'Towards an industrial synthetic route for producing sunflower oil based on plasticizer'
Increasing health concerns in relation to use of phtalates as plasticizers have led to the discovery of the safer alternative Grindsted SOFT-N-SAFE (SNS) by Danisco A/S (now known as DuPont Nutrition Biosciences Aps). The main component of SNS is based on acetylated glycerol monostearate, originating from hydrogenated castor oil. Unfortunately, castor oil is too expensive and available in too small quantities for SNS to be a realistic, large-scale alternative to phthalates. This thesis presents a less expensive and more accessible alternative, namely the SNS-analogue (SNS-A) in which the starting material is glycerol monooleate originating from sunflower oil.
Plasticizers are added to polymers to increase fluidity. In the worlds’ third mostly used plastic type polyvinyl chloride (PVC), mainly used in building and construction, phthalates continue to be used as plasticizers. The most widely used phthalate is di(2-ethylhexyl)phthalate (DEHP). SNS, released in 2005, is a 1-1 replacement alternative to DEHP. As SNS is made from vegetable oil, it is fully biodegradable and metabolizes like any other vegetable oil and is therefore fully digestible. SNS is thoroughly tested for environmental and health effects with no harmful effects found. For example, is the no-observed-adverse-effect level (NOAEL) in rats about 1,000 times higher for SNS than for DEHP.
However, a major concern about SNS is the price, as it is 3-4 times more expensive compared with DEHP. Thus, a cheaper alternative with the same safety features would be highly attractive. This has led DuPont Nutrition Biosciences Aps to take interest in the SNS-A from sunflower oil.
In this project a three step synthetic pathway consisting of epoxidation, hydrogenation and acetylation of glycerol monooleate was developed.
The pathway uses an ionic liquid (IL) as reaction media. ILs are salts that are liquid at ambient temperatures – often with melting points lower than 100 degrees C. ILs can act as solvents for chemical reactions and can have a dual function as both catalyst and solvent. Further, ILs have extremely low vapor pressure, which minimize solvent emission and thus makes it easier to reuse them efficiently.
Having considered several ILs the choice fell on trihexyltetradecyl phosphonium bis(trifluormethylsulfonyl) amide which showed favorable phase separation properties allowing a homogeneous epoxidation and hydrogenation reaction. The method was shown to provide satisfying results, but additional development will be needed to establish an industrially viable process protocol. A patent has been filed for the process.