Polyphenylene oxide blending

Polyphenylene oxide is blended with conjugated diene polymer by first producing a polymer mixture of polyphenylene oxide and conjugated diene polymer by solution blending and then mechanically blending the so produced masterbatch with the conjugated diene polymer.

This invention relates to the blending of polyphenylene oxide and 
conjugated diene polymers. In another aspect this invention relates to a 
new polyphenylene oxide conjugated diene polymer blend composition. 
BACKGROUND OF THE INVENTION 
The polyphenylene oxide resins are a family of engineering thermoplastics 
that are well known to the polymer art. The polyphenylene oxides may be 
made by a variety of catalytic and non-catalytic processes from the 
corresponding phenols or reactive derivatives thereof. By way of 
illustration, certain of the polyphenylene oxides are disclosed in U.S. 
Pat. Nos. 3,306,874; 3,306,875; 3,257,357; and 3,257,358. In accordance 
with the prior art the polyphenylene oxides can be prepared by an 
oxidative coupling reaction comprising passing an oxygen-containing gas 
through a reaction solution of a phenol and a metal-amine complex 
catalyst. U.S. Pat. No. 3,356,761 discloses polyphenylene oxide resins 
prepared by dissolving a polyphenylene oxide in styrene monomer and the 
styrene monomer subsequently polymerized into polystyrene to produce a 
mixture of polyphenylene oxide and polystyrene, i.e. a polyphenylene oxide 
resin. U.S. Pat. Nos. 3,373,226 and 3,383,435 disclose mixtures of 
polyphenylene oxide and a styrene resin. 
Blending of polyphenylene oxide, or polyphenylene oxide resins, and 
conjugated dienemonovinylarene block copolymers has been observed 
previously to lead to compositions having useful properties. For example, 
the impact strength of polyphenylene oxide resin can be significantly 
increased by the addition of a minor amount of a conjugated 
diene-monovinylarene teleblock copolymer, whereas the addition of a minor 
amount of a polyphenylene oxide resin to a conjugated diene-monovinylarene 
copolymer results in improved high temperature properties as well as 
improved tear and abrasion resistance. 
Mechanical blending of a polyphenylene oxide and conjugated 
diene-homopolymers or copolymers results in blends having less than 
optimum physical properties. This is due to the requirement that 
mechanical blending to give a homogeneous blend must be conducted at 
temperatures above the glass transition temperature of the polyphenylene 
oxide (ca. 220.degree. C.), which is too high for processing unsaturated 
conjugated diene-homopolymers or copolymers without serious degradation. 
Solution blending of polyphenylene oxide and conjugated diene homopolymers 
or copolymers requires use of a solvent system which typically contains at 
least 10 weight percent, preferably greater than 20 weight percent, 
aromatic hydrocarbon solvent due to the low solubility of polyphenylene 
oxide in paraffinic or cycloparaffinic solvents. Although solution 
blending with a partially or totally aromatic solvent system does give a 
blended composition having good physical properties, solution blending of 
large samples of polymers is time consuming and expensive in view of the 
large quantities of solvent required and the current high prices of 
hydrocarbons, especially aromatic hydrocarbons. 
STATEMENT OF THE INVENTION 
It is one object of this invention to provide a new process for blending 
polyphenylene oxide and conjugated diene polymers. 
A further object of this invention is to provide a new polyphenylene 
oxide/conjugated diene polymer blend composition which is useful as a 
polymer additive. 
Still another object of this invention is to provide a process for 
incorporating polyphenylene oxide into a conjugated diene polymer without 
temperature caused degradation of the conjugated diene polymer. 
As used here, the term "conjugated diene polymer" is intended to refer to 
homopolymers and copolymers of conjugated dienes, particularly including 
conjugated diene-monovinylarene block copolymers. 
In accordance with this invention a process for blending polyphenylene 
oxide and conjugated diene polymer is provided which comprises producing a 
masterbatch of a blend of polyphenylene oxide and conjugated diene polymer 
by solution blending and thereafter mechanically blending this masterbatch 
with a second conjugated diene polymer which can be the same as or 
different from the conjugated diene polymer used for the production of the 
masterbatch. Optional ingredients that can be incorporated into the 
mixture and are preferably incorporated into the masterbatch are styrene 
resins, extender oils, and conventionally employed polymer additives. 
More specifically, this invention provides a process for blending 
polyphenylene oxide and conjugated diene polymer comprising the following 
steps: 
Polyphenylene oxide and a first conjugated diene polymer are solution 
blended to form a solution of these polymers in a solvent. Then a blended 
initial mixture of polyphenylene oxide and said first conjugated diene 
polymer is recovered from this solution, the initial mixture being 
essentially free of this solvent. Finally, the initial mixture or at least 
a portion thereof is mechanically blended (let down) with a second 
conjugated diene polymer to obtain the final mixture of polyphenylene 
oxide in the conjugated diene polymer. The second conjugated diene polymer 
can be the same as or different from the first conjugated diene polymer. 
The polymeric blend composition prepared by this solution masterbatch and 
mechanical blending let down process has physical properties which are 
superior to those of a similar blend prepared by mechanical blending only. 
Furthermore, the solution masterbatch-mechanical blending let down process 
compared to an all solution blending process, is less expensive, less time 
consuming, and provides considerable versatility in that a series of 
polymeric blend compositions having different polyphenylene 
oxide:conjugated diene monovinylarene copolymer weight ratios can be 
prepared from a given masterbatch by adding various levels of conjugated 
diene monovinylarene copolymer during the mechanical blending let down 
step. 
In accordance with a second embodiment of this invention a composition of 
matter is provided which comprises an intimate admixture of 65 to 130 
parts by weight of polyphenylene oxide and 100 parts by weight of an 
elastomeric, rubbery nonresinous conjugated diene polymer. This 
composition of matter, which can also be characterized as comprising 
roughly equal quantities by weight of polyphenylene oxide and elastomeric, 
rubbery conjugated diene polymer, is useful as an additive that can be 
mechanically blended with conjugated diene polymers in such quantities as 
desired for obtaining certain quantities in such polymers that are 
attributable to the desired concentration of polyphenylene oxide in such 
rubbery polymer blends. The term "rubbery" as used above refers to a 
material that is capable of recovery from large deformations quickly and 
forcibly and retracts within one minute to less than 1.5 times its 
original length after being stretched at room temperature 
(20.degree.-27.degree. C.) to twice its length and held for one minute 
before release (ASTM D 1566-76). Further details and specifically 
preferred additional embodiments of this composition will become apparent 
from the following description and the claims. 
The composition and process of this invention constitute a significant 
improvement in the art of blending polyphenylene oxide into conjugated 
diene polymers, particularly into rubbery conjugated diene polymers. The 
quantity of polyphenylene oxide mixed with the conjugated diene polymer 
can be readily controlled. A homogeneous distribution of polyphenylene 
oxide in the final polymer is achieved without the application of overly 
high temperatures and the preparation of the masterbatch of a 
polyphenylene oxide/conjugated diene polymer mixture by solution blending 
is not an economically prohibitive step. 
POLYPHENYLENE OXIDES AND POLYPHENYLENE OXIDE RESINS 
The polyphenylene oxides have the repeating structural unit of the general 
formula: 
##STR1## 
wherein the oxygen atom of one repeating unit is connected to the 
phenylene nucleus of the next repeating unit, R is a monovalent 
substituent selected from the group consisting of hydrogen, hydrocarbon 
radicals free of a tertiary .alpha.-carbon atom, halohydrocarbon radicals 
having at least two carbon atoms between the halogen atom and phenyl 
nucleus and being free of a tertiary .alpha.-carbon atom, hydrocarbonoxy 
radicals free of aliphatic, tertiary .alpha.-carbon atoms, and 
halohydrocarbonoxy radicals having at least two carbon atoms between the 
halogen atom and phenyl nucleus and being free of an aliphatic, tertiary 
.alpha.-carbon atom; R' is the same as R and may additionally be a 
halogen; and x may represent any whole integer greater than 100. 
Examples of polyphenylene oxides corresponding to the above formula can be 
found in the above-referenced patents of Hay and Stamatoff. Especially 
preferred is poly(2,6-dimethyl-1,4-phenylene oxide). 
The polyphenylene oxides may be prepared in various ways. One method 
comprises oxidizing a phenol represented by the formula: 
##STR2## 
where R and R' have the same meanings given above. These phenols are 
oxidized by passing an oxygen-containing gas through the particular phenol 
in the presence of a catalyst system comprising a cuprous salt and a 
tertiary amine. 
The polyphenylene oxide, which is used for blending with the conjugated 
diene-monovinylarene copolymer, preferably is the pure polymer, or 
alternatively, it may be a styrene resin modified-polyphenylene oxide, 
i.e. a blend of a polyphenylene oxide and a styrene resin. 
The styrene resin is a resinous polymer having at least 25 weight percent 
of the polymer units derived from the compound having the formula: 
##STR3## 
wherein R.sup.2 and R.sup.3 are selected from the group consisting of 
hydrogen and lower alkyl or alkenyl groups of from 1 to 6 carbon atoms; 
R.sup.4 and R.sup.5 are selected from the group consisting of chloro, 
bromo, hydrogen, and lower alkyl groups of from 1 to 6 carbon atoms; and 
R.sup.6 and R.sup.7 are selected from the group consisting of hydrogen and 
lower alkyl and alkenyl groups of from 1 to 6 carbon atoms or R.sup.6 and 
R.sup.7 may be concatenated together with hydrocarbyl groups to form a 
naphthyl group. 
The term "styrene resin" as used herein includes by way of example, 
homopolymers such as polystyrene, poly(.alpha.-methylstyrene), and 
poly(chlorostyrene), the modified polystyrenes such as rubber modified 
polystyrenes, and styrene-containing copolymers such as 
styrene-chlorostyrene copolymers, styrene-bromostyrene, copolymers, 
styrene-acrylonitrile copolymers, styrene-butadiene copolymers, 
styrene-acrylonitrile-.alpha.-alkylstyrene copolymers, 
styrene-acrylonitrile-butadiene copolymers, and styrene-maleic anhydride 
copolymers. In addition, other suitable polymers include graft copolymers 
of styrene or .alpha.-methylstyrene polymerized on a polybutadiene or a 
butadiene-styrene copolymer, and graft copolymers of styrene or 
.alpha.-methylstyrene with vinyl monomers polymerized on a polybutadiene 
or a butadiene-styrene copolymer. The styrene resins described above may 
be prepared using polymerization methods described in such as Billmeyer's 
Textbook of Polymer Science, New York, Interscience Publishers, 1966. 
The method of blending the polyphenylene oxide with the styrene resin, when 
a styrene resin modified-polyphenylene oxide is to be used in the process 
of this invention, is not critical and does not constitute a part of this 
invention. The commercially used method comprises blending the 
polyphenylene oxide and the styrene resin in powder or granular form, 
extruding the blend, chopping into pellets and reextruding. Another 
possibility in accordance with this invention would involve the solution 
blending of polyphenylene oxide, styrene resin and conjugated diene 
polymer to produce the masterbatch polymer mixture; thereby the additional 
step of blending polyphenylene oxide and, e.g. polystyrene is avoided. 
The polyphenylene oxides and the styrene resins are combinable with each 
other in all proportions. Consequently, compositions comprising from 30 to 
100 weight percent polyphenylene oxide and from 70 to 0 weight percent 
styrene resin are included within the scope of the invention. In general, 
compositions containing from 40 to 85 percent polyphenylene oxide and from 
60 to 15 percent styrene resin exhibit the best overall combination of 
properties and these compositions are preferred. 
Suitable commercially available polystyrene-modified polyphenylene oxides 
are sold by General Electric under the trademark "Noryl." 
Conjugated Diene Polymers 
Both for the preparation of the masterbatch and for the final mixing step 
in the process of this invention homopolymers or copolymers of conjugated 
diene are useful. Thus, poly(1,3-butadiene) as well as copolymers of 
1,3-butadiene and styrene are useful. These polymers are rubbery, 
elastomeric polymers as defined above and not resins. 
Preferably conjugated diene-monovinylarene copolymers are used in the 
process of this invention. In general, any copolymer containing one or 
more blocks of polymerized monovinylarene is suitable for use in the 
process of this invention. Therefore, any monomer containing an active 
vinylidene group (CH.sub.2 .dbd.C&lt;), a conjugated dienyl group, or having 
a cyclic ester structure (lactone), and which is copolymerizable with a 
monovinylarene monomer can be used for preparing the polymers to be 
solution masterbatched with the polyphenylene oxide or polyphenylene oxide 
resins according to the process of this invention. 
Presently preferred are the conjugated dienemonovinylarene teleblock 
copolymers represented by the general formula I or II, 
##STR4## 
wherein A represents a block of polymerized monovinylarene monomer, B 
represents a block of polymerized conjugated diene units or alternately a 
random or random tapered block copolymer of conjugated diene and 
monovinylarene monomers, Y is the residual unit from a multifunctional 
coupling agent or a multifunctional initiating species and n has a value 
from 2 to 6. 
Conjugated dienes useful in the preparation of homopolymers and the linear 
and branched teleblock copolymers of this invention are generally those 
containing 4 to 12 carbon atoms per molecule, preferably those containing 
4 to 8 carbon atoms per molecule. Specific examples of useful conjugated 
dienes include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 
piperylene, 3-butyl-1,3-octadiene, and 2-phenyl-1,3-butadiene, and 
mixtures thereof. Especially preferred is 1,3-butadiene due to its 
availability and favorable cost. 
The monovinylarene monomers which are employed with the above described 
conjugated dienes in forming the linear and branched teleblock copolymers 
include those containing from about 8 to 20 carbon atoms per molecule. 
Examples of specific monovinylarene monomers include styrene, 
.alpha.-methylstyrene, p-vinyltoluene, and p-t-butylstyrene, and mixtures 
thereof. Presently preferred is styrene due to its availability. 
Linear and branched teleblock copolymers of this invention can be prepared 
by techniques well known in the art. Such techniques are disclosed in U.S. 
Pat. Nos. 3,251,905, 3,281,383, 3,639,521, and 3,639,517. Typical of such 
techniques are the sequential polymerization of monomer increments 
initiated by organomonolithium compounds followed by optional coupling 
with polyfunctional coupling agents, and the sequential polymerization of 
monomer increments initiated by organomultilithium compounds. 
The teleblock copolymers presently preferred for the invention generally 
contain from 15 to 90 weight percent polymerized conjugated diene units 
with the balance being polymerized monovinylarene units. Number average 
molecular weights of the useful copolymers are generally in the range of 
about 25,000 to 1,000,000, preferably in the range of about 100,000 to 
400,000. 
The rubbery conjugated diene polymers which are preferred in accordance 
with this invention, frequently are used in the form of oil extended 
rubbers. Based on 100 parts by weight of the conjugated diene polymers 5 
to 1000, typically 25 to 400, parts by weight of extender oil may be 
present. It is preferred to use 15 to 150 parts by weight of extender oil. 
This extender oil is preferably a naphthenic extender oil and may be 
present in both the masterbatch and the second diene polymer or in only 
one of the conjugated diene polymers. 
The hydrogenated analogues of these polymers are also suitable for this 
invention. 
MASTERBATCH COMPOSITION AND PREATION 
The weight ratio of polyphenylene oxide:conjugated diene polymer to be used 
in preparing the solution blended masterbatch can range broadly from 90:10 
to 1:99, preferably from 50:50 to 10:90. The weight ratio chosen will 
depend at least partially on the final polymeric blend composition(s) that 
are to be prepared from the masterbatch by the final mechanical let down 
step. 
The weight ratio of total solvent:total polymer for preparing the 
masterbatch generally should be greater than 3:1 to insure polymer 
solubility. Solvent systems will be described below. 
The generally employed and the preferred compositions of the masterbatch as 
well as the final mixture are shown in the following tabulation. 
______________________________________ 
Masterbatch Composition 
(Parts by Weight) 
Generally Preferred 
______________________________________ 
Polyphenylene oxide 
1 to 900 11 to 100 
Conjugated diene polymer 
100 100 
Styrene resin 0 to 2100 0 to 150 
Extender oil 0 to 1000 15 to 150 
______________________________________ 
Other materials optionally can be solution blended with the two polymers in 
the masterbatch preparation step. These other materials preferably should 
be soluble in the blending solvent, and can include such as extender oils, 
antioxidants, UV stabilizers, plasticizers, processing aids, other 
polymers, and the like, and mixtures thereof. 
Solvent systems suitable for use in solution blending of the masterbatch 
typically contain at least 10 weight percent, preferably at least 20 
weight percent, aromatic hydrocarbon solvent so as to prevent 
precipitation of the polyphenylene oxide during blending and prior to 
isolation of the polymeric masterbatch (polyphenylene oxides have limited 
solubility in paraffinic and cycloparaffinic solvents). An all aromatic 
hydrocarbon system, i.e. one or more aromatic hydrocarbon solvents, is 
especially suitable since polyphenylene oxides and conjugated 
diene-monovinylarene copolymers typically are readily soluble in aromatic 
solvents. Alternatively and preferably for the sake of convenience in some 
instances, the conjugated diene-monovinylarene copolymer can be dissolved 
in one or more paraffinic or cycloparaffinic hydrocarbon solvents, and the 
polyphenylene oxide or polyphenylene oxide resin dissolved in an aromatic 
hydrocarbon solvent, and the two solutions then mixed together. This is 
especially practical when a conjugated diene-monovinylarene polymer cement 
is available for blending with an aromatic hydrocarbon solution of a 
polyphenylene oxide. A premixed mixture of aromatic hydrocarbon and 
paraffinic or cycloparaffinic hydrocarbon solvents can also be used to 
dissolve the polymers for the solution blending masterbatch preparation 
step. 
The aromatic hydrocarbon solvents suitable for solution blending of the 
masterbatch include aromatic hydrocarbon solvents which may or may not be 
ring-substituted with one or more paraffinic and cycloparaffinic side 
chains, wherein the total number of carbon atoms in all the substituents 
attached to the aromatic nucleus is about six or less. The total number of 
carbon atoms in the aromatic solvent is generally 6 to 14. Examples of 
such solvents include benzene, toluene, cumene, the xylenes, the 
diethylbenzenes, mesitylene, p-cymene, and cyclohexylbenzene, alone or in 
admixture. 
The solution blending step is conducted in any container or apparatus which 
insures intimate mixing and which results in the formation of a 
homogeneous blend of polymers and other optional materials. Nonlimiting 
examples of suitable containers and apparatus for solution blending of the 
masterbatch include mechanically stirred reaction vessels and sealed 
beverage bottles which are mechanically tumbled. 
The solution blending step can be conducted at temperatures and pressures 
sufficient to maintain the polymers in solution. Typically the temperature 
is maintained within the range of about 25.degree. C. up to the boiling 
point of the lowest boiling solvent being used. Typically the blending 
temperature will thus be in the range of 25.degree. C. to 175.degree. C. 
The duration of the solution blending step is for that period of time 
which will result in the formation of a homogeneous solution of the 
polymers being blended in the solvent mixture. Following formation of the 
homogeneous masterbatch solution of the blended polymers, the masterbatch 
blend is isolated from the solvent mixture by typical recovery methods 
such as steam stripping, followed by separation of the precipitated or 
solid polymeric masterbatch blend by filtration, decantation, or other 
suitable means. 
MECHANICAL LET DOWN 
The final step in the blending process of this invention consists of 
mechanically mixing the previously described masterbatch with additional 
polymers and other compounding ingredients to obtain the final desired 
composition. Typically during this step additional conjugated diene 
polymer is added, preferably along with such ingredients as extender oils, 
antioxidants, UV stabilizers, processing aids, fillers, vulcanization 
ingredients, plasticizers, other polymers, and the like, and mixtures 
thereof, as desired or needed. The mechanical let down step can be 
conducted using any suitable mixing device conveniently and conventionally 
used for mixing rubbers or plastics, such as a differential roll mill, a 
Banbury mixer, an extruder, or a Brabender Plasti-Corder. In order to 
facilitate thorough mixing of the polymers and optional ingredients, and 
to develop the optimum physical properties, the mechanical let down step 
is carried out at sufficiently high temperatures to soften the polymers so 
that they are thoroughly dispersed and intermingled with each other. The 
mechanical mixing temperature will, in general, vary with the particular 
polymers employed; usually the polyphenylene oxide, which is the higher 
softening material, will govern the mixing temperature selected. For best 
results the mechanical blending temperature will be 140.degree. to 
200.degree. C. Mixing is continued until a uniform blend is obtained. 
The weight ratio of polyphenylene oxide:conjugated diene-monovinylarene 
copolymer in the final composition can range from 90:10 to 1:99, 
preferably 40:60 to 5:95, more preferably 25:75 to 15:85.

EXAMPLE I 
This example illustrates the usefulness of the masterbatch let down process 
for preparing polyphenylene oxide/butadiene-styrene radial teleblock 
copolymer blends, and the superior physical properties of blends prepared 
by this method compared to the properties of mechanically prepared blends. 
A polymeric masterbatch was prepared by dissolving one hundred parts by 
weight of 70/30 butadiene/styrene radial teleblock copolymer (added as 
Solprene.RTM. 411, manufactured and sold by Phillips Petroleum Company), 
75 parts by weight of poly(2,6-dimethyl-1,4-phenylene oxide), 50 parts by 
weight of Flexon 766 naphthenic extender oil, 0.3 parts by weight Irganox 
1076 (n-octadecyl [3-(3,5-di-t-butyl-4-hydroxyphenyl)]-propionate; 
Ciba-Geigy Corp.) and 0.5 parts by weight trisnonylphenyl phosphite in 
2025 parts by weight toluene in a stirred vessel at 93.degree. C. for one 
hour. The polymeric blend masterbatch was isolated by steam stripping and 
then tray dried to less than 0.75 weight percent volatiles at about 
70.degree. C. for about 8 hours. One hundred parts by weight of the dried 
masterbatch was mechanically blended with 275 parts by weight of 
additional 70/30 butadiene/styrene radial teleblock copolymer 
(Solprene.RTM. 411) and 175 parts by weight of additional Flexon 766 
naphthenic extender oil in a Midget Banbury mixer. The mixer was operated 
at 140 rpm with water at 70.degree. C. continuously being circulated 
through the jacket of the mixer. The masterbatch, the additional 
butadiene/styrene copolymer, and one half of the additional extender oil 
was initially charged to the mixer. When the stock temperature reached 
140.degree. C., the remainder of the additional extender oil was added. 
After a total mixing time of six minutes, the oil-extended polymeric blend 
composition was dumped at a stock temperature of 165.degree. C., and then 
further mixed on a 6".times.12" roll mill at 125.degree. C. before 
sheeting off. Test specimens for physical property evaluation were cut 
from 0.080 inch thick (0.203 cm) slabs which were compression molded at 
175.degree. C. 
A second 100 parts by weight portion of the dried masterbatch was 
mechanically blended with 412.5 parts by weight of an oil-extended 70/30 
butadiene radial teleblock copolymer which contained 50 parts by weight 
Flexon 766 naphthenic extender oil per 100 parts by weight of the 
butadiene/styrene copolymer (added as Solprene.RTM. 480, manufactured and 
sold by Phillips Petroleum Co.) to give a blend having the identical 
composition as that of the first masterbatch let down composition 
described above. The mechanical blending step and test specimen 
preparation were conducted using the same equipment and using the same 
basic procedure described above. 
As a control sample, a mechanically blended composition comprising 100 
parts by weight of 70/30 butadiene/styrene radial teleblock copolymer, 20 
parts by weight poly(2,6-dimethyl-1,4-phenylene oxide), and 60 parts by 
weight Flexon 766 naphthenic extender oil was mixed and test specimens 
prepared using the same conditions described above for the mechanical let 
down of the solution masterbatch, with the one exception that all of the 
extender oil was charged initially to the Banbury mixer along with all of 
the two polymers. 
As a second control, a solution blended composition comprising the same 
amounts and types of polymers and extender oil used for preparing the 
mechanically blended composition was prepared using toluene as the 
solvent. The procedure and conditions for preparing this solution blended 
composition was the same as used for preparing the solution blended 
masterbatch as described earlier. Test specimens were prepared as 
described for the masterbatch let down and mechanically blended 
compositions. 
Physical properties of these polymeric blends prepared by mechanical, 
solution, and masterbatch let down procedures are shown in Table I. 
TABLE I 
__________________________________________________________________________ 
Physical Properties of Masterbatch Let Down, Solution Blended, and 
Mechanically 
Blended Poly(2,6-dimethyl-1,4-phenylene Oxide)/Styrene 
Radial Teleblock Copolymer.sup.a Compositions.sup.b 
300% Hardness, 
Blending Melt 
Distortion 
Modulus, 
Tensile, MPa.sup.e 
Shore A 
Run 
Method Flow.sup.c 
(100.degree. C.), %.sup.d 
MPa.sup.e 
25.degree. C. 
60.degree. C. 
80.degree. C. 
(25.degree. C.).sup.f 
__________________________________________________________________________ 
1 Mechanical.sup.g 
82 67 1.6 3.9 1.2 0.5 45 
2 Solution.sup.h 
2.8 0 3.2 8.6 6.9 4.1 68 
3 Masterbatch 
let down.sup.i 
20 1.6 2.8 11.3 
5.4 2.8 60 
4 Masterbatch 
let down.sup.j 
26 6.7 2.9 9.5 4.8 2.4 56 
__________________________________________________________________________ 
.sup.a Added as Solprene.RTM. 411, a 70/30 butadiene/styrene radial 
teleblock copolymer having M.sub.w /M.sub.n of about 300,000/220,000, or 
as Solprene.RTM. 480 (see footnote .sup.j). 
.sup.b All compositions consist of 100 parts by weight of the 
butadiene/styrene copolymer, 20 parts by weight of the polyphenylene 
oxide, and 60 parts by weight of the naphthenic extender oil Flexon 766. 
.sup.c ASTM D123873; condition F. 
.sup.d ASTM D263376. 
.sup.e ASTM D41275. 
.sup.f ASTM D224075. 
.sup.g The composition of footnote .sup.b mixed in a Midget Banbury mixer 
for six minutes and dumped at 165.degree. C. Rubber added as Solprene.RTM 
411. 
.sup.h The composition of footnote .sup.b solution blended in toluene and 
recovered by steam stripping. Rubber added as Solprene.RTM. 411. 
.sup.i Solution blended (toluene) masterbatch of 100 parts by weight 70/3 
butadiene/styrene radial teleblock copolymer, 75 parts by weight 
poly(2,6dimethyl-1,4-phenylene oxide), and 50 parts by weight Flexon 766 
naphthenic extender oil was mechanically blended with 275 parts by weight 
of additional 70/30 butadiene/styrene radial teleblock copolymer and 175 
parts by weight additional naphthenic oil in a Midget Banbury mixer for 
six minutes and dumped at 165.degree. C. to give the composition of 
footnote .sup.b. Rubber added as Solprene.RTM. 411. 
.sup.j The same solution blended masterbatch of footnote .sup.i was 
mechanically blended with 412.5 parts by weight of Solprene.RTM. 480 (an 
oilextended 70/30 butadiene/styrene radial teleblock copolymer having 
M.sub.w /M.sub.n of about 300,000/220,000 and containing 50 parts of 
naphthenic oil per 100 parts of butadiene/styrene copolymer) and 37.5 
parts by weight of additional naphthenic oil in a Midget Banbury for 6 
minutes and dumped at 165.degree. C. to give the composition of footnote 
.sup.b. 
These data illustrate that the poly(2,6-dimethyl-1,4-phenylene 
oxide)/butadiene-styrene radial teleblock copolymer blends prepared by the 
masterbatch let down process of this invention (Runs 3 and 4) have 
physical properties superior to those obtained by one step mechanically 
blending of the entire composition (Run 1), and furthermore the polymeric 
blends prepared by the process of this invention have properties that are 
in the range of the properties of a blend prepared by a one step solution 
blending process (Run 2), which requires considerably more solvent, which 
must be recovered and purified, than the masterbatch let down process of 
this invention. 
Reasonable variations and modifications which will become apparent to those 
skilled in the art can be made in this invention without departing from 
the spirit and scope thereof.