ARTICLE
The European Commission asked ECHA (European Chemical Agency) to prepare a restriction proposal for microplastics in 2017. ECHA will answer in January of 2019 and launched a public consultation in the shape of a call for comments and evidence. The deadline to answer this call was established on the 11th of May, 2018. Subsequent to that, ECHA is collecting and analysing all the received contributions from individuals and associations and is preparing a report to be included in the Annex XV of the REACH regulation. EICF Contribution EICF stands for European Investment Casters’ Federation. It was born in 1954 as a forum to bring together the representatives of the European investment casting foundries to discuss developments and advances in the industry. Today it is composed of 117 members from 24 countries that represent foundries, suppliers and research institutions working in the field of investment casting. A summary of the report presented to the ECHA, in the impact to the European Investment Casting industry from this potential ban on microplastics is presented here: Investment Casting, also known as precision casting or lost wax, is a foundry casting process where the metal is cast into expendable refractory ceramic moulds. These moulds are produced using slurries based on alumino-silicates, alumina, silica or zircon bonded with an air-dried silica sol. A series of coats are applied over a wax pattern using slurry dips and refractory stuccoes. After the drying, dewaxing and sintering steps, the moulds are ready for the casting. Wax patterns are produced with mixtures of natural and synthetic waxes, which are produced by injecting the wax into aluminium or steel dies. The use of expendable ceramic moulds provides some outstanding features to investment casting: Intricate castings that cannot be produced with conventional process, almost near net shape components with tight dimensional tolerances, possibility of casting any metal alloys, exceptional surface finish and accuracy and large flexibility in the geometry and size of the castings. The main markets for this process in Europe are aerospace, energy, defence biomedical and automotive and Europe has a share of around 25% of the total world market of $14,000 M. Use of Microplastics in IC The production of the wax pattern is an essential step in the entire complex investment casting process as it guarantees the geometry requirements and surface conditions of the final component. Investment casting wax is a mixture or natural and artificial waxes, resins and different additives. One of the latter is a microplastic called XLPS or Crosslinked Polystyrene. It is presented as XLPS beads with a size range of 0 – 400 microns. XLPS can be present within engineered waxes up to 45% weight volume. XLPS is used to create dimensionally robust wax parts. All other wax components are deemed not to fall into the category of a microplastic. Cross-Linked Polystyrene (XLPS) is supplied as hard opaque spherical beads with a particle distribution normally of the order of 0 – 400 microns, with an average mean of 70 microns. XLPS is non-biodegradable and has a melting point of 270 degrees Celsius and has a CAS Number of 9003-70-7. The usage of XLPS filler enables the Investment Casting foundries to economically produce tight tolerances metal parts for the aerospace, energy, automotive, medical and general industry. The main function of XLPS is to provide dimensional stability to the patterns and contribute to a correct dewaxing step. It is used in more than 95% of the waxes for investment casting due to is unique properties and there are not real alternatives to it. Other products that have been used to try to provide the same performance to the wax in the past also contain microplastic, there is no real alternative for the product and furthermore the impact of the elimination of XLPS for investment casting usage would be hugely negative in economic and technical terms for European foundries. It is deemed that as the XLPS particles are encapsulated by wax and resin there is no risk of flushing out into the aqueous systems/drainage. The investment casting waxes are recycled, disposed of in landfill or burnt at the end of the life cycle. The current intentionally broad definition of “microplastic” in ECHA’s Call for Evidence would include some important investment casting wax additives. It is also useful to note that ECHA’s Q&A recognises that uses that do not result in release microplastics into the environment should not be subject to a Restriction (answer A.10 of ECHA’s Q&A from the online information session 12 March 2018). The use of polymer additives in the lost-wax investment casting process does not contribute to release of the polymer additives into the environment because the particles are embedded into a matrix of wax during use. Therefore, EICF requests not to include XLPS in the list of microplastics to be restricted in its use, at least in the investment casting sector. Specific Information Request XLPS stands for crosslinked polystyrene and is used as an additive in the formulations of the waxes used to produce the wax patterns in the investment casting process. It is a unique material that provides dimensional stability, reduction of shrinkage of the wax models, prevention of cavitation shrink holes in wax models increase of the strength in wax models and the required flowability to the wax and has no real substitutes. In investment casting applications it is exclusively used encapsulated or embedded in wax matrices (consisting of paraffins, resins, polymer bases, hard waxes etc.) with no possibility of free flowing. Following some features of XLPS are provided: i. Chemical name: Cross linked PolyStyrene (XLPS); Polymer Structure: Styrene/Divinylbenzene; Physical Form: Transparent beads.0-400 microns; Odor: No odor; Reactivity: Chemically inert; Moisture Content: 1% max.; Specific Gravity: 1.02 to 1.05 gr/cm3; Bulk Density: 0.63 to 0.7 gm/ml Thermal Stability: 200º C (392º F); Maximum Ash Content: 0.05% max. ii. XLPS is used between 5 to 40% as filler material in an Investment Casting wax formulation in combination with resins, waxes and additives. iii. XLPS is used as particles of 0 to 400 micron in the casting wax formulation. The particle shape can be spherical (beads) or irregular (ground material). iv. XLPS has no solubility in water and decomposes above 200ºC. XLPS is chemically inert as is the function of a filler in the application. v. XLPS has no or very slow biotic degradability. vi. XLPS is used around 2000 MTA as filler in investment casting wax in the EU. vii. Investment casting waxes with incorporated XLPS filler are after usage either recycled or disposed of according to regulations at the end of the life cycle. As the XLPS particles are encapsulated with wax and resin there is no contact with water or flushing out into the drainage system. XLPS is an ideal filler for Investment Casting waxes as it reduces cavitation in the wax pattern, increases the setting and the window of operation. XLPS is chosen based on: • Low thermal conductivity • Ideal density, close to wax/resin mixture which prevents settling • High thermal stability (>200º C) • Low thermal expansion • Low in inorganic components There is not really any suitable alternative. XLPS is nearly unique. 95% of waxes use XLPS due to its outstanding properties. Any restriction on the use of XLPS material in investment casting wax compounds would have a dramatic effect on the production and quality of the finished castings manufactured within the industry. There are currently no equivalent filler materials that can be used. The other options are also microplastics that are essential to control thixotropy of the wax (complexity of components). The technical advantages of XLPS based products create a competitive advantage and gain market share compared to previous known fillers as Terephthalic acid (PTA) and water. The use of other known alternatives would jeopardize the European investment casting industry and associated sectors due to the economic impact of the new validation and certification processes that aeronautical components have to comply with and the investments required to produce new wax injection moulds and adapt the production to the features of any currently available alternative. If candidates are identified in the future the dimensional aspects provided by the wax would probably change and this would entail the need of huge resources in terms of time and investments to adapt the moulds to the new materials in terms of certification and validation of aeronautical components (the main market of IC in Europe). The risk of outsourcing the production to countries were the directive would not apply is real for some non-critical components even though this outsourcing is not possible in many other cases due to the risk of disrupting the supply of critical strategic Defence and aeronautical components due to confidentiality issues and defence strategy. It should be noted that XLPS is widely used in water softening treatment, paint manufacture, tyre manufacture, oil drilling lubricants and numerous other applications. It is true that other alternatives may exist for these other applications but this is not the case for the application of XLPS as a filler for the wax in the investment casting sector. Investment casting industry is a strategic industrial sector for Europe. Also called precision casting it provides components that cannot be produced by any other casting processes due to the nature of the expendable moulds. The impact of a restriction in the use will affect over 95% of pattern wax supplied to the Precision Investment Casting Industry. The PIC industry supplies XLPS containing material to critical industries including aerospace, energy generation and medical prosthesis. These industries rely on XLPS filled wax product to create their products for the final customer. These processes are fixed processes with no changes to raw material allowed by the suppliers. A change to the restriction on microplastic use within this industry could have a knock-on effect to supply of finished goods if a restriction was applied. The restriction would lead to loss of employment and of strategical sectors and clients. The total market of IC is 14000 million of dollars and Europe has an important share of around 25% of it, i.e. around 3100 million and 95% of the components produced in Europe are made with waxes containing XLPS. Conventional methods used in the characterization of polymers can be used to identify microplastics. The high % of microplastics within the wax and its size allow its identification through infrared spectroscopy, Differential Scanning Calorimetry analytical processes where the peak corresponding to Polystyrene should be clearly and quickly identified. Conclusion At the end of April 2018, EICF has contributed to the call for comments and evidence launched by the ECHA by filling the questionnaire prepared by the latter. The EICF´s contribution has been submitted online. The main conclusion of the information provided by EICF is that EICF requests not to include XLPS in the list of microplastics to be restricted for its use in the investment casting sector.