Acrylates

Methyl Methacrylate

Methyl Methacrylate (also known as MMA, 2-methylmethacrylate, or methyl 2-methyl propenoate) is an ester of methacrylic acid.  It has the formula C5H8O2 and is a clear, colourless liquid that has an acrid odour and is not known to occur naturally.  It is insoluble in water, but is soluble in most organic solvents and it is also volatile and is flammable in both a liquid and vapour state.

Production

The main route of MMA production is by reacting hydrogen cyanide with acetone to form acetone cyanohydrin.  This is then reacted with concentrated sulphuric acid to produce methacrylate sulfate.  This is then reacted with methanol and water to form methyl methacrylate.  However, producers are looking at alternate production methods as this process involves the handling of highly toxic hydrogen cyanide, and also produces large amounts of ammonium bisulfate, as a by-product, which must then be disposed of.

Storage and Distribution

Methyl methacrylate must be transported and stored in containers made of stainless steel, glass, aluminium, or carbon steel.  It should be stored in a cool, dry, well-ventilated area that is out of the direct sunlight and is away from all sources of ignition.  It is normally supplied with an inhibitor as autopolymerisation can occur, especially in light.

MMA has a specific gravity of 0.939 and a flash point of 10 oC (closed cup) so must be labelled as highly flammable and it should also be labelled as an irritant.  For transportation purposes, MMA is classified as hazard class 3, and pack group II.

Uses

Methyl methacrylate is an important chemical as it is the monomer for polymethyl methacrylate (PMMA) polymers and copolymers.  These polymers and copolymers are then used in the manufacture of a variety of other products.  These include clear plastics (such as Plexiglass), resins, and acrylic sheets.  Some of the end products that have utilised these chemicals are advertising signs and displays, skylights, building panels and sidings, and plumbing and bathroom fittings.

MMA is also polymerised to form lubricant viscosity modifiers, dispersions,  molding/extrusion powder, and coatings.  These are then utilised in the production of such things as acrylic surface and paper coatings, adhesives, sealants, leather and paper coating, inks, textile finishes, latex paints, and lacquer and enamel resins.

MMA is also used in the fields of medicine and dentistry as it is used to make prosthetic devices, surgical bone cements, and as a ceramic filler or cement.  It can also be used in the production of orthotic shoe inserts, and in leaded acrylic radiation shields.

MMA can also be used in the impregnation of concrete as it makes the concrete water repellent.  It can also be used to partially replace styrene in unsaturated polyester resins as it gives better water resistance and a longer life to the final products.