CA1042590A - Thermoplastic polymer blends of epdm polymer, polyethylene and ethylene-vinyl acetate copolymer - Google Patents

Abstract

THERMOPLASTIC POLYMER BLENDS OF
(1) EPDM POLYMER HAVING A HIGH
DEGREE OF UNSTRETCHED CRYSTALLINITY
WITH (2) POLYETHYLENE
ABSTRACT OF THE DISCLOSURE
EPDM polymers having a high degree of unstretched crystallinity are physically blended with polyethylene poly-mers. The blends exhibit superior tensile strength, better than that predicted from their additive individual effects.
The thermoplastic polymer blends are useful to prepare molded products, tubing, liners, and like products.

Description

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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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1~4ZS90 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, -:
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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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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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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 )f~ ,) h 1~ t~,a~ JJ Jer~ q~

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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
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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 r ~ TJ~
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ZS~10 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).

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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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1~4Z5~30 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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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, /~o~,~f~ G~/~S D ~ t~ ~
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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.

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Claims (7)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. A thermoplastic 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 poly-mer, of a polyethylene polymer.

2. A thermoplastic polymer blend of Claim 1 wherein the EPDM polymer consists essentially of interpolymerized units of from about 70 percent to about 80 percent by weight of ethyl-ene, about 15 percent to about 29 percent by weight of propy-lene, and about 1 percent to about 5 percent by weight of a nonconjugated diene monomer containing from 5 to about 25 car-bon atoms in the monomer.

3. A thermoplastic polymer blend of Claim 2 wherein the nonconjugated diene monomer is an alkenyl norbornene.

4. A thermoplastic polymer blend of Claim 2 wherein the polyethylene polymer is present in from about 10 parts to about 100 parts by weight per 100 parts by weight of EPDM
polymer.

5. A thermoplastic polymer blend of Claim 4 wherein the polyethylene polymer is a low density polyethylene having a density of below about 0.94 gram/cc.

6. A theroplastic polymer blend of Claim 5 wherein the EPDM polymer consists essentially of interpolymerized units of ethylene, propylene, and 5-ethylidene-2-norbornene monomers and the polyethylene has a denisty of about 0.92 gram/cc.

7. A thermoplastic polymer blend of Claim 6 compris-ing (1) an EPDM polymer consisting essentially of interpoly-merized units of about 73 percent by weight of ethylene, about 23 percent by weight of propylene, and about 4 percent by weight of 5-ethylidene-2-norbornene, and (2) from about 10 parts to about 100 parts by weight per 100 parts by weight of the EPDM polymer, of a polyethylene polymer having a density of about 0.92 gram/cc.