Thermoplastic polymer alloy composition

Thermoplastic polymer alloy compositions are provided consisting of a blend of polypropylene, ethylene copolymer ionomer resin, ethylene/glycidyl acrylate or methacrylate copolymer, and uncrosslinked ethylene propylene rubber. The compositions are particularly useful in applications where a wide range of temperature and abrasive conditions are encountered.

BACKGROUND OF THE INVENTION 
This invention relates to thermoplastic polymer alloy compositions which 
exhibit excellent low temperature properties coupled with heat and scuff 
resistance and to a process for producing such compositions. 
For many years films and laminates of polyvinyl chloride (PVC) resins have 
found utility in the production of thermoformed articles including, for 
example, videotape cases, food packaging, and beverage containers. In the 
automotive field PVC has been employed extensively in the fabrication of 
interior sheathing for automobiles, for example, in instrument panel 
skins, door panels, roof liners, and seat covers. Although performance has 
been adequate, there are certain disadvantages inherently associated with 
use of PVC in these applications. In particular, large amounts of 
plasticizers must be incorporated into the resin in order to enhance 
flexibility and low temperature properties, as well as to provide a soft 
surface texture. However, as a result of the high temperatures to which 
the interiors of parked automobiles are subjected, the plasticizers have a 
tendency to migrate to the surface of the PVC films and consequently the 
PVC sheathing becomes brittle. In addition, a film of plasticizer is 
gradually deposited on the interior surfaces of the automobile, 
particularly on the interior surfaces of the windows. 
A more recently recognized disadvantage of the use of PVC concerns the 
difficulty of disposal and recycle of the resin. Incineration results in 
generation of significant quantities of hydrogen chloride and heavy metal 
redidues. In addition, the resin is not compatible with other plastics 
used in the manufacture of automobiles, thereby creating problems during 
recycling operations. 
Non-halogenated thermoplastic alloy compositions having good high 
temperature properties are known in the art, for example the 
polyolefin/ionomer blends disclosed in U.S. Pat. No. 4,871,810 or the 
blends of partially crosslinked ethylene/alpha-olefin copolymers with 
reaction products of ethylene copolymer ionomers and olefin/epoxy 
copolymers, disclosed in U.S. Pat. No. 4,968,752. Such compositions, 
however, are either deficient in softness of scuff resistance. 
Consequently there is a need in the art, especially in the automotive 
field, for a material which combines the low and high temperature 
resistance properties of plasticized PVC, can be recycled easily, and 
exhibits scuff resistance and softness equal or superior to that of 
plasticized PVC. 
SUMMARY OF THE INVENTION 
In accordance with this invention thermoplastic alloys compositions are 
provided comprising a blend of 
a) 10-40 wt. % polypropylene, 
b) 15-50 wt. % uncrosslinked ethylene propylene copolymer rubber, 
c) 20-60 wt. % of an ionomeric copolymer of ethylene and an alpha, 
beta-unsaturated C.sub.3 -C.sub.8 carboxylic acid, and 
d) 1-5 wt. % of a copolymer of ethylene and glycidyl acrylate or glycidyl 
methacrylate. 
These compositions exhibit excellent high and low temperature properties, 
scuff resistance, and softness. Since they are non-halogenated and 
compatible with a wide variety of recyclable materials they are more 
environmentally acceptable than PVC. 
The present invention is further directed to a process for preparing the 
thermoplastic alloy compositions, said process comprising melt blending 
a) 10-40 wt. % polypropylene, 
b) 15-50 wt. % uncrosslinked ethylene propylene copolymer rubber, 
c) 20-60 wt. %of an ionomeric copolymer of ethylene and an alpha, 
beta-unsaturated C.sub.3 -C.sub.8 carboxylic acid, and 
d) 1-5 wt. % of a copolymer of ethylene and glycidyl acrylate or glycidyl 
methacrylate. 
DETAILED DESCRIPTION OF THE INVENTION 
The polypropylene component of the alloy compositions of the invention 
consists of crystalline polypropylene and is intended to include in 
addition to the homopolymer those polymers that also contain minor 
amounts, usually not greater than 15 weight percent, of higher 
alpha-olefins, e.g. those containing 3-8 carbon atoms, such as butene, 
octene, etc. The polypropylene polymers useful in this invention have melt 
indices in the range of from about 0.07-80 dg/minute and are present in 
the alloy composition in amounts of 10-40 percent by weight, preferably 
20-30 percent by weight. 
The alloy compositions also contain 20-60 percent by weight, preferably 
30-50 percent by weight of an ionic copolymer of ethylene, an unsaturated 
C.sub.3 -C.sub.8 carboxylic acid, and optionally, at least one softening 
comonomer that is copolymerizable with ethylene. Acrylic and methacrylic 
acids are preferred acid comonomers. The softening comonomer can be an 
alkyl acrylate selected from the group consisting of n-propyl-, n-butyl, 
n-octyl-, 2-ethylhexyl-, and 2-methoxyethyl-acrylates. The preferred alkyl 
acrylates are n-butyl-, 2-ethylhexyl-, and 2-methoxyethyl-acrylates. The 
softening comonomer can also be an alkyl vinyl ether selected from the 
group consisting of n-butyl, n-hexyl, 2-ethylhexyl-, and 2- 
methoxyethyl-vinyl ether. The preferred alkyl vinyl ethers are n-butyl 
vinyl ether and n-hexyl vinyl ether. The copolymer is about 10 to 70% 
neutralized with metal ions selected from groups Ia, Ib, IIa, IIIa, IVa, 
VIb, and VIII of the Periodic Table of Elements such as sodium, potassium, 
zinc, calcium, magnesium, lithium, aluminum, nickel, and chrominum. 
Preferably the copolymer has from about 35 to about 70% of the carboxylic 
acid groups ionized by neutralization with metal ions selected from the 
group consisting of sodium, potassium, zinc, calcium, and magnesium. 
The thermoplastic polymer alloy contains about 1.5 weight %, preferably 2-3 
weight %, of an ethylene/glycidyl acrylate or ethylene/glycidyl 
methacrylate copolymer. Optionally, and preferably, the ethylene/glycidyl 
acrylate or ethylene/glycidyl methacrylate copolymer contains 
copolymerized units of an alkyl acrylate or an alkyl methacrylate having 
1-6 carbon atoms. The ethylene/glycidyl acrylate or ethylene/glycidyl 
methacrylate copolymer contains 60-88 weight percent ethylene and 1-12 
weight percent glycidyl acrylate or glycidyl methacrylate. Representative 
alkyl acrylates and alkyl methacrylates that are used in the copolymer 
include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl 
acrylate, isobutyl acrylate, hexyl acrylate, methyl methacrylate, ethyl 
methacrylate, propyl methacrylate, butyl methacrylate, and hexyl 
methacrylate. Ethyl acrylate is preferred and n-butyl acrylate is 
especially preferred. 
The ethylene/glycidyl (meth)acrylate, preferably containing an alkyl 
acrylate of 1-6 carbon atoms, can be prepared by direct polymerization, 
for example, copolymerizing ethylene, an alkyl acrylate, and glycidyl 
methacrylate or glycidyl acrylate in the presence of a free-radical 
polymerization initiator at elevated temperatures, generally 
100.degree.-270.degree. C., usually 130.degree.-230.degree. C., and at 
elevated pressures, i.e. 140-350 MPa. The most preferred 
ethylene/glycidyl(methacrylate copolymers that are used in this invention 
are copolymers of ehtylene, ethyl acrylate, glydicyl methacrylate, and, 
especially, ethylene, n-butyl acrylate, and glycidyl methacrylate. 
The thermoplastic polymer alloy contains about 15-50 weight percent, 
preferably 30-40 weight percent, of an uncrosslinked ethylene/propylene 
copolymer rubber, preferably an ethylene/propylene/nonconjugated diene 
copolymer (EPDM). The nonconjugated dienes can contain from 6-22 carbon 
atoms having at least one readily polymerizable double bond. The 
uncrosslinked ethylene/propylene copolymer rubber contains about 60-80 
weight percent usually about 65-75 weight percent ethylene. The amount of 
nonconjugated diene is generally from about 1-7 weight percent, usually 
2-5 weight percent. Preferably the ethylene/propylene copolymer rubbers 
are EPDM copolymers. EPDM copolymers that are especially preferred are 
ethylene/propylene/1,4- hexadiene, ehtylene/propylene/dicylopentadiene, 
ethylene/propylene/norbornene, ethylene/propylene/methylene-2-norbornene, 
and ethylene/propylene/1,4- hexadiene/norbornadiene copolymers. It is 
important that the ethylene propylene copolymer rubber be non-crosslinked 
because this imparts enhanced scuff resistance to the polymer alloys. 
The alloy compositions of the present invention are generally prepared by 
melt blending the polymeric components under high shear conditions, for 
example in an extruder. The various ingredients may first be combined with 
one another e.g., in a pellet blend, or they may be combined with one 
another via simultaneous or separate metering of the various components. 
They may also be divided and blended in one or more passes into separate 
sections of the mixing equipment. 
The resultant compositions may be formed into sheets, or they may be molded 
into any desired shape. In particular, they may be thermoformed for use as 
instrument panel skins for automobiles. Excellent low temperature 
flexibility combined with scuff resistance, and high temperature 
resistance, enables these compositions to be useful in applications 
wherein a wide range of temperature and abrasive conditions are 
encountered.

EXAMPLES 
The following tests were used to evaluate the compositions of the 
invention. 
Melt Tension - Performed on a Gottfert Rheotens instrument used with a 
Gottfert Rheograph 2001 piston rheometer according to the standard 
procedures given in the instruction manuals for these pieces of equipment. 
The piston rheometer was run at 180.degree. C. with a 2 mm diameter die 10 
mm long at a head speed of 0.067 mm/sec. The Rheotens instrument was run 
at take-away speed starting at 1 cm/sec and then increasing at a rate of 
1.2 cm/sec/sec until the strand broke. 
Maximum Draw - Performed on the Gottfert Rheotens instrument described for 
the melt tension test. A strand of polymer is fed from the capillary 
rheometer through a set of grooved wheels at a rate of 1 cm/sec. Then the 
wheel speed is increased at a rate of 1.2 cm/sec/sec until the strand 
breaks. This test simulates the elasticity of the melt and allows one to 
assess the tendency for polymers to draw sufficiently for thermoforming. 
Image - Injection molded disks 1/2 (3.2 mm) thick and 4 inches (10.2 cm) in 
diameter are placed on a Taber Abraser.RTM. apparatus as described in ASTM 
D-1044 using CS-10 wheels and 500 g of weight. The sample is rotated 3 
revolutions to simulate scuffing/scratching. The scuff pattern is then 
analyzed with a Quantimet Image Analyzer.RTM. and a value computed which 
is the percent of sample area in the scuffed region which is marred. A low 
value, therefore, indicates small amounts of marring and a high level of 
scuff resistance. 
Hardness - ASTM D-2240 
Gardner Impact - ASTM D-4226 
Flex Modulus - ASTM D-790 
Tensile Strength - ASTM D-1708 
Elongation at Break - ASTM D-1708 
EXAMPLE 1 
A mixture of 20 parts of polypropylene (melt index 4 g/10 minutes, ASTM 
D-1238, Condition L), 29 parts of an ethylene/propylene/1,4-hexadiene 
terpolymer (monomer ratio 70/26/4), 49 parts of a 45% neutralized zinc 
ionomer of ethylene/n-butyl acrylate/methacrylic acid terpolymer (monomer 
ratio 69.5/22/8.5; melt index 1.4 g/10 minutes, ASTM D-1238, Condition E), 
and 2 parts ethylene/n-butyl acrylate/glycidyl methacrylate terpolymer 
(monomer ratio 66.7/28/5.3, melt index 12.0 g/10 minutes) was placed in a 
polyethylene bag and tumble-mixed until a homogeneous blend was obtained. 
The resultant dry blend, Sample 1A, was melt blended in a Werner and 
Pfleiderer twin crew extruder having a diameter of 28 mm and a length to 
diameter ratio of 27.5. The screw used was a general purpose screw with 
vacuum capability which consisted of elements to convey the feed material 
from the feed zone to a melting zone in which the material was compressed 
and melting commenced. A further section of kneading blocks followed by 
reverse elements provided high shear and pressure to continue the melting 
and mixing processes. The reverse elements also served to provide a melt 
seal following which the melt was decompressed in a vacuum section. 
Following the vacuum zone the melt was recompressed and passed through 
kneading blocks and reverse elements which provided a second vacuum seal. 
The melt was then further compressed and mixed as it passed through the 
extruder and out the die. The extruder barrel and die were set at a 
temperature of 180.degree. C. and the resin was extruded at a rate of 4-5 
kg/hour. Temperature of the melt exiting the extruder die was 210.degree. 
C. The melt strand exiting the extruder was quenched in water and cut into 
pellets. The pelletized product was used to prepare specimens for the 
physical tests listed in Table I. 
A second sample, Sample 1B, similar to Sample 1A, except that the amounts 
of ethylene/propylene/1,4-hexadiene polymer and zinc ionomer were 48 parts 
and 30 parts, respectively, was prepared using the above-described mixing 
and melt blending procedures. Physical properties of Sample 1B are also 
shown in Table I. 
TABLE I 
______________________________________ 
1A 1B 
______________________________________ 
Ingredients 
Polypropylene 20 20 
EPDM.sup.1 29 48 
Zn Ionomer.sup.2 49 30 
E/nBA/GMA.sup.3 2 2 
Physical Properties 
Hardness, Shore D 39 33 
Gardner Impact, -30.degree. C., (J) 
&gt;36 31 
Melt Tension (cN) 11.0 5.9 
Maximum Draw 20.8 46 
Flex Modulus, (MPa) 122.5 103.3 
Image (%) 63 42 
Stress/Strain Properties, Original 
T.sub.B, (MPa) 10.5 9.9 
E.sub.B, (%) 384 490 
Stress/Strain Properties, Heat Aged 3 Weeks 
@ 121.degree. C. 
T.sub.B, (MPa) -- 10.1 
E.sub.B, (%) -- 403 
______________________________________ 
.sup.1 70 ethylene/26 propylene/4 1,4hexadiene 
.sup.2 29.5 ethylene/22 nbutyl acrylate/8.5 methacrylic acid, 45% 
neutralized with zinc 
.sup.3 66.7 ethylene/28 nbuty acrylate/5.3 glycidyl methacrylate 
EXAMPLE 2 
Two thermoplastic polymer alloy compositions, Samples 2A and 2B were 
prepared as follows. For Sample 2A, a mixture of 20 parts polypropylene 
(melt index 4 g/10 minutes), 27.7 parts of 
ethylene/propylene/1,4-hexadiene terpolymer (monomer ratio 70/26/4), 48 
parts of 45% neutralized zinc ionomer of ethylene/n-butyl 
acrylate/methacrylic acid terpolymer (monomer ratio 69.5/22/8.5; melt 
index, 1.4, ASTM D-1238, Condition E), 2 parts ethylene/n-butyl 
acrylate/glycidyl methacrylate terpolymer (monomer ratio 66.7/28/5.3, melt 
index 12.0 g/10 minutes), and 3.3 parts of a carbon black concentrate (30% 
carbon black in polyethylene) was placed in a polyethylene bag and 
tumble-mixed until a homogeneous blend was obtained. For Sample 2B, a 
mixture of 20 parts of the polypropylene, 28 parts of the 
ethylene/propylene/1,4-hexadiene terpolymer, 48 parts of the ionomer 
resin, 2 parts of the ethylene/n-butyl acrylate/glycidyl methacrylate 
terpolymer, and 2 parts of Ampacet 19238 carbon black concentrate (45% 
carbon black in ethylen/methyl acrylate copolymer) was mixed as described 
above for Sample 2A. The resultant dry blends were individually melt 
blended in the Werner and Pfleiderer twin screw extruder described in 
Example 1, using substantially the same conditions. Physical properties of 
the resultant compositions are shown in Table II. 
TABLE II 
______________________________________ 
2A 2B 
______________________________________ 
Ingredients 
Polypropylene 20 20 
EPDM.sup.1 27.7 28 
Zn Ionomer.sup.2 48 48 
E/nBA/GMA.sup.3 2 2 
Black #1.sup.4 3.3 -- 
Black #2.sup.5 -- 2.0 
Physical Properties 
Hardness, Shore D 40 39 
Gardner Impact, -30.degree. C., (J) 
34.6 34.0 
Melt Tension (cN) 9.5 11.4 
Maximum Draw 20 21 
Flex Modulus, (MPa) 148 -- 
Image (%) 47 -- 
Stress/Strain Properties, Original 
T.sub.B, (MPa) 12.0 10.6 
E.sub.B, (%) 175 349 
Stress/Strain Properties, Heat Aged 3 Weeks 
@ 121.degree. C. 
T.sub.B, (MPa) 13.0 12.7 
E.sub.B, (%) 473 465 
______________________________________ 
.sup.1 70 ethylene/26 propylene/4 1,4hexadiene 
.sup.2 29.5 ethylene/22 nbutyl acrylate/8.5 methacrylic acid, 45% 
neutralized with zinc 
.sup.3 66.7 ethylene/28 nbuty acrylate/5.3 glycidyl methacrylate 
.sup.4 30% carbon black in polyethylene 
.sup.5 Ampacet 19238 carbon black concentrate 
EXAMPLE 3 
A mixture of 20 parts polypropylene (melt index 4 g/10 minutes), 45 parts 
of ethylene/propylene/1,4-hexadiene terpolymer (monomer ratio 70/26/4), 33 
parts of a 71% neutralized zinc ionomer of ethylene/methacrylic acid 
copolymer (monomer ratio 90/10, melt index 1.1 g/10 minutes, ASTM D-1238, 
Condition E), and 2 parts ethylene/n-butyl acrylate/glycidyl methacrylate 
terpolymer (monomer ratio 66.7/28/5.3, melt index 12.0 g/10 minutes, ASTM 
D-1238, Condition E) was placed in a polyethylene bag and tumble-mixed 
until a homogeneous blend was obtained. The resultant dry blend, Sample 
3A, was melt blended in the Werner and Pfleiderer twin screw extruder 
described in Example 1 using substantially the same conditions described 
therein. 
Another sample, 3B, was prepared in the same manner, except that Sample 3B 
contained 29 parts of the ethylene/propylene/1,4- hexadiene terpolymer and 
49 parts of the 71% neturalized zinc ionomer. Physical properties of the 
resultant compositions are shown in Table III. 
TABLE III 
______________________________________ 
3A.sup.1 
3B 
______________________________________ 
Ingredients 
Polypropylene 20 20 
EPDM.sup.2 45 29 
Zn Ionomer.sup.3 33 49 
E/nBA/GMA.sup.4 2 2 
Physical Properties 
Hardness, Shore D 41,41 50 
Gardner Impact, -30.degree. C., (J) 
35.3,33.4 &gt;36 
Melt Tension (cN) 7.1,5.3 11.0 
Maximum Draw 40.0,78.0 35.0 
Flex Modulus, (MPa) 187.9,157.4 
211.8 
Image (%) 42,31 -- 
Stress/Strain Properties, Original 
T.sub.B, (MPa) 11.2,11.9 17.4 
E.sub.B, (%) 408,376 377 
Stress/Strain Properties, Heat Aged 3 
Weeks @ 121.degree. C. 
T.sub.B, (MPa) 14.7,11.0 21.9 
E.sub.B, (%) 409,268 387 
______________________________________ 
.sup.1 Data from two samples 
.sup.2 70 ethylene/26 propylene/4 1,4hexadiene 
.sup.3 90 ethylene/10 methacrylic acid, 71% neutralized with zinc 
.sup.4 66.7 ethylene/28 nbutyl acrylate/5.3 glycidyl methacrylate 
EXAMPLE 4 
A mixture of 20 parts polypropylene (melt index 4 g/10 minutes), 44 parts 
of ethylene/propylene/1,4-hexadiene terpolymer (monomer ratio 70/26/4), 32 
parts of a 71% neutralized zinc ionomer of ethylene/methacrylic acid 
copolymer (monomer ratio 90/10, melt index 1.1 g/10 minutes, ASTM D-1238, 
Condition E), 2 parts ethylene/n-butyl acrylate/glycidyl methacrylate 
terpolymer (monomer ratio 66.7/28/5.3, melt index 12.0 g/10 minutes, ASTM 
D-1238, Condition E), and 2 parts Ampacet 19328 carbon black concentrate 
was placed in a polyethylene bag and tumble-mixed until a homogeneous 
blend was obtained. The resultant dry blend, Sample 4, was melt blended in 
the Werner and Pfleiderer twin screw extruder described in Example 1 using 
substantially the same conditions described therein. Physical properties 
of samples of the resultant composition are shown in Table IV. 
TABLE IV 
______________________________________ 
Ingredients 
Polypropylene 20 20 
EPDM.sup.1 44 44 
Zn Ionomer.sup.2 32 32 
E/nBA/GMA.sup.3 2 2 
Carbon Black Conc. 2 2 
Physical Properties 
Hardness, Shore D 41 43 
Gardner Impact, -30.degree. C., (J) 
26.8 35.3 
Melt Tension (cN) 7.2 6.9 
Flex Modulus, (MPa) 142.9 -- 
Maximum Draw 48 45 
Image (%) 34 -- 
Stress/Strain Properties, Original 
T.sub.B, (MPa) 12.7 12.3 
E.sub.B, (%) 361 391 
Stress/Strain Properties, Heat Aged 3 Weeks @ 
121.degree. C. 
T.sub.B, (MPa) 15.8 12.6 
E.sub.B, (%) 436 367 
______________________________________ 
.sup.1 70 ethylene/26 propylene/1,4hexadiene 
.sup.2 90 ethylene/10 methacrylic acid, 71% neutralized with zinc 
.sup.3 66.7 ethylene/28 nbutyl acrylate/5.3 glycidyl methacrylate