Moldable polyblends of polyolefins and styrenic resins

A polyblend composition containing an olefin polymer, a rubber-modified styrenic resin, and a block copolymer compatibilizer is disclosed. In a preferred embodiment, a crystalline propylene polymer, a styrene/maleic anhydride random thermoplastic copolymer modified with a grafted styrene/butadiene rubber, and a hydrogenated styrene/butadiene block copolymer are intimately mixed to form a useful thermoplastic polyblend.

FIELD OF THE INVENTION 
This invention relates to polyblend compositions useful as engineering 
resins for the preparation of molded articles. More particularly, this 
invention pertains to thermoplastic polyblend compositions having improved 
impact properties. 
SUMMARY OF THE INVENTION 
A moldable polyblend composition comprised of an olefin polymer, a 
rubber-modified styrenic resin, and a compatibilizer is provided by this 
invention. The invention also provides filled thermoplastic compositions 
comprised of the polyblend composition and a filler. 
At least about 50 weight percent of the olefin polymer is a crystalline 
propylene polymer. The olefin polymer comprises from about 40 to 80 weight 
percent of the polyblend. 
The rubber-modified styrenic resin, which comprises from about 5 to 40 
weight percent of the polyblend, is comprised of from about 65 to 95 
weight percent of a random thermoplastic copolymer and from about 5 to 35 
weight percent of a grafted rubber selected from the group consisting of 
ethylene propylene diene monomer (EPDM) rubbers and conjugated diene 
rubbers. The random thermoplastic copolymer contains from about 35 to 99 
weight percent of a vinyl aromatic monomer, from about 1 to 30 weight 
percent of an .alpha.,.beta.-unsaturated dicarboxylic acid derivative, and 
from 0 to about 35 weight percent of an ethylenically unsaturated monomer 
selected from the group consisting of unsaturated nitriles, 
.alpha.,.beta.-unsaturated monocarboxylic acids, C.sub.1 -C.sub.4 alkyl 
esters of .alpha.,.beta.-unsaturated monocarboxylic acids, and mixtures 
thereof. In a preferred embodiment, the random thermoplastic copolymer is 
a styrene/maleic anhydride copolymer. 
The compatibilizer comprises from about 3 to 40 weight percent of the 
polyblend and may be selected from the group consisting of mono-vinyl 
aromatic monomer/conjugated diene block copolymers, hydrogenated 
mono-vinyl aromatic monomer/conjugated diene block copolymers, and 
mixtures thereof. 
The polyblends of this invention have remarkably improved impact properties 
as compared to prior art polyblends of olefin polymers and styrenic 
copolymers in which the copolymer was not modified with a grafted rubber. 
The magnitude of improvement in impact properties was unexpected in view 
of the relatively minor enhancement in such properties obtainable by 
simple blending of ungrafted rubber into the polyblends. The substantially 
reduced brittleness of the polyblends of this invention is also surprising 
in that the grafted rubber of the styrenic resin copolymer component 
constitutes only a small portion of the overall polyblend composition. 
Also unforeseen was the minimal effect of using a rubber-modified styrenic 
resin on the other physical properties of the polyblend composition. 
Tensile and flexural strength are not compromised while only insignificant 
changes in flexural modulus (stiffness) and heat resistance are observed. 
Normally, major improvements in the impact properties of a thermoplastic 
resin are accompanied by substantial degradation of certain other 
properties of the resin.

DETAILED DESCRIPTION OF THE INVENTION 
A. Olefin Polymer 
The moldable polyblend compositions of this invention can include from 
about 40 to 80 weight percent, preferably from about 45 to 80 weight 
percent, of an olefin polymer. At least about 50 weight percent (more 
preferably, at least about 60 weight percent) of the olefin polymer is a 
crystalline propylene polymer. The crystalline propylene polymer may be 
either a homopolymer of propylene or a copolymer of propylene with a minor 
amount (preferably, from about 1 to 20 weight percent) of another olefin 
such as ethylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, and 
the like. The apparent crystalline melting point of the crystalline 
propylene polymer is preferably from about 140 to 180.degree. C.; it is 
not necessary for this component to be completely crystalline (i.e., 
isotactic). 
In addition to the crystalline propylene polymer, the olefin polymer 
component of the polyblend composition may include polymers and copolymers 
of other unsaturated monomers. Examples of such materials include, but are 
not limited to polyethylene (low or high density), poly(1-butene), 
poly(4-methyl-1-pentene), copolymers of 4-methyl-1-pentene with linear or 
branched .alpha.-olefins, poly (3-methyl-1-butene), 
ethylene-propylene-diene polymers (EPDM polymers), copolymers of ethylene 
and 1-butene, copolymers of ethylene and vinyl acetate, copolymers of 
ethylene and ethyl acrylate, and the like and their mixtures. 
Particularly useful olefin polymers include impact-modified polypropylenes, 
which are blends of a crystalline propylene polymer (homopolymer or 
copolymer) with an EPDM (ethylene propylene diene monomer) copolymer, an 
ethylene/propylene copolymer, and/or a high density polyethylene. The use 
of an impact-modified polypropylene having from about 60 to 92.5 weight 
percent crystalline propylene polymer, from about 5 to 27 weight percent 
EPDM, and from about 2.5 to 13 weight percent high density polyethylene is 
especially desirable. Mixtures of propylene homopolymers and 
ethylene/propylene random or block copolymers also may be employed to 
advantage in the present polyblends. 
Methods of preparing the olefin polymers described above are well-known in 
the art. General descriptions of such methods may be found, for example, 
in "Propylene Polymers" Encyclopedia of Polymer Science and Engineering 
2nd Ed., Wiley-Interscience, Vol. 13, pp. 464-530 (1988) and "Olefin 
Polymers" Kirk-Othmer Encyclopedia of Chemical Technology 3rd Ed., 
Wiley-Interscience, Vol. 16, pp. 385-479(1981). The teachings of these 
reviews are incorporated herein by reference. 
Illustrative examples of suitable commercially available propylene polymers 
include Norchem.RTM. NPP8006-GF (a general purpose propylene homopolymer 
sold by Quantum Chemical Corp.), Norchem.RTM. NPP8752-HF {a high impact 
propylene copolymer sold by Quantum Chemical Corp.), Escorene.RTM. 1052 (a 
general purpose propylene homopolymer sold by Exxon Chemical Co.), 
Huntsman.RTM. 7525 (a high impact propylene copolymer sold by Huntsman 
Polypropylene Corp.), Pro-Fax.RTM. SB786 (a medium impact propylene 
homopolymer sold by Himont U.S.A., Inc.), Unipol.RTM. 7C56 (a high impact 
propylene copolymer sold by Shell Chemical Co.), Pro-Fax.RTM. 6323 (a 
general purpose propylene homopolymer sold by Himont U.S.A., Inc.) and 
Rexene 17/57512A (a high impact propylene copolymer sold by Rexene 
Products Co.). 
The number average molecular weight of the olefin polymer component of the 
polyblends of this invention is preferably above about 10,000 and more 
preferably is greater than about 50,000. The olefin polymer preferably has 
a melt flow rate of less than about 15 g/10 min. (Condition L). Olefin 
polymers having melt flow rates of less than about 12 g/10 min. are 
especially favored. Prior efforts to prepare polyblends of high molecular 
weight polypropylene (i.e., polypropylene with a melt flow rate of less 
than 15 g/10 min.) and non-rubber-modified styrene/maleic anhydride 
copolymers were unsuccessful due to problems with moldability and the 
appearance of the molded articles (Jpn. Pat. No. 63-205341). In contrast, 
moldings having excellent surface appearance and properties are readily 
obtained by conventional processing using the polyblends of this 
invention. Without wishing to be bound by theory, it is believed that the 
presence of the grafted rubber in the styrenic resin component is 
responsible for the greater compatibility and processability of the 
present polyblends as compared to the prior art polyblends. The ability to 
use high molecular weight olefin polymers in the polyblends of this 
invention is thought to make possible the observed improvements in impact 
properties. Melt strength is also expected to be improved by the use of 
higher molecular weight olefin polymers. 
B. Rubber-Modified Styrene Resin 
The moldable polyblend compositions of this invention additionally are 
comprised of from about 5 to 40 weight percent (more preferably, from 
about 10 to 30 weight percent) of a rubber-modified styrenic resin. The 
rubber-modified styrenic resin contains from about 65 to 95 weight percent 
(more preferably, from about 75 to 90 weight percent) of a random 
thermoplastic copolymer and from about 5 to 35 weight percent (more 
preferably, from about 10 to 25 weight percent) of a grafted rubber. 
The random thermoplastic copolymer is comprised of from about 35 to 99 
weight percent of a vinyl aromatic monomer, from about 1 to 30 weight 
percent of an .alpha.,.beta.-unsaturated dicarboxylic acid derivative, and 
from 0 to 35 weight percent of a third ethylenically unsaturated monomer. 
It is preferred that the random thermoplastic copolymer be comprised of 
from about 70 to 99 weight percent vinyl aromatic monomer and from about 1 
to 30 weight percent .alpha.,.beta.-unsaturated dicarboxylic acid 
derivative. The weight ratio of vinyl aromatic to 
.alpha.,.beta.-unsaturated dicarboxylic acid derivative is more preferably 
from about 75:25 to 95:5. 
Although any suitable vinyl aromatic monomer may be employed in the random 
thermoplastic copolymer, styrene is the preferred monomer because of its 
low cost and availability. Examples of other vinyl aromatic monomers which 
can be used include, but are not limited to, ar-methyl styrene, ar-ethyl 
styrene, ar-tertbutyl styrene, ar-chloro styrene, alpha-methyl styrene, 
divinyl benzene, vinyl benzyl chloride, and vinyl naphthalene, as well as 
other alkyl- or halo-substituted styrenes. Mixtures of vinyl aromatic 
monomers can be used. 
The preferred .alpha.,.beta.-unsaturated dicarboxylic acid derivative is an 
.alpha.-.beta.-unsaturated dicarboxylic acid anhydride. Exemplary 
.alpha.,.beta.-unsaturated dicarboxylic acid anhydrides include itaconic 
anhydride, citraconic anhydride, ethyl maleic anhydride, methyl itaconic 
anhydride, chloromaleic anhydride, bromomaleic anhydride, 
tetrahydrophthalic anhydride, and, most preferably, maleic e. However, 
other .alpha.,.beta.-unsaturated dicarboxylic acid derivatives may also be 
employed including .alpha.,.beta.-unsaturated dicarboxylic acids such as 
maleic or fumaric acid and maleimides such as N-methyl maleimide, N-phenyl 
maleimide, N-tribromo-phenyl maleimide, and the like. If desired, mixtures 
of .alpha.,.beta.-unsaturated dicarboxylic acid derivatives can be used. 
The third ethylenically unsaturated monomer may be selected from the group 
consisting of unsaturated nitriles such as acrylonitrile and 
methacrylonitrile, .alpha.,.beta.-unsaturated monocarboxylic acids such as 
acrylic acid and methacrylic acid, C.sub.1 -C.sub.4 alkyl esters of 
.alpha.,.beta.-unsaturated mono-carboxylic acids such as methyl 
methacrylate and ethyl acrylate, and mixtures thereof. Terpolymers of 
styrene, maleic anhydride, and acrylonitrile or methyl methacrylate are 
particularly preferred. 
In a preferred embodiment of this invention, the random thermoplastic 
copolymer is a styrene/maleic anhydride copolymer. The random 
thermoplastic copolymer preferably has a number average molecular weight 
of from about 30,000 to about 500,000 or a melt flow rate (Condition L) of 
from about 0.1 to 10 g/10 min. 
The rubber-modified styrenic resin is additionally comprised of from about 
5 to 35 weight percent (preferably, from about 10 to 25 weight percent) of 
a rubber grafted on the random thermoplastic copolymer. The grafted rubber 
is selected from the group consisting of conjugated diene rubbers and 
ethylene propylene diene monomer rubbers. 
Conjugated diene rubbers suitable for use in this invention preferably 
contain at least about 50 weight percent of a conjugated diene and have 
glass transition temperatures less than about 0.degree. C. (more 
preferably, less than about -20.degree. C.). Such rubbers include 
homopolymers, random copolymers, and block copolymers of conjugated 
1,3-dienes such as 1,3-butadiene (a preferred diene), isoprene, 
chloroprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and the like. The 
conjugated diene rubber is preferably selected from the group consisting 
of mono-vinyl aromatic monomer/conjugated diene block copolymers, 
mono-vinyl aromatic monomer/conjugated diene random copolymers, conjugated 
diene homopolymers, and mixtures thereof. 
The conjugated diene rubber may contain one or more copolymerizable 
ethylenically unsaturated monomers. Most preferably, the comonomer is a 
mono-vinyl aromatic monomer such as styrene, ar-methyl styrene, ar-ethyl 
styrene, ar-tert-butyl styrene, ar-chlorostyrene, alpha-methyl styrene, 
vinyl benzyl chloride, vinyl naphthalene, and the like and mixtures 
thereof. Other copolymerizable ethylenically unsaturated monomers may be 
employed, however, including unsaturated nitrile monomers such as 
acrylonitrile and methacrylonitrile, alkyl acrylates such as methyl 
methacrylate, methyl acrylate, butyl acrylate, or 2-ethylhexyl 
methacrylate, acrylamides such as acrylamide, methacrylamide, or 
butylacrylamide, unsaturated ketones such as vinyl methyl ketone or methyl 
isopropenyl ketone, .alpha.-olefins such as ethylene or propylene, vinyl 
esters such as vinyl acetate or vinyl stearate, vinyl heterocyclic 
monomers such as vinyl pyridine, vinyl and vinylidene halides such as 
vinyl chloride or vinylidene chloride, and the like and mixtures thereof. 
In a preferred embodiment of this invention, the comonomer used in 
combination with the 1,3-conjugated diene is the same as the vinyl 
aromatic monomer component of the random thermoplastic copolymer of the 
rubber modified styrenic resin. 
Exemplary conjugated diene rubbers suitable for grafting onto the random 
thermoplastic copolymer include styrene/butadiene and styrene/isoprene 
block copolymers. Such block copolymers may be linear, radial, or branched 
in structure. Linear block copolymers may have an ABA, AB(AB).sub.n A, 
(AB).sub.n, or similar structure wherein A represents a block of the 
mono-vinyl aromatic monomer, B represents a block of the conjugated diene 
and n is an integer of 1 to 10. Radial block copolymers may have an 
(AB).sub.n X structure, wherein X is a multi-valent linking agent. Block 
copolymers of these types are well-known. Details concerning their 
preparation, structure, and properties may be found, for example, in the 
following references: "Styrene-Diene Block Copolymers" Encyclopedia of 
Polymer Science and Technology 1st Ed., Suppl., Wiley, pp 508-530(1971), 
K. E. Snavely et al, Rubber World 169, 45(1973), and "Thermoplastic 
Elastomers" Kirk-Othmer Encyclopedia of Chemical Technology 3rd., Vol. 8, 
Wiley-Interscience, pp 627-632(1981). 
The following U.S. patents, incorporated herein by reference, further 
describe such block copolymer conjugated diene rubbers: U.S. Pat. Nos. 
3,937,760, 3,231,635, 3,265,765, 3,198,774, 3,078,254, 3,244,644, 
3,280,084, 3,954,452, 3,766,301, 3,281,383, 4,640,968, 4,503,188, 
4,485,210, 4,390,663, 4,271,661, and 4,346,193. Suitable block copolymers 
are also presently available from commercial sources. Examples of 
commercially available block copolymer rubbers include Stereon.RTM. 840A 
(a linear graded styrene/butadiene multi-block copolymer containing about 
43% styrene and having a number average molecular weight of about 60,000, 
sold by Firestone Synthetic Rubber and Latex Co.), Stereon.RTM. 730A (a 
stereospecific tapered styrene/butadiene block copolymer containing a 
total of 30% styrene with 21% styrene in block form and having a number 
average molecular weight of 140,000, sold by Firestone Synthetic Rubber 
and Latex Company), Kraton.RTM. D-1101 (a linear styrene/butadiene/styrene 
triblock copolymer containing 31% styrene, sold by Shell Chemical), 
Kratone.RTM. D-1107 (a linear styrene/isoprene/styrene triblock copolymer 
containing 14% styrene, sold by Shell Chemical), and Kraton.RTM. D-1184 (a 
branched styrene/butadiene multiblock copolymer containing 30% styrene, 
sold by Shell Chemical). 
Also suitable for use as conjugated diene rubbers in the rubber-modified 
styrenic resin component of this invention are random copolymers of 
mono-vinyl aromatic monomers and conjugated dienes. A particularly 
preferred conjugated diene rubber of this type is styrene/butadiene rubber 
(SBR). Homopolymers of conjugated dienes such as polybutadiene and 
polyisoprene may also be employed as the grafted rubber. All such rubbers 
are well-known in the art and are described, for example, in "Butadiene 
Polymers" Encyclopedia of Polymer Science and Engineering 2nd Ed., 
Wiley-Interscience, Vol. 2, pp. 537-590(1988), the teachings of which are 
incorporated by reference herein in their entirety. 
The grafted rubber may alternatively be an ethylene propylene diene monomer 
(EPDM) rubber. Such materials are well-known in the art and are random 
copolymers of ethylene, at least one C.sub.3 -C.sub.6 .alpha.-olefin 
(preferably propylene), and at least one nonconjugated diene. The 
nonconjugated diene may be a linear aliphatic diene of at least six carbon 
atoms which has either two terminal double bonds or one terminal double 
bond and one internal double bond. Alternatively, the nonconjugated diene 
may be a cyclic diene where one or both of the double bonds are part of a 
carbocyclic ring. The structure of the EPDM rubber may be altered as 
desired, particularly with respect to branching, by the selection of 
particular nonconjugated dienes as is well known in the art. Particularly 
preferred non-conjugated dienes include 1,4-hexadiene, dicyclopentadiene, 
vinyl norbornene, norbornadiene, and 5-ethylidene-2-norbornene. 
Preferably, the EPDM rubber contains from about 40 to 90 mole percent 
ethylene and 0.1 to 7.5 mole percent nonconjugated diene, with the 
remainder being propylene. Additional information regarding EPDM rubbers 
may be found in "Ethylene-Propylene Elastomers" Encyclopedia of Polymer 
Science and Engineering 2nd Ed., Wiley-Interscience, Vol. 6, p. 522(1986), 
the teachings of which are incorporated herein by reference. 
Examples of suitable commercially available EPDM rubbers include 
Royalene.RTM. 501 (a product of Uniroyal Chemical), Nordel.RTM. 2744 (a 
product of E. I. duPont de Nemours), and Epsyn.RTM. 40-A (a product of 
Copolymer Rubber and Chemical Corp.). Functionalized EPDM rubbers, 
including rubbers having pendant hydroxy, amido, amino, or thio groups, 
may also be employed. 
It is important that the rubber component of the styrenic resin be 
chemically grafted onto the random thermoplastic copolymer and not simply 
physically mixed with the copolymer. The exceptionally high impact 
properties of the polyblends of this invention cannot be realized by 
merely blending the rubber with the random vinyl aromatic 
monomer/.alpha.,.beta.-carboxylic acid derivative copolymers. 
Any suitable procedure for preparing the rubber-modified styrenic resin may 
be employed. For example, the vinyl aromatic monomer, 
.alpha.,.beta.-unsaturated dicarboxylic acid derivative, and other 
ethylenically unsaturated monomer (if any) may be copolymerized in the 
presence of the rubber in such a manner as to result in grafting of the 
rubber onto the resulting random thermoplastic copolymer. This approach is 
illustrated in U.S. Pat. Nos. 3,919,354 and 4,097,551, the teachings of 
which are incorporated herein by reference. The rubber is first dissolved 
in the vinyl aromatic monomer before free radical polymerization is 
initiated. The .alpha.,.beta.-unsaturated carboxylic acid derivative is 
then added continuously to the polymerizing mixture at a rate sufficient 
to maintain a low concentration of the .alpha.,.beta.-unsaturated 
dicarboxylic acid derivative. Methods for preparing rubber-modified 
terpolymers of vinyl aromatic monomers, unsaturated dicarboxylic acid 
anhydrides, and unsaturated nitriles are described in U.S. Pat. No. 
4,223,096, incorporated herein by reference. Other methods may also be 
employed, including reactive blending of the rubber with a pre-formed 
copolymer. Functional groups such as hydroxy, amido, amino, or thio may be 
present on the rubber to promote grafting with the random thermoplastic 
copolymers. Such methods are described, for example, in U.S. Pat. Nos. 
4,721,752 and 4,742,116, incorporated herein by reference. 
Especially preferred for use as the rubber-modified styrenic resins in the 
polyblends of this invention are resins in which the random thermoplastic 
copolymer is a styrene/maleic anhydride copolymer and the rubber is a 
styrene/butadiene block copolymer. Suitable commercially available 
rubber-modified styrenic resins include Dylark.RTM. 250, Dylark.RTM. 350, 
Dylark.RTM. 378, and Dylark.RTM. 700 (all products of ARCO Chemical 
Company). 
C. Compatibilizer 
The moldable polyblends of this invention are additionally comprised of 
from about 3 to 40 weight percent of a compatibilizer selected from the 
group consisting of mono-vinyl aromatic monomer/conjugated diene block 
copolymers, hydrogenated mono-vinyl aromatic monomer/conjugated diene 
block copolymers, and mixtures thereof. More preferably, the amount of 
compatibilizer is from about 3 to 30 weight percent of the total 
polyblend. 
The mono-vinyl aromatic monomer may be one or more compounds containing a 
vinyl functional group attached directly to an aromatic ring. Exemplary 
mono-vinyl aromatic monomers are styrene (the preferred such monomer), 
ar-alkyl styrenes such as p-methyl styrene, p-tert-butyl styrene, and 
o,p-dimethyl styrene, ar-halo styrenes such as o-chloro styrene and 
o,p-dichloro styrene, vinyl benzyl chloride, vinyl naphthalene, and 
alphamethyl styrene and the like and mixtures thereof Although the 
preferred conjugated diene is 1,3-butadiene, other such compounds as 
chloroprene, isoprene, 2,3-dimethyl butadiene, 1,3-pentadiene, and the 
like and their mixtures may also be employed. 
Compatibilizers suitable for use in this invention will contain at least 
one "soft" rubbery B block comprised predominantly of repeating units of 
one or more conjugated dienes (or their hydrogenated derivatives) and at 
least one "hard" thermoplastic A block comprised predominantly of 
repeating units of one or more mono-vinyl aromatic monomers. The "soft" 
block has a glass transition temperature below about 0.degree. C.; more 
preferably, the Tg is less than about -20.degree. C. The compatibilizer 
may have a linear, branched, or radial structure. Linear compatibilizers 
can have an ABA, AB(AB).sub.n A, (AB).sub.n, or similar structure where n 
is an integer from 1 to 10. Radial compatibilizers may have an (AB).sub.n 
X structure, wherein X is a multi-valent linking agent. In a preferred 
embodiment, the compatibilizer has a linear triblock structure and is a 
styrene/butadiene or hydrogenated styrene/butadiene block copolymer. The 
amount of styrene in such compatibilizers preferably varies from about 10 
to 60 weight percent and the overall molecular weight is preferably in the 
range of from about 35,000 to 300,000. 
Block copolymers suitable for use as compatibilizers in the polyblends of 
this invention are well-known. Such materials are described, for example, 
in "Styrene-Diene Block Copolymers" Encyclopedia of Polymer Science and 
Technology 1st Ed., Suppl., Wiley, pp. 508-570(1971), K. E. Snavely et al 
Rubber World 169, 45(1973), and "Thermoplastic Elastomers" Kirk-Othmer 
Encyclopedia of Chemical Technology 3rd Ed., Vol. 8, Wiley-Interscience, 
pp. 627-632(1981). 
The following exemplary U.S. patents, incorporated herein by reference, 
describe the preparation and properties of suitable mono-vinyl aromatic 
monomer/conjugated diene block copolymers useful as compatibilizers: U.S. 
Pat. Nos. 3,265,765, 3,937,760, 3,251,905, 3,287,333, 3,281,383, 
3,692,874, 4,346,193, 4,371,661, 4,390,663, 4,485,210, 4,503,188, 
4,640,968, 3,078,254, 3,778,490, 3,639,521, 3,903,201, 3,149,182, 
3,231,635, 3,390,207, 3,567,798, 3,594,452, 3,639,523, and 3,890,408. 
Compatibilizers which are hydrogenated mono-vinyl aromatic 
monomer/conjugated diene block copolymers may be obtained by the methods 
given in the following U.S. patents, incorporated herein by reference: 
U.S. Pat. Nos. 3,595,942, 3,700,633, 3,333,024, 3,706,817, 3,415,759, 
3,507,934, 3,644,588, 3,670,054, 3,700,748, 3,792,005, 3,792,127, and U.S. 
Re. 27,145. 
Commercially available block copolymers may also be used as polyblend 
compatibilizers, including, for example, Kraton.RTM. G-1652 (a linear 
hydrogenated styrene/butadiene triblock copolymer containing 29% styrene, 
sold by Shell Chemical), Kraton.RTM. G-1657X (a linear hydrogenated 
styrene/butadiene triblock copolymer containing 13% styrene and 35% 
diblock copolymer, sold by Shell Chemical), SOL T-168 (a radial 
styrene/butadiene block copolymer containing 43% styrene, sold by 
Enichem), and SOL T-192 (a styrene/isoprene block copolymer containing 25% 
styrene, sold by Enichem). 
D. Method of Preparing Polyblend 
The blending of the olefin polymer, rubber-modified styrenic resin, and 
compatibilizer may be performed in any manner that produces a 
compatibilized polyblend. The resulting compatibilized polyblend is 
dimensionally stable and does not exhibit delamination upon molding and in 
subsequent use. One method is to dissolve the polyblend components in a 
common solvent and then precipitate the polyblend by combining the 
solution with a non-solvent in which none of the components are soluble. 
However, the preferred procedure is to intimately mix the components in 
the form of granules and/or powder in a high shear mixer at an elevated 
temperature. Intimate mixing may be accomplished by the use of high shear 
extrusion compounding machines such as single or twin screw compounding 
extruders or thermoplastic extruders having preferably at least a 20:1 L/D 
ratio and a compression ratio of about 3 or 4:1. The polyblend may be 
either supplied directly to a molding machine or converted into pellet 
form for further processing. 
The mixing temperature is selected in accordance with the particular 
components to be blended. For example, generally it will be desirable to 
select a melt blending temperature above the melting or softening point of 
the component having the highest melting or softening point, but below the 
temperature at which thermal degradation of any component becomes 
significant. Blending temperatures between about 190.degree. C. and 
300.degree. C. are generally suitable. 
The order of blending is not critical. For example, all the components of 
the polyblend may be combined in a single step or, alternatively, the 
compatibilizer may be pre-blended with the olefin polymer. In yet another 
variation, a portion of the compatibilizer may be pre-blended with the 
olefin polymer and the remainder added when preparing the final polyblend. 
Other such variations will be apparent to one skilled in the art. 
The moldable polyblends of this invention may be combined with any of the 
standard thermoplastic additives such as fillers, reinforcing agents, 
colorants, lubricants, anti-static agents, stabilizers, fire retardants, 
anti-oxidants, anti-blocking agents, and/or other compounding ingredients. 
Examples of fillers which may be blended with the polyblends of this 
invention include, but are not limited to, mineral fillers such as calcium 
carbonate, dolomite, silicates, silicas, talc, kaolin, mica, magnesium 
phosphate, barium sulfate, titanium oxide, and the like, organic fillers 
such as carbon black, and fibrous fillers such as glass fiber (including 
strands and chopped fiber), carbon fiber, graphite fiber, aromatic 
polyamide fiber, ceramic fiber, and boron fiber. The weight ratio of 
polyblend to filler is preferably from about 0.5:1 to 20:1. 
From the foregoing description, one skilled in the art can readily 
ascertain the essential characteristics of this invention, and, without 
departing from the spirit and scope thereof, can make various changes and 
modifications of the invention to adapt it to various usages, conditions, 
and embodiments. 
The following examples further illustrate the moldable polyblends of this 
invention, but are not limitative of the invention in any manner 
whatsoever. 
EXAMPLES 
A. Description of Polyblend Components 
Olefin polymer A-1 is a 75:25 blend of Escorene.RTM. 1042 polypropylene (a 
propylene homopolymer having a melt flow rate of 1.9 g/10 min., sold by 
Exxon Chemical) and IM-7565 impact modifier [a 2:1 blend of EPDM 
(containing a 1:1 ratio of ethylene to propylene) and HDPE (high density 
polyethylene), sold by Uniroyal Chemical Company]. 
Olefin polymer A-2 is an 85:15 blend of Escorene.RTM. 1042 polypropylene 
and IM-7565 impact modifier. 
Olefin polymer A-3 is Escorene.RTM. 1042. 
Olefin polymer A-4 is Marlex.RTM. HGH-050, a propylene homopolymer having a 
melt flow rate of 5.0 g/10 min., sold by Phillips. 
Olefin polymer A-5 is Tenite.RTM. P64MZ-007, a propylene copolymer having a 
melt flow rate of 8.0 g/10 min., sold by Eastman. 
Olefin polymer A-6 is Fina.RTM. 3662, a propylene homopolymer having a melt 
flow rate of 12 g/10 min., sold by Fina Oil. 
Olefin polymer A-7, is Norchem.RTM. NPP8404HJ, a propylene copolymer having 
a melt flow rate of 3, sold by Quintum Chemical Corp. 
Styrenic resin B-1 is a styrene/maleic anhydride random copolymer 
containing about 14 weight percent maleic anhydride but no grafted rubber. 
B-1 has a melt flow rate of about 1.6 g/10 min. (Condition L). 
Styrenic resin B-2 is a rubber-modified styrene/maleic anhydride random 
copolymer containing about 13 weight percent maleic anhydride and prepared 
in accordance with the procedures of U.S. Pat. No. 3,919,354. B-2 has a 
melt flow rate of about 1.0 g/10 min. (Condition L) and contains about 15 
weight percent of a grafted styrene/butadiene block copolymer rubber. 
Styrenic resin B-3 is a styrene/maleic anhydride random copolymer having a 
melt flow rate of about 1.5 g/10 min., and containing 10 weight percent 
maleic anhydride and 5 weight percent of Diene.RTM. 35NF (a polybutadiene 
rubber having about 35% cis; 1,4-configuration, sold by Firestone 
Synthetic Rubber and Latex); prepared in accordance with U.S. Pat. No. 
3,919,354. 
Styrenic resin B-4 is a 50/20/15/5 styrene/p-methyl styrene/maleic 
anhydride/citraconic anhydride random copolymer containing about 20 weight 
percent of Krynac.RTM. 34.50 (an acrylonitrile/butadiene rubber containing 
34% acrylonitrile, sold by Polysar); prepared in accordance with U.S. Pat. 
No. 3,919,354. 
Styrenic resin B-5 is a styrene/maleic anhydride random copolymer 
containing 20 weight percent maleic anhydride and 25 weight percent of 
Ameripole.RTM. 4616 (a styrene/butadiene random copolymer rubber 
containing 23.5% styrene, sold by B. F. Goodrich); prepared in accordance 
with U.S. Pat. No 3,919,354. 
Styrenic resin B-6 is a terpolymer containing 65 weight percent styrene, 24 
weight percent maleic anhydride, and 11 weight percent acrylonitrile and 
grafted with 16 weight percent of a polybutadiene rubber; prepared in 
accordance with Example 5 of U.S. Pat. No. 4,223,096. 
Compatibilizer C-1 is Kraton.RTM. G-1652, a linear hydrogenated 
styrene/butadiene block copolymer containing 29% styrene (sold by Shell 
Chemical Company). 
Compatibilizer C-2 is Sol.RTM. T-166, a styrene/butadiene block copolymer 
containing about 30% styrene and having a number average molecular weight 
of about 80,000 (sold by Enichem). 
Compatibilizer C-3 is a star block copolymer containing 40% styrene 
prepared in accordance with Example IV-3 of U.S. Pat. No. 3,281,383. 
Compatibilizer C-4 is Kraton.RTM. D-1111, a linear styrene/isoprene block 
copolymer containing 21% styrene sold by Shell Chemical. 
Compatibilizer C-5 is Kraton.RTM. D-1184, a branched styrene/butadiene 
multi-block copolymer containing 30% styrene sold by Shell Chemical. 
Compatibilizer C-6 is a linear styrene/butadiene block copolymer having a 
calculated average of 5.3 blocks and a 1:3.4 weight ratio of 
styrene:butadiene, prepared according to Example I of U.S. Pat. No. 
3,937,760. 
B. Blending Procedure 
Polyblends were prepared by melt-blending the components shown in Table I 
using an Egan 1.5" single screw/single vent extruder (L/D=24:1) and the 
following conditions: 
______________________________________ 
RPM: 165 
Vacuum: 50 torr 
Screw Type: Stratablend screw 
Hopper Throat: Water-cooled 
Zone Temp. (.degree.F.): 
______________________________________ 
1 470 
2 470 
3 470 
4 470 
Die 470 
______________________________________ 
In Examples 10-12, olefin polymer A-3 was pre-blended with approximately 
one-third of the compatibilizer in a first step, then blended with the 
styrenic resin and the remainder of the compatibilizer in a second step. 
Molded samples for testing of physical properties were obtained by 
injection molding using a Reed 5 oz. 100 ton injection molding machine and 
the following conditions: 
______________________________________ 
Zone 1 470 F 
Zone 2 470 F 
Zone 3 470 F 
Nozzle 465 F 
Inj. Pressure 650 psi 
Hold Pressure 450 psi 
Back Pressure 100 psi 
Mold Close Time 45 sec 
Mold Temp. 120 F 
Screw Speed 60 rpm 
Inj. Forward Setting 8 sec 
Mold Open 8 sec 
Mold Close 45 sec 
Cushion 1/4 inches 
Shot Size 41/8 inches 
Melt Temp. 480 F 
______________________________________ 
The physical properties of the molded samples were measured using standard 
ASTM methods (Table I). 
To illustrate the use of differing proportions of various olefin polymers, 
rubber-modified styrenic resins, and compatibilizers within the scope of 
this invention, polyblends having the compositions shown in Table II 
(Examples 16-19) are prepared using the procedures described for Examples 
1-12. The polyblends are expected to exhibit the beneficial impact 
properties attainable by this invention when molded into thermoplastic 
articles. 
TABLE I 
__________________________________________________________________________ 
EXAMPLE NO. 1* 2 3* 4 5* 6 
__________________________________________________________________________ 
Composition 
A. Olefin Polymer 
A-1 A-1 A-1 A-1 A-1 A-1 
Wt. % 75 75 70 70 70 70 
B. Styrenic Resin 
B-1 B-2 B-1 B-2 B-1 B-2 
Rubber-Modified 
No Yes No Yes No Yes 
Wt. % 20 20 20 20 20 20 
C. Compatibilizer 
C-1 C-1 C-1 C-1 C-2 C-2 
Wt. % 5 5 10 10 10 10 
% Total Rubber.sup.1 
17.6 20.6 21.7 24.7 21.7 24.7 
% Grafted Rubber.sup.2 
0 3 0 3 0 3 
Properties 
Notched Izod (ft-lbs/in) 
2.2 6.3 5.4 10.2 2.2 8.3 
Penetration Impact 
Total Energy (ft-lbs) 
7.1 23.3 10.6 27.9 8.8 25.3 
Max. Load (lbs) 330 440 370 510 310 500 
Tensile Strength @ Yield (psi) 
3800 3300 3450 3100 3400 3100 
Elongation @ Break (%, 2"/min) 
&gt;150 &gt;150 133 &gt;150 33 80 
Flex. Strength @ Yield (psi) 
6250 5200 5600 4600 5600 4900 
Flex. Modulus (psi .times. 1000) 
166 145 150 130 154 137 
DTUL (.degree.F., 264/66 psi) 
140/219 
129/196 140/211 
128/196 129/209 
120/204 
__________________________________________________________________________ 
EXAMPLE NO. 7* 8 9 10* 11* 12 13* 14* 15* 
__________________________________________________________________________ 
Composition 
A. Olefin Polymer 
A-2 A-2 A-2 A-3 A-3 A-3 -- A-1 A-3 
Wt. % 60 65 65 49 49 49 -- 100 100 
B. Styrenic Resin 
B-1 B-2 B-2 B-1 B-1 B-2 B-2 -- -- 
Rubber-Modified 
No Yes Yes No No Yes Yes -- -- 
Wt. % 20 20 20 20 20 20 100 -- -- 
C. Compatibilizer 
C-2 C-2 C-1 C-2 C-1/C-2 
C-2 -- -- -- 
Wt. % 20 15 15 31 10/21 
31 -- -- -- 
% Total Rubber.sup.1 
26 24.5 24.5 31 31 34 15 16.8 0 
% Grafted Rubber.sup.2 
0 3 3 0 0 3 15 0 0 
Properties 
Notched Izod (ft-lbs/in) 
2.6 6.6 13.1 2.6 3.1 10.6 2.7 13.8 0.8 
Penetration Impact 
Total Energy (ft-lbs) 
6.8 27.0 30.3 9.3 5.7 26.3 11 22.0 3.0 
Max. Load (lbs) 270 535 575 380 330 495 
Tensile Strength @ Yield (psi) 
3300 3300 3200 3300 3400 3400 4700 5000 
Elongation @ Break (%, 2"/min) 
45 &gt;150 &gt;150 55 &gt;150 &gt;150 
Flex. Strength @ Yield (psi) 
5400 5200 5200 5400 5300 4800 10,000 
Flex. Modulus (psi .times. 1000) 
143 142 138 144 137 127 366 
DTUL (.degree.F., 264/66 psi) 
133/216 
120/206 
120/201 
130/208 
126/213 
121/206 
207/230 
117/175 
131/210 
__________________________________________________________________________ 
Notes: 
*Comparative example 
.sup.1 % Total rubber [impact modifier (EPDM) in olefin polymer + grafted 
rubber in styrenic resin + compatibilizer] in final polyblend composition 
.sup.2 % Grafted rubber from styrenic resin in final polyblend compositio 
TABLE II 
______________________________________ 
EXAMPLE NO. 16 17 18 19 
______________________________________ 
Olefin Polymer 
A-4 A-5 A-6 A-7 
Wt. % 80 55 60 70 
Styrenic Resin 
B-3 B-4 B-5 B-6 
Wt. % 10 25 35 15 
Compatibilizer 
C-3 C-4 C-5 C-6 
Wt. % 10 20 5 15 
______________________________________ 
C. Discussion 
The polyblends of Examples 2 and 4, containing rubber-modified 
styrene/maleic anhydride random thermoplastic copolymers in accordance 
with this invention, exhibited a two to three-fold increase in notched 
Izod and penetration impact strength as compared to the polyblends of 
Comparative Examples 1 and 3, which contained styrene/maleic anhydride 
copolymer having no grafted rubber. This significant reduction in 
brittleness was achieved with only a minor increase in the total amount of 
rubber in the polyblends. The compatibilizer used in these examples was a 
linear hydrogenated styrene/butadiene block copolymer. 
In Examples 5 and 6, a styrene/butadiene block copolymer containing 30% 
styrene was used as the compatibilizer. Once again, the substitution of a 
rubber-modified styrenic resin for an ungrafted random copolymer resulted 
in an unanticipated improvement in impact properties. Both notched Izod 
and penetration impact strength increased at least about three-fold 
despite only increasing the total amount of rubber from 21.7 to 24.7 
percent of the polyblend. In view of the gains in impact properties 
realized, it was surprising that the heat resistance of the polyblend of 
Example 6 was comparable to that of the polyblend of Comparative Example 
5. 
The benefits and advantages of the present invention are further 
illustrated by comparison of the physical properties obtained for the 
polyblends of Examples 8 and 9 to those of the Example 7 polyblend. In 
Comparative Example 7, an impact-modified polypropylene was blended with a 
styrene/maleic anhydride copolymer containing no grafted rubber. The 
impact strength of the resulting polyblend was relatively poor (2.6 
notched Izod). In Example 8, however, the use of a rubber-modified 
styrene/maleic anhydride copolymer resin of similar anhydride content and 
molecular weight led to a very substantial gain in impact properties. This 
was unexpected in view of the overall reduction in the total amount of 
rubber in the polyblend of Example 8 as compared to that of Example 7 
(24.5 vs. 26%). Moreover, there was no significant reduction in tensile 
strength, flexural strength, flexural modulus, or heat distortion 
resistance despite the greatly reduced brittleness of the polyblend of 
Example 8. Thus, the polyblends of this invention have an outstanding 
overall balance of properties not realized by prior art compositions. The 
remarkable benefits of using a rubber-modified styrenic resin are even 
more surprising in light of the relatively low impact strength of the 
styrenic resin itself (Example 13). 
Still further improvements in impact properties were realized in the 
polyblend of Example 9 by the use of a hydrogenated styrene/butadiene 
block copolymer compatibilizer in place of the non-hydrogenated 
styrene/butadiene block copolymer of Example 8. Once again, the other 
physical properties of the polyblend were not detrimentally affected. 
The polyblends of Comparative Example 10 and Example 12 differ only in the 
use of a rubber-modified styrene/maleic anhydride copolymer as the 
styrenic resin component in Example 12. This substitution, which only 
increased the total amount of rubber in the polyblend from 31 to 34, led 
to a four-fold increase in the notched Izod impact resistance.