ARTICLE
Auteur(s) : Patrick Borg, Guillaume Lê, Stéphanie Lebrun,
Bernard Pées
Pôle Synthèse des Matériaux, Groupe IPOM-LSM 6, 27470
Serquigny, France
Nature owes a lot to Castor Oil... starting with beavers.
Indeed, very long-time hunted for their fur and Castoreum
exploitation, they owe their survival to the replacement of
Castoreum by Castor Oil for its medicinal “virtues” and many
applications in perfumery. From the latin word castor, Castor Oil
keeps only the name in memory of its applications, but it has
absolutely nothing in common chemically. Regarding the name
ricinus, it is in reference to the similarity between Castor Beans
and ticks that the Swedish naturalist Carolus Linnaeus was giving
scientific name to ricinus communis plants over 200 years
ago.
Despite all these links with the animal world, Castor Oil is a
product of plant origin. Castor Oil is obtained from Castor Beans
Plants mainly cultivated in sub-tropical regions (India, Brasil,
China) that fructifies all along the year (several harvests in a
year) and is drought resistant. It is a robust culture (very few
pesticide), Castor Beans Plants can be grown on poor soil in semi
arid areas, do not compete with local food crops nor contribute to
deforestation. To ensure only ripe seeds collection harvesting is
done manually (mechanization is very limited).
Castor Oil is obtained by crushing Castor Beans seeds that come
from Castor Plants where they are located in Spiny Seed Pod. It is
obtained either by cold-pressing or by solvent-extraction of seeds
containing 40 to 60% of oil. Ricin is a toxin present in the
seed and plant but due to its high hydrophilic behavior it is not
soluble in oil. Then it concentrates in the Oil Cake that is
heat-treated (125 °C/25 min) to destroy the toxin and
valorized as organic fertilizer for biological agriculture or used
as a feedstock for livestock. In conclusion, Ricin is not found in
oil.
Castor Oil is not used for human feeding. Known since antiquity,
castor oil has been used in medicine as a purgative laxative
stimulant. Now, it remains present in small quantities as an
excipient in many pharmaceutical specialties. In cosmetics, it is
used as base of beauty oils for hands, body and especially hairs.
It is used under the form of shampoo or hair masks, but also as a
plasticizer in nail polish, lipsticks, creams and lotions, or as
color fixative.
Castor oil has also industrial applications because of its
polyol ester’s structure which acts as a lubricant for engines
operating at very high speed. It is used in the chemical industry
in the polyurethane sector, as a component of polyglycerol
polyricinoleate (emulsifier for food industry), in the manufacture
of lacquers, varnishes, polishes and wax substitutes. It also finds
applications under a dehydrated (DCO), hydrogenated (HCO) or
sulphated (Turkey Red Oil) form.
The originality of Castor Oil relies in its chemical nature. The
specificities come from:
- – The high content (up to 85%) of a particular fatty
acid: the ricinoleic acid.
- – The unique structure of ricinoleic acid: at the
difference of others conventionnal fatty acids from vegetable oils,
it combines a double bond and an additionnal hydroxyl
functionnality inside its linear chain comprising 18 carbon
atoms.
After alcoholysis reaction, a mixture of glycerol and fatty
acids esters is obtained with a high percentage of ricinoleic acid
ester (almost 85%).
Glycerol is a multifunctionnal organic compound, soluble in
water, and is widely used in many application fields: wetting and
lubrificating agent in handcreams, suntan lotions and soaps hair
care, anti-freezing, biobased raw materials for chemical
intermediates such as acrolein, propylene glycol,
epichlorhydrin…
The behaviour of Ricinoleic acid ester when heated to high
temperature has intrigued chemists since 1845. Since that time
Castor Oil chemistry has evolved significantly. The commonly way is
to crack under alkaline conditions (caustic pyrolysis) leading to
capryl alcohol (2-octanol) and sebacic acid (C10 a, w-diacid).
The process in use at the Arkema Marseilles plant is in fact unique
in the world. After alcoholysis reaction with methanol, methyl
ester of ricinoleic acid is cleaved by steam cracking (pyrolysis at
elevated temperature) into two parts giving first a 7 carbon
atoms compound (heptanal) and a 11 carbon atoms compound
(methyl undecylenate) (figure 1).
A whole range of innovative chemistries and end use products are
generated from these base reaction products. These products are
used in every-day life, to improve our comfort and safety but also
in very specific applications with very high technical
requirements.
When 18 = 10 + 8…
As described before, the most practiced way is to carry out the
cracking reaction under alkaline conditions (caustic pyrolysis)
leading to different final products: capryl alcohol (2-octanol) and
sebacic acid (C10 a, w-diacid).
Sebacic acid is a linear saturated 10-carbon dicarboxylic acid.
The major part of world production occurs in China (over
20,000 metric tonnes of exportation, over 90% of global
trade). In the industrial setting, sebacic acid can be used as such
or as an intermediate in lubricants, hydraulic fluids, cosmetics,
candles, aromatics, antiseptics and painting materials. But Sebacic
acid can be used for partially bio resourced polymers: for example,
by coupling with hexamethylene diisocyanate: nylon-6,10.
Furthermore, sebacic acid esters are used as plasticizers for
different polymers and synthetic rubbers (dibutyl sebacate DBS) and
in the manufacture of dioctyl sebacate (jet lubricant and lubricant
in aircooled combustion motors).
The 2-octanol (capryl alcohol) is mainly used as a raw material
to produce caproic acid intermediates in butter, rum, coconut and
fruit flavors. In cosmetics, it is an intermediate for the
preparation of caprylic/capric triglyceride (CCT): a mixed triester
of caprylic and capric acids possessing excellent oxidation
stability (almost indefinite shelf life). CCT is an emollient,
excellent as a superfatting oil in soapmaking and improves
spreading of skincare formulas. Capryl alcohol can be used as a
possible alternate for 2-ethylhexanol or isooctyl alcohol in the
preparation of diesters plasticizers: dicapryl esters such as
dioctyl phthalate (DOP) or dioctyl adipate (DOA). The 2-octanol is
used as a solvent, but it is also employed as a frother in the
mineral froth flotation of silica from iron ore.
When 18 = 11 + 7…
Arkema has developed a whole range of compounds with 11 and
7 carbon atoms derived from a chemistry based on the thermal
cracking of ricinoleic derivatives.
Esterol A: “the remaining C18 part”
It corresponds to the not breaking part after steam cracking. This
product is made up of saturated and unsaturated natural fatty acid
methyl esters like stearic, oleic or linoleic acid. They consist of
C16 and C18 linear chains, identical to those contained
in the common vegetable oils, and are valorized for their value in
the oil & fat markets. Esterol A is mainly used as
machining oils due to its capacity to fix sulphur and a good
ability to prevent scuffing or scoring of metal parts due to good
lubricating properties (oilness, anti-wear properties). It finds a
lot of applications in a large range of domains:
- – Metal working fluids/Cutting oils (lubricity for
anti-wear additive when sulfurized).
- – Fat liquors for leather treatment.
- – Concrete mold release agents (biodegradable, fluid
oil, easy to emulsify).
- – Grease and lubrication formulations.
- – Anti-foam agents.
“The C7 cut” and its derivatives… from perfumes to technical
products
Heptanal, a molecule with 7 aligned carbon atoms, is
appreciated for the olfactory qualities of certain of its
derivatives. In its natural state it was discovered in wine by
oenologists who called it Oenanthol. Other, more technical
qualities were discovered later, including its lubricant properties
thanks to the low freezing point of this chain. Heptanal is a
synthesis intermediate for the fragrance and aroma industry. Its
natural odor is categorized as fresh, green, citrus and is used in
aldehydic and floral compositions. Synthetic jasmine or
jasminaldehyde (ACA: a-n-amyl-cinnamaldehyde) is a perfume aroma
obtained from C7 aldehyde. This aroma is detectable in many
washing powders, soaps, candies and other jasmine perfumed
products. Another perfume aroma made up from heptanal is Folione
(methyl-heptyne carboxylate). With its green, violet, vegetable and
hay like odor, Folione is used in fragrances that require a hay or
straw-like quality.
Heptanal is transformed into 2 new compounds either by
oxidation or by reduction leading respectively to heptanoic acid
and heptanol.
Heptanoic acid has a large variety of applications. It can be
valorized in the form of esters as civil and military aircraft jet
engines lubricant, car motor oil and refrigerant lubricants.
Compared to C6/C8/C10 analogues, linear saturated C7 acid
esters based on trimethylolpropane, neopentylglycol,
pentaerythritol present a better compromise in terms of low
viscosity at low temperature and low volatility at high temperature
due to their lower pour points and higher viscosity indexes. In
addition to lubricant behavior, C7 salts have high efficiency
as corrosion inhibitor for water based hydraulic fluids for
automotive, additives in paints, cutting oils with
C7 monoethanolamides and metalworking fluids. Heptanoic acid
is a chemical intermediate for many application fields as:
- – pharmaceuticals and cosmetics (emollient
agent/surfactant in personal care as propylene glycol diheptanoate,
stearyl heptanoate and in pharmaceutical gel as neopentylglycol
diheptanoate);
- – aromas and perfumes (natural, green grassy and fruity
ester like odor in banana flavors and in coffee, dairy products,
passion fruit…);
- – plasticizers for polymers.
Heptanol is used in the fragrance and aroma industry (trace
quantities are used in perfumes to provide a peach-apricot aroma)
or as a synthesis intermediate (g-decalactone as coconut, vanilla
flavor for dairy products and beverage or esters with fruit notes
like heptyl butyrate, octanoate). It also finds application as
chemical intermediate for plasticizers for polymers.
The “C11 cut” and its derivatives… bifonctionnality and natural
bacterioactivity
They have the rare particularity of being both long and
bifunctional (presence of an carboxylic acid or ester function and
a terminal double bond at the other end of the chain). This
specific structure makes them highly interesting molecules which
can be used on their own or as chemical intermediates for the
design of tailor-made products adapted to a variety of different
needs.
Undecylenic acid derivatives are also widely used for their
natural bioactivity and fungi resistance (C11 chain
integration into phospholipid membranes). In nature, trace
quantities of C11 acid are found in sweat, tears and hair
fats. It is a natural fungicide, which is effective and well
tolerated. It can be used in soaps, shampoos, talcum powders and
other body hygiene products. Under salt form (Zn or Ca), it
combines natural bioresistance properties as well as surfactant
improving physical stability of water based products (cosmetics).
It founds applications in pharmaceuticals for human skincare:
preparations as athletes’ foot, hair-care and anti-dandruff
shampoos, deodorant, beauty creams, (antiseptic) soaps or
bacteriostatic emulsifier for cosmetics. Undecylenic acid
derivatives range is one of the safest, ecological, most economical
and highly effective natural bacteriostatic and antifungal
agents.
Undecylenic acid and methyl undecylenate are used as chemical
intermediates in cosmetic industry and many of their derivatives
enter in personal care compositions as surfactants, like Betain
C11 or Amphoram U (undecylenamido propyl betaine), undecylenic
acid diethanolamid and disodium undecylenamido MEA-sulfosuccinate.
Compared to chemical biocides (imidazoles, tolnaftates) used in
cosmetics, they are safe and natural bacteriostatic agents.
In perfumes industry, undecylenic acid and methyl undecylenate
can be used as such to provide respectively fruity-rosy note and
heavy citrus note (for lilac based perfumes and anti-odors) or as
chemical intermediate for:
- – undecenal for rose or jasmine based formulations, key
component for quality perfumes (fixing agent): quality enhancer for
large volume products;
- – undecenol for volume/natural freshness to floral
compositions (citrus, floral note), effect increasing, especially
in soap formulations;
- – macrocyclic musk: e.g. cyclopentadecanolid
(exaltolide, pentalide, thibetolide).
A bio-renewable source for polymers (figure 2)
In the middle of the 40’s, a group of French chemists succeeded to
synthesize a monomer from undecylenic acid: 11-amino-undecanoic
acid. As early as 1947, they created a new polymer from renewable
sources: “PA11” polyamide, as it is known to chemists, sold under
the trade name of Rilsan®. By coupling
11-amino-undecanoic acid with other monomers, ARKEMA developed a
whole range of biobased polymers combining high performance and
sustainability recognized by the Rnew® suffix.
Rilsan® PA11 is the only High Performance polymer
100% based on renewable resources. For nearly 60 years,
Rilsan® polyamides deliver a unique compromise of
several key physical & chemical properties including chemical
& hydrocarbon resistance, low density/light weight, impact
strength, burst strength, abrasion & scratch resistance,
flexibility, electrical resistance, high temperature service and
long-term ageing. Rilsan® PA 11 resins have earned
a preferred material status in the most demanding applications due
largely to their excellent balance of thermal, physical, chemical
and mechanical properties resulting in an outstanding cost
performance ratio. Processing ease is another major benefit of
Rilsan® polyamide resins: injection molding, extrusion
(fibers, web, tubes, multilayers, laminating, blown film, blow
molding…), or rotomolding. For all these reasons,
Rilsan® PA 11 has been selected by engineers for
markets and applications as diverse as automotive fuel lines,
pneumatic airbrake tubing, electrical anti-termite cable sheathing,
oil & gas flexible pipes & control fluid umbilicals, sports
shoes, rotomolded fuel tanks, textile, etc ...
Rilsan® PA11 can be supplied in pellets but also
in powder form. Rilsan® Fine Powders are unique
thermoplastic Polyamide 11 powders, developed for metal
coating more than 40 years ago, that combine corrosion,
chemical, abrasion cavitation erosion and impact resistance, low
coefficient of friction, aesthetic surface finish
(warm-to-the-touch), compatibility with food products and good
hygienic properties. Rilsan® coating is a proven surface
protection bringing its excellent chemical and mechanical
properties.
The Rilsan Fine Powder® brand has become the global
benchmark in several industries looking for the ultimate metal
protection in the automotive industry, for spline shafts, sliding
door, seat rails, and springs coating, and in the fluids industry,
for pipes, fittings, pumps, valves coating. Other major
applications include coating of dishwasher baskets, printing
rollers, small parts like clips and adjustors for the textile
industry, clips, springs, hinges for the building industry. Beside
coating applications, Rilsan® Fine Powders can also be
used as texturing additives in coil coatings and paints, as well as
in Laser Sintering process.
Pebax Rnew® are plasticizer-free thermoplastic
elastomers belonging to the engineering polymer family. Arkema has
developed the first engineering thermoplastic elastomer range
produced from renewable resources (20 to 94% of renewable
organic carbon). Thanks to their unique chemistry (polyEther Block
Amide – PEBA), by varying the monomeric block types and ratios, it
is possible to achieve a wide range of physical and mechanical
properties such as lightness, flexibility, dynamic properties due
to low hysteresis (alternative flexure), energy return, resilience,
outstanding properties at low temperature (impact resistance, low
rigification), good resistance to most chemicals, etc. Some grades
of Pebax® also bring antistatic properties, the ability
to be impregnated with fragrances, soft-touch, etc.
They are easy to process by injection molding and profile or
film extrusion, and can be easily melt blended with other polymers.
Pebax® is suitable for many applications in markets such
as sports, medical, packaging and industrial applications.
Castor Oil… a vegetal refinery
As a conclusion, every last drop is put to good use, often
replacing petrochemical-based products. Castor Oil derivatives is
actually a vegetal refinery!
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