Note: Descriptions are shown in the official language in which they were submitted.
2083326
RD-21 1 57
PROCESS FOR PREPARI~b~
TE~a~TE12 THE~MOPL~STIC POI~YM~S
BACKGROUND OF THE INVENTION
Technical Field
The present invention relates generally to making
functionalized thermoplastic polymers often used in preparing
solvent resistant polymer blends and, more particularly, to a method
10 for preparing anhydride-terminated polycarbonates by a melt
process.
Description of the Prior Art
Anhydride-terminated (sometimes referred to as
anhydride-capped or anhydride-functionalized) polycarbonates have
been synthesized in solution by esterificatio-n of hydroxy-terminated
polycarbonates with trimellitic anhydride acid chloride. Such
hydroxy-terminated polycarbonates are prepared by interfacial
phosgenation of dihydroxyaromatic compounds such as 2,2-bis(4-
hydroxyphenyl)propane, more commonly known as bisphenol A (BPA),
using the monotetrahydropyranyl ether of BPA as a chainstopper,
followed by acid hydrolysis to cleave the tetrahydropyranyl
protecting group. See, for example, Hathaway, U.S. Patents
4,736,013 and 4,732,934, both assigned to assignee of the present
invention.
A latently reactive t-butoxycarbonyl (t-BOC) protected
amino-terminated polycarbonate can also be interfacially prepared
by phosgenation of BPA in the presence of an expensive, non- ` `
30 commercially available chainstopper, namely t-BOC tyramine
according to the process described by Gambale in U.S. patent
application Serial No. 07/562,354, assigned to assignee of the
. : :
~ 2083326
RD-21 1 57
present invention. These thermally unstable protected amino-
terminated polycarbonates are subsequently converted to form an
anhydride-functionalized polycarbonate by extrusion with 1,2,4,5-
benzenetetracarboxylic dianhydride, a relatively costly compound.
The solution chemistry processes used to prepare these
functionalized polycarbonates are less than optimal due to the
requirement of multiple reaction steps and the need for costly
chainstoppers. Additionally, such types of solution chemistry are
generally accomplished using an organic solvent such as methylene
chloride, which requires additional environmental attention.
Anhydride-functionalized polycarbonates synthesized -
according to the above methods are often used to form solvent
resistant polymer blends of thermoplastics with amorphous -
polyamides prepared from a mixture of a diamine such as
hexamethylene diamine and isophthalic and/or terephthalic acids and
sold under such tradenames as SELAR PA of E. I. DuPont Company.
Fox, U.S. Patent 3,153,008, assigned to assignee of the
present invention provides a simple source of hydroxy-terminated
BPA polycarbonates (PC-OH) using a melt process. Fox provides a
method for preparing hydroxy-terminated polycarbonates with up to
80% hydroxy end groups by melt reacting bisphenol A and diphenyl
carbonate (DPC) using a catalyst.
Sivavec, U.S. Patent 4,988,775, assigned to assignee of
the present invention, discloses a melt extrusion process for
preparing dicarboxylate capped poiyphenylene ether whereby
hydroxy-terminated polyphenylene ether undergoes
transesterification with a trimellitic acid anhydride salicylate
ester.
There thus remains a need for an improved process for ~
3 0 praparing anhydride-functionalized thermoplastic polymers having - ~-
recurring carbonate units in the main chain which avoids the need
for solution chemistry, multiple steps and expensive reactants. -
.~ .,,, - . ...
'' ,'',
' , ~
2083326
- 3 -
RD-21 1 57
SUMMARY OF THE INVENTION
The need for an improved process for preparing
anhydride-terminated thermoplastic polymers having recurring
5 carbonate units in the main chain is satisfied in accordance with the
broadest principles of the present invention comprising the step of:
melt blending in a solvent-free environment a hydroxy-terminated
thermoplastic polymer having recurring carbonate units in the main
chain, a trimellitic anhydride salicylate ester and a catalyst to form
10 a thermoplastic polymer having recurring carbonate units in the
main chain and having functionalized end groups of the formula
~C ~
c
o
A preferred embodiment according to the inventive
method is represented by the following formula - .
~II) PC-OH + TMA-PSE ~ Catalyst
Extrusion
PC-O : ~
wherein PC-OH is a hydroxy-terminated polycarbonate and TMA-PSE :-
is trimellitic anhydride phenyl salicylate ester. The reaction occurs
. - .~ ~ ,~ . . . .
. ..
-- 4 20~3326'
RD-21 1 57
preferably using an extruder in a solvent-free environment by way of
a transesterification process.
It is therefore an object of the present invention to
provide an improved method for preparing anhydride-terminated or
functionalized thermoplastic polymers having recurring carbonate
units in the main chain which are capable of chamical reaction with
polyamides to provide a compatible blend which may be molded into
forms having excellent tensile strength, impact strength and solvent
resistance.
One advantage of the present invention includes the
ability to prepare the desired anhydride-terminated thermoplastic
polymers by a melt process and thus eliminate the need for solution
chemistry.
A further advantage provided by the inventive method
includes the ability to use readily available, low cost starting
materials and catalysts in the improved process and, thus, avoid
lengthy multi-step procedures for making starting materials and
reactant monomers such as chainstoppers.
DETAILED DESCRIPTION OF THE INVENTION
A wide variety of thermoplastic polymers which have
recurring carbonate units in the main chain may be anhydride-
terminated after being hydroxy-terminated according to the present
invention. The number of carbonate units present depends in part
upon the end use of the functionalized polymer.
The thermoplastic polymer having recurring carbonate
units in the main chain has functionalized end groups according to
formula I above.
3 0 The functionalized thermoplastic polymer having
recurring carbonate units in the main chain may be a
homopolycarbonate (i.e., prepared from a single dihydroxyaromatic
compound) or copolycarbonate (i.e., prepared from two or more ~
-.
~' ' '~ .',
- 5 - 2 0~ 33 2 6
RD-21 1 57
dihydroxyaromatic compounds). Such polymers are well-known in
the art and generally comprise structural units of the formula
o
(111) - R2--O--C--O--
in which R2 is the divalent residue of one or more dihydric phenols.
Suitable aromatic polycarbonates of the present invention include
those which contain structural units of the formula
(IV) ~1~-1l--
in which R3 and R4 are hydrogen, halogen, lower alkyl, phenyl or part
of a cycloalkylidene ring or substituted cycloalkylidene ring such as
found in cycloalkylidene bisphenols, x1 and X2 are lower alkyl, lower
15 alkenyl or halo and m and n are 0 or integers from 1 to the maximum
number of replaceable hydrogen atoms. The terms "lower alkyl" and
"lower alkenyl" as used herein refer to alkyl and alkenyl groups
having about 1 to about 6 carbon atoms. An alternative embodiment
to formula IV is a spirobisindane bisphenol, such as, for example, a
2 0 tetramethylspirobisindane bisphenol. The preferred polycarbonates
are bisphenol A polycarbonates.
Also, within the scope of the present invention are flame
retardant polycarbonates formed from halogen-containing
polycarbonate oligomers. Such polycarbonates are usually prepared
2 5 with substituted dihydric phenols, e.g., 2,2-bis(3,5-dibromo-4-
hydroxyphenyl)propane, commonly referred to as
tetrabromobisphenol A.
Polycarbonates may be prepared by several well-known
methods. For example, preparation may be accomplished by reacting
30 a dihydric phenol such as bisphenol A with a carbonate precursor. A
~. . . ~ - .
. . . . . . , , . - . .- ... ~ .
-- 6 20~332~
RD-21157
wide variety of other dihydric phenols may be used in the present
invention; many are disclosed in U.S. Patents 2,999,835, 3,028,365,
3,334,154, 4,190,618 and 3,160,121, all incorporated herein by
reference. Many carbonate precursors may be used; they are
5 typically either a carbonyl halide, a carbonate ester or a
haloformate. Exemplary carbonate precursors are described in U.S.
Patent 4,190,681.
Specific methods for the preparation of polycarbonates
are described in U.S. Patent 3,989,672, also incorporated herein by
1 0 reference. They may also be prepared by transesterification
processes well-known in the art and described, for example, in Fox's
U.S. Patent 3,153,008, incorporated herein by reference. Such a
preparation method is particularly preferred in the present invention
because the resulting polymers are substantially hydroxy-
1 5 terminated, as described below and, as such, eliminate the need for -~ -
a further reaction step to achieve the necessary hydroxy-
termination of the polycarbonates for use in the present inventive
method.
The thermoplastic polymer containing recurring
20 carbonate units may comprise a copolymer. "Copolymer~ as used
herein (and in contrast to ~copolycarbonaten) is meant to include
polymeric materials containing carbonate structural units as
described above along with at least one additional type of structural
unit, e.g., ester units, siloxane units, ether units and the like. The
25 selection of a particular copolymer will depend on the properties
desired for specific products made with compositions of the present
invention .
Exemplary copolymers falling within the scope of the
present invention are the copolyestercarbonate resins which
30 generally contain recurring carbonate groups and carboxylate groups.
These polymers are well-known in the art and are generally prepared - -
by reacting
(a) a carbonate precursor such as those described above;
2083326
RD-21 1 57
(b) at least one dihydric phenol as described above and;
(c) at least one difunctional carboxylic acid or reactive
derivative thereof. Exemplary copolyestercarbonate compositions
particularly suitable for the present invention are described in U.S.
5 Patent 4,487,896, incorporated herein by reference. These
materials exhibit excellent processability characteristics in
molding or extrusion applications. Specific examples of
copolyestercarbonates include those prepared from a mixture of
bisphenol A, phosgene and iso- and terephthalic acids or reactive
10 derivatives thereof, e.g., isophthaloyl chloride and terephthaloyl
chloride. The molar concentration of ester units in such polymers
may vary widely with the proviso that recurring carbonate units as
defined above are present in the main chain of the polymer.
Another suitable class of thermoplastic copolymers
15 which may be functionalized according to the present invention are
the organopolysiloxane-polycarbonate block copolymers, such as
those described in U.S. Patent 3,189,662, issued to the assignee of
the present application and incorporated by reference herein. Such
copolymers generally comprise diorganosiloxy blocks consisting
20 essentially of silicon atoms connected to each other by silicon-
oxygen-silicon linkage wherein each of the silicon atoms has two
organic substituents attached thereto; and polycarbonate blocks
which may be formed as described above.
Generally speaking, the polymers which are to be
25 functionalized with end groups according to the present invention
have intrinsic viscosities between about 0.3 and about 1.0 dl./g., as -
determined in chloroform at 25C. Factors determining the
selection of a particular intrinsic viscosity include the desired
physical properties of products formed from these polymers, as well
30 as the processing conditions to which the polymers will be
subjected.
The thermoplastic polymers to be functionalized
pursuant to the inventive method of the present invention should be ~
.,,,,~ . ..
208332~
- 8 -
RD-21 1 57
hydroxy-terminated prior to reaction with the functionalizing agent
Hydroxy-terminated thermoplastic polymers as described above are
referred to herein by the abbreviation PC-OH. Methods of forming
hydroxy-terminated polymers are well-known in the art. For
5 example, the polymers may be hydrolyzed with an alkali metal
hydroxy compound such as sodium hydroxide or potassium hydroxide
in an organic solvent. The degree of hydroxy termination is
generally high because the aromatic carbonate units are very
amenable to hydrolytic action. Typically, at least 80% of the
10 carbonate sites on the homopolymer or copolymer become hydroxy-
terminated by any of the methods discussed above.
Hydroxy-terminated polycarbonates may also be prepared
via ester interchange during the melt polymerization of a dihydric
phenol with diphenyl carbonate, as described in U.S. Patent
15 3, 1 53,008, sometimes referred to as transesterification.
Accordingly, the invention in one of its aspects is
directed to a method for preparing anhydride-capped polycarbonates
by melt blending in the absence of solvent, with application of
vacuum, at least one hydroxy-terminated thermoplastic polymer
20 (PC-OH) with at least one trimellitic anhydride salicylate ester of
the formula
O
R50C o o - ~.
11 ll
g~O-C~C\
Il .
O
25 wherein RS is C1.6 alkyl or more often a C6 10 aromatic hydrocarbon
radical such as phenyl, tolyl, xylyl, 1-naphthyl or 2-naphthyl, with
phenyl being preferred. Thus, the most preferred trimellitic
.
"' ' "
~ 9 2~332~;
RD-21 1 57
anhydride ester is the 4-(phenyl salicylate), which is also
frequently referred to as 4-(o-carbophenoxyphenyl) ester.
Trimellitic anhydride salicylate esters referred to
herein as the functionalizing agent may be prepared by conventional
5 methods. A particularly convenient method is the reaction of
trimellitic anhydride acid chloride (TAAC) with an ester of salicylic
acid, most preferably phenyl salicylate, forming a trimellitic
anhydride phenyl salicylate ester.
Suitable catalysts as referred to in formuia ll include
10 metal salts of the formulas MX, M2CO3, MOH, MOR and MOCOR
wherein M is sodium, lithium or potassium, X is fluoride, chloride,
bromide or iodide and R is selected from C1-C20 alkyl and aryl
groups. Also included are such salts as LiBH4, NaBH4 and LiAlH4.
Alternative catalysts may be selected from ammonium
salts of the formula ~ -
R7 ~ ::
( V I ) R6 _N~
R~
wherein R6, R7, R8 and R9 are independently selected from C1 20
20 alkyl and aryl groups and Z is halide, BH4, B(C6Hs)4 or OH.
Additionally, suitable catalysts may be selected from
non-volatile amines which, by way of example, include: 4-
dimethylaminopyridine (DMAP); imidazole and benzimidazole; 2,4-
diazabicyclo[2.2.2]octane (DABCO); 1,5-diazabicyclo[4.3.0]undec-7- ~ ~-
25 ene(DBU); and mixtures made thereof.
When the PC-OH is prepared by interfacial phosgenation,
the PC-OH product is believed to contain residual amines or basic
compounds which catalyze the capping reaction. Thus, even a trace
amount of such amines or basic compounds is sufficient to catalyze
30 the transesterification, thereby eliminating the need for an
additional catalyst such as described above.
~ ..
' ~
::
20~332fi
RD-21 1 57
The amount of catalyst should not exceed 4,000 ppm. of
the mixture, since excess catalyst may decrease the molecular
weight of the polycarbonate. Preferably, the amount of catalyst
should be 50-1,000 ppm.
The melt blending operation may be performed in
conventional melt blending apparatus of both the batch and
continuous type. It is often preferably conducted continuously in an
extruder, by reason of the excellent properties of extruded materials
and the availability of extruders in commercial polymer processing
facilities. Typical conditions include temperatures in the range of
about 225-350C, preferably about 275-325C. The proportion of
trimellitic anhydride salicylate ester employed is not critical and
will depend on the degree of anhydride capping desired. It is most
often about 2-5% by weight but may be as high as about 10% by
1 5 weight based on polymer.
It is preferred that the blending be conducted with
application of vacuum. In general, blending processes involving
pressures below about 20 torr for at least a portion of the process
are desirable. Extr~sion processes of this type may be conducted by
means of vacuum venting, whereby a vacuum is drawn on at least one
vent in the extruder.
The inventive method for preparation of the anhydride-
capped polycarbonate is illustrated by the following Table I and
Example 1. All parts are by weight. The polycarbonates employed
were prepared according to both known melt processes and
interfacial phosgenation processes as described above. Molecular
weights are weight average and were determined by gel permeation
chromatography relative to polystyrene.
3 0 Examo~
For samples 1-9 in Table I below, melt (M) or
interfacially (IF) prepared hydroxy-terminated bisphenol A
...
`
. .
-- 11 2083326
R D-2 1 1 57
polycarbonate, TMA-PSE and an amount of catalyst, if any, were
weighed in a 0.5 gallon glass jar and tumble mixed for 15 minutes.
The contents were then extruded on a 20 ml. Welding Engineers-Twin
Screw extruder. The zones were heated from throat to die at 250,
5 375, 4 x 525 and 530F. Vacuum was applied to extrusions of
samples 1, 2 and 3. The extrudate was cooled in water, chopped and
dried at 120C for three hours. Pellets of the capped product were
dissolved in chloroform and reprecipitated into acetone for infrared
analysis to determine the percent of capping (by measuring residual
10 % OH) and to confirm the anhydride functionalization by NMR.
2083326
.~ O ~ tD C" N N O <D
N~
C`J OOOOOOO
~ O O
N E 3
CC ' U) U~ . -
.~ o o g o o o o g o
~ ~ ~ o
S ~ ~ ` N
a ~ ", i i N
~ ~ ~ 3 ~, ~
cn a~ . : .:
u.~ ~
3 ~ ~ c-~ N N N
~ N 1~ ~ D ^
I I_ _ _ O o o o o O O O O
oo . . . _ _ _ _ _ _ ooo =--
_ _ o o o o o ^ ^
tL a~ o o o ~ -- C'~
_ E IL ~L S S S S ~ ~ 11 U ~ Q
, 333 x
~ ~ S ~
_ N ~ :
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RD-21 1 57
Sample 2 from Table I illustrates that a product with
80% anhydride capping was obtained when interfacially prepared PC-
OH was reacted with 7% by weight TMA-PSE in the absence of added
or additional catalyst.
Sample 3 from Table I illustrates that a product with
69% capping was obtained when the same interfacially prepared PC-
OH as in sample 2 was reacted with 3.5% by weight TMA-PSE in the
absence of added catalyst.
It is believed that the difference in the degree of
functionalization of the melt prepared PC-OH of sample 1 and the
interfacially preparèd PC-OH of samples 2 and 3 can be explained by
the fact that the interfacially prepared PC-OH may contain residual
amines or basic compounds which catalyze the transesterification
as discussed above. The melt polymerized PC-OH contains no such
catalyst. When melt PC-OH was extruded with TMA-PSE in the
presence of a basic catalyst (i.e., sodium stearate, imidazole or -
DABCO) at 200-1,000 ppm. by weight of PC-OH, significant capping -
of the polycarbonate with anhydrides occurred (see samples 4-9).
Spectroscopic examination of the extruded pellets of
Samples 7-9 showed little or no TMA-PSE remaining.
Additional samples not shown on Table I were prepared -
with higher concentrations of TMA-PSE. These samples showed
residual TMA-PSE which affected the properties of the subsequent
capped PC-polyamide blends. This effect may be avoided by
2 5 repr0cipitating the polymer prior to compatibilizing with the
polyamide to remove the excess TMA-PSE, or using a smaller amount
of TMA-PSE, which preferably should not exceed 10% by weight of
the melt blend components.
,
30 Examel~ 2
The capped polycarbonates (40 parts by weight) of
samples 1-9 (in samples 11-12, redissolved in chloroform and
.' . '
. .
- ~ -
: .
- 14 - 208332~
RD-21 1 57
reprecipitated into acetone), a polyamide (SELAR PA - 40 parts) and
an impact modifier known as Acryloid KM-653, a product of Rohm
and Haas Company (20 parts) were weighed in a 0.5 gallon glass jar
and tumble mixed for 15 minutes followed by extrusion on a Welding
5 Engineers-20 mm. twin-screw extruder with zone temperatures
from throat to die of 250, 375, 4 x 510 and 525F with vacuum
venting. The extrudate was cooled in water, chopped and dried at
120C for three hours. Izod bars were molded on a 15 ton Boy type
injection molder at 285C. The bars were notched and equilibrated
10 under a 50% humidity atmosphere for 24 hours.
The compositions and properties of the blends of some of
the anhydride-functionalized polycarbonate samples of Table I with
polyamides are shown in Table ll below.
. .. -
.
:,
208332~
c q~ ~ .
E ~ Z
_ Co~
_.
0~-- ~ D CDF~ O O
Cl~ m ~ u~ o ~ o a~ D ~ F~ o
~D ~ F~ CD 10 N ~` O O 0~
,Om c~ cO 0, co ce~ co 0, co co ~q
' .,~
o ~ . ~ N 117a~~D O
O I~ N CO O O~ F~~ CD ~t
E ~ ~ ~ o o
.Q _ C~l ~r` 1~ F~In O F~ O O>
g Cc~ ~ O N ~ t ~ O
O Q m C~,l N N N N _ NN N N
~3 ~ ~
_ C ~ N o~ a~ o F U) , _
0 ~ _ CD O U~ N ~ I~
~ _ ~ ~ ~ 0 ~
E o ~ ~ ---- ~ .
~ ~ ''.`
O ~ N C~l ~F~ .C .~
~ E
~ _ C~l F~ ~ 10 ~ O C~ ~ . `: .
~ _ _ _ _ _ _ _ _ _ C~l _
, " '.` ':
'. ~ ''
' '' ~`'
,-- - 16 - 20~3326
RD-21 1 57
Blends using reprecipitated polycarbonate or pellets
functionalized with TMA-PSE (samples 11, 12, 17, 18 and 19)
showed no delamination (peeling) and had a desirable ductile quality.
However, where there was a residual amount of TMA-PSE, the TMA-
5 PSE competed with PC-TAAC for the amine end group of the
polyamide and thereby reduced the copolymer level and hence
affected the compatibilization of the two phases. Samples 14, 15
and 16 are believed to show the effect of residual TMA-PSE. Sample
13 is a control blend using unfunctionalized polycarbonate giving
10 brittle parts with severe delamination. The impact modifier KM-653
was more effective in improving impact modification when used in
pellet form than when used in powdered form (compare samples 11
with 12 and 19 with 20).
Efficient melt functionalization of hydroxy-terminated
15 polycarbonates and subsequent blend compatibilization has been
achieved by the present invention, which is not restricted to the
examples shown above regarding the use of other catalysts,
polyamides and impact modifiers.
While the invention has been described in terms of the
20 preferred embodiments, those skilled in the art will recognize that
the specific configurations, steps and parameters may be varied in
the practice of the invention by those skilled in the art without
departing from the spirit of the invention, the scope of which is
defined by the appended claims.
