Discovered during the 19th century, and industrialised in the first half of the 20th century, methacrylates form a family of monomers comprising methacrylic acid (MAA) and its esters derivatives.
Methacrylates are used as building blocks to make a wide range of polymers. These polymers are then used as raw materials or components in the manufacture of a wide range of formulations or objects that we use in our everyday life, especially when stability, durability, hardness and scratch resistance are needed. Today, it is estimated that more than three million tons of methacrylates are produced and transformed every year in the world.
Methyl methacrylate (MMA) is by far the most produced methacrylate monomer. Its versatility allows it to be used to produce a pure homopolymer (poly-methyl methacrylate or acrylic glas – PMMA) or, in combination with other monomers, to obtain a series of polymers with various and valuable properties. Other methacrylate monomers are produced by using MMA as a key raw material.
MMA can be manufactured using different industrial processes based either on ethylene (C2), Ppopylene (C3) or isobutylene (C4) petrochemical feedstock. In Europe, MMA is industrially produced from acetone cyanohydrin (ACH), itself obtained from acetone (C3) using a process known as the ACH Process.
The main applications of MMA are:
- PMMA also called ‘acrylic glass’ is a highly transparent long lasting plastic which is used in many end products and appliances where it stays for a long time with unchanged properties. Hardly any other plastic can provide these unrivalled properties (optical transparency, stability against sunlight and air-oxidation, no discoloration). Of specific interest is the ability of PMMA to split back into its monomer under suitable conditions (Back-cracking) thereby offering excellent recycling opportunities.
In the form of pellets or beads, PMMA can be moulded into an almost infinite range of end use products such as: rear-lights and instrument clusters for vehicles, appliances and lenses for glasses.
PMMA in the form of sheets, affords shatter resistant panels for building windows, skylights, bullet proof security barriers, signs & displays, sanitary ware (bathtubs), LCD screens, furniture and many other applications.
PMMA sheets can be produced as cast sheets (direct polymerisation of MMA) or as extruded sheets using molten PMMA beads or pellets as starting material.
- Coating Polymers (or Coating Resins) made based on MMA and other co-monomers like butyl methacrylate, butyl acrylate and some other (meth)acrylates provide outstanding stability against environmental conditions Therefore they are preferred for long lasting high quality applications like protective coatings highly resilient to weather, sunlight and other factors that can cause failure of other types of coatings. This durable property is important in all applications and contributes positively to the reduction of the (sustainability) footprint of these paints and coatings.
Relevant examples are residential, road-marking and industrial paints as well as powder coatings and inks. Some coating systems are also made of formulations that are directly polymerised on site. Methacrylates provide access to end use coatings that can be applied with reduced emissions of volatile organic compounds (VOCs).
- Other methacrylates:
MMA is a raw material for the manufacture of other methacrylates. These derivatives include ethyl methacrylate (EMA), butyl methacrylate (BMA) and 2-ethyl hexyl methacrylate (2-EHMA) which are mainly found in various types of coating polymers or formulations to which they bring some unique properties. Methacrylic acid (MAA) is used as a chemical intermediate as well as in the manufacture of coating polymers, construction chemicals and textile applications.
Because of the wide array of valuable properties it affords, MMA –often in combination with other methacrylates- can be used in many other applications, notably as plastics modifiers and processing aids, medical equipment and dental objects (fillings, dentures, bridges, dental prosthetics). It is a key ingredient in the manufacture of artificial marble and is also found in the composition of products adding value to several other industries including electronics, paper, leather, floor polishes or adhesives and sealants.
The CEFIC Methacrylates sector group – MSG
The MSG is a trade group comprising the manufacturers of methacrylic acid, its basic esters and specialty esters, and polymethyl methacrylate (PMMA) in Europe, in accordance with Article 32 of Cefic statutes and by-laws
MSG members are:
The group is managed by Philippe Salemis, Sector Group Manager – tel. + 32 2 676 7436.
The Methacrylate Sector Group aims at:
- Promoting the standing of the methacrylates industry (methacrylate monomers and PMMA) in a socially responsible manner
- Informing consumers and those involved in the handling of these products on their properties and functionalities
- Encouraging the safe and proper use of methacrylates by developing and publishing appropriate technical information
- Maintaining a high level of technical understanding by identifying and managing research into health and environmental effects and assessing risks in use
- Presenting scientific data and studies on methacrylates to the industry, authorities and the public to better understand the Tox and Ecotox properties
- Developing a common position on major issues of the industry for presentation to regulators, opinion leaders and other concerned bodies
- Developing product stewardship programmes following the Responsible Care principles
The MSG works closely with the Methacrylate Producers Association, Inc. (MPA). This American association was formed in 1987. Its members are: Arkema Inc., The Dow Chemical Company, Evonik Cyro and Lucite International. MPA member companies work jointly to address important Health, Safety and Environmental issues involving the basic methacrylate monomer products.
Methacrylate monomers are reactive products which must be handled in appropriate ways. Methacrylate ester hazards include skin sensitisation, combustibility, and potential for rapid polymerisation which generates heat. Methacrylic acid (MAA) hazards include corrosivity, combustibility, and potential rapid polymerisation which generates heat.
In order to manage these hazards please refer to the Safe Handling Manuals.
Health & Safety
MSG and MPA, based upon about 60 years of experience in the safe handling of these chemicals, have prepared Safe Handling Guidelines for methacrylic acid and the methacrylate esters (MMA, EMA, BMA and 2-EHMA). These documents provide product stewardship advice for the safe storage, handling and use of these products. Along with the Safety Datasheets provided by each supplier, they should be read and understood before ordering, storing and using methacrylates.
- Methacrylate Esters – Safe Handling Manual
- Methacrylic Acid – Safe Handling Manual
- Guidance on Proper Protective Gloves (in preparation)
Because methacrylate esters are contact allergens, the use of un-reacted liquid monomers in mixtures which are intended to come into contact with skin or nails, e.g. nail sculpting, is not recommended. More information on methacrylates and human health can be found on the MPA website.
MSG is contributing with other non-European producers of methacrylates to the activities of a consortium –the Methacrylates REACH Task Force- for the preparation of the registration dossiers within the framework of the REACH Legislation.
The Methacrylates REACH Task Force successfully completed the registration of the lower methacrylates (MAA, MMA, EMA, nBMA, iBMA and 2-EHMA) as a group of related esters (or category) for high production volume chemicals (>1000 tpa). The registrations included the conduct of several studies to meet data requirements for compounds in the highest tonnage band, a comprehensive hazard assessment for each compound, as well as an assessment of safe handling conditions for identified uses of each compound.
Actually the Task Force is working towards registration of specialty methacrylates before the 2nd registration deadline under REACH.
For further information contact Ms E Hunt, Methacrylates REACH Task Force Administrator.
CO2 Emissions Trading Scheme (ETS)
Launched in 2005, the Emission Trading Scheme (ETS) is designed to curb C02 emissions in the EU through a “cap and trade system”. Companies emitting more than foreseen either have to purchase permits to make up for the excess (auctioning), or invest in low carbon technology or reduce their production. Phase Two of ETS started in 2008, committing Europe to reduce its greenhouse gas emissions by 20% by 2020. Phase Three (2013-2020) includes more sectors and greenhouse gases. Currently there is on-going debate on further reducing to 30% by 2020 and additional emission cuts by 2050 (Low Carbon Economy Roadmap).
Industrial Emissions Directive (IED)
The existing Directive on industrial emissions, the Integrated Pollution Prevention and Control (IPPC) Directive, adopted in 1996, fixes the rules for granting permits to operate industrial installations. The objective is to provide a high level of protection of the environment as a whole.
- An integrated approach considering the emissions from the installation to the different environmental media (air, water and land).
- Setting the permit conditions (essentially Emission Limit Values – ELVs) based on the performance that can be achieved through application of the Best Available Techniques (BATs). BATs are established techniques which are the most effective in achieving a high level of environmental protection as a whole and which can be implemented in the relevant sector under economically and technically viable conditions, taking into account costs and advantages.
- Flexibility i.e. taking into account the technical characteristics of the installation concerned, its geographical location and the local environmental conditions.
Health / Occupational Exposure Limits Regulations
Sustainability, also known as Sustainable Development, is a pattern of resource use that aims to meet human needs while preserving the environment so that these needs can be met not only in the present, but also for future generations.
Methacrylates have properties that constitute key assets in terms of sustainability. Examples include:
- Recycling or reuse of some raw materials. For instance, the sulphuric acid commonly used in the ACH Process for MMA manufacturing can be recycled (regenerated) and re-used in the same process. Alternately, this used sulphuric acid can be transformed into ammonium sulphate, a valuable fertiliser, so that the same sulphuric acid molecule served to the manufacture of two products.
- When heated in appropriate conditions, PMMA splits back into its starting monomer, MMA. This back-cracking is used industrially to recycle PMMA and to produce some MMA which can be used again.
- Long lasting stability: The outstanding chemical stability very often ensures a service time beyond 10 or even 20 years. Compared to other chemicals, the respective footprint over the life time is obviously much lower. There are numerous examples such as PMMA glazing for e.g. greenhouses, garden deck roofs;. rear lights in cars;, methacrylate based architectural coatings). These properties allow methacrylates to make up the major part of the finished goods part.
Life Cycle Assessment (LCA) is a methodology that allows quantifying the environmental aspects and other potential impacts associated with a product, process or service from its beginning (cradle) until its end (grave) or re-use (cradle again). The procedures of LCA are part of the ISO 14000 environmental management standards under ISO 14040:2006 and 14044:2006.
MSG believes that LCA contributes to take more informed decisions through a better understanding of the human health and environmental impacts of products, processes and activities related to, or derived from, methacrylates.
The member companies of the Cefic MSG are in agreement to join efforts and work on widely agreeable standards concerning sustainability topics. The member companies recently made comprehensive studies within their proprietary scope to establish up-to-date LCA data. MSG intends to share these results as well as the underlying methodology with other industry organisations like Plastics Europe to ensure reliable and widely accepted sustainability data in the public domain. Beyond that, the methacrylate industry is a strong advocate in supporting cradle-to-grave investigations for prominent application examples where methacrylates prove to ultimately contribute to favourable sustainability footprint.
The EPD and Eco-profile for MMA were released in March 2014. The detailed report, EPD and datasets are available from the PlasticsEurope webpage.The Eco-profile for PMMA in Market Communication (2016) has been completed and is now downloadable.
Relevant studies and literature
- Methacrylate Esters – Safe Handling Manual
- Methacrylic Acid – Safe Handling Manual
- PMMA Ecoprofile (Plastics Europe)
- OECD SIDS Methyl methacrylate
- OECD SIDS Methacrylic acid
- OECD SIDS Category Short-chain alkyl methacrylates
- ECHA REACH Dissemination MMA – EMA – nBMA – iBMA – 2-EHMA
- Betts CJ, Dearman RJ, Heylings JR, Kimber I, Basketter DA. 2006. Skin sensitization potency of methyl methacrylate in the local lymph node assay: comparisons with guinea-pig data and human experience. Link
- Franz R, Brandsch R, 2012, Migration of acrylic monomers from methacrylate polymers –establishing parameters for migration modelling, submitted for publication in Packaging Technology and Science
- Staples C.A., Farr C., Hunt E. K., McLaughlin J.E., Müllerschön H., Pemberton M.A., 2009, Using Quantitative Structure–Activity Relationships to Support the Assessment of the Environmental, Fate and Aquatic Toxicity of a Series of Methacrylic Acid Esters, Human and Ecological Risk Assessment, 15: 503–525. Link