Note: Descriptions are shown in the official language in which they were submitted.
~ CL~
This invention is di.rected to an interfacial polymerizatio~
process for preparing high molecular ~7eight aromatic polycarbon-
ates which comprises reacting under interfacial polycarbonate-
forming conditions a dihydric phenol and a carbonate precursor
in the presence of a catalytic amount of a substituted py~idine
or a salt of a substituted pyridine.
BACKGROUND OF THE INVENTION
Polycarbonates are well known thermoplastic materials
finding a wide range of uses, particularly for injection molding
applications and as glazing sheet for replacement of window
glass. The interfacial polymerization technique, which is one of
the methods employed in preparing a polycarbonate, involves
reactin~ a dihydric phenol and a carbonate precursor in the
presence of an aqueous caustic solution containing an alkali or
alkaline earth-metal hydroxide, and an inert organic solvent
medlum which is a solvent for the polycarbonate as it is formed.
While the interfacial polymerization process is generally effec-
tive in producing polycarbonates, it does, in general, suffer
from two disadvantages. Firstly, the rate of reaction is
relatively slow. Secondly, there is a general difficulty in pro-
ducing high molecular weight aromatic polycarbonates, i.e., those
having a weight average molecular weight of about 15,000 to
greater. Many techniques, such as those employing ultrasonic
waves during the reaction, have been employed to remedy these two
disadvantages. These techniques have not always proved to be
entirely effective and involve the use of cumbersome and expen-
sive equipment. It is advantageous economically to speed up the
reaction and to produce high molecular weigilt aromatic polycarbon-
ates without having to employ extra equipment or more severe
reaction conditions. One such method is the use o~ catalysts in
-- 1 --
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~L~6~ 3~
the interfacial polymerization process.
However, there is generally rela~ively little known about
effective catalysis of polycarbonate reactions. The prior art
discloses that certain compounds such as tertiary and quaternary
5 amines and their salts (U.S. Pat. 3,275,601), guanidine compounds
(U.S. Pat. 3,763,099), and ammonia and ammonium compounds (U.S.
Pat. 4,055,544) are effective catalysts for the interfacial poly-
merization process for producing polycarbonates. However, the
prior art also teaches that certain organic nitrogen compounds
function as molecular weight regulators or chain terminators in
the polycarbonate reactions. Thus, the afore-mentioned U.S. Pat.
3,275,601 discloses that aniline and methyl aniline function as
chain terminators in the polycarbonate reaction, while U~S. Pat.
4,001,184 discloses that primary and secondary amines are
effective molecular weight regulators. Furthermore, U.S. Pat.
4,111,910 teaches that ammonia, ammonium compounds, primary
amines, and secondary amines function as chain terminators in -the
formation of polycarbonates via the interfacial polymerization
process, and U.S. Pat 3,223,678 teaches that monoethanolamine
and morpholine act to break the polycarbonate chain thereby re-
sulting in lower molecu~ar weight polycarbonates.
DESCRIPTION OF THE INVENTION
This invention is directed to an interfacial pol~merization
process ~or producing high molecular weight aromatic carbonate
polymers wherein a dihydric phenol is reacted with a carbonate
precursor in the presence of an aqueous caustic solution con-
taining an alkali metal or alkaline earth metal hydroxide and a
catalyst which is a substltuted pyridine or a salt of a substi-
tuted pyridine.
-~ 8CL-3~14
The reaction of a dihydric phenol such as 2,2-bis~4-hydro~y-
phenyl)propane with a carbonate precursor such as phosgene results
in a high molecular weight aromatic polycarbonate polymer consist-
ing of dihydric phenol derived units bonded ~o one another through
carbonate linkages. The reaction is carried out in the presence
of an aqueous caustic solution containing the alkali and alkaline
earth metal hydroxide as acid acceptors and an inert organic sol-
vent medium which is a solvent for the polycarbonate as it is
formed. Generally, a molecular weight regulator is also present
to control the molecular ~eight of the polycarbonate polymer. In
the process of the present invention, a substituted pyridine is
present and acts as an effective catalyst to-speed up the reaction
between the carbonate precursor and the dihydric phenol.
The high molecular weight aromatic carbonate polymers pro-
duced in accordance with the practice of this invention include
carbonate homopolymers of dihydric phenols or carbonate copoly-
mers of two or more different dihydric phenols. Additionally,
the production of high molecular weight thermoplastic randomly
branched polycarbonates and copolyester-polycarbonates are in-
cluded within the scope of this invention. The randomly branchedpolycarbonates are prepared by coreacting a polyfunctional or-
ganic compound with the afore-described dihydric phenol and car-
bonate precursor.
The dihydric phenols employed in the practice of this inven-
tion are known dihydric phenols in which the sole reactive groups
are the two phenolic hydroxyl groups. Some of these are repre-
sented by the general formul,a
~ X
HO ~ A)n ~ ~ ~ ~ OH
~X `~
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wherein A is a divalent hydrocarbon radical conkaining 1-15 carbon
O O p
atoms, -S-, -S-S-, -S-, -S-, -o-, or -C-~ X is independently
o
hydrogen, halogen, or a monovalent hydrocarbon radical such as an
alkyl group of 1-4 carbons, an aryl group of 6-10 carbons such as phenyl,
tolyl, xylyl, naphthyl, an oxyalkyl group of 1-4 carbons or an oxyaryl
group of 6-10 carbons and n is O or 1.
Typical of some of the dihydric phenols that can be employed in the
practice of the present invention are bisphenols such as bis(4-hydroxyph-
enyl) methane, 2,2-bis(4-hydroxyphenyl) propane (also known as bis-
phenol-A), 2,2-bis(4-hydroxy-3-methylphenyl)propane, 4-4-bis(4-hydroxy-
phenyl)heptane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, 2,2-bis
(4-hydroxy-3,5-dibromophenyl)propange, etc., dihydric phenol ethers such
as bis(4-hydroxyphenyl) ether, bis(3,5-dichloro-4-hydroxyphenyl) ether,
etc., dihydroxydiphenyls such as p,p'-dihydroxydiphenyl, 3,3'-dichloro-
4,4'-dihydroxydiphenyl, etc.; dihydroxyaryl sulfones such as bis(4-
hydroxyphenyl) sulfone, bis(3,5-dimethyl-4-hydroxyphenyl) sulfone, etc.,
dihydroxy benzenes, resorcinol, hydroquinone, halo- and alkyl-substituted
dihydroxy benzenes such as 1,4-dihydroxy-2,5-dichlorobenzene, 1,4-
dihydroxy-3-methylbenzene, etc., and dihydroxy diphenyl sulfides and
sulfoxides such as bis(4-hydroxyphenyl) sulfide and bis (4-hydroxyphenyl)
sulfoxides, bis-(3,5-dibromo-4-hydroxyphenyl)sulfoxide, etc. A
variety of additional dihydric phenols are also available and are
disclosed in U.S. Patent Nos. 2,999,835 to Goldberg dated September 12,
1961, 3,028,365 to Schnell et al dated April 3, 1962 and 3,153,008
to ox dated October 13, 1964. It is, of course, possible to employ
two or more different dihydric phenols or a copolymer of a dlhydric
phenol with glycol or with hydroxy or acid-terminated polye~t~r,
or with a dibasic acid in the event a polycarbonate copolymer or
interpolymer rather than a homopolymer i.s desired Eor use Ln the
preparation of the polycarbonate polymers of this invention.
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Also employed in the practice of khis invention are blends of
any of the above dihydric phenols, the preferred dihydric
phenol is bisphenol-A. The polyfunctional organic compounds
which may be included within the scope of this invention are
set forth in U.S. Patents 3,635,895 to Kramer dated
January 18, 1972 and 4,001,184 to Scott dated January 4, 1977.
These polyfunctional aromatic compounds contain at least
three functional groups which are carboxyl, carboxylic
anhydride, haloformyl or mixtures thereof. Examples of
these polyfunctional aromatic compounds include trimellitic
anhydride, trimellitic acid, trimellityl trichloride, 4-
chloroformyl phthalic anhydride, pyromellitic acid, pyro-
mellitic dianhydride, mellitic acid, mellitic anhydride,
trimesic acid, benzophenonettracarboxylic acid, benzophe-
nonetetracarboxylic anhydride, and the like. The preferred
polyfunctional aromatic compounds are trimellitic anhydride
or trimellitic acid or their haloformyl derivatives. Also
included herein are blends of a linear polycarbonate and a
branched polycarbonate.
The carbonate precursor can be either a carbonyl halide
or a bishaloformate. The carbonyl halides include car-
bonyl bromide, carbonyl chloride, and mixtures thereof.
The bishaloformates suitable for use include the bishalo-
formates of dihydric phenols such as bischloroformates of
2,2-bis(4-hydroxyphenyl) propange, 2,2-bis(4-hydroxy-3,5-
dichlorophenyl)propane, hydroquinone, and the like, or
bishaloformates of glycols such as bishaloformates of ethylene
glycol, and the like. While all of the above carbonate
precursors are useful, carbonyl chloride, also known as
phosgene, is preferred.
By adding monofunctional compounds which are capable of
reacting with phosgene or with the end groups of the polycarbon-
ates consisting of the chlorocarbonic acid ester group and which
~6~ CL-3~1~
terminate the chains, such as the phenols, e.g., phenol, tert-
butylphenyl, cyclohexylphenol, and 2,2-(4,~-hydxoxyphenylene-4'-
methoxyphenylene)propane, aniline and methylaniline, it is
possible to reyulate the molecular weight of the polycarbonates.
S As mentioned hereinabove, the acid acceptor is an alkali or
alkaline earth metal hydroxide. Illustrative of these acid
acceptors are sodium hydroxide, lithium hydroxide, potassium
hydroxlde, calcium hydroxide, and the like. The amount of said
acid acceptor present should be sufficient to maintain the pH of
the aqueous caustie solution above about 9.
Illustrative of the inert organic solvents which are present
during the reaction and which dissolve the polycarbonate as i~ is
formed are aromatic hydrocarbons and halogenated hydrocarbons such
as benzene, toluene, xylene, chlorobenzene, orthodichlorobenzene,
chloroform, methylene ch-oride, carbon tetrachloride, trichloro-
ethylene and dichloroethane. The solvent is present in an
amount effective to solubilize or dissolve substantially all of
the polycarbonate as it is formed.
The catalytic compounds within the scope of the instant
invention are the substituted pyridlnes and the.ir salts. The
substituted pyridines are represented by the general formula
Rn I.
N
wherein each R is independently selected from alkyl, substituted
alkyl, alkenyl, substituted alkenyl, cycloaliphatic, preferably
cycloalkyl, substituted cycloaliphatic, preferably substituted
cycloalkyl, alkoxy, aryl, substituted aryl, alkaryl, aralkyl,
alkylamino, and dialkylamino radicals; and n is an inteyer having
a value of from 1 to 5, inclusive.
-- 6 --
,
~ ZCL-3~1~
Preferred alkyl radicals represented by ~ are those con-
taining from 1 to about 20 carbon atoms. Illustrative of -these
preferred alkyl groups are methyl, ethyl, n-propyl, isopropyL,
n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, and the
various positional isomers thereof, and likewise the straight
and branched chain positlonal isomers of hexyl, heptyl, octyl,
nonyl, decyl, and the like.
Preferred alkenyl radicals represented by R are those
containing from 2 to about 20 carbon atoms. Illustrative of
these preferred alkenyl radicals are vinyl, allyl, propenyl,
butenyl, 2-methylpropenyl, methallyl, 3-octenyl, an~ the llke.
Preferred cycloalkyl radicals represented by R are those con-
taining from 3 to about 12 carbon atorns. Illustrative of these
cycloalkyl radicals are cyclopropyl, cyclobutyl, cyclopentyl,
cyclohexyl, cycloheptyl, cyclononyl, dimethylcyclohexyl, propyl-
cyclohexyl, and the like.
Pre~erred aryl radicals represented by R are those containing
from 6 to 18 carbon atoms, such as phenyl, naphthyl, and anthracyl
radicals.
Preferred aralkyl radicals represented by R are those con-
taining from 7 to about 20 carbon atoms. Illustrative of these
aralkyl radicals are benzyl, 2-phenylethyl, 2-phenylpropyl,
cumyl, phenylbutyl, naphthylmethyl, and the like.
Preferred alkaryl radicals represented by R are those con-
taining from 7 to about 20 carbon atoms. Illustrative of these
alkaryl radicals are tolyl, 2,6-xylyl, 2,~-xylyl, 2-methyl-1-
naphthyl, and the like.
- Preferred alkoxy radicals represented by R are those con-
taining from 1 to 18 carbon atoms. Illustrative of these alkoxy
radicals are methoxy, ethoxy, isopropoxy, L~entoxy, dodecyloxy,
octadecyloxy, and the like.
-- 7
gCL~
Preferred alkylamino and dialkylamino radicals represented
by R are those containing from 1 to about 20 carbon atoms.
Illustrative of these mono- and dialkylamino radicals are
methylamino, ethylamino, butylamino, octylamino, dimethylamino,
diethylamino, dibutylamino, methyloc~ylamino, me-th~vloctadecyl-
amino, and the like.
T~hen substituent groups are present on the alkyl, alk.eny,
cycloalkyl and aryl radicals, they are preferably those selected
from the group consistin-g of alkyl and alkoxy radicals.
Illustrative substituted pyridines represented by Formula I
include 2-picoline, 3-picoline, 4-picoline, 2-ethylpyridine, 3-
ethylpyridine~ 4-ethylpyridine, 2-isopropylpyridine, 3-isopropyl-
pyridine, 4-isopropylpyridine, 2-butylpyridine, 4-tertiarybutyl-
pyridine, 2,3-lutidine, 2,4-lutidine, 2,5-lutidine, 2,6-lutidine, -
15 3,4~1utidine, 3,5-lutidine, 3,4-diethylpyridine, 3,5-diethylpyri-
dine, 3-ethyl-4 methylpyridine, 2-(3-pentyl)pyridine, 4-(3-
pentyl)pyridine, 2-dimethylaminopyridin0, 4-dimethylaminopyridine',
2-methoxypyridine, 2,6-dimethoxypyridine, 4-cyclohexylpyridine,
4-(5-nonyl)pyridine, 4-phenylpropylpyridine, and the like.
The salts of the substituted pyridines are represented by
the ~eneral formula ~ \ -
! ~ Rn\ y (m) II.
~ H /m
wherein R and n are as defined above and Y is an m valent anion.
Preferred m valent anions represented by Y are sulfate, sulfite,
phosphate, phosphite, halides, nitrate, nitrite, carbonate, and
carboxylates.
The substituted pyridines and their salts are known com-
pounds whose chemistry and preparakion are well known t:o those
skilled in the art. ~hus, these compounds are described in
-- 8
.
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8~
_terocyclic Compounds, Volume 1, ~y R.C~ Elderfiel~, John
Wiley & Sons, Inc., NY, N~.
The amount of substituted pyridine or salt of a su~stituted
pyridine catalyst present during the reaction is a catalytic
amount. By catalytic amount is meant an amount effective to
catalyze the reaction between the dihydric phenol and the
carbonate precursor to produce the high molecular weight poly-
carbonate. Generally, this amount ranges from about 0.01 to
about 10 weight percent based on the weiyht of the dihydric phenol
present.
The process of the instant invention is carried out by
reacting a dihydric phenol, such as bisphenol-A, with a carbonate
precursor, such as phosgene, in a reaction medium containing an
aqueous caustic solution and an inert organic solvent for the
lS polycarbonate and in the presence of a catalytic amount of the
substituted pyridine or substituted pyridine salt catalyst of
the present invention.
The temperature at which this reaction proceeds may vary
from below 0C to about 100C. The reaction proceeds satisfac-
torily at temperatures ranging from about room temperature (25C)to about 50C. Since the reaction is exothermic, the rate of
carbonate precursor addition may be used to control the reaction
temperature. The amount of carbonate precursor, such as phosgene,
required will generally depend upon the amount of dihydric
phenol present. Generally, one mole of the carbonate precursor
will react with one mole of dihydric phenol to provide the poly-
carbonate. When a carbonyl halide, such as phosgene, is used
as the carbonate precursor, two moles of hydrohalic acid such as
HCl are produced by the above r~action. These two moles o~ acid
are neutralized by the alkali and alkaline earth metal hydro~ide
acid acceptor present. The ~oregoing are herein re~erred to as
stoichiometric or theoretical amounts.
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PREFERRED EM~ODIM~N~ ~F THE ~NVEMTION
In order ~o more fully and clearly illustrate the present
invention, the following examples are presented. It is intended
that the examples be considered as illustrative rather than
limiting the invention disclosed and claimed herein. In the
examples, all parts and percentages are on a weight basis unless
otherwise specified.
EXAMPLE 1
This example illustrates an unsuccessful attempt to prepare
a high molecular weight polycarbonate polymer via the interfacial
polymerization technique without the presence of a catalyst. To
a reactor Eitted with a reflux condenser and a mechanical agita-
tor, charge 57 parts of 2,2-bis(4-hydroxyphenyl)propane, 57
parts of water, 325 parts of methylene chloride, and 1.2 parts of
paratertiarybutylphenol. Phosgene is then added to the reaction
mixture at a rate of 0.65 parts per minute for a period of 30
minutes while maintaining the pH at 9 by the addition of a 15~
aqueous sodium hydroxide solution. After 30-minutes, the pH is
raised to 11.0 by the use of additional amounts of sodium
hydroxide solution. Phosgenation is continued for a further 10
minutes at this pH. The material is recovered from the reaction
and found to have an intrinsic viscosity of 0.12 dl./g. This
indicates that a relatively low degree of polymerization is
achieved.
EXAMPLE 2
This example illustrates an unsuccessful attempt to prepare
a hlgh molecular weight polycarbonate polymer via the intexfacial
polymerization technique by using pyridine, which falls outside
the scope of Formula I, as catalyst. To a reactor fitted with a
reflux condenser and a mechanical agitator, charye 57 parts of
2,2-bis(4-hydroxyphenyl)propane, 57 parts of 2ater, 325 parts
of methylene chloride, and 0.4 parts of pyridine. Phosgene is
- 10 -
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then added to the reactio~ mi~ture at a rate of 0.~5 parts per
minute for a period of 30 minutes while maintaining the pH at
9 by the addition of a 15% aqueous sodium h~droxide solution.
After 30 minutes, the pH is raised to 11.0 by the use of addi-
tional amounts of sodium hydroxide solution. Phosgenation iscontinued for a further 10 minutes at this pH. The material is
recovered from the reaction and found to have an intrinsic
viscosity of 0.12 dl./g. This indicates no significant improve-
ment over the insignificant degree of polymerization achieved
in Example 1 wherein the reaction was carried out in the absence
of any catalyst.
EX~MPLE 3
This example illustrates a successful attempt to prepare a
high molecular weight polycarbonate polymer via the interfacial
polymerization technique in the presence of an alkylpyridine
catalyst. To a reactor fitted with a reflux condenser and a
mechanical agitator, charge 57 parts of 2,2-bis(4-hydroxyphenyl)
- propane, 57 parts of water, 325 parts of methylene chloride, and
O A 54 parts of 2,4-lutidine. Phosgene is then added to the
reaction mixture at a rate of 0.65 parts per minute for a period
of 30 minutes while maintaining the pH at 9 by the addition of
a l5% agueous sodium hydroxlde solution. After 30 minutes, the
pH is raised to 11.0 bv the use of additional amounts of sodium
hydroxide solution. Phosgenation is continued for a further 10
minutes at this pH. The material is recovered from the reaction
and found to have an intrinsic viscosity of 0.46 dl./g. This
value indicates that a high degree of pol~merization is
achieved.
EXAMPLES 4-15
-
Substantially the same procedure as described in Example 3
is repeated except that various other substituted pyridine
. , . _ _ . . . . ... .... . . . .. ... . .. _ _ _ . _ .
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9~
catalysts are uti:Lized in place of 2,4-lu-tidine. The su~stituted
pyridines used and the intrinsic viscosity o~ -the polycarbonate
produced are set orth in Table I.
TABLE I
Intrinsir
Catalyst Viscosity
Example No. Name Parts by Weight dl./g.
4 2,6-lutidine 0.54 0.31
2-picoline 0.47 0.19
6 2~ethylpyridine 0.54 0.28
7 2,5-lutidine 0.54 1.05
~ 3,5-lutidine 0.54 0.22
9 2-propylpyridine 0.66 0.77
4-(3-phenylpropyl) 1.00 0.19
pyridine
11 2-(3-pentylpyridine) 0.75 0.22
12 4-dimethylamino- 0.61 0.79
pyridine
13 2,4,6-collidine 0.61 0.63
14 2-methoxypyridine 0.55 0.18
2 vinylpyridine 0.54 0.20
EX~MPLE~ 16-20
Substantially the same procedure as descrlbed in Ex.ample 3
is repeated except that various other substituted pyridine catal-
ysts are utilized in place of 2,4-lutidine and a molecular weight
regulator, i.e., phenol, used. The substituted pyridine used,
the amount of molecular ~eight regulator used, and the intrinsic
viscosity of the polycarbonate produced are set forth in Table
II.
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... . . .. . ..
~ 8~ 8CL-3414
TABL,E II
Catalyst
Parts Pl.enol inIntrinsic
by parts by Viscosity
E~ample No. Name Weiaht weight dl /g
16 2,6-lutidine0.27 0.25 0.30
17 2,4-lutidine0.27 0.25 0.41
18 2,4-lutidine0.54 0.25 0.38
19 2,4,6-collidine 0.31 0.25 0.24
4-dlmethylamino- 0.61 0.25 0.32
pyridine
As can be seen by a comparison of Example 1 with Examples
3-20, the use of the substituted pyridines of Formula I results
in the production of high molecular weight aromatic polycarbonates
via the interfacial polymerization technique, while in the ab-
sence of the substituted pyridine catalyst, the interfacialpolymerization technique is ineffective in producing high molecu-
lar weight aromatic polycarbonates under substantially identical
reaction conditions.
It is further evident ~rom the composition of Examples 1
and 2 that unsubstituted pyridine is not a catalyst in the inter-
facial polymerization system. But on introducing suitable sub-
stituents, as shown by the numerous examples, substituted pyridine
becomes an effective catalyst.
It will thus be seen that the objects set forth above,
among those made apparent from -the preceding description, are
efficiently attained, and since certain changes may be made in
carryiny out the above process and the composition set forth
without departing from the scope of the invention, it is intended
that all matters contained i.n the above description shall be
interpreted as illustrative and not in a limiting sense.
... ..
