Breakthrough in Supercritical CO₂ Spray Coating Technology

Driven by China’s “Dual Carbon” goals and increasingly stringent environmental regulations, the coating industry is seeking new eco-friendly spraying processes that maintain high performance. Supercritical CO₂-assisted spray coating has become a global research focus in recent years. By mixing supercritical carbon dioxide with coating materials, it drastically lowers viscosity, reduces or eliminates organic solvents, cuts VOC emissions by 70%–80%, and improves atomization quality and film performance. Dongguan Mansheng Automation Equipment Co., Ltd. recently announced that its supercritical CO₂ spray coating pilot system, developed jointly with South China University of Technology (SCUT), has successfully passed pilot verification. A commercial model is planned for launch in 2026, positioning Mansheng at the forefront of next-generation green coating technology.

Mainstream solvent-based coatings require large amounts of organic solvents (toluene, xylene, esters, etc.) to adjust viscosity. These solvents fully evaporate during spraying and drying, becoming the primary source of VOC emissions. Even water-based coatings contain small amounts of co-solvents, involve high drying energy consumption, and demand strict substrate treatment. The breakthrough solution: supercritical CO₂.

CO₂ reaches a supercritical state at temperatures above 31°C and pressures above 7.38 MPa, combining low viscosity, high diffusivity (gas-like) with high solvency (liquid-like). When injected into coatings, it:

• Greatly reduces viscosity, enabling smooth atomization of high-solid coatings (≥90% solids).
• Replaces organic solvents; CO₂ vaporizes instantly without residue or VOCs.
• Enhances atomization via rapid expansion and micro-explosion, producing fine droplets (10–15 μm).
• Improves film properties: density, adhesion, and gloss.

Originally developed by Union Carbide (US) and later refined in Germany and Japan, commercial adoption remains limited globally due to high-pressure equipment costs, system complexity, and narrow process windows.

In partnership with the National Engineering Research Center for Novel Polymer Processing Equipment at SCUT, Mansheng spent two years developing a compact supercritical CO₂ spray module that integrates seamlessly with its 6th-generation 360° high-speed rotating automatic spray equipment. Core components:

• CO₂ booster pump: Pressurizes industrial-grade CO₂ (≥99.5% purity) to 10–15 MPa.
• Heating & temperature control unit: Maintains 40–60°C to keep CO₂ supercritical.
• Static mixer: Uniformly blends supercritical CO₂ and coating.
• Back-pressure valve & rapid-release nozzle: Sustains system pressure and triggers instant pressure-drop atomization.

The module measures just 0.8m × 0.6m × 1.2m and can be installed beside existing spray booths without major line modifications. Mansheng simplified high-pressure sealing and pressure-release algorithms, cutting manufacturing costs by ~40% and improving safety for commercial scalability.

Tests using 85% high-solid coating show dramatic improvements:

“VOCs dropping from 68 to 14 is a remarkable result,” said the project leader. “With 23% higher material utilization and only ~¥0.2/kg CO₂ cost, total operating cost remains below traditional solvent spraying.”

1. High-solid coating mandates Construction machinery, wind turbine blades, marine coatings: thick-film anti-corrosion with strict VOC limits.
2. High-density coating requirements New energy battery cases, hydrogen storage tanks: pinhole-free, high-insulation films.
3. Green retrofits for solvent-based lines Low-cost upgrade without switching to water-based lines.

A supercritical CO₂ module is priced at ¥150,000–200,000 (excluding main spray unit). For a medium plant using 20 tons of coating yearly:

• Coating savings: ~4.6 tons/year → ¥276,000
• VOC treatment savings: ~¥8,640
• Solvent cost reduction: ~¥60,000
• Total annual savings: ~¥345,000

Net annual benefit: ~¥220,000 Payback period: ~18 months

All high-pressure lines use 316L stainless steel (rated 25 MPa) with safety valves and rupture discs. The system features multi-level interlocks for automatic pressure relief and shutdown. Supercritical CO₂ is non-toxic and non-flammable. Mansheng has completed 500+ hours of continuous testing with fluctuation controlled within ±5%. One-key start and automatic cleaning enable 5-minute color changes.

China’s 14th Five-Year Industrial Green Development Plan encourages supercritical fluid coating technologies. Guangdong offers up to 15% subsidies (max ¥2 million) for projects cutting VOCs by >50%. Mansheng assists clients with applications.

Global competitors (Nordson, Wagner) charge ¥800,000–1,500,000 per system. Mansheng’s ¥150,000–200,000 pricing aims to break foreign monopolies and enable domestic substitution. “We aim for affordable green technology, not luxury equipment,” said Mansheng’s General Manager.

• H2 2026: 10 free pilot programs in auto parts, construction machinery, wind power.
• Q2 2026: Official commercial launch.
• Build a supercritical CO₂ process database for epoxies, polyurethanes, acrylics, and various substrates.

Spraying has evolved:

1. Manual guns → automatic reciprocators (1st revolution)
2. Robots + high-speed rotary atomization (2nd revolution)
3. Supercritical CO₂ coating (3rd revolution candidate)

Mansheng’s early advancement secures China a leading role in global green coating competition.