CA1141067A - Block copolymerization process and product - Google Patents

Abstract

BLOCK COPOLYMERIZATION PROCESS AND PRODUCT
ABSTRACT
A process for the preparation of ethylene-propylene block copolymers at high catalyst productivity rates resulting in polymer products having improved impact strength-polymerized ethylene content relationship. The polymer produced by the process exhibits improved physical and mechanical properties.

Description

BACKC.R~UND OF TH~ INVENTI~N

In block polymerization, there is substantially effect-ed a combination of the best physical and chemical properties of two or more polymers, for example, the combination of those of polyproplyene with those of polyethylene. Thus, polyethylene, while not possessing melting points or tensile stren~ths as high as those of polypropylene, does in fact possess excellent low temperature properties such as brittleness and impact: When the outstanding properties of both of these polymers are combined ~I in the technique of block pol~merizationf there results at once ¦ a heteropolymer useful in many applications for which neither homopolymer was practically useful.
A group of block copolymers, which have excellen~
physical properties, are the ethylene-propylene block copolymers, e.g. those of the type P-EP, where P denotes a propylene homo-polymer preblock and EP is a post-block of ethylene-propylene ; copolvmer. By v~rying the proportions of the blocks and the polymerized ethylene content, the physical properties can be closely controlled to fit the particular application for which the polymer products are intended. In general, at constant melt B ~
~l--flow rates the impact strength at roo~ temperature of the block copolymer is substantially directly proportional to the amount of polymerized ethylene in the total product.
Block copolymers are advantageously produced on a commercial scale by the process disclosed in U.S. Patent No.
3,514,501. Briefly, this process involves preparation of the preblock, preferably in the liquid phase, by catalytic poly-meri~ation of propylene in a hydrocarbon diluent such as liquid ; propylene to form a slurry. After separation of the slurry, the prepolymer which still contains active catalyst residues is introduced into at least one reaction zone, where it is reacted with monomer vapors for a sufficient period of time to form the polymer post block onto the polymer preblock in the desired proportions.
In the past, the conventional catalyst system used in such a polymerization process has been an unmodified or an electron donor-modified titanium halide component, activated with an organoaluminum cocatalyst. Typical examples of con-ventional propylene polymerization catalyst systems include cocrystallized titanium trichloride-aluminum trichloride catalysts of the general formula n.TiC13.AlC13 activated with diethyl aluminum chloride or triethyl aluminum. The cocryst-allized titanium trichloride-aluminum trichloride can have been subjected to a modification treatment with a suitable electron donor compound to increase its activity or stereospecificity.
Such compounds include phosphorus compounds, esters of inorganic and organic acid ethers and numerous other compounds.
One major drawback, however, in using the aforementioned conventional catalysts, has been the low catalyst productivity, which has necessitated the subse~uent deashing of the product to reduce the content of catalyst residues, which otherwise would detrimentally affect the product quality.
Recently new catalysts have ~een developed which are - 2a -, far more active than the aforementioned conventional satalysts in the polymerization of alpha-olefins. Briefly described, ,~ these catalysts are comprised of a titanium halide catalyst , component suppcrted on maanesium dihalide and an alkylaluminum 1I compound, which can be present as a complex ~ith an electron ' donor compound. These catal~st components have been described in the patent literature, e.y. in U.S. Patents No. 3,830,787, j No. 3,953,414, No. 4,051,313, No. 4,115,319 and No. 4,149,990.
¦ The productivities obtained with these new catalysts ¦j are extremely high resulting in polymers containing such small quantities of residual catalyst that the conventional deashing ~¦ step can be dispensed with. The catalysts function well in the Il homopolymerization of propylene and in the copolymerization of ¦l a mixture of propylene and another alpha-olefin such as ethylene, ¦
, provided that the polymerization reaction is carried out in a ¦¦ liquid diluent, e.g. liquid propylene monomer. However, in the ¦¦ vapor phase polymerization used in preparing the EP copolymer 1¦ block of P-EP block copolymer described above, using convention-,, al operating conditions, 1~ has been found that the product ~ !~ quality of the resulting block polymer has been substantially ¦l inferior. Specificially, in order to achieve a desired impact ¦I strenyth at a desired melt flow, it was found that considerably ¦¦ more ethylene had to be in~orporated into,the total polymer than is the case when employing conventional catalysts. The I necessary increase in ethylene content to achieve the impact strength detrimentally a~fects other desirable properties of the final product such as stiffness, heat deflection temperature, ¦ tensile properties, etc.
! I-t is therefore an ob1ect of the present invention to , provide a hiyhly e ficient process for the vapor phase poly-merization of ethylene-propylene blocks onto a preformed propy-lene polymer yielding polymer Froducts having improved impact ~`
strength ~ithout siyllificant1~ affectiny other desirable .
, Il physical polymer properties.
1, ~nother object of the invention is to provide a process for the preparation of ethylene-propylene block co-, polymers wherein the polymerized ehtylene content of the ,otal il polymer product is minimized to achieve a desired impact jl strength.
~, Still another object of the present invention is to provide a novel ethylene-propylene block copolymerswhich ex-hibits improved processability when extruded or injection mold-!~ ed as compared to conventional ethylene-propylene block co-polymers of the same total ethylene content-. ¦
Another object of the present invention is to provide ¦ a novel ethylene-propylene block copol~mer which can be proces-¦¦ sed at lower extrusion or molding temperatures and/or lower ,¦ extrusion or molding pressures than conventional resins of the same meltflows and total ethylene content.
Further objects will become apparent from a reading of ¦¦ the specification and appended claims.
'11 I THE IN~IENTION

; 20 The above objects are accomplished in a continuous I, sequential vapor phase block copolymerization process which I comprises: I,i (A) providing a preformed propylene polymer in finely divided ¦I form, said preformed polymer containing active catalyst 25 1¦ residues and having been prepared by polymerizing propylene ¦l in the presence of a catalyst composition containing the components (a) an aluminum trialkyl or an alurninum trialkyl at least , partially complexed with an electron donor componnd, and l~
(b) titallium tri- or tetrahalide supported on magneslum "

~ I

31 ~41~67 dihalide, or a complex of a titanium tri- or tetra-halide with an electron donor compound supported on magnesium dihalide;
Il (B~ introducing said preformed polymer into at least one 5 ¦¦ continuously agitated reaction zone, (C) introducing ethylene and propylene monomers to said reaction zone in a molar ratio of ethylene to propylene of from about 0.15 to about 0.3, ~ (D) polymerizing said ethylene and propylene monomers in the 1I vapor phase in the reaction zone onto said preformed ! propylene prepolymer.
,i As used throughout this specification and the claims ¦¦of this invention, the following terms are intended to have the Il following meanings:
15ll (a) "preformed polymer" means a propylene polymer which ¦ is suitable for independent use, but which contains ¦¦ active catalyst residues;
~1 (b) "active catalyst residues" as used herein indicates catalytic components in the polymer which function 20 j to polymerize added monomeric substances ~ithout ¦ the need of adding further quantities of catalyst.
¦I The active catalyst residues referred to herein are ¦~i preferably those initially employed in the poly-Il merization to produce the preformed polymer;
25i, (c) a "block polymer" has the same significance as hereto-! fore understood in the prior art, that is, a polymer . j molecule consisting of a single section of an alpha-l olefin polymer or copolymer attached to a single I section of another alpha~olefi.n polymer or copol~me~-.

Bloc]~ polymers are i.ntended to include t~o or more co-polymers sequen.ially polymerized one onto the o.`ner;
a homopolymer followed by a co~olymer, or al~erna~
holno or copolymer bloc~s of t~o or more alph.~-ole-i,n 1, ;!
rnonomers;
', (d) "~701atile constituents" include unpolymerized alpha- j olefin monomers, as well as inert hydrocarbon diluents such as ethane, propane, butane, pentane, hexane, l heptane, octane, aromatic hydrocarbons, diesel oils Il and the like;
,~ (e) by polymerization in a "hydrocarbon diluent", it is intended that polymerization can occur in the presence ~¦ of inert hydrocarbon diluents such as those named above in (d) or polymerizations wherein the monomer, ¦i i.e. propylene, under conditions of temperatures and pressure is kept in liquid form during the polymeriz-jl ation, thereby servin~ as its own dispersing medium or mi~ture of inert hydrocarbons and olefin monomers in ¦l liquid form;
(f~ by "vapor phase" block polymerization and "substantial-ly dry prepolymer" it is intended to mean that a pre-formed polymer contains in the order of 5% or less of volatile constituents, is reacted with gaseous monomers ;~ 20 1! in the absence of added inert hydrocarbon diluents.
Propylene, optionally in admixture with mlnor amounts ¦ of other alpha-olefins of from about 2 to 10 carbon atoms or ¦ more can be employed to form a prepolymer. Such other alpha-olefins include ethylene, hutene-l, isobut~éne-l, pentene-l, I~ hexene-l, and hiqher, as well as branched alpha-olefins such as ¦l 2-methyl butene-l, 4-methyl pentene-l and hi~her. Of these ~¦ monomers, propylene and mixtures of propylene and ethylene are ¦ of special interest and most preferred. When ethylene is a 1~ component, it is preferred that it be limited to a concentration ~ of from about 0.3 to about 2 ~it ~ of the total monomer feed.
The prepolymer is formed in a reaction zone employin~

a hydrocarbon diluent and a catalyst for the polymerization, carryin~ out the polymerizatioo to a solids content of from 5 to , ~. ~

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4~06~
60~, but preferably 20 to 40~. The preferred diluent is li~uid propylene.
In the preferred process for the prepolymer formation, i.e. the well known "liquid pool" process, the propylene functions as the liquid diluent as well as feed to the reaction, except for small quantities of inert hydrocarbons, e.g. hexane, mineral oil, petrolatum, etc., that may be used for the intro-duction of the catalyst components into the reaction zone.
The reaction is continuous and monomer feed and catalyst components are continuously fed to the reactor and a slurry of polymer product and liquid propylene is withdrawn, preferably through a cyclic discharge valve which simulates continuous operation. Various modifiers such as hydrogen may be added to alter the properties of the polymer product. Such modifiers are well known in the art and need not be discussed in any further detail since they form no part of this invention.
The catalyst components used in the process for pre-paring the prepolymer can be any one of the recently developed, high activity magnesium halide supported catalyst components and organoaluminum cocatlayst components disclosed e.g. in ~.S.
Patents No. 3,830,787, No. 3,953,414, No. 4,051,313, No. 4,115, 319, and No. 4,149,990.

Typically, such a catalyst composition is a two component composition where the components are introduced separately into the polymerization reactor. Component (a) of such a composition is advantageously selected from trialkyl aluminums containing from 1 to 8 carbon atoms in the alkyl group, such as triethyl aluminum, trimethyl aluminum, tri-n-butyl aluminum, tri-isobutyl aluminum, triisohexyl aluminum, tri-n-octyl alumirum and triisooctyl aluminum. Most preferably, the trialkyl aluminum is complexed ~ith an electron donor prior to introduction into the polymerization reactor. Best results are ,~

6~7 achieved when esters of carboxylic acids or diamines, particular-ly esters of aromatic acids are used as the electron donors.
Some typical examples of such compounds are methyl-and ethylbenzoate, methyl- and ethyl-p-methoxybenzoate, diethyl-carbonate, ethylacetate, dimethylmaleate, triethylborate, ethyl-o-chlorobenzoate, ethylnaphthenate, methyl-p-toluate, ethyl-toluate, ethyl-p-bu~oxy benzoate, ethyl-cyclohexanoate, ethyl-pivalate, N,N,N',N'-tetramethylenediamine, 1,2,4,-trimethyl-piperazine, 2,5-dimethylpiperazine and the like. The molar ratio of aluminum alkyl to electron donor can range between 1 and 100, preferably between 2 and 5. Solutions of the electron donor and the trialkyl aluminum compound in a hydrocarbon such as hexane or heptane are preferably prereacted for a certain period of time generally less than 1 hour prior to feeding the mixture into the polymerization reaction zone.
The other component of the catalyst composition is either a titanium tri-or tetrahalide supported on magnesium dihalide, or a complax of a titanium tri-or tetrahalide with an electron donor compound supported on magnesium dihalide. The halogen in the respective halides can be chlorine, bromine or iodine, the preferred halogen being chlorine. The electron donor, if it is used in forming a complex, is suitably selected from the esters of inorganic and organic oxygenated acids and the polyamines. Examples of such compounds are the esters of aromatic carboxylic acids, such as benzoic acid, p-methoxybenzoic acid and p-toluic acids and particularly the alkyl esters of said acids; the alkylene diamines, e.g. N',N",N"', N""-tetramethylethylene-diamine. The Magnesium to electron donor molar ratio are equal to or higher than 1 and preferably 3~ between 2 and 10. Generally the titanium content expressed as ~s~
~ 8 ~

6~

titanium metal ranges between 0.1 and 20 wt % in the supported catalyst component and preferably between 1 and 3 wt ~.
The preparation of such supported catalyst components - 8a ~

~14~7 has been described in the prior art and are commerclally avail- ¦
able.
The catalyst components (a) and (b) are fed to the ' prepolymer reaction zone in amounts such that the Al/Ti molar ~, il ratio is maintained in the broad range between about 1 and about 10,000 and preferably between about 10 and 200.
! Temperatures at which the prepolymer formation can be Ii carried out are those known in the art, for example, from 50 to ¦¦ 250F~ preferably from 115 to 165F and most preferably from l 125F to about 155F. The pressures in the prepolymer formation ¦ can range from atmospheric or below where normally liquid inert I j! hydrocarbon diluents are used (heptane or hexane) to pressures i up to 500 psig or higher where propylene is used as its own dispersing agent or the propylene in admixture with a normally ~15 gaseous hydrocarbon diluent such as propane or butane, which ¦ are liquid under the conditions of the reaction.
- I¦ The prepolymer from the reaction zone is taken to a ~ ¦I separation zone, sach as a cyclone or a bag filter, wherein the ; ¦¦ volatile constituents are separated from the polymer and proces-1 sed according to known techniques and recycled to the reaction zone, the amount of volatiles removed being su~ficient so that ¦ less than 10% and preferably no more than 5~ volatile content remains in the prepolymer. , ~, In the vapor phase block polymerization, the polymer ~I recovered from the separation zone and containing active catalyst residues, is taken to a continuously agitated reaction Il zone containing provisions therein for introducing the ethylene ¦¦ monomer and propylene monomer at one or more points along the j' length of the zone (and inert gases such as nitrogen) so that ~ the active catalyst residues in the prepolymer polymerize said mono~ers to a block thereby modifying the ultimate properties of the resin produced. The polymeri~ation in the continuousl~ I
a~itated reaction zone is ~lenerally carried out at press~lres ;'' ,ii ,, ~
_ q 1, ll ~14~

lower than those used for the prepolymer preparation, i.e.
pressures of 10 to 50 psig or somewhat higher. Polymerization temperatures can range, for example, from about 50~F to about 210F, but preferably from about 130 to about 200F.
The ethylene and propylene monomers do not require premixing prior to introduction into the vapor phase zone; in fact, it is more advantageous to separately introduce each of the monomers at one or preferably several points along the reactor length. Liquid propylene can be introduced, which upon vaporization will remove some of the heat of polymerization generated in the reaction zone. The molar ratio of the total ethylene to total propylene introduced to the reaction zone should, however, be restricted within the range of ~rom about 0.15 to about 0.3. If higher ratios are employed, it has been found that the effectiveness of the ethylene content in the total polymer product on the impact properties is severely de-creased. For instance, at a ratio of 0.5 it is required to incorporate about twice the amount of ethylene into the total polymer in order to obtain the same impact strength as that of a final product prepared at a ratio o about 0.2.
Generally from about 5 to about 40 percent by weight of block based on the weight of the total polymer is produced in the total block poly~erization reactor system.
Suitable continuously agitated reaction zones include those disclosed in U.S. Patent No. 3,514,501.
The reaction zone can be one or more pipe line reactors in series with optional jacketing for heat removal and suitable monomer introduction points as ~ell as agitating means. According to the preferred embodiment of this invention, one or more horizontal ribbon blender reactors are provided for the continuous operation. Such reactors are equipped internally with a series of ribbon blades and/or paddles rotated by a power drive. By suitable arran~ement of ; I the agitation equipment the polvmer can be moved continuously from the inlet to the outlet. The polymer powder substantially independent of any agitation, behaves much like a fluid and "flows" or moves from the inlet end of the reactor to the out-1 let end, that is, flo~s along -the length of the reactor in ¦I much the same manner as a fluid like a liquid would.
¦ Propylene is provided at-]east to the inlet of tne reactor and if liquid propylene monorner is used, it is prefer- !
¦ ably also provided through inlet spray nozzles spaced along the I upper portion of the reactor. Ethylene monomer feed in vapor form can be introduced in similar fashion at points along the ¦! length of the reactor. The reactor is advantageously provided i with an external cooling jacket for removal of heat through the ¦ reactor wall. Additional vapor-phase reactors can be provided 11 in series wlth the block polymerization reactor for the purpose Il of increasing residence time. If desired, any of the various ¦I known modifiers may be added to one or more reactor for their intended purpose.
Because of the generally high productivity of the ¦¦ supported catalyst system expressed in terms of pounds of ¦I polymer produced per pound of titanium metal r which productivity has been further enhanced by the present invention, there is no I need to remove catalyst residues from the polymer in a deashing ¦ step as is the case ~ith conventional catàlyst.

2 I The polymer products provided in accordance with ¦ this invention and produced by the preferred "liquid pool"
li method have a meltflow range between about 0.1 and about ¦¦ 10 g/lOmin., ratio of weight-average molecular weignt to ~I number-average rnolecular weight of above about 6.5, ethvlene

3 content of at least about 1 preferrabl~- above about d w. Q`, Ti content not exceeding about 3ppm, .~g content not exceeding , about 40ppm, C1 contellt not exceeding about lOOpprn and to~al ~sh content not exceeding about 4no~p~.

6~

Specific advantages of the ~olymers of this invention ' compared to conventional po1vmers include wider ~rocessabilit.y range, lo~^~er processing energy re~uire~ents, superior ability ~I to fill thin sections and multiple cavitv molds, better draw-ll down, easier drawabilitv and higher processing speed in the ¦¦ continuous filament and staple fiber ~roduction.
1, For example, hased on spiral meltflow measurements, i it was found that polymers o.f this invention having meltflows I (ASTM-1238 Condition L) in the range of about 2-lOg/lOmin. can be processed at 50~30F lower molding temperatures, or 350-150 I psi lower molding pressures than conventional polymers of the !I same meltflows (ASTM-1238) and total ethylene content.
I It is believed that the molecular weiqht distribution, ¦
1l Mw/Mn is the ~roperty that best relates to the improvements in 1l impact strength as well as polymer rheological properties and !I Drocessability. Typically, polymerization with a conventional Y !¦ catalyst system would result 1n a polymer product having a ¦I Mw/Mn ratio of at most 6.5 and generally below 6, while the polymers of this invention have Mw/~n ratios of at least 6.5 2~ j e.g. between about 7 and about 10.
Various additives can, i.f desired, be incorporated ¦ into the polypropylene resin, such as fibers, fillers, anti-¦ oxidants, metal deactivating agents, heat and light stabilizers, ~ dyes, pi~ments, lubricants and the like.
Ij The polymers can be used with advantaqe in the , manufacture of fibers, filaments and films by extrusion; of ! rigid articles by injection moldinq; and of bottles by blow ¦l molding techniques.
'~ The followinq examples further illustrate the advantages obtained by the invention.

., I~-l2- , E~MPLES 1-7 ` The experiments were conducted in large scale contin-uous pilot plant operations. For the prepolymer pre~aration, propylene and catalyst components were continuously charged to a stirred reactor, the monomer feed rate was adjusted correspond ing to 2 hours residence time in the reactor. The organo-aluminum compound G~ the catalyst system was a hexane solution of triisobutyl aluminum (TIBA) which had been treated prior to 1~ introduction into the reactor with a hexane solution of methyl-p-toluate 5MPT), an electron donor ~ompound. The solid support-ed titanlum hal~e cata~yst ox~nent was a o~c~ly available catalyst.
The supported catalyst component contained about 1.5 wt titanium, 20.3 wt % magnesium, 60.0 wt % chlorine and 9.6 wt %
hydrocarbon volatiles. Ethylbenzoate had been used in the manufacture of ~he supported catalyst-component. The two catalyst compvnents were added at ra~es directly proportional to the polymer produ~tion rates and in amounts su~ficient to main-tain a polymer ~olids concentration in the reactor slurry at a 2Q nominal value of about 40%. The catalyst productivity (lb polymer/lb of Ti metal) was calculated in each case from the polymer slurry withdrawal rate, solids content in the slurry and the ti anium catalyst component addition rate.
After separation of ~he prepolymer from unreacted propylene, ~aid prepolymer which still contained active catalyst residues was fed sequentially to two serially connected, water-csoled jacketed horizontal reactors, each provided with ribbon blades as agitation means. Pro~ylene was introduced near the inlet of each of the reactors and ethvlene monomer 3~ through three inlets spaced evenly across each of the reactors.
The block copolymer product was recovered from the outlet o~
the second reactor. ~he operating conditions in each of the ~' reactors were essentially the same unless otherwise noted.
Pertinent operating conditions and results are shown in Table 1 In the Figure, the relationship of wt % ethylene in the product !
1 is plotted against the notched Izod impact strength (at room 1I temperature). Curve A denotes the typical relationship ob- ¦
¦l tained when preparing the prepolymer with conventional catalys "
e.y. Stauffer ~A catalyst (3~iC13 AlC13) with diethyl aluminum chloride as cocatalyst (at Al/Ti molar ratio of about 3) and ~¦ under conditions to produce a final product melt flow of about ¦¦ 2 grams/10 mins. It has been found that in such a conventional ; ,I process the ethylene/propylene molar ratios used in the vapor l~ phase reaction zone may be varied considerably, e.g. from about ¦¦ 0.2 - 0.8, without having any material effect on the relation-` ¦! ship shown by curve A.
1! Curve B depicts the ethylene content I~od impact ¦! strength relationships obtained in Comparative Examples 1-6. The ¦ polymers of these examples were all prepared with a catalyst of ¦¦ the composition required in this invention, however, the vapor II phase block copolymerization reactions were each carried out ~l at ethylene/propylene ratios outside the limits of this invent-¦l ion. As seen from curve B of the graph, the ethylene incorporat-¦l ed in each of the block copolymers was not very efficient in ¦l achieving impact resistance; in fact, about double the ethylene I incorporation is needed to obtain products of a desired impact 1l as compared to conventionally prepared block copolymers (curve A).
Example 7, however, which was prepared according to ¦ the present invention, resulted in a block copolymer having a much improved ethylene content-impact resistance relationship (point is indicated in the Figure).

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EX~PLES 8 Ar~7~ 9 ~, ¦ p The polymer products from two continuous polymerization runs conducted essentially according to the technique described 1l in Examples 1 - 7 were subjected to a detailed analysis except j that 1.4 mol percent ethylene was present in the prepolymer reactor feed stream in Example 9 and triethyl aluminum was used ; 1l as the cocatalyst. The results are shown in Table 2 together ¦¦ with pertinent operating conditions.
¦¦ As indicated in Table 2, standard ASTM test methods lG ~~! were used to determine the majority of the properties of the ~` polymer products.
The Mw/~n ratio was determined by liquid chromatography using o-dichlorobenzene as solvent.
The contents of Ti, Mg and Al were determined by 1 atomic absorption analysis of polymer ash dissolved in hydro-chloric acid and the chlorine content by colorimetric determinat-on of combusteù polyLer san~le uslng a Parr oxygen bomb.

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Il -l6-i EX~1~5PLE NO. 8 9 Catalyst FT-1 FT-l Alkyl aluminum TEA TEA
Trialkyl aluminum/MPT-mol ratio 3.4 3.1 Al/Ti-mol ratio 150 150 First Reactor Temperature F 130 130 Pressure - psig 335 350 Residence Time - hrs. 1.7 1.7 E/P mol. ratlo - 0.014 Productivity kg/gTi 353 437 Second Reactor Temperature F 175 175 Pressure - psig 40.7 40.
Residence Time - hrs. 2.0 2.0 E/P mol. ratio 0.3 0.3 . Additives:
BHT - ppm 1200 1200 Irganox 1010-ppm 500 500 Calcium stearate-ppm 1000 1000 Hydrotalcite-ppm1000 1000 Properties:
Total ethylene content - wt % 4.2 6.7 Melt Flow g/lOmin. (1) 0.8 2.1 Density gm/cc (2) 0.897 0.895 Mn 46,100 38,000 30 Mw 367,000 325,000 Mw/Mn 8.0 8.6 * Trademark ,.,"~

ll TABLE 2 (CONTINUED) ~ - !
. EX~IPLE_NO. 8 9 Tensile Strength .
~ @ Yield - psi (3) 4290 3S30 ¦l @ Break - psi (3) 3080 3015 . Elongation at ~ Break - ~ (3) 516 485 il Flexural ;ioclulus-!' psi x 105 (4) 1. 55 1.16 ; 10 Tensile Modulus- ¦
psi x 105 (3) 1.67 1.29 HDT - at 66 psi C (5) 81 80 Crystalline Melting Point - C 168 162 . Hardness --(Rockwell) (6) 51.5 38.4 LTB - C (7) -12.8 -20. 4 Izod Impact ll ft lbs/in (8) 5.2 5.4 i!
il Polymer Impur.ities:
¦~ Ash - ppm 395 350 ! Mg - ppm 37 33 I Ti - ppm 3 2 , C1 - ppm 98 95 A1 - ppm 255 194 j~ (1) ASTP1 D1238, Cond. L (2) ASTN D1505 l~ (3) ASTM D638 (4) ASTM D790 ; ll (5) ASTP~ D648 t6) ASTM D785 (7) AST!~I D746 ~8) ASTM D256 I

! , It is obvious to those skilled in the art that ~an~
variations and modi-ications can be made to the pro~ylene poly~er ! of this invention ~11 such departures from the .oregoing specification and considered within the scope of this invention 5 1l as defined bv the specification and the appended claims.

Claims (23)

WHAT IS CLAIMED IS:

1. A propylene-ethylene block copolymer having a melt-flow range between about 0.1 and 10 g/10 min., ratio of weight-average molecular weight to number-average molecular weight (Mw/Mn) above about 6.5, polymerized ethylene content above about 1.0, Ti content not ex-ceeding about 3 ppm, Mg content not exceeding about 40ppm, Cl content not exceeding about 100ppm and total ash content not exceeding about 400ppm.

2. The polymer of claim 1, obtained in a process compris-ing:
(A) providing a preformed propylene polymer in finely divided form, said preformed polymer containing active catalyst residues and having been prepared by polymerizing propylene in the presence of a catalyst composition containing the components:
(a) an aluminum trialkyl or an aluminum trialkyl at least partially complexed with an electron donor compound selected from an ester of a car-boxylic acid or a diamine, in a molar ratio of trialkyl aluminum to electron donor between about 1 and about 100, and (b) titanium tri- or tetrahalide supported on mag-nesium dihalide, or a complex of a titanium tri- or tetrahalide with an electron donor, compound supported on magnesium dihalide, wherein the electron donor compound is a polyamine or an ester of an inorganic or an organic oxygenated acid, and wherein the magnesium to electron donor compound molar ratio is at least about 1;

(B) introducing said preformed polymer into at least one continuously agitated reaction zone;
(C) introducing ethylene and propylene monomers to said reaction zone in a molar ratio of ethylene to propylene of from about 0.15 to about 0.3;
(D) polymerizing said ethylene and propylene monomers at a temperature from about 50°F. to about 210°F.
in a vapor phase in the reaction zone onto said preformed propylene prepolymer.

3. A block copolymer according to claim 2, wherein the preformed propylene polymer is produced in a poly-merization zone under sufficient pressure to maintain propylene in liquid phase.

4. A block copolymer according to claim 2, wherein the preformed propylene polymer is propylene homopolymer.

5. A block copolymer according to claim 2, wherein the preformed propylene polymer is a random ethylene-propylene copolymer.

6. A block copolymer according to claim 2, wherein the alkyl group of the aluminum trialkyl catalyst in component (a) contains from 1 to 8 carbon atoms.

7. A block copolymer according to claim 2, wherein the aluminum trialkyl catalyst in component (a) is tri-isobutyl aluminum.

8. A block copolymer according to claim 2, wherein the aluminum trialkyl catalyst in component (a) is triethyl aluminum.

9. A block copolymer according to claim 2, where the electron donor compound of component (a) of the catalyst composition is an ester of a carboxylic acid or a diamine.

10. A block copolymer according to claim 9, wherein said electron donor is an ester of an aromatic acid.

11. A block copolymer according to claim 10, wherein the ester is methyl-p-toluate.

12. A block copolymer according to claim 2, wherein the molar ratio of trialkyl aluminum to electron donor is between about 2 and about 5.

13. The block copolymer of claim 2, wherein component (a) is prepared by prereacting the aluminum trialkyl with the electron donor for less than one hour prior to polymerization.

14. The block copolymer of claim 2, wherein the titanium tri- or tetrahalide is a titanium trichloride or titanium tetrachloride.

15. The block copolymer of claim 2, wherein the magnesium dihalide is magnesium dichloride.

16. The block copolymer of claim 2, wherein the electron donor compound of component (b) is a polyamine or an ester of an inorganic or an organic oxygenated acid.

17. The block copolymer of claim 16, wherein said electron donor is an ester of an aromatic carboxylic acid.

18. The block copolymer of claim 17, wherein the ester is ethylbenzoate.

19. The block copolymer of claim 2, wherein the molar ratio of the magnesium to electron donor is between about 2 and about 10.

20. The block copolymer of claim 2, wherein the titanium content expressed as titanium metal ranges between about 0.1 and about 20 weight percent in the supported catalyst component (b).

21. The block copolymer of claim 18, wherein the titanium content is between about 1 and about 3 weight percent.

22. The block copolymer of claim 2, wherein catalyst components (a) and (b) are provided to the reaction zone in a molar ratio of Al/Ti of between about 1 and about 10,000.

23. The block copolymer of claim 2, wherein said Al/Ti molar ratio is between about 10 and about 200.