CA2234108A1 - Articles made from polypropylene, higher alpha-olefin copolymers - Google Patents
Articles made from polypropylene, higher alpha-olefin copolymers Download PDFInfo
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- CA2234108A1 CA2234108A1 CA002234108A CA2234108A CA2234108A1 CA 2234108 A1 CA2234108 A1 CA 2234108A1 CA 002234108 A CA002234108 A CA 002234108A CA 2234108 A CA2234108 A CA 2234108A CA 2234108 A1 CA2234108 A1 CA 2234108A1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/10—Homopolymers or copolymers of propene
- C08L23/14—Copolymers of propene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F210/04—Monomers containing three or four carbon atoms
- C08F210/06—Propene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/10—Homopolymers or copolymers of propene
- C08L23/14—Copolymers of propene
- C08L23/142—Copolymers of propene at least partially crystalline copolymers of propene with other olefins
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
- C08J2323/10—Homopolymers or copolymers of propene
- C08J2323/14—Copolymers of propene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2205/00—Polymer mixtures characterised by other features
- C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2314/00—Polymer mixtures characterised by way of preparation
- C08L2314/06—Metallocene or single site catalysts
Abstract
A molded or extruded article made from a propylene, .alpha.-olefin copolymer, where the .alpha.-olefin has 5 or more carbon atoms (higher alpha-olefins (HAO)), where the copolymer is made with a metallocene catalyst system, provides substantially higher cold flow resistance and resiliency than when the propylene copolymer contains an .alpha.-olefin of 4 or less carbon atoms. Other properties such as ultimate tensile strength and impact strength are substantially higher as well. Such polymers can be used to advantage in extruded profiles and molded parts either alone or in a thermoplastic olefin (TPO). Parts made from the propylene HAO copolymers or compounds made from them show improved creep resistance than propylene ethylene copolymers.
Description
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 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:
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 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.
~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 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 . .
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
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 ~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
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 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.
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 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 W 097119991 PCT~US96/19184 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 PCT~US96119184 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 W 097119991 PCT~S96/19184 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.
PCT~S96/19184 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 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 PCT~US96/19184 WO 97~19991 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 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.
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.
~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 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 . .
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
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 ~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
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 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.
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 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 W 097119991 PCT~US96/19184 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 PCT~US96119184 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 W 097119991 PCT~S96/19184 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.
PCT~S96/19184 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 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 PCT~US96/19184 WO 97~19991 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 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.
PCT~US961191~4 WO 9711g991 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
(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.
PCT~US961191~4 WO 9711g991 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
Claims (11)
1. An article comprised of an isotactic copolymer of propylene and at least one .alpha.-olefin having 5 or more carbon atoms;
said .alpha.-olefin being present in the said copolymer in the range of from 0.2to 6 mole percent based on the total moles of monomers in said copolymer, said copolymer having a Mw/Mn ~ 5, said copolymer having a peak melting point in the range of from 100°C to 145°C; and wherein an article made from said copolymer has an Rma of at least 1.1, preferably 1.2, more preferably 1.3, wherein
said .alpha.-olefin being present in the said copolymer in the range of from 0.2to 6 mole percent based on the total moles of monomers in said copolymer, said copolymer having a Mw/Mn ~ 5, said copolymer having a peak melting point in the range of from 100°C to 145°C; and wherein an article made from said copolymer has an Rma of at least 1.1, preferably 1.2, more preferably 1.3, wherein
2. An article as recited in Claim 1 wherein said article further comprises a second polyolefin, wherein said second polyolefin is selected from the group consisting of polyethylene, polypropylene and olefinic elastomers.
3. An article as recited in claim 1 wherein said .alpha.-olefin is selected from the group consisting of 1-pentene, 4-methyl-1-pentene, 1-hexene and 1-octene and wherein said .alpha.-olefin is present in the range of from 0.5 to 3 mole percent.
4. An article as recited in claim 1 wherein said propylene copolymer is produced using a metallocene catalyst system and wherein said copolymer has an Mw/Mn ~ 3.5.
5. An article as recited in claim 4 wherein said metallocene catalyst system contains a silicon bridged bis (substituted 2-methyl-indenyl) zirconium dichloride and methylalumoxane activator.
6. An article as recited in claim 1 wherein said copolymer further comprises an additional comonomer, selected from the group of .alpha.-olefin consisting of from 2 to 20 carbon atoms.
7. The article of claim 1 wherein said article is one of a film, a molded part, tubing, or sheet.
8. An article comprising at least a first isotactic propylene .alpha.-olefin copolymer, said .alpha.-olefin, being selected from the group consisting of 1-pentene, 4-methyl-1-pentene, 1-hexene and 1-octene;
said propylene .alpha.-olefin copolymer being polymerized by a metallocene-alumoxane catalyst system, wherein said metallocene is dimethyl silyl bis (2-methyl-benzindenyl) zirconium dichloride;
wherein said .alpha.-olefin is present in the range of from 1 to 3 mole percent based on the total moles of said propylene .alpha.-olefin copolymer, said copolymer has a Mw/Mn ~ 3; and said copolymer has a melting point in the range of from 115°C to 135°C.
said propylene .alpha.-olefin copolymer being polymerized by a metallocene-alumoxane catalyst system, wherein said metallocene is dimethyl silyl bis (2-methyl-benzindenyl) zirconium dichloride;
wherein said .alpha.-olefin is present in the range of from 1 to 3 mole percent based on the total moles of said propylene .alpha.-olefin copolymer, said copolymer has a Mw/Mn ~ 3; and said copolymer has a melting point in the range of from 115°C to 135°C.
9. A film comprising an isotactic copolymer of propylene, a first .alpha.-olefin and a second comonomer, said first .alpha.-olefin selected from the group consisting of 1-pentene, 4 methyl-1-pentene, 1-hexene and 1-octene;
said second comonomer selected from the group consisting of ethylene, 1-butene, 4-methyl 1-pentene, 1-hexene and 1-octene;
wherein said first .alpha.-olefin and said second comonomer are present in said copolymer in a combined total of said first .alpha.-olefin and said second comonomer in the range of from 0.5 to 3 mole percent, based on the total moles of monomers insaid copolymer;
wherein said copolymer has a Mw/Mn ~ 3;
wherein a film made from said copolymer has an extractable level less than 3 weight percent, and said film having an Rma of at least 1.2, wherein
said second comonomer selected from the group consisting of ethylene, 1-butene, 4-methyl 1-pentene, 1-hexene and 1-octene;
wherein said first .alpha.-olefin and said second comonomer are present in said copolymer in a combined total of said first .alpha.-olefin and said second comonomer in the range of from 0.5 to 3 mole percent, based on the total moles of monomers insaid copolymer;
wherein said copolymer has a Mw/Mn ~ 3;
wherein a film made from said copolymer has an extractable level less than 3 weight percent, and said film having an Rma of at least 1.2, wherein
10. A molded article comprising a propylene .alpha.-olefin copolymer, said .alpha.-olefin being selected from the group consisting of 1-pentene, 1-hexene and 1-octene;
said propylene .alpha.-olefin copolymer being made utilizing a metallocene catalyst system, wherein said metallocene is dimethyl silyl bis (2-methyl-benzindenyl) zirconium dichloride;
wherein said .alpha.-olefin is present in the range of from 1 to 2 mole percent;said copolymer has a Mw/Mn ~ 3;
said copolymer has a melting point in the range of from 115°C to 135°C;
wherein said copolymer is isotactic;
wherein a molded article made from said propylene .alpha.-olefin copolymer has an extractable level less than 3 weight percent, and wherein said molded article has an Rma exceeding 1.3, wherein
said propylene .alpha.-olefin copolymer being made utilizing a metallocene catalyst system, wherein said metallocene is dimethyl silyl bis (2-methyl-benzindenyl) zirconium dichloride;
wherein said .alpha.-olefin is present in the range of from 1 to 2 mole percent;said copolymer has a Mw/Mn ~ 3;
said copolymer has a melting point in the range of from 115°C to 135°C;
wherein said copolymer is isotactic;
wherein a molded article made from said propylene .alpha.-olefin copolymer has an extractable level less than 3 weight percent, and wherein said molded article has an Rma exceeding 1.3, wherein
11. The article of claim 10 wherein said article is selected from the group consisting of, a food container, a medical device, a syringe, and a vehicle part.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US56535195A | 1995-11-30 | 1995-11-30 | |
| US08/565,351 | 1995-11-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2234108A1 true CA2234108A1 (en) | 1997-06-05 |
Family
ID=24258238
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002234108A Abandoned CA2234108A1 (en) | 1995-11-30 | 1996-12-02 | Articles made from polypropylene, higher alpha-olefin copolymers |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0863943A1 (en) |
| JP (1) | JP2000501140A (en) |
| KR (1) | KR19990071757A (en) |
| CN (1) | CN1203614A (en) |
| BR (1) | BR9611669A (en) |
| CA (1) | CA2234108A1 (en) |
| MX (1) | MX9804215A (en) |
| WO (1) | WO1997019991A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4461872A (en) * | 1983-02-22 | 1984-07-24 | E. I. Du Pont De Nemours And Company | Blends of a propylene/α-olefin copolymer with isotactic prolypropylene |
| DE3904468A1 (en) * | 1989-02-15 | 1990-08-16 | Hoechst Ag | POLYPROPYLENE WAX AND METHOD FOR THE PRODUCTION THEREOF |
| JPH10503789A (en) * | 1994-05-24 | 1998-04-07 | エクソン・ケミカル・パテンツ・インク | Articles made from polypropylene, higher alpha-olefin copolymers |
-
1996
- 1996-12-02 WO PCT/US1996/019184 patent/WO1997019991A1/en not_active Application Discontinuation
- 1996-12-02 CN CN96198708A patent/CN1203614A/en active Pending
- 1996-12-02 EP EP96942122A patent/EP0863943A1/en not_active Withdrawn
- 1996-12-02 JP JP9520736A patent/JP2000501140A/en active Pending
- 1996-12-02 CA CA002234108A patent/CA2234108A1/en not_active Abandoned
- 1996-12-02 KR KR1019980704035A patent/KR19990071757A/en not_active Application Discontinuation
- 1996-12-02 BR BR9611669A patent/BR9611669A/en not_active Application Discontinuation
-
1998
- 1998-05-27 MX MX9804215A patent/MX9804215A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| EP0863943A1 (en) | 1998-09-16 |
| CN1203614A (en) | 1998-12-30 |
| WO1997019991A1 (en) | 1997-06-05 |
| MX9804215A (en) | 1998-09-30 |
| KR19990071757A (en) | 1999-09-27 |
| JP2000501140A (en) | 2000-02-02 |
| BR9611669A (en) | 1999-02-23 |
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