Juhua Methylene Chloride

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Juhua Methylene Chloride, CAS 75-09-2, is a technical dichloromethane stream produced by Zhejiang Juhua Co., Ltd. for extraction, cleaning, polymer processing, and pharmaceutical isolation. The product is supplied as a clear liquid with a molecular weight of 84.93 g/mol, a normal boiling point of 39.6 °C, a melting point of −96.7 °C, and a density of 1.326 g/cm³ at 20 °C. The saturated vapor pressure at 20 °C is approximately 47.4 kPa, placing the material among the fastest evaporating chlorinated solvents used in enclosed equipment. The Hansen solubility parameters are typically reported as δD 18.2 MPa^0.5, δP 6.3 MPa^0.5, and δH 6.1 MPa^0.5; this combination yields strong solvency for acrylic, alkyd, epoxy, and chlorinated polymer matrices. Unlike ethyl acetate or methyl ethyl ketone, Juhua Methylene Chloride does not exhibit a closed-cup flash point under ASTM D93; the material is controlled by the GHS classifications H351, H332, and H336, which require exposure monitoring under 29 CFR 1910.1052.

Commercial designations for Juhua Methylene Chloride include industrial grade, high-purity grade, and extraction/polyurethane grade. The high-purity stream is directed to closed-loop pharmaceutical extraction and polycarbonate synthesis, where water ingress above 50 ppm can alter reaction stoichiometry and phase separation. Industrial-grade material is released for vapour degreasing and paint stripping, where stabilizer identity and acidity are the primary process-control variables. The product is available in 250 kg drums, 1.1 t intermediate bulk containers, and isotanks; export lots are usually accompanied by a batch certificate of analysis referencing GB/T 4117-2008.

Regulatory documentation for Juhua Methylene Chloride includes EU REACH registration, Chinese hazardous chemical registration, and the CLP Index Number 602-004-00-3; the EINECS number is 200-838-9. These document sets differentiate the product from repacked generic DCM that may not carry downstream-use exposure scenarios or full REACH registration.

What Specification Benchmarks Apply to High-Purity Dichloromethane in Extraction Service?

For pharmaceutical and polymer applications, the residual solvent framework is ICH Q3C, where methylene chloride is listed as a Class 2 solvent with a concentration limit of 600 ppm in the final drug substance unless a higher level is justified by daily exposure calculations. Juhua product released for extraction service is therefore controlled for non-volatile residue, acidity, and metals. The table below lists the typical release envelope for high-purity and industrial grades; different domestic producers may meet the same assay value but differ in trace stabilizer identity and moisture history.

For closed-loop extraction systems, the limiting parameter is frequently not dichloromethane assay but water content and non-volatile residue. A water level above 0.005 wt% in DCM used for water-sensitive reactions can hydrolyze phosgene or acid chloride intermediates, increasing byproduct formation and lowering yield. In polycarbonate interfacial polymerization, methylene chloride is the organic phase; excessive moisture distorts the phase ratio and alters molecular weight distribution. Published data for Juhua product in this specific configuration is limited to batch certificates rather than independent peer-reviewed studies.

Process control at the production site includes gas chromatographic analysis of chlorinated impurities such as chloroform and carbon tetrachloride. In high-purity grade, chloroform is typically held below 50 ppm and carbon tetrachloride below 10 ppm; industrial grades may have higher limits but remain within GB/T 4117-2008 and the export specification. This distinction is measurable in radical polymerization processes where chain-transfer-active impurities alter molecular weight control.

Differences between Juhua Methylene Chloride and alternative merchant DCM streams are primarily traceability, stabilizer identity, and moisture control. In high-shear dispersion of chlorinated polymers, the solvent must contain water below 100 ppm and acidity below 10 ppm as HCl; Juhua high-purity material is typically released against these constraints. Some imported DCM reaches the same assay but carries higher non-volatile residue due to bulk transfer and repackaging; the difference becomes measurable in gravimetric residue after distillation, where residue above 0.001 wt% can deposit on wiped-film evaporator blades and shorten service intervals. Users switching from another DCM source should run comparative distillation residue checks under ASTM D1353 and gas chromatographic impurity scans before qualifying the product for pharmaceutical or polycarbonate service.

Paint stripping and resinous coating removal rely on a high Kauri-butanol number of approximately 136, higher than perchloroethylene (90) and methyl ethyl ketone (120). The solvency allows DCM-based strippers to penetrate crosslinked alkyd, epoxy, and polyurethane films at temperatures between 18 °C and 35 °C without external heating. Commercial formulations add paraffin or polymeric film formers to reduce evaporative loss; without a seal, the 47.4 kPa vapor pressure at 20 °C reduces wet contact time on vertical surfaces and drives solvent loss. The product is used where substrate temperature must remain below 60 °C and where N-methyl-2-pyrrolidone or dibasic ester strippers require longer dwell periods. Open-tray stripping must be performed under local exhaust and air monitoring per 29 CFR 1910.1052(d).

Vapour Degreasing Equipment and Light Metal Compatibility

Vapour degreasing with Juhua Methylene Chloride is conducted in enclosed top-open or vacuum degreasers with freeboard ratios above 0.75 and solvent cooling coils maintained at 5–10 °C below the boiling point. The latent heat of vaporization is approximately 28.6 kJ/mol, permitting rapid condensation and high throughput in conveyorized lines. However, methylene chloride is aggressive to unprotected aluminium, magnesium, and zinc in hot, wet environments. If water separates in the sump, hydrochloric acid can form and attack light-metal components and carbon steel; the product should therefore be used with continuous moisture removal and stainless steel or coated carbon steel fluid paths. For aluminium parts, pre-cleaning validation under ISO 2812-1 is recommended to quantify corrosion risk before production-scale conversion from hydrocarbon or alcohol degreasers. Vacuum degreasers with total enclosure and carbon bed recovery reduce operator exposure to the 25 ppm OSHA permissible exposure limit and improve solvent recovery.

Pharmaceutical extraction uses Juhua Methylene Chloride for alkaloid purification, reaction solvent, and crystallization isolation where the low boiling point permits product recovery in falling-film evaporators at reduced temperature. The ICH Q3C Class 2 limit of 600 ppm for residual methylene chloride means final dryers must be validated by gas chromatography. Typical vacuum drying at 40–45 °C and 20–50 mbar is used, but residual solvent removal must be confirmed for each product because high-amorphous materials can retain DCM above the limit. Low non-volatile residue and low water content in the solvent reduce contamination of heat exchanger surfaces in multi-effect evaporation systems. The product document set should include batch-level gas chromatographic purity and residue data rather than a simple distributor repack certificate.

Polycarbonate interfacial polymerization uses methylene chloride as the organic phase for bisphenol A and phosgene condensation. The product requirement in this application is not only high assay but low water and low methyl chloride content. A water level above 0.005 wt% shifts the hydrolysis equilibrium and reduces polymer molecular weight; typical polycarbonate producers specify water content below 50 ppm. The high density of DCM ensures clean phase separation from the aqueous brine phase in continuous stirred-tank reactors. Compared with non-chlorinated solvents such as ethyl acetate or dichlorobenzene, DCM has a lower boiling point, which simplifies solvent recovery and reduces thermal stress on the polymer. Published data for Juhua product in polycarbonate-specific service is limited; most producers qualify suppliers through bench-scale oligomerization tests and full-scale reactor trials.

If Methylene Chloride Is Compared With Trichloroethylene and Ethyl Acetate in Continuous Immersion Cleaning

Continuous immersion cleaning requires solvent selection based on evaporation rate, density, flammability, and solvency. DCM has a boiling point of 39.6 °C and a vapor pressure of 47.4 kPa at 20 °C; trichloroethylene boils at 87.2 °C and evaporates more slowly; ethyl acetate has a flash point of −4 °C and is classified as a flammable liquid under GHS H225, whereas DCM does not have a closed-cup flash point under ASTM D93. For thick oil and wax removal, DCM offers a Kauri-butanol number near 136, which is higher than ethyl acetate and close to trichloroethylene, but it may attack acrylic and polycarbonate parts if immersion times exceed process validation. The table below summarizes comparative values used in solvent substitution studies.

Flexible slabstock polyurethane foam processing employs methylene chloride as an auxiliary blowing agent to supplement carbon dioxide generation from the isocyanate-water reaction. The low boiling point of Juhua Methylene Chloride produces additional gas during the exothermic polymerization phase, allowing formulators to reduce water content and control foam hardness independently of density. On continuous slabstock lines with trough widths above 2 m, methylene chloride additions are typically held between 2 phr and 8 phr, with higher levels producing finer cell structure but increasing the risk of scorch in thick blocks. Because the heat of vaporization of DCM is approximately 28.6 kJ/mol, excessive addition can absorb enough exothermic energy to alter the temperature profile and delay tin-catalyzed gel reactions. The product stream used for polyurethane must be low in acidity and water; water above 0.02 wt% changes the water index and can create reproducibility problems in continuous equipment. Foam density is typically measured according to ISO 845; target density for flexible slabstock foams is often 15–30 kg/m³. Published data for this specific configuration is limited, and line-scale validation is required for each foam recipe.

Adhesive and sealant manufacturing uses Juhua Methylene Chloride in polychloroprene contact cements and acrylic sprayable adhesives. The high density of 1.326 g/cm³ at 20 °C reduces overspray bounce-back in high-pressure air-assisted spray equipment, improving transfer efficiency on porous substrates. Rotational viscosity of a 20 wt% polychloroprene solution in a DCM/toluene blend is typically adjusted to 500–2,000 mPa·s at 25 °C under ASTM D2196, allowing fast wet-out and rapid tack development in lamination lines. The low boiling point of 39.6 °C shortens open time, so production equipment must be tuned to high-speed application and forced-air drying. The solvent is not suitable for waterborne adhesive systems and should not be combined with strong bases or reactive metal powders.

Storage and handling of Juhua Methylene Chloride require closed transfer and dry-gas blanketing where moisture must remain below 50 ppm. The liquid is denser than water and will sink in collection sumps; drainage systems should be sealed because vapor can travel long distances. Elastomer selection should avoid natural rubber and EPDM, which swell rapidly; polytetrafluoroethylene, high-density polyethylene, and butyl rubber are commonly used for service. The OSHA permissible exposure limit under 29 CFR 1910.1052 is 25 ppm as an 8-h time-weighted average, with a short-term exposure limit of 125 ppm. The ACGIH threshold limit value is 50 ppm TWA. Process vents should be routed to carbon adsorption or thermal oxidation. The product is not assigned H225, but vapor can form ignitable mixtures at elevated temperatures; autoignition temperature is approximately 556 °C. Therefore, welding or open-flame work in storage areas requires a confined-space permit and lower-explosive-limit monitoring.