Note: Descriptions are shown in the official language in which they were submitted.
CA 02342916 2001-03-05
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IMPROVED BROMINATED POLYSTYRENIC RESINS. AND THEIR USE
BACKGROUND OF THE INVENTION
Brominated polystyrenes are well established flame retardants for
thermoplastics.
Generally, brominated polystyrenes are produced by reaction between
polystyrene and a
brominating agent (e. g. , bromine or bromine chloride) in the presence of a
solvent (e. g. ,
dichloroethane) and a Lewis acid catalyst. Heretofore the art has proffered
many processes
which are claimed to produce a superior brominated polystyrene. See U.S. Pat.
Nos. 4,200,703;
4,352,909; 4,975,496 and 5,532,322.
Previously-known brominated polystyrene flame retardants remain deficient in
certain
properties which translate into deficient performance of thermoplastic polymer
blends in which
they are used when the blends are subjected to polymer processing conditions.
For example, prior art brominated polystyrene polymers evaluated for thermal
stability
have exhibited a 1 % weight loss at temperatures less than 336°C when
submitted to Thermo-
gravimetric Analysis (TGA) and most have exhibited a 1 % weight loss at
temperatures around
300 ° C . Such low thermal stabilities are undesirable, especially
under the high temperatures to
which flame retarded thermoplastics formulated with brominated polystyrene
polymers are
exposed during processing.
Corrosion of metal processing equipment such as melt blenders, extruders, and
molding
machines, attributable to the release of hydrogen halide under thermal
processing conditions is
another deficiency of flame retarded thermoplastic polymer blends made using
prior brominated
polystyrene flame retardants. In the presence of moisture, HCl and HBr
released from the
brominated polystyrene in the blend at processing temperatures can result in
acid formation and
consequent metal corrosion.
The bromine content of a brominated polystyrene is the sum of (1) bromine
substituted
on the aromatic portions of the polymer, (2) bromine substituted on aliphatic
portions of the
polymer, e. g. , the polymer backbone or alkyl substituents resulting from
alkylation of the
aromatic portion of the polymer, and (3) any ionic bromine present, e.g.,
NaBr. Alkylation of
aromatic rings in brominated polystyrene is catalyzed by the Lewis acid
catalyst used in
producing the brominated styrenic polymer, with the reaction solvent (usually
a 1-3 carbon atom
dihaloalkane) serving as the alkylating agent. The bromine for (1) is referred
to herein as
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aromatic bromide, while the bromine for (2) is referred to as aliphatic
bromide. Even though
ionic bromine can contribute to the total bromine content, its contribution to
the total bromine
content is small. Nevertheless, as pointed out in U.S. Pat. No. 5,328,983,
ionic impurities in
brominated polystyrene may degrade polymer formulations in respect to their
ultimate electrical
properties, and also may result in corrosion of processing equipment or in the
corrosion of
metallic parts in their end-use applications.
The chlorine content of brominated polystyrenes, like the bromine content, is
chiefly part
of the polymer structure as aromatic andlor aliphatic chloride substituents.
Use of bromine
chloride as the brominating agent is the largest contributor to the chlorine
content. However,
chlorinated solvents and/or chlorine-containing catalysts used in the
production of the brominated
polystyrene may also contribute to its chlorine content.
The aliphatic halide content of the brominated polystyrene is not desirable as
aliphatic
halide is not as thermally stable as aromatic halide and, thus, aliphatic
halide can be easily
converted to hydrogen halide, e.g., HBr or HCI, under normal end-use
processing conditions.
Aliphatic bromide and chloride are generally referred to by the art and
quantified, respectively,
as hydrolyzable bromide and hydrolyzable chloride since such halides are
easily hydrolyzed as
compared to aromatic halides.
To evaluate brominated styrenic polymers for their tendencies to release
hydrogen halide
under thermal processing conditions, use is made of the method described in
U.S. Pat. No.
5,726,252 and referred to therein as the Thermal Stability Test Procedure. In
essence, this
method indicates the content of halogen atoms in the brominated polystyrene
that is not bonded
directly to the aromatic rings and thus is more readily released from the
polymer when at
elevated temperature. The Thermal Stability Test is described in greater
detail hereinafter.
Apart from whether the halide is present as an aromatic or aliphatic halide,
it is also
desirable to minimize total chlorine content of the brominated polystyrene as
chlorine is not as
efficacious or as stable a flame retardant constituent as is bromine.
Additionally, it has been demonstrated that prior art processes for
manufacturing
brominated polystyrene give rise to significant cleavage of the polymer chain.
This cleavage
results in the produced brominated polystyrene having an MW, as measured by
Gel Permeation
Chromatography, which is significantly lower than the calculated theoretical
MW of the
brominated polystyrene. The calculation is based upon the bromine content (wt
% ) of the
brominated polystyrene product and the MW of the polystyrene reactant at
reaction initiation. It
is advantageous if the theoretical M". and the actual MW of the produced
brominated polystyrene
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are close to each other, given the t margins of error for GPC, since such
closeness evidences
a paucity of polymer cleavage. The degree of cleavage should be minimized
since cleavage
results in an increase of alkyl end groups in the brominated polystyrene,
which alkyl end groups
provide loci for the facile formation of the undesirable hydrolyzable halides
discussed above.
Conversely, if cross-linking occurs, the molecular weight of the brominated
polystyrene is
increased, and if not controlled, such cross-linking can result in formation
of insoluble residues
andlor gelation of the reaction mixture. In addition, viscosity specifications
related to end
product usage can be disrupted by such undesirable increases in molecular
weight.
Total halogen content, especially total bromine content, of the brominated
polystyrene is
another important consideration. Pyro-Chek~ 68PB brominated polystyrene flame
retardant
(Ferro Corporation) is reported to have a total halogen content of about 67
wt%. U.S. Pat. Nos.
5,637,650 and 5,726,252 of Ferro Corporation report that Pyro-Chek~ 68PB flame
retardant has
3000 to 6000 ppm of backbone halogen, 5000-6000 ppm being typical. And when
Pyro-Chek~
68PB flame retardant was subjected to the Thermal Stability Test in our
laboratories, it evolved
1960 ppm HBr. In order to provide a brominated polystyrene that melt blends
more easily and
efficiently than Pyro-Chek~ 68PB flame retardant, Ferro Corporation developed
another product
with a lower total halogen content, namely, Pyro-Chek~ 60PB brominated
polystyrene flame
retardant. This product, which has a total bromine content of about 61 wt % ,
is reported to melt
at a lower temperature and to flow more easily during compounding and
processing operations
than Pyro-Chek~ 68PB flame retardant. However, these improvements in melt flow
are
achieved with a reported concomitant reduction in aromatic bromine content of
10 % . Thus, if
anything, the 10 % reduction in aromatic bromine content portends at best no
improvement in
thermal stability and at worst a reduction in thermal stability as compared to
Pyro-Chek~ 68PB
flame retardant.
It would be especially desirable if most if not all of the above-mentioned
disadvantages
of brominated polystyrenes could be avoided or at least minimized. For
example, it would be
of considerable advantage, especially for achieving better electrical
properties, if a more
thermally stable brominated styrenic polymer, e.g., brominated polystyrene,
could be provided
that also has a suitably low ionic bromine content. Another welcome
contribution to the art
would be a brominated polystyrene styrene polymer in which the theoretical MW
and the actual
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MW of the produced brominated polystyrene are close to each other and in which
the content of
ionic bromine is sufficiently low for inclusion in polymers used in electrical
applications, such
as glass-filled nylon polymers.
From another point of view, it would be desirable and advantageous, if a
brominated
styrenic polymer, e. g. , brominated polystyrene, could be provided that has
both improved melt
flow characteristics and improved thermal stability. It would also be of great
advantage if
improved melt flow and thermal stability could be achieved without material
sacrifice of other
important properties, and if possible with concomitant provision of other
desirable properties
such as low ionic bromide content, minimal (if any) chlorine content, and
desirable color and
odor properties.
Also, a need exists for thermoplastics, especially engineering thermoplastics,
and
particularly nylon (a.k.a. polyamide) thermoplastics, flame retarded by a
brominated polystyrene,
having enhanced thermal stability and reduced metal corrosiveness.
This invention is deemed to at least minimize, if not overcome, most, if not
all, of the
above-mentioned disadvantages of brominated polystyrenes.
SUMMARY OF THE INVENTION
In accordance with this invention, new, high quality brominated styrenic
polymers having
suitably low ionic bromine contents are provided. In addition, these new
brominated styrenic
polymers possess or exhibit other superior properties or characteristics
enhancing their utility as
flame retardants for thermoplastic polymers of various types, including glass-
filled polyesters and
glass-filled nylons.
Thus pursuant to a first aspect of this invention there is provided a
brominated styrenic
polymer, preferably a brominated polystyrene, that has (i) a TGA temperature
for 1 % weight
loss which is 340 ° C or higher, preferably within the range of from
340 ° C to 380 ° C, and more
preferably within the range of from 345°C to 380°C, and a
chlorine content, if any, of less than
about 700 ppm Cl, preferably less than 500 ppm Cl, and more preferably less
than 100 ppm Cl,
and (ii) an ionic bromine content of 2000 ppm or less, preferably 1500 ppm or
less, more
preferably 1000 ppm or less, and most preferably 500 ppm or less, all such ppm
levels being
based on the total weight of the brominated styrenic polymer.
Also provided by the first aspect is a brominated styrenic polymer, preferably
brominated
polystyrene, that has an actual M W which is within about 20 % , and
preferably within about 10 % ,
of its calculated theoretical Mw, the theoretical MW being based upon the
actual bromine content
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of the brominated styrenic polymer and the Mw of the styrenic polymer reactant
used to produce
the brominated styrenic polymer, and that has an ionic bromine content of 2000
ppm or less,
preferably 1500 ppm or less, more preferably 1000 ppm or less, and most
preferably 500 ppm
or less. Preferably, such brominated styrenic polymer is also characterized
(i) by containing less
than about 700 ppm Cl, preferably less than 500 ppm Cl, and more preferably
less than 100 ppm
Cl and/or (ii) by having a TGA temperature for 1 % weight loss which is
340°C or higher,
preferably within the range of from 340°C to 380°C, and more
preferably within the range of
from 345°C to 380°C.
The first aspect also provides a brominated styrenic polymer, preferably
brominated
polystyrene, that is essentially free of impurities selected from the group
consisting of (a)
methylene chloride, (b) ethylene dichloride, and especially (c)
bromodichloroethane, {d)
dibromochloroethane, (e) dibromodichloroethane, (f) tribromochloroethane, and
(g) any mixture
of two or more of the foregoing, especially a mixture that contains at least
one of (c) through
(fj, and that has an ionic bromine content of 2000 ppm or less, preferably
1500 ppm or less,
more preferably 1000 ppm or less, and most preferably S00 ppm or less. In
additional
alternative preferred embodiments such brominated styrenic polymer is also
characterized (i) by
containing, if any, less than about 700 ppm Cl, preferably less than 500 ppm
Cl, and more
preferably less than 100 ppm Cl and/or (ii) by having a TGA temperature for 1
% weight loss
which is 340°C or higher, preferably within the range of from
340°C to 380°C, and more
preferably within the range of from 345°C to 380°C, andlor (iii)
by having a thermal stability
in the Thermal Stability Test described hereinafter of 1500 ppm HBr or less,
preferably 1000
ppm of HBr or less, and more preferably 500 ppm of HBr or less, and/or (iv) by
having an
actual MW which is within about 20%, and preferably within about 10%, of its
calculated
theoretical MW, the theoretical MW being based upon the actual bromine content
of the brominated
styrenic polymer and the MW of the styrenic polymer reactant used to produce
the brominated
styrenic polymer.
In each of the above embodiments of the first aspect the brominated styrenic
polymer,
preferably a brominated polystyrene, additionally has a thermal stability in
the Thermal Stability
Test described hereinafter of 1500 ppm HBr or less, preferably 1000 ppm of HBr
or less, more
preferably 500 ppm of HBr or less, and most preferably 200 ppm of HBr or less
(e. g. , as little
as 100 ppm of HBr or less), all such ppm levels being based on the total
weight of the
brominated styrenic polymer.
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Each of the brominated polymer compositions of the first aspect of this
invention
described above preferably has a total bromine content of at least 50 wt % ,
more preferably at
least 60 wt % , and most preferably at least about 67 wt % (e. g. , in the
range of about 68-71
wt%).
A second aspect of this invention provides brominated styrenic polymers, e.g.,
brominated polystyrene, that possess both improved melt flow characteristics
and improved
thermal stability. In addition, this invention makes it possible to achieve
these beneficial
advantageous properties without material sacrifice of other important
properties. Indeed, this
aspect of the invention makes it possible to provide brominated styrenic
polymers, e.g.,
brominated polystyrene, that have other desirable properties such as low ionic
bromide content,
minimal (if any) chlorine content, and desirable color and odor properties.
Accordingly, pursuant to the second aspect of this invention there is provided
a
brominated styrenic polymer, preferably a brominated polystyrene, that has a
bromine content
in the range of 60 to 66 wt% bromine; a total chlorine content, if any, of
less than 700 ppm; a
GPC weight average molecular weight in the range of 500,000 to 800,0; a DSC
glass
transition temperature (Tg) of less than 175°C; and a thermal stability
in the Thermal Stability
Test of 250 ppm HBr or less.
In preferred embodiments, the thermal stability in the Thermal Stability Test
is 150 ppm
HBr or less, and more preferably 100 ppm or less. Preferably, the Tg is
165°C or less, and
most preferably 160°C or less. Preferably the bromine content is in the
range of 60 to 65 wt%,
and most preferably in the range of 60 to 64 wt% . Chlorine contents, if any,
are preferably 500
ppm or less, more preferably 200 ppm or less, and most preferably 100 ppm or
less. The GPC
weight average molecular weight is preferably in the range of 500,000 to
700,000.
In still other preferred embodiments of the second aspect, the brominated
styrenic
polymer, preferably brominated polystyrene, (i) has essentially no content of
impurities selected
from the group consisting of (a) methylene chloride, (b) ethylene dichloride,
and especially (c)
bromodichloroethane, (d) dibromochloroethane, (e) dibromodichloroethane, (fj
tribromochloroethane, and (g) any mixture of two or more of the foregoing,
especially a mixture
that contains at least one of (c) through (f); and/or {ii) has a solution OE
value (10 wt% in
chlorobenzene) of less than 20, preferably within the range of from 2 to 18,
and most preferably
in the range of from 2 to 15; and/or a TGA temperature for a 1 % weight loss
that is above about
315°C, and more preferably is about 325°C or above.
A third aspect of this invention provides a composition which comprises a
thermoplastic
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polymer, preferably a thermoplastic engineering thermoplastic polymer, having
blended therewith
at least a flame retardant amount of brominated styrenic polymer having, prior
to blending, (i)
a total bromine content above about 50 wt % (preferably above about 60 wt % ,
and more
preferably at least about 67 wt % ), (ii) a TGA temperature for 1 % weight
loss which is 340 ° C
or higher, preferably within the range of from 340°C to 380°C,
and more preferably within the
range of from 345°C to 380°C, and (iii) a chlorine content, if
any, of less than about 700 ppm
CI (more preferably, less than about 500 ppm Cl, and still more preferably
less than about 100
ppm Cl).
Another embodiment of the third aspect of this invention is a composition
which
comprises a thermoplastic polymer, preferably a thermoplastic engineering
thermoplastic
polymer, having blended therewith at least a flame retardant amount of
brominated styrenic
polymer having, prior to blending, (i) a total bromine content above about 50
wt% (preferably
above about 60 wt% , and more preferably at least about 67 wt%), (ii) a
chlorine content, if any,
of less than about 700 ppm Cl (preferably less than about 500 ppm Cl, and more
preferably less
than about 100 ppm Cl), and (iii) in the Hydrolyzable Bromine Test described
hereinafter, a
hydrolyzable bromine content of 3600 ppm Br or less, and preferably a
hydrolyzable bromine
content of 2800 ppm Br or less.
In another embodiment of this aspect there is provided a composition which
comprises
a thermoplastic polymer, preferably a thermoplastic engineering thermoplastic
polymer, having
blended therewith at least a flame retardant amount of brominated styrenic
polymer having, prior
to blending, (i) a total bromine content above about 50 wt % (preferably above
about 60 wt % ,
and more preferably at least about 67 wt% ), (ii) a TGA temperature for 1 %
weight loss which
is 340°C or higher, preferably within the range of from 340°C to
380°C, and more preferably
within the range of from 345°C to 380°C, and (iii) in the
Hydrolyzable Bromine Test described
hereinafter, a hydrolyzable bromine content of 3600 ppm Br or less, and
preferably a
hydrolyzable bromine content of 2800 ppm Br or less. Particularly preferred
for use in this
embodiment is a brominated styrenic polymer which is further characterized in
that it has, prior
to blending, a chlorine content, if any, of less than about 700 ppm Cl (more
preferably, less than
about 500 ppm CI, and still more preferably less than about 100 ppm Cl).
A further embodiment of the third aspect of this invention is a composition
which
comprises a thermoplastic polymer, preferably a thermoplastic engineering
thermoplastic
polymer, having blended therewith at least a flame retardant amount of
brominated styrenic
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polymer having, prior to blending, (i) a total bromine content above about 50
wt % (preferably
above about 60 wt%, and more preferably at least about 67 wt%), and (ii)
thermal stability in
the Thermal Stability Test described hereinafter of 200 ppm HBr or less,
preferably 150 ppm
of HBr or less, and more preferably 100 ppm of HBr or less. Particularly
preferred for use in
this embodiment is a brominated styrenic polymer which is further
characterized in that it has,
prior to blending, a chlorine content, if any, of less than about 700 ppm Cl
(more preferably,
less than about 500 ppm Cl, and still more preferably less than about 100 ppm
Cl).
Still another embodiment is a composition which comprises a thermoplastic
polymer,
preferably a thermoplastic engineering thermoplastic polymer, having blended
therewith at least
a flame retardant amount of brominated styrenic polymer having, prior to
blending, (i) a total
bromine content above about 50 wt % (preferably above about 60 wt % , and more
preferably at
least about 67 wt% ), (ii) a TGA temperature for 1 % weight loss which is
340°C or higher,
preferably within the range of from 340 ° C to 380 ° C, and more
preferably within the range of
from 345°C to 380°C, and (iii) thermal stability in the Thermal
Stability Test described
hereinafter of 200 ppm HBr or less, preferably 150 ppm of HBr or less, and
more preferably
100 ppm of HBr or less. Particularly preferred for use in this embodiment is a
brominated
styrenic polymer which is further characterized in that it has, prior to
blending, a chlorine
content, if any, of less than about 700 ppm Cl (more preferably, less than
about 500 ppm Cl,
and still more preferably less than about 100 ppm Cl).
A still further embodiment of the third aspect of this invention is a
composition which
comprises a thermoplastic polymer, preferably a thermoplastic engineering
thermoplastic
polymer, having blended therewith at least a flame retardant amount of
brominated styrenic
polymer having, prior to blending, (i) a total bromine content above about 50
wt% (preferably
above about 60 wt%, and more preferably at least about 67 wt%), (ii) a TGA
temperature for
1 % weight loss which is 340 ° C or higher, preferably within the range
of from 340 ° C to 380 ° C,
and more preferably within the range of from 345°C to 380°C,
(iii) in the Hydrolyzable
Bromine Test described hereinafter, a hydrolyzable bromine content of 3600 ppm
Br or less, and
preferably a hydrolyzable bromine content of 2800 ppm Br or less, and (iv)
thermal stability in
the Thermal Stability Test described hereinafter of 200 ppm HBr or less,
preferably 150 ppm
of HBr or less, and more preferably 100 ppm of HBr or less. Particularly
preferred for use in
this embodiment is a brominated styrenic polymer which is further
characterized in that it has,
prior to blending, a chlorine content, if any, of less than about 700 ppm Cl
(more preferably,
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less than about 500 ppm Cl, and still more preferably less than about 100 ppm
Cl).
Yet another embodiment is a composition which comprises a thermoplastic
polymer,
preferably a thermoplastic engineering thermoplastic polymer, having blended
therewith at least
a flame retardant amount of brominated styrenic polymer having, prior to
blending, (i) a total
bromine content of about 67 wt % or more, and (ii) a TGA temperature for 1 %
weight loss
which is 340 ° C or higher, preferably within the range of from 340
° C to 380 ° C, and more
preferably within the range of from 345°C to 380°C.
Preferably, the brominated styrenic polymer used in each of the above
compositions of
the third aspect of this invention is further characterized by:
a) containing, prior to blending, no detectable quantity of Cl; and/or
b) having, prior to blending, an actual MW which is within about 20%, and
preferably within
about 10 % , of its calculated theoretical MW, the theoretical MW being based
upon the
actual bromine content of the brominated styrenic polymer and the MW of the
styrenic
polymer reactant used to produce the brominated styrenic polymer; and/or
c) containing, prior to blending, no detectable quantity of any one or more of
bromodichloroethane, dibromochloroethane, dibromodichloroethane, and
tribromochloroethane.
d) having, prior to blending, a OE color value that is less than 20
(preferably within the
range of from 5 to 18, and most preferably within the range of from 3 to 15).
Each of the compositions of the third aspect of this invention described above
most
preferably also further comprises a reinforcing amount of reinforcing filler
or fiber, preferably
glass fiber, and/or a flame retardant synergist dispersed therein.
In each of the compositions of the third aspect of this invention described
above, most
preferably the thermoplastic polymer is a thermoplastic polyester or a
thermoplastic polyamide.
A feature of this third aspect is that it has now made it possible to provide
flame retarded
compositions that have increased thermal stabilities and reduced metal
corrosiveness at elevated
polymer processing temperatures vis-a-vis corresponding compositions made with
prior art
brominated polystyrenes. In addition it is now possible to provide flame
retarded compositions
that have other superior characteristics such as reduced odor when at elevated
temperatures, and
reduced color.
All ppm levels referred to herein are based on the total weight of the
brominated styrenic
polymer.
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Other embodiments and features of this invention will be further apparent from
the
ensuing description and appended claims.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is a schematic diagram depicting a process suitable for producing
preferred
brominated polystyrenes of each of the aspects of this invention.
THE FIRST ASPECT OF THIS INVENTION - FURTHER DESCRIPTION
Brominated StYrenic Polymers
The brominated styrenic polymers of this aspect are brominated styrenic
polymers,
(preferably a brominated polystyrene). These brominated styrenic polymers have
a total bromine
content of at least 50 wt % , preferably above 60 wt % , and more preferably
at least 67 wt % ; and
an ionic bromine content of 2000 ppm or less, preferably 1500 ppm or less,
more preferably
1000 ppm or less, and most preferably 500 ppm or less, all wt % and ppm levels
herein being
based on the total weight of the brominated styrenic polymer, unless otherwise
stated.
Moreover, the brominated styrenic polymers (preferably brominated
polystyrenes) of this
invention possess certain additional important properties or characteristics
pertaining to such
factors as TGA temperature for 1 % weight loss, total chlorine content (if
any), thermal stability
in the Thermal Stability Test described hereinafter, actual MW closely
matching calculated
theoretical MW, and freedom from specified impurity contents. The properties
of other suitable
brominated styrenic polymers of this invention will be apparent as the
description proceeds.
The high TGA temperatures which are characteristic of brominated styrenic
polymers that
possess the TGA characteristics specified above are not believed to be due to
post reaction
purification techniques. Rather, it is believed that such enhanced thermal
stability is due to the
chemical makeup of the brominated styrenic polymer itself.
As to the brominated styrenic polymers that possess the MW properties
specified above,
a difference between the actual MW and the theoretical MW outside of the
normal t margin of
error for GPC analysis, is evidence of either cross-linking (increases the MW)
or polymer chain
cleavage (decreases the MW). The 20% difference mentioned above for the
brominated styrenic
polymers that possess this characteristic includes the t margin of error.
Preferred differences
are those less than 20%, with differences of less than 10% being most
preferred. Since GPC
techniques can give different but similar values for the same polymer tested,
the testing is best
performed by taking the arithmetic average of five consecutive GPC
determinations of the
polymer to be tested. Other data averaging techniques are suitable, such as
using the average
of 10 consecutive GPC determinations with discard of the high and low values,
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requirement being that accurate and reproducible results are obtained.
This invention also provides a novel thermally stable brominated polystyrene
which is
comprised of polymer units represented by Formula (I), as follows:
x x
s
c - c
x
O
Bra
wherein each X is independently -H or a halide atom, the identity of each X
for each polymer
unit being such that the brominated polystyrene contains less than 6000 ppm of
X-type halide
atoms, and wherein the value of n for each polymer unit is such that the
brominated polystyrene
contains at least 50 wt% bromine. From an economic and performance standpoint,
it is
preferred that the bromine content be within the range of from above 60 wt% to
70-71 wt% (n
= 1.9 to 2.9-3.0), and especially within the range of from 68 wt% to 71 wt% (n
= 2.7 to 3.0).
With regard to the halide atoms, X, preferred brominated polystyrenes will be
those in
which X is bromide. Such polymers may contain some chlorine atoms, but the
amount will be
insignificant, usually less than 500 ppm, and where possible, less than 100
ppm. If chlorine is
present, its source would probably be the Lewis acid catalyst or the solvent
used in the
preparation of the brominated polystyrene. Preferred brominated polystyrene
polymers are those
in which the chlorine content is less than 500 ppm in accordance with X-Ray
Fluorescence
analysis. It is beneficial, from the viewpoint of economy and performance,
that the X-type
bromide content be less than 4000 ppm, say within the range of from 1000 ppm
to 3000 ppm.
Most beneficial are those X-type bromide contents which are within the range
of from 0 ppm to
1500 ppm.
The brominated polystyrenes of this aspect of the invention are unique in
that, from their
very inception, the polymer has the very low X-type halide content discussed
above. This is an
important aspect as the polymers do not need further treatment to reduce the X-
type halide
content. Reduction of the X-type halide content, say by hydrolysis, is not
desirable as it yields
a polymer having hydroxyl, ether, and/or olefinic functionality in its
structure which can alter
polymer properties. It is preferred that the brominated polystyrenes of this
invention contain
little or no hydrolysis residues, say less than 500 ppm and preferably less
than 100 ppm.
The most preferred brominated polystyrene components of this aspect of the
invention
will be those which provide, at the lowest cost, the highest bromine content
and the lowest X-
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type halide content which obtain the desired properties referred to above.
The brominated styrenic polymers of this aspect preferably exhibit additional
superior
physical properties, e.g., little or no color or odor. For flame retardants,
color is an important
property, with pure white being the ultimate goal. Due to the formation of
various color bodies
by all bromination processes, the industry has accepted near-white products as
being acceptable.
The color of prior art brominated polystyrene, expressed as a solution OE
value, generally will
fall within the range of 20 to 35. In distinction, the brominated polystyrenes
used pursuant to
this invention typically feature DE values ( 10 wt % in chlorobenzene) of less
than 20 and
preferably within the range of from 2 to 18. Most preferably, such DE value
will be within the
range of from 2 to 15.
Another physical property of the preferred brominated styrenic polymers of
this aspect
is that they have essentially no odor, or very little odor, when heated to a
temperature above
150°C. In comparison, Pyro-Chek~ 68PB brominated polystyrene flame
retardant (Ferro
Corporation) has a noticeable and strong odor at 150°C. The strong odor
is believed to be
attributable to the presence of bromochloroethanes, e.g., bromodichloroethane,
dibromochloro-
ethane, dibromodichloroethane and tribromochloroethane, which are in the Pyro-
Chek~ 68PB
product. Such bromochloroethanes are not seen in detectable quantities in the
brorninated
styrenic polymers of this invention.
Stvrenic Polymer Reactants
Styrenic polymers which are brominated to form the brominated styrenic
polymers of this
aspect of the invention are homopolymers and copolymers of vinyl aromatic
monomers.
Preferred vinyl aromatic monomers have the formula:
HZC=CR-Ar
wherein R is a hydrogen atom or an alkyl group having from 1 to 4 carbon atoms
and Ar is an
aromatic group (including alkyl-ring substituted aromatic groups) of from 6 to
10 carbon atoms.
Examples of such monomers are styrene, alpha-methylstyrene, ortho-
methylstyrene, meta-
methylstyrene, para-methylstyrene, para-ethylstyrene, isopropenyltoluene,
vinylnaphthalene,
isopropenylnaphthalene, vinylbiphenyl, vinylanthracene, the dimethylstyrenes,
tert-butylstyrene,
the several bromostyrenes (such as the monobromo-, dibromo-, and tribromo-
variants).
Polystyrene is the preferred reactant. When the brominated styrenic polymer is
made by
bromination of a copolymer of two or more vinyl aromatic monomers, it is
preferred that styrene
be one of the monomers and that styrene comprise at least 50 weight percent of
the
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copolymerizable vinyl aromatic monomers. If a bromo styrenic polymer is
selected for
bromination to make a brominated styrenic polymer, the initial bromostyrenic
polymer must have
a lower bromine content than the bromine content to be present in the
brominated styrenic
polymer of this invention. In this connection, the terms "brominated styrenic
polymer" and
"brominated polystyrene" as used in the specification and in the claims hereof
refer to a
brominated polymer produced by bromination of a pre-existing styrenic polymer
such as
polystyrene or a copolymer of styrene and at least one other vinyl aromatic
monomer, as
distinguished from an oligomer or polymer produced by oligomerization or
polymerization of
one or more brominated styrenic monomers, the properties of the latter
oligomers or polymers
being considerably different from brominated polystyrene in a number of
respects.
The polystyrene reactant used in the production of the brominated polystyrenes
of this
first aspect can be any of those which are commercially available. Generally,
the polystyrene
backbone will not have been hydrogenated and, thus, will have unsaturation.
There is no need
for the brominated polymers of this invention to be produced from anionically
produced
polystyrene as is taught in EPO 0 201 411; in fact, it is preferred that the
polystyrene reactant
not be an anionically produced polystyrene as such polystyrene polymers are
expensive and not
readily available. The aromatic pendant constituents of the polymer can be
alkyl substituted, but
in most cases, will not be so substituted. The polystyrene used to produce the
brominated
polystyrenes of this invention will have a MW within the range of from 500 to
500,000 and a
polydispersity within the range of from above 1 to 4. For most purposes, the
polystyrene
reactant will have a M". within the range of from 100,000 to 300,000 and will
have a
polydispersity within the range of from 1.25 to 2.5. The lower molecular
weight polystyrene
reactants will have a MW within the range of from 500 to 100,000 and a
polydispersity less than
about 10 and preferably within the range of from above 1 to 4. Higher
molecular weight
polymer reactants of this invention have a MW within the range of from 300,000
to 500,000 and
a polydispersity within the range of from above 1 to 4. The MW and
polydispersity values are
both based on gel permeation chromatography (GPC) techniques which are
hereinafter described.
It has also been found preferable that the polystyrene used in the formation
of the
brominated polystyrenes flame retardant not contain any additives, such as
zinc stearate,
paraffins, mineral oils and the like. A highly preferred polystyrene is
Styron~ 612 which is
marketed by Dow Chemical Company. However, additive-containing polystyrene
such as Styron
668, Styron 677, Styron 680 of Dow Chemical Company, as well as Piccolastic
A5, Piccolastic
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A75, or Piccolastic D125 of Hercules Incorporated, and EA 3300, MB 3200, MC
3100, or EA
3000 of Chevron Chemical Company, or equivalent materials from other
producers, can be used.
Production of the Brominated Polystyrene
For purposes of simplification, much of the description hereinafter refers to
preparation
of brominated polystyrene, the preferred flame retardant of this invention.
The principles and
procedures described are applicable to preparation of other brominated
styrenic polymers.
The brominated polystyrenes of this invention are not conventionally produced.
Generally, a suitable process comprises feeding a mixture of bromine and a
solution of
bromochloromethane and polystyrene (2.5 to 5 moles of bromine per mole of
polymerized
styrene in the polystyrene) to a reactor containing a further amount of
bromochloromethane and
a catalytic amount of AlCl3. The mixture of polystyrene, bromochloromethane
and bromine is
substantially free of a bromination catalyst. The phrase, "substantially free
of a bromination
catalyst" , is to be taken to mean less than a catalytically effective amount
of catalyst. With such
low amounts of catalyst, little or no catalyzed bromination or cross-linking
should occur.
Generally, such amounts will be less than 500 ppm based on the weight of
polystyrene reactant
present. The reaction temperature will be within the range of from -
10°C to 15°C. Preferably,
the reaction is conducted at one or more temperatures in the range of -10
° C to 10 ° C as this
provides product of the highest quality and, surprisingly, the reaction itself
proceeds at a suitably
rapid rate at these low temperatures such that the process meets commercial
production
requirements. After the reaction mass is formed, it is usually maintained at
reaction temperature
for a period in the range of 5 minutes to 2 hours, and preferably in the range
of 5 minutes to
60 minutes. After this period, the reaction product is worked up by adding
water and then
settling to remove the acidic phase. Multiple water washes can be performed as
desired. Next
the reaction mass is treated with a base such as sodium hydroxide, sodium
sulfite, and/or sodium
borohydride, usually as an aqueous solution, to adjust the reaction pH to a
suitable level of
basicity and kill any remaining brominating agent. After these treatments, the
reaction mass is
settled to obtain a two-phase reaction mass containing an organic phase, which
contains, as a
solute, the brominated styrenic polymer product and an aqueous phase. The
aqueous phase is
decanted and the remaining organic phase is stripped of its solvent component.
It is most
convenient to accomplish this strip by pumping the organic phase into boiling
water. As the
solvent is flashed off, the brominated styrenic polymer product forms a
precipitate. The
precipitate can be recovered by any liquid-solid separation technique, e. g. ,
filtration, or
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WO 00/14125 PCT/US99/20848
centrifugation. The recovered precipitate is then dried. If desired, a thermal
stabilizing amount
of base can be incorporated in the finished brominated polystyrene
composition. That is, the
finished brominated polystyrene composition can be treated to contain an
amount of alkali metal
base such that if a sample of the finished composition is dissolved in
bromochloromethane and
the resultant solution is extracted with water, the aqueous extract has a pH
of at least about 9.0,
preferably a pH in the range of 9.5 to 11, and more preferably in the range of
10 to 10.5.
Commonly-owned application Serial No. 09/066,172, filed April 24, 1998,
describes processes
in which a suitable amount of aqueous base is employed to improve the thermal
stability of the
resultant brominated polystyrene. A preferred way is to suitably increase the
amount of base
used during the catalyst deactivation stage so that a suitable residual amount
of the base remains
within the finished brominated polystyrene.
A preferred process can be used to ensure recovery of a purified brominated
polystyrene
polymer (or other brominated styrenic polymer) having a suitably low ionic
halogen content
(e. g. , ionic bromine or ionic chlorine content) from the reaction mass
formed by brominating
polystyrene with bromine in a halocarbon or halohydrocarbon solvent having a
boiling point
below 100°C and in the presence of a Lewis acid catalyst. Such
preferred process comprises:
a) quenching the reaction mass in water to form an aqueous phase and an
organic phase, and
recovering the organic phase;
b) mixing the organic phase with water at a temperature in the range of 10 to
100°C in a
ratio of from 0.02 to 0.6 part by volume of the aqueous phase per each 1 part
by volume
of organic phase to form an aqueous extraction phase and an extracted organic
phase, and
recovering the extracted organic phase;
c) optionally but preferably, mixing inorganic alkali metal base and water
with extracted
organic phase from b) to form an alkaline mixture in which the pH of the
aqueous phase
in this mixture is in the range of 7 to 14, and preferably in the range of 10
to 14;
d) mixing a bromine scavenger and water with alkaline mixture from c) to form
a bromine
scavenged mixture;
e) precipitating brominated polystyrene by mixing bromine scavenged mixture
from d) with
a water solution of inorganic alkali metal base maintained at or above the
boiling
temperature of the halocarbon or halohydrocarbon solvent; and
f) recovering brominated polystyrene formed as a precipitate in e).
Before proceeding to step c) above, step b) above can be repeated one or more
times as may be
necessary or appropriate in achieving the desired reduction in ionic halogen
(e. g. , ionic
CA 02342916 2001-03-05
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bromine). Alternatively, step b) can be conducted on a continuous basis using
liquid-liquid
extraction apparatus such as a liquid-liquid extraction tower. Sodium sulfite
and sodium
borohydride are the preferred bromine scavengers for use in step d) above.
However, other
water-soluble inorganic sulfides can be used. And in step d) above, a
coalescing filter can be
employed, if desired, to remove additional aqueous phase from the organic
phase, and thereby
still further reduce the ionic halogen content of the finished product.
In the production of brominated polystyrene, it is important that the iron
content be kept
to a minimum, say less than about 10 ppm iron. The introduction of iron into
the product
usually occurs due to iron equipment which is in contact with the reaction and
product streams.
Thus, it is preferred to use process equipment which does not act as a source
of iron
contamination. For example, the equipment can be glass-lined or corrosion
resistant alloy.
A more detailed process description with reference to the accompanying drawing
is given
below.
Detailed Descr~tion of Bromination Process with Reference to the Drawing
Preferred process technology for producing brominated polystyrenes is
described herein.
It will be appreciated that, unless otherwise indicated in the specification
hereof or specified in
any claim hereof, this invention is not limited to use of all of this
preferred process technology.
Polystyrenes useful for the production of the brominated polystyrenes by this
preferred
process are any of those which have been described above. Also, as mentioned
previously, it
is preferred that the polystyrene be additive-free.
The catalyst used in the preferred process can be any of the aluminum based
catalysts,
e.g., A1C13, AlBr3 and Al. Mixtures of aluminum catalysts can also be used.
Once the catalyst
has been added to the reaction system, it may undergo some reaction without
significant loss of
catalytic activity, e. g. , A1C13 may convert to some extent to AlBr3. A1C13,
because of its
availability and price, is the catalyst of choice, and powder grade AlCl3 is
most preferred due
to its ease of dispersibility.
The catalyst is used in an amount which is sufficient to obtain the catalytic
effect sought.
These catalytic amounts will depend on the activity of the catalyst, but will
generally fall within
the range of from 0.2 to 10 weight percent and preferably within the range of
from 0.5 to 5
weight percent, based on the weight of the styrenic polymer being brominated.
The most active
catalysts will be used in the lower amounts, while the less active catalysts
will be used in the
higher amounts. When AlCl3 is the catalyst, amounts within the range of from
0.5 to 3 weight
percent are preferred.
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The brominating agent is preferably bromine. Bromine can be obtained
commercially in
the diatomic form or can be generated by the oxidation of HBr. Br2 can be
supplied either as
a liquid or a gas. The amount of brominating agent used in the process should
provide an
overall mole ratio of total brominating agent to total styrenic polymer fed
which will provide
from 1 to 3 bromine substitutions per styrenic monomer unit in the polymer. It
is preferred that
the brominated polystyrene contain at least about 60 wt % bromine, and
desirably at least about
68 wt% bromine and most preferably within the range of from 69 to 71 wt%
bromine. For any
particular styrenic polymer, the amount of brominating agent used in the
process will be
determined by the bromine content desired considering the highest bromine
content which is
obtainable with the process parameters chosen. The higher bromine contents
will require the
most brominating agent. It is pointed out that as perbromination is
approached, it becomes more
difficult to substitute the last bromines. Adding ever larger amounts of a
brominating agent does
not always attenuate this difficulty. The stoichiometry is easily determined
as it requires one
mole of Br2 per substitution sought. In practice, the practitioner will
determine the bromine
content sought on a weight basis and then will calculate, on an idealized
basis, the number of
moles of brominating agent needed to obtain the same. For example, if the
styrenic polymer is
polystyrene and the bromine content sought is 68 wt% , at least 2.7 moles of
bromine per
styrenic monomer unit will be required, not including any desired
stoichiometric excess.
All of the bromine can be added with the polystyrene-bromochloromethane
solution or
a portion of the bromine can be pre-added to the reactor with the remainder
being added with
the solution. If pre-addition is to be used then the pre-added portion will
amount to 0.5 to 20
of the total bromine used in the process.
Generally, the mixture which is to be fed is formed from 1 to 8 moles of
brominating
agent per mole of styrenic monomer units at any time during the feed period.
During the feed,
the quantitative relationship can be constant or can vary within the above-
mentioned range. (It
is possible to allow for some excursions outside of the range so long as such
does not do
significant harm to the process efficiency or to product quality.) A preferred
range is from 2.5
to 5 moles of brominating agent per mole of styrenic monomer units to form the
feed mixture.
As can be appreciated, the use of an amount of brominating agent in the feed
mixture which
gives a mole ratio of brominating agent to styrenic monomer units which is
less than or greater
than the selected overall mole ratio of brominating agent to styrenic monomer
units will result
in exhaustion of either the brominating agent or the styrenic polymer as a
mixture constituent
before exhaustion of the other constituent. For example, to produce brominated
polystyrene with
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WO 00/14125 PCT1US99I20848
a 70 wt% bromine content, an overall molar ratio of bromine to styrenic
monomer units of 3.0:1
would be suitable. But to form a feed mixture in which the molar ratio of
bromine to styrenic
monomer units is 1:1, the amount of polystyrene to be fed will be completed
before obtaining
the needed overall amount of bromine. In this case, the practitioner first
uses the 1:1 mixture
and then continues on with just a bromine feed after the polystyrene feed has
been exhausted.
If, on the other hand, the molar ratio in the feed mixture is chosen to be
5:1, then the bromine
will first become exhausted and the feed will have to be finished with the
polystyrene alone.
Generally, it is preferred to have the overall molar ratio and the feed
mixture ratio at least
somewhat similar. In all cases though, the initial feed should preferably
contain at least a molar
ratio of bromine to styrenic monomer units of 1:1.
It is preferred that the bromine used in the process be essentially anhydrous,
i. e. , contain
less than 100 ppm (weight basis) water and contain no more than 10 ppm
impurities, e. g. , oil,
grease, carbonyl containing hydrocarbons, or iron. Available, commercial grade
bromine may
have such purity. If, however, such is not available, the organic impurities
and water content
of the bromine can be conveniently reduced by mixing together a 3 to 1 volume
ratio of bromine
and concentrated (94-98 percent) sulfuric acid. A two-phase mix is formed
which is stirred for
10-16 hours. After stirring and settling, the sulfuric acid phase, along with
the impurities and
water, is separated from the bromine phase. To further enhance the purity of
the bromine, the
recovered bromine phase can be subjected to distillation.
The preferred organic solvent for the bromination, brornochloromethane, is
preferably
essentially anhydrous, containing less than 100 ppm (weight basis) water. It
is most preferred
that the solvent contain as little water as is practically obtainable, say
between 0 to 30 ppm
(weight basis).
The process benefits from the reaction mass being in an anhydrous condition.
Water
tends to affect the catalytic activity of the aluminum catalyst, which effect
may hinder the quick
aromatic bromination of the styrene rings. If, for some reason, the
practitioner has large
amounts of water in the process and dewatering is not practical, then it may
be possible to
overcome the situation by simply increasing the amount of catalyst used.
By forming a solution of bromochloromethane and styrenic polymer, the polymer
becomes easy to handle and mix with bromine. These solutions preferably
contain from 5 to 50
wt % polymer. More highly preferred are those which contain from 5 to 30 wt %
polymer.
It is preferred to have the bromination catalyst, to which the
bromine/styrenic polymer
mixture is fed, to be in association with bromochloromethane so that the
catalyst can be in a
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solution, slurry, dispersion or suspension. Such will enhance reaction mass
mixing and mass
transfer qualities. The mixture of bromochloromethane and catalyst is best
described as a
suspension. Generally, it is suitable to use from 95 to 99.9 wt% , preferably
from 99 to 99.8
wt % , bromochloromethane, based on the total weight of bromochloromethane and
catalyst.
The styrenic polymer/brominating agent mixture feed should occur
expeditiously, with
consideration being given to the ability of the process equipment to handle
the heat load from
the exothermic process, the evolving HBr, and other process concerns. In
short, the feed can
occur over the shortest time period that will be allowed by the equipment
without excursion
outside of critical process parameters. Generally, it is anticipated that the
feed period will be
from 0.5 to 3 hours for a commercial-size plant. Shorter feed periods are
expected for smaller
scale processes.
It is possible to conduct the bromination reaction at a temperature within the
range of
from -20°C to 60°C. Desirably, the bromination temperature is
maintained within the range
of from -10 ° C to 15 ° C . Most preferred temperatures are in
the range of from -10 ° C to 0 ° C .
This last-mentioned temperature range provides product of the highest quality
and, surprisingly,
the reaction itself proceeds at a suitably rapid rate at these low
temperatures such that the process
meets commercial production requirements. The pressure can be atmospheric,
subatmospheric
or superatmospheric.
In carrying out the process, a bromination catalyst, preferably powdered
A1CI3, is
suspended in essentially anhydrous bromochloromethane, to give an easily
stirrable suspension.
The suspension is prepared in a glass-lined, stirred reactor and brought to a
temperature within
the range of from -10°C to -5°C. The mix is kept under an inert,
dry atmosphere in the
reactor. A solution of a styrenic polymer and bromochloromethane is prepared
and intimately
mixed with a bromine stream to yield a homogenous mixture. The mixture is fed
into the stirred
bromination catalyst suspension in the reactor. The intimate mixing of the
styrenic polymer
solution and bromine can be accomplished in a number of ways. For example, the
solution and
bromine can be fed to a mixing device, e. g. , a mixing nozzle, at the lower
end of the diptube
in the reactor which extends to a point below the suspension level. The mixing
device is
designed to obtain the intimate mixing of the solution and bromine. Also, the
mixing device acts
to impart mixing energy, at the point of feed, to the intimate mixture and
catalyst suspension.
Another technique for obtaining intimate mixing of the styrenic polymer
solution and brominating
agent, is to use an exterior reactor loop having an in-line mixer, such as an
impingement mixer.
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Generally, the use of an exterior reactor loop includes first charging the
reactor with a
bromination catalyst slurry, or suspension, and then withdrawing from the
reactor a stream which
is then fed to a mixer external of the reactor. A mixture formed from at least
bromine and
styrenic polymer is also fed to the mixer to yield a second mixture which is
formed from the two
feeds to the mixer. The second mixture is subsequently fed back to the
reactor. The stream
withdrawn from the reactor will initially comprise the catalyst. After the
second mixture is fed
to the reactor and the process runs, the withdrawn stream will begin to
comprise brominated
polystyrene along with catalyst.
Exemplifying the use of a reactor jet mixer, reference is made to Figure 1
wherein there
is shown a reactor, generally designated by the numeral 10. Reactor 10 is a
stirred reactor, and
initially it contains a suspension comprising catalyst and bromochloromethane.
Reactor discharge
conduit 40 provides a recycle stream from reactor 10 which is fed to pump 50.
Pump 50
pressurizes the stream so that it is fed with force via conduit 70 back to
reactor 10. Bromine
is fed via conduit 20 to pump Pl while, at the same time, a solution of
polystyrene and
bromochloromethane is fed via conduit 22 to pump PZ. Pumps Pl and PZ feed jet
mixer 24 via
lines 26 and 28, respectively, to thereby produce an intimate mixture of
bromine, polystyrene,
and solvent. This intimate mixture is fed into the reaction mass in proximity
to agitator 30 to
ensure thorough mixing of the reactor contents. The removal of contents from,
and their recycle
back to, reactor 10, and also the feed of fresh reactants to jet mixer 24 are
continued until at
least substantially all of the bromine and polystyrene/bromochloromethane
solution have been
fed into the reaction mass.
As can be appreciated, the contents of reactor 10 change in composition during
the
bromine and bromochloromethane solution feeds. Initially, the contents of
reactor 10 comprise
catalyst and solvent. As the process runs, the reactor contents comprise and
begin to become
more rich in brominated polystyrene.
Irrespective of whether or not a diptube mixer or an exterior impingement
mixer is used,
the bromination of styrenic polymer will yield HBr as a major by-product. The
HBr formed in
the process first saturates the solvent and from then on HBr escapes into the
head space above
the reactor contents. It is preferred that the HBr be removed and passed to a
water scrubber or
stored as dry HBr. A dry, inert gas, e. g. , nitrogen, can be used as a pad
over the reactor
contents to minimize the presence of water therein.
The reactor, in all cases, is preferably kept at a low temperature, e. g. ,
from -10 ° C to
CA 02342916 2001-03-05
WO 00/14125 PCT/US99/2084$
° C, during the feed of the styrenic polymer and/or brominating feed,
as the case may be, and
most preferably from -10°C to 5°C. Also, after the feed is
accomplished, the reactor is
maintained at reaction temperature (desirably in the range of -10°C to
15°C and preferably in
the range of -10°C to 10°C) for a period of from 5 minutes to 2
hours and preferably from 5
5 to 60 minutes. Such additional period of time following completion of the
feed serves to
continue the bromination until the desired degree of bromination has been
achieved. Such period
will be longer if the reaction parameters provide for mild bromination
conditions during the
bromine-polystyrene feed than if the parameters chosen provide for more severe
bromination
conditions during the feed. Also, such period will be longer if a high degree
of bromination
10 (e. g. , above 69 wt % bromine in the brominated polystyrene) is sought.
The reaction mass can
be kept in the reactor during the additional period of time following
completion of the feed.
Also, the hold period can be used to strip more HBr from the reaction mass by
using an inert
gas sweep.
When the desired degree of bromination has been achieved, the preferred
process
described above for recovery of a purified brominated polystyrene polymer
having a suitably low
ionic halogen content involving steps a) through fj can be used. Another
similar method for
working up the reaction mass is to treat the reaction mass with water to
deactivate the catalyst.
Then the reaction mass is settled to remove the aqueous HBr phase. Sodium
sulfite or sodium
borohydride, typically as an aqueous solution, can then be added (and
preferably is added) to
remove any remaining brominating agent, followed by sodium hydroxide, again
typically as an
aqueous solution, to adjust the pH of the reaction mass. Although sodium
sulfite and sodium
borohydride are the preferred bromine scavengers for use in removing any
remaining
brominating agent, other water-soluble inorganic sulfides such as lithium
sulfite, potassium
sulfite, magnesium sulfite, ammonium sulfite, or other water soluble
borohydrides such as
lithium borohydride, or potassium borohydride can be used, in as much as the
scavenging
function is performed by the sulfite or borohydride anion and/or by whatever
other species may
form when the inorganic sulfite or borohydride is dissolved in water. Aqueous
solutions of the
sulfite or borohydride can contain any suitable concentration of the dissolved
inorganic sulfite
or borohydride, and the amount of water-soluble sulfite or borohydride salt
used should be at
least sufficient to react with (destroy) the amount of residual brominating
agent present in the
mixture being treated. It is not necessary or advisable to use a large excess
of sulfite or
borohydride, e. g. , more than about 2-3 mole % excess, as the excess
represents wasted material
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WO 00/14125 PCTNS99/20848
serving no useful purpose. After scavenging the brominating agent, additional
sodium hydroxide
or other alkali metal base can be added, if desired, in a suitable amount and
preferably in the
form of an aqueous solution to act as a stabilizer for the brominated
polystyrene. Whether or
not such stabilizer is used, the reaction mass is settled to obtain a two-
phase reaction mass
containing an organic phase, which contains, as a solute, the brominated
styrenic polymer
product, and an aqueous phase. The aqueous phase is decanted and the remaining
organic phase
is stripped of its solvent component. It is most convenient to accomplish this
strip by pumping
the organic phase into boiling or near-boiling water. As the solvent is
flashed off, particles of
the brominated styrenic polymer product form in and separate from the residual
liquid phase as
a precipitate, and if desired, concurrently a suitable amount of the base can
be incorporated into
the particulate brominated polystyrene as it is being formed. If desired, a
surfactant, such as
dioctyl sulfosuccinate sodium salt, can be added to the hot water. The amount
of dioctyl
sulfosuccinate, if used, can be within the range of from 0.01 to 0.05 wt~,
based upon the total
weight of water and surfactant. The precipitate can be recovered by any liquid-
solid separation
technique, e. g. , filtration, or centrifugation. The recovered precipitate is
then dried.
Analytical Methods
Since brominated styrenic polymers have good, or at least satisfactory,
solubility in
solvents such as tetrahydrofuran (THF), the determination of the total bromine
content for the
brominated styrenic polymers is easily accomplished by using conventional X-
Ray Fluorescence
techniques. The sample analyzed is a dilute sample, say 0.1 ~ 0.05 g
brominated polystyrene
in 60 mL THF. The XRF spectrometer can be a Phillips PW 1480 Spectrometer. A
standardized
solution of bromobenzene in THF is used as the calibration standard. The total
bromine values
described herein and reported in the Examples are all based on the XRF
analytical method.
To determine the ionic bromine content of brominated styrenic polymers, the
procedure
used involves dissolving a sample of the polymer in a suitable organic solvent
medium and
titrating the solution with a standard solution of silver nitrate. In
particular, a 2.0 gram sample
of the brominated styrenic polymer weighed to the nearest 0.1 mg is placed in
a 600 mL beaker,
followed by 200 mL of tetrahydrofuran (THF), and a stir bar. The solids are
stirred until
completely dissolved. To this solution is added 50 mL of toluene, and the
mixture is stirred.
Immediately prior to conducting the titration, 50 mL of acetone, then 50 mL of
isopropyl
alcohol, and then 10 mL of glacial acetic acid are added to the sample
mixture. The sample is
then titrated immediately with standardized O.O1N AgN03 using an automatic
potentiometric
titrator such as a Metrohm 670, 716, or 736, or equivalent. Reagent grade
(A.C.S.) THF,
22
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WO 00/14125 PCTNS99/20848
toluene, acetone, isopropyl alcohol, and acetic acid are used in the
procedure. The analysis is
conducted using duplicate samples, plus a determination on a blank sample
conducted in identical
fashion except using no polymer. If both ionic bromine and ionic chlorine are
present, the
bromide titrates first. The distance between the inflection points is the
chloride titre. The
average of the two sample determinations is reported. However, if duplicate
samples do not
agree within less than 10 ~ of each other, an additional replicate sample is
analyzed in the same
way, and the average of the three analyses is reported to three significant
digits. The calculation
for ionic bromine or chlorine are as follows:
Ionic bromine (ppm) = mL AgN03, x normality of AgNO~ x (7.99)x104
sample weight in grams
Ionic chlorine (ppm) = mL AgN03 x normality of AgN03 x (3.545)x104
sample weight in grams
mL AgN03 = mL required for sample - mL required for blank
To determine the color attributes of the brominated polymers of this
invention, use is
again made of the ability to dissolve brominated styrenic polymers in easy-to-
obtain solvents,
such as chlorobenzene. The analytical method used is quite straight-forward.
Weigh 5 g t 0.1
g of the brominated polystyrene into a 50 mL centrifuge tube. To the tube also
add 45 g ~ 0.1
g chlorobenzene. Close the tube and shake for 1 hour on a wrist action shaker.
After the 1 hour
shaking period, examine the solution for undissolved solids. If a haze is
present, centrifuge the
solution for 10 minutes at 4000 rpm. If the solution is still not clear,
centrifuge an additional
10 minutes. Should the solution remain hazy, then it should be discarded as
being incapable of
accurate measurement. If, however, and this is the case most of the time, a
clear solution is
obtained, it is submitted for testing in a HunterLab ColorQuest Sphere
Spectrocolorimeter. A
transmission cell having a 20-mm transmission length is used. The colorimeter
is set to "Delta
E-lab" to report color as OE and to give color values for "L", "a" and "b".
DSC values were obtained with a TA Instruments DSC Model 2920. Samples were
heated from 25 ° C to 400 ° C at 10 ° C/min under
nitrogen.
Thermogravimetric analysis (TGA) is used to test the thermal behavior of the
brominated
styrenic polymers of this invention. The TGA values are obtained by use of a
TA Instruments
Thermogravimetric Analyzer. Each sample is heated on a Pt pan from 25°C
to 600°C at
23
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WO 00/14125 PCT/US99/20848
10°Clmin with a nitrogen flow of 50-60 mL/min.
To determine thermal stability and estimate the corrosive potential of a
sample, the
following test procedure as described in U.S. Pat. No. 5,637,650 is used. Each
sample is run
in duplicate. A 2.OOt0.01 g sample is placed into a new clean 20x150 mm test
tube. With a
neoprene stopper and Viton~ fluoroelastomer tubing, the test tube is connected
to a nitrogen
purge line with exit gas from the test tube being passed successively through
subsurface gas
dispersion frits in three 250-mL sidearm filter flasks each containing 200 mL
of 0.1 N NaOH
and 5 drops of phenolphthalein. With a constant nitrogen purge at 0.5 SCFH,
the test tube is
heated at 300°C in a molten salt bath (51.3 % KN03/48.7 % NaN03) for 15
minutes followed by
5 minutes at ambient temperature. The test tube containing the sample is then
replaced with a
clean dry test tube, and the apparatus is purged with nitrogen for an
additional 10 minutes with
the empty test tube in the 300°C salt bath. The test tube, tubing and
gas dispersion tubes are all
rinsed with deionized water, and the rinse is combined quantitatively with the
solutions in the
three collection flasks. The combined solution is acidified with 1:1 HN03 and
titrated with 0.01
N AgN03 using an automatic potentiometric titrator (Metrohm 670, 716, 736, or
equivalent).
Results are calculated as ppm HBr, ppm HCI, and ppm HBr equivalents as
follows:
pprn HBr = (EP 1)(N)(80912)/(sample wt.)
ppm HCl = {EP 2 - EP 1)(N)(36461)/(sample wt.)
ppm HBr equivalents = (EP 2)(N)(80912)/(sample wt.)
where EP(x) = mL of AgN03 used to reach end point x; and N = normality of
AgN03. The
tubing is thoroughly dried with nitrogen before the next analysis. Each day
before the first
sample, three empty clean test tubes are run as blanks to assure there is no
residual hydrogen
halide in the system.
The MW values were obtained by GPC using a Waters model 510 HPLC pump and, as
detectors, a Waters Refractive Index Detector, Model 410 and a Precision
Detector Light
Scattering Detector, Model PD2000. The columns were Waters, ~.Styragel, SOOA,
10,000A and
100,000 A. The autosampler was a Shimadzu, Model Sil 9A. A polystyrene
standard (MW =
185,000) was routinely used to verify the accuracy of the light scattering
data. The solvent used
was tetrahydrofuran, HPLC grade. The test procedure used entailed dissolving
0.015-0.020 g
of sample in 10 mL of THF. An aliquot of this solution is filtered and 50 ~,L
is injected on the
columns. The separation was analyzed using software provided by Precision
Detectors for the
PD 2000 Light Scattering Detector.
24
CA 02342916 2001-03-05
wo oonai2s rc~nvs99no8aa
The calculated theoretical MW values were obtained in accordance with the
equation:
Theoretical MW BrPS = MWPS +
~W PS)(Atom wt Br - Atom wt H)(Mol wt Sty )(0 O1)(wt% Br)
(Atom. wt. Br )(Mol. wt Sty.) - (Atom. wt. Br - Atom. wt. H)(Mol. wt.
Sty.)(0.01)(wt% Br)
As used throughout this application, "PS" is used interchangeably with and
meant to
designate polystyrene, while "Sty" means styrene. The term "MW~ means weight
average
molecular weight as determined by GPC (light scattering detector) described
supra.
Substrate Polymer Other Components. Provortions
Particular thermoplastics with which the foregoing brominated styrenic
polymers can be
blended pursuant to further embodiments of this invention include polyethylene
terephthalate,
polybutylene terephthalate, polycyclohexylene dimethylene terephthalate,
polytrimethylene
terephthalate, blends or mixtures of two or more of these, and analogous
copolymeric
thermoplastic polyesters, especially when filled or reinforced with a
reinforcing filler such as
glass fiber. Preferred thermoplastic polyesters are polyethylene terephthalate
and polybutylene
terephthalate. Polyamide thermoplastics, such as polyamide 6, polyamide 6,6,
or polyamide 12,
again preferably when glass filled, can also be effectively flame retarded in
like manner.
Conventional additives, such as flame retardant synergists, antioxidants, UV
stabilizers, dyes,
pigments, impact modifiers, fillers, acid scavengers, plasticizers, flow aids,
blowing agents, and
the like, can be included with the formulations as is appropriate. Preferred
polymer blends of
this invention do contain a flame retardant synergist or glass fiber filler or
reinforcement, and
most preferably both a synergist, and a reinforcing fiber and/or filler.
The brominated styrenic polymer flame retardants of this invention are used in
flame
retardant amounts, which typically are within the range of from 5 to 20 wt%,
the wt% being
based on the total weight of the thermoplastic polymer formulation or blend.
When used, the
amount of reinforcing fillers such as glass fiber will typically be in the
range of up to about 50
wt% based on the total weight of the finished composition. The amount of flame
retardant
synergist, when used, such as antimony trioxide, antimony pentoxide, sodium
antimonate,
potassium antimonate, iron oxide, zinc borate, or analogous synergist
generally will be in the
range of up to about 12 wt% based on the total weight of the finished
composition.
Masterbatch compositions wherein the components except for the substrate
thermoplastic
polymer are in suitable relative proportions but are blended in a smaller
amount of the substrate
polymer, are also within the scope of this invention. Thus this invention
includes compositions
CA 02342916 2001-03-05
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which comprise at least one thermoplastic polymer such as a polyalkylene
terephthalate or a
nylon polymer with which has been blended a brominated styrenic polymer
(preferably a
brominated polystyrene) of this invention in a weight ratio (substrate
polymer:brominated
polystyrene) in the range of, say, 1:99 to 70:30. Such masterbatch blends need
not, but may
also contain filler or reinforcing fiber and/or at least one flame retardant
synergist such as iron
oxide, zinc borate, or preferably an antimony oxide synergist such as antimony
trioxide,
antimony pentoxide, sodium antimonate, or potassium antimonate. Typical
examples of
reinforcing agents or fillers that can be used include low-alkali E-glass,
carbon fibers, potassium
titanate fibers, glass spheres or microballoons, whiskers, talc, wollastonite,
kaolin, chalk,
calcined kaolin, and similar substances. Sizing agents can be used with such
reinforcing agents
or fillers, if desired. A number of suitable glass-filled polyalkylene
terephthalates or nylon
molding compositions are available on the open market, and these can be used
in preparing the
compositions of this invention.
Also provided by this invention are additive blends composed of a brominated
styrenic
polymer of this invention and a synergist such as, for example, a blend of 75
parts by weight
of a brominated polystyrene and 25 parts by weight of a synergist such as
antimony trioxide,
antimony pentoxide, sodium antimonate, potassium antimonate, iron oxide, zinc
borate, or
analogous synergist. Typically such blends will contain in the range of 70 to
98 parts by weight
of the brominated polystyrene and 30 to 2 parts by weight of the synergist,
with the total of the
two components being 100 parts by weight. Suitable amounts of other suitable
additive
components can also be included in such additive blends.
Various known procedures can be used to prepare the blends or formulations
constituting
such additional compositions of this invention. For example the polyalkylene
terephthalate
polymer or a nylon polymer and the brominated styrenic polymer such as
brominated polystyrene
and any other components or ingredients to be incorporated into the finished
blend can be
blended together in powder form and thereafter molded by extrusion,
compression, or injection
molding. Likewise the components can be mixed together in a Banbury mixer, a
Brabender
mixer, a roll mill, a kneader, or other similar mixing device, and then formed
into the desired
form or configuration such as by extrusion followed by comminution into
granules or pellets,
or by other known methods.
The following Examples are presented for purposes of illustration and are not
to be
construed as imposing limitations on the scope of the invention. Examples 1-3
give preferred
general procedures for producing brominated polystyrene of this invention.
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EXAMPLE 1
A mixture of 770.0 g bromochloromethane (BCM, 9 ppm water) and 2.775 g
powdered
AlCl3 was prepared in a 5-L jacketed glass reactor equipped with a mechanical
paddle stirrer,
condenser, and thermowell. A jacketed glass mixing tee was mounted on an inlet
port on the
reactor to which bromine (533.35 g, 3.337 mole) and a solution of 134.00 g
(1.287/n mole)
polystyrene (Mitsubishi Kasei Polytex, MW = 270,000) in 1204 g BCM were pumped
at average
rates of 8.74 g/min and 20.27 g/min, respectively. The reactor and mixing tee
were cooled with
a circulating glycol bath to maintain a temperature of 0 ° C to 2
° C throughout the 1 hour feed
time and subsequent 1 hour cook. The reaction mixture was then washed with
water and
neutralized with a mixture of aqueous sodium gluconate, sodium sulfite, and
sodium hydroxide.
After diluting the organic phase with additional BCM (1450 g), the solution
was added dropwise
to 1. 8 L hot (90 ° C-94 ° C) water containing 0.25 g dioctyl
sulfosuccinate sodium salt (surfactant)
to precipitate the product and distill the solvent. The slurry was filtered
and the off white solid
was washed with water. Drying to constant weight at 150°C gave 389.8 g.
The product
contained 69.5 % total bromine and 1300 ppm hydrolyzable bromine.
EXAMPLE 2
A 7.209 g (54.1 mmol) portion of powdered aluminum chloride was suspended
(stirred
at 250 rpm) in 1549.83 g of dry (10 ppm water) bromochloromethane (BCM) in a 5-
L jacketed
reaction flask cooled to 0°C by a circulating glycol bath. A 10.00 wt%
solution of PS (360.96
g, 3.4657/n mol) in dry BCM (3250.44 g) was prepared in a second 5-L flask.
The PS used was
Dow Styrori 612 which had a MW of 190,000. The PS solution was pumped from the
bottom
valve of this feed reservoir to a jacketed, glycol-cooled mixing tee mounted
on the reaction flask.
At the same time, bromine was pumped from a fared feed reservoir to the same
mixing tee
where it combined with the polystyrene solution before dropping into the
stirred catalyst
suspension in the reaction flask. Two Masterflex 7550-90 pumps were used. The
PS feed
system used an all-Teflon feed line with pump head 77390 operating at a
constant speed of 60
rpm. This provided a constant feed rate of 21.02/n mmol PS/min (21.89 g/min).
The bromine
feed system used a combination of Teflon and Viton tubing with pump head 7518-
10 operating
at a rate of 70.05 mmol/min for the first 18 min, 38.80 mmol/min for 18-23
min, and 56.75
mmol/min for 23-165 min. Both feeds ended at 165 min. The overall mole ratio
of Br2/PS was
2.70. A rinse of 260.95 g of dry BCM was used for the PS solution feed system
to assure
complete transfer of the polymer to the reaction flask. The reaction
temperature was maintained
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WO 00/14125 PCT/US99/20848
at 0 ° C to 4 ° C throughout the addition and subsequent 2.3
hour cook period (with nitrogen purge
of the reactor overhead). The weight increase for the caustic exit gas
scrubber was 665.4 g
(87. 8 % of theory for HBr) . The catalyst was deactivated by addition of
125.0 g of a 10 wt %
aqueous solution of sodium gluconate. A 63.41 g portion of 10 wt% aqueous
sodium sulfite was
added, and the pH was adjusted to 14 by addition of 423.0 g of 10 wt % aqueous
NaOH . After
dilution with BCM (1334.6 g), the organic phase was separated and then washed
with water
(1011.8 g). The product was recovered from the organic phase by addition to
vigorously stirred
hot (90°C-94°C) water to which was added 1.23 g of the sodium
salt of dioctyl sulfosuccinate.
The solvent distilled from the hot water leaving a slurry of brominated
polystyrene product in
water. After suction filtering, the off white solid was rinsed with water and
dried to a constant
weight of 1085 . 98 g (97. 9 % yield) in a vacuum oven ( 150 ° C/2
torr/5 hr) . The ionic bromine
content of the brominated polystyrene so produced was only 88 ppm by weight.
EXAMPLE 3
The procedure of Example 2 was followed except that: a 2-L flask and 40 g of
polystyrene were used; the A1C13 wt% (based on polystyrene) was 2.0 wt% ; the
feed mole ratio
of bromine to polystyrene was 3.33; the total equivalents of bromine was 2.78;
the temperature
range was 0 ° C to 5 ° C; the feed times for the
bromine/polystyrene was 32 min/38 min; and the
cook time was 1S0 minutes.
Example 4, wherein all parts are by volume unless otherwise specified,
illustrates a
preferred purification process for removing ionic bromine from brominated
polystyrene during
the course of preparing the polymer.
EXAMPLE 4
A brominated polystyrene reaction mass (1500 parts), formed by reacting
bromine with
a 10 wt% solution of polystyrene in bromochloromethane (BCM) using aluminum
chloride as
catalyst, was quenched in 450 parts of water, and thoroughly mixed for 15
minutes. A sample
of the quenched reaction mass (Sample A) was taken for use in the purification
process described
below. The aqueous and organic phases were allowed to settle and the aqueous
phase was
removed by decantation. The organic phase was then brought to pH 12 by the
addition of 50
parts of fresh water and 25 parts of 25 wt% sodium hydroxide solution. This
mixture was
thoroughly mixed. Any residual bromine was scavenged by addition to the
mixture of 1.7 parts
of 6.9 wt% sodium borohydride in 23 wt% aqueous sodium hydroxide solution,
followed by
thorough mixing. A sample of the resultant organic phase (Sample B) was taken
for recovery
28
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WO 00/14125 PCTNS99/20848
of the brominated polystyrene without use of the following purification
process.
Application of the purification process to Sample A was performed as follows:
Sample
A was poured into a 1000 mL glass separatory funnel. The aqueous and organic
phases were
allowed to separate for 5 minutes. The organic phase was removed from the
bottom of the
funnel (325.2 grams). The aqueous layer was recovered (71.0 grams). The
organic phase was
separated into two equal halves and placed into two 8-ounce jars. Fresh water
was placed into
each jar for a second water wash (46.1 grams). This water level is equivalent
to a ratio of 850
parts of water to 1500 parts of reaction mass. Both jars were shaken for 30
minutes on a Burrell
Wrist Action Shaker. The contents of both jars were poured into and combined
in a 1000 mL
separatory funnel and allowed to separate for 5 minutes. The organic phase was
recovered from
the bottom (319.5 grams), and 95.3 grams of aqueous phase remained in the
funnel. Fresh water
(12.8 grams) was added to the organic phase to assist in pH reading using
strips of pH indicator
paper. The pH of the organic phase was 5. The pH was raised to 14 by the
addition of 25 %
by weight aqueous sodium hydroxide solution (2.4 grams). Excess bromine was
scavenged by
the addition of 6.9 wt% sodium borohydride in 23 wt% aqueous sodium hydroxide
solution (0.5
gram). The brominated styrene product from Sample A was recovered by
precipitation into a
mixture formed from 1500 grams of water and 12.6 grams of 25 % by weight
aqueous sodium
hydroxide solution. In conducting this precipitation operation, the water-
sodium hydroxide
mixture was in a 3000 mL glass reactor, with baffles, and was heated to
100°C. The vessel was
stirred by an agitator set on 500 rpm. The organic phase was fed into this
reactor by a
peristaltic pump, set on 42 rpm through 1/8" polypropylene tubing into the
water. The feed
point was approximately 1 /2" underneath the water surface. The BCM was
condensed and
removed overhead. After the organic phase was fed, the water temperature was
allowed to
return to 100°C to remove any residual BCM and then cool. The
brominated polystyrene
product was vacuum filtered in a 2000 mL fritted glass filter. It was washed
three times with
approximately 1000 mL of warm water. The solids were dried in a vacuum oven at
140°C
overnight. The ionic bromine level detected in the final brominated
polystyrene product from
Sample A was 222 ppm.
The brominated polystyrene product from Sample B, without use of the above
purification
process, was recovered by use of the foregoing precipitation procedure. The
precipitation used
1500 grams of water and 13.0 grams of 25 % by weight sodium hydroxide aqueous
solution
followed by three washings with warm water. The ionic bromine level detected
in the final
brominated polystyrene product recovered from Sample B was 1810 ppm.
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In carrying out the purification process illustrated in Example 4, effective
use can be
made of coalescing filters and/or a liquid-liquid extraction column. The
principles involved in
the design and operation of such equipment is known and reported in the
literature. Anyone
interested in pursuing such information can refer, for example, to I. Bartik,
LiquidlLiquid
Separation Through The Use of Coalescence, a paper presented on February 8,
1977 at The
Filtration Society, New England Chapter, Sturbridge, Massachusetts 01566; and
McCabe and
Smith, Unit Operations of Chemical Engineering, Third Edition, McGraw-Hill
Book Company,
pages 619-627; or other similar sources. In using a liquid-liquid extraction
tower the water
should be introduced into the column below the incoming countercurrent flow of
the crude
organic phase to the tower, so that the water extract is taken from the upper
portion of the tower
and the extracted organic phase is removed from the lower portion of the
tower.
Comparative Examples CE-1 and CE-2 describe the preparation of brominated
polystyrene in accordance with the teachings of U.S. Pat. No. 5,532,322, which
issued in 1996.
COMPARATIVE EXAMPLE CE-1
A solution of 75.10 g (0.721/n mole) of polystyrene (Mitsubishi Kasei Polytex,
MW =
270,000) in 750 g of 1,2-dichloroethane (EDC, containing 12 ppm water) was
prepared in a 5-L
jacketed glass reactor equipped with a mechanical paddle stirrer, condenser,
and thermowell.
The temperature of the reaction was controlled with an ethylene glycol
circulating bath on the
reactor jacket. After cooling to 15°C, 11.03 g of antimony (III) oxide
was added to the
polystyrene solution. A previously prepared solution of 149.7 g (0.937 mole)
bromine and 66.3
g (0.935 mole) chlorine in 505 g cold (-5 ° C) EDC was added to the
reactor under the liquid
surface through a diptube attached to the cooled bromine chloride feed
reservoir. The reaction
temperature was slowly increased from 10 ° C to 25 ° C during
the 2 hour addition. The mixture
was then held at 30 ° C until hydrogen halide evolution was complete (
1.5 hr) as indicated by an
end of the weight gain of the caustic scrubber on the exit gas line from the
reactor. The reaction
mixture was washed with water and neutralized with aqueous sodium sulfite and
caustic. The
organic phase was then added dropwise to 3.5 L methanol to precipitate the
product. The slurry
was filtered and the solid was washed with methanol. After vacuum drying at
150°C, the light
yellow solid (product 1) weighed 203.7 g.
COMPARATIVE EXAMPLE CE-2
Comparative Example CE-1 was repeated using 230.8 g (2.00 mole) commercial
bromine
chloride with 80.20 g (0.770/n mole) polystyrene and 11.77 g Sb203. The water
washed and
CA 02342916 2001-03-05
WO 00/14125 PCTNS99/20848
neutralized organic phase was divided into two equal portions. One portion was
added to 1.5
L of methanol as in Example CE-1 to obtain 101.6 g of light yellow solid
(product A) after
drying to constant weight at 150°C. The other portion was added
dropwise to 1.9 L of hot
(89 ° C-94 ° C) water to precipitate the product and distill the
solvent. The dry light yellow solid
(product B) weighed 100.3 g.
In Table 1 a compilation of the properties of the brominated polystyrene
products
produced in Examples 1-3 and CE-1 and CE-2 is given. In addition, the
properties of Pyro-Chek
68PB flame retardant of Ferro Corporation are given. Pyro-Chek 68PB flame
retardant is
believed to be produced in accordance with the teachings of U.S. 4,352,909.
TABLE
1
' ; ANAIYTICAL RESULTS
,
Example 1 2 3 CE-1 CE-2 CE-2 Pyro-Chek
A B 68PB
Total Br (wt~) 69.5 68.9 69.8 63.48 63.10 63.0067.2
Thermal Stability' 380 104 85 3250 2560 3770 1960
(ppm HBr)
Total Cl (wt%) <0.01-- <0.011.00 0.68 0.83 0.71
GPC MW (light scat.)920,000-- 620,000560,000580,000580,000620,000
Calc'd. Theo. MW 860,000590,000610,000720,000715,000715,000n/d2
GPC (light scat.)
DSC Tg3 (C) 190 -- -- 170 164 162 185
TGA 1 % wt loss 349 357 375 312 311 293 300
Q (C)
Solution Color
L 96.3296.47 96.8696.21 94.99 94.6292.03
a -2.09-2.45 -2.30-2.36 -2.32 -2.33-0.17
b 11.9914.30 11.1615.07 16.96 17.0623.38
DE 12.7214.90 11.8415.71 17.83 18.0324.70
' Determined by use of the method of U.S. Pat. No. 5,637,650 as described
above.
Calculated Theoretical MW for Pyro-Chek 68PB could not be determined since the
MW of the
polystyrene reactant used in 68PB is not known.
Tg = glass transition temperature.
Examples 5, 6, and 7 illustrate additional procedures by which brominated
polystyrenes
of this invention can be prepared.
EXAMPLE 5
A 0.910 g (6.82 mmol) portion of powdered aluminum chloride was suspended
(stirred
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CA 02342916 2001-03-05
WO 00/14125 PCT/US99/20848
at 250 rpm) in 190 g of dry (13 ppm water) bromochloromethane (BCM) in 1-L
jacketed flask
cooled to 0 ° C by circulating glycol bath. A 419. 86 g portion of a
10.00 wt % solution of
polystyrene (403.1/n mmol) in dry BCM was pumped at a constant rate of 8.46
g/min (8.13
mmol/min) to a jacketed, glycol-cooled mixing tee mounted on the reaction
flask. At the same
time, bromine was pumped at a constant rate of 6.09 g/min (38.1 mmol/min) to
the same mixing
tee where it combined with the polystyrene solution (feed mole ratio of Br2/PS
is 4.69) before
dropping into the stirred catalyst suspension in the reaction flask. The
bromine feed was stopped
after 30.0 min ( 1143 . 5 mmol) and the polystyrene solution feed was stopped
after 49.6 minutes
(overall mole ratio of Br2/PS is 2.84). A rinse of 160 g of dry BCM was used
for the
polystyrene solution feed system to assure complete transfer of the polymer to
the reaction flask.
The reaction temperature was maintained at 0 ° C-5 ° C
throughout the addition and subsequent
2 hr cook period. The catalyst was deactivated by addition of 16.4 g of 10 wt%
aqueous
solution of sodium gluconate, and pH was adjusted to 14 by addition of 60.7 g
of 10 wt
aqueous NaOH. The reaction mixture was washed with 10 wt% aqueous sodium
sulfite followed
by a water wash. The product was recovered from the organic phase by addition
to vigorously
stirred hot (90°C) water containing 0.02 wt% dioctyl sulfosuccinate
sodium salt surfactant. The
solvent is distilled from the hot water leaving a slurry of the brominated
polystyrene product in
water. After filtering, the powdery solid was rinsed with water and dried to
constant weight in
a vacuum oven (150°C/2 torr/5 hr). The dry solid weighed 127.08 g (95%
yield). The product
contained 69.6 wt% total Br. In the thermal stability test referred to above,
the product evolved
174 ppm of HBr in 15 minutes at 300°C. The HunterLab solution color (10
wt% in
chlorobenzene) values were L = 94.58, a = -2.79, b = 17.29, Delta E = 18.34.
EXAMPLE b
A Y-shaped mixing apparatus having a cooling jacket was equipped with 2 feed
lines,
each connected to a pump. One of the feed lines was for delivering bromine and
the other was
for delivering a PS and BCM solution. Bromine (93.3 g, 31.3 mL or 0.583 mole),
delivered
at a rate of 1 mL/min (19.4 mmol/min), and a PS/BCM solution (22.4 g PS, 0.215
mol and 97
mL or 194 g of anhydrous BCM), delivered at 4 mL/min (7.17 mmol/min), were fed
simultaneously from their respective feed lines into the cooled (5 ° C)
Y-mixing apparatus. The
resultant intimate mixture from the mixing apparatus was then fed into a
cooled (5 ° C) suspension
of 0.45 g (2 wt % based on PS) of powdered aluminum chloride in 49 mL (98 g)
of anhydrous
BCM. Evolved HBr was scrubbed by a caustic solution during the reaction. The
feeds were
32
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complete in 35 minutes and the mixture was cooked for 2 hours at 5°C.
After water and sodium
sulfite washes, solid BrPS was isolated by precipitating from 500 mL of hot
(90°C) water as
described above. A total of 66 g of BrPS (97 % yield) was obtained. The
product contained
68.4 wt% total Br. In the thermal stability test referred to above, the
product evolved 71 ppm
of HBr in 15 minutes at 300°C. The HunterLab solution color (10 wt% in
chlorobenzene)
values were L = 96.74, a = -1.90, b = 15.99, Delta E = 16.44.
EXAMPLE 7
A 0.910 g (6.82 mmol) portion of powdered aluminum chloride is suspended
(stirred at
250 rpm) in 190 g of dry (13 ppm water) bromochloromethane (BCM) in 1-L
jacketed flask
cooled to 0 ° C by circulating glycol bath. A 419. 86 g portion of a
10.00 wt % solution of
polystyrene (403.1/n mmol) in dry BCM is pumped at a constant rate of 8.46
g/min (8.13
mmol/min) to a jacketed, glycol-cooled mixing tee mounted on the reaction
flask. At the same
time, bromine is pumped at a constant rate of 6.09 g/min (38.1 mmol/min) to
the same mixing
tee where it is combined with the polystyrene solution (feed mole ratio of
Br2/PS is 4.69) before
dropping into the stirred catalyst suspension in the reaction flask. The
bromine feed is stopped
after 30.0 min ( 1143. 5 mmol) and the polystyrene solution feed is stopped
after 30 minutes
(overall mole ratio of Br2/PS is 2.84). A rinse of 160 g of dry BCM is used
for the polystyrene
solution feed system to assure complete transfer of the polymer to the
reaction flask. The
reaction temperature is maintained at 0 ° C-5 ° C throughout the
addition and subsequent 45 minute
cook period. The catalyst is deactivated by addition of 16.4 g of water. The
crude organic and
aqueous phases are allowed to settle, and the aqueous acidic phase is removed.
Then the pH is
adjusted to 14 by the addition of 10 wt% aqueous NaOH, and sodium borohydride
is added to
scavenge any excess bromine. The product is then recovered from the organic
phase by addition
to vigorously stirred hot (90°C) water. The solvent is distilled from
the hot water leaving a
slurry of the brominated polystyrene product in water. After filtering, the
powdery solid is
rinsed with water and dried to constant weight in a vacuum oven
(150°C/2 torr/5 hr).
Examples 8-21 illustrate additional preferred procedures for producing
brominated
polystyrenes of this invention.
EXAMPLES 8-21
The following procedure was used in these Examples: A mixture of 1.44 g (10.8
mmol)
of aluminum chloride (Aldrich, anhydrous) and 310 g of dry (10-60 ppm water
after drying over
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WO 00/14125 PCT/US99/20848
molecular sieves) bromochloromethane (BCM) was stirred at 350 rpm with a
paddle of Teflon~
polymer in a 1-L three-necked jacketed round bottom flask. The flask contents
were cooled to
the desired temperature by circulating chilled ethylene glycol through the
jacket. A 10 wt%
solution of Dow Styron 612 polystyrene (72.2 g; 0.69 equivalents) in dry BCM
(650g) was
charged to a separate vessel (500 mL graduated addition funnel). The
polystyrene solution was
pumped from the bottom of this feed reservoir to a vacuum jacketed mixing tee
mounted on the
reaction flask. The tee was maintained at the same temperature as the reaction
mixture by
circulating the ethylene glycol exiting from the flask to the tee. As the
polystyrene solution was
pumped from the reservoir, bromine (295.5 g; 1.85 mol) was simultaneously
pumped from a
125-mL graduated addition funnel to the same mixing tee where it combined with
the polystyrene
solution. The resulting red solution flowed through the jacketed, spiral
column (approximately
12" in length) and exited above the surface of the stirred catalyst
suspension. Two Masterflex
pumps were used for the feed to the mixing tee. The polystyrene system used an
all Teflon line
with a Cole-Palmer 77390 pump head. The bromine feed system used a combination
of Teflon
and Viton tubing with the latter being used with a Masterflex 7518-10 pump
head. Both feeds
ended in approximately 32-35 minutes. Constant attention to feed rates was
necessary in order
to achieve complete addition simultaneously. The overall mole ratio of Br2/PS
was 2.7. A rinse
of 57 g of dry BCM was used for the polystyrene solution feed system to assure
complete
transfer of the polymer to the reaction flask. After the addition was
complete, the reaction was
stirred at temperature for 45 minutes while being swept with nitrogen and was
then quenched
by the addition of 13 g of a 10 wt% solution of sodium sulfite. During the
quench the material
was stirred at 450 rpm and was stirred at this rate for 5 minutes. The
reaction color changed
from red/brown to a cream (light tan) during the sulfite addition. The
reaction was allowed to
stand for 5 minutes and the phases were separated using a bottom valve on the
reaction flask.
After removing the aqueous phase from the reactor, the organic layer was
returned to the reactor
and the pH was adjusted to 14 with the use of 10 wt% aqueous NaOH (100-200 g).
Additional
BCM (267 g) was added, the mixture was transferred to a separatory funnel, and
the phases were
allowed to separate. Product was recovered from the organic phase by addition
to hot water as
follows. A 2-L three-necked creased flask equipped with a mechanical stirrer,
125 rnL addition
funnel, thermometer, and Dean-Stark trap with a condenser was charged with 700
mL of water
and heated to 92-94°C with a heating mantle. The addition funnel was
filled with the contents
from the bottom phase of the separatory funnel. The feed rate from the
addition funnel was
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PCT/US99/20848
controlled so that the condenser on the Dean-Stark trap was not overloaded and
so that the water
temperature did not fall below 91 °C. BCM and some water were removed
overhead while the
product precipitated in the water as white to yellowish-white solids. The
addition funnel was
refilled as necessary to have a continuous flow of material to the flask.
After the addition was
complete, the slurry was stirred at temperature for about 10 minutes to ensure
complete removal
of BCM. The slurry was allowed to cool to about 65°C and collected on a
Buchner funnel using
suction filtration through #2 filter paper. About 300 mL of hot water was used
to rinse the flask
and the filter cake. The solids were transferred to a 2-L beaker, thoroughly
mixed with 400 mL
of water and reisolated by suction filtration. The solids were air dried
overnight and then dried
at 150°C in a vacuum oven (1-Smm Hg) until a constant weight (180-200
g) was achieved. The
product was powdered with a mortar and pestle prior to analysis (see Table 2).
TAR1,F 2
ANAI~TICAL RESULTS
Example 8 9 10 11 12 13 14
1$ Reaction Temp. -10 -10 -10 -10 0 0 0
(C)
Total Br (wt % 68.7 68.8 69.2 68.3 69.3 70.1 68.5
)
Thermal Stability'312 267 289 328 330 196 115
(ppm HBr)
Hunter Lab Solii.'
Color (1036 PhCl)
L 98.09 97.64 97.74 97.75 97.14 97.51 96.79
a -1.70 -1.83 -1.51 -1.54 -2.12 -1.59 -2.33
b 7.98 8.56 7.55 8.10 9.78 7.90 11.08
DE g.3g 9.07 8.02 8.55 10.40 8.43 11.77
TGA 1 ~ wt loss 351 353 358 353 355 356 347
TemplN2(C)
GPC molWt. (light
' _
scat. detect.)
:.:
Mw(x10') 595 601 580 631 634 572 645
Calc'd MW (x10') 591 592 600 584 602 617 587
MW/MW (Calc'd) 1.01 1.02 0.97 1.08 1.05 0.93 1.10
' Determined by use of the method of U.S. Pat. No. 5,637,650 as described
above
CA 02342916 2001-03-05
WO 00/14125 PCT/US99/20848
TABLE 2 (Continued)
:. ANALYTIC
AL
.
RE~~1LTS
Example 15 16 17 18 19 20 21
Reaction Temp. 0 10 10 10 20 20 20
(C)
Total Br (wt % 68.6 69.0 69.1 68.9 69.2 68.7 68.7
)
Thermal Stability'74 222 203 194 349 313 249
(ppm HBr)
Hunter Lab Solit.
Color (IO% PhCI)
L 97.31 96.47 96.88 96.56 94.40 94.70 94.43
a -2.32 -3.12 -2.83 -2.57 -3.18 -3.40 -3.23
b 10.10 14.63 12.98 13.09 22.79 22.17 23.92
OE 10.71 15.38 13.65 13.77 23.68 23.05 24.78
TGA 1 ~ Wt loss 351 352 347 349 342 347 344
Temp/NZ(C)
GPG mol: Wt (light
cat. detect.). ' i.: '
MW(x10') 583 673 694 819 886 863 831
Calc'd MW (x103) 589 596 598 594 600 591 591
M""lMW (Calc'd) 0.99 1.13 1.16 1.38 1.48 1.46 1.41
' Determined by use of the method of U.S. Pat. No. 5,637,650 as described
above
The ionic bromine content of the brominated polystyrene formed in Example 14
was
measured and found to be only 320 ppm by weight.
Commonly-owned application Serial No. 09/066,172, filed April 24, 1998,
describes
processes in which a suitable amount of aqueous base is employed to improve
the thermal
stability of the resultant brominated polystyrene. It is to be noted that the
use of such processes,
while desirable, is not required pursuant to this invention, as the excellent
results referred to
hereinabove were achieved without using brominated polystyrene formed in this
way. Thus the
process procedures which are fully described in this commonly-owned copending
application,
constitute optional, but entirely suitable procedures for producing brominated
polystyrenes of the
present invention.
Inclusion of the suitable amount of inorganic alkali metal base such as NaOH
or KOH
into the brominated polystyrenes of Examples 8-21 is preferably accomplished
substantially in
the manner described in Example 22, infra, by utilizing a suitable excess of
aqueous NaOH (or
36
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KOH) when precipitating the brominated polystyrene from BCM, and either
eliminating the final
water wash step or substituting an aqueous NaOH (or KOH) solution as the final
wash.
Alternatively, and less preferably, brominated polystyrenes formed as
described in Examples 8-
21 in finely-divided or powder form can be powder blended with suitable
quantities of powdered
alkali metal base such as sodium hydroxide, sodium acetate, or potassium
hydroxide.
EXAMPLE 22
The procedure of Example 1 is repeated and in the step wherein the reaction
mixture is
washed with water and neutralized with a mixture of aqueous sodium gluconate,
sodium sulfite,
and sodium hydroxide, the amount of the aqueous sodium hydroxide is such that
a dried sample
of the brominated polystyrene composition produced in the process, when
subjected to the
following pH determination procedure, gives an aqueous extract having a pH of
9.3. The
procedure for determining pH of the brominated polystyrene composition is as
follows: Place
in a beaker 1 gram to 1.5 grams of a representative sample, weighed to the
nearest 0.1 gram,
and dissolve same in 50 mL of BCM. Then add 50 mL of water which has been
boiled to
remove carbon dioxide and has a pH of 7. Vigorously stir the resultant mixture
with a magnetic
stirrer such that the two liquid phases are intimately mixed for 2 to 5
minutes. Then reduce the
stirrer speed such that the two phases separate in the beaker, and lower the
pH electrode in the
upper layer only. Measure the pH of the upper layer using a Hach EC-10 pH
meter (or
equivalent) that has been calibrated the same day.
THE SECOND ASPECT OF THIS INVENTION - FURTHER DESCRIPTION
Except as otherwise described below, the materials, facilities, operating
conditions,
analytical methods, test conditions, substrate polymers, proportions, and all
other details of the
second aspect of the invention are as described above in connection with the
first aspect of this
invention.
Brominated Styrenic Polymers
The brominated styrenic polymers of this aspect (preferably a brominated
polystyrene)
have a total bromine content in the range of 60 to 66 wt % , more preferably
from 60 to 65 wt % ,
and most preferably from 60 to 64 wt % . In addition, the brominated styrenic
polymers,
preferably brominated polystyrenes, of this invention have a specified minimal
total chlorine
content, if any; a specified GPC weight average molecular weight (MW); a
specified DSC glass
transition temperature (Tg); and a specified thermal stability in the Thermal
Stability Test, all
as set forth above in the Summary of the Invention.
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WO 00/14125 PCT/US99/20848
With reference to Formula (I) above, the identity of each X for each polymer
unit of the
polymers of the second aspect is such that the brominated polystyrene contains
substantially less
than about 5000-6000 ppm of X-type halide atoms, and wherein the value of n
for each polymer
unit is such that the brominated polystyrene contains in the range of 60 to 66
wt% bromine (n
= 1.9 to 2.5). From an economic and performance standpoint, it is preferred
that the bromine
content be within the range of from 60 wt% to 65 wt% (n = 1.9 to 2.4), and
especially within
the range of from 60 to 64 wt% (n = 1.9 to 2.3.
Preferably the brominated polystyrene polymers are those in which the chlorine
content
is less than 500 ppm and most preferably less than 100 ppm in accordance with
X-Ray
Fluorescence analysis.
The following Examples are presented for purposes of illustrating the second
aspect of
this invention, and are not to be construed as imposing limitations on the
scope of the invention.
In Examples 23 and 24 a co-feed procedure was employed whereas Examples 25-30
were
conducted using a pre-mix procedure. See in this connection U.S. Pat.
No.5,767,203.
EXAMPLE 23
Aluminum chloride (4.804 g, 36.0 mmol, 1.2 wt% based on PS) was combined with
anhydrous bromochloromethane (BCM, 1824.6 g) in a 5-L five-necked fully
jacketed reaction
flask. After cooling the stirred mixture to -2°C with a glycol
circulating bath, a 42 mL (0.815
mol) portion of bromine (Aldrich, 99.5 %) was pumped into the flask from a 500-
mL graduated
addition funnel containing a total of 1273.92 g (7.972 rnol) bromine. A
solution of 415.2 g
(3.986 mol based on styrene repeat unit) of polystyrene (Dow Styrori 612, MW =
190,000) in
3735.6 g anhydrous BCM was pumped into the vigorously stirred reaction mixture
in 192
minutes (average rate of 21.6 g/min), while at the same time, the remaining
bromine (370 mL)
in the addition funnel was pumped to the reaction flask as a separate stream
(average rate of 5.97
g/min). The reaction mixture was held between -3°C and 0°C
during the co-feed and subsequent
1 hr cook period. Water was then added to destroy the catalyst followed by 10
wt% aqueous
Na2S03 and 10 wt% aqueous NaOH. The organic phase was separated and washed
with water.
Product was recovered from the organic phase by addition to hot (88-
92°C) water which caused
the solvent to distill leaving a slurry of solid brominated polystyrene in
water. The slurry was
suction filtered. The wet cake was rinsed with water and then dried to a
constant weight in a
vacuum oven ( 150°C/2 torr) to obtain 1017.9 g (97 % yield) of white
brominated polystyrene
product.
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WO 00/14125 PC'T/US99/20848
EXAMPLE 24
The bromination of PS was repeated substantially as described in Example 23
except that
this reaction was performed in a 3-Liter reactor with appropriate adjustments
in the amounts of
materials fed into the reactor.
EXAMPLE 25
A Y-shaped glass mixing apparatus having a jacket for circulating coolant was
equipped
with two feed lines, each connected to a pump. One of the feed lines was for
delivering
bromine, and the other was for delivering a solution of PS in BCM. Bromine
(1253.2 g, 7.842
mol) and a PS/BCM solution (404.9 g Styrori 612 PS in 3604.3 g anhydrous BCM)
were
pumped simultaneously into the cooled (0°C) Y-mixing apparatus that was
mounted on a 5-L
five-necked fully jacketed reaction flask. The intimate cooled mixture of
bromine/PS/BCM that
formed in the mixer dropped into the reaction flask where it combined with a
stirred mixture of
anhydrous AlCl3 (4.91 g, 1.2 wt % based on PS) and anhydrous BCM ( 1675.0 g)
that was held
at -2°C to 0°C by a circulating cooler. Both feeds were
completed in 120 minutes for an average
feed rate of 10.44 g/min for bromine and 33.4 g/min for PS/BCM. After stirring
for 5 minutes
at 0°C, the catalyst was destroyed by addition of water. The mixture
was treated with 10 wt%
aqueous NaZS03 and neutralized with 10 wt% aqueous NaOH. The organic phase was
separated
and washed with water. The product was isolated by feeding the organic phase
to hot (88-92°C)
water to distill the solvent and form a slurry of solid brominated polystyrene
in water. After
suction filtration, the solid was rinsed with water and dried in a vacuum oven
to obtain 991.1
g (96 % yield) of white product.
EXAMPLES 26-30
In each of these Examples the general procedure of Example 25 was utilized. In
Examples 26-30
the amount of bromine used was increased from 1253.2 g (7.842 mol), to 1347.4
g (8.431 mol),
1500.2 g (9.388 mol), 1509.9 g (9.448 mol), 1653.3 g ( 10.346 mol), and 1659.6
g ( 10.385
mol), respectively. Also appropriate adjustments were made in the rate of
bromine delivery
(matching the PS/BCM delivery time in each run).
Table 3 summarizes the bromination reaction conditions used in Examples 23-30,
and
Table 4 sets forth analytical data for the respective products of Examples 23-
30.
39
CA 02342916 2001-03-05
WO 00/14125 PCT/US99/20848
O O M ,..,V1 ~D V7 ~t
~
.:
M
N ~ ~ M ~ ~ M M d' O~
W ~ d. due'ct ~ ~O O N N
O
.
p ~ ~ V1 M v0 O
~
~ O v0 O~ M M M 0 0~1
M oO V~
~ d' ~ ~G O N N
pp p ~ ~, vD Ov ~ Os
W
~ ~ M ~
M O O y D
~ ov v ~ o ~ a~ N
W ,...
C~
Z ~ ~ O ""~O N ~ I~
~
N
..i o0
O ~
G~ .., ~ ~t ~ ...,01
G
i
~ ~ O ~ ~ ~ ~ O
N O I~ M ~'~M
~ ~ N ~
eh x v ~' N ~ M 't c~io ~
Z ' o 1 ''
W .., et ~
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,~,O~ 00 N N N N ~!
a N
~ ~ ~ ~ ~ ~ O
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W ~ ~t M ~ N I~
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O .
~d.
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cV ~G ~ ~ N O~
v~ ', ~ ~t ~r M ~ ~ ~ c~io
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3
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.,
~ ~ ~ ~ ~ O '~ V b
3 ~ 3 ~ ~
H ~ ~ G
W Q a. C, A. C4 f ,
40
Image
CA 02342916 2001-03-05
PCT/US99/20848
WO 00/14125
The excellent melt stability characteristics of brominated styrenic polymers
of this
second aspect of the invention are illustrated by capillary rheometry melt
stability tests in
which the melt viscosities of a blend of glass-filled nylon 6,6 and a
brominated polystyrene
of this invention were determined and compared to the melt flow
characteristics of the same
glass-filled nylon 6,6 devoid of the brominated polystyrene. The base nylon
6,6 mixture was
composed of 70 wt% nylon 6,6 and 30 wt% glass fibers. The composition of this
invention
was made by blending 19.85 wt% of brominated polystyrene of this invention
containing
61.5 wt% of bromine. The tests were performed on a Kayeness LCR 6000 Capillary
Rheometer, operating at at 285°C at a shear rate of 500 1/sec. The die
on the capillary
rheometer had a diameter of 1 mm and a length of 20 mm. Approximately 12 grams
of
extruded pellets were forced into the heated capillary. This material was
allowed to preheat
for 6 minutes. The packing force placed on the material was 991 N. At the end
of the 6
minute preheat, the material was forced through the die form a ram starting
position of 100
mm to a ram position of 120 mm. The ram was moving at a rate of 41 mm/min.
This took
approximately 30 sec. During this time, the Viscosity of the material, the
Stress and Force
were measured. After the 6 minutes, the material was forced through the die
from a ram
position of 120 mm to 140 mm (same rate each time). Again the Viscosity,
Stress, and
Force were measured. This cycle went on for a total of five measurements,
which amounted
to 32.4 minutes in the capillary. The data points were as follows:
Glass-filled Nvlon 6 6 Formulation:
Ram Position = 120 mm, Time = 6.5 min., Viscosity = 208.8 Pa-s
Ram Position = 140 mm, Time = 13.0 min., Viscosity = 203.2 Pa-s
Ram Position = 160 mm, Time = 19.4 min. , Viscosity = 210.2 Pa-s
Ram Position = 180 mm, Time = 25.9 min., Viscosity = 207.8 Pa-s
Ram Position = 200 mm, Time = 32.4 min., Viscosity = 185.2 Pa-s
Glass filled Nvlon 6 6 Formulation Containing Brominated Polvstvrene Low Br
Sample. 62 % Br
Ram Position = 120 mm, Time = 6.5 min., Viscosity = 181.8 Pa-s
Ram Position = 140 mm, Time = 13.0 min., Viscosity = 174.1 Pa-s
Ram Position = 160 mm, Time = 19.4 min., Viscosity = 169.2 Pa-s
Ram Position = 180 mm, Time = 25.9 min., Viscosity = 153.4 Pa-s
Ram Position = 200 mm, Time = 32.4 min. , Viscosity = 151.3 Pa-s It can be
seen from
the above data that in all instances the blend of this invention containing
the brominated
42
CA 02342916 2001-03-05
WO 00/14125 PCT/US99/20848
polystyrene had lower viscosity indicating better melt flow, and equivalent
melt stability than
the same formulation devoid of the brominated polystyrene.
THE THIRD ASPECT OF THIS INVENTION - FURTHER DESCRIPTION
Except as otherwise described below, the materials, facilities, operating
conditions,
analytical methods, test conditions, proportions, and all other details of the
third aspect of
the invention are as described above in connection with the first aspect of
this invention.
Thermoplastic Polymer Components
Various thermoplastic polymers such as polyolefm polymers, styrenic polymers,
ABS,
and other similar thermoplastics can be flame retarded pursuant to this third
aspect of the
invention. Examples of polyolefm polymers that can be flame retarded include 1-
olefin
homopolymers such as polyethylene, polypropylene, polybutene, and copolymers
of ethylene
and/or propylene with one or more higher 1-olefins and/or diolefinic monomers.
Polystyrene, whether rubber modified or not, and copolymers of two or more
styrenic
monomers such as styrene, alpha-methylstyrene, vinylnaphthalene, homopolymers
of ring
alkyl-substituted vinylaromatic monomers such as individual or mixed ar-
methylstyrene
isomers, individual or mixed ar-ethylstyrene isomers, individual or mixed ar-
methyl isomers
of alpha-methylstyrene, and copolymers of two or more such vinylaromatic
monomers serve
as examples of styrenic polymers that can be flame retarded pursuant to this
aspect of the
invention.
Preferred compositions are those in which the substrate polymer being flame
retarded
is an engineering thermoplastic polymer, such as polyethylene terephthalate,
polybutylene
terephthalate, polycyclohexylene dimethylene terephthalate, nylon, and the
like, especially
when filled or reinforced with a reinforcing filler such as glass fiber.
Pursuant to the most
preferred embodiments of this invention, the engineering thermoplastic
substrate is a nylon
engineering thermoplastic (a.k.a. polyamide), such as polyamide 6, polyamide 6-
6,
polyamide 12, polyamide 4-6, and equivalent thermoplastic polyamides,
including blends of
two or more such thermoplastic polyamide resins. Suitable nylon engineering
thermoplastics
which can be used in the practice of this invention are available as articles
of commerce.
Components referred to by chemical name or formula anywhere in the
specification
or claims hereof, whether referred to in the singular or piurai, are
identified as they exist
prior to coming into contact with another substance referred to by chemical
name or chemical
type (e. g. , another component or a solvent) . It matters not what
preliminary chemical
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CA 02342916 2001-03-05
WO 00/14125 PCT/US99/20848
changes, transformations and/or reactions, if any, take place in the resulting
mixture or
solution as such changes, transformations, and/or reactions are the natural
result of bringing
the specified components together under the conditions called for pursuant to
this disclosure.
Thus the components are identified as ingredients to be brought together in
connection with
performing a desired operation or in forming a desired composition. Even
though the claims
hereinafter may refer to substances, components and/or ingredients in the
present tense
{"comprises" or "is"), the reference is to the substance, component or
ingredient as it existed
at the time just before it was first contacted, blended or mixed with one or
more other
substances, components and/or ingredients in accordance with the present
disclosure. The
fact that a substance, component or ingredient may have lost its original
identity through a
chemical reaction or transformation during the course of contacting, blending
or mixing
operations, if conducted in accordance with this disclosure and with the
application of
common sense and the ordinary skill of a chemist, is thus wholly immaterial
for an accurate
understanding and appreciation of the true meaning and substance of this
disclosure and the
claims thereof.
This invention is susceptible to considerable variation in its practice.
Therefore the
foregoing description is not intended to limit, and should not be construed as
limiting, the
invention to the particular exemplifications presented above. Rather, what is
intended to be
covered is as set forth in the ensuing claims.
44
