What Monoethanolamine Is and How It Is Traded
Monoethanolamine (MEA, 2-aminoethanol, CAS 141-43-5) is a primary amine that carries a hydroxyl group on the same two-carbon chain. Its formula is C2H7NO and its molecular weight is 61.08. It is a colourless, hygroscopic liquid with an ammoniacal odour, miscible with water in all proportions, boiling near 171 C at atmospheric pressure and showing a relative density of about 1.012 at 20 C. The combination of an amine function and an alcohol function is what makes it useful in cleaning formulations: the amine neutralises acidic soil and builds alkalinity, while the hydroxyl group keeps the molecule water-soluble.
In detergents MEA acts as a functional additive rather than as the main surfactant. Formulators normally dose it from about 0.2% to 3% of the finished liquid, depending on the surfactant system and the viscosity target.
Functions of MEA in Liquid Detergents
Thickening. MEA and its salts raise the viscosity of surfactant solutions. In systems built on anionic surfactants the amine interacts with the micellar structure and widens the range in which a stable, pourable product can be formulated without a separate thickening polymer.
Emulsification of oily soil. The amine reacts with fatty acids to form amine soaps in situ. Those soaps emulsify greasy and oily soils, which is why alkaline cleaners built with MEA perform well on kitchen and industrial grease.
Dispersion. MEA keeps insoluble matter suspended instead of letting it settle or re-deposit, so the cleaning liquor stays homogeneous through the wash cycle and removed soil does not go back onto the surface.
Foam behaviour. It stabilises the lamellae of surfactant foam and extends foam life in hand-dish and hard-surface products. In low-foam machine cleaners the same effect is balanced against a defoamer package.
Alkalinity reserve. A dilute MEA solution sits around pH 11, so part of the alkalinity survives dilution and the partial neutralisation that follows as acidic soil is taken up.
Typical Specification and Test Methods
| Property | Typical commercial value | Test method |
|---|---|---|
| Assay, total amine as MEA | 99.0% min | Amine value titration, ASTM D2074 |
| Water | 0.30% max | Karl Fischer titration, ASTM E203 |
| Colour | 20 Pt-Co max | ASTM D1209 |
| Density at 20 C | 1.010 to 1.015 g/cm3 | ASTM D4052 |
| Distillation range | about 168 to 172 C | ASTM D1078 |
These figures describe ordinary commercial practice rather than one fixed law. The binding values are those printed on the supplier specification and repeated in the certificate of analysis for the lot.
Other Industrial Outlets for the Same Molecule
Detergents are only one outlet. Ethanolamines are used in gas treating to strip carbon dioxide and hydrogen sulphide from process streams, as neutralising amines in personal care formulations, as cement grinding aids, as intermediates for emulsifiers, corrosion inhibitors and textile softeners, and as salt-forming counter-ions in agrochemical formulation.
Packaging, Storage and Handling Practice
MEA moves in 200 kg drums, 1000 kg intermediate bulk containers and ISO tank containers. It is corrosive to skin and seriously damaging to eyes, so transfers are made in closed systems with chemical protective equipment. The liquid absorbs carbon dioxide and water from air, which shifts assay and colour, so storage tanks are held under a dry nitrogen blanket and drums are resealed after sampling. Copper and copper alloys are avoided in wetted parts because the amine attacks them; stainless steel and lined carbon steel are the usual materials of construction. A sealed drum stored under cover, away from acids and oxidisers, holds specification for at least 24 months.
Frequently Asked Questions
Q: Is MEA a surfactant?
A: No. MEA is a builder and co-additive. It has little surface activity of its own; it improves the behaviour of the anionic and nonionic surfactants already present in the formulation.
Q: Why does MEA improve grease removal?
A: Part of the effect is alkalinity, which saponifies fatty soil, and part is the formation of amine soaps with free fatty acids. Those soaps act as emulsifiers, so oily soil is lifted and held in the wash liquor.
Q: What assay and water content should a buyer specify?
A: Detergent grades are normally bought at 99.0% minimum assay with water at 0.30% maximum, tested by amine value titration and Karl Fischer titration. Tighten the water limit when the product is moisture-sensitive.
Q: Can MEA be stored in mild steel?
A: Carbon steel is acceptable for many grades, but the tank must be dry and blanketed because the amine picks up carbon dioxide and water. Copper, brass and their alloys should not be used in wetted parts.
Q: How is MEA dosed in a liquid detergent?
A: Typical use is 0.2% to 3% by weight of the finished product. The exact level is set by the viscosity, pH and grease-cutting targets, and is confirmed by a lab viscosity curve before scale-up.
Q: Does MEA change the pH of the finished cleaner?
A: Yes. It supplies alkalinity reserve and buffers the product near pH 11 in dilution. Formulators balance it against acidic builders and thickeners fed in the same batch.