U.S. patent application number 12/962802 was filed with the patent office on 2011-03-31 for method of making isosorbide polycarbonate.
This patent application is currently assigned to SABIC INNOVATIVE PLASTICS IP BV. Invention is credited to Hans-Peter Brack, Marianne Guyader, Han Vermeulen, Dennis James Patrick Maria Willemse.
Application Number | 20110077377 12/962802 |
Document ID | / |
Family ID | 41258854 |
Filed Date | 2011-03-31 |
United States Patent
Application |
20110077377 |
Kind Code |
A1 |
Brack; Hans-Peter ; et
al. |
March 31, 2011 |
Method of Making Isosorbide Polycarbonate
Abstract
A polycarbonate is provided that contains repeat units derived
from isosorbide and a residue derived from an activated diaryl
carbonate. The polycarbonate has .sup.1H-NMR peaks associated with
the repeat units derived from isosorbide. The polycarbonate
contains no more than a maximum allowable amount of
sorbitol-derived color bodies. If these color bodies are present in
the polycarbonate it has a .sup.1H-NMR peak associated with the
color bodies. The maximum allowable amount of color bodies are
present when the integrated area of the .sup.1H-NMR peak associated
with the color bodies divided by the integrated areas of the
.sup.1H-NMR peaks associated with the repeat units derived from
isosorbide is 0.025.
Inventors: |
Brack; Hans-Peter;
(Herrliberg, CH) ; Guyader; Marianne;
(Six-Fours-les-Plages, FR) ; Vermeulen; Han;
(Hoeven, NL) ; Willemse; Dennis James Patrick Maria;
(Standdaarbuiten, NL) |
Assignee: |
SABIC INNOVATIVE PLASTICS IP
BV
Bergen op Zoom
NL
|
Family ID: |
41258854 |
Appl. No.: |
12/962802 |
Filed: |
December 8, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12238683 |
Sep 26, 2008 |
7863404 |
|
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12962802 |
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Current U.S.
Class: |
528/196 ;
528/298; 528/370 |
Current CPC
Class: |
C08G 64/0208 20130101;
C08G 64/30 20130101; C08G 64/1608 20130101 |
Class at
Publication: |
528/196 ;
528/370; 528/298 |
International
Class: |
C08G 64/06 20060101
C08G064/06; C08G 65/42 20060101 C08G065/42; C08G 63/78 20060101
C08G063/78 |
Claims
1. A method of producing an isosorbide-containing polycarbonate
comprising the steps of: (i) providing a first monomer component
comprising isosorbide, (ii) performing a monomer component
conditioning step selected from the group consisting of: (a)
testing the first monomer component for the presence of sorbitol,
and if sorbitol is present, treating the first monomer component to
reduce the level of sorbitol to an amount less than 0.10 mole % in
the first monomer component, and (b) treating the first monomer
component to reduce the level of sorbitol to an amount less than
0.10 mole % in the first monomer component, (iii) forming a
reaction mixture by adding a diaryl carbonate and a catalyst to the
first monomer component, and (iv) allowing the reaction mixture to
react under polymerization conditions to build molecular weight,
thereby producing an isosorbide-containing polycarbonate.
2. The method of claim 1, wherein the method further comprises the
step of adding one or more additional monomer components to the
first monomer component selected from the group consisting of: BPA,
C.sub.36 branched fatty diol, C.sub.36 diacid, dodecanedioic acid,
and sebacic acid.
3. The method of claim 2, wherein the one or more additional
monomer components comprise BPA and C.sub.36 diacid.
4. The method of claim 1, wherein the method is accomplished by
performing step (iii) before or after (ii).
5. The method of claim 1, wherein the monomer component
conditioning step (ii) is performed to reduce the level of sorbitol
to an amount less than 0.05 mole % in the first monomer
component.
6. The method of claim 5, wherein the monomer component
conditioning step (ii) is performed to reduce the level of sorbitol
to an amount less than 0.01 mole % in the first monomer
component.
7. The method of claim 1, wherein in step (iv) the reaction mixture
reacts under melt polymerization conditions to prepare
polycarbonate, the catalyst is a melt transesterification catalyst,
and the diaryl carbonate comprises an ester-substituted diaryl
carbonate.
8. The method of claim 1, further comprising the step of: (v)
performing a polycarbonate treatment step selected from the group
consisting of: (a) testing the polycarbonate for the presence of a
sorbitol-derived color body associated with a NMR peak located over
a chemical shift at about 2.55 ppm in a .sup.1H-NMR spectrum, and
if the sorbitol-derived color body is present, treating the
polycarbonate prepared in step (i) to reduce the level of the
sorbitol-derived color body, and (b) treating the polycarbonate to
reduce the level of the sorbitol-derived color body.
9. A method of producing an isosorbide-containing polycarbonate,
comprising the steps of: (i) preparing a polycarbonate by reacting
isosorbide with a diaryl carbonate in the presence of a
polymerization catalyst under polymerization conditions, and (ii)
performing a polycarbonate treatment step selected from the group
consisting of: (a) testing the polycarbonate prepared in step (i)
for the presence of a sorbitol-derived color body associated with a
.sup.1H-NMR peak located at a chemical shift of about 2.55 ppm in a
.sup.1H-NMR spectrum, and if the sorbitol-derived color body is
present, treating the polycarbonate prepared in step (i) to reduce
the level of the sorbitol-derived color body, and (b) treating the
polycarbonate prepared in step (i) to reduce the level of the
sorbitol-derived color body, thereby producing an
isosorbide-containing polycarbonate product.
10. The method of claim 9, wherein in step (ii) the polycarbonate
prepared in step (i) is tested for the presence of the
sorbitol-derived color body using .sup.1H-NMR analysis, UV vis
spectra analysis, X-Rite analysis, or by visually comparing the
polycarbonate produced in step (i) with known color standards for
polycarbonate.
11. The method of claim 9, wherein in step (ii) the polycarbonate
prepared in step (i) is treated to reduce the presence of the
sorbitol-derived color body by dissolving the polycarbonate in a
solvent and precipitating the polycarbonate from solution.
12. The method of claim 11, wherein the solvent is a chlorinated
solvent selected from the group consisting of chloroform and
dichloromethane.
13. The method of claim 9, wherein step (ii) is performed to reduce
the concentration of the sorbitol-derived color body in the
polycarbonate produced in step (i) such the polycarbonate product
has less than 50% of the area contained under the .sup.1H-NMR peak
located at a chemical shift of about 2.55 ppm in a .sup.1H-NMR
spectrum of the product polycarbonate than does the polycarbonate
produced in step (i).
14. The method of claim 9, wherein step (ii) is performed to reduce
the concentration of the sorbitol-derived color body in the
polycarbonate produced in step (i) such the polycarbonate product
has less than 25% of the area contained under the .sup.1H-NMR peak
spanning a chemical shift of about 2.55 ppm in a .sup.1H-NMR
spectrum of the product polycarbonate than does the polycarbonate
produced in step (i).
15. The method of claim 9, wherein step (ii) is performed to
decrease the YI of the polycarbonate as measured using UV Vis
spectrometry by a value of 2 or more.
16. The method of claim 9, wherein step (i) is performed by
reacting the isosorbide with a diaryl carbonate in the presence of
one or more additional monomer components selected from the group
consisting of: BPA, C.sub.36 branched fatty diol, C.sub.36 diacid,
dodecanedioic acid, and sebacic acid.
17. The method of claim 16, wherein the one or more additional
monomer components comprise BPA and C.sub.36 diacid.
18. The method of claim 10, wherein in step (i) the reaction
mixture reacts under melt polymerization conditions to prepare
polycarbonate, wherein the catalyst is a melt polymerization
catalyst and the diaryl carbonate comprises and activated diaryl
carbonate.
19. A polycarbonate comprising repeat units derived from
isosorbide, and a residue derived from an activated diaryl
carbonate, wherein the polycarbonate has .sup.1H-NMR peaks
associated with the repeat units derived from isosorbide and
wherein the polycarbonate contains no more than a maximum allowable
amount of sorbitol-derived color bodies, wherein if
sorbitol-derived color bodies are present in the polycarbonate, the
polycarbonate has a .sup.1H-NMR peak associated with the
sorbitol-derived color bodies, and wherein the maximum allowable
amount of sorbitol-derived color bodies are present when the
integrated area of the .sup.1H-NMR peak associated with the
sorbitol-derived color bodies divided by the total combined
integrated areas of the .sup.1H-NMR peaks associated with the
repeat units derived from isosorbide is 0.025.
20. The method of claim 19, wherein the polycarbonate contains
sorbitol-derived color bodies and wherein the integrated area of
the .sup.1H-NMR peak associated with the sorbitol-derived color
bodies divided by the total combined integrated areas of the
.sup.1H-NMR peaks associated with the repeat units derived from
isosorbide is less than 0.01.
21. The polycarbonate of claim 19, wherein the polycarbonate
contains no detectable amount of sorbitol-derived color bodies.
22. The polycarbonate of claim 19, wherein the residue derived from
an activated diaryl carbonate is derived from an ester-substituted
diaryl carbonate and the residue comprises methyl salicylate.
Description
BACKGROUND
[0001] There is a significant interest in preparing polymers from
materials derived from biomass. The diol
1,4:3,6-dianhydro-D-sorbitol, hereinafter referred to as
isosorbide, is readily made from renewable resources, such as from
sugars and starches. According to the following reaction scheme,
isosorbide can be made from biomass derived starch through
hydrolysis, hydrogenation, and dehydration reactions.
##STR00001##
[0002] The use of isosorbide in polymerization reactions has been
found to result in poorer quality polycarbonate as compared to
polycarbonate made from other monomer components and specifically
those containing bisphenol-type compounds. These properties include
poorer color quality of the polymer as well as reduced mechanical
properties such as melt viscosity. There is a need to improve the
properties of polymers produced using isosorbide as a monomer
component.
SUMMARY OF THE INVENTION
[0003] The present Inventors found that polycarbonate produced
using isosorbide obtained from different suppliers resulted in
product polycarbonates having varying color properties, even though
the same or similar reaction conditions were employed. Studies were
conducted to determine what was causing the color variations
between the polymers and it was determined that the intermediate
reaction material, sorbitol, used in the formation of isosorbide
has an adverse effect on the color properties of product polymer.
The present Inventors also found that the isosorbide coming from
the different suppliers had varying amounts of sorbitol present in
the isosorbide that led to the formation of color bodies within the
produced polycarbonate. Without being bound by a particular
mechanism, the present Inventors believe that sorbitol reacts to
form color bodies under elevated polymerization reaction
temperatures and long reaction times.
[0004] The present invention provides at least two methods that may
be used together or separately for solving the presently recognized
problem. First, if present, the sorbitol is preferably removed from
the isosorbide prior to polymerization to form polycarbonate.
Second, the product polycarbonate may be treated to reduce the
amount of the sorbitol-derived color body after polymerization. By
using the methods of the present invention, the Inventors have
found that a product isosorbide-containing polycarbonate may be
prepared that has superior properties, including superior color, as
compared to isosorbide-containing polymers of the past.
[0005] In one embodiment, the present invention provides a method
of producing an isosorbide-containing polycarbonate. The method
comprises the steps of:
[0006] (i) providing a first monomer component comprising
isosorbide,
[0007] (ii) performing a monomer component conditioning step
selected from the group consisting of: (a) testing the first
monomer component for the presence of sorbitol, and if sorbitol is
present, treating the first monomer component to reduce the level
of sorbitol to an amount less than 0.10 mole % in the first monomer
component, and (b) treating the first monomer component to reduce
the level of sorbitol to an amount less than 0.10 mole % in the
first monomer component,
[0008] (iii) forming a reaction mixture by adding a diaryl
carbonate and a catalyst to the first monomer component, and
[0009] (iv) allowing the reaction mixture to react under
polymerization conditions to build molecular weight, thereby
producing an isosorbide-containing polycarbonate.
[0010] In another embodiment the present invention provides a
further method of producing an isosorbide-containing polycarbonate.
The method comprises the steps of:
[0011] (i) preparing a polycarbonate by reacting isosorbide with a
diaryl carbonate in the presence of a polymerization catalyst under
polymerization conditions, and
[0012] (ii) performing a polycarbonate treatment step selected from
the group consisting of: (a) testing the polycarbonate prepared in
step (i) for the presence of a sorbitol-derived color body
associated with a .sup.1H-NMR peak located at a chemical of about
2.55 ppm in a .sup.1H-NMR spectrum, and if the sorbitol-derived
color body is present, treating the polycarbonate prepared in step
(i) to reduce the level of the sorbitol-derived color body, and (b)
treating the polycarbonate prepared in step (i) to reduce the level
of the sorbitol-derived color body, thereby producing an
isosorbide-containing polycarbonate product.
[0013] By using the methods of the present invention one is able to
prepare an isosorbide-containing polycarbonate having superior
properties to those of the prior art. In a further embodiment, the
present invention provides a polycarbonate comprising repeat units
derived from isosorbide and a residue derived from an activated
diaryl carbonate. The polycarbonate has .sup.1H-NMR peaks
associated with the repeat units derived from isosorbide. The
polycarbonate contains no more than a maximum allowable amount of
sorbitol-derived color bodies, wherein if sorbitol-derived color
bodies are present in the polycarbonate, the polycarbonate has a
.sup.1H-NMR peak associated with the sorbitol-derived color bodies.
The maximum allowable amount of sorbitol-derived color bodies are
present when the integrated area of the .sup.1H-NMR peak associated
with the sorbitol-derived color bodies divided by the combined
integrated areas of the .sup.1H-NMR peaks associated with the
repeat units derived from isosorbide is 0.025.
BRIEF DESCRIPTION OF DRAWING
[0014] FIGS. 1,2, 4, and 6A-7 are graphical representations of
results obtained in the example section.
[0015] FIG. 3 is a schematic diagram of a reactor system used in
the example section.
[0016] FIGS. 5 and 8-10 are .sup.1H-NMR analysis spectras.
DETAILED DESCRIPTION
[0017] The present invention may be understood more readily by
reference to the following detailed description of preferred
embodiments of the invention and the examples included herein. The
present invention relates to isosorbide-containing polycarbonate
produced by polymerization reactions and to methods of forming
polycarbonate from isosorbide.
[0018] The present Inventors found that polycarbonate produced
using isosorbide obtained from different suppliers resulted in
product polycarbonates having varying color properties, even though
the same or similar reaction conditions were employed. Studies were
conducted to determine what was causing the color variations
between the polymers and it was determined that the intermediate
reaction material, sorbitol, used in the formation of isosorbide
has an adverse effect on the color properties of product polymer.
The present Inventors also found that the isosorbide coming from
the different suppliers had varying amounts of sorbitol present in
the isosorbide that led to the formation of color bodies within the
produced polycarbonate. Without being bound by a particular
mechanism, the present Inventors believe that sorbitol reacts to
form color bodies under elevated polymerization reaction
temperatures and long reaction times. Therefore, in order to
produce polycarbonate having superior color properties the
Inventors have found that the sorbitol concentration in the
reaction mixture should be reduced prior to treating at elevated
polymerization temperatures and/or the sorbitol-derived color body
concentration in the product polycarbonate should be reduced after
polymerization.
[0019] The Inventors have identified that the sorbitol-derived
color bodies have a detectable presence in isosorbide-containing
polycarbonate that relates to the color properties of the polymer
and to the presence and concentration of sorbitol in the isosorbide
monomer raw material. The present invention provides several
methods of reducing the sorbitol-derived color bodies in the
isosorbide-containing polycarbonate as well as provides an
isosorbide-containing polycarbonate having a maximum allowable
sorbitol-derived color body content specification that provides
good polycarbonate color properties.
[0020] In a first embodiment, the present invention provides a
method of producing polycarbonate where the monomer component is
tested for the presence sorbitol and if present the monomer
component is treated to reduce the presence of sorbitol, or
alternatively the monomer component is treated to reduce sorbitol
concentration regardless of whether it is present or not. In a
second embodiment, the polycarbonate product is tested for the
presence of the sorbitol-derived color body, and if it is present
the polycarbonate product is treated to reduce the presence of the
sorbitol-derived color body. In the alternative, the product
polycarbonate is treated to reduce the presence of the
sorbitol-derived color body regardless of whether it is present or
not. In another embodiment a combination of the first and second
embodiments may be employed to produce superior polycarbonate.
[0021] By using the methods of the present invention, the Inventors
have found that the isosorbide-containing product polycarbonate has
superior properties including improved color as compared to
polycarbonate prepared in the past that contains repeat units
derived from isosorbide. The polycarbonate contains residues
derived from an activated diaryl carbonate and no more than a
maximum allowable level of the sorbitol-derived color bodies.
Definitions
[0022] As used in the specification and claims of this application,
the following definitions, should be applied.
[0023] "a", "an", and "the" as an antecedent refer to either the
singular or plural. For example, "an aromatic dihydroxy compound"
refers to either a single species of compound or a mixture of such
species unless the context indicates otherwise.
[0024] "polycarbonate" refers to an oligomer or polymer comprising
residues of at least one monomer compound (e.g. a dihydroxy
compound) joined by carbonate linkages. In certain embodiments of
the invention, the polycarbonate comprises residues of an aromatic
dihydroxy compound and has a number average molecular weight, Mn,
measured relative to polystyrene (PS) standards of between 10,000
g/mol and 160,000 g/mol. In specific embodiments, the Mn measured
relative to PS is between 13,000 g/mol and 160,000 g/mol, for
example between 15,000 g/mol and 160,000 g/mol. In another
embodiment, the Mn (PS) is between 15,000 g/mol and 102,000 g/mol.
The term "polycarbonate" encompasses poly(carbonate-coester)
oligomers and polymers. Nothing in the description and claims of
this application should be taken as limiting the polycarbonate to
only one monomer residue unless the context is expressly limiting.
Thus, the application encompasses copolycarbonates with residues of
2, 3, 4, or more types of monomer compounds.
[0025] The term "sorbitol-derived" as it is used herein to describe
an undesirable color body of isosorbide-containing polycarbonate is
herein understood to mean that the Inventors believe that the color
body is derived from sorbitol. One basis, inter alia, for this
belief, as demonstrated in the example section, comes from the link
between the color of isosorbide-containing polycarbonate and the
amount of sorbitol contained in the reaction mixture formulation
used to prepared the polycarbonate. Another basis, inter alia, for
this belief, also as demonstrated in the example section, comes
from the link between the integrated area of peaks in .sup.1H-NMR
spectra and the amount of sorbitol contained in the reaction
mixture formulation used to prepared the polycarbonate and the
color of the polycarbonate.
[0026] The phrase "the polycarbonate has .sup.1H-NMR peaks
associated with the repeat units derived from isosorbide" and
similar phrases are herein understood to mean that the a
.sup.1H-NMR spectra of isosorbide-containing polycarbonate using
deuterated chloroform as a solvent has peaks located at chemical
shifts at about 4.50 ppm, about 4.56 ppm, and about 4.87 ppm with
reference to tetramethylsilane (TMS) that are associated with the
incorporated isosorbide monomer.
[0027] The phrase "the polycarbonate has a .sup.1H-NMR peak
associated with the sorbitol-derived color bodies" and similar
phrases are herein understood to mean that if sorbitol-derived
color bodies are present in the polycarbonate a .sup.1H-NMR spectra
of the isosorbide-containing polycarbonate using deuterated
chloroform as a solvent has a peak located at a chemical shift of
about 2.55 with reference to TMS that is associated with the
sorbitol-derived color bodies.
[0028] Reference throughout the specification to "one embodiment,"
"another embodiment," "an embodiment," "some embodiments," and so
forth, means that a particular element (e.g., feature, structure,
property, and/or characteristic) described in connection with the
embodiment is included in at least one embodiment described herein,
and may or may not be present in other embodiments. In addition, it
is to be understood that the described element(s) may be combined
in any suitable manner in the various embodiments.
[0029] Numerical values in the specification and claims of this
application, particularly as they relate to polymer compositions,
reflect average values for a composition that may contain
individual polymers of different characteristics. Furthermore,
unless indicated to the contrary, the numerical values should be
understood to include numerical values which are the same when
reduced to the same number of significant figures and numerical
values which differ from the stated value by less than the
experimental error of conventional measurement technique of the
type described in the present application to determine the
value.
Sorbitol and Isosorbide:
[0030] The methods of the present invention include the use of
isosorbide as a monomer component in the preparation of
polycarbonate. Furthermore, the polycarbonate of the present
invention comprises repeat units derived from isosorbide. According
to the following reaction scheme, isosorbide can be made from a
biomass derived starch through hydrolysis, hydrogenation, and
dehydration reactions.
##STR00002##
[0031] Sorbitol has the following structure:
##STR00003##
[0032] Isosorbide has the following structure:
##STR00004##
[0033] It has been found that isosorbide provided by commercial
suppliers contains sorbitol which is likely present due to the
incomplete conversion to isosorbide. As described herein, it is
believed that sorbitol reacts to form sorbitol-derived color bodies
at elevated temperatures and extended reaction times leading to
poor color properties of the resulting isosorbide-containing
polycarbonate. In one embodiment, the isosorbide monomer is tested
for the presence of sorbitol and treated to reduce the
concentration of sorbitol prior to polymerization. In another
embodiment, the isosorbide is simply treated to reduce the
concentration of sorbitol regardless of whether it is present or
not. Where isosorbide is tested for the presence of sorbitol, the
sorbitol content in isosorbide can be measured by an organic purity
measurement method such as chromatographic methods including Gas
Chromatography (GC) and High Performance Liquid Chromatography
(HPLC). A calibration curve may be generated in these
chromatographic methods by analyzing prepared standard solutions
having various concentrations of high purity reagent or analytical
grade sorbitol. In a preferred embodiment sorbitol content is
determined by HPLC.
Optional Additional Monomer Compounds:
[0034] The methods of the present invention include the use of
isosorbide as a monomer component in the preparation of
polycarbonate. In some embodiments another monomer compound (e.g. a
second monomer compound) or compounds are optionally selected for
incorporation into the product polycarbonate. Therefore, the
polycarbonates of the present invention may be isosorbide
homopolymers, copolymers, terpolymers, or polymers containing
several other monomer compounds.
[0035] The additional monomer compounds are not limited to
dihydroxy compounds or to aromatic dihydroxy compounds. For
example, preferred additional monomer compounds include compounds
having one or more functional groups capable of reacting with a
dihydroxy compound or a diaryl carbonate to give a chemical bond.
Some non-limiting examples of such reactive functional groups are
carboxylic acid, ester, amine functional groups and their
combinations. Typical monomer compounds will have two functional
groups capable of reacting with a dihydroxy compound or a diaryl
carbonate; however monofunctional compounds may be used as
chainstoppers or endcappers, and trifunctional or higher functional
compounds may be used as branching agents. However, dihydroxy and
aromatic dihydroxy compounds are frequently preferred for use in
these types of applications. Suitable dihydroxy compounds and
dihydroxy aromatic compounds are those as described in U.S. patent
application Ser. No. 11/863,659 which is incorporated herein by
reference for all purposes.
[0036] In one embodiment the additional monomer component comprises
a compound selected from the group consisting of: ethylene glycol,
1,3-Propanediol, 1,2-Propanediol, 1,4-Butanediol, 1,3-Butanediol,
1,5-Pentanediol, 1,6-Hexanediol, 1,7-Heptanediol, 1,10-Decanediol,
1,2-Cyclohexanediol, trans-1,2-Cyclohexanediol,
cis-1,2-Cyclohexanediol, 1,4-Cyclohexanedimethanol, C.sub.36
branched fatty diol, 1,2,6-Hexanetriol, resorcinol, Pluronic.RTM.
PE 3500, Pluronic.RTM. PE 6100, and UNITHOX.RTM. 480
ETHOXYLATE.
[0037] In another embodiment the additional monomer component
comprises a compound selected from the group consisting of:
bisphenol-A (BPA), C.sub.36 branched fatty diol, C.sub.36 diacid,
dodecanedioic acid, and sebacic acid. In yet a further preferred
embodiment, the additional monomer component comprises BPA and
C.sub.36 diacid.
The Diaryl Carbonate:
[0038] As described herein the methods of the present invention
relate to polymerization of monomer components comprising sorbitol
and those that create carbonate linkages within the polymer. The
type and conditions of the polymerization reactions are not
particularly limited. However, in a preferred embodiment as
described above, polycarbonate is prepared in a melt polymerization
reaction using a diaryl carbonate as explained below.
[0039] In the production of polycarbonate, the compounds which
react with the monomer compounds to form carbonate linkages (e.g.
the carbonate source) may be carbonate diesters, carbonyl halides,
etc. Specific examples of diaryl carbonates include: diphenyl
carbonate, ditolyl carbonate, bis(chlorophenyl)carbonate, m-cresyl
carbonate, and dinaphthyl carbonate. Of the various compounds of
this type diphenyl carbonate (DPC) is often preferred.
[0040] The diaryl carbonate can also be derived from an activated
diaryl carbonate or a mixture of an activated diaryl carbonate with
a non-activated diaryl carbonate. A preferred activated carbonate
of the present invention is an ester-substituted diaryl carbonate
such as bismethylsalicylcarbonate (BMSC). However, as used herein
the term "activated diaryl carbonate" is defined as a diaryl
carbonate which is more reactive than diphenyl carbonate toward
transesterification reactions. Such activated diaryl carbonates are
of the general formula:
##STR00005##
wherein Ar is a substituted aromatic radical having 6 to 30 carbon
atoms. The preferred activated diaryl carbonates have the more
specific general formula:
##STR00006##
wherein Q and Q' are each independently activating groups. A and A'
are each independently aromatic rings which can be the same or
different depending on the number and location of their substituent
groups, and n or n' are whole numbers of zero up to a maximum
equivalent to the number of replaceable hydrogen groups substituted
on the aromatic rings A and A', wherein a+a' is greater than or
equal to 1. R and R' are each independently substituent groups such
as alkyl, substituted alkyl, cycloalkyl, alkoxy, aryl, alkylaryl,
cyano, nitro, halogen, and carboalkoxy. The number of R groups is a
whole number and can be 0 up to a maximum equivalent to the number
of replaceable hydrogen groups on the aromatic rings A minus the
number n. The number of R' groups is a whole number and can be 0 up
to a maximum equivalent to the number of replaceable hydrogen
groups on the aromatic rings A minus the number n'. The number and
type of the R and R' substituents on the aromatic ring are not
limited unless they deactivate the carbonate and lead to a
carbonate which is less reactive than diphenylcarbonate. Typically,
the location of the R and R' substituents on the aromatic ring are
any one or any combination of the para and/or two ortho
positions.
[0041] Non-limiting examples of activating groups Q and Q' are:
alkoxycarbonyl groups, halogens, nitro groups, amide groups,
sulfone groups, sulfoxide groups, imine groups, or cyano groups
with structures indicated below:
##STR00007##
[0042] Specific and non-limiting examples of activated carbonates
include bismethylsalicylcarbonate, bis(o-chlorophenyl)carbonate,
bis(o-nitrophenyl)carbonate, bis(o-acetylphenyl)carbonate,
bis(o-phenylketonephenyl)carbonate, bis(o-formylphenyl)carbonate,
and bis(o-cyanophenyl)carbonate. Unsymmetrical combinations of
these structures, where the substitution number and type on A and
A' are different, are also possible to employ in the current
invention. A preferred structure for an activated carbonate is an
ester-substituted diaryl carbonate having the structure:
##STR00008##
wherein R' is independently at each occurrence a C.sub.1-C.sub.20
alkyl radical, C.sub.4-C.sub.20 cycloalkyl radical, or
C.sub.4-C.sub.20 aromatic radical; R.sup.2 is independently at each
occurrence a halogen atom, cyano group, nitro group,
C.sub.1-C.sub.20 alkyl radical, C.sub.4-C.sub.20 cycloalkyl
radical, C.sub.4-C.sub.20 aromatic radical, C.sub.1-C.sub.20 alkoxy
radical, C.sub.4-C.sub.20 cycloalkoxy radical, C.sub.4-C.sub.20
aryloxy radical, C.sub.1-C.sub.20 alkylthio radical,
C.sub.4-C.sub.20 cycloalkylthio radical, C.sub.4-C.sub.20 arylthio
radical, C.sub.1-C.sub.20 alkylsulfinyl radical, C.sub.4-C.sub.20
cycloalkylsulfinyl radical, C.sub.4-C.sub.20 arylsulfinyl radical,
C.sub.1-C.sub.20 alkylsulfonyl radical, C.sub.4-C.sub.20
cycloalkylsulfonyl radical, C.sub.4-C.sub.20 arylsulfonyl radical,
C.sub.1-C.sub.20 alkoxycarbonyl radical, C.sub.4-C.sub.20
cycloalkoxycarbonyl radical, C.sub.4-C.sub.20 aryloxycarbonyl
radical, C.sub.2-C.sub.60 alkylamino radical, C.sub.6-C.sub.60
cycloalkylamino radical, C.sub.5-C.sub.60 arylamino radical,
C.sub.1-C.sub.40 alkylaminocarbonyl radical, C.sub.4-C.sub.40
cycloalkylaminocarbonyl radical, C.sub.4-C.sub.40 arylaminocarbonyl
radical, or C.sub.1-C.sub.20 acylamino radical; and b is
independently at each occurrence an integer from 0 to 4. At least
one of the substituents CO.sub.2R.sup.1 is preferably attached in
an ortho position relative to the carbonate group.
[0043] Examples of preferred ester-substituted diaryl carbonates
include and are not limited to bismethylsalicylcarbonate (CAS
Registry No. 82091-12-1), bis(ethyl salicyl)carbonate, bis(propyl
salicyl)carbonate, bis(butylsalicyl)carbonate, bis(benzyl
salicyl)carbonate, bis(methyl 4-chlorosalicyl)carbonate and the
like. Typically bismethylsalicylcarbonate is preferred for use in
melt polycarbonate synthesis due to its lower molecular weight and
higher vapor pressure.
[0044] One method for determining whether a certain diaryl
carbonate is activated or is not activated is to carry out a model
transesterification reaction between the certain diaryl carbonate
with a phenol such as para-cumyl phenol. This phenol is preferred
because it possesses only one reactive site, it possesses a low
volatility, and it possesses a similar reactivity to bisphenol-A.
The model transesterification reaction was carried out at
temperatures above the melting points of the certain diaryl
carbonate and para-cumyl phenol and in the presence of a
transesterification catalyst, which is usually an aqueous solution
of sodium hydroxide or sodium phenoxide. Preferred concentrations
of the transesterification catalyst are about 0.001 mole % based on
the number of moles of the phenol or diaryl carbonate. A preferred
reaction temperature is 200.degree. C., but the choice of
conditions and catalyst concentration can be adjusted depending on
the reactivity of the reactants and melting points of the reactants
to provide a convenient reaction rate. The only limitation to
reaction temperature is that the temperature must be below the
degradation temperature of the reactants. Sealed tubes can be used
if the reaction temperatures cause the reactants to volatilize and
effect the reactant molar balance. The determination of the
equilibrium concentration of reactants is accomplished through
reaction sampling during the course of the reaction and then
analysis of the reaction mixture using a well-known detection
method to those skilled in the art such as HPLC (high pressure
liquid chromatography). Particular care needs to be taken so that
reaction does not continue after the sample has been removed from
the reaction vessel. This is accomplished by cooling down the
sample in an ice bath and by employing a reaction quenching acid
such as acetic acid in the water phase of the HPLC solvent system.
It may also be desirable to introduce a reaction quenching acid
directly into the reaction sample in addition to cooling the
reaction mixture. A preferred concentration for the acetic acid in
the water phase of the HPLC solvent system is 0.05% (v/v). The
equilibrium constant can be determined from the concentration of
the reactants and product when equilibrium is reached. Equilibrium
is assumed to have been reached when the concentration of
components in the reaction mixture reach a point of little or no
change on sampling of the reaction mixture. The equilibrium
constant can be determined from the concentration of the reactants
and products at equilibrium by methods well known to those skilled
in the art. A diaryl carbonate which possesses an equilibrium
constant of greater than 1 is considered to possess a more
favorable equilibrium than diphenylcarbonate and is an activated
carbonate, whereas a diaryl carbonate which possesses an
equilibrium constant of 1 or less is considered to possess the same
or a less favorable equilibrium than diphenylcarbonate and is
considered not to be activated. It is generally preferred to employ
an activated carbonate with very high reactivity and equilibrium
constants compared to diphenylcarbonate when conducting
transesterification reactions. Preferred are activated carbonates
with an equilibrium constant greater than at least 10 times that of
diaryl carbonate.
[0045] Some non-limiting examples of non-activating groups which,
when present in an ortho position relative to the carbonate group,
would not be expected to result in activated carbonates are alkyl
and cycolalkyl. Some specific and non-limiting examples of
non-activated carbonates are bis(o-methylphenyl)carbonate,
bis(p-cumylphenyl)carbonate, and
bis(p-(1,1,3,3-tetramethyl)butylphenyl)carbonate. Unsymmetrical
combinations of these structures are also expected to result in
non-activated carbonates.
[0046] Unsymmetrical diaryl carbonates wherein one aryl group is
activated and one aryl is unactivated or de-activated would also be
useful in this invention if the activating group renders the diaryl
carbonate still more reactive than diphenyl carbonate.
[0047] The theoretical stoichiometry of the reaction within the
melt polymerization reaction mixture requires a molar ratio of
monomer composition to diaryl carbonate composition of 1:1.
However, in practicing the present invention the molar ratio in the
melt reaction mixture is suitably between 0.25:1 to 3:1, for
example equal to or between 0.9 to 1.1, more preferably between
1:0.95 to 1:1.05 and more preferably between 1:0.98 to 1:1.02.
The Activated Carbonate Residue:
[0048] In a preferred embodiment as described herein, polycarbonate
is prepared in a melt polymerization reaction using an activated
diaryl carbonate. In this embodiment the melt reaction components
comprise the monomer component comprising isosorbide, an activated
diaryl carbonate, and a melt transesterification catalyst. As the
reaction proceeds to form polycarbonate an activated diaryl
carbonate residue is produced and is removed from the reaction
products to drive the melt transesterification reaction forward and
to build molecular weight of the product polycarbonate. The
identity of the activated diaryl carbonate residue will depend upon
the activated diaryl carbonate used in the process. Polycarbonates
produced using an activated diaryl carbonate will contain residual
amounts of the activated diaryl carbonate residue.
[0049] If an activated diaryl carbonate (e.g. ester-substituted
diaryl carbonate) such as bismethylsalicylcarbonate (BMSC) is
employed, a typical activated carbonate residue will be a phenolic
compound such as an ester-substituted phenol (e.g. methyl
salicylate). Similarly if an ester-substituted diaryl carbonate
such as bisethylsalicylcarbonate is employed, a typical phenolic
by-product will be an ester-substituted phenol such as ethyl
salicylate.
[0050] In certain preferred embodiments of the present invention
the activated carbonate residue is at least one ester-substituted
phenol having the structure,
##STR00009##
wherein R.sup.1 is a C.sub.1-C.sub.20 alkyl group, C.sub.4-C.sub.20
cycloalkyl group, or C.sub.4-C.sub.20 aryl group; R.sup.2 is
independently at each occurrence a halogen atom, cyano group, nitro
group, C.sub.1-C.sub.20 alkyl group, C.sub.4-C.sub.20 cycloalkyl
group, C.sub.4-C.sub.20 aryl group, C.sub.1-C.sub.20 alkoxy group,
C.sub.4-C.sub.20 cycloalkoxy group, C.sub.4-C.sub.20 aryloxy group,
C.sub.1-C.sub.20 alkylthio group, C.sub.4-C.sub.20 cycloalkylthio
group, C.sub.4-C.sub.20 arylthio group, C.sub.1-C.sub.20
alkylsulfinyl group, C.sub.4-C.sub.20 cycloalkylsulfinyl group,
C.sub.4-C.sub.20 arylsulfinyl group, C.sub.1-C.sub.20 alkylsulfonyl
group, C.sub.4-C.sub.20 cycloalkylsulfonyl group, C.sub.4-C.sub.20
arylsulfonyl group, C.sub.1-C.sub.20 alkoxycarbonyl group,
C.sub.4-C.sub.20 cycloalkoxycarbonyl group, C.sub.4-C.sub.20
aryloxycarbonyl group, C.sub.2-C.sub.60 alkylamino group,
C.sub.6-C.sub.60 cycloalkylamino group, C.sub.5-C.sub.60 arylamino
group, C.sub.1-C.sub.40 alkylaminocarbonyl group, C.sub.4-C.sub.40
cycloalkylaminocarbonyl group, C.sub.4-C.sub.40 arylaminocarbonyl
group, or C.sub.1-C.sub.20 acylamino group; and b is an integer
0-4.
[0051] Examples of ester-substituted phenols (i.e. activated
carbonate residues) include methyl salicylate, ethyl salicylate,
propyl salicylate, butyl salicylate, 4-chloro methyl salicylate,
benzyl salicylate and mixtures thereof. Typically, methyl
salicylate is preferred. Further the solvent may be recovered and
reused. For example, ester-substituted phenols such as methyl
salicylate may be recovered, purified, and reacted with phosgene to
make ester-substituted diaryl carbonates which in turn can be used
to prepare oligomeric polycarbonates. Typically, purification of
the recovered ester-substituted phenol is efficiently carried out
by distillation.
The Catalyst:
[0052] As described herein the methods of the present invention
relate to polymerization of monomer components comprising sorbitol
and those that create carbonate linkages within the polymer. The
type and conditions of the polymerization reaction are not
particularly limited. However, in a preferred embodiment as
described above, polycarbonate is prepared in a melt polymerization
reaction using an activated diaryl carbonate. A typical melt
transesterfication catalyst system used in accordance with the
preferred method of the present invention is an alpha or an
alpha/beta catalyst system comprising a base, and preferably
comprising at least one source of alkaline earth ions or alkali
metal ions, and/or at least one quaternary ammonium compound, a
quaternary phosphonium compound or a mixture thereof. The alpha
source of alkaline earth ions or alkali metal ions being used is in
an amount such that the amount of alkaline earth or alkali metal
ions present in the reaction mixture is in a range between
10.sup.-5 and 10.sup.-8 moles alkaline earth or alkali metal ion
per mole of dihydroxy compound employed.
[0053] If employed, the beta catalyst is a quaternary phosphonium
and/or a quaternary ammonium compound. The quaternary ammonium is
selected from the group of organic ammonium compounds having
structure,
##STR00010##
wherein R.sup.20-R.sup.23 are independently a C.sub.1-C.sub.20
alkyl radical, C.sub.4-C.sub.20 cycloalkyl radical, or a
C.sub.4-C.sub.20 aryl radical; and X.sup.- is an organic or
inorganic anion. In one embodiment of the present invention anion
X.sup.- is selected from the group consisting of hydroxide, halide,
carboxylate, sulfonate, sulfate, formate, carbonate, and
bicarbonate.
[0054] Non-limiting examples of suitable organic quaternary
ammonium compounds are tetramethyl ammonium hydroxide, tetrabutyl
ammonium hydroxide, tetramethyl ammonium acetate, tetramethyl
ammonium formate and tetrabutyl ammonium acetate. Tetramethyl
ammonium hydroxide is often preferred.
[0055] The quaternary phosphonium compound is selected from the
group of organic phosphonium compounds having structure,
##STR00011##
wherein R.sup.24-R.sup.27 are independently a C.sup.1-C.sup.20
alkyl radical, C.sup.4-C.sup.20 cycloalkyl radical, or a
C.sub.4-C.sub.20 aryl radical; and X.sup.- is an organic or
inorganic anion. In one embodiment of the present invention anion
X.sup.- is an anion selected from the group consisting of
hydroxide, halide, carboxylate, sulfonate, sulfate, formate,
carbonate, and bicarbonate. Suitable organic quaternary phosphonium
compounds are illustrated by tetramethyl phosphonium hydroxide,
tetramethyl phosphonium acetate, tetramethyl phosphonium formate,
tetrabutyl phosphonium hydroxide, and tetrabutyl phosphonium
acetate (TBPA). TBPA is often preferred.
[0056] Where X.sup.- is a polyvalent anion such as carbonate or
sulfate it is understood that the positive and negative charges in
the quaternary ammonium and phosphonium structures are properly
balanced. For example, where R.sup.20-R.sup.23 are each methyl
groups and X.sup.- is carbonate, it is understood that X.sup.-
represents 1/2 (CO.sub.3.sup.2).
[0057] Suitable sources of alkaline earth ions include alkaline
earth hydroxides such as magnesium hydroxide and calcium hydroxide.
Suitable sources of alkali metal ions include the alkali metal
hydroxides illustrated by lithium hydroxide, sodium hydroxide and
potassium hydroxide. Other sources of alkaline earth and alkali
metal ions include salts of carboxylic acids, such as sodium
acetate and derivatives of ethylene diamine tetraacetic acid (EDTA)
such as EDTA tetrasodium salt, and EDTA magnesium disodium salt.
Sodium hydroxide is often preferred.
[0058] The amount of catalyst employed is typically based upon the
total number of moles of dihydroxy compound employed in the
polymerization reaction. When referring to the ratio of catalyst,
for example phosphonium salt, to all dihydroxy compounds employed
in the polymerization reaction, it is convenient to refer to moles
of phosphonium salt per mole of the dihydroxy compound(s), meaning
the number of moles of phosphonium salt divided by the sum of the
moles of each individual dihydroxy compound present in the reaction
mixture. The amount of organic ammonium or phosphonium salts
employed typically will be in a range between 1.times.10.sup.-2 and
1.times.10.sup.-5, preferably between 1.times.10.sup.-3 and
1.times.10.sup.-4 moles per mole of the first and second dihydroxy
compounds combined. The inorganic metal hydroxide catalyst
typically will be used in an amount corresponding to between
1.times.10.sup.-4 and 1.times.10.sup.-8, preferably
1.times.10.sup.-4 and 1.times.10.sup.-7 moles of metal hydroxide
per mole of the first and second dihydroxy compounds combined.
[0059] In a most preferred catalyst system of the present
invention, solely an alkali metal hydroxide may be employed. As
discussed above, alkali metal hydroxides are illustrated by sodium
hydroxide, lithium hydroxide, and potassium hydroxide. Due to its
relatively low cost, sodium hydroxide is often preferred.
The Methods of the Present Invention:
[0060] The present invention provides various methods for solving
the presently recognized problem of sorbitol content in isosorbide
used as a monomer in the preparation of polycarbonate. In a first
embodiment, the concentration of sorbitol is preferably reduced in
the isosorbide component prior to polymerization to form
polycarbonate. In a second embodiment, the product polycarbonate
may be treated to reduce the amount of the sorbitol-derived color
body after polymerization. By using the methods of the present
invention, the Inventors have found that a product
isosorbide-containing polycarbonate may be prepared that has
superior properties, including superior color, as compared to
isosorbide-containing polymers of the past.
[0061] In the first embodiment, the method comprises the steps
of:
[0062] (i) providing a first monomer component comprising
isosorbide,
[0063] (ii) performing a monomer component conditioning step
selected from the group consisting of: (a) testing the first
monomer component for the presence of sorbitol, and if sorbitol is
present, treating the first monomer component to reduce the level
of sorbitol to an amount less than 0.10 mole % in the first monomer
component, and (b) treating the first monomer component to reduce
the level of sorbitol to an amount less than 0.10 mole % in the
first monomer component,
[0064] (iii) forming a reaction mixture by adding a diaryl
carbonate and a catalyst to the first monomer component, and
[0065] (iv) allowing the reaction mixture to react under
polymerization conditions to build molecular weight, thereby
producing an isosorbide-containing polycarbonate.
[0066] Sorbitol is believed to be present in isosorbide compounds
coming from suppliers of the raw material. It is believed that when
sorbitol is present in the isosorbide raw material it reacts to
form the sorbitol-derived color body under polymerization
conditions involving elevated heat and residence times. The present
Inventors have found it desirable to prepare and use isosorbide
monomer components comprising less than 0.1 mol % sorbitol, for
example less than 0.08 mol % sorbitol, and most preferably less
than 0.05 mol % sorbitol. In more preferred embodiments, the
present Inventors have found that isosorbide monomer components
comprising less than 0.04 mol % (e.g. less than 0.03 mol % or less
than 0.01 mol %) sorbitol, are best for use in the present
invention. In the most preferred embodiment, the isosorbide monomer
component is treated to reduce the sorbitol content to an amount
that is undetectable in the isosorbide monomer component.
[0067] As described herein, where the isosorbide monomer component
is tested for the presence of sorbitol the testing mechanism is not
particularly limited and can be accomplished by known methods of
determining the presence and concentration of sorbitol. In a
preferred embodiment, as described above, the testing step is
performed by HPLC. The step of testing preferably occurs at the
location of formation of the isosorbide-containing polycarbonate.
However, the step of testing may be performed "offsite", for
example at the isosorbide production facility or somewhere in
between for example at a third party certification agency,
laboratory, or warehouse where the isosorbide product is tested and
assigned a sorbitol grading value or a sorbitol content level. In
this later embodiment where the monomer is assigned the sorbitol
grading value "offsite", the treating of the monomer component will
proceed based on the assigned sorbitol grading value. For example
where the isosorbide is assigned a sorbitol grading value of less
than 0.10 mol % at an offsite location (e.g. a third party chemical
supplier), that isosorbide monomer component may be ordered from
the supplier and used in the production of polycarbonate and such
use falls within the scope of the step "testing the first monomer
component for the presence of sorbitol, and if sorbitol is present,
treating the first monomer component to reduce the level of
sorbitol to an amount less than 0.10 mole % in the first monomer
component".
[0068] The step of "treating the first monomer component to reduce
the level of sorbitol to an amount less than 0.10 mole % in the
first monomer component" likewise is not particularly limited and
can occur by known purification methods such as washing,
extraction, distillation, or combinations thereof. The step of
testing and/or treating the isosorbide monomer component may occur
before, during, or after the formation of the reaction mixture as
recited in step (iii) above. Similar to the description of the
testing step described above, the treatment step may occur at an
"offsite" location and the treated isosorbide product then used in
the "onsite" polymerization process. This offsite testing and/or
treatment falls within the scope of the present invention.
[0069] The step of "allowing the reaction mixture to react under
polymerization conditions to build molecular weight" is likewise
not particularly limited. As described herein the methods of the
present invention relate to polymerization of monomer components
comprising isosorbide and those that create carbonate linkages
within the polymer. The type of reaction and reaction conditions of
the polymerization reaction are not particularly limited as such
polymerization reactions are well known in the art. In a preferred
embodiment, however, the polycarbonate is prepared in a melt
polymerization reaction using an activated diaryl carbonate, such
as an ester-substituted diaryl carbonate (e.g. BMSC). Melt
polymerization reactions that create the transesterification
between the free hydroxyl ends of dihydroxy compounds with the
carbonate source are known and are not particularly limited with
respect to the present invention. For example, U.S. patent
application Ser. Nos. 11/863,659, 11/427,861, and 11/427,885, which
are incorporated herein by reference for all purposes, disclose
preferred processes and catalysts for the melt production of
polycarbonate suitable for use with the methods of the present
invention.
[0070] A second embodiment of the present invention provides a
further method of producing an isosorbide-containing polycarbonate.
The method comprises the steps of:
[0071] (i) preparing a polycarbonate by reacting isosorbide with a
diaryl carbonate in the presence of a polymerization catalyst under
polymerization conditions, and
[0072] (ii) performing a polycarbonate treatment step selected from
the group consisting of: (a) testing the polycarbonate prepared in
step (i) for the presence of a sorbitol-derived color body
associated with a .sup.1H-NMR peak located at a chemical shift of
about 2.55 ppm in a .sup.1H-NMR spectrum, and if the
sorbitol-derived color body is present, treating the polycarbonate
prepared in step (i) to reduce the level of the sorbitol-derived
color body, and (b) treating the polycarbonate prepared in step (i)
to reduce the level of the sorbitol-derived color body, thereby
producing an isosorbide-containing polycarbonate product.
[0073] In this second embodiment isosorbide-containing
polycarbonate is prepared and then is subsequently tested for the
presence of, and treated if necessary to reduce the level of, the
sorbitol-derived color body. Alternatively, the polycarbonate is
simply treated, without testing for the presence of the
sorbitol-derived color body.
[0074] The step of preparing polycarbonate as with the first
embodiment is not particularly limited. The isosorbide-containing
polycarbonate may be prepared offsite at a polycarbonate production
facility (e.g. by a third party) and then shipped to the
polycarbonate treatment site to perform treatment step (ii). In a
preferred embodiment, however, the isosorbide-containing
polycarbonate is prepared onsite by a melt polymerization reaction
using an activated diaryl carbonate such as BMSC. Preferably
directly after preparation, the polycarbonate is then subjected to
treatment step (ii).
[0075] Where the isosorbide-containing polycarbonate is tested for
the presence of the sorbitol-derived color body, the testing
mechanism is not particularly limited and can be accomplished by
known methods of detecting the presence of color bodies or
components within samples. For example the polycarbonate can be
tested for the presence of the sorbitol-derived color body using
.sup.1H-NMR analysis, UV vis spectra analysis, or X-Rite analysis.
Alternatively, because the sorbitol-derived color body can create
visually observable color within the product polycarbonate, the
isosorbide-containing polycarbonate can be compared with known
color standards for polycarbonate to determine if the color body is
present and its concentration should be reduced. In this later
embodiment comparative samples of isosorbide-containing
polycarbonate can be prepared that contain quantified amounts of
the sorbitol-derived color body. These samples are then used to
compare produced isosorbide-containing polycarbonate to visually
determine the content of the sorbitol-derived color body within the
produced polycarbonate. Treatment steps then can be designed and
conducted within the scope of the present invention based upon the
visual comparison of the produced polycarbonate to the sample. In a
preferred embodiment the concentration of the sorbitol-derived
color bodies is preferably quantified using .sup.1H-NMR deuterated
chloroform (CDCl.sub.3) as a solvent and TMS as the reference as
described below.
[0076] The step of "treating the polycarbonate prepared in step (i)
to reduce the level of the sorbitol-derived color body" is likewise
is not particularly limited and can occur by known purification
methods such as washing, extraction, and/or distillation. In a
preferred embodiment however, the polycarbonate is treated to
reduce the presence of the sorbitol-derived color body by
dissolving the polycarbonate in a solvent and precipitating the
polycarbonate from solution. The present Inventors have found that
the solvent is not particularly limited. However, in a preferred
embodiment the solvent is a chlorinated solvent, for example a
solvent selected from the group consisting of: chloroform and
dichloromethane.
[0077] In a preferred embodiment, the step of "treating the
polycarbonate prepared in step (i) to reduce the level of the
sorbitol-derived color body" is performed to reduce the
concentration of the sorbitol-derived color body in the
polycarbonate produced in step (i) such the polycarbonate product
has less than 75% (e.g. less than 50%, more preferably less than
25%, for example less than 5%) of the area contained under the
.sup.1H-NMR peak located at a chemical shift of about 2.55 ppm in a
.sup.1H-NMR spectrum of the product polycarbonate than does the
polycarbonate produced in step (i).
[0078] In another preferred embodiment, the step of "treating the
polycarbonate prepared in step (i) to reduce the level of the
sorbitol-derived color body" is performed to decrease the YI of the
polycarbonate by a value of 2 or more (e.g. by a value of 5, 10,
15, 20, 25, 30, or more) as measured using UV-Vis spectrometry
methods described herein.
The Isosorbide-Containing Polycarbonate:
[0079] Without being bound by a particular mechanism, the present
Inventors believe that sorbitol reacts to form sorbitol-derived
color bodies under elevated polymerization reaction temperatures
and long reaction times. The Inventors have identified that the
sorbitol-derived color bodies have a detectable presence in
isosorbide-containing polycarbonate that relates to the color
properties of the polymer and to the presence and concentration of
sorbitol in the isosorbide monomer raw material. By using the
methods of the present invention one is able to produce an
isosorbide-containing polycarbonate that has superior color
properties compared to polycarbonates prepared using past methods.
The present Inventors have found that in order to provide
isosorbide-containing polycarbonate having good color that the
polycarbonate should contain no more than a the below defined
maximum allowable amount of sorbitol-derived color bodies.
[0080] Using the .sup.1H-NMR analysis described below polymer
samples were analyzed in deuterated chloroform (50 to 70 mg polymer
in 1.0 ml CDCl.sub.3) containing 0.1 wt % tetramethylsilane (TMS)
as reference from which chemical shifts in ppm were measured. The
Inventors have found that the sorbitol-derived color body is
associated with a peak located at a chemical shift of about 2.55
ppm in an .sup.1H-NMR spectrum. See FIG. 5 for a representative
example of the peak at about 2.55 ppm in a .sup.1H-NMR spectrum.
Using .sup.1H-NMR analysis, the concentration of the
sorbitol-derived color body can be quantified as a relative peak
area by determining the integrated area of a peak associated with
the color body relative to that of three peaks associated with the
incorporated isosorbide residues. The relative area of the peak at
about 2.55 ppm has been found to correlate strongly with
sorbitol-derived color bodies and with the color of the
isosorbide-containing polymers made using reaction mixtures
containing varying amounts of sorbitol.
[0081] In one embodiment, the amount or a quantified concentration
of the sorbitol-derived color body can be determined by visually
comparing the produced isosorbide-containing polycarbonate to
isosorbide-containing polycarbonate "standards" that contain a
previously quantified amount of the sorbitol-derived color body. In
another embodiment the amount or a quantified concentration of the
sorbitol-derived color body can be determined by comparing the
relative area of the peak at about 2.55 ppm in a .sup.1H-NMR
spectrum of the isosorbide-containing polycarbonate to the relative
areas of other peaks contained in the spectrum that are associated
with other components of the polycarbonate (e.g. the isosorbide,
the diaryl carbonate, and/or other monomer components). For
example, in order to give an amount or quantify the concentration
of the sorbitol-derived color body relative to the incorporated
isosorbide, the isosorbide peak at about 4.87 ppm assigned to the
two protons (assigned to methine protons at C-1 and C-4 in the
figure below) can be integrated, and the integrated area set at a
value of 1000. Two other isosorbide (IS) peaks at about 4.50 ppm
(assigned here to the coupling between C-5 proton and one of C-6
methylene protons in the figure below) and about 4.56 ppm (assigned
here to the coupling between C-2 proton and one of C-3 methylene
protons in the figure below) can also integrated, and their
integrated areas set to values of 500 each because each peak is
assigned to one proton. This process then establishes three
isosorbide peaks at about 4.87 ppm, 4.56 ppm, and 4.50 ppm as
constant relative internal standards of area 1000, 500, and 500,
respectively (e.g. a total area of 2000). The peak at about 2.55
ppm associated with the sorbitol-derived color body can then be
integrated, and the area of this peak relative to those of the
three isosorbide peaks (e.g. an internal standard area of 2000) can
be obtained and quantified from the .sup.1H-NMR spectrum. The
chemical structure of isosorbide is:
##STR00012##
[0082] The polycarbonate of the present invention comprises repeat
units derived from isosorbide and a residue (e.g. methyl
salicylate) derived from an activated diaryl carbonate (e.g. BMSC).
As described above, the polycarbonate has .sup.1H-NMR peaks
associated with the repeat units derived from isosorbide located at
chemical shifts of about 4.50 ppm, 4.56 ppm, and 4.87 ppm in a
.sup.1H-NMR spectrum using deuterated chloroform as a solvent and
TMS as the reference. The present Inventors have found that in
order for the polycarbonate to have good color properties, the
polycarbonate should contain no more than a maximum allowable
amount of sorbitol-derived color bodies. If the color bodies are
present the polycarbonate will have a .sup.1H-NMR peak associated
with the sorbitol-derived color bodies located at a chemical shift
of about 2.55 ppm in a .sup.1H-NMR spectrum using deuterated
chloroform as a solvent and TMS as the reference.
[0083] The maximum allowable amount of sorbitol-derived color
bodies are present in the polycarbonate when the integrated area of
the .sup.1H-NMR peak associated with the sorbitol-derived color
bodies divided by the combined integrated areas of the .sup.1H-NMR
peaks associated with the repeat units derived from isosorbide is
0.025. For example, using the above constant internal standard
method of assigning the three peaks associated with isosorbide a
combined area value of 2000, the peak at about 2.55 ppm associated
with the sorbitol-derived color bodies will contain an area of 50
(e.g. 50/2000=0.025) when the polycarbonate contains the maximum
allowable amount of sorbitol-derived color bodies. In more
preferred embodiments the polycarbonate will comprises less than
the maximum allowable amount of sorbitol-derived color bodies. In
these more preferred embodiments, the integrated area of the
.sup.1H-NMR peak associated with the sorbitol-derived color bodies
divided by the combined integrated areas of the .sup.1H-NMR peaks
associated with the repeat units derived from isosorbide is less
than 0.02 (e.g. 40/2000=0.02), for examples less than 0.01 (e.g.
20/2000=0.01), and more preferably less than 0.005 (e.g.
10/2000=0.005). In a most preferred embodiment the polycarbonate
contains no detectable amount of sorbitol-derived color bodies.
[0084] The measurement of color properties of the polycarbonate is
not particularly limited. For example, the color properties of
solid polymer samples can be measured by a spectrometer such as a
spherically-based, 0/45 or 45/0, or multi-angle spectrophotometer
or a colorimeter. In one embodiment, they are measured by an Xrite
Teleflash 130 instrument, specifically by an Xrite Teleflash 130
instrument using the conditions given in the example section below.
The color properties of irregularly shaped polymer samples may be
measured after dissolution by solution spectroscopy. In a preferred
embodiment the color properties of polycarbonate are preferably
measured using UV-Vis spectroscopy and the conditions expressed
below in the example section.
EXAMPLES
[0085] Having described the invention in detail, the following
examples are provided. The examples should not be considered as
limiting the scope of the invention, but merely as illustrative and
representative thereof.
[0086] (WE) as used herein is understood to mean "working example"
while (CE) is understood to mean "comparative example". The terms
"working" and "comparative" are simply used to demonstrate
comparisons to other examples. Working and comparative examples may
or may not be an example within the scope of the present
invention.
[0087] In the following examples the following processes,
measurements, and experimental tests were performed.
.sup.1H-NMR Analysis Procedure
[0088] Nuclear magnetic resonance spectroscopy was used to detect
and characterize the chemical structure of the sorbitol-derived
color body and to calculate the concentration of the color body
relative to that of isosorbide based on the relative areas of the
color body peak and three isosorbide peaks.
[0089] Samples were analyzed in deuterated chloroform (50 to 70 mg
polymer in 1.0 ml CDCl.sub.3) containing 0.1 wt % tetramethylsilane
(TMS) as reference from which chemical shifts in ppm were measured.
Spectral analysis and quantification using .sup.1H-NMR was carried
out as follows. .sup.1H-NMR spectra were recorded on a Bruker
Avance Ultrashielded 400 MHz (1H-Frequency) system equipped with a
5 mm QNP Probehead. The following settings were used: [0090]
Acquisition time: 2.56 secs [0091] Number of scans: 256 [0092]
Recycle delay: 10 secs [0093] Experiment: 30 degr.
.sup.1H-pulsewidth [0094] Temperature: 44.degree. C.
[0095] The spectra were obtained by Fourier transformation of the
Free Induction Decay (FID) after application of 0.3 Hz apodization
and phase correction. The chemical shift of the TMS proton was set
at 0.0 ppm.
[0096] The concentration of the color body derived from sorbitol
was quantified as a relative peak area by determining the
integrated area of a peak associated with the color body relative
to that of three peaks associated with the incorporated isosorbide
residues. The relative area of the Peak at about 2.55 ppm (See FIG.
5 for an example of peak at about 2.55 ppm found in 1H-NMR
analysis) has been found to correlate strongly with the color of
the polymers obtained by the spiking of polymerization reactions
with sorbitol. In order to give a concentration of the color body
relative to the incorporated isosorbide residues, the isosorbide
peak at about 4.87 ppm assigned to the two protons (assigned to
methine protons at C-1 and C-4) was integrated, and the integrated
area was set at a value of 1000. Two other IS peaks at about 4.50
ppm (assigned here to the coupling between C-5 proton and one of
C-6 methylene protons) and about 4.56 ppm (assigned here to the
coupling between C-2 proton and one of C-3 methylene protons) were
also integrated, and their integrated areas were set to values of
500 each because each peak is assigned to one proton. This process
then established the three isosorbide peaks at about 4.87 ppm, 4.56
ppm, and 4.50 ppm as constant relative internal standards of area
1000, 500, and 500 respectively (e.g. a total area of 2000). The
peak at about 2.55 ppm due to the sorbitol-derived color body was
then integrated, and the area of this peak relative to those of the
three isosorbide peaks (e.g. a total of 2000) was obtained for the
.sup.1H-NMR spectrum. The chemical structure of isosorbide is:
##STR00013##
UV-Vis Procedure
[0097] UV-Vis spectroscopy was used to quantify the color
properties of the polymers prepared with and without spiking of
sorbitol into the polymerization process. Polymer sample solutions
were prepared by dissolving 0.5 g of the polymer sample in 10 ml of
chloroform (5 mass/volume % solution). A UV/Vis spectrometer Lambda
800 from PerkinElmer.RTM. Instruments, the software UV Winlab
Version 3.00.03 and the following settings were used: [0098]
Absorbance spectra: from 380 nm to 720 nm in intervals of 10 nm
[0099] Ordinate mode: absorbance [0100] Intergration: 1.0 nm [0101]
Scan speed: 483.8 nm/min
[0102] The yellowness index YI of the polymers was then calculated
from the UV/Vis spectrum according to the method of ASTM D
1925.
Size Exclusion Chromatography (SEC) Measurements:
Equipment:
[0103] Agilent 1100 Series degasser
[0104] Agilent 1100 Series Isocratic pump
[0105] Agilent 1100 Series Auto sampler
[0106] Agilent 1100 Series Column compartment
[0107] ODS Hypersil column
[0108] Personal computer with SEC data acquisition software
[0109] Analytical balance
[0110] Standard laboratory equipment and glass ware
[0111] Syringe 10 ml
[0112] SEC vials
Sample Preparation:
[0113] Weigh approximately 1 mg/mL of polymer and dissolve it in
dichloromethane. Shake for at least 10 minutes. Introduce liquid
into a SEC vial via a syringe with a filter tip to avoid solid
particles.
Instrument Method Configuration:
[0114] Column: ODS Hypersil column [0115] Temperature: 35.degree.
C. [0116] Data acquisition: Signal Wavelength 254 nm/peakwidth:
>0.1 min (2 s) [0117] Eluent: CH.sub.2Cl.sub.2 (100%), no
gradient elution [0118] Flow rate: 0.3 ml/min. [0119] Pressure
limits: from 4 bar to 170 bar [0120] Injection volume: 10.0 .mu.l
[0121] Total Run Time: 15.00 min. [0122] Internal Standard
correction: flowmarker=0.625 mL of toluene in 2.5 L CH2Cl2 [0123]
wavelength 254 nm [0124] ref. Position 4.97 min/max deviation
5%.
Small-Scale Melt Polymerization Experiments
[0125] Samples of isosorbide (IS) containing (homo/co/ter) polymers
were prepared in using the followings steps. Small-scale
polymerization reactions were carried out in glass tube reactors,
which had the same vacuum system. Before charging the monomers the
glass reactor tubes were soaked in 1M HCl for at least 24 hours to
remove any sodium present at the surface of the glass. After this
acid bath the glass tubes were rinsed using 18.2 MW (Milli-Q
quality) water for at least 5 times. According to the desired make
up of the polymer the batch reactor tubes were charged at ambient
temperature and pressure with 25.00 grams of solid BMSC and the
required number of grams of isosorbide, C.sub.36 diacid, and
Bisphenol-A (BPA). After this the reactor system was sealed shut,
the system was deoxygenated by briefly evacuating the reactors and
then introducing nitrogen. This process was repeated three times.
100 .mu.l of the catalyst solution (alpha catalyst solution: 0.5 M
aqueous sodium hydroxide and diluted to the required concentration
40 .mu.Eq) was added to each reactor as an aqueous solution.
[0126] The temperature of the reactor was maintained using a
heating mantle. The pressure over the reactor was controlled by a
nitrogen bleed into the vacuum pump downstream of the distillate
collection flasks and measured with a pressure gauge. The reactor
was brought to near atmospheric pressure and reaction time is
started at the same moment as the heaters are switched on. The
reactions were carried out according to the conditions in Table
below. In the below Table, "Tr" is the set point temperature of the
reactor; and "To" is the set point temperature of the overhead. The
vacuum system removed the methyl salicylate by-product, which was
condensed in condensers. The product was recovered by removing a
drain nut at the bottom of each reactor.
[0127] The standard reaction profile is below.
TABLE-US-00001 Time Remarks 0:00:00 T.sub.r reached 170.degree. C.;
T.sub.o reached 100.degree. C., pressure reached 100 kPa 0:06:00
Set stirrer to approximately 40 rpm 0:15:00 Set Tr to 230.degree.
C. 0:30:00 Set P at 50 kPa 0:50:00 Set Tr at 270.degree. C. and P
at <0.2 kPa 1:04:00 Open reactor under nitrogen flow and stop
reaction. Drain polymer from reactor.
Example 1
Sorbitol Spiking in IS-(Homo/Co/Ter)Polymers
[0128] Different amounts of sorbitol were added to reaction
mixtures to form IS-homopolymers, IS-copolymers, and IS-terpolymers
to evaluate the influence of sorbitol on the properties of these
polymers. The color properties were measured using UV/Vis
spectroscopy method described above. .sup.1H-NMR analysis was
performed on the prepared polymers and it was determined that
polymer color was not related to byproducts from using BMSC as the
carbonate source. In the reaction mixture, some molar percent of
isosorbide was replaced with sorbitol to simulate an isosorbide
with different amounts of sorbitol impurities. The reactions were
done on the melt polymerization unit with the standard reaction
profile with a molar ratio of 1.01.
TABLE-US-00002 GEPL.P-161/234129 Formulation Example Sorbitol
spiking Mw (PC) Mn (PC) PDI L* a* b* YI -- -- mol %/IS g/mol g/mol
-- -- -- -- -- Homopolymer WE 1 0.00 17628 7889 2.2 98.8 0.04 1.3
2.4 BMSC (101)/IS CE 1 0.10 17347 7827 2.2 97.9 -0.33 4.7 8.4
40.mu.Eq NaOH CE 2 0.30 11734 5366 2.2 96.2 -0.50 9.4 16.8 CE 3
0.50 14934 6345 2.4 94.6 -0.53 14.2 25.2 CE 4 1.00 15119 6858 2.2
93.9 -0.96 19.0 32.8 CE 5 5.00 NM NM NM 43.1 12.63 49.0 125.3
Terpolymer WE 2 0.00 20913 8559 2.4 99.7 0.10 0.3 0.6 BMSC (101)/
CE 6 0.05 19999 6284 2.4 99.3 -0.26 2.0 3.4 IS(80)/BPA(13)/C.sub.36
CE 7 0.10 15258 6560 2.3 98.9 -0.38 3.4 5.9 diacid(7) CE 8 0.15
16130 6916 2.3 98.3 -0.28 4.2 7.5 40.mu.Eq NaOH CE 9.1 0.20 15556
6742 2.3 97.7 -0.37 6.2 11.0
The color properties of both the homo- and ter-polymers are plotted
in FIGS. 1 (homopolymers) and 2 (terpolymers).
[0129] Copolymers were also prepared using IS, various comonomers,
two levels of sorbitol were spiked to the samples (i.e. none and
0.1 mol %). The properties of these copolymers are given in the
table below.
TABLE-US-00003 Formulation Mw (PC) Mn (PC) PDI L* a* b* YI -- --
g/mol g/mol -- -- -- -- -- WE 3 IS (50)/BPA(50) 19427 8666 2.2 99.6
-0.06 0.6 1.1 IS (50)/BPA(50) 16293 7117 2.3 99.7 -0.11 0.9 1.5 CE
9.2 IS (50)/BPA(50) + 17097 7648 2.2 98.4 -0.70 4.2 7.2 0.1 mol
%/IS sorbitol IS (50)/BPA(50) + 17429 7707 2.3 98.6 -0.46 4.6 8.1
0.1 mol %/IS sorbitol WE 4 IS (50)/Resorcinol(50) 14798 6559 2.3
95.5 0.05 3.9 7.3 IS (50)/Resorcinol(50) 14711 6520 2.3 98.9 -0.24
2.9 5.1 CE 10 IS (50)/Resorcinol(50) + 14422 6314 2.3 96.7 -0.99
11.1 19.1 0.1 mol %/IS sorbitol IS (50)/Resorcinol(50) + 13572 6013
2.3 97.8 -0.88 8.1 14.0 0.1 mol %/IS sorbitol WE 5
IS(93)/C36diacid(7) 26273 10704 2.5 99.6 -0.17 1.2 2.0
IS(93)/C36diacid(7) 27731 11193 2.5 99.1 -0.39 2.9 5.0 CE 11
IS(93)/C36diacid(7) + 27968 10841 2.6 98.1 -0.92 5.9 10.0 0.1 mol
%/IS sorbitol IS(93)/C36diacid(7) + 27314 10973 2.5 98.7 -0.46 4.2
7.3 0.1 mol %/IS sorbitol WE 6 IS(70)/C36diol(30) 16248 6599 2.5
96.2 0.04 1.2 2.3 IS(70)/C36diol(30) 13368 5370 2.5 95.3 0.05 1.7
3.3 CE 12 IS(70)/C36diol(30) + 14118 6114 2.3 95.8 -0.07 2.3 4.2
0.1 mol %/IS sorbitol IS(70)/C36diol(30) + 14341 6406 2.2 94.1 0.13
2.8 5.4 0.1 mol %/IS sorbitol
[0130] As can be seen in the tables above and in FIGS. 1 and 2, the
color properties of the polymer deteriorates as the amount of
sorbitol in the reaction mixture increases. Sorbitol has an adverse
effect on the color of the different polymer formulations when
spiked at levels at or above 0.1 mole % relative to the isosorbide
content of the formulation. There does not appear to be branching
with added sorbitol. Furthermore the molecular weight decreases
with the increase of the amount of sorbitol but there does not
appear to be significant change in the by-product formation, except
for the increase in the content of IS--OH and decrease in the
content of IS-SalOH for the homopolymer formulation.
[0131] As demonstrated, the addition of sorbitol to the
homopolymer, copolymer, and terpolymer reaction mixture
formulations results in a yellowish-brown coloration of the
polymer. Therefore it has been demonstrated that the amount of
sorbitol that can be tolerated in isosorbide as an impurity should
be limited (e.g. to an amount less than 0.10 mol %, more preferably
less than 0.05 mol %) because sorbitol has a negative effect on
polymer color quality.
[0132] The polymer prepared in Working Example 1 and Comparative
Examples 1 to 4 was also analyzed using .sup.1H-NMR spectroscopy to
detect the sorbitol-derived color body and to calculate the
concentration of the color body relative to that of isosorbide
based on the relative areas of the color body peak and three
isosorbide peaks according to the .sup.1H-NMR analysis procedure
described above. FIG. 6A shows a graph comparing the YI of the
polymer samples to the quantified concentration of the
sorbitol-derived color body and to the amount of sorbitol spiked to
initial reaction mixtures. FIG. 6B shows a graph comparing the YI
of the polymer samples to the quantified concentration of the
sorbitol-derived color body.
Example 2
Dissolution and Precipitation of Polymer to Remove Low Mw Color
Bodies
[0133] In this example the polymer formed in Comparative Example 5
above was treated to reduce the concentration of the
sorbitol-derived color body. The treatment step included the
dissolution and precipitation of the polymer from solution. The
dissolution and precipitation method was used to separate the
polymer from the low molecular weight color body species found as
"residuals" in the polymer samples. In this method, sample
solutions were prepared by dissolving 0.5 g of the polymer sample
(e.g. from polymerization spiked with sorbitol) in 5 ml of
chloroform (5 mass/volume % solution). After dissolution, 10 ml of
methanol were added to the sample solution in order to precipitate
the polymer. The precipitated polymer and the solution containing
the color body were then separated by filtration.
[0134] Each solution (e.g. before and after precipitation) and the
precipitated polymer, were analyzed using .sup.1H-NMR and UV-Vis
measurements to determine if the color body was present or absent.
See FIGS. 8 to 10. FIG. 8 shows the .sup.1H-NMR spectra of the
solution after dissolution of the polymer and prior to
precipitation containing the peak at about 2.55 ppm. FIG. 9 shows
that the .sup.1H-NMR peak at about 2.55 ppm assigned to the color
body is no longer detectable in the spectra of the precipitated
polymers after dissolution/precipitation. FIG. 10 shows that the
peak at about 2.55 ppm is observed in the solution spectra of the
extracted residual species. In the UV-Vis measurements (see FIG. 7)
it was found that the color was removed from the polymer by the
dissolution/precipitation process. This example demonstrates that
the sorbitol-derived color body can be freely removed from the
polymer.
[0135] Applicants note that another peak located at about 1.92 ppm
in the .sup.1H-NMR spectra is present in pretreated polymer and is
also removed after the dissolution/precipitation treatment step.
This peak is also believed to be associated with the
sorbitol-derived color body and may be related to a free --OH
feature of the color body. Because this peak is relatively broad
and featureless single peak little information can be ascertained
from it. Also, broad --OH peaks tend to be less useful for analysis
because they may shift or otherwise alter due to hydrogen-bonding
interactions and solvent interactions, among other interactions.
Therefore the peak at about 2.55 ppm is believed to be more useful
for analysis of the sorbitol-derived color body.
Example 3
Polymerization Using a Plug Flow Reactor/Flash
Devolatilization/Reactive Extruder Hybrid System Shown
Schematically in FIG. 3
[0136] A terpolymer of isosorbide, BPA and C.sub.36 diacid was made
in a 80/13/7 (mole %) composition. In this system a stirred tank
101 is charged at ambient temperature and pressure with the
isosorbide (38,914 g) and BPA (9,879 g) diol and C36 diacid (13,210
g) diacid monomers, and solid BMSC (112,144 g). The standard
BMSC/(diol/diacid) monomer molar ratio is 1.02. After loading the
reactor the catalyst solution (sodium hydroxide aqueous solution in
an amount of 225 micromoles per total mole diol+diacid) is added
directly into the stirred tank 101. After this the monomer mix tank
101 is sealed shut. The system is deoxygenated by briefly
evacuating the monomer mix tank 101 followed by introducing
nitrogen. This process is repeated three times. Then, in order to
melt the diaryl carbonate and prepare the oligomer, the pressure is
set to 800 mbar and the temperature is increased to about
175.degree. C. The liquid mixture is continuously stirred and left
to react until an exothermic peak is observed in the stirred tank
101.
[0137] Using a piston pump 103, the oligomer is then fed to a
pre-heater 104. The oligomer is mixed in a small 10 cm intensive
mixing zone 105. The oligomer is than pumped through the plug flow
reactor 106. The PFR 106 temperatures typically range between 150
and 230.degree. C., the residence time in the plug flow reactor 106
varies between 2 and 10 minutes. The pressures typically range
between about 400 and 600 kPa, in order to ensure that no vapor
phase is formed. The oligomer is then fed to the pre-heater 110.
The temperature in this pre-heater 110 ranges between 150 and
240.degree. C. The pressure is kept below 50 kPA in order to start
evaporation of methyl Salicylate (MS). The concentration of MS
remaining in the liquid phase (oligomer) varies between about 10
and 20% (w/w). Then, the oligomer mixture is fed through the
distributor 112 to the flash vessel 113. In the flash vessel,
additional MS is removed and molecular weight is further increased.
In the flash vessel the pressure typically varies between 5 and 30
kPa, and the temperature is kept between 150 and 240.degree. C.
[0138] The MS evaporated leaves the flash vessel and condenses in
condenser 115. It is collected as a liquid in a storage vessel. The
oligomer is pumped out of the flash vessel to the extruder 116
using the gear pump 114. The amount of MS in this oligomer varies
between 0.5 and 20% (w/w), depending on the temperature and
pressure settings of the flash vessel.
[0139] The extruder used is a ZSK 25 extruder. The oligomer is fed
to the extruder at a rate between 5 and 25 kg/h. The screw speed
varies between 300 and 500 rpm. The barrels of the extruder are set
at 260.degree. C., the die head at 270.degree. C. The ZSK 25 (type)
extruder is equipped with a high vacuum system to further remove
the methyl Salicylate formed as a byproduct in the polycondensation
reaction. Polycarbonate is removed from the extruder. The set
points of this process are shown in the table below.
TABLE-US-00004 # UOM Run 1 Run 2 Run 3 Formulation vessel 101 Ratio
[--] 1.02 1.02 1.016 Catalyst Mol/Mol diol 7.5E-05 6.0E-06 7.5E-05
Oil temp setpoint [.degree. C.] 150 150 150 Pressure [--] ATM ATM
ATM Agitator speed [rpm] 400 400 400 Piston pump 103 Flow N-210
[kg/h] 25 25 25 Preheater reactor 104 Oil temp setpoint [.degree.
C.] 160 160 160 SMXL Reactor 106 Oil temp setpoint [.degree. C.]
160 160 160 Pressure setpoint kPa 400 400 400 Preheater devol
vessel 110 Oil temp setpoint [.degree. C.] 200 200 200 Pressure
setpoint kPa 200 200 200 Devol vessel 113 Oil temp setpoint
[.degree. C.] 190 190 190 Pressure setpoint kPa 5 5 5 Devol
Extruder 116 Screw speed [rpm] 300 300 300 Barrel temp. setpoint
[.degree. C.] 260 260 260 Die temp. setpoint [.degree. C.] 270 270
270 Pressure setpoint kPa 0.1 0.1 0.1
[0140] The influence of sorbitol on the final polymer color is
shown in Runs 1-3. In these runs 3 different isosorbides were used
with varying sorbitol concentrations. These concentrations are
shown in Table 2.
TABLE-US-00005 Isosorbide [sorbitol] Run (wt %) 1 N.D. 2 0.1 3
0.1
[0141] These runs were performed using the plug flow reactor/flash
devolatilization/reactive extruder hybrid system described with
regard to FIG. 3. In doing so the resulting product was analyzed on
color and the results are shown in the tables below and in FIG.
4.
[0142] The color of the produced polycarbonate pellets was measured
using a XRITE TELEFLASH 130 instrument. A standard light source D65
(neutral daylight, 6500 Kelvin) with a 10.degree. observation angle
was used to generate L, a*, and b* values. The pellets were placed
in a glass Petri-dish with a diameter of 15 cm and a height of 4
cm. The dish was completely filled with pellets, excess pellets
were removed, and the surface pellets gently compressed. Next, the
filled dish was placed at a fixed distance and angle from the
instrument light source and detector, as determined by the
instrumental configuration/geometry. Each sample was measured three
times in 3 different dish positions whereby the dish is rotated
between each position. The average results are shown in the table
below. Run numbers are in the left column.
TABLE-US-00006 YI L* a* b* 1 31.7 82.0 1.78 20.2 2 41.9 69.6 4.32
24.3 3 43.9 69.1 5.84 25.5
The color of the produced polycarbonate pellets was also measured
using UV-Vis spectroscopy as described above. These values are
included in the table below.
TABLE-US-00007 Isosorbide Solution color of [sorbitol] terpolymer:
(untreated) Run (wt %) L a b YI 1 N.D. 99.7 -0.1 0.5 0.8 2 0.1 99.3
-0.2 1.7 2.9 3 0.1 98.8 -0.3 2.6 4.6
[0143] These runs demonstrate that the use of isosorbide containing
no detectable amount of sorbitol provides the best color properties
of the final polymer. L* is higher, and YI, b*, and a* are lower
compared to the Isosorbide containing 0.1 wt % sorbitol. Sorbitol
reacts to form a sorbitol-derived color body during the
polymerization.
[0144] In a next step, the polymers prepared in Runs 1 to 3 were
treated to reduce the concentration of the sorbitol-derived color
body. In this step the polymers were dissolved and precipitated
from solution. The dissolution and precipitation method was used to
separate the polymer from the sorbitol-derived color body species
found as "residuals" in the polymer samples. In this step, sample
solutions were prepared by dissolving 0.5 g of the polymer sample
from the respective run in 5 ml of chloroform (5 mass/volume %
solution). After dissolution, 10 ml of methanol were added to the
sample solution in order to precipitate the polymer. The
precipitated polymer and the solution containing the color body
were then separated by filtration. The properties of the
precipitated polymer are contained in the table below. Comparing
the precipitated polymers' properties to the starting polymers'
properties, one can see that the color of the polymers are
significantly enhanced.
TABLE-US-00008 Solution color Polymer of terpolymer: [sorbitol]
after precipitation Run (wt %) L a b YI 1 N.D. 99.7 0 0.1 0.3 2 0.1
99.6 0 0.2 0.3 3 0.1 100 0 0 0
* * * * *