Methyl methacrylate

Description

Methyl methacrylate is an organic compound with the formula CH₂=C(CH₃)COOCH₃. This colourless liquid, the methyl ester of methacrylic acid (MAA) is a monomer produced on a large scale for the production of poly(methyl methacrylate) (PMMA).

Chemical Properties

Methyl methacrylate is a colorless liquid. Acrid, fruity odor. The odor threshold is 0.05
0.083 ppm

Chemical Properties

Methyl 2-methyl-2-propenoate has an acrid, penetrating odor. In another report this compound is reported to possess a sharp, fruity odor

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.

Physical properties

Clear, colorless liquid with a penetrating, fruity odor. An experimentally determined odor threshold concentration of 210 ppb_v was reported by Leonardos et al. (1969). Experimentally determined detection and recognition odor threshold concentrations were 200 μg/m³ (49 ppb_v) and 1.4 mg/m³ (340 ppb_v), respectively (Hellman and Small, 1974).

Uses

Methyl methacrylatec is used in acrylic bone cements used in orthopedic surgery; in the production of acrylic polymers, polymethylmethacrylate and copolymers used in acrylic surface coatings; in the manufaeture of emulsion polymers; in the modification of unsaturated polyester resins; in the production of higher methacrylate, acrylic fibers, acrylic film, inks, radiation-polymerized impregnants for wood, and solvent-based adhesives and binders; as an impact modifier of PVC; in medicinal spray adhesives; in nonirritant bandage solvents; in dental technology as ceramic filler or cement; to coat corneal contact lenses; in intraocular lenses, artificial nails, and hearing aids; as a monomer for polymethaerylate resins; in the impregnation of concretc.

Uses

The principal application, consuming approximately 80% of the MMA, is the manufacture of poly methyl methacrylate acrylic plastics (PMMA). Methyl methacrylate is also used for the production of the co-polymer methyl methacrylate-butadiene-styrene (MBS), used as a modifier for PVC. Another application is as cement used in total hip replacements as well as total knee replacements. Used as the "grout" by orthopedic surgeons to make the bone inserts fix into bone, it greatly reduces post-operative pain from the insertions but has a finite lifespan. Typically the lifespan of methyl methacrylate as bone cement is 20 years before revision surgery is required. Cemented implants are usually only done in elderly populations that require more immediate short term replacements. In younger populations, cementless implants are used because their lifespan is considerably longer. Also used in fracture repair in small exotic animal species using internal fixation.

Uses

1. 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.
2. In the manufacture of methacrylate resins and plastics. Methyl methacrylate is transesterified into higher methacrylates such as n-butyl methacrylate or 2-ethylhexyl methacrylate.
3. 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.
4. 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).
5. Impact modifiers for clear rigid polyvinyl chloride.

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.

Production Methods

The compound is manufactured by several methods, the principal one being the acetone cyanohydrin (ACH) route, using acetone and hydrogen cyanide as raw materials. The intermediate cyanohydrin is converted with sulfuric acid to a sulfate ester of the methacrylamide, methanolysis of which gives ammonium bisulfate and MMA. Although widely used, the ACH route coproduces substantial amounts of ammonium sulfate. Some producers start with an isobutylene or, equivalently, tert-butanol, which is sequentially oxidized first to methacrolein and then to methacrylic acid, which is then esterified with methanol. Propene can be carbonylated in the presence of acids to iso butyric acid, which undergoes subsequent dehydrogenation . The combined technologies afford more than 3 billion kilograms per year. MMA can also be prepared from methyl propionate and formaldehyde.

Preparation

Prepared by the esterification of methacrylamide sulfate with methanol.

Definition

ChEBI: Methyl methacrylate is an enoate ester having methacrylic acid as the carboxylic acid component and methanol as the alcohol component. It has a role as an allergen and a polymerisation monomer. It is an enoate ester and a methyl ester. It is functionally related to a methacrylic acid.

Aroma threshold values

Detection at 0.024 to 0.058 ppm (water); recognition at 0.7 to 1.4 mg/m3 (air); detection at 0.2 to 0.62 mg/m3.

Synthesis Reference(s)

Journal of the American Chemical Society, 70, p. 1153, 1948 DOI: 10.1021/ja01183a082
The Journal of Organic Chemistry, 33, p. 2525, 1968 DOI: 10.1021/jo01270a082

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

1. 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.
2. 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.
3. Irritation of eyes, nose, and throat. Nausea and vomiting. Liquid may cause skin irritation.

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.

Flammability and Explosibility

Flammable

Industrial uses

Initiators for methyl methacrylate polymerization include AIBN, dilauroyl peroxide (LPO), and 2,2'-Azobis[2-(2-imidazolin-2- yl)propane].

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.

Potential Exposure

Virtually all of the methyl methacrylate monomer produced is used in the production of polymers, such as surface coating resins; plastics (Plexiglas and Lucite); ion exchange resins; and plastic dentures.

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts theskin, remove contaminated clothing and wash immediatelywith soap and water. Seek medical attention immediately. Ifthis chemical has been inhaled, remove from exposure,begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR ifheart action has stopped. Transfer promptly to a medicalfacility. When this chemical has been swallowed, get medical attention. Give large quantities of water and inducevomiting. Do not make an unconscious person vomit.

Carcinogenicity

In several lifetime animal studies, there was no evidence that methyl methacrylate is carcinogenic.

Environmental Fate

Chemical/Physical. Polymerizes easily (Windholz et al., 1983). Methyl methacrylate undergoes nucleophilic attack by OH ions in water (hydrolysis) resulting in the formation of methacrylic acid and methanol (Kollig, 1993). Hydrolysis occurs at a rate of 171/M?h at 25 °C (Sharma and Sharma, 1970). No measurable hydrolysis was observed at 85.0 °C (pH 7) and 25 °C (pH 7.07). Hydrolysis half-lives of 9 and 134 min were observed at 66.0 °C (pH 9.86) and 25.0 °C (pH 11.3), respectively (Ellington et al., 1987).

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.

Shipping

UN1247 Methyl methacrylate monomer, stabilized, Hazard Class: 3; Labels: 3-Flammable liquid.

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.]

Toxicity evaluation

The mitochondria are regarded as the main intracellular target of MMA. If isolated rat liver mitochondria are incubated with MMA, oxygen consumption increases. This is the result of an uncoupling of the mitochondrial respiratory chain, as seen from the expected influence on state 4 and state 3 respiration. State 4 respiration is stimulated. As has been reported for organic solvents, MMA attacks complex I of the respiratory chain close to the rotenonebinding site. This means that substrates which are oxidized in conjunction with nicotinamide adenine dinucleotide inhibit the flow of electrons and thus also ATP synthesis. Unlike classical uncouplers, MMA stimulates the Mg2+- dependent ATPase bound to the inner mitochondrial membrane. Structural changes in the inner membrane, as found with nonionic detergents, were observed by electron micro scopy. The release of enzymes indicates disintegration of the membrane.

Incompatibilities

Vapor may form explosive mixture with air. Reacts in air to form a heat-sensitive explosive product @ 60C. Incompatible with nitrates, oxidizers, peroxides, strong acids; strong alkalis; oxidizers, reducing agents; amines, moisture. Contact with benzoyl peroxide may cause ignition, fire and explosion. May polymerize if subjected to heat, polymerization catalysts e. g., azoisobutyronitrile, dibenzoyl peroxide; di-tert-butyl peroxide, propionaldehyde); strong oxidizers; or ultraviolet light. May contain an inhibitor, such as hydroquinone.

Waste Disposal

Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must conform to EPA regulations governing storage, transportation, treatment, and waste disposal. Incineration may be allowed.