Materials Science

Natural-based lubricants offer high-performance and sustainability for PVC processing

By Dr Sascha Simon, Head of Technical Development – Green Polymer Additives at Emery Oleochemicals GmbH

Dr Sascha Simon, Head of Technical Development – Green Polymer Additives at Emery Oleochemicals, explains how bio-based plastic

Dr Sascha Simon, Head of Technical Development – Green Polymer Additives at Emery Oleochemicals, explains how bio-based plastic additives are helping industries to achieve sustainability objectives.
The demand for smart solutions in the building and construction, food packaging, and automotive industries continues to increase. One important thermoplastic material that has the versatility to function in a variety of applications is polyvinyl chloride (PVC). Typically, the term “sustainable” or “renewable” does not appear in conjunction with PVC when polymers based on lactic acid (polylactic acid – PLA) or starch are used. However, the raw material source might not be the sole criterion when considering the sustainability of different polymers.
PVC has a particularly key role in the building and construction industry. Based on its annual production volume, PVC is the dominant polymer followed by polystyrene (PS) or polyethylene (PE). In this industry, most applications like floorings, sidings or technical profiles, have a working life of 15 years or more. After that, these end products can be sorted, ground and recycled. This allows for a second, and sometimes third, life cycle of the material.
Choosing the proper additives
The nature of PVC can be manipulated by the use of additives. With the foresight that availability of petrochemicals could be limited in the future, Emery Oleochemicals began the development of bio-based additives in the 1950s. The company has since developed a broad product portfolio targeting factors such as improving the properties of materials or facilitating processing. Today, ongoing developments are directed toward the replacement of petrochemical-based additives with natural-based lubricants for a variety of plastic applications.  
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Recently, Emery Oleochemicals introduced bio-alternatives to hydrocarbons based on natural oils and fats. These paraffins and Fischer-Tropsch waxes serve as external lubricants in PVC processing. The aim is to have a lubricating film between the hot metal surface in the extruder and the sticking polymer melt, allowing for smooth transportation of the thermoplastic PVC and reducing the melt pressure at the nozzle. The effect was studied in a test formulation shown in the top section of Table 1. All components were mixed on phr-level (parts per 100 resin) typically used in the PVC industry. In a CaZn stabilized formulation, which included a small amount of filler (chalk), a typical paraffin wax was compared with Emery Oleochemicals’ 100% renewable ester wax, commercially known as LOXIOL G 24. On the extruder, the torque level of the equipment and the melt pressure at two zones was monitored. The torque level indicates if a lubricant works as an internal or external lubricant during processing and how much energy is needed for the fusion and transportation. Melt pressure 1 was measured close to the vacuum zone, while pressure 2 was detected at the nozzle. As outlined in the Table, both materials showed similar behaviours during processing. This provides a processor with the opportunity to use a natural-based product as a 1:1 alternative to a conventional petrochemical additive.
Montan waxes are a by-product from lignite harvesting. The process to obtain the source material requires many steps including chromic acid bleaching. Since availability is highly dependent on the lignite layer, and because hazardous chemicals are necessary to purify it, price fluctuations in the market were common. The need to find an alternative to montan waxes has become prominent in recent years. Emery’s goal was to duplicate the performance of montan waxes using more sustainable options to process PVC, but the research not only revealed that natural-based alternatives show comparable performance to fossil-based additives for PVC processing – natural-based products can also deliver advantages in availability and handling. The synthesis started from natural fatty acids combined with polyols to build up ester structures capable of mimicking the effect of lignite-based counterparts. Various solutions with different composition tailored for the individual applications were introduced. These natural-based alternatives are being used today in the packaging segment to produce highly transparent films for pharmaceuticals and in boxes for electronics.
What’s next?
Substitution of petrochemicals with natural-based solutions will help industries to achieve sustainability objectives. Ester chemistry using natural fats and oils, and the pure fatty acids gained from them, provide ideal raw materials to produce tailored solutions.
By making use of natural raw materials which will still be available 100 years from now, and by creating tailored solutions for a specific polymer application, bio-based plastic additives are now recognised as more than a passing trend. Emery Oleochemicals continues to offer the market high-performance, natural-based solutions which are founded by over 60 years of technical expertise and plastics industry knowledge.
Dr Sascha Simon, Head of Technical Development – Green Polymer Additives at Emery Oleochemicals GmbH, Helmut-Neynaber Str. 49, 27612 Loxstedt, Germany

LOXIOL is a registered trademark of Emery Oleochemicals.