Note: Descriptions are shown in the official language in which they were submitted.
8CH-2145
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The present invention relates to thermoplastic molding
compositions which are based on an intimate admixture of a
copolymer of a vinyl aromatic compound and an ~ , B-unsaturated
cyclic anhydride and a radial teleblock copolymer of a vinyl
aromatic compound, a conjugated diene and a coupling agent,
with or without a polyphenylene ether resin present. The
compositions of this invention provide molded articles having
good overall mechanical properties, e.g., impact strength,
tensile strength, tensile elongation, and the like.
Vinyl aromatic resins, e.g., polystyrene, have been
found to be useful in thermoplastic molding compositions.
Vinyl aromatic resins have poor heat distortion and impact
resistance, however, and attemps have been made to upgrade
these properties. One approach has been to modify the vinyl
aromatic resins by copolymerizing these materials with ~ ,
B unsaturated cyclic anhydrides, to form copolymers such
as poly(styrene-maleic anhydride).Although improvements
in heat resistance and solvent resistance are provided, the -~
resulting copolymers are somewhat brittle, and do not
have good resistance to impact.
Various attemps have been made to improve the impact
resistance of copolymers of vinyl aromatic resins and ~, B-
unsatured cyclic anhydrides. For instance, these copolymers
have been blended with nitrile rubbers. Blends of nitrile
rubber and styrene-maleic anhydride copolymers are disclosed
in U.S. Patent 2,914,505 dated November 24, 1959 and U.S.
Patent No. 3,641,212 dated February 8, 1972. With some of
these compositions, however, the components are not com-
patible, and the compositions are difficult to prepare.
It has now been surprisingly discovered that copolymers
of a vinyl aromatic compound and an ~, ~-unsaturated cyclic
anhydride can be combined with a radial teleblock copolymer of
,.~
lQ8869~ 8CH-2145
a vinyl aromatic compound and a conjugated diene, e.g., a
styrenebutadiene radial teleblock copolymer, to form com-
positions which can be molded to articles having good
mechanical properties, including good impact strength,
tensile yield and elongation.
As used herein, the term "radial teleblock copolymer"
refers to branched polymers having segments, or blocks,
which are comprised of a conjugated diene polymer, blocks
of a vinyl aromatic polymer, and a coupling agent. More
particularly, in the copolymer structure, several chains
of the diene polymer, usually three or more, extended
from a coupling agent, with each chain terminating at its
other end with a block of the vinyl aromatic polymer. It
is generally believed that incompatibility of the block
segments in the radial teleblock copolymer promotes the
formation of a two-phase system with blocks of the vinyl
aromatic polymercoalescingto form discrete regions, or
"domains". These domains simulate the effect of cross-links
between the chains of elastomer, and a branched elastomeric
network is thus formed comprising blocks of a conjugated
diene polymer, blocks of vinyl aromatic polymer, and a coupl-
ing agent.
Radial teleblock copolymers are known in the art.
For instance, detailed descriptions of these materials are
given by Marrs et al in ADHESIVES AGE, December, 1971, pp.
15-20 and by Haws et al in RUBBER WORLD, January, 1973, pp.
27-32 .
The present invention provides, in its broadest aspects,
a thermoplastic composition which comprises an intimate
admixture of:
(i) a copolymer of a vinyl aromatic compound and an
~, ~ -unsaturated cyclic anhydride; and
8CH-2145
36~
(ii) a radial teleblock copolymer of a vinyl aromatic
compound, a conjugated diene and a coupling agent.
In a preferred embodiment, the compositions of this
invention further comprise a polyphenylene ether resin.
The copolymers of a vinyl aromatic compound and an
~ unsaturated cyclic anhydride (i) are well known in the
art and are described in the literature. In general, they
are prepared by conventional bulk solution or emulsion
techniques using free-radial initiation. For example, styrene-
maleic anhydride copolymers can be obtained by simply react-
ing the two monomers, i.e., styrene and maleic anhydride, at
50C in the presence of benzoyl peroxide. The rate of poly-
merization may be better controlled if a solvent such as
acetone, benezene or xylene is used.
The vinyl aromatic compound of component (i) can be
derived from compounds of the formula:
CR _ 2
(I) R5 1 - CHR
~ 3
R6 ~ R4
wherein Rl and R2 are selected from the group consisting of
(lower) alkyl or alkenyl groups of from 1 to 6 carbon atoms
and hydrogen; R3 and R4 are selected from the group consisting
of chloro, bromo, hydrogen and (lower) alkyl of from 1 to 6
carbon atoms; R5 and R6 are selected from the group con-
sisting of hydrogen and (lower) alkyl and alkenyl groups of
from 1 to 6 carbon atoms or R5 may be concatenated together
with hydrocarbyl groups to form an naphthyl group. These
compounds are free of any substituent that has a tertiary
carbon atom. Styrene is the preferred vinyl aromatic
compound.
,
~8~6~3 8CH-2145
The ~ ,~ -unsaturated cyclic anhydride of component
(i) can be represented by the formula:
(II) R7 C(H)n ~ ~ - C - - - (CH2)m - R
wherein the dotted lines represent a single or a double car-
bon to carbon bond, R7 and R8 taken together represents a
O O
Il 11 9
C _ O - C linkage, R is selected from the group consisting of
hydrogen, vinyl, alkyl, alkenyl, alkylcarboxylic or alkenyl-
carboxylic of from 1 to 12 carbon atoms, n is 1 or 2, de-
pending on the position of the carbon-carbon double bond,
and m is an integer of from 0 to about 10. Examples include
maleic anhydride, citraconic anhydride, itaconic anhydride,
aconitic anhydride, and the like.
The preparation of these copolymers is described in
U.S. Patent No, 2,971,939 dated February 14, 1961, U.S.Pat.,
No. 3,336,267 dated August 15, 1967 and U.S. 2,769,804
dated November 6, 1956.
The copolymers which comprise component (i) include
rubber-modified copolymers thereof. The rubber employed in
preparing the rubber-modified copolymers of a vinyl aromatic
compound and an ~ ~-unsaturated cyclic anhydride can be a
polybutadiene rubber, butyl rubber, styrene-butadiene rubber,
acrylonitrile rubber, ethylene-propylene copolymers, natural
rubber, EPDM rubbers and the like.
The preparation of rubber-modified copolymers of a vinyl
aromatic compound and an ~ , ~-unsaturated cyclic anhydride
is described in Netherlands 7,212,714.
Component (i) can comprise from 40 to 1 parts by weight
of the ~ , ~-unsaturated cyclic anhydride, from 60 to 99
parts by weight of a vinyl aromatic compound and from 0 to
8CH-2145
~S38~36~9~
25 parts by weight of rubber. The preferred polymers will
contain about 25-5 parts by weight of the ~, ~ unsaturated
cyclic anhydride, 75-95 parts by weight of the vinyl aromatic
compound, and 10 parts by weight of rubber.
A preferred unmodified vinyl aromatic~ -unsaturated
cyclic anhydride copolymer useful in the composition of this
invention is Dylark 232, commercially available from Arco
Polymers. Dylark 232 is a styrene-maleic anhydride copolymer
containing about 11% maleic anhydride, the balance being
styrene. A preferred rubber-modified vinyl aromatic~
unsaturated cyclic anhydride copolymer is Dylark 240, which is
also available from Arco Polymers. Dylark 240 is a high im-
pact styrene-maleic anhydride copolymer containing 9-10% rubber
and 9% maleic anhydride, the balance being styrene.
The radial teleblock copolymers (ii) are available com- ~-
mercially or can be prepared by following the teachings of
the prior art. As an illustration, they can be made by poly-
merizing conjugated dienes, e.g., butadiene, and vinyl
aromatic compounds, e.g., styrene in the presence of an
organometallic initiator, e.g., n-butyllithium, to produce
copolymers which contain an active metal atom, such as lithium,
on one end of each of the polymer chains. These metal atom-
terminated polymers are then reacted with a coupling agent
which has at least three active sites capable of reacting
with the carbon-metal atom konds on the polymer chains and
replacing the metal atoms on the chains. This results in
polymers which have relatively long branches which radiate
from a nucleus formed by the polyfunctional coupling agent.
Such a method of preparation is described in detail
in Zelinski et al, U.S. Pat.No.3,281,383 dated October 25,1966.
The coupling agents for the radial teleblock copolymers
can be chosen from among polyepoxides, polyisocyanates, polyi-
c~ h
-- 5
8CH-2145
6~
mines, polyaldehydes, polyketones, polyanhydrides, polyesters,
polyhalides and the like. These materials can contain two or
more types of functional groups, such as the combination of
epoxy and aldehyde groups or isocyanate and halide groups.
The coupling agents are described in detail in the above mentioned
U.S. Pat. No. 3,281,383 dated October 25, 1966.
The conjugated dienes of the radial teleblock copolymer
include compounds such as 1,3-butadiene, isoprene, 2,3-dimethyl-
1,3-butadiene, 1-3-pentadiene, 3-butyl-1,3-octadiene, and the
like. The vinyl aromatic polymers may be prepared from vinyl
aromatic compounds of Formula II. They include styrene, 1-
vinylnaphthalene, 2-vinylnaphthalene and the alkyl, cycloalkyl,
aryl, alkaryl and aralkyl derivatives thereof. Examples in-
clude 3-methylstyrene, 4-n-propylstyrene, 4-cyclohexylstyrene,
4-4-(4-phenyl-n-butyl) styrene, and the like.
In preferred compositions, the radial teleblock co-
polymer will be a radial teleblock copolymer of styrene and
butadiene, with terminal blocks derived from styrene, and a
coupling agent selected from epoxidized polybutadiene,
SiCI4 or mixtures thereof. Especially preferred epoxidized
polybutadiene coupling agents are available commercially
under the trade names Oxiron 2000 and Oxiron 2001.
The molecular weight of the radial teleblock copolymer
and the ratios of the co-monomers thereof can vary broadly.
In preferred embodiments the molecular weight of the radial
teleblock copolymer will be from about 100,000 to about
350,000, and will comprise from 1 to 45 parts by weight of
the vinyl aromatic compound and from 99 to 55 parts by weight
of the conjugated diene, based on the weight of the radial
teleblock copolymer. The amount of coupling agent is the co-
polymer will depend on the particular agent and the amount of
organometallic initiator used. Generally, relatively small
c ~
8CH-2145
amounts of coupling agent, e.g., from about 0.1 to 1 part by
weight per 100 parts of resin are employed.
Preferred radial teleblock copolymers are Solprene 406
(containing about 60 parts by weight of butadiene units and
about 40 parts by weight of styrene units), Solprene 411
(containing about 70 parts by weight of butadiene units and
about 30 parts by weight of styrene units), Solprene 414
(containing about 60 parts by weight of butadiene units and
about 40 parts by weight of styrene units), and S411P (con-
taining about 70 parts by weight of butadiene units and about30 parts by weight of styrene units). These materials also
include a realively minor amount of coupling agent, e.g.,
less than 1 part by weight of coupling agent per 100 parts
of polymer.
As noted above, the compositions of this invention can
also include a polyphenylene ether resin. The polypheny-
lene ether resins are preferably of the formula:
wherein the oxygen ether atom of one unit is connected to
the benzene nucleus of the next adjoining unit, n is a positive
integer and is at least 50 and each Q is a monovalent sub-
stituent selected from the group consisting of hydrogen,
halogen, hydrocarbon radicals free of a tertiary alpha-carbon
atom, halohydrocarbon radicals having at least two carbon
atoms between the halogen atom and the phenyl nucleus,
hydrocarbonoxy radicals and halohydrocarbonoxy radicals having
at least two carbon atoms between the halogen atom and the
-- 7 --
8CH-2145
6~
phenyl nucleus.
Examples of polyphenylene ethers corresponding to the
above formula can be found in Hay, u.S. Pat.3,306,874 and
u.S. Pat 3,306,875 both dated February 28, 1967 and in
Stamatoff, U.S. Pat Nos. 3,257,357 and 3,257,358 both dated
June 21, 1966.
For purposes of the present invention, an especially
preferred family of polyphenylene ethers includes those
having alkyl substitution in the two positions ortho to the
oxygen ether atom, i.e., those of the above formula wherein
each Q is alkyl, most preferably having from 1 to 4 carbon
atoms. Illustrative members of this class are: poly(2,6-
dimethyl-1,4-phenylene)ether; poly(2,6-diethyl-1,4-phenylene)
ether; poly (2-methyl-6-ethyl-1,4-phenylene)ether; poly(2-
methyl-6-propyl-1,4-phenylene)ether; poly(2,6-dipropyl-1,
4-phenylene)ether; poly(2-ethyl-6-propyl-1,4-phenylene)
ether; and the like. The most preferred polyphenylene ether
resin is poly(2,6-dimethyl-1,4-phenylene)ether, preferably
having an intrinsic viscosity of about 0.5 deciliters per
gram as measured in chloroform at 25 C.
The components of the compositions of this invention
are combinable in a wide range of proportions. The com-
positions can comprise, for instance, from about 5 to about
95, preferably from about 40 to about 90 parts by weight
of (i) the copolymer of a vinyl aromatic compound and an
~ , ~-unsaturated cyclic anhydride, and from about 95 to
about 5, preferably from about 60 to about 10, parts by weight
of (ii) the radial teleblock copolymer.
When a polyphenylene ether resin is also used, the com-
positions will preferably include from about 5 to about 95,preferably from about 40 to about 90 parts by weight of the
copolymers of a vinyl aromatic compound and an ~ , ~-unsaturated
-- 8
~ 6~ 8CH-2145
cyclic anhydride, from about 95 to about 5, preferably from
about 60 to about 10 parts by weight of the radial tele-
block copolymer, and preferably from about 1 to about 75 parts
by weight of a polyphenylene ether resin.
The compositions of the invention can also include other
ingredients, such as flame retardants, extruders, processing
aids, pigments, stabilizers and the like, for their con-
ventionally employed purposes. Reinforcing fillers, in
amounts sufficient to impart reinforcement, can be used, such
as aluminum, iron or nickel, and the like, and non-metals,
such as carbon filaments, silicates, such as acicular calcium
silicate, asbestos, titanium dioxide, potassium titanate and
titanate whiskers, glass flakes and fibers.
The preferred reinforcing fillers are of glass. In
general, best properties will be obtained if glass filaments
are employed in amounts of from about 10 to about 40% by
weight, based on the combined weight of glass and resin.
However, higher amounts can be used.
The compositions of the invention may be prepared by
blending the components in a Henschel mixer and compounding
the mixture on a twin-screw 28 mm Werner-Pfleiderer ex-
truder. Thereafter, the extruder is chopped into pellets and
molded on a Newbury injection molding machine.
The present invention is further illustrated in the
following examples, which are not to be construed as
limiting. All parts are by weight.
Blends of styrene-maleic anhydride copolymer, styrene-
butadiene radial teleblock copolymer and poly(2,6-dimethyl-1,
4-phenylene) ether resin were prepared by blending the com-
ponents in a Henschel mixer and thereafter compounding themixture on a twin-screw 28 mm Werner-Pfleiderer extruder.
Thereafter the extruder was chopped into pellets and molded
g
8CH-2145
~693
on a Newbury injection molding machine. The compositions are
shown below:
Components 1 2 3 4 5 6
.
Styrene-maleic anhydride
copolymera 100 70 60 -- -- --
Rubber-modified styrene- d
maleic anhydride copolymer -- -- -- 100 80 70
Styrene-butadiene racdial
teleblock copolymer -- 30 30 -- -- --
10 Styrene-butadiene r~dial
teleblock copolymer -- -- -- -- 20 20
Poly(2,6-dimethyl-1,4-
phenylene) ethere -- -- 10 -- -- 10
a Dylark 232, Arco Polymers
b Dylark 240, Arco Polymers
c Solprene 406, Phillips Petroleum Co.
d Soleprene 414, Phillips Petroleum Co.
e PPO, General Electric Co., having an I.V.
of about 0.5 as measured in CHC13 at 25C.
The above compositions were molded into test bars and
tested according to ASTM procedures to evaluate physical
properties.
Table 1
Property 1 2 3 4 5 6
Tensile yield (psi) 9300 5600 550078005700 5900
Tensile strength (psi) 9300 480048006400 4900 5300
Elongation (~) 9 4634 3148 38
Izod Imp. Strength
(ft. lb./in.n) 0.43 3.03.7 1.81.7 3.4
30 Gardner Imp. Strength
(in.-lbs.) ~10 10373 <1010 30
-- 10 --
,
3B~9~ 8CH-2145
The test results show elongation and impact strength
are improved by the addition of the radial teleblock co-
polymer to a styrene-maleic anhydride resin. The presence
of the polyphenylene ether resin further enhances the im-
provement in impact strength.
Obviously, other modifications and variations of the -
present invention are possible in the light of the above
teachings. For instance, the compositions may contain other
functional additives, e.g., plasticizers, extenders, lub-
ricants, oxidation inhibitors, flame retardants, pigments,
stabilizers, and the like.
It is, therefore, to be understood that changes may be
made in the particular embodiments described above, which
are within the full intended scope of the invention as ~ -
defined in the appended claims.
-- 11 --
