Note: Descriptions are shown in the official language in which they were submitted.
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1~42590
The invention relates to thermoplastic polymer blends.
Polymer blends of ethylene-propylene (EP) polymers
or of ethylene-propylene-diene (EPDM) polymers with poly-a-
monoolefin polymers, particularly with polyethylenes, are known
to the art (See U.S. Patent Nos. 3,176,052; 3,328,486; 3,361,850
and 3,751,521). At times, curing or crosslinking agents are
added to effect chemical changes in the nature of the blend
(See U.S. Patent Nos. 3,256,366 3,564,080; 3,758,643; and
3,806,558). Polymer blends described in U.S. Patent ~os.
3,785,643 and 3,806,558 are stated to be thermoplastic in nature.
They are prepared by partially crosslinking the polymers, parti-
cularly the EPDM polymers. The polymer blends of the present
invention; i.e. physical blends of (1) EPDM polymers having a
high degree of unstretched crystallinity and (2) polyethylene
(PE) polymerA, are thermoplastic in nature, yet do not use
curing or crosslinking agents in their preparation. Additionally,
the tensile strengths of the blends are superior to that pre-
dicted from the additive individual effects of the polymer com-
ponents. In blends where low density PE polymers are used,
tensile strengths of the blends are higher than either polymer
component alone.
Thermoplastic polymer blends comprising (1) an
ethylene-propylene-diene (EPDM) polymer having a high unstretched
crystallinity of at least about 10 percent by weight, and (2)
a polyethylene (PE) polymer are prepared by physically mixing
under heat and shear conditions the two polymer components.
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According to the invention there i9 provided a thermo-
plastic polymer blend comprising (1) an EPDM polymer consisting
essentially of interpolymerized units of about 65 percent to
about 85 percent by weight of ethylene, about 5 percent to
about 35 percent by weight of propylene, and about 0.2 percent
to about 10 percent by weight of a diene monomer, said EPDM ~
polymer having a weight percent unstretched crystallinity of ~ .
from about 10 percent to about 20 percent by weight of the -
polymer and a melt endotherm value of about 6 to about 10 .
calories per gram and (2) from about 5 parts to about~200
parts by weight per 100 parts by weight of the EPDM polymer, -:
, . . .
of a polyethylene polymer.
The thermoplastic blends exhibit tensile strengths .
greater than that predicted from each polymer's individual
.
contributive effect. Especially good results are obtained ~ -~
with blendq of the EPDM polymer and low density PE polymer.
No curing or crosslinking agents are used to obtain the
superior tensile strengths ~: -
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of the thermoplastic blend.
DETAILED DESCRIPTION OF THE INVENTION
The thermoplastic polymer blends of this invention
comprise a physlcal mixture of two polymer components; i.e,
an ethylene-propylene-diene (EPDM) polymer and a polyethylene
~PE) polymer. The polymers are mixed in a range of from about
5 parts by weight to about 200 parts by welght of PE per 100
parts by weight of EPDM polymer. The use of over 200 parts
of PE per 100 parts of EPDM in the polymer blend 18 not necess-
ary to achleve the advantages of the present invention. Excel-
lent results are obtained ln a range o~ ~rom about 10 parts to ~ :
about 100 parts of PE per 100 parts of EPDM.
The polymer blends are truly thermoplastic, exhibit-
~ng excellent streneth and structural stability at ambient
temperature but easily processable at temperatures above 120C.
A smooth roll ls formed in milllng operations, and the blends
are readily extrudable and moldable, having good flow properties.
Formed items made from the blends are reprocessable. In con-
trast to the thermoplastlc blends disclosed in U.S. Patent Nos.
3,785,643 and 3,806,558, the polymer blends of the present in- -
ventlon do not need or use curing or cros~linking agents to
effect partial cure of the polymer component~, particularly
the EPnM polymer. However, also in contrast to other Xnown
thermoplastic blends employing an EPDM polymer, the EPDM poly- ;~
mers used in the present invention are unique in havlng a high
unstretched crystalllnlty, which 18 a measurable property o~
the EPDM polymer. Other propertles o~ the unlque EPDM polymer
used are dlsclosed in the following dlscussion.
The ethylene-propylene-diene (EPDM) polymers employed
have high unstretched crystalllnlty, ranging from a minimum of
about 10% by welght to about 20% by weight based upon the
welght of the polymer. More preferredly, th~ unstretched cry-
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.
S90
stallinity o~ the polymer ranges ~rom about 12% to about 16%
by welght of the EPDM polymer. The unstretched crystallinlty
of the EPDM polymer is measured using an X-ray technique. Mea-
suring weight percent crystallinity in polymer~ via X-ray is
a known technique (see Natta et al, Atti Accad-Nazi. Lincei.
Rend. (8) 8 11 (1957)). The method used herein consisted of
pressing a 0.020 inch thick film of the EPDM polymer at 120C.
and 20,000 pounds pressure. The ~ilms were quickly cooled
(quenched). The thin films are then mounted and exposed to
X-ray~, and a defraction scan is made across an angular range.
Using a diffractometer, a plot of the angular distribution of
the radiation scattered by the ~ilm is made. This plot is seen
as a diffraction pattern o~ sharp crystalline peaks superim- -~
posed upon an amorphous peak. The quantltative value of weight
percent crystallinity ls obtained by dlviding the crystalline
diffraction area of the plot by the total dlffraction ~rea on
the plot.
The EPDM polymers also exhibit a large melt endotherm
of from about 6 to about 10 calories/gram. The melt endotherm
? is measured using a Diferential Scanning Calorimeter (DSC)
A sold by DuPont as the DuPont 900~Thermal Analyzer. The test
measures orlentation w~thin the polymer. A completely amorphous
EPDM terpolymer would have a zero melt endotherm. The test con- ;
sists o~ placing a polymer sample of known weight into a cloaed
aluminum pan. DSC cell calorimeter pans supplied by DuPont
were used. The polymer sample ls then heated at a rate of
10C./mlnute over a temperature range of ~rom -100C. to ~75C.
The re~erence material used is glass beads. The DSC chart is
precalibrated, using metals with known heats o~ Yusion, to pro-
vide a chart having a unit area in terms of calories/squareinch/minute. As the poly~er sample is heated, a crystalline
melt point peak will show on the chart. The area under the
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~)4ZS90
crystalline melt point peak is measured, and the melt endotherm
in calories/gram is calculated from the area obtalned.
The EPDM polymer is comprised of interpolymerlzed
units of ethylene, propylene and diene monomers. The ethylene
forms from about 65% to about 85% by weight o~ the polymer,
the propylene ~rom about 5% to about 35% by weight, and the
diene from about 0.2~ to about 10% by weight, a'l based upon
the total weight of the EPDM polymer. ~ore preferredly, the
ethylene content is from about 70% to about 80% by weight, the
propylene content is from about 15% to about 2g% by weight, and
the diene ~ontent is from about 1% to about 5% by weight of the
EPDM polymer. Examples of the diene monomers are: con~ugated
dienes such as isoprene, butadiene, chloroprene, and the like;
and noncon~ugated dienes, containing from 5 to about 25 carbon
atoms, such as 1,4-pentadlene, 1,4-hexadiene, 1,5-hexadiene,
2,5-dimethyl-1,5-hexadiene, 1,4-octadiene, and the like; cyclic
dienss such as cyclopentadiene, cyclohexadiene, cyclooctadiene,
dlcyclopentadiene, and the like; vinyl cyclic ènea such as 1-
vinyl-l-cyclopentene, l-vlnyl-l-cyclohexene, and the like;
alkylbicycl~nondienes such as 3-methylbicyclo(4,2,1)nona_3,7_
diene, 3-ethyl-bicyclonondiene, and the like; lndenes such as
methyl tetrahydroindene, and the like; alkenyl norbornenes
such as 5-ethylldene-2-norbornene, 5-butylidene-2-norbornene,
2-methallyl-5-norbornene, 2-isopropenyl-5-norbornene, 5-(1,5-
hexadlenyl)-2-norbornene, 5-(3,7-octadleneyl)-2-norbornene,
and the like; and tricyclo dienes such as 3-methyl-tricyclo
(5,2,1,02~6)-31~decadiene, and the like. The more preferred
dienes are the noncon~ugated dienes. Particularly good results
are obtained when alkenyl norbornenes are used as the dlene
monomer.
The presence of interpolymerlzed dlene monomer ln
the ~PDM polymer 1~ a necess ry featuro o~ the EPDM polymer.
,, : , .. ' ' . '' . ' ;' ' " "' '
lQ42590
It was found that blends of EP (ethylene-propylene) polymers
with polyethylene polymers did not exhibit the unexpectedly
high tensile strengths which characterize the blends of the
inventlon. The type o~ diene monomer used is not critlcal a~
long as the EPDM polymer employed has high unstretched cry-
stallinity. -
The EPDM polymers can be readily prep~red following
known 6uspension and solution polymerization processes and
techniques.
The EPDM polymers are high molecular weight, solid
elastomers. They have a dilute solution viscoaity (DSV) of
about 1.6 to about 2.5 measured at 25C. as a solution of 0.2
gram of EPDM polymer per dlclliter oi toluene. The raw polymer
has a green strength tensile of about 800 p8i to about 1800
ps~, and more typically, from about 1000 p8i to about 1600 psi,
and an elongation at break of at least about 600 percent.
The polyethylene employed in the blend can be a low - -
(to about 0.94 grams/cc.) density, medium (about 0.94 gramæ/
cc. to about o.g6 grams/cc.) density, or high (above about o.g6 : : -
grams/cc.) density polyethylene. The low density polyethylenes ~,
are more pre~erred as they provide actual tensile reinforcement
between the polymers. The polyethylenes have a melt index of
.
fro~ about 0.2 grams/10 minutes to about 30 grams/10 minutes
~ measured at 190C. under a 2.16 kilogram load. If a low denslty
polyethylene is used, the melt lndex 18 pre~erredly below 7
gram/10 mlnutes. The polyethylenes are commercially available,
and can be readily prepared using standard polymerization tech-
niques known to the art. Aa mentioned before, the polyethylene
i~ used at from about 5 parts to about 200 parts by weight with
100 parts by weight of the EPDM polymer. Particularly good
re~ults are obtained when the PE i8 used at about 10 parts to
about 100 parts by weight wlth 100 parts by weight o~ EPDM
polymer,
-6-
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1~4ZS9O
The composition of the inventlon comprlses a physical
blend of the EPDM polymer and polyethylene (PE) polymer. No
cure or crosslinking agents are employed. It was totally unex-
pected that the thermoplastic polymer blend o~ the two poly-
meric components would exhibit a tenslle strength greater than
that predicted from the additive individual effects of any one
component alone. Prior to this invention, the classic behavior
of uncured polymer blends is that tensile strengths of the
blend would be lower than the additive individual e~fects of
each polymer. It was further unexpected thatthe use of cry-
stalline EPDM and low density PE in the blends would produce
higher tensile strengths in the blend than the tensile strength
of either one polymer component alone.
The polymer blends are truly thermoplastic, moldable
and remoldable at temperatures of above 120C., preferably at
above 140C. to about 200C.,-yet having a strong, flexible - -
plastic nature at room temperatures. -~
A wide range of rubber and plastic compounding in-
gredients are readily mixed with the thermoplastic polymer
blends usipg mixing eq~ipment such as two-roll mllls, extruders,
r~ 13 4h l u~
A bsi~ xers, and the like. Standard mixing and addition
techniques are used. In many cases, the addition of compound-
ing lngredients, particularly waxes, plasticizers and extend-
ers, can detract from the overall tensile strength of the
thermoplastic blend. Relnforcing ~illers such as fumed silica
provide increased tensile strength to the blends,
Examples of compoundlng ingredients are metal oxides
llke zinc, calcium, and magneslum oxide, lead monoxide and di-
oxide, ~atty acids such as stearic and lauric acld, and salts
thereo~ such as cadmium, zinc and copper stearate and lead
oleate; fillers such as the carbon black~ like channel blacks,
A high reinforcing blacks as NllO and N330, low reinforcing
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A black~ as N550 and N770, and thermal black~ as N880 and N990,
calcium and magnesium carbonates, calcium and barium sulfates,
aluminum silicates, phenol-formaldehyde and polystyrene re-
sins, asbestos, and the like; plasticizers and extenders such
as dialkyl and diaryl organic acids like diisobutyl, diisooctyl,
diisodecyl, and dibenzyl oleates, stearates, sebacates, aze-
lates, phthalates, and the like; ASTM type 2 petroleum oils,
ASTM D2226 aromatic, naphthalenic and paraffinic olls, castor
oil, tall oil, glycerin, and the like; antioxidants, antiozon-
ants, and stabilizers such as di-~-naphthyl-p-phenylenediamine,
phenyl-~-naphthylamine, dioctyl-p-phenylenediamine, N-1,3-
dimethylbutyl-N-phenyl-p-phenylenediamine, 4-isopropylamino
d~phenylamine, 2,6-di-t-butyl paracresol, 2,2'-methylenebis- -~
(4-ethyl-6-t-butyl phenol), 2,2~-thiobis-(4-methyl-6-t-butyl ~
phenol), bisphenol-2,2'-methylenebis-6-t-butyl-4-ethylphenol, ~ -
4,4'-butylidenebis-(6-t-butyl-m-cresol), 2-(4-hydroxy-3,5-t-
butylaniline)-4,6-bis(octylthio)-1,3,5-triazine, hexahydro-
1,3,5-tris-~-(3,5-di-t-butyl-4-hydroxyphenyl~propionyl-s-tri-
azine, tri6-(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate,
tetrakismethylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propion- `~
ate methane, distearyl thiodipropionate, dilauryl thiodlpro-
pionate, tri(nonylatedphenyl)phosphite, and the like; and
other ingredients such as plgments, tacklfiers, ~lame ratardantæ,
iungicldes, and the 11ke. Such ingredlents are used ln levels
well known to those skllled in the art.
Applications for the thermoplastic polymer blends
lnclude tubing, liners, wire and cable insulation, mats, and
molded ltems such as shoe soleR, toys, kitchen ware, and the
iike.
The blends were evaluated for their stress-strain
properties; i.e. ten6ile, modulus, and elongation, followlng
ASTM procedure D638 (using a pull rate of 20 inche~/mlnute).
-8-
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~4'~S~O
Hardne~s was measured followlng ASTM D2240.
The ~ollowing Examples are presented to further
illustrate the invention. Unless otherwise stated, the ingre-
dient~ recited in the recipes are used in parts by weight.
EXAMPLES
The polymeric components of the blends, along with
compounding ingredients, if used, were mixed together using
a two-roll mill. The roll ratio was 1.2 to 1 and the front
roll has a roll speed of 21 rpm. Front roll temperature was
150C. with the back roll sllghtly cooler. The EPDM was banded
on the mill and the other polymeric and compounding ingredients
(if used) added to the banded polymer. Mill time ~as about
5 minutes. ~ -~
The mixing conditions and temperatures outlined above
are not critical. The important factor i8 to get uniiorm dis- ~
persion of the polymers and ingredients in the thermoplaætic ~ -
blend. This can be accomplished using other equipment~ such
as a Banbury mixer, by mixing at other temperatures and for
other times, and the like; all of which conditions and proce-
dures are well known to the artisan. The above conditions were
used to achieve good, thorough mixlng, and are outlined to
illustrate the preparatlon of the physical blends of the Exam-
ples. -
EXAMPLE I
A highly cryst~lline EPDM polymer was mixed with a
A low dens~ty polyethylene (PE Cl~ polymer~ and the re~ultlng
thermoplastic blend evaluated for lts tenslle strength and
elongation. For comparatlve purposeB~ other EPDM and ethylene-
propylene (EP) polymers were also mixed with the same PE poly-
mer and the blends evaluated. The PE polymer used has a den-
sity o~ 0.92 g./cc. and a tensile strength o~ 1800 p~1 and an
elongation of 570 percent. The EPDM polymers employed are
identi~ied as follows:
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1~42590
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The EPDM (and EP) polymers and PE polymer were
blended together using a two-roll mill operatlng at a roll
temperature of about 160C. The polymers were mlxed about 5
minutes, sheeted o~f of the mlll and pressed in a tenslle mold
to prepare samples for tensile and elongation measurements.
The recipes used and data obtained are as ~ollows: :
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Sample 1, a thermoplastic polymer blend of the pre-
sent invention, has excellent tensile strength. The measured
tensile strength is unexpectedly superior to those of the
other blends, and is higher than the tensile strength of either
polymer component used alone.
EXAMPLE II
The experimentation in Example I was r^peated but
A for the use of a high density polyethylene (PE-LB733~ polymer
in the blend. The PE used has a density of 0.95 g./cc. and a
tensile strength of 3800 psi. Again the thermoplastic blend ~ .containing EPDM-l, a polymer of the present invention, exhibited
the hi6he~t tens11e strength,
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EXAMPLE III
The highly crystalline EPDM polymer used ln Example
I (EPDM-l) was blended with different types o~ polyethylene
polymer. The blends were evaluated ~or their tens~le proper-
ties. Recipes and data ~ollow:
Tensile -
Strength -
~psi) 1 2 3 4
A EPDM-l ~ 1640 100 100 100 100
10 1~ PE-NA30~a 2090 10 - - -
PE-C14b~ 1800 - 10
PE-LS630C~ about - - 10
PE-LB733d~ 3~00 - - - 10 ;
Tensile strength, 2300 2300 2160 2520
p~i -
Elongation, percent 660 670 680 700
Rardness, Durometer A 72 72 75 75
a polyethylene having a density of 0.92 g./cc.,
- 20 a melt lndex at 190C. of 1.28 g/10 mlnutes,
i~ a tensile strength of 2090, and an elongation
o~ 650 percent.
b polyethylene having a denslty of 0.92 g./cc., ~ -
a tensile strength of 1800 psi, and an elonga-
tion of 570 percent.
c polyethylene having a density of o.g6 g./cc.,
a melt lndex of 28 g./10 mln., a tensile
strength of about 4500 psi (pulled at 2 inches/
mlnute), and an elongation of about 25 percent.
d polgethylene havlng a density of 0.95 g.~cc.,
a melt index of 0.23 g./10 minutes, and a
ten ile strength o~ 3800 p~i, and an elonga-
tion of about 60 percent.
Sa~ples 1 and 2 contalned low denslty PE polymers in
the thermoplastic blends. In both cases the tensile strength
of the blend 1~ higher than that o~ ~ny one polymer component.
Samples 3 and 4 contained medlum to high denslty PE polymers.
The blend tensile strengths in both lnstances are hlgher than
;~ what would have been predicted ~rom the addltive effects o~
the tenslle of the PE pol~mer to the EPDM polymer, on a weight
; percent basls. For example, sample 3 would have a predicted
tensile value o~ (1640 + 410) = 2050 psl, and Sample 4 would
have a predlcted tensile value of (1640 ~ 350) = 1990 psi,
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while the actual values were 2160 psi and 2520 psi respectively.
EXAMPLE IV
An EPDM polymer similar in composltion to the highly
crystalline EPDM polymer of Example I was blended with various
PE polymers at various levels of PE polymer to EPDM polymer.
The polymers were mixed for 7 minutes on a two-roll mill oper-
atlng at 160C. All of the resulting themoplastic blends
exhibited excellent tensile strengths. The data shows that,
generally, the use o~ over 50 parts by weight of PE polymer
per 100 parts of EPDM polymer is not necessary to achieve the
maximum tensile properties of the blends. A small amount of
lubricant was used in the blends. As will be shown in the
next example, lubricant~ can detract from the overall tensile
strength of the blends.
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1~42590
EXAMPLE V
Many types of standard rubber and plastic compoundlng
; ingredients can be mixed with the thermoplastic polymer blends
of the invention, particularly ~llers and reinforcing agents,
-5 ant~oxidants and stabilizers, and plasticizers and lubricants.
; The compounding ingredients can be added uslng procedures and
in amounts well known to those skilled in the art. However, it
has been ~ound that the addition of lubricants can detract from
;~ the overall tensile strength Or the thermoplastic polymer blends.
The following data demonstrates this fact. The EPDN polymer
and PE polymer used are similar to those employed in samples
12 to 15 of the previous example.
1 2 3
`~ ~ EPDM ~ 100 100100
15 ~ PE-DND2004 _ 100100 -
Aristowaxa - _ 5
; Tensile strength, psi 1270 26502470
'`! Elongation, percent 670 760 700
a para~finic wax lubricant having a melting ~ -
point of about 165F. ;~ ~
.~ , .
; ~ ' ' '
.,
.
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, -18_
~, ~ ~J'J "~ ' D ~ J~D~
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