Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR MAKING AND USING BISARYL DIPHOSPHATES
FIELD OF THE INVENTION
The present invention relates generally to the
manufacture and use of bisaryl diphosphates, and more
particularly to an improved process for making and using
bisphenol A bis(diphenyl)-phosphate without purification.
BACKGROUND OF THE INVENTION
Bisaryl diphosphates such as bisphenol A bis(diphenyl)-
phosphate can be effective flame retardants for polymer
resins. For example, polyphenylene oxide/high-impact
polystyrene ("PPO/HIPS"~ and polycarbonate/acrylonitrile-
butediene-styrene {"PC/ABS") blends can be improved with
bisaryl diphosphate flame retardants.
Because of their commercial utility, various processes
for the manufacture of bisaryl diphosphates have been
developed. For example, it is known that bisphenol A
bis(diphenyl)-phosphate can be obtained by catalytically
reacting a phosphorus oxyhalide with bisphenol A and then
reacting the intermediate with phenol.
Prior art processes for making and using bisaryl
diphosphates include one or more steps to remove the
catalyst from the diphosphate. The most common method
employed for catalyst removal has been by aqueous washing
which leads to emulsions with the product. However, the
residual water must generally be removed prior to use as a
flame retardant.
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Prior art processes for ~tiaking and using bisaryl
diphosphates also disclose that the triaryl phosphate
content of the final products should be reduced.
Accordingly, prior art processes typically employed a
non-reactive solvent to reduce triaryl phosphates.
In view of the above it can be seen that a need exists
for improved methods of flame retarding polymer resins with
bisaryl diphosphate compounds. The present invention
addresses that need.
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SUMMARY OF THE INVENTION
Briefly describing one aspect of the present invention,
there is provided a method of effectively and economically
making flame retarded polymer resins by adding to the
polymer resin a catalytically synthesized bisaryl
diphosphate that has not been purified to remove catalyst
from the product, so that the synthesized bisaryl
diphosphate provided to the resin contains the catalyst (or
the residue of the catalyst) used to make the bisaryl
diphosphate.
In another aspect of the invention, the flame retarded
polymer resins referred to above are made using a bisaryl
diphosphate that is the product of a process in which a
dihydric aromatic compound (such as bisphenol A) is
semi-continuously added to a heated catalyst/phosphorus
oxyhalide mixture (such as a mixture of phosphorus
oxychloride and MgCl) over a period of 0.5 hours to 12.U
hours. The resulting intermediate is then reacted with an
alcohol (such as phenol) to form the desired bisaryl
diphosphate.
Other aspects of the invention provide flame retarded
polymer resins using bisaryl diphosphates prepared using
other process limitations. In one method the dihydric
aromatic compound (e. a., bisphenol A) contains less than
about 200 ppm water. In another method the alcohol (e. a.,
phenol) contains less than about 300 ppm water.
One object of the present invention is to provide
improved methods of flame retarding polymer resins.
Another object of the present invention is to provide
new polymer resins that have been flame retarded at a
" minimum cost.
Still another object of the present invention is tc
" provide improved methods of manufacturing bisaryl
diphosphate compounds for use as flame retardants in polymer
resins.
Related objects and advantages of the present invention
will be apparent from the following description.
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DESCRIPTION OF THE PREFERRED EMBODIMENT
For the purposes of promoting an understanding of tile
principles of the invention, reference will now be made to
preferred embodiments and specific language will be used to
describe the same. It will nevertheless be understood that
no limitation of the scope of the invention is thereby
intended, such alterations and further modifications in the
illustrated device, and such further applications of the
principles of the invention as illustrated therein, being
contemplated as would normally occur to one skilled in the
art to which the invention relates.
As noted above, one aspect of the present invention
provides a method of making flame retarded polymer resins by
blending a catalytically prepared bisaryl diphosphate into a
polymer resin without removing the catalyst (or catalyst
residue) from the bisaryl diphosphate. Surprisingly,
polymer resins that have been flame retarded in this w~.-,r
possess characteristics that compare favorably with those of
resins made with bisaryl diphosphates only after removing
the catalyst from the bisaryl diphosphate. While the
MgCl2 catalyst residue was expected to cause problems with
the hydrolytic stability of PC/ABS, formulated resin with
both the bisaryl diphosphate and the catalyst left in were
found to be stable.
As to the polymer resins that can be used in the present
invention, the bisaryl diphosphate/catalyst mixture may be
used as a flame retardant in a wide variety of polymer
resins. Preferred polymer resins include polyphenylene
oxide (PPO), high-impact polystyrene (HIPS), polycarbonate
(PC), polyurethane (PU), polyvinyl chloride (PVC),
acrylonitrile-butadiene-styrene (ABS), and polybutylene
terephthalate (PHT), but a wide range of other polymer
resins may also be used. Blends of these and other resins,
such as polyphenylene oxide/high-impact polystyrene blends
(ppp/HIPS) and polycarbonate/acrylonitrile-butadiene-styrene
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blends (PC/ABS) may also advantageously be made and used.
' The flame retardant may be added in the range of 5-30%,
preferably, 10-20%.
As to the bisaryl diphosphate/catalyst mixtures that are
formulated into the polymer resins, in the preferred
embodiments the bisaryl diphosphate is made by the two-step
process illustrated below.
ST 1
1. A phosphorus oxyhalide is reacted with a dihydric
aromatic compound in the presence of a catalyst. The
dihydric aromatic is preferably semi-continuously added to a
heated mixture of phosphorus oxyhalide and catalyst over a
period of time of 0.5 hours to 12 hours.
2. The reaction mixture is heated to reflux
temperatures in order to evolve the hydrogen chloride
by-product gas and convert the dihydric aromatic compound
into the corresponding diphosphorotetrachloridate.
3. Unreacted phosphorous oxyhalide is removed by
distilling under reduced pressure leaving the step 1
intermediate product.
STEP 2
1. The crude step 1 intermediate is reacted with an
alcohol to form the desired flame-retardant product.
2. The reaction is heated to sufficient temperatures
to convert the intermediate to product.
3. A subsurface nitrogen sparge is introduced to
remove the by-product hydrogen chloride.
' 4. Excess alcohol is removed, by a reduced pressure
strip if necessary. The product is used without any further
~ 30 purification.
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As to the components used in the preferred embodiments,
the phosphorus oxyhalide is of the formula POX3, where X
is bromine or chlorine. The most preferred phosphorus
oxyhalide is phosphorus oxychloride, although phosphorus
oxybromide can be used.
As to the dihydric aromatic compound used in the first
step of the process, the preferred dihydric aromatic
compounds include resorcinol, hydroquinone, bisphenol A,
bisphenol S, bisphenol F, bisphenol methane, biphenols, and
other substituted dihydric aromatic compounds. It is
preferred that there be no more than one substituent ortho
to each hydroxyl group on the dihydric aromatic compound.
The most preferred dihydric aromatic compound is bisphenol A.
The ratio of the phosphorus oxyhalide to the dihydric
compound is used to control the degree of polymerization in
the final product. The preferred range is between one-half
and five moles of phosphorus oxyhalide per mole of dihydric
compound, although ratios outside this range may be used.
The preferred range is merely representative of the process
in its preferred embodiments.
The preferred catalysts promote the reaction and are
soluble in the final product, although nonsoluble catalysts
may be used. Many of the preferred catalysts are metal
halide salts, but other types of compounds may be used ~:o
catalyze the reaction. Examples of preferred catalysts
include aluminum chloride, magnesium chloride, calcium
chloride, zinc chloride and titanium tetrachloride. The
most preferred catalyst for use in this invention is
magnesium chloride.
The amount of catalyst needed in the reaction is in the
range of 0.01-2.0 wt% based on the weight of dihydric
aromatic compound. The most preferred range is 0.1-0.75 wto.
It is to be appreciated that heat is maintained on the
reaction mixture until the dihydric aromatic compound has
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essentially been converted to the
diphosphorotetrachloridate. This typically requires aging
periods of 1-3 hours, depending on the particular dihydric
compound chosen.
After the reaction is complete, the excess phosphorus
oxyhalide may be removed by distillation. The distillation
can be at reduced pressure, or at atmospheric pressure using
elevated temperatures. Preferably, the phosphorus oxyhalide
is removed with reduced pressure and elevated temperatures.
Most preferably, the pressure is less than 20 torr and the
temperature is between 150 and 180C.
As to the alcohol used in the second step of the
process, any alcohol may be used. Preferred alcohols are
aromatic alcohols, although aliphatic alcohols may also be
used -- either alone or in combination with an aromatic
alcohol. Preferred alcohols for use in the invention
include ortho-cresol, meta-cresol, para-cresol, xylenols,
phenol, halo-phenols and other substituted phenols. It is
preferred that there be no more than one substituent ortho
to each hydroxyl group on an aromatic alcohol. The more
preferred alcohols are monohydric aromatic alcohols, most
preferably phenol.
The ratio of alcohol to the diphosphorotetrachloridate
intermediate is preferably at least 4 moles per mole based
on reaction stoichiometry. Excesses of up to 10% are
desired to increase the reaction rate and account for loss
of the aromatic compound from the reactor. The preferred
range is a 1-3% excess above stoichiometric requirements.
The alcohol is preferably added to the hot mixture from
the first step in a semi-continuous fashion. The compound
is added over the course of 0.5 to 12 hours. The reaction
is conducted at a temperature such that the alcohol reacts
' with the step 1 intermediate. This temperature varies
according to the substituents on both the alcohol and the
dihydric aromatic compound from the first step. When the
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reaction components are bisphenol A, phosphorus oxychloride,
and phenol, the preferred temperature range for the reaction
of step 1 intermediate is 140-240°C with the most preferable
range being 150-180°C. The reaction temperature may be held
constant after the addition of alcohol, or it may be
increased to increase the reaction rate.
After essentially all or the step 1 intermediate has
been converted to final product, the excess alcohol is
distilled from the mixture, preferably under reduced
pressure. The temperature, pressure and other reaction
conditions for the distillation depend on the dihydric
aromatic compound and alcohol being used, but when the
reaction components are bisphenol A and phenol, the most
preferred method is stripping in a wiped-film or
falling-film evaporator using absolute pressures of less
than 10 torr and temperatures of 165-220°C.
Alternatively, the present invention may be embodied in
a process for the preparation of a bisaryl diphosphate as
described below:
1. A phosphoryl compound of the formula (RO)2POX,
where X is bromine or chlorine and R is aromatic or
aliphatic, is reacted with about a 0.5 molar quantity of a
dihydric aromatic compound in the presence of a suitable
catalyst.
2. The reaction mixture is heated to promote reaction
and evolve the by-product hydrogen chloride gas. A nitrogen
sparge may be introduced to the reaction to enhance
evolution of hydrogen chloride.
3. The resulting product is distilled under reduced
pressure to remove any volatile components. The product is
used without any further purification.
In this alternative embodiment the aromatic/aliphatic
group in the phosphoryl compound (the "R" group in the
formula above) is derived from the reaction of an alcohol
._.....__._......... .. T
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with a phosphorus oxyhalide. Suitable alcohols are
identical to those listed above. The dihydric aromatic
compound is also selected from those listed above.
Also in the alternative embodiment the dihydric aromatic
compound is added to the hot phosphoryl compound in the
temperature range of 100-240C. Typical addition times
range from 0.5 to 12 hours. When the reaction is complete,
any volatile compounds are removed by distillation under
reduced pressure in a wiped-film or falling-film evaporator
in the temperature range of 165-220C.
In the most preferred aspect of the present invention
the bisaryl diphosphate used to flame retard the polymer
resin is the product of a specific process for catalytically
preparing bisaryl diphosphates. The process includes the
semi-continuous addition of the dihydric aromatic compound
to the phosphorus oxyhalide to reduce triaryl phosphate
content, with semi-continuous addition being the addition of
the dihydric aromatic compound to the heated
catalyst/phosphorus oxyhalide mixture over a period of J.5
hours to 12.0 hours. The resulting product is then reacted
with an alcohol to farm the desired bisaryl diphosphate.
The semi-continuous addition of the dihydric aromatic
compound reduces the decomposition of this compound,
particularly in the case of bisphenol A. The step 1
intermediate product therefore contains fewer decomposition
products. Since these decomposition products are converted
to triaryl phosphates in the second reaction, the use of the
semi-continuous addition is effective to minimize the
triaryl phosphate content in the final product. This is
especially true when bisphenol A is used as the dihydric
' aromatic compound.
In another preferred aspect of the present invention the
w bisaryl diphosphate used to flame retard the polymer resin
is the product of a process for catalytically preparing
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bisaryl diphosphates in which a dry dihydric aromatic
compound (e.a., dry BPA) is used. Most preferably, the
dihydric aromatic compound has a moisture content of <200ppm
water. Using this technique it is possible to produce a
supply of aryldiphosphate esters in which the monomer
content is increased from about 60% to about 80%. This
improves the physical properties of the formulated polymer,
including melt flow, impact strength, and flame retardancy.
In another preferred aspect of the present invention the
l0 bisaryl diphosphate used to flame retard the polymer resin
is the product of a process for catalytically preparing
bisaryl diphosphates in which a dry alcohol (e~a., dry
phenol) is used. Most preferably, the phenol has a moisture
content of <300ppm. The effect of excess water is an
I5 increase in acidity of the final product which causes
hydrolytic instability when formulated in PC/AHS. The
effect of water in phenol is thus different than the effect
of water in BPA.
In view of the above discussion of the importance of
20 keeping water out of the BPA and phenol, it should also be
recognized that it is important to also keep water out of
the POC13. It is known to the art that POC13 reacts
with water to form undesirable products, as shown below:
O
POC13 + H20 --r ~~ + HCI
CI2POH
p O O
+ POCI3 --s I, ~) + HCI
CI2POH CI2POPCI2
Acid POC13 Dimer
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Water is therefore substantially eliminated from the POC13
in the most preferred embodiments. In certain preferred
embodiments the POC13 is sufficiently water-free to assure
that the dimer and acids levels in the POC13 are less than
0.2% by weight.
Reference will now be made to specific examples using
the processes described above. It is to be understood that
the examples are provided to more completely describe
preferred embodiments, and that no limitation to the scope
of the invention is intended thereby.
EXAMPLE 1
Bulk Addition of Bispheno_1 ~A
SteQ 1: Phosphorus oxychloride (3347.88, 21.881 moles),
magnesium chloride (2.858, 0.030 moles), and bisphenol A
(1425.48, 6.24 moles) were charged into a flask equipped
with a stirrer, heating mantle, temperature controller, and
a reflux condenser vented to a caustic scrubber. The
contents were heated to reflux for 6.75 hours and the
reaction monitored for completion by liquid chromatography.
After the reaction was complete, the flask was equipped for
distillation and vacuum gradually applied until the pressure
was less than 20 torr. The temperature of the flask
contents was allowed to increase to 180°C during this
process. When the temperature reached 180°C, the
distillation was stopped and the material was subsequently
used in the second step.
Step 2: A portion of the step 1 intermediate (1095.88)
from the above reaction was charged into a flask equipped
with a stirrer, heating mantle, temperature controller, and
a reflux condenser vented to a caustic scrubber. The
' contents were heated to 180°C and phenol (832.78, 8.85
moles) was charged into an addition funnel. The phenol was
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added over the course of 3.5 hours. An hour after the
addition was complete, a subsurface nitrogen sparge was
introduced into the reactor. The reaction was monitored far
completion by liquid chromatography. When the reaction was
complete, vacuum was applied to the reactor for 1.0 hour to
remove the bulk of the excess phenol. The product was
analyzed by liquid chromatography and found to contain 96.1%
by area bisaryl diphosphate (monomer and higher oligomers)
and 4.5 wt% triphenyl phosphate.
EXAMPLE 2
Semi-Continuous Addition of Bisphenol A
Step 1: Phosphorus oxychloride (671.08, 4.38 moles) and
magnesium chloride (0.588, 0.0061 moles) were charged into a
flask equipped with a stirrer, heating mantle, temperature
controller, and a reflux condenser vented to a water
absorber. The flask contents were heated to 100°C.
Bisphenol A (288.58, 1.26 moles) was placed in a solids
addition funnel and added to the flask over the course of 3
hours. At that time, the flask contents were heated to
reflux and the reaction monitored for completion by liquid
chromatography. After the reaction was complete, the flask
was equipped for distillation and vacuum gradually applied
until the pressure was less than 20 torr. The temperature
of the flask contents was allowed to increase to 180°C
during this process. When the temperature reached 180°C,
the distillation was stopped and the material was
subsequently used in the second step.
Step 2: The contents of the flask from step 1 were
heated to 165°C. Phenol (432.68, 4.60 moles) was charged
into an addition funnel wrapped with heat tape. The phenol
was added to the reactor over the course of 2 hours. An
hour after the addition was complete, a subsurface nitrogen
sparge was introduced into the reactor. The reaction was
monitored for completion by liquid chromatography. When the
T
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reaction was complete, vacuum was applied to the evaporator
to remove the remaining phenol. The final product was
analyzed by liquid chromatography and found to contain 98.7%
by area bisaryl diphosphate (monomer and higher oligomers)
and 0.76 wt% triphenyl phosphate.
EXAMPLE 3
Use of dry BPA
Ste,.p 1: Phosphorus oxychloride and bisphenol A were reacted
under magnesium chloride catalysis as described in Example
2. Step 1 (semi-continuous addition of BPA). The bisphenol
A was analyzed for moisture prior to the reaction. Two
different reactions were run using two different water
levels in the bisphenol A. The product of both reactions
was analyzed by liquid chromatography to determine the
amount of monomeric and dimeric product. The table below
shows that use of dry bisphenol A results in a step 1
intermediate product that has a higher content of the
monomeric product relative to the dimeric product.
Water Area % Area % Normalized
in Monomeric Dimeric Area o
Bisphenol A Product Product Monomeric
Product
149 nnm 74 8 17 1 81 4
500 ppm 67 0 22 9 74 6
EXAMPLE 4
Use of Dry Phenol
Step I: Two reactions were run to generate step 1
intermediate product as described in Example 2, Step 1
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(semi-continuous addition of BPA). In both cases, bisphenol
A with a moisture content of <200 ppm water was used.
Normalized area % monomer content of the final product was
>81%.
Step 2: The material from each of the step 1 reactions was
reacted with phenol as described in Example 2, Step 2. The
two reactions used phenol which had two different levels of
moisture. The product was analyzed by liquid chromatography
for the monomeric and dimeric content and analyzed by
titration for acidity. The data in the table below show
that the increased moisture in the phenol had no impact on
the normalized monomer content in the final product.
However, the acidity of the final product was affected.
Water Normalized Area % Acid Value of Product
in Phenol Monomerir Pr~~t (mg KOH/g? _
222 ppm 81 0 0 041
400 fpm 81.0 0 248
EXAMPLE 5
It can also be seen that use of dry phenol (<300 ppm
2p water) and use of dry BPA (<200 ppm water) results in a
flame retarded polycarbonate which is hydrolytically more
stable than that achieved using wet BPA or phenol. Polymer
resin bars were compounded and molded from PC/ABS with
bisphenol A bis(diphenyl)phosphate as described in Example
6~ The formulated bars were subjected to accelerated test
conditions (100°C and 100% relative humidity) to determine
hydrolytic stability. The molecular weight of the
polycarbonate portion of the resin was monitored by gel
permeation chromatography over time. The increased
_ _......~_.____-_.._~___._....__.. _.______
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hydrolytic stability is indicated by the lower loss of
molecular weight over time.
MOLECULAR WEIGHT OF POLYCARHONATE OVER TIME
Time Dry BPA and Dry BPA Wet Phenol
(hr.) Drv Phenol Wet Phenol and Dry BPA
0 46,800 44,274 43,049
9 44,678 44,513 40,166
45,730 38,205 37,630
24 42,304 33,293 33,554
10 EXAMPLE 6
n i m in
The bisphenol A bis(diphenyl) phosphate produced in the
above examples is compounded into various polymer resins
using a Berstorff 25 mm twin screw extruder equipped with a
15 q inch wide, variable speed, DC drive belt feeder. The twin
screw extruder settings are tabulated below.
Barrel 2 Temperature (°C) 240-260
Barrel 3 Temperature (°C) 240-260
Barrel 4 Temperature (°C) 240-260
Barrel 5 Temperature (°C) 240-260
Barrel 6 Temperature (°C) 240-260
Barrel 7 Temperature (°C) 240-260
Die Temperature (°C) 240-260
Melt Temperature (°C) 240-270
Melt Pressure (psi) 240-560
Torque (kilowats) 0.17-0.25
Extruder Speed (rpm) 18-200
The bisphenol A bis(diphenyl) phosphate is heated in a
4-liter stainless steel resin kettle to approximately 80°C.
While the bisphenol A bis(diphenyl) phosphate is heating,
the belt feeder containing the polymer resin is calibrated
to deliver the required feed rate into the throat of the
extruder.
Once the bisphenol A bis(diphenyl) phosphate has reached
temperature, the heated Zenith pump is calibrated to deliver
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the desired feed rate of bisphenol A bis(diphenyl) phosphate
into the third barrel of the twin screw extruder. The
pumping system is then connected to the extruder by
attaching the feedlines into the injection port located at
the third barrel.
After the feed rates have been set, the polymer resin is
fed into the twin screw extruder at the throat. The resin
is allowed to pass through the extruder for several minutes
before the bisphenol A bis(3iprenyl) phosphate is added in
order to ensure that any residual clean out material is
purged from the extruder. After the purging step is
complete, the pumping system is started and bisphenol A
bis(diphenyl) phosphate is injected into the extruder
through the feedlines and the injection port.
The melt pressure, measured at the interface between the
seventh barrel and the die, is used as an indication that
the bisphenol A bis(diphenyl) phosphate is being
incorporated into the polymer resin. The base polymer resin
generally has a melt pressure reading 100-200 psi greater
than the bisphenol A bis(diphenyl) phosphate formulated
polymer resin. Once the bisphenol A bis(diphenyl} phosphate
is incorporated into the polymer resin, the melt pressure
drops 100-200 psi due to bisphenol A bis(diphenyl)
phosphate's ability to improve the flow properties of the
polymer resin.
Once the bisphenol A bis(diphenyl) phosphate has been
incorporated into the polymEr resin, the material passes
through the extruder die and strands through a water bath
used for cooling. The cooled strands of formulated polymer
resin are pellitized and used for molding flammability and
physical test bars.
The same procedure is used for each individual polymer
resin system. The main difference is in the amount of
bisphenol A bis(diphenyl) phosphate added to the individual
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polymer resin systems. Representative examples are below.
These formulations were all tested by the standard UL 94
procedure and found to be less flammable than the base resin.
1. PPO/HIPS: 20% bisphenol A bis(diphenyl) phosphate &
80% PPO/HIPS
2. PC/ABS: 11% bisphenol A bis(diphenyl) phospl-.ate &
89% PC/ABS
3. PBT: 10% bisphenol A bis{diphenyl) phosphate &
90% PBT.
While the invention has been illustrated and described
in detail in the foregoing description, the same is to be
construed as illustrative and not restrictive in character,
it being understood that only the preferred embodiment has
been shown and described and that all changes and
modifications that come within the spirit of the invention
are desired to be protected.
