| Chemical Properties |
Methyl methacrylate is a methyl ester of methacrylic acid. It is a colourless, volatile liquid with an acrid fruity odour. It has a relatively high vapour pressure (4 kPa at 20°C), moderate water solubility (15.8 g/litre), and a low log octanol/water partition coefficient (Kow = 1.38) . Methyl methacrylate is typically 99.9% pure and contains small amounts of inhibitor to retard polymerization. |
| Definition |
ChEBI: An enoate ester having methacrylic acid as the carboxylic acid component and methanol as the alcohol component. |
| Uses |
- Methyl methacrylate is a volatile synthetic chemical that is used principally in the production of cast acrylic sheet, acrylic emulsions, and moulding and extrusion resins.
- In the manufacture of methacrylate resins and plastics. Methyl methacrylate is transesterified into higher methacrylates such as n-butyl methacrylate or 2-ethylhexyl methacrylate.
- methyl methacrylate monomer is used in the production of methylmethacrylate polymers and copolymers, polymers and copolymers are also used in waterborne, solvent, and undissolved surface coatings, adhesives, sealants, leather and paper coatings, inks, floor polishes, textile finishes, dental prostheses, surgical bone cements, and leaded acrylic radiation shields and in the preparation of synthetic fingernails and orthotic shoe inserts. Methyl methacrylate is also used as a starting material to manufacture other esters of methacrylic acid.
- Granules for injection and extrusion blow moulding which for their outstanding optical clarity, weathering and scratch resistance are used in lighting, office equipment and electronics (cell phone displays and hi-fi equipment), building and construction (glazing and window frames), contemporary design (furniture, jewellery and tableware), cars and transportation (lights and instrument panels), health and safety (jars and test tubes) and household appliances (microwave oven doors and mixer bowls).
- Impact modifiers for clear rigid polyvinyl chloride.
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| Production Methods |
Methyl methacrylate (MMA) is the most important ester of methacrylic acid. It can be homo- and copolymerised to produce acrylic resins with good strength, transparency and with excellent weather resistance. The first commercial process for making MMA (1930's), the acetone cyanohydrin route, remains the predominant process in use today. In the acetone cyanohydrin route, acetone cyanohydrin reacts with sulfuric acid at low temperature to produce the sulfuric monoester of 2-hydroxy-2-methyl-propionamide, which forms methacrylamide sulphate after exposure to higher temperatures (100° - 140°C). The liquid phase is maintained by using an excess of 0.2 - 0.7 moles of 100% sulfuric acid. The first step of the reaction is strongly exothermic while the rearrangement of the sulfuric ester is endothermic.
During the synthesis of methacrylamide, a portion of the acetone cyanohydrin decomposes to carbon monoxide during the first part of the reaction. Additionally other by-products are formed and react due to the strength of the acid and high temperature in the second step. About 92 - 94% of the acetone cyanohydrin is converted to useful products and 6 - 8% is consumed in the formation of organic by-products (acetone, acetone sulphonates, olygomers, polymers, others). Methacrylamide sulphate is esterified with a mixture of water and methanol to form MMA and an aqueous solution of ammonium hydrogensulphate, sulfuric acid and the organic by-products. The ammonium hydrogensulphate is an unavoidable by-product of the reaction. |
| General Description |
A clear colorless liquid. Slightly soluble in water and floats on water. Vapors heavier than air. Vapors irritate the eyes and respiratory system. Containers must be heavily insulated or shipped under refrigeration. An inhibitor such as hydroquinone, hydroquinone methyl ester and dimethyl t-butylphenol is added to keep the chemical from initiating polymerization. The chemical may polymerize exothermically if heated or contaminated with strong acid or base. If the polymerization takes place inside a container, the container may rupture violently. Used to make plastics. |
| Air & Water Reactions |
Highly flammable. Very slightly soluble in water. |
| Reactivity Profile |
Methyl methacrylate, may polymerize if contaminated or subjected to heat. If polymerization takes place in a container, the container is subject to violent rupture. Oxidizes readily in air to form unstable peroxides that may explode spontaneously [Bretherick 1979. p.151-154, 164]. Peroxides may also initiate exothermic polymierization of the bulk material [Bretherick 1979. p. 160]. Benzoyl peroxide was weighed into a beaker that had previously been rinsed with methyl methacrylate. The peroxide catalyzed polymerization of the methyl methacrylate and the build-up of heat ignited the remaining peroxide [MCA Case History 996. 1964]. |
| Hazard |
Flammable, dangerous fire risk, explosivelimits in air 2.1–12.5%. Eye and upper respiratorytract irritant, body weight effects, and pulmonaryedema. Questionable carcinogen. |
| Health Hazard |
- Methyl methacrylate may cause slight eye irritation or moderate skin irritation. It is considered a skin sensitizer; allergic reactions may result from contact. Inhalation of vapor or mist can cause irritation of the nose, throat, and lungs and can be fatal in high concentrations. Prolonged or repeated overexposure has been reported to affect the kidneys, liver, gastrointestinal tract, nervous system and lung.
- Methyl methacrylate is moderately toxic to aquatic organisms on an acute basis. The bioconcentration potential (tendency to accumulate in the food chain) is low. If released to surface water, methyl methacrylate will readily biodegrade. A portion may evaporate to the air. It will not persist in the environment.
- Irritation of eyes, nose, and throat. Nausea and vomiting. Liquid may cause skin irritation.
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| Fire Hazard |
Behavior in Fire: Vapor is heavier than air and may travel a considerable distance to a source of ignition and flash back. Containers may explode in fire or when heated because of polymerization. |
| Safety Profile |
Moderately toxic by inhalation and intraperitoneal routes. Mildly toxic by ingestion. Human systemic effects by inhalation: sleep effects, excitement, anorexia, and blood pressure decrease. Experimental teratogenic and reproductive effects. Mutation data reported. A skin and eye irritant. Questionable carcinogen with experimental tumorigenic data. A common air contaminant. A very dangerous fire hazard when exposed to heat or flame; can react with oxidizing materials. Explosive in the form of vapor when exposed to heat or flame. The monomer may undergo spontaneous, explosive polymerization. Reacts in air to form a heat-sensitive explosive product (explodes on evaporation at 6OOC). May ignite on contact with benzoyl peroxide. Potentially violent reaction with the polymerization initiators azoisobutyronitrile, dibenzoyl peroxide, di-tert-butyl peroxide, propionaldehyde. To fight fire, use foam, CO2, dry chemical. When heated to decomposition it emits acrid smoke and irritating fumes. |
| storage |
Methyl methacrylate is a reactive chemical that must be stored and handled with care. It is stable under recommended storage conditions. Heat can cause polymerization. Inhibitor is added to methyl methacrylate monomer to prevent polymerization. For the inhibitor to be effective, the oxygen concentration in the vapor space must be at least 5%. Store material in containers made of stainless steel, carbon steel, glass, or aluminum. Avoid contact with acids, bases, oxidizing agents, reducing agents, UV light (ultraviolet light, which is found in sunlight), free-radical initiators, and organic peroxides. |
| Purification Methods |
Wash the ester twice with aqueous 5% NaOH (to remove inhibitors such as hydroquinone) and twice with water. Dry it with CaCl2, Na2CO3, Na2SO4 or MgSO4, then with CaH2 under nitrogen under reduced pressure. The distillate is stored at low temperatures and redistilled before use. Prior to distilling, inhibitors such as hydroquinone (0,004%), .-naphthylamine (0.2%) or di--naphthol are sometimes added. Also purify it by boiling with aqueous H3PO4 solution and finally with saturated NaCl solution. It is dried for 24hours over anhydrous CaSO4, distilled at 0.1mm Hg at room temperature and stored at -30o [Albeck et al. J Chem Soc, Faraday Trans 1 1 1488 1978]. [Beilstein 2 II 398, 2 III 1279, 2 IV 1519.] |
