Note: Descriptions are shown in the official language in which they were submitted.
CA 02234108 1998-04-28
WO 97/19991 PCT~US96/19184
ARTICLES MADE Fl~OM POLYPROPYLENE~ HIGHER ALPHA-
OLEF'IN COPOLYM~RS
This application is a corl-in~tion-in-part of USSN 08/248,283, filed May
24, 1994.
TECIINICAL FIELD
This invention relates generally to films~ sheets, molded articles, extruded
profiles, tubing or sirnilar articles made from propylene a-olefin copolymers. The
o articles exhibit exceptional physical prope. l-es, in~ ing relatively low cold flow or
creep. More crecific~lly this invention relates to the use of certain propylene ~-
olefin copolyrners (formed using a metallocene catalyst system) where the a-olefin
is seiected from a-olefins having 5 or more carbon atoms.
BACKGROUND
Polyolefin polymers are well known articles of cc..... ~ .,e. The uses of
polyolefins are many and well known to those of skill in the art. Polyolefins have
many useful physical properties. However, in many ~pplic~tionc, polyolcfins
display unacccpt~ble cold flow properties, that is, at room t~ .n~c.dl.lre or service
tL.~Jye.~lure, they exhibit flow when subjected to low ievels of stress for an
P~ntied period. Cold flow recict~nce is a pro~e. Iy of i.~lpOI lance in rnany
polyrner appli~ti~mc Cold flow is defined as the non-recoverable defoin.ation of a
polymer article in response to a force or stress (well below the yield stress of the
material), applied for an extended time at a selected te.~ e~ alure. Different
polymers will exhibit dilT~ t reCict~nces to cold flow
Polypropylene homopolymers and copolyrners have come into wide use.
Over 5 million tons ( 4 million metric tons) of polypropylene are m~rlllf~ red
each year in the United States alone. Polypropylene has a wide range of
co.~l.ercial uses, from pac~ ng films and sheeting to molded food containers andfibrous constructions employed for eY~mrle in diapers and hospital gowns.
There are several classes of polypropylene. One of these classes is
statistical copolymers of propylene and another alpha-olefin (for purposes of this
CA 02234108 1998-04-28
W O 97/19991 PCT~S96/19184
appli~tiQn this l~lq~cifir~tion in~l~ldes ethylene), sometimes also known as random
copolymers. In the past this class has tended to be ~ 1 pl .,~enled largely by
copolymers of propylene and ethylene, usually made using Ziegler-Natta c~t~ly;.ls.
Copo~ le~;~alion of higher alpha-olefins (HAO) (those a~pha-olefins of S or
greater carbon atoms) with propylene, using Ziegler-Natta catalysts has been
problPm~tic in the past due to the lower reactivity of these catalysts towards higher
alpha-olefins. The Ziegler-Natta catalyzed propyle..c elhylene copolymers have
generally found use based on their sl~bst~nti~lly di~ nl p~ upci lies when cûmpared
to polypropylene homopolymers. Broadly, the d;~r~,nces between Ziegler-Natta
o catalyzed homopolymers and propylene-ell.ylene copolymers are seen in suchprùpt;l lies as lower melting point, greater flexibility, better clarity and slightly
improved to~.hnPss for the copolymer.
EP 0 495 099 Al to Mitsui Petrocll~m;cql Industries sl-ggPst~ a method for
polyrnerization ofthe propylene a-olefins utili7ing met~lloc~ne-~ln~..o~ ~nc catalyst
lS systems. The doc~ nt also sll~Psts a propylene a-olefin copolymer where the
propylene is present from 90-99 mole % and the a-olefin is present from 1-10 mole
%. This docllmPnt sl-ge~Psts that the propylene a-olefin copolymers would have anarrow rrolcc~ r weight distribution (Mw/Mn), the copolymer would have a low
melting point, and the copolymers have eYcellent so~ness. The dor~ e~l~ also
s~gest~ a straight line relalion~l~p between Tm and propylene content, however,
no distinction is drawn to the melting point depression effect of difI~ a-olefins.
EP O 538 749 A1 to Mitsubishi Petlcr.h~ ' Co. sl~ePctc a propylene
copolymer composition to produce a film having excellent low-t~ cl alllre heat
sealing, where the composition has I to 70 wt% of A and 30-99 wt% of B where:
2~ A is a propylene ethylene or a-olefin copolymer where the a-olefin has 4-
20 carbon atoms and a MJM" of not more than 3.
B is a propylene ethylene or a-olefin copoly ner where the a-olefin has 4-
20 carbon atoms and a M~,/~ of 3 .5 to 10.
Copolymer A is polyrnerized by a metallocene catalyst system.
Copolymer B is polymerized by a Ziegler-type catalyst.
CA 02234108 1998-04-28
~E016APCT
Substan~ all examples utilize plup~ ~ c e,lhylw~c copoly..lers or
p~p,~ c ~ op~
E3P O 318 049 Al to ~ ~r~n~g8~S c~ne copo~..,~ of propylene
unth minor pOItiOl~S of et~lene antlor a-olefins~ The copolymers are said to ha~e
s vay good mechnical l)lop~~c~ The copo~mers are pol~mcii~ot in ~e presence
of metallocene compound~ The examples of ~s document show pro~"rl~c-
ethylene ant p.~" l~o l-butene copobmers
US S,081,322 suggests po~ol& waxes obtained by copoh,...~.8
pl~l4ne, pres~t l~om 80-99.?S~ by wdght based on total weight ofthe
0 polymer ant 0.2S - 20~/ bywd~ht of units denved fiom c~ c or an alpha-
olefin containing not less than 4 csrbon atoms. Invend~e examples indude
pl~p~l~K ~ CCO~O~ and propylene hexene copcl~ . No rCGo~ni1;on
ofthe ~li~ce of ~e ~bstantial p~pc~ is bCh.O~ such two polyrners are
evident in ~is document.
îs US 4,461,872 ~ a blent of an ~ o -~ ;c copol~ cr of 45-90 mole
p~l of p~oy~ lcne and 10-1S mole ~ll of a G-Cu alph-olefin with an
isotactic p~o&~lene ~1~,...~. Blends are sait to be usefi~ in so~ c ~-~ and
ngid pla~cs including spul~ dc~ fiber l..alc~i61s, films, and adhesives.
Among the pol~...c,.~ that d~ .~o~ ale acceptable cold flow r~ nc4 are
20 polyvinyl cbloride ~PVC)~ The cold flow le~:~t~-ncc of PVC enables it to be used in
applications where the rdativdy poor cold flow of polyolefins is unacc pl~ble
Fresh meat wrap is an example ofthe dr~;e~ of polyolefins when
comp~red to PVC. PVC films are known and valued for their ability to "snap
back~ aR~ defonna~o~ This snap back attribute is direc~y related to the film's
25 ability to resist cold flow. In retail meat di~l~a, such defol,lls~on is causect when
the p~L'9ged meat is hn~ A Ree~~l-e of its "snap back~, meat ~ ppect in PVC
Slm, even aR~ handling~ does not show the effects of ~ch h~.A1;.~ Polyotefins
have ~?eat~dly been triect in film ~pp~ ;ons such as meat wrap with littte
co~ r ~ S~ because when dcfo,.l.ed by hcnAlily3 a p~olyolefin's tenAPncy
30 to cold flow leaves unacceptable finger marks or otner depr~ons or distor~ons of
the film even a~er the paclugect meat itself has recovered (or sub,t~n~ ly re~l~med
lEND--3 SrlEET
Ip_~ ~_p
CA 02234108 1998-04-28
94EO16~PCT
3a
the shape it had before defo~,.~tion) Polypropylene and polyethylene ofthe
polyolef~ns especiaDy exhibit this ~efiri~ncy, due to their relatively poor cold flow.
However, even though PVC has many ad~,~n~gcs in spplir~;onC as
ed above as well as many others PVC has several sllb~ drawbacks
s that hve made its replacement by other pl9~iC~ such as polyolefins, a high priority
in many of those applications. As a first ~c. mple of a drawback the density of
PVC is substantially higher than most polyolefw. The tensity of most PVC is
about 1.2 ~/cc va~s a density well below 1.0 g/cc for most polyolefins. This hasa very p,~elical effiect, that a given unit of wdght of PVC urill yield subst-s-n~i-s-lly
lo less product than a unit of polyolefin. A second d~wback of PVC is that upon
con~b~l~ion, for example in waste or trash in~e~lion, PVC will evolve
. .
CA 02234108 1998-04-28
W O 97119991 PCTAUS96/19184
hydrochloric acid. Still another drawback, espe~iQlly for food and medical related
PVC applic~tion~, is the extractibility of p!~ctici~rs such as phthql~te esters used in
flexible PVC.
Polypropylenes can be molded or extruded into many shapes. Conventional
s homopolypropylene and conve.-lional copolyrners of propylene and elhyl~,nc show
creep or cold flow when subjected to a force or stress. Additionally,
polypropylenes are oPten blended with other materials to modify their p~ope~ ,5,for eY~mple to give them rubbery or more rubbery characteristics.
Certain classes of co,.~pou~ded polypropylenes have rubber like
o characteristics. However, the polypropylene compounds need no vui~- i7~tionPolyolefins such as polypropylene are not generally considered elastic,
however, they are generally rigid and light weight. Rubbers on the other hand are
elastic, but are not rigid.
Rubber products have generally found extensive use in appl;c~tiQnc which
s require elasticity snd flexibility. Molding of rubber into a finished product entails a
curing step, generally referred to as vlJlc~r.;~ ;or, which r~tuh~s the use of
speei~li7Pd molding m~chinPs, long cycle times and a number of cQ~rlic~ted
procPccing steps. The rubber molding process, therefore, does not lend itself easily
to mass production due to these p,.)c~ g diffis-~lti~s It highly desirable to find
a rubber or rubber like compound without the need for a v~ ni~tion step.
Many ~t~ t~ have been rnade to find such rubber analogs. For e~ y)le;,
flexible plastics such as flexible vinyl chloride resins, ethylene/vinyl acetatecopolyrners and low density polyethylenes generally have good flexibility,
f~.ication and molding properties, but suffer from poor heat resist~ncP, and
resiliency (rebound) which greatly restrict their utility.
In order to improve the properties of such flexible plastics, they have been
blended with high melting point plastics such as high density polyethylene and
polypropylene. This blPn~ing however, causes a loss in flexibility.
More recently, a class of cornpounds having properties between those of
cured rubbers and so~ plastics have been investi~ted. These compounds are
generally referred to as therrnoplastic elastomers (TPE). The cl~ccic~l TPE
CA 02234108 1998-04-28
WO 97119991 PCTnJS96fl9184
s
structure involves a matrix of an elastomer such as, for example, a polybutadiene,
polyester or polyurethane, tied together by therrnoplastic junction regions. A well
known eY~mrle of a TPE is Shell's Kraton ~) G, triblock of styrene and
hydrogenated polybutadiene, where the the. ,..opla5lic crosrl ~ ~g points are small
s dorn~inc of glassy polystyrene held together by rubbery polybutarliene blocks. This
structure leads to behavior similar to vul~ani7p~d elastomers at ~b-~nt tempe~dl~re
but, at t~nlpe.alLIres above the polystyrene soRening point, the system undergoes
plastic flow.
A subset of therrnoplastic elastomers, embodying only olefin based
0 polyrners, is referred to as the.,l,oplastic olefins (TPO). A typical TPO conl~lises a
melt blend or like mixture of at least one therrnoplastic polyolefin resin, with at
least one olefin copolymer el~storner (OCE). The therrnoplastic polyolefin resinwill give the TPO rigidity and tenl;)~,alure re~ict~nce while the elastomer imparts
flexibility and resilience as well as improving the tou~hnPss of the material.
s TPOs find particular a~Flic ~ion in the auto industry for flexible exterior
body parts such as, for ex~rnp'~, bumper covers, nerf strips, air dams and the like.
In such a~,clicalions, it is desired that the TPO have good resiliency (ability of the
part to return to its original shape a~er der~)l,.,alion), impact strength at low
temperatures, fleYibility~ high heat distortion te~llpe~al~re~ surface hardness and
surface finish characteristics. Additionally ease of processability and molding is
desired.
Other application for TPOs include films, footwear, SpGI til~g goods, electric
parts, gPrl etC~ water hoses and belts, to name just a few. Particularly in films,
elasticity and clarity p,o~ ies are ;"lpo~ t. Other of the a~re-..< -n;oned
pl ope. ties will be hllpol t~ll depending upon the desired application.
However, TPOs suffier co..lpar~d to TPEs such as Kraton G due to the
inability of the polypropylene matrix to resist stress over relatively long periods of
time.
Polymer compositions such as TPEs exhibit cold flow . esis~ance and
30 resiliency that generally exceeds that of TPOs. This cold flow resistance andresiliency enables l'PEs to be used in applications where the relatively poor cold
CA 02234108 1998-04-28
~E016APCT
flow and resiliency of polyolefins sucb s polrl,rop~lcnc wlacceptable. Such
applications inchde molded articles for automobiles and appliances~ In molded
articles, shape is oRen a critical paramet~. Cold flow due to a contained load or
due to an appliet force could cause unacceptable non-recoverable deformation in a
S molded put AtditionaUy, much less wagbt and time would be necessary to
cause a load-set or deformation due to a static load if the molded parts ~e
fabricatet fiom most polyoleSns rathertban TPOs. Versus TPEs, the p_rO..,~ce
of most polyolefins would be even poorer.
Even tbougb TPEs hve many ad~lt~es as ~ ~d above, their cost
0 makes tbem unacceptable for some ~ppl;r~lion~ and marginally acceptable in
otbers Wh~e much less c~_ thn TPEs, IPOs on the other band re not an
ideal choice dther tue to the above m~- 1;o~ dcfc.~e physical propwlics.
Tbere is lhc~f~c a need for a polyolefin, s~P~ ly a pol~p.~p~ c
copol~.ner that will resist cold flow to a ~ extent tbat it could replace
s cor,~ tio,~al PPs or the poh~ lcnc co-Y~ror r.~l in blends, eg TPOs, in many
applications
SUMM~RY OF T~F lNVENTION
It has been discoveret that p~pyl~K copolymers made ut~
rnet~tlocerG catalyst systems to pGhJ~w~C propylene with a-olefin ~ ~ nr~ e- s
20 ha~ring 5 or more carbon atoms (highwr alpha-olefins (HAO)), show a surprising
fnh~n~ - ~,nt in important physial p-~p~li~ when compared to propylenc
CGpGhJ~I wS utilizmg alpba-olefins of 4 carbon atoms or less (for purposes ofthis
application, this ~J~cation includes ethylene). Higher alpha-olefins as described
herein include 1-pentene 4methyl-l-pP~ 1 heYene and l-octene. These
2s pol~,,.ws may also contain a second ~ -onC~ r s~ v~ from the group con~
of c~ c, l-butene, 4methy-1-p~!~r~nt~ l-h~Y~n~, and l-octent. Alpha-olefins
can consist of alpl~olefins containing from 2-20 car~on atoms~ In an f .,bodi...f nt
of the present invention, the most st~iking step change is evidenr~d in the present
invention in cold flow n~ P~c~ or creep ~ nC values on ar~cles made from
30 materials made acco~d;n~8 to this e .~boA;~ t These changes will be noted in
'~lAENDED SHEET
- IPEA/EP
CA 02234108 1998-04-28
94E016~PCT
articlcs made from thc copolymcr ~hF ~ vcs, or h parts fab~ ted from a TPO
c~ g~esc COpOI~ a.
In an ~m ~ ;-n~t of the present u~ lion, extruded, mold~ and
calFn~ articlcs such as film, tubing, ex~uded prof~cs, mold~d parts, sheets, or
othcr fab~icatcd u~cles arc cG.np.is~d of an isotactic ~ copolymer of
IP~
CA 02234l08 l998-04-28
PCTrUS96/t91~4
W O 97/l9991
propylene and HAO and alternatively TPOs util;7ine these copolymers. The HAO
is present in the range of from about 0.2 to about 6 mole percent. The copolymerwill have a ~ 'e~ r weight distribution (MWD) ~t~ (weight average
molE~ul~r weight/number average mole~ul~r weight) s 5 and a peak melting point
(DSC) in the range offrom about 100~ C to about 145~ C. An article msde from
these copolymers will exhibit improved creep or cold flow recict~nce when
co-..p~ ~d to a propylene ethylene copolymer of similar flexability.
BRIE~ DESCRIPTION OF T~IE DRAWlNGS
These and other features, aspects, and advantages of the present invention
0 will bcco"-e better understood with regard to the following deic- ;~Jt-on, appended
claims and ncGon~psnying drawings where: Fig. I shows the effect of comonomer
on melting point depression in a propylene copolyrner.
DESCRIPTION OF T~E PREFERRED EMBODlMENTS
The present invention conc~ s Gertain classes of fabricated polypropylene
articles, and their uses. These articles have unique characteristics which make
them well suited for use in certain applic~tionc. Flexible films, tubing, sheets,
extruded profiles, molded articles and other articles made the. ~r. O... have superior
cold flow resiC~ ce comparet to extruded profiles and molded parts made from
polypropylenc-e~l.ylene copolymers. A detailed description follows of certain
~ fe., ed resins for use in fabricating articles that are within the scope of our
invention, and prert,- ~d methods of producing these resins and their products.
Those skilled in the art will appreciate that numerous modifications tO these
prefe.- ed embodiments can be made without departing from the scope of the
invention. For example, though the properties of films and molded plaques are
used to ~xemrlify the attributcs of the copolymers of the present invention, thecopolymers have numerous other uses. To the extent thal our description is
specific, this is solely for the purpose of illustrating pl efe. I ~d embodiments of our
invention and should not be taken as lirniting our invention to these specific
embo~liment~
The term random or st~fi~ti~ copolymer as used herein shall mean
copolyrners of propylene and other a-olefins polymerized in a medium which the
CA 02234l08 l998-04-28
W O 97/t9991 rCTrUS96/19184
contents of the various comonomers and other process conditions are moint~ined
slll,a~ 11y co~ throughout the course ofthe reaction. Variations in the
cQmrQciti~n of the resulting copolymen due to the eYistPnee of el ~ c ~y distinct
sites within the catalytic entity from which they are prepared or to norrnal
s variations experienced in sequçnced reactors, as long as the resulting "r~a~lor
blend" polyrners are r~s( "~1~ in the melt, are ac~ ,Jtcd in the current definition
We have discovered that certain m~PIIQc~ne catalyst systems can be used
to poly..,e. i~e propylene st~ticticsl copolymers having pr ~l~e~ lies which are highly
desirable for conversion into various products. Generally these resins are isotactic
o polypropylene 51~;c~ 1 copolymers, the copolymers utilize propylene and one or
more alpha-olefins. For purposes of this application, the term isotactic is intended
to mean a polymer where propylene tacticity distribution will be greater than about
90 percent mmmm pentads, where m is a meso diad, (m is defined as the same
relative confi~l.ation of methyl groups of two s~cce~sive monomer units (diad) to
lS each other), preferably in the range of from about 94 to about 98 percent mrnmm
pentads, most p. ~,fe~ ably in the range of from about 95 to about 97 percent mrnmrn
p..nt~ds, as dete...uned by nuclear ma~tic reson~ ee (NMR).
P~d~.clion orthe Resins
The polypropylene copolymers of the present invention are prc,fe,.Jbly
produced using supported m~t~llocene catatysts. The copolymers may be
produced in fl~ i7ed bed or stirred bed gas phase reactors, slurry or bulk liquid
reactors of tank or loop type, or other processes practiced for the polymerization
of polypropylene. Series bulk liquid boiling pool reactors are p. ef~ d.
Specific metallocene-type catalysts tcnown to be useful for producing
isotactic olefin polyrners may be found in, for eY~nple~, EPA 485 820, EPA 485
821, EPA 485 822 and EPA 485 823, by Winter, et al. and US 5,017,867 by
Welborn. These p~l~lic~tio~s are inco~l.or~led in the present applicdlion by
don~m~rt for purposes of U.S. patent practice.
Various publications describe placing catalyst systems on a suppo. l.ng
merli-lm and use ofthe resulting supported catalysts. These inctude U.S. Patent
~umbers 5,006,500, 4,925,821, 4,937,217, 4,953,397, 5,086,025, 4,912,075, and
CA 02234108 1998-04-28
WO 97/19991 PCT~S96/19184
4,937,301 by Chang and U.S. Patent Numbers 4,808,~61, 4,897,455, 5,077,255,
5,124,418, and 4,701,432 by Welborn, all of which are incoll~o~ated in the present
~ppiication by reference for purposes of U.S. patent practice.
Specific i~ nalion on the use of support techniques for met~'lcc~one-type
s catalysts, for use in the ~ ,"~ation of propylene alpha-olefin polymers may be
found in US Patent Number 5,240,894 by Burkhardt, also incGllJolalc~ by
..,nce for pu~poses of U.S. patent prosec~ltion. While catalysts used for the
following ~A i'es are employed in a bulk liquid-phase pol~-l..,.i~tion, catalysts
for co.nl--er-,;al use may be used in other plocesses incll~ing for ex~mple, gaso phase and slurry process.
Resins produced by the above ref~r~.,ced processes and catalysts can have
alpha-olefin comor oln~rs in the range of from about 0.2 mole perceDt to about 6mole percent. Above 6 mole percent, ~he resulting resin may make an extruded
profile, or molded article with a melting point or so~ening point too low for most
s prefe.,ed applications. Below 0.2 mole percent comonomer, the flexural mo~ c
may become too high, leading to a product that may be too stiff for most of
applications. In a more prefe.-t;d embodiment, the alpha-olefin comnnomPr is
present in the range offrom about 0.4 to about 3.5 mole percent. In a most
p~efe~ . ed embo~ en1 the alpha-olefin is present in the range of from about 0.5 to
about 3 mole percent. In the most preferred embodiment, the alpha-olefin is
present in the range of from about I to about 3 mole percent.
In one preferred embodimen~, the catalyst system co--lp.;ses a silicon
bridged bis (substituted 2-methyl-indenyl) zirconium dichloride or a derivative
thereof, methyl ~lnm~y~ne and an inorganic support. In a more pr~f. ,lc;d
2s embodiment dimethyl silyl bis (2-methyl-ben7in~enyl) ,i~coru.~m dichloride is the
metallocene of choice. This p-ef~.led catalyst system is used to generate the
propylene-ethylene and propylene-hexene resins used in the films whose properties
are shown in Table 1. However, it would be possible to copolymerize any alpha-
olefin of 2 to 20 carbon atoms utili7i-lg these and similar catalyst systems.
Further details re~,ard.ng preparation of the catalyst system and production
of the resin are provided in the examples that follow.
CA 02234108 1998-04-28
W O 97JI9991 PCT~S96119184
Characte. ;~li.s of the Resins
The polymers of the present invention are subst~nti~lly isotactic in nature.
The polymers will generally have a narrow n1ole~ul~r weight distribution, as
characterized by the M~JM", (weight average mol~ qr weightlnumber average
S moleculqr weiBht) (m~ weight distribution MWD), of S 5. Preferably s 3.5,more preferably < 3.2, most preferably 5 3.0 and the most plef~ ,d s2.5. M~,
(MWD) is d~te.,l..ned by Gel r~.".,eation Chromalography (GPC), as is molecular
weight. Such techniques are well known. The techni~u~s are desc.,bcd in
copending application USSN 08/164,520 incorporated herein by reference for
purposes of US patent practice. The polymers will exhibit melting points in the
range offrom about 100~ C to about 145~ C, more preferably in the range offrom
about 110~Ctoabout 135~C,mostl"ef~ blyintherangeoffromabout 115~C
to about 135~ C.
Food law con.~ nce can be an i",~,olla~ .iLe,ion for articles made from
IS these resins, such compliance usually directly affected by the extractable content of
an article made from a resin. A standard of U.S. Food and Drug A~ aLion as
noted in 21 CFR 177.1520 is to use the n-hexane reflux procedure, the mqYim
extract~hles level of the products of the present invention is eYrecte~l to be less
that about ~ wt%, prefe, ably less than about 4 wt%, most pr~,fe,ably less than
about 3 wt%.
Useful melt flow rates of the polymers of the present invention are in the
range of from about 0. I to about 5000 dg/min. In a prefel . ~d embodiment, the
melt flows are in the range of from about 0. ~ to about 200 dg/min. In a most
pl.,f.,l r~d embodiment, the melt flow rates are in the range of from about 1 to2s about 100 dg/rnin. Melt flow rates are measured by ASTM D-1238 condition L.
Makinv a Film, Tubin~ or Sheet
Films may be made by any techniques known by those of ordinary skill in
the art. For eY~mrle, blown films produced with an annular die and air cooling, or
cast films using a slot die and a chill-roll for cooling are both acceptable
techniques. Oriented films may be produced by either post extruder manipulation
of the blown film through heating and orientation, or by longitudinal stretching of
CA 02234108 1998-04-28
9~BO~6AK~ ' '
Il .
an e~c~uded sheet foDowed by tentering techniques. Films are generally in the
range offrom about 0~2 to about 10 mils (S.0~ to 254 llm).
Sheet may be mate dther by exhuting a Sl~bA~ 'Uy flat proSle fiom a
tie, onto a chiD roD, or all~n~eb by caleodaring. Sheet wiD generaDy be
S consiterod to h~e a thicla~ of fiom 10 m~s to about 100 mils (254 ~m to 2540
~un), akhough shee~ may be substantiaDy ~icker. F1ms or sheets for test pw~
may be made by compression molting techniques, as well.
Tubi~g may be obtainod by profile c.~l.~on For use in medical
applications or the lilce, the tubing will generaLly be in the range offrom about 0.31
0 cm (1/8") to about 2.54 cm (1~) in outside diameter, and hve a waD thickncss of in
the range of fiom about 254 ~m (10 mils) to 0.5 cm (200 mils).
Films made from tbe p.c,~L~s of a vcrsion ofthe prcsent invention may bc
uscd to contain food aficla such as meat and snacks for instance. Such films mayalso be uscd to protoct nd display atticles of appard.
lS Sheet made fitom the p.~ ,ls of aD r~-bc~ 1 of a vcrsion of thc prcsent
invention may be used to fonn containers. Such CQn~ ~ may bc fonned by
of c..-~ing, solid pbase pressurc fo~ , stamping and othcr ~h~
techniques may be used ~or foods such as mcat or dairy products. Sheets may alsobc formed to cover floors or walls or other surfaces
Tubing made ~om tbe pr~ ~ ofthis in~ention may be used in r~
food, or oth~ uses tbat w~l be apparent to those of oldi~y sldll in the art.
Molded ~ es and ~uded Profiles
Molded at~cles may be made by any teshniques known to those of ordinary
sldll in tbc att. For cxampl4 t~ol~:led articles may be fa~,;c~cd by injection
2s molding, blow molding, c.~ sion blow ~Ot'~ r-' molding, and foam
molding. Molded parts are found in many tbi~L ~ 5 of 500 ~m (20 mils) or
greatcr. For molded articles, thc thickness of a cross soc~on ofthe article will~y bc in tbe rangc offrom about 508 llm to about 2.5 cm
Molded articlcs Por health care devices, such as, for example, ~,ù~ges are
also cQ~ .plated. ~'d~d articles for use as vehicle parts are also eQ~lc .~plst~
- AMENDED SHEET
I p ~ ,~ ~ _ p
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Table I sets forth the physical propc.ly data for a propyle.le-elhylene
copolymer film and a propylene-hexene copolymer film meetinC the description of
this application. The film test is used as an in-~irstor of molded article or extruded
profile pc~ro,lll&nce.
s The data in Table I show that other physical/~-.r,cll~n;c~l properties of
articles fabricated from the resins of the present invention will also show an
improvement in value, as noted before, when compared to propylene copolymers
of lower alpha-olefins. It can be readily seen that the data in Table I showing that
the films pr~pared from the hexene- I copolymer have relatively high recictAn~e to
0 cold flow (creep) as inAi-'~t~d by their Rlr,, values (Rn~ defined below). Films
forrned from propylene-ethylene copolymers, on the other hand display the
exrected relatively poor rPcictance to cold flow. The difI;,~ ces dicrussed above
between the tested propylene hexene- I and propyl~,nc-c~ lene copolyrners (both
mPt~1locçne catalyzed), can also be expected with propylene copolymers of other
s HAOs, when col"pa~cd with propylene-elhylene copolyrners.
.e. lies of Molded Articles and E~truded Profilles Produced From the
Resins
The resins ~icalsced above, when forrned into molded articles, will show
superior l~r-~pe. ties when c~,l,t,ared to either co--~lle. c;ally available, Ziegler-Natta
catalyzed or metallocene cataly~d propylene ~-olefin resins where the a-olefin has
4 carbon atoms or less.
Ploa~.cclive examples S-8 indicate that molded parts will show improved
physical prope. Iies in the cO~ Jal iaon noted above.
Determination of R_
A pararneter useful for characterizing cold flow resict~nce or creep
resict~ncç, is a value known as time delayed compliance (TDC). For purposes of
this applicdlion, l-DC is defined as the amount of strain observed in an article that
is placed under a specific stress for a specified time divided by the maenitude of the
stress. The time specified should be chosen such that the time delayed cl~mrli~nce
at that time is at least two (2) times the initial compli~nce of the material. Those of
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13
ordinary skill in the art will recoeni~ that the stress should be below the
spe~,;",cn's yield stress.
A useful technique for eV~llJ~tin~ the step change in prop.,. Iies between
propylene-HAO copolyrners and propylene eth~lene copolyrners has been
s developed (both met~llncene catalyzed).
For films, molded articles, tubing, sheets, and similar a ticles and other
articles made from them, the technique uses the ratio of the TDC of a propylene-ethylene copolyrner, to the TDC of a propylene-HAO copolymer.
The ratio is ,~,r~ s~,nled by the symbol R,~" where:
0 TDC (of p.opylene-elhylene copolyrner articJe)
Rm~=
TDC (of propylene-HAO article)
where the resins to form each article are chosen such that the tensile modulus of
each article is subst~n~i~lly the sarne as that ofthe other article.
IS In the detern~ination of R~", it is i,--~o,L~nl that substantially all pa-~,-.,t~
that affect the physical properties of the articles in both the numerator and
dçno.n;l~tQr of the ratio be the same.
Such parameters include, but are not limited to:
for the resins: mol~ r weights should vary by no more than 10%
for the fabricated article: fabrication conditions and te~hni~luçs;
dimensions of the test syec~"len;
post fabrication l- e~t n ~ n s,
blend components; or additives
It ~,vill be understood by those of ordinary skill in the art that co..~no...c.
content (either HAO or ethylene) can be varied for purposes of ~t~ g
substantially the same tensile modulus in both the propylene-HAO and propylene-
ethylene copolymers.
The choice of equal tensile modulii for the articles of both numerator and
dçnomin~tor ensures that the co-l-l,a-.ion is made at a constant degree of fl~Yil~ility
of the articles. Articles made from isotactic propylene-HAO copolymers of the
present invention will have a R~ xeee~in~ about I.1, indicating 5ignifiç~ntly
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improved resict~nce to cold flow co,--pare~ to isotactic propylenc-elh~lene
copolymers. Blends of olefin polyrners, wherein at least one polymer is a st~tjctir~
isotactic propylene-HAO copolymer are also cQntemrl~ted as long as the R",. of
the article is greater than about 1.1. Possible blend materials may include, but are
not limited to; ethylene copolymers of ethylenically unsaturated esters,
polyethylene homopolymers and copolymers with a-olefins, polypropylene homo
and copolyrners, ethylene propylene rubbers (EP), ethylene, propylene, diene
monomer ela tomers (EPDM), styrene-but~ ne-styrene (SBS), additives such as
slip agents, anti-static agents, colorants, anti-oxidants, stabilizers, fillers, and
fe;n~orce.~ such as CaC03, talc, and glass fiber, and other additives that will be
well known to those of ordinary s~ll in the art.
An R"" of at least I .1 in~ic~tes that an article will exhibit cignific~ntly better
cold flow ,~ nce than an article made from a propylene-ethylene copolymer.
The greater the R~ number, the more improved the co~.pli~r,e of the propylene-
HAO copolymer in relation to the propylene-ethylene based article. In a p~ ,d
embodiment, the Rm~ is at least 1.2. In a more pref~"~,d embo~imPnt~ the Rn~ is at
least 1.3.
In addition to better cold flow recict~lcç, these propylene-HAO
copolymers exhibit other improved physical properties. Table I compares physicaly~ope~lles of propylene copolymers of ethylene and propylene copolymers of
HAOs and dernonctrates that ultimate tensile strength, and impact ~l",ng~h of the
propylene-HAO copolyrners for eA~ le, are siEnifir~ntly improved.
A ~rther i~ ,alion of the fact that the class of propylene-HAO copolymers
is distinct from the propylene-ethylene or propylene-butene copolymer class, is
2s found in the response of the melting points of the copolymers to co-monomer
incorporation. This is illustrated in Figure I It can be seen that the melting point
depression for a given molar comonomer incorporation is about twice as much for
the propylene-HAO copolymers as for the ethylene and butene resin class of
propylene copolymers.
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1~
Blends of olefins polymers includin~ the st~tic~ic~l propylene HAO
copolymers of the present invention and other materials such as additives or other
polyolefins are also co"~ pl~ed
ExamDle I
Plepa.alion Of Metallocene Catalyst
A silica sul,po- Ied metallocene catalyst is p~ &~d according to the
t~aC-h;~c of USSN 071885,170 using dimethyl silyl, bis(2 methyl, 4,5 ber~in~enyl)
zirconium dichloride as the metallocene. The catalyst recipe is 400 grams of silica
(Davison 948), 10 ~rams of metallocene and 3 liters of 10 wt % methyl alumoxane
0 (MAO) in toluene solutio-l as described in Or~anoMetallics. v. 13, No. 3, 1994, p.
954-963. Approximately 600 grams of the finished catalyst system is recoYered.
This catalyst is prepolyll,e. ~ed with one weight of ethylene per weight of catalyst
system at a temperature of about 15~ C. The ethylene is added over a period of 1.5
hours to assure slow reaction rate.
lS Exam~le 2
P~pa. a~ion Of Propylene-Eehylene Copolymers
Approximately 15 grams of ethylene and 550 grams of propylene are added
to an autoclave m~int~ined at 30~ C. A~er allowing time for equilibration, 0.2
grams of the prepolymerized catalyst of eY~mp~e I is added to the reactor and the
te~l.pe~al-lre raised to 50~ C over a period of several min~tes An irmr ediate
reaction is observed. The reaction is te....~ ted aPter 30 minutes to limit the extent
of conversion ofthe ethylene so that its conc ~ alion in the reaction medillm
nearly conctant over the period of the reaction. A total of 1 14 grarns of propylene-
ethylene St~icti~al copolymer is obt~-ed. Its weight average molecular weight as2s measured by size exclusion chromatography is 184,000, its ethylene content
(measured by FTIR) is 3.3 wt %, and its peak melting point is 121~ C.
E~am~le 3
~r~al~Lion Of Propylene-Hexene Copolymers
To the autoclave of Example 2 is added 550 grams of propylene and 34
~o grams of hexene- l . The catalyst of F ~le I is added (0.2 grams) and the
te.ll~JGl aLLIre controlled as in Example 2. The reaction is allowed to run for a total
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of two hours in this case since the relative reactivities of propylene and hexene-1
are nearly the sarne under these conditions. A total of 222 grarns of propylene-hexene s~is~ copolymer is obtained. Its weight average rnole ~ weight as
measured by size exclusion chromatography is 204,000, its hexene-l content is 2.9
wt % (measured by FTIR), and its peak melting point is 126~ C.
E~am~le 4
Preparation Of Propylene l -Octene Copolyrners (Prospecli~e Example)
To the autoclave of F~ 'e 2, 5S0 grams of propylene is added along
with apl)r~ y 45 grams of l-octene as the molar amount of F~ rle 3. The
o catalyst of FY? nple I is added and the te.-~p~.~tllre is controlled as in r~ F 2.
The reaction is allowed to run for 2-3 hours as the reactivities of propylene and I -
octene is nearly the same under these condil;ons. Over 200 grams of propylene-
octene st~tic~ic~l copoiymers could be expected. The average molecul~r weight asmeasured by size ~Yt l-lcion chromatography is over 200,000. The octene-1
IS content is çYpected to be between 2.0 and 4 wt % (if measured by FTIR), and its
peak melting point is in the range of 125-135~ C.
Esamr~lcs 5 and 6
Film P~ al alion and Testing
These e"~-l~)le ~ show l~ret)& ~lion of films from the copolymers of
examples 2 and 3 inclu~lin~ details of procedures for film forn~ing and l)l opc. ly
measurement. The data is summarized in Table 1. (Film preparation and testing
from a resin produced in FY~mP1~ 4 would follow the same procedures.)
A film of the copolymer to be characterized is formed by col,.l)res~;on
mol ling g.2 grams of the granular copolyrner between Mylar~ sheets in a form 152s x 15 centirneters in area and 0.5 mm in thicl~nPss The molding procedure is: 1)
close the platens (controlled at a temperature of 200~ C) until they contact thesarnple; hold for one minute with no applied pressure; 2) increase the cl~mping
force to 10 Tons and hold for one minute; 3) increase the cl~ pi.~ force to 40 tons
and hold for two minutes; 4) release the clamping force and quench the film (still
between the Mylar sheets) in a water bath at room temperature. After the films are
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con~litioned for six days at room temperature, dunlbbell s~mples are die-cut from
the films.
The tensile l~ropel lies of the resulting sarnples are measured on a Zwick
REL 2051 tensile tester at a te.lllJe.al.lre of 25 ~ 2 degrees C for the standard
s tensile prvpellies, procedure DIN 534~7 ~1987) is adhered to. For the
measurement of time delayed com~ e, the tensile s~,e~ n~l- is loaded into the
tester just as if one are doing the ~l~ndard tensile test. A predetermined load is
applied and the s~e~ n elong~tiQn is lecolded as a filnction oftime. The load ischosen to be in the range of 50-60% of that which would cause the ~,e~ c to
o experience yielding (for samples presented here, a load of 11.7 MPa is chosen).
The sarnple elong~tiorl recorded 480 seconds a~er the load is initially applied is
chosen as a measure of cold flow for the particular load and this strain divided by
the stress applied is deci~ted "the time-delayed co~.r1i~nçe".
The results of the evalll~tioll are shown in Table 1.
s Det~.. ;n-lion of R~_
The tensile p.ope,lies of parts made from the resins of eY~mrles 24 are
measured on a tensile tester at a te,l-~ Jre of 25 + 2 degrees C for the standard
tensile prope. lies. For the measurement of time delayed comp!i~lce, the tensilespe~ is loaded into the tester jUSt as if one are doing the standard tensile test.
A predetermined load is applied and the spc~ cl~ elongation is recorded as a
fi~nrtjo~ of time. The same load is chosen for both parts to be tested, per the
deffnisiQn of R~ where the two parts have subst~nti~lly the same modulus. The
sarnple elon~,alion recorded 480 seconds a~er the load is initially applied is chosen
as a measure of cold flow for the particular load and this strain divided by the2s stress applied is d~ci~n~ted "the time-delayed compliance".
E~amPle 7 (l'~r~s~e~tive E~amPle~
Molded Article P. e~Jal ~lion and Testin~
The following prospective ~y~mples outline expected improvements in
molded part performance ofthe propylene copolymer or TPOs forrnulated using
this copolymer of the present invention cGIn~ared to either propylene polyrners
made with conventional Ziegler-Natta catalysts or compared to propylene
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copolymers of propylene and an alpha~olefin of 4 or less carbon atoms that are
produced by metallocene catalyst systems and TPOs formulqted using these latter
copolymers.
I~e~ l propcl lies are evaluated by the following tests.
S (I) Melt Flow Rate - ASTM D-1238, Con~lition L.
(2) Flexural Mo~h~lus, secant - ASTM D-790.
(3) Shore D Hardness - ASTM D-2240.
(4) Notched Izod - ASTM D-256.
(S) Tensile Properties - ASTM D~38.
o (6) BrittlPn~ss Tell.pe.at-lre - ASTM D-746.
(7) Vicat So~ening Teh.p~ ure - ASTM D-1525.
(8) Shrinkage - ASTM D-995.
(9) Density - ASTM D-2240.
(10) Bending Beam ~ ncy - a 5 in. x 0.5 in. x 0.125 in. ",e~
~s held by a 1/2 in. l.,andrLI, is bent at an angle of 90~ and held for 3
seCon~ls After release, the ,pc~ is allowed 2 min~-teS of
un ,Irei3ed recovery. The angle from the normal is then measured
and repo,led as resiliency. 0~ would COI ~titute cornpl~:e recovery
and "perfect" resiliency.
A sample is injection molded in an Van Dorn injection moldjng press into
standard parts for the vanious ASTM tests, then tested for selected m~h~n
p.upe.l,es.
Although the present invention has been descl,bed in considerable detail
with ~ ~,fe, c.,ces to certain prefe. I ~d versions thereof, other versions are possible.
Therefore, the spirit and scope of the appended claims should not be lirnited to the
description ofthe pref~. -ed versions contqinPd therein.
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TABLE I
Copolyrner ofCopolyrner of
Polymer Example 2F ,a ~le 3
Tensile Modulus (~a) 583 604
s TDC (1 1.8 Mpa load; time 480 sec) 5.3 3.15
Rma 1.0 1.68
Tensile Strength (Ultimate - MPa)38.0 43.7
Dart Impact Strength (Nm~mrn) 12.5 14.0
DSC Peak Melting Point ~C 121 126
