PVC | PLASTICISERS
solutions, enteral nutrition, and blood. Blood bags made with PVC plasticised with DINCH have been approved in at least one European country for several years. “CE-marked medical devices based on alternative plasticisers are already in use not only on the European market, but are also available in Asia and North America,” Langsch said. At the same conference, Dr Martin Stimpson,
Market Development & Account Manager at Eastman Chemical UK, looked at the suitability for DEHT (which Eastman manufactures as well as DEHP) for blood bags. He started by noting that one of the reasons why DEHP has been so favoured historically by bag makers is that, in addition to doing an excellent job as a plasticiser, it also stabilises the red blood cell (RBC) membrane, resulting in reduced haemolysis and good shelf life. Although DEHP and DEHT are structurally and functionally similar, DEHT (di-(2ethylhexyl) tereph- thalate), which the company markets as Eastman 168 SG, “is distinct from a metabolic and toxico- logical standpoint,” Stimpson said. Stimpson presented results from an Eastman-
supported study, which revealed that all RBC products stored in DEHT plasticised bags showed haemolysis under 1% after 42 days’ storage (Figure 3). Pointing out that further work with a larger sample size is needed to validate performance, he said that, based on this initial study, “the clinical performance of Eastman 168 SG suggests it should be considered a lead alternative plasticiser for PVC blood bags.” In addition, he said that fresh frozen plasma (FFP) products stored in DEHT-plasticised bags for
up to one year tested the same as products stored in DEHP-plasticised bags. “Based on this data, Eastman 168 SG is a potential replacement for DEHP in FFP storage bags,” he said.
The scientific case Back at ExxonMobil Chemical, Global Technical Plasticiser Advisor Didier Naert is campaigning for the use of “sound science” to make the case for plasticisers (preferably DINP, possibly in combina- tion with MB10 to reduce viscosity and boost gelation and low temperature flexibility). He says because PVC and plasticisers are not chemically bound, but rather develop intermolecular forces such as dipole-dipole interaction, dispersion forces, and Van Der Waals forces, an optimum balance between polar and non-polar groups is needed to keep the two together. Ortho-phthalates like DEHP and DINP excel in this regard, with their polarised heads and non-polar tails, with polarising ester groups in the middle. Alternatives such as hydrogenated phthalates, terephthalates, adipates, citrates, and modified vegetable oil all fall short in at least one aspect, he says. “Based on structural interaction and chemical
structure, terephthalates or other alternatives are not able to cover the range of performance offered by HMW phthalates,” according to Naert. “There is an ever-increasing need for plasticiser mixtures; specialty additives are shifting the flexible PVC industry into a foggier and more costly environment.” Consumer products and also technical articles have to be sustainable, Naert said. “Focusing on being non-phthalate does not mean that such plasticisers are automatically more sustainable. From raw material selection up to recycling, many considerations come into play when selecting sustainable plasticisers. We believe that the overall DINP attributes and performance makes it well positioned to address such considerations.”
Figure 4: Gelation behaviour of an Elatur CH / DPT mixture (2:1) is almost on the level of DINP (Vestinol 9 is DINP; INB is isononyl benzoate; MB10 is isodecyl monobenzoate; 2088 is a reaction mass of several olefin glycol dibenzoates; DBT is dibutyl terephthalate; ATBC is acetyltributylcitrate Source: Evonik
22 COMPOUNDING WORLD | August 2018
Alternative options But DINP producers are not putting all their eggs in one basket. Discussing innovations to meet regulatory and economic challenges at AMI’s PVC Formulation 2018 conference in Cologne in April, Dr Hinnerk Becker, Head of Marketing Segment Plasticisers at Evonik Performance Materials, introduced Elatur CH cyclohexanoate. He said this is a non-phthalate alternative to DINP. Its properties can be boosted by fast fusers, also made by the company. Becker pointed out that DEHP stands out for its high gelation power. DINP, the best alternative to DEHP, has lower gelation power, and other alterna-
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