Types of Phthalates
The family of phthalate esters are by far the most widely
produced plasticisers worldwide. Both ortho-phthalic and
terephthalic acid may be reacted with an alcohol to produce
phthalate esters which may be used as plasticisers. In practice,
terephthalates are more commonly used in the USA than
elsewhere.
Phthalate esters are manufactured from alcohols such
as methanol and ethanol (C1/C2) up to iso-decanol (C13),
either as a straight chain or with some branching. The reason for
this large variety of phthalates is in order to rpovide a wide
range of different properties for different uses. Please see
list of phthalates in common
use.
Just over one million tons of phthalates are produced in Western
Europe each year.
Di-2-ethylhexyl phthalate (DEHP)
Di-2-ethylhexyl phthalate (DEHP) (CAS No 117-81-7) is also known
as di-octyl phthalate (DOP). In Western Europe it accounts for
about 20% of all plasticiser usage. It is the phthalate ester
of the alcohol 2-ethyl hexanol, which is normally manufactured from
propylene via the dimerisation of butyraldehyde.
The widespread use of DEHP plasticiser is a reflection of its
all around plasticising performance and its provision of adequate
properties for a great many cost-effective, general purpose
products. Some concerns have been periodically raised as to the
potential health effects of this substance but recent assessments
have confirmed that the exposure of the general population to DEHP
gives no cause for concern1
For more information please refer to the DEHP Information
Centre
Di-isononyl phthalate (DINP) and Di-isodecyl phthalate
(DIDP)
Together, these two plasticisers (DINP: CAS Nos: 68515-48-0 and
28553-12-0 EINECS Nos: 271-090-9 and 249-079-5 and DIDP: CAS Nos:
68515-49-1 and 26761-40-0 EINECS Nos: 271-091-4 and 247-977-1)
account for around 60% of all plasticiser use in Western
Europe.
They are produced by esterification of "oxo" alcohols of average
carbon chain length nine or ten. The "oxo" route differs from the
2-ethylhexanol route in that the alcohol for subsequent
esterification is produced through the carbonylation of an alkene
(olefin) rather than the dimerisation of butyraldehyde. The
carbonylation process adds a carbon unit to an alkene chain by
reaction with carbon monoxide and hydrogen with temperature,
pressure and catalyst. In this way a C8 alkene is carbonylated to
yield a C9 alcohol; a C9 alkene is carbonylated to produce a C10
alcohol. Due to the distribution of the C=C double bond in the
alkene and the varying effectiveness of certain catalysts, the
position of the added carbon atom can vary and an isomer
distribution is generally created in such a reaction, the precise
nature of this distribution being dependent upon the precise
reaction conditions. Consequently these alcohols are termed iso
alcohols and subsequent iso-phthalates. The C9 and C10
iso-phthalates are commodity general purpose plasticisers.
For more information please refer to the DINP Information
Centre and the DIDP Information Centre
Speciality phthalates
Other phthalates are produced to meet specific application
requirements . For fast-fusing applications, where foams are
rdequired, BBP, DIHP, DIBP and DBP are used.
For low viscosity applications and where good low temperature
flexibility is required the linear and semi-linear phthalates are
used (e.g. L911P and L810P).
For high temperature use (high performance cables for example)
DTDP and DIUP are preferred.
For more information please refer to the BBP Information
Centre and the DBP Information Centre
References
-
EU risk assessment conducted by EU member state technical
experts under the auspices of the European Chemicals Bureau (ECB).
Publication of the risk assessment report is expected in late
2005.
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