Part 1 – options and commercial sources
In polymer chemistry, emulsion polymerization is a type of radical polymerization that usually starts with an emulsion incorporating water, monomers, and surfactants. The most common type of emulsion polymerization is an oil-in-water emulsion, in which droplets of monomer (the oil) are emulsified (with surfactants) in a continuous phase of water. Emulsion polymerization is used to make several commercially important polymers. Emulsion polymerizers typically cover many different monomer combinations, stabilizing systems and end-target applications.
Manufacturers are coming under increasing pressure from direct customers, end consumers, competitors and regulatory bodies to improve the sustainable development of their operations. A 2010 study by the European Polymer Dispersion and Latex Association (EPDLA) concluded that 80-90% of the environmental impact of an emulsion polymerization business can be directly attributed to the raw materials consumed. While a polymer manufacturer can still improve business sustainability by other means – such as reducing water usage, greenhouse gas emissions, net waste and non-renewable energy consumption during manufacture/transport – the most effective route towards becoming truly sustainable is clearly to research, develop and promote more sustainable monomers and other raw materials into the marketplace.
Materials Options
Isobornylmethacrylate (IBOMA)
Isobornyl Methacrylate is a chemical compound primarily used as a monomer in the production of various polymers and coatings. It is derived from isobornyl alcohol and methacrylic acid and is commonly used in the adhesives, paints, and coatings industries. IBOMA offers excellent adhesion, high gloss, and low volatility properties, making it a favored choice for many end-use applications.
IBOMA is under consideration as a partial replacement for hard monomers such as styrene. Increased hardness and higher glass transition temperatures are two key properties. Unlike hard polymers made with methylmethacrylate, those using IBOMA are not brittle. This enhances the flexibility of the coating making it resistant to cracking and crazing.
Because of its molecular structure, IBOMA polymer has excellent light, fresh reflection, abrasion resistance, medium resistance and weather resistance, and its hygroscopicity is lower than MMA (methyl methacrylate). In addition, the acrylic resin with IBOMA has good compatibility with polyester, alkyd and many volatile paint film-forming substances.
When IBOMA is used in powder coatings, its copolymer can improve the agglomeration of powder, improve the stability of powder coatings and reduce the melting viscosity, thus improving the levelling of coatings and improving the appearance and luster of coatings.
IBOMA is readily manufactured from renewable non-food chain resources such as camphor or pinene. This makes it a more sustainable alternative to other hard monomers such as methylmethacrylate and styrene made from petroleum feedstocks.
IBOMA is 71% biorenewable content with a (homopolymer) Tg of 150°C. When incorporated into a co-polymer with compatible monomers, IBOMA can provide many property improvements to coating and adhesive formulations.
The increased flexibility of IBOMA-containing polymers and the bulky isobornyl group on which it is based enhance coating adhesion on various substrates, including metals, wood and plastics. Improved adhesion may eliminate the need for primers and increase the corrosion and moisture resistance.
The future outlook for the Isobornyl Methacrylate (IBOMA) Market appears to be promising. The market is expected to witness significant growth during the forecasted period due to the increasing demand from the construction, automotive, and packaging industries, among others.
2-Octyl Acrylate (2OA or 2-OA)
2OA is produced by a patented process involving the reaction of 2-octyl alcohol – as a waste product from castor oil-derived alkyd synthesis (the castor oil itself only grown in areas unsuitable for food crops) – with acrylic acid to form 2-octyl acrylate, with an established biocontent of 73%.
The monomer is inherently hydrophobic in nature compared to (eg n-butyl acrylate (BA)), and therefore would be expected to show advantages in terms of water resistance properties over the oil-based BA monomer. 2OA has a Tg of −44 °C, and therefore it is a potential alternative to either n-butyl acrylate or 2-ethylhexyl acrylate (2-EHA).
In contrast to IBOMA, although 2OA has been extensively cited in patents, little work can be found in the open literature. The most exhaustive work was done by Badía et al., where they developed mostly pressure-sensitive adhesives (PSAs) not only with 2OA but also with IBOMA as main monomers. They also showed that to substitute the traditional MMA/2-EHA system by the bio-based IBOMA/2-OA pair, adjustments in the amount of chain transfer agent (CTA) were necessary in order to get similar properties. The homopolymerization of 2-OA was studied in more detail by Barrenetxe et al., and they found that 2-OA was more prone to branching and crosslinking reactions than 2-EHA when both monomers were homopolymerized under the same conditions.
Commercial Sources
The main bio-based monomers isobornyl methacrylate (IBOMA) and 2-octyl acrylate (2-OA) are respectively produced by Evonik industries and Arkema (France), respectively. Bio-based versions of IBOMA, for example, Visiomer® Terra IBOMA from Evonik are commercially available.
Sinomer® IBOMA, available from the Sinocure Chemical Company, is suitable for manufacturing high Tg thermoplastic acrylic resin. Its products have high hardness, high alcohol resistance and heat resistance, and have good flexibility, adhesion, moisture resistance and weatherability. It is a new type of acrylate monomer with special structure. It is suitable for manufacturing soft plastic film coatings such as PET, PE, PP, etc. And decorative protective coatings for PE, PP, PC and other engineering plastics.
BASF is expanding its growing portfolio of bio-based monomers with a proprietary process for production of 2-Octyl Acrylate (2OA). The new product is said to underline BASF’s strong commitment to innovation for a sustainable future with 73% 14C-tracable bio-based content according to ISO 16620.
Besides the regular bio-based 2-Octyl Acrylate, BASF has also launched the new product as 2-Octyl Acrylate BMB ISCC Plus. Here, the remaining carbon content is ISCC PLUS certified, and by applying BASF’s biomass balance (BMB1) approach (see Ref 2 and Fig 1), this variant offers a further reduced product carbon footprint (PCF2).
With an industrial-scale production setup at its Verbund site in Ludwigshafen, Germany, BASF has a pioneering role when it comes to producing 2OA in large volumes. This allows BASF to make the bio-based monomer globally available as a raw material.
Fig 1 The BASF biomass balance approach allows fossil-fuel-based raw materials to be replaced by renewable raw materials in BASF’s Production site at Verbund. In contrast, certificated trading completely separates the use of biomass from in-house product manufacture.
Part 2 Biobased polymers for sustainable coatings and related applications
References
- IBOMA – The Wonder Monomer Isobornyl Methacrylate https://www.ulprospector.com/knowledge/14503/pc-iboma-the-wonder-monomer-isobornyl-methacrylate/
- Mass balance approach to accelerate the use of renewable feedstocks in chemical processes
https://www.basf.com/global/documents/en/sustainability/we-drive-sustainable-solutions/circular-economy/Mass_Balance_Approach_Renewable_Feedstocks.pdf.assetdownload.pdf
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