Because of their versatile properties, PURASOLV lactate esters are successfully being used in a wide range of applications in the solvent cleaning industry. In the PU industry, their high solvency power enables fast and effective dissolution of a wide range of resins, specifically polyurethane resins. PURASOLV is successfully used in the following applications:

• MDI line flushing
• elastomeric PU line and nozzle flushing
• nozzle cleaning for PU spray coatings

MDI line flushing

MDI is the most widely used isocyanate in the PU industry. In low-pressure systems, moisture from the air can penetrate the lines, especially during (intermediate) production stops. The moisture reacts with MDI to form a polymer, which crystallizes readily, causing clogged lines and pumps. Broken pumps and hardened line deposits require repairs and cleaning that could involve substantial costs and downtime.

The use of PURASOLV can prevent this from happening. The alpha-hydroxy group present in the molecule and its excellent solvency power will make the MDI end groups react with PURASOLV.

When a line or system containing MDI or its oligomers is flushed with PURASOLV, it will immediately react with the MDI end groups, blocking MDI and its oligomers from reacting with water before actual crystallization occurs. The reaction product formed with PURASOLV will readily dissolve in PURASOLV.

Because of this, the potential threat of crystallization is eliminated and the equipment can be restarted without extensive cleaning procedures. The application of PURASOLV has substantially decreased consumption compared to the traditionally used chlorinated solvents.

Elastomeric PU line and nozzle flushing

In the molding of elastomeric PU foams for applications like automotive filter production, the polyol and isocyanate are dosed in a fixed ratio into the nozzle mixing head. The polyol-isocyanate mixture will react readily, so the mold must be filled with this mixture within a tight timeframe.

Nozzle contamination cannot be completely avoided, requiring regular solvent cleaning of the nozzle and mixing chamber, after which a dump shot is required before regular molding can be continued.

Traditionally, highly volatile (chlorinated) solvents are used in this application. The application of PURASOLV represents an excellent alternative. The slow evaporation properties of PURASOLV require optimization of solvent use per cleaning cycle as well as drying time after the cleaning cycle and prior to the next dump shot. Optimization results in a substantial reduction of solvent use as well as a reduction of the dump shots.

Nozzle cleaning in PU spray coatings

Nozzles used for PU spray coatings require regular cleaning between spray cycles. In general, fast evaporating solvents such as MEK are used. MEK is a HAP (hazardous air pollutant) and its usage must be reported. Due to their low boiling point, such solvents evaporate readily. This increases the solvent usage per cleaning cycle and makes reclaiming or recycling options almost impossible. The combination of a low flashpoint and fast evaporation constitute a safety risk.

PURASOLV has excellent solvency power for PU resins as used in spray coating applications resulting in high cleaning efficiency. With PURASOLV, substantial (50% or better) solvent usage reductions can be achieved; recycling or reclamation of PURASOLV is also possible.