From castor oil to a range of renewable polyamides

From castor oil to a range of renewable polyamides

Patrick Borg, Bernard Pees, Frederic Malet
ARKEMA - F 27470 SERQUIGNY

In the middle of the 30’s, the French chemists have succeeded to synthesize a polymer from castor oil. This polymer, more commonly called "PA11", is a polyamide marketed under the trade name of Rilsan®. The unique combination of high performance properties allows to use this Bioplastic in a wide range of highly demanding applications including packaging, automotive and truck (air brake tubes, fuel lines), oil and gas (off shore flexible pipes), sporting equipments (soles for sport shoes, ski top layers), textile, cable and electrical components.

As early as 1947, this polyamide, made from renewable sources, was sold under the name of Rilsan®. First, it was used to create long, fine, resistant threads which were converted into synthetic fibres to compete Nylon® 6 and 6.6 oil-based polyamides. Then quickly, the use of Rilsan®, found other applications. Today, the PA11 is widely used in high-value added applications with great technical and resistance requirements ; PA11 delivers an outstanding level of chemical, thermal and impact resistance over a wide range of flexibility. PA11 is used as a cost effective replacement of metal or rubber in highly technical applications.

Present in Castor Oil at 85% in the form of triglyceride ester, ricinoleic acid can be converted according to two separate processes.
First, alkaline pyrolysis process leads to both 2-octanol (8 carbons) and sebacic acid (decanedioic acid - 10 carbons).Both find find applications in many fields,i.e. solvent, lubricant, plasticizer, hydraulic fluid, cosmetic, etc.. Sebacic acid is also a component of bio-plastics.
A second process currently used by Arkema, consists in cracking methyl ricinoleate to get in one hand heptaldehyde - source of co-products with 7 carbons such as heptanoic acid, heptanol - and in the other hand methyl undecylenate that leads by successive transformations to 11-aminoundecanoic acid (11 carbons), the PA11 monomer.

Arkema, leading consumer of castor oil, enhances all the co-products of the Rilsan® and pebax Rnew® manufacturing processes. Heptaldehyde and heptanol, 100% linear chain saturated fatty bio-based chemicals, can be used as a synthesis intermediate in fragrance and aroma industries, and as plasticizers for polymers. Heptanoic acid is used primarily in the form of salts for aqueous anticorrosion or in the form of esters for industrial lubricants (aviation, refrigeration, ..), plasticizers and flavors. The properties of methyl undecylenate and undecylenic acid make them interesting molecules that found applications as such or as a precursor for flavors, fragrances, pharmaceuticals, hygiene products and cosmetics. But they can also be used in formulations requiring anti-odor properties. Undecylenic acid is well known for its bioactivity against some fungi and bacteria. Finally, all the methyl esters of linear fatty acid presents in Castor Oil and separated from methyl ricinoleate are gathered in an unique biodegradable product, Esterol A, that has a wide range of applications : solvents, cutting oils, fat liquors for leather treatment, textile oils, mold-release formulations for concrete, anti-foaming agent and all greasing/lubricating formulations.

Actually, every last drop is put to good use, often replacing petrochemical-based products.