyrrolidone; NMP; 1-Methylpyrrolidin-2-one |
| Casnumber | 872-50-4 |
| Einecsnumber | 212-828-1 |
| Molecularformula | C5H9NO |
| Molecularweight | 99.13 g/mol |
| Appearance | Colorless to light yellow liquid |
| Odor | Mild amine-like odor |
| Boilingpoint | 202 °C |
| Meltingpoint | -24 °C |
| Flashpoint | 91 °C closed cup |
| Autoignitiontemperature | 270 °C |
| Density | 1.028 g/cm3 at 25 °C |
| Vaporpressure | 0.32 mmHg at 20 °C |
| Viscosity | 1.65 mPa·s at 25 °C |
| Refractiveindex | 1.470 at 20 °C |
| Solubility | Miscible with water, alcohols, ethers, ketones, chloroform, and aromatic hydrocarbons |
| Ph | 7.7 (100 g/L in water at 20 °C) |
| Logp | -0.38 |
| Purity | ≥99.5% typical industrial grade |
| Watercontent | ≤0.05% typical |
| Colorapha | ≤20 typical |
As an accredited N-Methylpyrrolidone factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | N-Methylpyrrolidone supplied in 200 L UN-approved steel drums, chemically resistant, sealed, labeled with appropriate hazard warnings. |
| Container Loading (20′ FCL) | N-Methylpyrrolidone (NMP) loaded into a 20-foot FCL container, drummed, palletized, secured, and sealed for safe ocean shipment. |
| Shipping | N-Methylpyrrolidone is typically shipped in sealed steel drums, IBCs, or tank trucks. It is generally not classified as dangerous goods for transport. Keep containers closed, upright, and protected from moisture, sunlight, heat, ignition sources, and strong oxidizers. Follow local regulations and SDS guidance. |
| Storage | Store N-Methylpyrrolidone in a cool, dry, well-ventilated area away from heat, sparks, flames, and strong oxidizers. Keep containers tightly closed, properly labeled, and upright; use secondary containment to prevent spills. Ground and bond during transfers. Avoid contact with acids, bases, and moisture. Store in a dedicated, ventilated cabinet or combustible-liquid storage area. Follow local regulations and SDS recommendations. |
| Shelf Life | N-Methylpyrrolidone has a shelf life of about 24 months when stored in a tightly sealed container under cool, dry conditions. |
PVDF binder dissolution in NMP for lithium-ion cathode slurry is governed by the solvent's hydrogen-bonding solubility parameter and low water tolerance. Production formulations begin with a PVDF pre-gel at 6–8 wt% in NMP homogenized under high shear until solution viscosity reaches 3,000–12,000 mPa·s at 25 °C. The final coating slurry contains NMP at 25–35 wt%, adjusted to obtain 3,000–8,000 mPa·s viscosity typical for slot-die application; high-nickel cathode grades with carbon nanotube conductive dispersions may require the upper end, while lithium iron phosphate pastes often run lower due to particle-size distribution. On production lines, planetary mixers operating at reduced pressure of -0.09 MPa and disperser tip speeds of 15–25 m/s prevent air entrainment, because water above 0.03 wt% in recovered NMP causes PVDF gelation and coating streak defects. Slot-die coating onto aluminium foil uses wet-film gaps of 150–300 µm, followed by multi-zone drying from 80 °C to 130 °C; exhaust concentration is maintained below 25% LEL because NMP LEL is 1.3 vol%. NMP recovery skids with condensation and activated-carbon adsorption return solvent to the process, but batch-to-batch variance in amine impurity content above 20 ppm can shift slurry viscosity by several hundred mPa·s despite identical weighing. Industrial compliance is anchored to REACH Annex XVII Entry 71 for NMP concentration thresholds and occupational DNEL-based risk management, US EPA TSCA risk evaluation requirements, and ACGIH TLV-TWA of 10 ppm with skin notation for worker exposure. Finished article types include NMC, LFP, and LCO cathode-coated aluminium foil rolls subsequently calendered and slit for prismatic, cylindrical, or pouch lithium-ion cells used in electric vehicles and stationary storage.
In high-density interconnect printed circuit board fabrication, NMP-containing remover formulations are deployed for post-etch photoresist stripping and for removal of no-clean flux residues from reflowed assemblies. Formulated strippers combine NMP at 35–65 wt% with an alkanolamine such as monoethanolamine at 10–20 wt%, water at 5–10 wt%, and a corrosion inhibitor package; this composition balances polymer swelling rate against copper attack on fine-line traces. Process equipment includes immersion modules operated at 60–80 °C for 5–15 min, spray-in-air chambers at 1.5–2.5 bar, and ultrasonic agitation at 40 kHz where blind vias require residue-free sidewall cleaning. Subsequent deionized-water rinsing is monitored by IPC-TM-650 Method 2.3.25 for ionic contamination, with acceptance thresholds at 1.56 µg NaCl/cm² or tighter for class 3 assemblies; final articles must also comply with RoHS Directive 2011/65/EU restrictions after cleaning. Terminal outputs are rigid and flexible PCB assemblies, CMOS image sensor modules, and display panel polarizer films, where residual NMP is reduced below customer-specific outgassing limits.
Before die-coating of magnet wire, polyamic acid prepolymer is dissolved in NMP at mass fractions of 75–88 wt% with dissolved solids between 12–20 wt%. The solution is prepared in jacketed reactors under dry nitrogen because water above 0.03 wt% hydrolyzes pyromellitic dianhydride-derived polyamic acid, decreasing molecular weight and final enamel flexibility. Viscosity at 25 °C typically lies between 1,500–6,000 mPa·s, and die-coating equipment with slot-die gaps of 10–30 µm applies the enamel to copper or aluminium wire. Thermal imidization in vertical ovens with staged zones from 300–400 °C converts the polyamic acid to polyimide, releasing ring-closure water and residual NMP that must be extracted to maintain insulation properties. Compliance verification for the finished magnet wire includes ASTM D1676 film-insulated magnet wire test methods and the IEC 60317 series for winding wire classes; REACH Annex XVII Entry 71 also applies to NMP in the enamel formulation during coil-coating operations. Terminal product types are high-temperature enameled wire rated at class 180, 200, and 220 used in traction motors, aerospace generators, and oil-well drilling motors.
Butadiene recovery from steam-cracker C4 streams uses NMP as an extractive distillation solvent to alter relative volatilities between 1,3-butadiene and close-boiling butanes/butenes. In a first extractive distillation column, solvent-to-feed mass ratios are maintained between 4:1 and 6:1 for raw C4 feedstock containing 40–50 wt% 1,3-butadiene; higher ratios increase separation factor but raise reboiler duty and solvent degradation. Column pressure is controlled at 4–6 bar, overhead temperature at 40–60 °C, and bottoms at 120–150 °C to avoid NMP thermal breakdown, which is indicated by free amine content and pH reduction in the lean solvent loop. The rich solvent is then fed to a stripping column where 1,3-butadiene is released at lower pressure and purified to polymer-grade specification of ≥99.5 wt% with acetylene impurities below 50 ppm. Compliance testing for product quality follows ASTM D2593 gas chromatographic determination of butadiene purity and hydrocarbon impurities; REACH registration obligations apply to the NMP inventory in the distillation unit. Downstream products include styrene-butadiene rubber, polybutadiene rubber, acrylonitrile-butadiene-styrene resins, and styrene-butadiene latex used in tire compounds and impact-modified plastics.
In active pharmaceutical ingredient manufacturing, NMP is confined to reaction steps where its dipolar aprotic character accelerates SNAr and N-alkylation chemistry; process development reports typically charge NMP at 5–15 L/kg of limiting substrate, although the exact ratio is fixed by solubility and reaction rate studies. The solvent is removed by solvent-swap vacuum distillation at 40–60 °C and 50–200 mbar in glass-lined reactors, because thermal stress above 80 °C can generate peroxide and amine breakdown products that complicate downstream crystallization. Residual NMP in the final active pharmaceutical ingredient is controlled to 530 ppm as the ICH Q3C Class 2 permissible daily exposure of 5.3 mg/day; release testing employs headspace gas chromatography aligned with USP Chapter 467 residual solvent procedures. Manufacturing operations comply with 21 CFR Part 211 current good manufacturing practice for finished pharmaceuticals, and EU REACH obligations apply to NMP as an industrial solvent. Terminal products include APIs from kinase inhibitor, antiviral, and agrochemical synthesis routes, as well as advanced intermediates where NMP is used for selective crystallization or salt formation.
Polysulfone and polyethersulfone ultrafiltration membrane casting dope is prepared with NMP as the primary solvent, with polymer content between 15–25 wt% and NMP at 75–85 wt%; polyvinylpyrrolidone pore former is included at 1–5 wt% to modify surface hydrophilicity. The dope is filtered through 25 µm absolute-rated cartridge filters before slot-die casting at wet thicknesses of 100–300 µm onto a moving nonwoven polyester support. Phase inversion occurs in a water coagulation bath maintained at 16–24 °C; the NMP-water exchange rate at the skin layer determines whether a dense selective barrier or macrovoid-rich sublayer forms. Membrane leaf or hollow-fiber production lines extract residual NMP in post-casting rinse tanks, and the final product is tested for molecular weight cut-off, pure-water flux, and tensile break strength. Compliance for drinking-water contact membranes is covered by NSF/ANSI 61 extraction protocols, and ISO 9001 process control applies to the casting line; EU REACH Annex XVII Entry 71 applies to NMP in the dope make-up area. Terminal product types include flat-sheet and hollow-fiber ultrafiltration and microfiltration cartridges for municipal water treatment, food concentration, and biopharmaceutical protein separation.
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N-Methylpyrrolidone (CAS 872-50-4; molecular weight 99.13 g/mol) is supplied as a hygroscopic polar aprotic solvent with grades differentiated by water content, amine impurities, and trace-metal burden. Typical industrial specification sheets list assay ≥99.0%, water ≤0.10%, APHA colour ≤50, and methylamine ≤0.01%. Semiconductor-grade material is controlled to assay ≥99.8%, water ≤0.02%, chloride ≤0.5 mg/kg, sodium ≤0.1 mg/kg, iron ≤0.1 mg/kg, and APHA colour ≤10; these trace-metal limits are aligned with SEMI Grade 5 processing for front-end semiconductor applications. Density by ASTM D4052 is 1.028 g/cm³ at 25 °C; closed-cup flash point by ASTM D93 is 91 °C; autoignition temperature is 270 °C; vapour pressure is 0.29 mmHg at 20 °C. Because the solvent is hygroscopic, bulk transfers under nitrogen pad and desiccant breathers are specified when water-sensitive upstream chemistry is used.
| Specification parameter | Industrial grade | Semiconductor grade | Test method |
|---|---|---|---|
| Assay | ≥99.0% | ≥99.8% | Gas chromatography |
| Water | ≤0.10% | ≤0.02% | ASTM D1364 |
| APHA colour | ≤50 | ≤10 | ASTM D1209 |
| Chloride | ≤1 mg/kg | ≤0.5 mg/kg | Ion chromatography |
| Sodium | ≤1 mg/kg | ≤0.1 mg/kg | ICP-MS |
| Iron | ≤0.2 mg/kg | ≤0.1 mg/kg | ICP-MS |
| Methylamine | ≤0.01% | ≤0.005% | Gas chromatography |
| Flash point | 91 °C | 91 °C | ASTM D93 |
Polymer-grade NMP is controlled primarily by water, colour, and amine content because residual water hydrolyses polyamic acid precursors and shifts imidization kinetics. In polyimide wire-enamel and flexible circuit production, NMP solutions of 18–25 wt% polyimide precursor exhibit Brookfield viscosity (ASTM D2196, spindle RV4, 20 rpm) in the range of 10,000–50,000 mPa·s at 25 °C. Specifications for total amine impurities below 0.005% prevent premature termination during condensation polymerization, while iron below 0.1 mg/kg avoids discoloration in films cured at 300–350 °C. Viscosity drift in stored solutions is a more sensitive batch indicator than assay alone; a lot with acceptable assay but water above 0.05% may show viscosity reduction within 48 h in closed containers. Production-scale batch data from glass-lined mixing vessels show that the addition sequence of dianhydride to NMP-solvated diamine controls exotherm and final molecular weight distribution better than reverse addition.
In semiconductor and printed circuit board manufacturing, NMP is used as a photoresist stripper and polyimide cleaning solvent in wet-bench equipment constructed from stainless steel 316L or fluoropolymer materials. Operating temperature is maintained at 80 °C in recirculating immersion tools because vapour pressure remains below 1 mmHg at that temperature, limiting evaporative loss. Semiconductor-grade NMP is specified to avoid metallic contamination on 300 mm wafer substrates; cation limits are controlled by ICP-MS and particle counts are measured by laser particle sensors after filtration through 0.1 µm PTFE cartridges. Published photoresist stripping-rate data for specific film grades is limited; the dissolution mechanism involves resin swelling followed by delamination rather than direct oxidative attack. Water ingress above 0.5% is controlled because it reduces swell rate and increases particle counts in post-strip rinses. In printed circuit board defluxing, NMP is blended with non-amine surfactants for solder-flux residue removal; amine synergists are limited to 5–8 wt% because higher concentrations promote copper tarnishing under damp-heat storage at 85% RH.
The solvency window of NMP is defined by Hansen parameters of 18.0 MPa0.5 dispersion, 12.3 MPa0.5 polar, and 7.2 MPa0.5 hydrogen-bonding components, giving a total of 22.9 MPa0.5. The interaction distance Ra against polyethersulfone, polyamide-imide, and polyvinylidene fluoride is below 8 MPa0.5, whereas nonpolar polyolefins show Ra above 12 MPa0.5 and are not dissolved. For polyvinylidene fluoride-based electrode binders, dissolution at 60–80 °C under high-shear mixing is required because room-temperature solvation is slow; the resulting solution viscosity depends on PVDF molecular weight and degree of fluorine content. NMP also acts as a coalescing agent in waterborne polyurethane dispersions at addition levels of 3–5 wt%, where it lowers minimum film formation temperature by 4–6 °C per percent addition. Its dielectric constant of 32.2 at 25 °C supports dissociation of lithium salts in electrochemical applications but is lower than that of DMSO (46.7), which influences solvation-shell structure in non-aqueous systems.
In high-temperature condensation polymerizations such as polyaryl ether synthesis, NMP operates as the reaction medium under nitrogen at temperatures up to 200 °C. The reaction mass typically contains 20–30 wt% polymer solids and disodium salts, resulting in a slurry viscosity that shifts from 100 mPa·s at 120 °C to below 20 mPa·s at 180 °C in glass-lined agitated reactors. This reduction in viscosity allows the conversion of phenol-terminated oligomers without exceeding the torque limit of the agitator. NMP is selected over dimethyl sulfoxide in these systems because it is less prone to decomposition in the presence of potassium carbonate and aromatic diols at 180–200 °C. However, the high boiling point of NMP increases solvent recovery energy; vacuum stripping at 20–50 mbar with a jacket temperature of 140–160 °C is required to remove residual solvent from the precipitated polymer crumbs.
Because NMP has a boiling point 49 °C higher than DMF and a flash point 33 °C higher than DMF, it is substituted in polyimide precursor formulations where higher curing temperatures and higher processing safety margins are required. A direct solvent substitution cannot be made without adjusting the imidization cycle: NMP has stronger hydrogen-bond acceptance than DMF and a lower vapour pressure, so the drying stage in film casting is extended by 30–50% in casters with 120–180 °C hot-air zones. The higher boiling point allows step-curing at 300 °C without solvent boiling defects, whereas DMF residual can cause blistering at temperatures above 200 °C. Substitution also changes viscosity because polyimide precursor solutions in NMP typically show higher viscosity than equivalent solids in DMF; it is corrected by reducing solids by 1–2 wt%. When DMF is replaced by NMP, solvent recovery condensers require higher heating-medium temperatures of 140–160 °C for NMP-water separation, compared with 110–125 °C for DMF-water systems in atmospheric columns.
Coating-line substitution of DMSO by NMP in lithium-ion anode and cathode slurries changes both the drying-rate profile and the cleanability of the slot-die apparatus. DMSO has a melting point of 18.5 °C, while NMP remains liquid down to -24 °C, eliminating heated storage in cold-room batch preparation. The viscosity of NMP at 25 °C is 1.65 mPa·s, lower than DMSO at 1.99 mPa·s, allowing slightly higher solids loading for a given slot-die pressure drop. NMP vapour pressure is 0.29 mmHg at 20 °C, lower than DMSO vapour pressure of 0.55 mmHg at 20 °C; drying-zone temperature profiles therefore require air velocities of 1.5–2.5 m/s and zone temperatures of 80–120 °C to achieve residual solvent below 500 ppm in coated electrodes. Slot-die cleanability improves with NMP because dried NMP-based PVDF slurry is less hygroscopic than DMSO-based residue, but NMP exposure to copper foil at elevated temperatures requires control of water content below 0.05% to avoid surface oxidation. Published comparative data for full-scale electrode coating machines is limited; however, pilot-line results with 600 mm slot-die coaters show NMP-based slurries require lower cleaning-solvent volume than DMSO-based slurries.
For pharmaceutical and extractive distillation applications, residual NMP is controlled under ICH Q3C as a Class 2 solvent with a permitted daily exposure of 5.3 mg/day and a concentration limit of 530 ppm. In active pharmaceutical ingredient manufacturing, NMP is used as a reaction solvent for nucleophilic substitutions, where its dipole moment of 4.09 debye and high boiling point allow higher reaction temperatures than tetrahydrofuran or dimethylformamide. Residual levels in final drug product must be validated by gas chromatography with flame-ionization detection according to USP 467, with a limit of quantification below 50 ppm for routine release. Bulk pharmaceutical-grade NMP must meet low peroxide and low non-volatile residue specifications; supplier certificates of analysis commonly report peroxide values below 5 mg/kg and residue on evaporation below 10 mg/kg. Because NMP is under REACH Annex XVII entry 71, supply to professional users above 0.3% concentration requires appropriate risk-management measures. In aromatics separation, water addition of 10–20 wt% is used to increase extractive distillation selectivity at the expense of capacity.
Closed-loop recovery of NMP from semiconductor waste streams is constrained by the accumulation of low-volatility organic by-products and trace amines. Recovery by vacuum distillation in wiped-film evaporators operating at 60–80 °C and 10–30 mbar produces overhead NMP with water below 0.05%, but the distillate remains contaminated with methylamine and morpholine derivatives if the feed contains photoresist degradation products. Adsorptive polishing over molecular sieve and activated carbon beds reduces amine levels to <0.005%; the beds require replacement every 2–4 weeks when feed amine load exceeds 50 mg/kg. Reboiler temperature is held below 100 °C to prevent ring-opening by-products, and the reboiler is blanketed with nitrogen containing <10 ppmv oxygen. Repeated recycling can increase sodium and iron levels in the recovered solvent; ICP-MS analysis of recovered NMP shows sodium levels of 0.2–1.0 mg/kg compared with <0.1 mg/kg for fresh semiconductor-grade material. For this reason, closed-loop material is often reserved for lower-spec cleaning rather than direct reuse in polymer synthesis.
Among solvent alternatives, N-ethyl-2-pyrrolidone (NEP) and γ-butyrolactone (GBL) differ from NMP in volatility, viscosity, and safety profile. NEP has a boiling point near 212 °C, a flash point near 95 °C, and a viscosity near 2.4 mPa·s at 25 °C, which makes it less volatile than NMP but more viscous. GBL has a boiling point near 204 °C, a flash point near 98 °C, and a density of 1.13 g/cm³; it is a cyclic ester with higher density and a more restricted regulatory status in some jurisdictions. In polymer dissolution, NMP is preferred over GBL for polyimide and aramid processing because its amide structure provides stronger hydrogen-bond acceptance; in lithium-ion electrode manufacture, GBL can be used in some low-temperature formulations but exhibits lower solubility for high-molecular-weight PVDF than NMP. NMP also differs from dimethylformamide in toxicity and regulatory burden: DMF has a lower boiling point (153 °C) and lower flash point (58 °C), and DMF is classified under ICH Q3C as Class 2 with a concentration limit of 880 ppm, while NMP has a lower concentration limit of 530 ppm.
| Property | NMP | DMF | DMSO |
|---|---|---|---|
| CAS number | 872-50-4 | 68-12-2 | 67-68-5 |
| Molecular weight | 99.13 g/mol | 73.09 g/mol | 78.13 g/mol |
| Density at 25 °C | 1.028 g/cm³ | 0.944 g/cm³ | 1.100 g/cm³ |
| Boiling point | 202 °C | 153 °C | 189 °C |
| Flash point, closed cup | 91 °C | 58 °C | 87 °C |
| Viscosity at 25 °C | 1.65 mPa·s | 0.92 mPa·s | 1.99 mPa·s |
| Dielectric constant | 32.2 | 36.7 | 46.7 |
| ICH Q3C class | Class 2, 530 ppm | Class 2, 880 ppm | Class 3, 5000 ppm |
