Summary:
N-Methylpyrrolidone (NMP) is a highly effective solvent for paint stripping and resin removal applications. It is also widely used as a co-solvent in industrial cleaning formulations and reaction systems.
But recent regulatory scrutiny and significant safety concerns have driven NMP users towards safer alternatives.
Our Sta-Sol® dimethyl ester based solvent blends and water soluble microemulsions may be excellent replacements for NMP in several common stripping and removal applications, including paint stripping, urethane cleaning and removal, ink cleaning, and more.
Introduction
This article focuses on finding an effective solvent alternative to NMP as a solvent used in parts cleaning and flush applications in polyurethane foam production settings.
N-methylpyrrolidinone (NMP) is a well-known solvent used in a variety of cleaning, stripping and coatings applications.
Becoming equally well-known, however, are the increasing safety and regulatory concerns related to this material at the state, federal and international level.
For example:
- NMP is listed under California’s Proposition 65 and identified as a Substance of Very High Concern (SVHC) by the ECHA under REAcH. Both designations are due to concerns about reproductive toxicity.
- NMP is also subject to Toxics Release Inventory (TRI) reporting under EPCRA Section 313 and included in certain state right-to-know legislation (e.g. MA and PA).
- NMP is currently targeted for reduction and further assessment under a 2015 TSCA Work Plan Chemical Risk Assessment.
Polyurethane Manufacturing: Parts Cleaning & Line Flush
Finding an NMP Replacement
NMP has long been recognized as an effective solvent for cleaning polyurethane resin from parts and equipment in the production of urethane foam products.
In light of the above safety and regulatory concerns, however, many urethane foam producers are looking for ways to reduce or replace NMP in their production processes.
We have worked with several of these companies, and their challenge usually involves maintaining performance and efficiency, as much as possible, while reducing risks and meeting current health, safety and environmental objectives.
Testing an Alternative: Sta-Sol® Dimethyl Esters
Sta-Sol® products are based on dimethyl (dibasic) ester chemistry.
Dimethyl esters (DMEs) are cost-effective materials consisting of purified and mixed grades of adipic, glutaric and succinic dimethyl esters.
DMEs feature preferable regulatory profiles (i.e. not reportable under EPCRA Section 313; not regulated under California Proposition 65), very low volatility, and low odor. They are also non-flammable and non-corrosive.
As we have worked with dibasic esters in different formulations and application settings for several years, we were confident that the cleaning and resin removal characteristics of Sta-Sol® would make it a viable candidate for replacing NMP in polyurethane parts cleaning and line flush applications.
The esters work to soften and dissolve, making it easier to remove the resins from a substrate.
Our esters have very low volatility and therefore evaporate at slow rates, making them suitable for parts soaking processes and recycling.
Conclusion
Based on feedback from our customers, the Sta-Sol® blends have been very effective drop-in substitutes for NMP in urethane resin cleaning and removal
(Read a recent case study about NMP replacement in urethane cleaning here.)
We have seen similar results with other resin removal applications, including uncured and partially cured acrylic resins, paints, and polymeric coatings.
As with all product suggestions, the product performance and compatibility characteristics of DMEs may depend on the specific aspects of each unique process and cannot be guaranteed. Testing and trials are recommended.
In addition, these materials are only slightly water soluble, so they may leave a slight film on parts after soaking or flushing is complete.
If water solubility is critical, Sta-Sol solvents can be formulated with emulsifiers for aqueous cleaning applications.
For example, our microemulsions combine safe and effective solvents and surfactants to deliver concentrated cleaning power in aqueous applications.
Microemulsions are formulated solvent replacements that can be extended with co-solvents or used as-is.
If you are looking to replace NMP in a cleaning or resin removal application, please feel free to contact us to discuss potential alternatives, order samples, and more.