Note: Descriptions are shown in the official language in which they were submitted.
RD--606 7
'
A PROCESS FOR Q PPI~G POLYPHENYLE~E OXIDE
The process of this invention relates to the reduc-
tion in the eas~ of oxidative and/or theremal degradation
of polyphenylene oxides by contacting the latter with a cap-
ping agent in the presence of a water soluble base, a cata-
- 5 lytic phase transfer agent, and, optionally, an effective
organic phase reducing agent. More particularly, this inven-
tion comprises contacting a polyphenylene oxide with a
capping agent selected frgm the class consisting of monoacyl
halides of the formula R-C-X, hydrocarbon monosulfonyl halides
of the formulaOR-S82-X, anhydrides of monocarboxylic acids o~
the formula R-C-O-C-R, alkyl halides of the formula R-X,
dialkyl sulfates of the formula R-O-S02-0-R, wherein R is
alkyl, cycloalkyl, aryl or mixtures thereof, X is chlorine,
bromine, fluorine or iodine, wherein said contacting is
carried out in the presence of (1) a water soluble base
selected from the class consisting of alkali metal and
alkaline earth metal bases, (2) a catalytic phase transfer
agent, and, opt~onally, (3) an effective organic phase
j- reducing agent.
Polyphenylene oxides comprise an interesting group
of new polymers which are disclosed in U.S. Patent ~os.
3,306,874, 3,306,875 - issued February 28, 1972 and 3,432,466-
issued March 11, 1969 - Hay, all assigned to the same as~ignee
as the present invention. In general, these polyphenylene oxides
,.
,,
.
RD-6067
are homopolymers or copolymers of poly(2,6-disubstituted-
1,4-phenylene oxide)s which are made by oxidatively coupling
of 2,6-disubstituted phenols.
To date, the prior art has employed various means
of stabilizing polyphenylene oxides against oxidative and
thermal degradation including the methods described in U.S.
Patent Nos. 3,375,228, 3,402,143, 3,535,281 and 3,573,254,
all assigned to the same assignee as the present invention.
As disclosed by the prior art means whi~ provide, in part or
total, oxidative and/or thermal stability to polyphenylené
oxides are desirable in order to prev2nt substantial oxi-
dative attack upon polyphenylene oxide~ thus avoiding
-~ substantial discoloration and/or embrittlement of the oxides
when processed at elevated temperatures into useful articles
of manufacture
An object of this invention is to provide poly-
phenylene oxides which have improved color characteristics.
Another object is to provide an economic process for capping
polyphenylene oxides. These and other objects will be readi-
ly apparent from the following specification and the
appended claims~
In essence, process of oûr invention comprises con-
tacting a polyphenylene oxide with a capping agent selected
from monoacyl halides, monosulfonyl halides, anhydrides of
monocarboxylic acids, alkyl halides, or dialkyl sulfates
r- :
: 1()641~;~
RD-606?
wherein the contacting is carried out in the presence of
(1) a water soluble base, (2) a catalytic phase transfer
agent, and, optionally, (3) an effective organic phase
reducing agent.
In general, the capping agents that are employed
in the practice of this invention are defined herein as com-
pounds which will react with a phenolic hydroxyl group with
subsequent formation of a bond between the oxygen atom of
the phenolic group and a hydrocarbylcarbonyl group, a
hydrocarbylsulfonyl group, a hydrocarbylcarbonyl group, a
hydrocarbyl group, a hydrocarbyloxysulfonyl group, derived
from monoacyl halides, monosulfonyl halides, anhydrides of
monocarboxylic acids, alkyl halides, and dialkyl sulfates,
respectively.
Representative of useful capping agents falling
within the above definitions are the following
(A) monoacyl halides of the formula: R-C-X,
(B) monosulfonyl halides of the formula R-S02-X,
(C) anhydrides of monocarboxylic acids of the formula
O O
R-C-0-C-R,
(D) alkyl halides of the formula R-X, and
(E) dialkylsulfates of the formula R-0-S02-0-R, where-
in the above formulas R is alkyl, cycloalkyl, aryl
or mixtures thereof, such as alkaryl, alkcycloalkyl,
- 25 aralkyl, arcycloalkyl, cycloalkaryl,
-3-
`
6 ~ RD-6067
etc., and X is chlorine, bromine, fluorine or iodine. Pref-
erably, the R groups contain from about 1 to about 30 carbon
atoms, and more preferably contain from about 1 to about 20
carbon atoms~ Representative examples of specific capping
; 5 agents include:
(1) monoacyl halides, such as acetyl fluoride, acetyl
chloride~ acetyl bromide, propionyl halides, butyryl halides,
stearoyl halides, benzoyl halides, toluoyl halides, naphthoyl
halides, cinnamoyl halides, etcO,
(2) monosulfonyl halides, such as methanesulfonyl
halides, benzenesulfonyl halides, toluenesulfonyl halides,
xylene sulfonyl halides, etc ;
(3) anhydrides of monocarboxylic acids, such as acetic
anhydride, propionic anhydride, octanoic anhydride, benzoic
- 15 anhydride, toluic anhydride, butyric anhydride, pivalic
anhydride, m-dichlorobenzoic anhydride, 2,3,4,5,6-
pentachlorobenzoic anhydride, pentaoic anhydride, palmatoic
anhydride, stearic anhydride, etc.;
(4) alkyl halides, such as: methylchloride, methyl-
bromide, methyliodide, isopropyl halides, amyl halides,
hexadecyl halides, cyclopentyl halides, l-halo-l, 3-dimethyl-
cyclopentanes, diphenyldihalomethanes, triphenyl halo-
methanes, etc~; and
(5) dialkylsulfates7 such as: dimethyl sulfate,
diethyl sulfate, dibutyl sulfate, diisoamyl sulfate, dicyclo-
lO~lg;#
RD-6067
hexyl sulfate, didodecyl sulfate, di(octadecyl)sulfate, etc.
As pointed out by the foregoing specific examples, the
particular capping agent employed is not critical, since any
agent which is capable of reacting with phenolic hydroxyl
groups which improves the oxidative and/or thermal stability
of the resulting groups can be employed. A presently
preferred capping agent is acetic anhydride since it is a
readily available inexpensive capping agent
The catalytic phase transfer agents which can be
- 10 employed comprise any compounds which are soluble in the
organic phase of a polyphenylene oxlde reaction mixture.
Among the catalytic phase transfer agents which are suitable
are those selected from the group consisting of quaternary
ammonium compounds, quaternary phosphonium compounds and
tertiary sulfonium compounds, or mixtures thereof. These
compounds can be described as the ammonium, phosphonium and
sulfonium salts having the respective formulas:
[Rl N R~ X C _N-R~ Y
;
rR P R~ X r R ~+
R L R 2
[RI S R~+ X . ¦RI-S-R~+ Y
. . .~ .. ~
0~ 4~ ~ ~
RD-6067
wherein each R' is lndependently selected from aliphatlc
hydrocarbon radicals having from about 1 to about 30 carbon
atoms, preferably from about 2 to about 15 carbon atoms,
each X is selected from the group consisting of Cl , Br ,
F , CH3S03 , CH3C02 , CF3C02 or OH , and each Y is selected
from the group consisting of S04 , C03 , or C204 .
These onium compounds can be prepared by methods
well-known in the art which include the familiar addition
reactions of tertiary aliphatic amines, tertiary aliphatic
phosphines and aliphatic sulfides with aliphatic halides.
The water soluble base can be any water soluble base
which can be dissolved in the aqueous phase of the poly-
phenylene oxide reaction mixture in amounts adequate to
provide sufficient hydroxyl groups within the organo phase to
form an alkali metal or alkabneearth metal cation phenoxide.
Preferably, the bases that are employed are those that are
very soluble in an aqueous mediaO Among the water soluble
base compounds that can be employed are alkali metal or
alkaline earth metal hydroxides and carbonates. Specific
examples include compounds such as potassium hydroxide,
sodium hydroxide, sodium monocarbonate, barium carbonate,
etc.
In general, our process comprises contacting a
polyphenylene oxide reaction product mixture and a catalytic
phase transfer agent in the presence of a water soluble base,
--6--
: ~ :
RD-6067
wherein the contacting is carried out in time periods and in
the presence of amounts of wat0r soluble base and catalytic
phase transfer agent sufficient to react with any phenolic
hydroxyl group and form a resulting alkali or
alkaline earth metal phenoxide group. The addition of the
catalytic phase transfer agent to the polyphenylene oxide
reaction mixture can be either carried out before, during or
- after polymerization of the disubstituted phenol to poly-
phenylene oxide. In a preferred embodiment of this invention,
the catalytic phase transfer agent is employed in the form of
an in situ prepared effective organic phase reducing agent
which contains cations selected from quaternary ammonium,
guaternary phosphonium and tertiary sulfonium ions and an
anion selected from dithionite, dithionate and borohydride
ions in accordance with the invention of D.M. White,
~ described in U,S. patent No. ~ 060, ~/ ~, is8ued ~ove~berv?~, ~77
assigned to the same assignee as the assignee of this invention
Representative of effective organic phase
reducing agents are such compounds as tetramethylammonium
dithionite, tricaprylmonomethylammonium dithionite,
trimethylsulfonium borohydride, tetrapropylammonium
dithionate, etc., and mixtures thereof. In general, in
carrying out the process, it is preferred that the catalytic
transfer agent, and/or effective organic phase reducing agent,
:~)6 ~ RD-6067
water soluble base and capping agent contact the polyphenylene
oxide reaction mixtures at temperatures wherein the capping
agents are not susceptible to significant thermal or hydro-
lytic degradation. Accordingly, it is preferred that our
process, including the in situ preparation of an effective
organic phase reducing agent, be carried out within the
temperature range of from about 0 C. to aboutlOO C. and
even more preferably from about 15 C. to about 80 C.
In general, the proportions of catalytic phase
transfer agent to water soluble base (hereafter sometimes
referred to as CPTA and WSB, respectiiTely) employed to con-
vert the hydroxyl associated with polyphenylene oxide
reaction product groups to metal alkoxide groups can vary
widely. For example, suitable molar proportions of CPTA:WSB
are generally within the range of from about 1:10 to about
1:1000, and more preferably from about 1:100 to about 1:1000.
Molar proportions of capping agent (hereafter some-
times referred to as CA) to water soluble base can also vary
widely Generally, the suitable proportions of CA:WSB are
within the range of from about 1:100 to about 50:1, and more
preferably within the range of from about 1:10 to about 10:1.
In general, suitable molar proportions of capping
agent to polyphenylene oxide, based on a polyphenylene oxide
molecular weight within the range of from about 10,000 to
about 50,000 and a hydroxyl group per polymer unit mole range
-8-
1~4~ RD-6067
of from about 0.5 to about 1.0, are wi.thin the range of from
about 0.5:1 to about 50:1, and more preferably within the
range of from about 1:1 to about 10:1. Generally, poly-
. phenylene oxide reaction mixtures contain from about 0.01%
: 5 to about 1% by weight of unreacted phenolic compounds, as
well as dimers, trimers, tetramers, etc., and other low-
molecular-weight oligomers. Accordingly, the molar
proportions of capping agent to polyphenylene oxide, as
defined based on polyphenylene oxide hereinbefore, have been
established to provide sufficient capping agent molar
quantities to react with substantially all of the hydroxyl
groups contained by the polyphenylene oxide and any unreacted
phenolic compounds, d.imers, trimers, etc., and other low-
molecular-weight oligomers which may constitute a portion of
the polyphenylene oxide after separation from the reaction
mixture~
The economic advantages of the process obtained
from the use of our invention can readily be understood by a
.
comparison of the usual prior art process and our invented
- 20 process in the separation and recovery of polyphenylene oxides
which are substantially resistant to oxidative and thermal
degradation at elevated temperatures~
Polyphenylene oxide reaction product mixtures
generally comprise dimers, trimers, polyphenylene oxide, and
the other oxidation products, such as diphenoquinones,
_g_
4~9..~
: RD-6067
benzoquinones, etc~, a solvent in which the reaction is
carried out, an amine-cupric salt complex, water resulting
from the oxidation step, and a small amount of methanol,
(about 1%, by weight, of the total reaction mixture) which is
added to solubilize the copper salt. The reaction product
: mixture is ordinarily diluted with additional aromatic
hydrocarbon solvent, such as toluene, so that the concentra-
tion of the polyphenylene oxide ranges between 8-10%, by
weight, A small amount of acetic acid is then added in
order to remove the amine used in the catalyst ~ystem and to
assist in the separa~ion of the cupric salt into the aqueous
me.~L~anol ~ . A toluene solution results which con-
tains polyphenylene oxide in combination with diphenoquinone,
other quinone by-products, trimers, tetramers and other
;: lS oligomers Thereafter, large amounts of methanol are added
to the toluene solution in order to precipitate the poly-
phenylene oxide and to extract the quinone-type by-product
constituents, Thereafter, it is customary to recover the
methanol leaving behind a sludge which contains the dipheno-
quinone by-products and monomer, dimer, trimer and other
low-molecular-weight oligomers which are then discarded. As
noted above, the prior art sequence requires the use of
large quantities of methanol (which is difficult to separate
and recover in a form suitable for subsequent reuse in the
preparation of additional polyphenylene oxide) in order to
-10-
RD-6067
obtain the polyphenylene oxide free oL quinone type by-
product impurities. The chara~teristics of the sludge
in which the`diphenoquinone resides is such that it is
ordinarily uneconomical to isolate the quinone by-product.
In the practice of our invention, the process for
isolating polyphenylene oxide from the reaction mixture com-
prises the above initial process steps including, if desired,
the addition of hydrocarbon solvent, such as the afore-
mentioned toluene, so that the concentration of the poly-
phenylene oxide ranges between 8-10%, by weight. Thereafter,
the reaction mixture is contacted preferentially with an
effective organic phase reducing agent (hereafter sometimes
referred to as EOPRA) such as tricaprylmonomethyl ammonium
dithionite in order to reduce any oxo groups associated with
diphenoquinone, and with other oxidation products of the
reactant phenols, then contacted with a WSB to form alkoxide
groups which can be capped~ As an alternative to the afore-
said EOPRA contact, the reaction mixture can be contacted
with a CPTA in the presence of a WSB in order to form suit-
able metal phenoxide groups of the polymer and
the low-molecular-weight oligomers which are readily capped
thereafter The reaction products can be isolated from the
reaction mixture by any suitable liquid-solid separation
techniques, including simple, continuous or steam distilla-
tion, etc., of the polyphenylene oxide reaction mixtures.
64~
RD-6067
Alternatively, separa~ion of the volatile constituents ~rom
the polyphenylene oxide reaction mixture can be carried out
using direct as well as indirect drying techniques. In
general, the separation is preferably carried out by heating
the reaction mixtures to temperatures within the range of
from aboùt 50 to about 150 C., and more preferably within
the range of from about 75 to about 125 C. Following
separation of the volatile constituents from the polyphenylene
oxide reaction mixture, the amine-cupric salt complexes can
be separated from the reaction mixture by extraction with
dilute acid either before or after the precipitation step.
As illustrated above, our process does not require
~ the separation of diphenoquinone, trimers, tetramers, etc.,
¦ in the preparation of oxidatively and thermally stable poly-
phenylene oxides. Elimination of the prior art alcohol
~ ! -
extraction of by-product dimers, etc., obviates difficult and
expensive alcohol separation, recovery and purification
; process operations.
In general, the polyphenylene oxides prepared by
our preferred process, i.e. wherein the polyphenylene oxide
is contacted with an effective organic phase reducing agent
prior to contact with a capping agent, absorb visible light
within the range of from about 4000 to about 5000 Angstrom
units (metric equivalents 400 to 500 nanometers). In
general, the resulting polyphenylene oxides dissolved in
-12-
.
: .
''
RD-606?
benzene (0.1% concentration, 1 cm. cell) have a visible
- spectrum absorbance at 422 nm. of about 0.14 after a EOPRA
contact, and an absorbance at 422 nm. of about 0.04 after a
CA contact. For comparison, polyphenylene oxides isolated
in an identical manner but without contacting EOPRA and CA
have an absorbance at 422 nm. of about 1.8.
Polyphenylene oxides prepared from a process
sequence which includes alcohol extraction of reaction by-
products, with subsequent contact of polyphenylene oxide
contact with CPTA and a WSB, prior to an EOPRA contact with a
capping agent, dissolved in benzene (0.12 concentration, 1
cm. cell) have a visible absorbance at 422 nm. of about 0.03
after an EOPRA contact, and an absorbance of a 422 nm. of
about 0.03 after a CA contact.
As illustrated by the foregoing color data, the use
of the preferred process of this invention which includes the
use of an effective organic phase reducing agent step and a
capping step provides a polyphenylene oxide which is sub-
stantially free of color, thermally and oxidatively stable
and eliminates the process expense of removalofreaction by-
products by an alcohol extract process requirement.
In order that those ~killed in the art may better
understand the invention, the following examples are given
which are illustrative of the practice of the invention, how-
ever, are not intended for the purposes of limitation. In
-13-
-'
,, : . , .
,
~7~
RD-6067
all the examples, all parts are by weight unless otherwise
stated.
EXAMPLE I
A series of acylat~s (capping) of commercial poly-
phenylene oxide reaction mixtures were carried out according-
ly: a solution of 5.0 grams of polyphenylene oxide in 15 ml.
of chlorobenzene was contacted with tricaprylmono~ethyl
ammonium chloride (Aliquat 336~) and a 50% aqueous sodium
hydroxide solution. The resulting mLxture was stirred
vigorously, portions thereof were removed in intervals of 2,
25 and 45 minutes. Acetic anhydride was added to each
portion and each mixture thereafter was stirred for 2 minutes,
diluted with benzene, precipitated by the addition of methanol.
The resulting polymer was washed in methanol, then with water,
then again with methanol, and then dried in 80 C. and 10
; Torr. In all of the test solutions, the polyphenylene oxide
- was a commercial sample of poly(2,6-dimethyl-1,4-phenylene
oxide) having an intrinsic viscosity of 0.49 dl./g. (measured
in chloroform at 25 C.) and an infrared hydroxyl absorbance
- 20 at 3610 cc. 1 of 0.092 for a 2 5% solution in carbon di-
sulfide, CS2, in a 1 cm. thick cell calibrated against CS2 -~
in a matched cell which corresponds to the polyphenylene
oxide product having 0.68 nonhydrogen bonded phenolic
hydroxyl groups per molecule. The product was prepared by
-14- -
(3~ g~
RD-6067
the polymerization of 2,6-xylenol by oxidative coupling of
the same in the presence of a secondary amine basic cupric
complex under oxidative coupling reaction conditions. The
reaction media contained in addition to the poly(2,6-dimethyl-
1,4-phenylene oxide), colored by-products including
3,3',5,5'-tetramethyl-4,4'-diphenoquinone and 2,6-di~ethyl-
benzoquinone. The results of capping the polyphenylene oxide
reaction mixture, the reaction solvent, the capping agent,
the catalytic transfer agent, and the water soluble base
employed is set out in Table Io
TABLE I
Reaction Mixture
(Per R. of Polvphenylene oxlde)
Catalyt~c ,4~ Hydroxyl Groups
Phas~(3~ Water` ' Per Molecule
C~pplng(2) Trangfer Soluble (based on ~R at
~; Run No. Solvent(l) ARent ARent Baoe ~3610 cm
1* 3 ml** 0.1 g. 0 2 g. n.Olg. 0.00
2 10 0 5 0.1 1.0 0.06
3 10 0.5 0 1.0 0.48
; (cont~)
- 4 0 0 0 0 0.68
(;niti
.. PPO)
(1) toluene
(2) acetic anhydride
(3) A 75% solution of tricaprylmonomethyl-
- ammonium chloride in isopropanol
(4) sodium hydroxide
* Reactants allowed to equilibrate 25
min. before acetic anhydride added
** Chlorobenzene as solvent
The above data indicates complete capping of the
reaction mixture was carried out in Run No. 1 under condi-
:-
-15-
- - .
''~
l(?~ t l ~
RD-6067
tions where the quantity of the tricaprylmonomethylammonium
chloride corresponded to only 2% by weight (0.68%, mole per
mole of polymer) of the polymer and where a relatively small
quantity of sodium hydroxide at high concentration in water
was employed.
Run No. 2 was carried out in the presence of much
larger quantities of solvent, capping agent, catalytic phase
- transfer agent and sodium hydroxide.
Run No. 3 carried out demonstrates the significant
- I 10 decrease in the effective capping of polyphenylene oxide when
carried out in the absence of the catalytic phase transfer
agent.
; Run No. 4 defines the hydroxyl groups per molecule
of the polyphenylene oxides prior to their evaluation in Run
Nos. 1, 2 and 3.
.
EXAMPLE II
A series of cappings were carried out in a manner
similar to that of Table I, Run No. 1, of Example I, wherein
various equilibration times in minutes were employed before
the addition of the acetic anhydride capping agent to the
reactants. The polyphenylene oxide control was identical to
that of Example I, Run No. 4. The effect of the equilibra-
tion time upon the degree of capping of the polyphenylene
oxide is demonstrated by the data set out in Table II here-
after:
-16-
~:)t;4~
RD-6067
- TABLE II
Equilibration Time ~OH] Per Polyphenylene
Run No.(min.) Oxide Molecule _
1 2 0.06
~2 25 0.00
3 45 0 00
As illustrated by the foregoing data, the capping
reaction can effectively be carried out over a very short
period of time. Comparable results in capping effectiveness
are obtained wherein tricaprylmonomethylammonium dithionite
is substituted for tricaprylmonomethylammonium chloride in
the capping evaluations of Example I, Run Nos. 1, 2 and 3
and Example II, Run Nos. 1, 2 and 3.
- " '
EXAMPLE III
This example illustrates the reduction, capping and
total isolation of xylenol polymerization reaction products
with catalysis of both of these steps from only a single
addition of a catalytic phase transfer agent at a concentra-
tion of 0.005 g. per g. polymer. To a stirred oxygenated
solution of 0.31 g (0 00031 mole) N,N-dimethylbutylamine in
192 ml. toluene in a 3-neck flask equipped with stirrer, oxy-
gen inlet tube and thermometer and partially immersed in a
25 stirred water bath, was added in the order listed 0.135
g (0.00034 mole) CuBr2 (t-C4H9)NHCH2CH2NHtt-G4Hg) and 25 g-
(0.205 mole) 2,6-dimethylphenol. The mixture was stirred
vigorously under oxygen for 42 minutes. At this point, two
~6 41~ ~
RD-6067
10 ml aliquots were removed and the polymer was isolated
from them in one case by dropwise addition of 50 ml. methanol
to the stirred solution followed by methanol washing of the
solid and drying in a vacuum oven (sample A-l) and in the
other case by adding the polymer reaction mixture to 1 liter
of vigorously stirred, boiling water in a Morton flask which
removed the volatile components by steam distillation and
flash boiling followed by washing the solid with water and
drying in a vacuum oven (sample A-2). The intrinsic
viscosity of the polymer was found to be 0.5 dl./g.
- (chloroform, 25 C.).
To the remaining reaction mixture was added 1.13
ml. of a 10% solution of Aliquat 336~ in toluene (0.5%
catalytic phase transfer agent based on polymer weight).
Nitrogen was bubbled through the mixture and 0,493 g. sodium
dithionite was added in five portions. During this addition,
- two 0.25 ml~ samples o~ water were also added, The reaction
mixture turned from a deep brown to a milky white color
Two aliquots were removed as described above and precipitated
with methanol (sample B-l) and with hot water tsample B-2).
To the remaining reaction mixture was added 3.44
g, of a 50% sodium hydroxide solution (ten times the estimated
phenolic hydroxyl content of the polymer with molecular
- weight of 20,000 and of the biphenol from the reduction of
tetramethyldiphenoquinone, assuming a 2% yield based on the
-. . . . :
.
RD-6067
initial 2,6-dimethylphenol). A light green color was noted.
After 30 minutes, 1.23 g. acetic anhydride (three times the
estimated molar hydroxyl content) was added over a 15 minute
periodO The light yellow solution was divided into two
portions and the polymer was precipitated in the manner des-
cribed above with methanol (sample C-l) and with hot water
(sample C-2),
The discoloration achieved by reduction and capping
for the hot water precipitated polymer was determined by
measuring their visible spectra. The increase in hydroxyl
groups on reduction of carbonyl groups and the decrease on
capping was determined by measuring their infrared spectra.
: .
Visible IR
absorbance* absorbance**
SamPle _ Treatment at 422 nm. at 3610 cm 1
A-2 None 1.83 0.19
B-2 Reduced .14 .28
C-2 Reduced and capped.04 .03
*-1 g. polymer/l. benzene, 1 cm. path
**-0.25 g~ polymer/10 ml. CS2, 1 cm~ path
The visible light absorption of the methanol
precipitàted samples were also decreased by reduction and
capping. The untreated product A-l had an absorbance at 422
nm. of 0.12 while both the reduced and reduced and capped
samples (~-1 and C-l, respectively) had absorbances of 0.03.
Polyphenylene oxides which are capped in accord-
ance with the process of this invention are substantially
-19-
lU6~
RD-6067
free of color bodies, chromophoresj orincip~nt hydroxy~ groups,
and- are substantially resistant to oxidative and/or thermal
degradation at elevated temperatures. Accordingly, these
polymers after capping may be used to prepare improved
articles of manufacture having improved thermal and oxi-
dative stability. Thes~e polyphenylene oxides-csn be employed
either alone or in combination with other resins using
conventional manufacturing techniques such as molding, vacuum
. . .
forming extrusion, etc., in the manufacture of articles hav-
ing improved color oxidation and thermal stability.
The polyphenylene oxides prepared by our invention
are particularly well suited for applications requiring
excellent electrical insulation, good mechanical properties
at elevated temperatures and dimensional stability under
conditions of high humidity and mechanical load, including
television tuner strips, microwave insulation, coil cores,
and transformer housings. In addition, our polyphenylene
oxides can be used for a diversity of water-distribution and
water-treatment applications including molded parts which
require the maintenance of close tolerances in aqueous en-
vironments especially during prolonged immersion in water.
Additionally, among many others, our polyphenylene oxides can
be used in applications requiring service at elevated tempera-
tures, such as in filter stacks, filter discs, and valve seats.
Obviously, other modifications and vsriations of
-20-
;', ' :, ,
o~7
RD-6067
the present invention are possible in light of the above
teachings. It is, therefore, understood that changes may be
made in the particular embodiments of the invention described
which are within the full intended scope of the invention as
defined by the appended claims.
F
