U.S. patent application number 10/103920 was filed with the patent office on 2002-11-28 for process for producing polycarbonates.
Invention is credited to Hucks, Uwe, Kratschmer, Silke, Prein, Michael.
Application Number | 20020177684 10/103920 |
Document ID | / |
Family ID | 7679078 |
Filed Date | 2002-11-28 |
United States Patent
Application |
20020177684 |
Kind Code |
A1 |
Kratschmer, Silke ; et
al. |
November 28, 2002 |
Process for producing polycarbonates
Abstract
A continuous process for producing polycarbonates by the
transesterification of didiaryl carbonates with dihydroxyaryl
compounds in the presence of quaternary onium compounds is
disclosed. The polycarbonates thus produced are suitable for
preparing a variety of articles.
Inventors: |
Kratschmer, Silke; (Krefeld,
DE) ; Hucks, Uwe; (Alpen, DE) ; Prein,
Michael; (Brasschaat, BE) |
Correspondence
Address: |
BAYER CORPORATION
PATENT DEPARTMENT
100 BAYER ROAD
PITTSBURGH
PA
15205
US
|
Family ID: |
7679078 |
Appl. No.: |
10/103920 |
Filed: |
March 22, 2002 |
Current U.S.
Class: |
528/196 |
Current CPC
Class: |
C08G 64/307
20130101 |
Class at
Publication: |
528/196 |
International
Class: |
C08G 064/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 26, 2001 |
DE |
10114804.6 |
Claims
What is claimed is:
1. A continuous process for producing polycarbonate comprising
transesterifying didiaryl carbonate with dihydroxyaryl compound,
and condensing in the presence of a quaternary onium compound
catalyst, said condensing including a final stage, said process
characterized in the absence of additional catalyst from said final
stage.
2. A continuous process for producing polycarbonate according to
claim 1, wherein a essentially readily decomposable onium compound
is used as a catalyst and in which after a precondensation without
removing the released monohydroxyaryl compound an oligocarbonate is
formed in subsequent evaporation steps by stepwise reduction of
pressure and stepwise rise of temperature removing the released
monohydroxyaryl compound, which is then further condensed to the
final product in one or more basket-type reactors without adding
further catalysts again by evaporating the monohydroxyaryl compound
using a stepwise reduction of pressure and stepwise rise of
temperature.
3. The polycarbonate prepared by the the process according to claim
1.
4. The polycarbonate of according to claim 2, characterized in
being substantially free of electrolytes.
5. A storage medium comprising the polycarbonate of claim 2.
6. Optical storage medium comprising the polycarbonate of claim
2.
7. Magneto-optic storage medium comprising the polycarbonate of
claim 2.
8. The process of claim 1 wherein onium compound is
tetraphenylphosphonium phenolate.
9. The process of claim 1 wherein catalyst is used in an amount of
10.sup.-8 to 10.sup.-3 mol per one mol bisphenol.
10. The process of claim 9 wherein the catalyst is used in an
amount of 10.sup.-8 to 10.sup.-3 mol per one mol bisphenol.
11. The process of claim 1 wherein the catalyst is added dissolved
in phenol.
12. The process of claim 1 wherein the apparatuses, reactors,
pipelines, pumps and fittings which are used at process
temperatures of up to about 290.degree. C. are made of stainless
steels of type Cr Ni (Mo) 18/10 and the ones used at process
temperatures of higher than about 290.degree. C. are made of Ni
base alloys of type C.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a continuous process for
producing polycarbonates, more specifically to producing
polycarbonates by transesterification.
SUMMARY OF THE INVENTION
[0002] A continuous process for producing polycarbonates by the
transesterification of didiaryl carbonates with dihydroxyaryl
compounds in the presence of quaternary onium compounds, without
the addition of basic alkali- or alkaline earth metal compounds, is
disclosed. The polycarbonates thus produced are suitable for
preparing a variety of articles.
BACKGROUND OF THE INVENTION
[0003] The production of aromatic oligo- or polycarbonates by the
melt-transesterification process is known from the literature, and
has been described previously, for example, in the Encyclopedia of
Polymer Science, Vol. 10 (1969), in Chemistry and Physics of
Polycarbonates, Polymer Reviews, H. Schnell, Vol. 9, John Wiley and
Sons, Inc. (1964), and in DE-C 10 31 512.
[0004] In the aforementioned literature references and in the
literature information described therein, basic alkali, alkaline
earth and transition metal hydroxides, alcoholates, carbonates,
acetates, borohydrides, hydrogen phosphates and hydrides are used
as catalysts. These catalysts are chosen to enable the use of low
processing temperatures and short residence times for the melts
during the manufacturing process to achieve higher product
qualities. However, these catalysts have the disadvantage that they
catalyze secondary reactions which result in defects in the
polycarbonate. Defects such as these include defect structures A-D,
which are defined below in the text. In addition, the catalysts
remain in the polycarbonate and can have a negative effect on the
properties of the polymer because they contain impurities. The aim
was therefore to produce a polycarbonate which is as pure as
possible and as low colored as possible by use of an improved
process.
[0005] Therefore, in order to minimize the addition of these
catalysts, they are very often used in combination with onium
compounds, such as those described in EP-A 673959 or EP-A 694572,
for example.
[0006] EP-A 671 428 describes the production of a polycarbonate by
melt transesterification, in which tetraorganophosphonium
carboxylates which decompose during the production process are used
as catalysts. Only a discontinuous process is described. A
discontinuous process is however less susceptible to fluctuating or
inadequate catalyst concentrations. These do however occur
frequently in the case of such types of catalysts, since they
decompose uncontrollably depending on the quality of the raw
materials. The contaminations can promote or inhibit decomposition.
By contrast, in a fully continuous process, even the slightest
fluctuations in catalyst concentrations can produce changes in the
development of molecular weight during the reaction. In a
continuous process this can be compensated only very inadequately
or not at all by changing the reaction conditions in order to avoid
lapses in product quality. Since in the case of readily
decomposable catalysts such catalytic fluctuations produce the
abovementioned problems, so far no fully continuous process has
become known which is effective without the use of alkali metal or
alkaline earth metal catalysts.
[0007] Furthermore, the products described in EP-A 671 428 have an
extremely high OH terminal group concentration of more than 1000
ppm, in addition to a broad molecular weight distribution which is
manifested by the Mw/Mn ratio. It is generally known, however, that
the content of remaining terminal OH groups in particular should be
kept as low as possible, since they have a negative effect on
thermal stability and on the stability to hydrolysis, and on the
behavior of the material on aging. DE 4 238 123 A1 describes a
two-stage process for the production of polycarbonates by melt
transesterification using quaternary ammonium or phosphonium
compounds as catalysts, in which the temperatures in the first
stage are limited to 260.degree. C. and in the second stage to
295.degree. C. In the first stage adherence to end group ranges is
required. In a discontinuous process the combination of these steps
results in low contents of one type of branching agent described in
the application. A continuous method of synthesis is not
described.
[0008] DE A 43 12 390 describes a two-stage process in which also
small contents of branching agents of the same chemical structure
as disclosed in DE 4 238 123 A1 are obtained. Onium compounds are
used as catalysts in the first stage, whilst alkali or alkaline
earth salts are used in the second stage. In this way reaction
times are shortened, so as to avoid the negative impact of high
temperatures to the product quality which are well known by the
person skilled in the art. A disadvantage here is the industrial
cost, particularly the cost on an industrial scale for a uniform
distribution of the catalysts which subsequently have to be metered
into the polymer matrix in the second stage. Excess local
concentrations of catalysts cannot be ruled out, however, and can
result in a local concentration of highly branched products, which
are then contained in the polycarbonate as sources of swelling.
These swelling elements form defects in the polymer matrix and
limit the use of products made therefrom. Also this reference does
only disclose a batch process.
[0009] Moreover, the metal catalysts which are added in the process
described in DE A 4 312 390, such as alkali and alkaline earth
salts, are also disadvantageous, because they remain in the
product. They have to be deactivated as soon as the
polycondensation process has been finished by means of suitable
additives, whereby further ions are introduced. The object of the
present invention, however, is to employ polycarbonates which are
substantially free from electrolytes or which at least have a low
content of electrolytes, i.e. which are substantially free from
ions or which at least have a low content of ions, suitable for
applications in the electronics field and for storage media. In the
sense of the present invention, a low content of electrolyte means
polycarbonates which have an alkali and alkaline earth
content<60 ppb, preferably<40 ppb, most preferably<20
ppb.
[0010] Surprisingly, it has now been found that, if suitable
reactions are selected, the continues production process can result
in polymers, without catalysts which contain basic alkali or
alkaline earth metals containing compounds, and in several
subsequent steps at high temperatures and residence times,
especially at the final polycondensation step, and with economic
throughputs, without this procedure resulting in an increased
content of terminal OH groups, increased formation of branching
agents or crosslinking and loss of colour. Moreover, in contrast to
EP-A 671 428, an improved molecular weight distribution is
achieved.
[0011] When catalysis is effected by catalysts which contain alkali
or alkaline earth metals, the temperatures and the residence time
during polycondensation are lower in the final stage. It is
therefore particularly surprising that in the process according to
the invention, despite increased temperatures and residence times,
better product colors are obtained.
BRIEF DESCRIPTION OF THE FIGURES
[0012] FIG. 1 is a graphic representation of the residual content
of DPC (diphenyl carbonate) as a function of relative viscosity and
Na content.
[0013] FIG. 2 depicts yellowness index (YI) as a function of
relative viscosity, Na and temperature
[0014] FIG. 3 shows the temperature in final reactor as a function
of relative viscosity and Na content.
DETAILED DESCRIPTION OF THE INVENTION
[0015] The present invention relates to a continuous process for
producing polycarbonates by the transesterification of didiaryl
carbonates with dihydroxyaryl compounds, characterized in that
condensation is carried out in the presence of quaternary onium
compounds as catalysts, wherein the final condensation stage is
effected without further addition of catalysts.
[0016] This continuous process for producing polycarbonates by the
transesterification of didiaryl carbonates with dihydroxyaryl
compounds is preferably characterized in that, using catalysts
which can be decomposed leaving no residue, after a preliminary
condensation without separation of the monohydroxyaryl compound
formed, and in a plurality of subsequent flash/evaporator stages in
which the temperature is increased in steps and the pressure is
decreased in steps, an oligocarbonate is produced which is
thereafter condensed to form the finished polycarbonate in one or
more basket-type reactors subsequently used, without the addition
of further amounts of the spent catalyst used or of a new,
different catalyst, whilst the temperature is further increased and
the pressure is further reduced. Under the selected reaction
conditions the catalysts decompose essentially without leaving a
residue. The term "essentially without leaving a residue" is to be
understood to mean that catalyst residues, for example phosphorous
containing compounds, cannot be detected in the finished
polycarbonate, and the cleavage products are found practically
quantitatively in the condensed vapours out of the process. The
detection limit of phosphorous in polycarbonate is 1 ppm.
[0017] Over the entire process, the temperatures range between 180
and 330.degree. C., and the pressures range between 15 bar absolute
and 0.01 mbar.
[0018] In order to carry out the process, the reactants can either
be melted together, or the solid dihydroxyaryl compound can be
dissolved in the diaryl carbonate melt or the solid diaryl
carbonate can be dissolved in the dihydroxyaryl compound melt, or
both raw materials can be combined as a melt, which is preferably
obtained directly from production. The residence times of the
seperated melts of raw materials, particularly those of the
dihydroxyaryl compound melts, are selected to be as short as
possible. However the mixture of the melts could be kept for longer
residence times at lower temperatures, due to the reduced melting
point of the mixture compared to the separate raw materials without
being damaged. Thereafter, the catalyst, dissolved in the
monohydroxyaryl compound, preferably phenol, from which the diaryl
carbonate is prepared, is admixed and the melt is heated to the
reaction temperature. At the commencement of the technical
important process of producing polycarbonate from Bisphenol A and
diphenyl carbonate, the reaction temperature is 180 to 220.degree.
C., preferably 190 to 210.degree. C., particularly preferably
190.degree. C. At a residence time of 15 to 90 min., preferably 30
to 60 min., reaction equilibrium sets in, without removing the
released monohydroxyaryl compound. The reaction can be conducted at
atmospheric pressure, or can also be operated under an overpressure
for industrial reasons. The preferred pressure in industrial
installations is 2 to 12 bar.
[0019] The molten mixture is flashed into a first vacuum chamber,
the pressure in which is set to 100 to 400 mbar, preferably 150 to
300 mbar, and directly thereafter is heated to its inlet
temperature again in a suitable apparatus at the same pressure.
During this expansion process the released monohydroxyaryl compound
is removed together with remaining amounts of monomers.
[0020] After a residence time of 5 to 30 minutes in a receiver,
optionally with circulating pump device keeping temperature and
pressure constant, the reaction mixture is flashed into in a second
vacuum chamber, the pressure in which is 50 to 200 mbar, preferably
80 to 150 mbar, and directly thereafter is heated to a temperature
of 190 to 250.degree. C., preferably 210 to 240.degree. C.,
particularly preferably 210 to 230.degree. C., in an apparatus at
the same pressure. Again during this expansion process released
monohydroxyaryl compound is removed together with remaining amounts
of monomers.
[0021] After a residence time of 5 to 30 min in a receiver,
optionally with circulating pump device keeping temperature and
pressure constant, the reaction mixture is flashed into a third
vacuum chamber, the pressure in which is 30 to 150 mbar, preferably
50 to 120 mbar, and directly thereafter is heated to a temperature
of 220 to 280.degree. C., preferably 240 to 270.degree. C.,
particularly preferably 240 to 260.degree. C., in a suitable
apparatus at the same pressure. Again during this expansion process
released monohydroxyaryl compound is removed together with
remaining amounts of monomers.
[0022] After a residence time of 5 to 20 min in a receiver,
optionally with circulating pump device keeping temperature and
pressure constant, the reaction mixture is flashed into a further
vacuum chamber, the pressure in which is 5 to 100 mbar, preferably
15 to 100 mbar, particularly preferably 20 to 80 mbar, and directly
thereafter is heated to a temperature of 250 to 300.degree. C.,
preferably 260 to 290.degree. C., particularly preferably 260 to
280.degree. C., in a suitable apparatus at the same pressure. Again
during this expansion process released monohydroxyaryl compound is
removed together with remaining amounts of monomers.
[0023] The number of these stages, which is 4 here for example, can
vary between 2 and 6, preferably between 3 and 6. The relative
viscosity of the oligomer which is attained in these stages ranges
between 1.04 and 1.20, preferably between 1.04 and 1.15,
particularly preferably between 1.05 and 1.15, very particularly
preferably between 1.06 and 1.10 . The relative viscosity is
determined as the ratio of the viscosity of the solvent to the
viscosity of the polymer dissolved in said solvent. It was
determined in dichloromethane at a concentration of 5 g/liter at
5.degree. C.
[0024] After a residence time of 5 to 20 minutes in a receiver,
optionally with circulating pump device keeping temperature and
pressure constant compared to the last of the above mentioned
steps, the oligomer which is thus produced is fed into a
basket-type reactor and is further condensed at 250 to 310.degree.
C., preferably 250 to 290.degree. C., particularly preferably 250
to 280.degree. C., at pressures of 2 to 15 mbar, preferably 4 to 10
mbar, and at residence times of 30 to 90 min, preferably 30 to 60
min.
[0025] The product attains a relative viscosity of 1.12 to 1.25,
preferably 1.13 to 1.22, particularly preferably 1.13 to 1.20.
[0026] The melt leaving this reactor is brought to the desired
final viscosity in a basket-type reactor. The temperatures range
from 270 to 330.degree. C., preferably 280 to 320.degree. C,
particularly preferably 280 to 310.degree. C., the pressure ranges
from 0.01 to 3 mbar, preferably 0.2 to 2 mbar, at residence times
of 60 to 180 min, preferably 75 to 150 min. The relative
viscosities are adjusted to the values required for the application
concerned and range from 1.18 to 1.40, preferably 1.18 to 1.36,
particularly preferably 1.18 to 1.34.
[0027] Instead of two basket type reactors the whole final
polycondensation step could also be carried out in one reactor of
said type.
[0028] The vapours which come out of the different process steps
are unified and reprocessed, for example according to the process
disclosed in Geman Patent Application Serial number 1 01 00
404.
[0029] Depending on the course of the process, suitable apparatuses
and reactors for the individual process steps include heat
exchangers, apparatuses or agitated vessels which provide the
requisite residence time at constant temperature; flashing
apparatuses such as vessels of large volume, separators or
cyclones, stirred vessels, rotary evaporators or other commercially
available apparatuses; conditions which ensure the requisite
residence times after heating; single- or double-shaft basket-type
or disc reactors having the requisite volume and film forming
areas, as well as a construction which is appropriate for the
increasing melt viscosity.
[0030] The pipelines between apparatuses should of course be as
short as possible, and bends in the lines should be kept as slight
as possible. The general external conditions to be relied on when
building facilities for chemical processes have to be taken into
consideration in this respect.
[0031] In a preferred embodiment of the process, a customary heat
exchanger is used for heating the molten raw materials. A
perforated tray column is used as a hold-up vessel for achieving
reaction equilibrium. The flashing operations, i.e. the flash
evaporation operations, are carried out in centrifugal separators,
preferably cyclones or baffle separators. The melt flowing out of
the centrifugal separator, preferably cyclones or baffle separators
is heated in falling film evaporators, which are followed by
vessels for adjusting the residence time. The vessels are equipped
with a circulating pump device and the melts out of the circulating
pump device, centrifugal separators, preferably cyclones or baffle
separators flow through a lattice construction, perforated metal
sheet construction or a packed column and are collected in the
sump. Condensation to form a medium viscosity product is carried
out in a disc-type or basket-type reactor. Polycondensation is also
effected in a disc-type or basket-type reactor, which at the high
residence times provides a very large surface which is continuously
renewed under vacuum. The geometric construction of the disc-type
or basket-type reactors corresponds to the increase in melt
viscosity. It could also be possible in certain special
arrangements to use only one disc-type or basket-type reactor.
Examples of suitable reactors include those which are described in
WO A 99/28 370. Reactors made of materials which contain less than
5% iron are particularly suitable.
[0032] Particularly suitable materials for the production of the
apparatuses, reactors, pipelines, pumps and fittings are stainless
steels of type Cr Ni (Mo) 18/10, such as for example 1.4571 or
1.4541 (Stahlschlussel 2001, Verlag: Stahlschlussel Wegst GmbH,
Th-Heuss-Stra.beta.e 36, D-71672 Marbach) and Ni base alloys of
type C, such as for example 2.4605 or 2.4610 (Stahlschlussel 2001,
Verlag: Stahlschlussel Wegst GmbH, Th-Heuss-Stra.beta.e 36, D-71672
Marbach). The stainless steels are used at process temperatures of
up to about 290.degree. C. and the Ni base alloys at process
temperatures of higher than about 290.degree. C.
[0033] The present invention also relates to the thermoplastic
polycarbonates which can be obtained by the process according to
the invention. These have an extremely low content of cations and
anions, which are each less than 60 ppb, preferably <40 ppb,
most preferably <20 ppb, wherein the cations exist as those of
alkali and alkaline earth metals which can originate as impurities
from the raw materials used, for example, and from phosphonium and
ammonium salts, and which can also originate from abrasion or
corrosion of the materials of the installation employed. Further
Ion like Fe--, Ni--, Cr--, Zn--, Sn--, Mo-- and Al-ions and their
homologues could also be present in the raw materials or originate
from abrasion or corrosion of the materials of the installation
employed. In the polycarbonate according to the invention the all
over content of such impurities is below 2 ppm, preferably below 1
ppm and particularly preferably below 0.5 ppm.
[0034] Such very low contents are only achieved by using raw
materials of highest purity. Such highly pure compounds are only
obtainable by purification procedures like recrystallization,
distillation, precipitation and washing and similar procedures
known in the art, for example.
[0035] The anions which are present are those of inorganic and
organic acids in equivalent amounts (e.g. chloride, sulphate,
carbonate, phosphate, phosphite, oxalate etc.).
[0036] The polycarbonates are also distinguished by the fact that
they do not contain any detectable amounts of incorporated cleavage
or decomposition products containing reactive end groups which are
formed during the transesterification process. Such cleavage or
decomposition products are for example isopropenyl monohydroxyaryls
or dimers thereof.
[0037] The weight average molecular weights of these polycarbonates
range from 15,000 to 40,000, preferably from 18,000 to 36,000,
preferably from 18,000 to 34,000, wherein the weight average
molecular weight is determined via the relative viscosity.
[0038] The content of terminal OH groups of these polycarbonates is
50 to 750 ppm, preferably 70 to 500 ppm, most preferably 90 to 300
ppm.
[0039] The content of defect structures A-D in the polycarbonate is
determined by HPLC after complete saponification. For this purpose,
the polycarbonate is saponified by boiling it with sodium
methylate, and is subsequently acidified, filtered, and evaporated
to dryness. The residue is dissolved in acetonitrile and is
detected by HPLC.
[0040] The polycarbonate according to the invention corresponds to
formula (1) 1
[0041] wherein the part in brackets represents a repeating
structural unit, wherein M is Z or a defect structure A, B, C
and/or D,
[0042] wherein Z represents an aromatic radical which is described
below,
[0043] wherein defect structure A 2
[0044] is present in a proportion which does not exceed 800 ppm
[0045] preferably 750 ppm
[0046] most preferably 500 ppm,
[0047] wherein defect structure B 3
[0048] is present in a proportion which does not exceed 350 ppm
[0049] preferably 250 ppm
[0050] most preferably 70 ppm,
[0051] wherein defect structure C 4
[0052] is present in a proportion which does not exceed 200 ppm
[0053] preferably 150 ppm
[0054] most preferably 60 ppm,
[0055] wherein defect structure D 5
[0056] is present in a proportion which does not exceed 750 ppm
[0057] preferably 300 ppm
[0058] most preferably 150 ppm,
[0059] wherein Y denotes H or 6
[0060] wherein
[0061] R indepently from each other can denote H, or identical or
different C.sub.1-C.sub.20 alkyl, C.sub.6H.sub.5 or
C(CH.sub.3).sub.2C.sub.6H.sub.5 groups, and
[0062] n represents 0, 1 or 2,
[0063] wherein X denotes Y or --(MOCOO)Y, and
[0064] M and Y have the meanings described above.
[0065] The sum of all the defect structures A-D should not exceed
1000 ppm, preferably 700 ppm, most preferably 550 ppm.
[0066] Compared with the prior art, the process has the following
surprising advantages:
[0067] Despite decomposition of the catalyst being difficult to
control, polycarbonates which have the desired molecular weights, a
low content of terminal OH groups, a low content of crosslinking,
not detectable amounts of compounds derived from decomposition or
cleavage during the melt transesterification process and a very low
content of alkali and alkaline earth metal compounds can be
reproducibly obtained by this continuous process. Furthermore these
polycarbonates are improved by containing amounts of residual
catalyst, f. e. phosphorous containing compounds, which are below
the detection limit.
[0068] Since no alkali or alkaline earth metal cations are present
which would otherwise be present in the polycondensation stage, the
measure of deactivating the catalyst after the formation of
polycarbonate is complete, whereby further ions would be
introduced, can be omitted.
[0069] The content of diaryl carbonates in the finished
polycarbonate is appreciably less than when the polycondensation in
the last reaction step is conducted in the presence of catalysts,
for example catalysts which contain alkali or alkaline earth
metals.
[0070] Defect structures which originate from secondary reactions,
particularly branched structures of formulae A-D, are present only
in surprisingly small amounts, and in contrast to polycarbonates
otherwise obtained by the melt transesterification process, do not
result in increased melt or structural viscosities., The products
of the invention are thus equivalent to products obtained by the
solution process.
[0071] The polycarbonate which is obtained by the process according
to the invention thus differs considerably from the polycarbonates
known hitherto which have been produced by the transesterification
process, in which the catalyst is active over the entire process or
is added for subsequent polycondensation after oligocondensation
has been completed.
[0072] The attainment of a good quality product is particularly
surprising, because, compared with a procedure comprising lower
temperatures and shorter residence times, which is only possible
here in the presence of catalysts which contain alkali and/or
alkaline earth salts, it is achieved by a procedure comprising a
higher temperature and longer residence times. Under conditions
where the product is subjected to a higher degree of thermal stress
for a longer period, however, one skilled in the art would expect a
loss of quality with regard to the color of the product and the
content of defect structures. Surprisingly, these problems do not
occur when employing the process according to the invention. One
skilled in the art who starts from the prior art with the aim of
producing polycarbonates which are low in or substantially free
from electrolytes by polycondensation, namely in the last step of
the process, without a further addition of catalyst, would
therefore scarcely imagine that this could be achieved by higher
temperatures and longer residence times.
[0073] Dihydroxyaryl compounds which are suitable for the process
according to the invention are those of formula (II)
HO--Z--OH (II)
[0074] where Z is C.sub.6-30 aromatic radical which may contain one
or more aromatic nuclei, and which may be substituted and may
contain aliphatic or cycloaliphatic radicals, or alkylaryl groups
or hetero atoms as bridging members.
[0075] Examples of dihydroxyaryl compounds of formula (II)
include
[0076] hydroquinone,
[0077] resorcinol,
[0078] dihydroxydiphenyls,
[0079] bis-(hydroxyphenyl)-alkanes,
[0080] bis-(hydroxyphenyl)-cycloalkanes,
[0081] bis-(hydroxyphenyl)-sulphides,
[0082] bis-(hydroxyphenyl)-ethers,
[0083] bis-(hydroxyphenyl)-ketones,
[0084] bis-(hydroxyphenyl)-sulphones,
[0085] bis-(hydroxyphenyl)-sulphoxides,
[0086]
.alpha.,.alpha.'-bis-(hydroxyphenyl)-diisopropylbenzenes,
[0087] as well as compounds thereof which contain alkylated and
halogenated nuclei.
[0088] These and other suitable dihydroxyaryl compounds are
described, for example, in U.S. Pat. Nos. 3,028,365, 3,148,172,
3,275,601, 2,991,273, 3,271,367, 3,062,781, 2,970,131 and
2,999,846; in DE-A 1 570 703, 2 063 050, 2 063 052 and 2 211 0956;
in French Patent Specification 1 561 518; and in the monograph by
H. Schnell entitled "Chemistry and Physics of Polycarbonates",
Interscience Publishers, New York 1964 all incorporated herein by
reference.
[0089] Examples of preferred dihydroxyaryl compounds include:
[0090] 4,4'-dihydroxydiphenyl,
[0091] 2,2-bis-(4-hydroxyphenyl)propane,
[0092] 2,4-bis-(4-hydroxypheny1)-2-methylbutane,
[0093] 1,1 -bis-(4-hydroxyphenyl)cyclohexane,
[0094] 1,1 -bis-(4-hydroxyphenyl)-4-methylcyclohexane,
[0095]
.alpha.,.alpha.'-bis-(4-hydroxyphenyl)-p-diisopropylbenzene,
[0096]
.alpha.,.alpha.'-bis-(4-hydroxyphenyl)-m-diisopropylbenzene,
[0097] bis-(4-hydroxyphenyl)sulphone,
[0098] bis-(4-hydroxyphenyl)methane,
[0099] 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane,
[0100] bis-(2,6-dimethyl-4-hydroxyphenyl)propane,
[0101] bis-(4-hydroxypheny1)hexafluoropropane,
[0102] (4-hydroxyphenyl)-1-phenylethane,
[0103] (4-hydroxypheny1)diphenylmethane,
[0104] dihydroxydiphenylether,
[0105] 4,4'-thiobisphenol,
[0106] bis-(4-hydroxyphenyl)-1-(1-naphthyl)ethane,
[0107] bis-(4-hydroxyphenyl)-1-(2-naphthyl)ethane,
[0108]
dihydroxy-3-(4-hydroxyphenyl)-1,1,3-trimethyl-lH-inden-5-ol,
[0109]
dihydroxy-1-(4-hydroxyphenyl)-1,3,3-trimethyl-1H-inden-5-ol,
[0110]
2,2',3,3'-tetrahydro-3,3,3',3'-tetramethyl-1,1'-spirobi-1H-inden-5,-
5'-diol.
[0111] The following are particularly preferred:
[0112] resorcinol,
[0113] bis-(4-hydroxyphenyl)-1-(1-naphthyl)ethane,
[0114] bis-(4-hydroxyphenyl)-1-(2-naphthyl)ethane,
[0115] 2,2-bis-(4-hydroxyphenyl)propane
[0116]
.alpha.,.alpha.'-bis-(4-hydroxyphenyl)-p-diisopropylbenzene,
[0117]
.alpha.,.alpha.'-bis-(4-hydroxyphenyl)-m-diisopropylbenzene,
[0118] 1,1-bis-(4-hydroxyphenyl)cyclohexane,
[0119] bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane,
[0120] bis-(4-hydroxyphenyl)diphenylmethane.
[0121] The following are most particularly preferred:
[0122] bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane,
[0123] 4,4'-dihydroxydiphenyl,
[0124] 2,2-bis-(4-hydroxyphenyl)propane.
[0125] Either a dihydroxyaryl compound of formula (II) may be used,
with the consequential formation of homopolycarbonates, or a
plurality of dihydroxyaryl compounds of formula (II) may be used,
with the consequential formation of copolycarbonates.
[0126] Dihydroxyaryl compounds which have residual contents of the
monohydroxyaryl compounds from which they were produced may also be
used. The monohydroxyaryl compound content thereof can be up to
20%, preferably 10%, more preferably to 5% and particularly
preferably up to2%.
[0127] Didiaryl carbonates in the sense of the present invention
are diary carbonates of formula (III) 7
[0128] and of formula (IV), 8
[0129] wherein R, R' and R", independently of each other, may
represent H, or C.sub.1-C.sub.34 alkyl, cycloalkyl,
C.sub.7-C.sub.34 alkaryl or C.sub.6-C.sub.34 aryl radicals which
are optionally branched, for example diphenyl carbonate,
butylphenyl-phenyl carbonate, di-butylphenyl carbonate,
isobutylphenyl-phenyl carbonate, di-isobutylphenyl carbonate,
tert-butylphenyl-phenyl carbonate, di-tert-butylphenyl carbonate,
n-pentylphenyl-phenyl carbonate, di-(n-pentylphenyl) carbonate,
n-hexylphenyl-phenyl carbonate, di-(n-hexylphenyl) carbonate,
cyclohexylphenyl-phenyl carbonate, di-cyclohexylphenyl carbonate,
phenylphenol-phenyl carbonate, di-phenylphenol carbonate,
isooctylphenyl-phenyl carbonate, di-isooctylphenyl carbonate,
n-nonylphenyl-phenyl carbonate, di-(n-nonylphenyl) carbonate,
cumylphenyl-phenyl carbonate, di-cumylphenyl carbonate,
naphthylphenyl-phenyl carbonate, di-naphthylphenyl carbonate,
di-tert-butyl phenyl-phenyl carbonate, di-i-tert-butylphenyl
carbonate, dicumylphenyl-phenyl carbonate, di-(dicumylphenyl)
carbonate, 4-phenoxyphenyl-phenyl carbonate, di-4-phenoxyphenyl
carbonate, 3-pentadecylphenyl-phenyl carbonate,
di-(3-pentadecylphenyl)carbonate, tritylphenyl-phenyl carbonate,
di-tritylphenyl carbonate, preferablydiphenyl carbonate,
tert-butylphenyl-phenyl carbonate, di-tert-butyl phenyl carbonate,
phenylphenol-phenyl carbonate, di-phenylphenol carbonate,
cumylphenyl-phenyl carbonate, di-cumylphenyl carbonate, most
preferably diphenyl carbonate.
[0130] The diaryl carbonates could also be used containing residual
amounts of the monohydroxyaryl compound, which was used as the raw
material for its manufacturing. These amounts could be up to 20% by
weight of the diaryl carbonate, preferably up to 10% by weight,
particularly preferably up to 5% by weight and very particularly
preferably up to 2% by weight.
[0131] Furthermore, the phenolic compounds used as carbonates may
also be used directly as monohydroxyaryl compounds in addition to
the aforementioned carbonates, in order to influence the terminal
groups of the polycarbonate. For this purpose such a
monohydroxyaryl compound must be selected which posseses a boiling
point above the boiling point of the monohydroxyaryl compound used
as the precursor for the diaryl carbonate used in the process. The
preferred mixtures are those which contain diphenyl carbonate. In
the process according to the invention, it is possible to add the
monohydroxyaryl compound at any time during the reaction,
preferably at the start of the reaction, and the amount added may
be divided into a plurality of portions. The proportion of free
monohydroxyaryl compound may range from 0.4-17 mol %, preferably
1.3-8.6 mol % (with respect to the dihydroxyaryl compound). The
addition may be made either before the reaction, or completely or
in part during the reaction.
[0132] The diaryl carbonates are used in an amount of 1.02 to 1.30
mol, preferably 1.04 to 1.26 mol, most preferably 1.06-1.22 mol,
with respect to one mole of dihydroxyaryl compound. Mixtures of the
aforementioned diaryl carbonates may also be used.
[0133] Ammonium or phosphonium catalysts are used for the
synthesis. For the purpose of the present application, these are
also jointly designated as onium compounds. They are preferably
used in amounts of 10.sup.-8 to 10.sup.-3 mol, most preferably in
amounts of 10.sup.-7 to 10.sup.-4 mol, with respect to one mol
dihydroxyaryl compound.
[0134] Phosphonium salts may be used as catalysts for the
production of the polycarbonates according to the invention, and
may optionally be used in combination with other suitable catalysts
which do not result in too high a content of defect structures A-D
and which decompose at elevated temperatures, such as other onium
compounds for example.
[0135] Phosphonium salts in the sense of the invention are those of
formula (VII), 9
[0136] wherein R.sup.1-4 can represent identical or different
C.sub.1-C.sub.10 alkyl, C.sub.6-C.sub.10 aryl, C.sub.7-C.sub.10
arylalkyl or C.sub.5-C.sub.6 cycloalkyl groups, preferably methyl
or C.sub.6-C.sub.14 aryl groups, most preferably methyl or phenyl,
and X.sup.- can be an anion such as hydroxide, sulphate, hydrogen
sulphate, hydrogen carbonate, carbonate, a halide, preferably
chloride, or an alcoholate of formula OR, wherein R is preferably a
C.sub.6-C.sub.14 aryl or a C.sub.7-C.sub.12 arylalkyl group, most
preferably phenyl. Compounds such as these are described in
"Houben-Weyl, Methoden der organischen Chemie", Thieme Verlag
Stuttgart, 4th Edition, 1963, Vol. 12.1, pages 47, 107-147, as
thermally labile phosphonium salts. The preferred catalysts
are:
[0137] tetraphenylphosphonium chloride,
[0138] tetraphenylphosphonium hydroxide,
[0139] tetraphenylphosphonium phenolate,
[0140] most preferably tetraphenylphosphonium phenolate.
[0141] Preferred amounts of phosphoniumcatalysts are 10.sup.-8 to
10.sup.-3 per mol of dihydroxyaryl compound, particularly preferred
are amounts of 10.sup.-7 to 10.sup.-4.
[0142] The catalysts are added in solution in order to avoid
damaging excess concentrations during metering. The solvents are
system- and process-inherent compounds such as for example
dihydroxyaryl compounds, diaryl carbonates or monohydroxyaryl
compounds. Monohydroxyaryl compounds are particularly preferred
since the skilled man knows that the dihydroxyaryl compounds and
diaryl carbonates already change slightly and decompose at even
slightly raised temperatures, in particular under the effect of the
catalysts. The resulting compounds reduce the quality of the
polycarbonate. In the technically important transesterification
process for the production of polycarbonate the preferred compound
is phenol. Phenol is also an obvious choice since the selected
catalyst tetraphenylphosphonium phenate is isolated as a mixed
crystal with phenol during the production process.
[0143] The ammonium and phosphonium compounds are removed by
thermal decomposition. The cleavage products occur in the
distillate, and catalyst residues can no longer be detected in the
polycarbonate. (see Example). Most of the cleavage products consist
of triphenlyphosphine and triphenlyphosphinoxide.
[0144] The polycarbonates may deliberately be branched by small
amounts ranging from 0.02 to 3.6 mol % (with respect to the
dihydroxy compound) of branching agents. Suitable branching agents
include compounds which are suitable for the production of
polycarbonate and which contain three or more functional groups,
preferably those with three or more than three phenolic OH groups,
for example 1,1,1-tri-(4-hydroxyphenyl)ethane and
isatin-bis-cresol.
[0145] Remaining amounts of monomers in the polycarbonate which are
still present due to the chemical balance of the reaction and the
process parameters like temperature, pressure and residence times
could be further reduced by use of suitable evaporation
processes.
[0146] Adjuvant substances and reinforcing agents may be admixed
with the polycarbonates according to the invention in order to
modify the properties thereof. Suitable adjuvant substances and
reinforcing agents include thermal and UV stabilizers, flow
enhancers, demoldingagents, flame retardants, pigments, finely
divided minerals, fiberous substances, e.g. alkyl and aryl
phosphites, phosphates, phosphanes, low molecular weight esters of
carboxylic acids, halogen compounds, salts, chalk, quartz flour,
glass and carbon fibers, pigments and combinations thereof.
Compounds such as these are described, for example, in WO-A
99/55772, pages 15-25, and in "Plastics Additives", by R. Gachter
and H. Muller, Hanser Publishers 1983, incorporated herein by
reference.
[0147] Furthermore, other polymers may also be admixed with the
polycarbonates according to the invention, e.g. polyolefins,
polyurethanes, polyesters, acrylonitrile-butadiene-styrene and
polystyrene.
[0148] These substances are preferably added to the finished
polycarbonate in conventional processing units, but may be added
during a different stage of the production process depending on the
requirements.
[0149] The polycarbonates obtained by the process according to the
invention may be processed in the usual manner in customary
machines, e.g. in extruders or injection molding machines, to form
moldings such as sheet or slabs.
[0150] Applications of the polycarbonates according to the
invention include:
[0151] 1. Safety glass panes or sheets, which, as is known, are
necessary in many areas of buildings, vehicles and aircraft, and
which are also used for the visors of helmets.
[0152] 2. The production of extruded sheeting and sheeting formed
from solution for displays or electric motors, and also sheeting
for skiing.
[0153] 3. The production of blown articles (se U.S. Pat. No.
2,964,794, for example).
[0154] 4. The production of transparent sheeting, particularly
cavity sheeting, for the cladding of buildings such as railway
stations, greenhouses and lighting installations.
[0155] 5. The production of traffic light housings or traffic
signs.
[0156] 6. The production of foamed materials (see DE-B 1 031 507,
for example).
[0157] 7. The production of fibers and filaments (see DE-B 1137 167
and DE-A 1 785 137, for example).
[0158] 8. Translucent plastics with a content of glass fibers for
photometric purposes (see DE-A 1 554 020, for example).
[0159] 9. The production of precision injection molded parts, such
as lens holders for example. Polycarbonate with a content of glass
fibers is used for this purpose, and optionally additionally
contains about 1-10% by weight MoS.sub.2with respect to its total
weight.
[0160] 10. Optical applications such as optical storage media (CDs,
DVDs), safety spectacles, or lenses for photographic and film
cameras (see DE-A 2701173, for example).
[0161] 11. Light transmission supports, particularly optical fiber
cables (see EP-A1 0089 801, for example).
[0162] 12. Electrical insulation materials for electrical
conductors and for plug housings and plug-in connectors.
[0163] 13. As a support material for organic photoconductors.
[0164] 14. The production of lamps, e.g. headlamps, lens covers or
lamp covers.
[0165] 15. Medical applications, e.g. oxygenators, dialysers.
[0166] 16. Foodstuff applications, such as bottles, crockery and
chocolate moulds.
[0167] 17. Applications in the automobile field, where contact with
fuels and lubricants can occur.
[0168] 18. Articles for sports, such as slalom poles for
example.
[0169] 19. Domestic articles such as kitchen sinks and letterbox
housings.
[0170] 20. For casings, e.g. electricity distribution boxes,
electrical appliances, domestic appliances.
[0171] 21. Components of domestic articles and of electrical and
electronic appliances.
[0172] 22. The production of motorcycle- and safety helmets.
[0173] 23. Parts of automobiles, such as window glass, dashboards,
bodywork parts and shock absorbers.
[0174] 24. Other applications such as feeding doors for stables or
animal cages.
[0175] In particular, the polycarbonates according to the invention
are suitable for use in the field of electronics, especially for
optical, magneto-optic and other data storage media.
[0176] The present invention also relates to products made from the
polycarbonates according to the invention.
EXAMPLES
Example 1
[0177] 94.7 kg/hour of a molten mixture consisting of 49.8 kg
diphenyl carbonate/hour (232.7 mol/hour) and 44.9 kg bisphenol
A/hour (196.9 mol/hour), with the addition of 0.0034 kg
tetraphenylphosphonium phenolate/hour (0.0079 mol/hour) dissolved
in 0.1 kg phenol/hour were pumped from a container through a heat
exchanger, and were heated to 190.degree. C. and passed through a
hold-up column. The mean residence time was 45 minutes.
[0178] The melt was then led, via a flashing valve, into a
separator at a pressure of 200 mbar. The melt flowing therefrom was
heated to 190.degree. C. again in a falling film evaporator, which
was also maintained at 200 mbar, and was caught in a container.
After a residence time of 20 minutes, the melt was pumped into the
next three stages of identical construction. The conditions in the
2.sup.nd/3.sup.rd/4.sup.th stages were 80/50/25 mbar;
230/250/270.degree. C. and 20/10/10 minutes. The oligomer formed
had relative viscosity of 1.068. All the vapors were passed via
pressure controllers into a column maintained under vacuum, and
were taken off as a condensate.
[0179] The oligomer was subsequently condensed in a basket-type
reactor at 270.degree. C. and 7.3 mbar, and at a residence time of
45 minutes, to form a high molecular weight oligomer. The relative
viscosity thereof was 1.134. The vapors were condensed.
[0180] The oligomer was condensed in a further basket-type reactor
at 311.degree. C. and 1.0 mbar to give a relative viscosity of
1.277. The mean residence time was determined as 130 minutes. The
vapors were thereby condensed after passing or inside of the vacuum
system.
[0181] The polycarbonate contains 245 ppm of terminal OH-groups and
the following contents of branched species were measured in the
polycarbonate: structure A: 226 ppm; structure B: 6 ppm; structure
C:<5 ppm; structure D: 138 ppm.
[0182] An amount of phosphorus corresponding to 0.000234 kg/hour
was detected in the combined condensates from the vapor streams.
This was equivalent to 96.3% of the amount of catalyst used
(=0.000243 kg/hour). Accordingly, no significant amounts of
catalyst residues or decomposition products remained in the
product. Phosphorous could not be detected.
Examples 2 to 8
[0183] By varying the ratio of diphenyl carbonate to bisphenol A,
polycarbonates were produced which contained comparable terminal
groups but which had different relative viscosities. Apart from the
vacuum, all the conditions such as throughput, catalyst and
temperature remained constant in these tests. The results are given
in Table 1.
1TABLE 1 Temp. of Rel. ppm ppb final Test viscosity OH Na reactor
YI ppm DPC 2 1.202 290 0 310 3.54 553 3 1.203 280 0 310 3.77 534 4
1.218 290 0 310 3.23 444 5 1.253 290 0 310 3.00 268 6 1.274 280 0
310 2.92 217 7 1.277 230 0 311 2.77 227 8 1.287 250 0 311 2.69
195
[0184] DPC denotes diphenyl carbonate.
Comparative Examples 9 to 14
[0185] In a further series of tests, the same solution of
tetra-phenylphosphonium phenolate in phenol, which was enriched
with different amounts of sodium phenolate/hour, however, was fed
into the molten mixture. The corresponding amounts, and the
equivalent amount of sodium in ppb with respect to polycarbonate,
are listed in Table 2. By varying the ratio of diphenyl carbonate
to bisphenol A, polycarbonates were produced which contained
comparable terminal groups but which had different relative
viscosities. These further results are given in Table 2.
2TABLE 2 Corresponding amount (g) of Temp. Rel. ppm Na ppb of final
ppm Test viscosity OH phenolate/hour Na reactor YI DPC 9 1.207 290
0.0630 250 290 3.69 585 10 1.249 310 0.0315 125 310 3.77 378 11
1.251 310 0.0630 250 300 3.84 348 12 1.276 290 0.0630 250 310 4.00
288 13 1.287 260 0.0252 100 310 3.54 260 14 1.292 250 0.0252 100
310 3.38 232
[0186] The test results are illustrated in FIGS. 1 to 3.
[0187] Although the invention has been described in detail in the
foregoing for the purpose of illustration, it is to be understood
that such detail is solely for that purpose and that variations can
be made therein by those skilled in the art without departing from
the spirit and scope of the invention except as it may be limited
by the claims.
* * * * *