Molecular weight distribution modification in a tubular reactor

Polymodal MWD ethylene copolymer comprising at least two modes of differing molecular weights. Each mode has at least one of M.sub.w /M.sub.n of less than 2.0, and a M.sub.z /M.sub.w of less than 1.8. The polymodal character of the copolymer is achieved by either (1) withdrawing polymer modes from the reactor from at least one takeoff port, and blending such modes with the reactor effluent, or (2) utilizing at least two catalyst species in the reaction to produce modes of differing molecular weights.

BACKGROUND OF THE INVENTION 
The present invention relates to novel copolymers of alpha-olefins. More 
specifically, it relates to novel copolymers of ethylene with other 
alpha-olefins comprised of copolymer chains with compositions which are 
intramolecularly heterogeneous and intermolecularly homogeneous, as well 
as to a process for making these copolymers and their use in elastomer 
applications. In particular, it relates to polymers having a polymodal 
molecular weight distribution wherein individual modes of the polymer 
comprise narrow molecular weight distributions copolymer chains with 
compositions which are intramolecularly heterogeneous and intermolecularly 
homogeneous. 
For convenience, certain terms that are repeated throughout the present 
specification are defined below: 
A. Inter-CD defines the compositional variation, in terms of ethylene 
content, amond polymer chains. It is expressed as the minimum deviation 
(analogous to a standard deviation) in terms of weight percent ethylene 
from the average ethylene composition for a given copolymer sample needed 
to include a given weight percent of the total copolymer sample which is 
obtained by excluding equal weight fractions from both ends of the 
distribution. The deviation need not be symmetrical. When expressed as a 
single number, for example, 15% Inter-CD, it shall mean the larger of the 
positive or negative deviations. For example, for a Gaussian compositional 
distribution, 95.5% of the polymer is within 20 wt % ethylene of the mean 
if the standard deviation is 10%. The Inter-CD for 95.5 wt % of the 
polymer is 20 wt % ethylene for such a sample. 
b. Intra-CD is the compositional variation, in terms of ethylene, within a 
copolymer chain. It is expressed as the minimum difference in weight (wt) 
% ethylene that exists between two portions of a single copolymer chain, 
each portion comprising at least 5 wt% of the chain. 
c. Molecular weight distribution (MWD) is a measure of the range of 
molecular weights within a given copolymer sample. It is characterized in 
terms of at least one of the ratios of weight average to number average 
molecular weight, M.sub.w /M.sub.n, and Z average to weight average 
molecular weight, M.sub.z /M.sub.w, where: 
##EQU1## 
Ni is the number of molecules of weight Mi. 
d. Viscosity Index (V.I.) is the ability of a lubricating oil to 
accommodate increases in temperature with a minimum decrease in viscosity. 
The greater this ability, the higher the V.I. 
Ethylene-propylene copolymers, particularly elastomers, are important 
commercial products. Two basic types of ethylene-propylene copolymers are 
commercially available. Ethylene-propylene copolymers (EPM) are saturated 
compounds requiring vulcanization with free radical generators such as 
organic peroxides. Ethylene-propylene terpolymers (EPDM) contain a small 
amount of non-conjugated diolefin, such as dicyclopentadience; 
1,4-hexadiene or ethylidene norbornene, which provides sufficient 
unsaturation to permit vulcanization with sulfur. Such polymers that 
include at least two monomers, i.e., EPM and EPDM, will hereinafter be 
collectively referred to as copolymers. 
These copolymers have outstanding resistance to weathering, good heat aging 
properties and the ability to be compounded with large quantities of 
fillers and plasticizers resulting in low cost compounds which are 
particularly useful in automotive and industrical mechanical goods 
applications. Typical automotive uses are tire sidewalls, inner tubes, 
radiator and heater hose, vacuum tubing, weather stripping and sponge 
doorseals and Viscosity Index (V.I.) improvers for lubricating oil 
compositions. Typical mechanical goods uses are for appliance, industrial 
and garden hoses, both molded and extruded sponge parts, gaskets and seals 
and conveyor belt covers. These copolymers also find use in adhesives, 
appliance parts as in hoses and gaskets, wire and cable and plastics 
blending. 
As can be seen from the above, based on their respective properties, EPM 
and EPDM find many, varied uses. It is known that the properties of such 
copolymers which make them useful in a particular application are, in 
turn, determined by their composition and structure. For example, the 
ultimate properties of an EPM or EPDM copolymer are determined by such 
factors as composition, compositional distribution, sequence distribution, 
molecular weight, and molecular weight distribution (MWD). 
The efficiency of peroxide curing depends on composition. As the ethylene 
level increases, it can be shown that the "chemical" crosslinks per 
peroxide molecule increases. Ethylene content also influences the 
rheological and processing properties, because crystallinity, which acts 
as physical crosslinks, can be introduced. The crystallinity present at 
very high ethylene contents may hinder processibility and may make the 
cured product too "hard" at temperatures below the crystalline melting 
point to be useful as a rubber. 
Milling behavior of EPM or EPDM copolymers varies radically with MWD. 
Narrow MWD copolymers crumble on a mill, whereas broad MWD materials will 
band under conditions encountered in normal processing operations. At the 
shear rates encountered in processing equipment, broader MWD copolymer has 
a substantially lower viscosity than narrower MWD polymer of the same 
weight average molecular weight or low strain rate viscosity. 
Thus, there exists a continuing need for discovering polymers with unique 
properties and compositions. This is easily exemplified with reference to 
the area of V.I. improvers for lubricating oils. 
For elastomer applications the processibility is often measured by the 
Mooney viscosity. The lower this quantity the easier the elastomer is to 
mix and fabricate. It is desirable to have low Mooney yet to maintain a 
high number average molecular weight Mn so that the polymers form good 
rubber network upon cross-linking. For EP and EPDM narrowing, the 
molecular weight distribution results in the production of polymer with 
higher number average molecular weight at a given Mooney. In certain 
cases, the poor milling or calendering or extrusion behavior that results 
from the narrow MWD must be ameliorated. Rather than perform a MWD 
broadening which includes low molecular weight components which reduce Mn, 
it is possible to broaden the MWD without disproportionately lowering Mn. 
This is done by superposing one or more narrow MWD modes, i.e., different 
Mooney components, each of which contains no low molecular weight polymer. 
The result is a polymodal molecular weight distribution comprised of 
narrow MWD polymer fractions of different molecular weights. 
The present invention is drawn to a novel copolymer of ethylene and at 
least one other alpha-olefin monomer which copolymer is intramolecularly 
heterogeneous and intermolecularly homogeneous. Furthermore, it is 
composed of several such components, the MWD of each which is very narrow. 
It is well known that the breath of the MWD can be characterized by the 
ratios of various molecular weight averages. For example, an indication of 
the narrow MWD of each component in accordance with the present invention 
is that the ratio of weight to number average molecular weight (M.sub.w 
/M.sub.n) is less than 2. Alternatively, a ratio of the Z-average 
molecular weight to the weight average molecular weight (M.sub.z /M.sub.w) 
of less than 1.8 typifies a narrow MWD in accordance with the present 
invention. It is known that the property advantages of copolymers in 
accordance with the present invention are related to these ratios. Small 
weight fractions of material can disproportionately influence these ratios 
while not significantly altering the property advantages which depend on 
them. For instance, the present of a small weight fraction (e.g., 2%) of 
low molecular weight copolymer can depress M.sub.n, and thereby raise 
M.sub.w /M.sub.n above 2 while maintaining M.sub.z /M.sub.w less than 1.8. 
Therefore, polymers, in accordance with the present invention, are 
characterized by having at least one of M.sub.w /M.sub.n less than 2 and 
M.sub.z /M.sub.w less than 1.8. The copolymer comprises chains within 
which the ratio of the monomers varies along the chain length. To obtain 
the intramolecular compositional heterogeneity and narrow MWD, the 
copolymers in accordance with the present invention are preferably made in 
a tubular reactor. It has been discovered that to produce such copolymers 
requires the use of numberous heretofore undisclosed method steps 
conducted within heretofore undisclosed preferred ranges. Accordingly, the 
present invention is also drawn to a method for making the novel 
copolymers of the present invention. 
DESCRIPTION OF THE PRIOR ART 
Representative prior art dealing with tubular reactors to make copolymers 
are as follows: 
In "Polymerization of ethylene and propylene to amorphous copolymers with 
catalysts of vanadium oxychloride and alkyl aluminum halides"; E. 
Junghanns, A. Gumboldt and G. Bier; Makromol. Chem., v. 58 (12/12/62): 
18-42, the use of a tubular reactor to produce ethylene-propylene 
copolymer is disclosed in which the composition varies along the chain 
length. More specifically, this reference discloses the production in a 
tubular reactor of amorphous ethylene-propylene copolymers using Ziegler 
catalysts prepared from vanadium compound and aluminum alkyl. It is 
disclosed that at the beginning of the tube ethylene is preferentially 
polymerized, and if no additional make-up of the monomer mixture is made 
during the polymerization the concentration of monomers changes in favor 
of propylene along the tube. It is further disclosed that since these 
changes in concentrations take place during chain propagation, copolymer 
chains are produced which contain more ethylene on one end than at the 
other end. It is also disclosed that copolymers made in a tube are 
chemically non-uniform, but fairly uniform as regards molecular weight 
distribution. Using the data reported in their FIG. 17 for copolymer 
prepared in the tube, it was estimated that the M.sub. w /M.sub.n ratio 
for this copolymer was 1.6, and from their FIG. 18 that the intermolecular 
compositional dispersity (Inter-CD, explained in detail below) of this 
copolymer was greater than 15%. 
"Laminar Flow Polymerization of EPDM Polymer"; J. F. Wehner; ACS Symposium 
Series 65 (1978); pp 140-152 discloses the results of computer simulation 
work undertaken to determine the effect of tubular reactor solution 
polymerization with Ziegler catalysts on the molecular weight, 
distribution of the polymer product. The specific polymer simulated was an 
elastomeric terpolymer of ethylene-propylene-1,4-hexadiene. On page 149, 
it is stated that since the monomers have different reactivities, a 
polymer of varying composition is obtained as the monomers are depleted. 
However, whether the composition varies inter-or intramolecularly is not 
distinguished. In Table III on page 148, various polymers having M.sub.w 
/M.sub.n of about 1.3 are predicted. In the third paragraph on page 144, 
it is stated that as the tube diameter increases, the polymer molecular 
weight is too low to be of practical interest, and it is predicted that 
the reactor will plug. It is implied in the first paragraph on page 149 
that the compositional dispersity produced in a tube would be detrimental 
to product quality. 
U.S. Pat. No. 3,681,306 to Wehner is drawn to a process for producing 
ethylene/higher alpha-olefin copolymers having good processability, by 
polymerization in at least two consecutive reactor stages. According to 
this reference, this two-stage process provides a simple polymerization 
process that permits tailor-making ethylene/alpha-olefin copolymers having 
predetermined properties, particularly those contributing to 
processability in commercial applications such as cold-flow, high green 
strength and millability. According to this reference, the inventive 
process is particularly adapted for producing elastomeric copolymers, such 
as ethylene/propylene/5-ethylidene-2-norbornene, using any of the 
coordination catalysts useful for making EPDM. The preferred process uses 
one tubular reactor followed by one pot reactor. However, it is also 
disclosed that one tubular reactor could be used, but operated at 
different reaction donditions to simulate two stages. As is seen from 
column 2, lines 14-20, the inventive process makes polymers of broader MWD 
than those made in a single stage reactor. Although intermediate polymer 
from the first (pipeline) reactor is disclosed as having a ratio of 
M.sub.w /M.sub.n of about 2, as disclosed in column 5, lines 54-57, the 
final polymers produced by the inventive process have an M.sub.w /M.sub.n 
of 2.4 to 5. 
U.S. Pat. No. 3,625,658 to Closon discloses a closed circuit tubular 
reactor apparatus with high recirculation rates of the reactants which can 
be used to make elastomers of ethylene and propylene. With particular 
reference to FIG. 1, a hinged support 10 for vertical leg 1 of the reactor 
allows for horizontal expansion of the bottom leg thereof and prevents 
harmful deformations due to thermal expansions, particularly those 
experienced during reactor clean out. 
U.S. Pat. No. 4,065,520 to Bailey et al discloses the use of a batch 
reactor to make ethylene copolymers, including elastomers, having borad 
compositional distributions. Several feed tanks for the reactor are 
arranged in series, with the feed to each being varied to make the 
polymer. The products made have crystalline to semi-crystalline to 
amorphous regions and gradient changes in between. The catalyst system can 
use vanadium compounds alone or in combination with titanium compound and 
is exemplified by vanadium oxy-trichloride and diisobutyl aluminum 
chloride. In all examples titanium compounds are used. In several examples 
hydrogen and diethyl zinc, known transfer agents, are used. The polymer 
chains produced have a compositionally disperse first length and uniform 
second length. Subsequent lengths have various other compositional 
distributions. 
In "Estimation of Long-Chain Branching in Ethylene-Propylene Terpolymers 
from Infinite-Dilution Viscoelastic properties", Y. Mitsuda, J. Schrag, 
and J. Ferry; J. Appl. Pol. Sci., 18, 193 (1974) narrow MWD copolymers of 
ethylenepropylene are disclosed. For example, in TABLE II on page 198, 
EPDM copolymers are disclosed which have M.sub.w /M.sub.n of from 1.19 to 
1.32. 
In "The Effect of Molecular Weight and Molecular Weight distribution on the 
Non-Newtonian Behavior of Ethylene-Propylene-Diene Polymers; Trans. Soc. 
Rheol., 14, 83 (1970); C. K. Shih, a whole series of compositionally 
homogeneous fractions were prepared and disclosed. For example, the data 
in TABLE I discloses polymer Sample B having a high degree of homogeneity. 
Also, based on the reported data, the MWD of the sample is very narrow. 
However, the polymers are not disclosed as having intramolecular 
dispersity. 
Molecular weight distribution (MWD) is a very important characteristic of 
ethylene-propylene copolymers and terpolymers. Favorable distributions 
result in polymers which can have both faster cures and better processing 
characteristics. An optimum combination of these properties is achieved 
where the polymers have a bimodal molecular weight distribution and a 
bimodal compositional distribution. 
A significant amount of effort has been expended by the polymer industry in 
an attempt to produce such bimodal ethylene-propylene polymers. Generally, 
these efforts have been directed toward physical blends of polymers having 
different MWD or by sequential polymerization in a multiple reactor 
system. For example, a polymerization is carried out in a first reaction 
stage to produce a polymer of a particular MWD and composition with a 
subsequent polymerization in a second reactor stage to produce a polymer 
of a different MWD from that of the first stage and, if desired, of a 
different monomer composition. Representative prior art dealing with the 
preparation of bimodal MWD ethylene-propylene copolymers are as follows: 
British Pat. No. 1,233,599 is illustrative of this two stage polymerization 
process. While copolymers of ethylene are disclosed, the examples and 
disclosure are directed toward polyethylene homopolymers and crystalline 
copolymers, e.g. , 95% ethylene. The preferred catalysts are vanadium 
compounds such as vanadyl halide, vanadium tetrachloride or vanadium 
tris-(acetyl-acetibate) in conjunction with an aluminum compound, e.g., 
Br.sub.2 AlCH.sub.2 Br.sub.2. The different MWDs are obtained by using 
differing amounts of hydrogen in the first and second stage 
polymerization. 
U.S. Pat. No. 4,078,131 discloses an ethylene-propylene rubber composition 
having a bimodal distribution in molecular weights comprising two polymer 
fractions each having a wide distribution of molecular weights and a 
monomer composition different from that of the other principal fractions. 
The polymers are further characterized in that they are formed of: (a) a 
first principal fraction comprising from about 30% to about 85% (by weight 
referred to the total weight of elastomers) of molecular weight fractions 
having an intrinsic viscosity distribution of from about 0.2 to about 3, 
and average intrinsic viscosity between about 0.8 to about 1.5, an average 
propylene content between about 36 to about 52% by weight, and a 
termonomer content of between 0% and about 5%, and of (b) a second 
fraction comprising about 70% to about 15% of weight of molecular weight 
fractions having an intrinsic viscosity distribution from about 3 to about 
15, an average intrinsic viscosity of about 3.5 to about 7, and average 
propylene content of between about 26% to about 32% by weight and a 
termonomer content of about 0 to about 5%. 
The polymers are prepared by carrying out polymerization in two separate 
reactors connected in series. The catalyst systems utilized include 
organic and inorganic component of a transition metal of Group 4A to 8A of 
the Mendeleev periodic table of the elements, e.g., VOCl.sub.3, VCl.sub.4, 
vanadium esters and acetyl acetonates. Co-catalysts include organoaluminum 
compounds or mixtures of compounds, e.g., aluminum alkyls. 
U.S. Pat. No. 3,681,306 discloses a two stage polymerization process for 
the preparation ethylene-propylene co-and terpolymers. In one embodiment 
the first stage is a "pipe reactor" and the second stage is a back-mixed 
pot reactor. The polymerization is carried out so that the average 
ethylene/alpha olefin ratio in one stage is at least 1.3 times the average 
ratio of the other stage. Any of the coordination catalysts known to be 
useful in producing EPDM polymers is said to be effective for the process. 
U.S. Pat. No. 4,259,468 discloses a broad molecular weight 
ethylene-propylene-diene rubber prepared using as a catalyst (a) the 
alcohol reaction product of vanadium oxytrichloride and (b) a mixture of 
aluminum sesquichloride and ethylaluminum dichloride. The polymer is 
characterized in that the higher molecular weight fraction contains a 
larger proportion of the diene than does the lower molecular weight 
fraction. The polymer has an intrinsic viscosity of about 1.0 to about 6.0 
dl/g and a weight average molecular weight/number ratio of about 3 to 
about 15. 
U.S. Pat. No. 4,306,041 discloses a method of manufacture of EPDM type 
terpolymers which utilizes a two stage polymerization process. 
Substantially all of the non-conjugated diene monomer is fed to the first 
stage thereby producing a polymer having a non-uniform diene content. 
It has been shown that selecting the appropriate support for titanium based 
Ziegler catalysts can result in the single stage polymerization of 
ethylene propylene polymer have a broad molecular weight distribution, 
e.g., TiCl.sub.4 supported on aluminosilicate; see A.G. Rodinov, et al., 
Vysokomal, soyed A23: No. 7, 1560-1567, 1981. 
A 1962 study alleges that soluble Ziewgler catalysts tend to give EP 
polymers having uniform monomer distribution as a function of molecular 
weight. Heterogeneous TiCl.sub.4 -AlEt.sub.3, on the other hand, gives a 
broad distribution. See G. W. Philips and W. L. Carrick, "Transition Metal 
Catalysts, IX. Random Ethylene-Propylene Copolymers with Low Pressure 
Polymerization Catalysts,-" J. Am. Chem. Soc., 84, 920-925, 1962. 
In the polymerization of ethylene-propylene polymers it has been 
demonstrated that different catalysts give different EP reactivity ratios. 
See G. Natta, G. Crespi, A. Valvassori, G. Sartori, Rubber Chemistry and 
Technology, 36 1608 (1963). 
C. Cozewith and G. Ver Strate, Macromolecules, 4, 482 (1971). Cozewith and 
Ver Strate have determined the reactivity ratios R.sub.ethylene and 
R.sub.propylene for the system VOCl.sub.3 /EASC to be 10.1 and 0.025 
respectively. A co-worker in an unpublished memorandum disclosed that the 
R.sub.ET and RP.sub.r for VCl.sub.4 /EASC was found to be 3.91 and 0.224 
respectively.

DETAILED DESCRIPTION OF THE INVENTION 
As already noted above, the present invention is drawn to novel copolymer 
of ethylene and at least one other alpha-olefin monomer, which copolymer 
is a superposition of two or more copolymers, each of which is 
intramolecularly homogeneous and has an MWD characterized by at least one 
of M.sub.w /M.sub.n of less than 2 and M.sub.z /Mphd w of less than 1.8. 
More specifically, the individual component copolymers in accordance with 
the present invention comprises intramolecularly heterogeneous chains 
wherein at least two portions of an individual intramolecularly 
heterogeneous chain, each portion comprising at least 5 wt % of the chain, 
differ in composition from one another by at least 5 wt % ethylene, 
wherein the intermolecular compositional dispersity of the polymer is such 
at 95 wt % of the polymer chains have a composition 15% or less different 
in ethylene from the average weight percent ethylene composition, and 
wherein the copolymer is characterized by at least one of a ration of 
M.sub.w /MHD n of less than 2 and a ratio of M.sub. z /M.sub.w of less 
than 1.8. 
Since the present invention is considered to be most preferred in the 
context of ethylene-propylene (EPM) or ethylene-propylene-diene (EPDM) 
copolymers, it will be described in detail in the context of EPM and/or 
EPDM. 
Copolymer in accordance with the present invention is preferably made in a 
tubular reactor. When produced in a tubular reactor with monomer feed only 
at the tube inlet, it is known that at the beginning of the tubular 
reactor ethylene, due to its high reactivity, will be preferentially 
polymerized. However, the concentration of monomers changes along the tube 
in favor of propylene as the ethylene is depleted. The result is component 
copolymer chains which are higher in ethylene concentration in the chain 
segments grown near the reactor inlet (as defined at the point at which 
the polymerization reaction commences), and higher in propylene 
concentration in the chain segments formed near the reactor outlet. An 
illustrative copolymer chain of ethylene-propylene is schematically 
presented below with E representing ethylene constituents and P 
representing propylene constituents in the chain: 
##STR1## 
As can be seen from this illustrative schematic chain, the far left-hand 
segment (1) thereof represents that portion of the chain formed at the 
reactor inlet where the reaction mixture is proportionately richer in the 
more reactive constituent ethylene. This segment comprises four ethylene 
molecules and one propylene molecule. However, as subsequent segments are 
formed from left to right with themore reactive ethylene being depleted 
and the reaction mixture proportionately increasing in propylene 
concentration, the subsequent chain segments become more concentrated in 
propylene. The resulting chain is intramolecularly heterogeneous. 
In the event that more than two monomers are used, e.g., in the production 
of EPDM using a diene termonomer, for purposes of describing the present 
invention all properties related to homogeneity and heterogeneity will 
refer to the relative ratio of ethylene to the other monomers in the 
chain. The property, of the copolymer discussed herein, related to 
intramolecular compositional dispersity (compositional variation within a 
chain) shall be referred to as Intras-CD, and that related to 
intermolecular compositional disperisty (compositional variation between 
chains) shall be referred to as Inter-CD. 
For copolymers in accordance with the present invention, composition can 
vary between chains as well as along the length of the chain. The Inter-CD 
can be characterized by the difference in composition between some 
fraction of the copolymer and the average composition, as well as by the 
total difference in composition between the copolymer fractions containing 
the highest and lowest quantity of ethylene. Techniques for measuring the 
breadth of the Intra-CD are known as illustrated by Junghanns, et al., 
wherein a p-xylene-dimethylformamide solvent/non-solvent was used to 
fractionate copolymer into fractions of differing intermolecular 
composition. Other solvent/non-solvent systems can be used, such as 
hexane-2-propanol, as will be discussed in more detail below. 
The Inter-CD of the individual component copolymers in accordance with the 
present invention is such that 95 wt % of the copolymer chains have an 
ethylene composition that differs from the average component weight 
percent ethylene composition by 15 wt % or less. The preferred Inter-CD is 
about 13% or less, with the most preferred being about 10% or less. In 
comparison, Junghanns, et al., found that their tubular reactor copolymer 
had an Inter-CD of greater than 15 wt %. 
Broadly, the Intra-CD of copolymer in accordance with the present invention 
is such that at least two portions of an individual component 
intramolecularly heterogeneous chain, each portion comprising at least 5 
wt % of the chain, differ in composition from one another by at least 5 wt 
% ethylene. Unless otherwise indicated, this property of Intra-CD as 
referred to herein is based upon at least two 5 wt % portions of copolymer 
chain. The Intra-CD of copolymer in accordance with the present invention 
can be such that at least two portions of copolymer chain differ by at 
least 10 wt % ethylene. Differences of at least 20 wt %, as well as of at 
least 40 wt % ethylene are also considered to be in accordance with the 
present invention. 
The experimental procedure for determining Intra-CD is as follows. First, 
the Inter-CD is established as described below, then the polymer chain is 
broken into fragments along its contour and the Inter-CD of the fragments 
is determined. The difference in the two results is due to Intra-CD as can 
be seen in the illustrative example below. 
Consider a heterogeneous sample polymer containing 30 monomer units. It 
consists of 3 molecules designated A, B, C. 
##STR2## 
Molecule A is 36.8 wt % ethylene, B is 46.6%, and C is 50% ethylene. The 
average ethylene content for the mixture is 44.3%. For this sample the 
Inter-CD is such that the highest ethylene polymer contains 5.7% more 
ethylene than the average while the lowest ethylene content polymer 
contains 7.5% less ethylene than the average. Or, in other words, 100 wt % 
of the polymer is within +5.7% and -7.5% ethylene about an average of 
44.3%. Accordingly, the Inter-CD is 7.5% when the given wt % of the 
polymer is 100%. The distribution may be represented graphically as by 
curve l in FIG. 3. 
If the chains are broken into fragments, there will be a new Inter-CD. For 
simplicity, consider first breaking only molecule A into fragments shown 
by the slashes as follows: 
EQU EEEEP/EEEPE/EEPPE/EPPEP/PPEPP/PPPPP 
Portions of 72.7%, 72.7%, 50%, 30.8%, 14.3% and 0% ethylene are obtained. 
If molecules B and C are similarly broken and the weight fractions of 
similar composition are grouped the new Inter-CD shown by curve 2 in FIG. 
3 is obtained. The difference between the two curves in the figure is due 
to Intra-CD. 
Consideration of such data, especially near the end point ranges, 
demonstrates that for this sample at least 5% of the chain contour 
represented by the cumulative weight % range (a) differs in composition 
from another section by at least 15% ethylene shown as (b), the difference 
between the two curves. The difference in composition represented by (b) 
cannot be intermolecular. If it were, the separation process for the 
original polymer would have revealed the higher ethylene contents seen 
only for the degraded chain. 
The compositional differences shown by (b) and (d) in the figure between 
original and fragmented chains give minimum values for Intra-CD. The 
Intra-CD must be at least that great, for chain sections have been 
isolated which are the given difference in composition (b) or (d) from the 
highest or lowest composition polymer isolated from the original. We know 
in this example that the original polymer represented at (b) had sections 
of 72.7% ethylene and 0% ethylene in the same chain. It is highly likely 
that due to the inefficiency of the fractionation process any real polymer 
with Intra-CD examined will have sections of lower or higher ethylene 
connected along its contour than that shown by the end points of the 
fractionation of the original polymer. Thus, this procedure determines a 
lower bound for Intra-CD. To enhance the detection, the original whole 
polymer can be fractionated (e.g., separate molecule A from molecule B 
from molecule C in the hypothetical example) with these fractions 
refractionated until they show no (or less) Inter-CD. Subsequent 
fragmentation of this inter-molecularly homogeneous fraction now reveals 
the total Intra-CD. In principle, for the example, if molecule A were 
isolated, fragmented, fractionated and analyzed, the Intra-CD for the 
chain sections would be 72.7-0%=72.7% rather than 72.7-50%=22.7% seen by 
fractionating the whole mixture of molecules A, B and C. 
In order to determine the fraction of a polymer which is intramolecularly 
heterogeneous in a mixture of polymers combined from several sources or as 
several modes in the case described here, the mixture must be separated 
into fractions which show no further heterogenity upon subsequent 
fractionation. These fractions are subsequently fractured and fractionated 
to reveal which are heterogeneous. 
The fragments into which the original polymer is broken should be large 
enough to avoid end effects and to give a reasonable opportunity for the 
normal statistical distribution of segments to form over a given monomer 
conversion range in the polymerization. Intervals of ca 5 wt % of the 
polymer are convenient. For example, at an average polymer molecular 
weight of about 10.sup.5, fragments of ca 5000 molecular weight are 
appropriate. A detailed mathematical analysis of plug flow or batch 
polymerization indicates that the rate of change of composition along the 
polymer chain contour will be most severe at high ethylene conversions 
near the end of the polymerization. The shortest fragments are needed here 
to show the low propylene content sections. 
The best available technique for determination of compositional dispersity 
for non-polar polymers is solvent/non-solvent fractionation which is based 
on the thermodynamics of phase separation. This technique is described in 
"Polymer Fractionation," M. Cantow editor, Academic 1967, p. 341 ff and in 
H. Inagaki, T. Tanaku, Developments in Polymer Characterization, 3, 1 
(1982). These are incorporated herein by reference. 
For non-crystalline copolymers of ethylene and propylene, molecular weight 
governs insolubility more than does composition in a solvent/non-solvent 
solution. High molecular weight polymer is less soluble in a given solvent 
mix. Also, there is a systematic correlation of molecular weight with 
ethylene content for the polymers described herein. Since ethylene 
polymerizes much more rapidly than propylene, high ethylene polymer also 
tends to be high in molecular weight. Additionally, chains rich in 
ethylene tend to be less soluble in hydrocarbon/polar non-solvent mixtures 
than propylene-rich chains. Thus the high molecular weight, high ethylene 
chains are easily separated on the basis of thermodynamics. 
A fractionation procedure is as follows: Unfragmented polymer is dissolved 
in n-hexane at 23.degree. C. to form ca a 1% solution (1 g polymer/100 cc 
hexane). Isopropyl alcohol is titrated into the solution until turbidity 
appears at which time the precipitate is allowed to settle. The 
supernatant liquid is removed and the precipitate is dried by pressing 
between Mylar.RTM. (polyethylene terphthalate) film at 150.degree. C. 
Ethylene content is determined by ASTM method D-3900. Titration is resumed 
and subsequent fractions are recovered and analyzed until 100% of the 
polymer is collected. The titrations are ideally controlled to produce 
fractions of 5-10% by weight of the original polymer especially at the 
extremes of composition. 
To demonstrate the breadth of the distribution, the data are plotted as % 
ethylene versus the cumulative weight of polymer as defined by the sum of 
half the weight % of the fraction of that composition plus the total 
weight % of the previously collected fractions. 
Another portion of the original polymer is broken into fragments. A 
suitable method for doing this is by thermal degradation according to the 
following procedure: In a sealed container in a nitrogen-purged oven, a 2 
mm thick layer of the polymer is heated for 60 minutes at 330.degree. C. 
This should be adequate to reduce a 10.sup.5 molecular weight polymer to 
fragments of ca 5000 molecular weight. Such degradation does not change 
the average ethylene content of the polymer. This polymer is fractionated 
by the same procedure as the high molecular weight precursor. Ethylene 
content is measured, as well as molecular weight on selected fractions. 
Ethylene content is measured by ASTM-D3900 for ethylene-propylene 
copolymers between 35 and 85 wt. % ethylene. Above 85% ASTM-D2238 can be 
used to obtain methyl group concentrations which are related to percent 
ethylene in an unambiguous manner for ethylene-propylene copolymers. When 
comonomers other than propylene are employed no ASTM tests covering a wide 
range of ethylen contents are available, however, proton and carbon 13 
nuclear magnetic reasonance can be employed to determine the composition 
of such polymers. These are absolute techniques requiring no calibration 
when operated such that all nucleii contribute equally to the spectra. For 
ranges not covered by the ASTM tests for ethylene-propylene copolymers, 
these nuclear magnetic resonance methods can also be used. 
Molecular weight and molecular weight distribution are measured using a 
Waters 150 gel permeation chromatograph equipped with a Chromatix KMX-6 
on-line light scattering photometer. The system is used at 135.degree. C. 
with 1,2,4 trichlorobenzene as mobile phase. Showdex (Showa-Denko America, 
Inc.) polystyrene gel columns 802, 803, 804 and 805 are used. This 
technique is discussed in "Liquid Chromatography of Polymers and Related 
Materials III", J. Cazes editor. Marcel Dekkar, 1981, p. 207 (incorporated 
herein by reference). No corrections for column spreading are employed; 
however, data on generally accepted standards, e.g., National Bureau of 
Standards Polyethene 1484 and anionically produced hydrogenated 
polyisoprenes (an alternating ethylenepropylene copolymer) demonstrate 
that such corrections on M.sub.w /M.sub.n or M.sub.z /M.sub.w are less 
than 0.05 unit. M.sub.w /M.sub.n is calculated from an elution 
time-molecular weight relationship whereas M.sub.z /M.sub.w is evaluated 
using the light scattering photometer. The numerical analyses can be 
performed using the commercially available computer software GPC2, MOLWT 2 
available from LDC/Milton Roy-Riviera Beach, Fla. 
As already noted, copolymers in accordance with the present invention are 
comprised of ethylene and at least one other alpha-olefin. It is believed 
that such alpha-olefins could include those containing 3 to 18 carbon 
atoms, e.g., propylene, butene-1, pentene-1, etc. Alpha-olefins of 3 to 6 
carbons are preferred due to economic considerations. The most preferred 
copolymers in accordance with the present invention are those comprised of 
ethylene and propylene or ethylene, propylene and diene. 
As is well known to those skilled in the art, copolymers of ethylene and 
higher alpha-olefins such as propylene often include other polymerizable 
monomers. Typical of these other monomers may be non-conjugated dienes 
such as the following non-limiting examples: 
a. straight chain acyclic dienes such as: 1,4-hexaidne; 1,6-octadiene; 
b. branched chain acyclic dienes such as: 5-methyl-1, 4-hexadiene; 
3,7-dimethyl-1,6-octadiene; 3,7-dimethyl-1,7-octadiene and the mixed 
isomers of dihydro-myrcene and dihydroocinene; 
c. single ring alicyclic dienes such as: 1,4-cyclohexadiene; 
1,5-cyclooctadiene; and 1,5-cyclododecadiene; 
d. multi-ring alicyclic fused and bridged ring dienes such as: 
tetrahydroindene; methyltetrahydroindene; dicyclopentadiene; 
bicyclo-(2,2,1)-hepta-2,5-diene; alkenyl, alkylidene, cycloalkenyl and 
cycloalkylidene norbornenes such as 5-methylene-2-norbornene (MNB), 
5-ethylidene-2-norbornene (ENB), 5-(4-cyclopentenyl)-2-norbornene; 
5-cyclohexylidene-2-norbornene. 
Of the non-conjugated dienes typically used to prepare these copolymers, 
dienes containing at least one of the double bonds in a strained ring are 
preferred. The most preferred diene is 5-ethylidene-2-norbornene (ENB). 
The amount of diene (wt. basis) in the copolymer could be from about 0% to 
20% with 0% to 15% being preferred. The most preferred range is 0% to 10%. 
As already noted, the most preferred copolymer in accordance with the 
present invention is ethylene-propylene or ethylene-propylene-diene. In 
either event, the average ethylene content of the copolymer could be as 
low as about 10% on a weight basis. The preferred minimum is about 25%. A 
more preferred minimum is about 30%. The maximum ethylene content could be 
about 90% on a weight basis. The preferred maximum is about 85%, with the 
most preferred being about 80%. 
The molecular weight of copolymer made in accordance with the present 
invention can vary over a wide range. It is believed that the weight 
average molecular weight could be as low as about 2,000. The preferred 
minimum is about 10,000. The most preferred minimum is about 20,000. It is 
believed that the maximum weight average molecular weight could be as high 
as about 12,000,000. The preferred maximum is about 1,000,000. The most 
preferred maximum is about 750,000. 
Another feature of copolymer made in accordance with the present invention 
is that the molecular weight distribution (MWD) of each component is very 
narrow, as characterized by at least one of a ratio of M.sub.w /M.sub.n of 
less than 2 and a ratio of M.sub.z /M.sub.w of less than 1.8. As relates 
to EPM and EPDM, a typical advantage of such copolymers composed of 
several modes having narrow MWD is that when compounded and vulcanized, 
faster cure and better physical properties result than when copolymers 
having lower M.sub.n for a given Mooney are used. 
Processes in accordance with the present invention produce copolymer by 
polymerization of a reaction mixture comprised of catalyst, ethylene and 
at least one additional alpha-olefin monomer. Solution polymerizations are 
preferred. 
Any known solvent for the reaction mixture that is effective for the 
purpose can be used in conducting solution polymerizations in accordance 
with the present invention. For example, suitable solvents would be 
hydrocarbon solvents such as aliphatic, cycloaliphatic and aromatic 
hydrocarbon solvents, or halogenated versions of such solvents. The 
preferred solvents are C.sub.12 or lower, straight chain or branched 
chain, saturated hydrocarbons, C.sub.5 to C.sub.9 saturated alicyclic or 
aromatic hydrocarbons or C.sub.2 to C.sub.6 halogenated hydrocarbons. Most 
preferred are C.sub.12 or lower, straight chain or branched chain 
hydrocarbons, particularly hexane. Non-limiting illustrative examples of 
solvents are butane, pentane, hexane, heptane, cyclopentane, cyclohexane, 
cycloheptane, methyl cyclopentane, methyl cyclohexane, isooctane, benzene, 
touene, xylene, chloroform, chlorobenzenes, tetrachloroethylene, 
dichloroethane and trichloroethane. 
These processes may be carried out in a mixfree reactor system, which is 
one in which substantially no mixing occurs between portions of the 
reaction mixture that contain polymer chains initiated at different times. 
To produce the polymodal MWD polymers of this invention, the product is 
removed at one or more locations. Alternately, two or more catalysts with 
different propagation rates are used. Suitable reactors are a continuous 
flow tubular or a stirred batch reactor. A tubular reactor is well known 
and is designed to minimize mixing of the reactants in the direction of 
flow. As a result, reactant concentration will vary along the reactor 
length. In contrast, the reaction mixture in a continuous flow stirred 
tank reactor (CFSTR) is blended with the incoming feed to produce a 
solution of essentially uniform composition everywhere in the reactor. 
Consequently, the growing chains in a portion of the reaction mixture will 
have a variety of ages and thus a single CFSTR is not suitable for the 
process of this invention. However, it is well known that 3 or more 
stirred tanks in series with all of the catalyst fed to the first reactor 
can approximate the performance of a tubular reactor. Accordingly, such 
tanks in series are considered to be in accordance with the present 
invention. Alternately, a reactor in which limited discrete mixing is 
permitted may be used. In this case, several catalyst feeds are used, each 
comprising appropriately premixed components. The reactor is not truly mix 
free. However, mixing of chains which are initiated at different times is 
permitted only in a manner that discrete narrow MWD modes are produced. 
The term "limited discrete mix free reactor" as used in the specification 
and claims means a reactor which permits the aforedescribed limited 
discrete mixing. 
The term "essentially mix free reactor" as used in the specification and 
claims means both mix free and limited discrete mix free reactors. 
A batch reactor is a suitable vessel, preferably equipped with adequate 
agitation, to which the catalyst, solvent, and monomer are added at the 
start of the polymerization. The charge of reactants is then left to 
polymerize for a time long enough to produce the desired product. For 
economic reasons, a tubular reactor is preferred to a batch reactor for 
carrying out the processes of this invention. 
In addition to the importance of the reactor system to make copolymers in 
accordance with the present invention, the polymerization should be 
conduced such that for each component or mode in the MWD: 
a. the catalyst system produces essentially one active catalyst species, 
b. the reaction mixture is essentially free of chain transfer agents, and 
c. the polymer chains for each mode are essentially all initiated 
simultaneously, which is at the same time for a batch reactor or at the 
same point along the length of the tube 
for a tubular reactor. 
The desired polymer can be obtained if additional solvent and reactants 
(e.g., at least one of the ethylene, alpha-olefin and diene) are added 
either along the length of a tubular reactor or during the course of 
polymerization in a batch reactor. Operating in this fashion may be 
desirable in certain circumstances to control the polymerization rate or 
polymer composition. However, it is necessary to add the catalyst at the 
inlet or specific locations of the tube or at the onset of or at specific 
times in batch reactor operation to meet the requirement that essentially 
all polymer chains are initiated simultaneously. 
Accordingly, in on aspect of this invention, processes in accordance with 
the present invention are carried out: 
(a) in a least one mix free reactor or limited discrete mixing reactor, 
(b) using catalyst systems that produce essentially one active catalyst 
species each, 
(c) using at least one reaction mixture which is essentially transfer 
agent-free, and 
(d) in such a manner and under conditions sufficient to initiate 
propagation of essentially all polymer chains of each discrete mode 
simultaneously. 
(e) with drawing polymer fractions from the reactor after varying degrees 
of polymerization have been allowed to occur the effect of which is to 
cause the polymer to be composed of a blend of narrow MWD molecular 
weight. 
By quenching polymerization after removal from the reactor and blending the 
polymer fractions a polymodal ethylene-propylene copolymer is produced, 
each fraction comprising copolymer chains with compositions which are 
intramolecularly heterogeneous and intermolecularly homogeneous. 
In another embodiment of the invention steps (a) through (d) above are 
followed except that more than one catalyst species is utilized. The 
catalyst species are characterized by the fact that they do not interact 
with one another, and initiate polymer species of narrow MWD, but of 
different molecular weights. A preferred mixed catalyst system comprises 
VCl.sub.4 /VOCl.sub.3 utilizing as a cocatalyst an alkyl aluminum 
sesquihalide. The catalyst system can be lewis base moderated. The 
resultant polymer is a bimodal MWD polymer. 
Since the tubular reactor is the preferred reactor system for carrying out 
processes in accordance with the present invention, the following 
illustrative descriptions and examples are drawn to that system, but will 
apply to other reactor systems as will readily occur to the artisan having 
the benefit of the present disclosure. 
In practicing processes in accordance with the present invention, use is 
preferably made of at least one tubular reactor. Thus, in its simplest 
form, such a process would make use of but a single reactor. However, as 
would readily occur to the artisan having the benefit of the present 
disclosure, more than one reactor could be used, either in parallel for 
economic reasons, or in series with multiple monomer feed to vary 
intramolecular composition. 
For example, various structures can be prepared by adding additional 
monomer(s) during the course of the polymerization, as shown in FIG. 4, 
wherein composition is plotted versus position along the contour length of 
the chain. The Intra-CD of cure 1 is obtained by feeding all of the 
monomers at the tubular reactor inlet or at the start of a batch reaction. 
In comparison, the Intra-CD of curve 2 can be made by adding additional 
ethylene at a point along the tube or, in a batch reactor, where the 
chains have reached about half their length. The Intra-CD's of Curve 3 
requires multiple feed additions. The Intra-CD of curve 4 can be formed if 
additional comonomer rather than ethylene is added. This structure permits 
a whole ethylene composition range to be omitted from the chain. In each 
case, a third or more comonomers may be added. 
The composition of the catalyst used to produce alpha-olefin copolymers has 
a profound effect on copolymer product properties such as compositional 
dispersity and MWD. The catalyst utilized in practicing processes in 
accodance with the present invention should be such as to yield 
essentially one active catalyst species in the reaction mixture. More 
specifically, it should yield a controlled number of species, each of 
which must be capable of simultaneous initiation. Additional active 
catalyst species could be present, provided the copolymer product is in 
accordance with the present invention, e.g., a superposition of components 
of narrow MWD. The extent to which a catalyst species contributes to the 
polymerization can be readily determined using the below-described 
techniques for characterizing catalyst according to the number of active 
catalyst species. 
Techniques for characterizing catalyst according to the number of active 
catalyst species are within the skill of the art, as evidenced by an 
article entitled "Ethylene-Propylene Copolymers. Reactivity rations, 
Evaluation and Significance," C. Cozewith and G. Ver Strate, 
Macromolecules, 4, 482 (1971), which is incorporated herein by reference. 
It is disclosed by the authors that copolymers made in a continuous flow 
stirred reactor should have an MWD characterized by M.sub.w /M.sub.n =2 
and a narrow Inter-CD when one active catalyst species is present. By a 
combination of fractionation and gel permeation chromatography (GPC) it is 
shown that for single active species catalysts the compositions of the 
fractions vary no more than .+-.3% about the average and the MWD (weight 
to number average ratio) for these samples approaches two (2). It is this 
latter characteristic (M.sub.w /M.sub.n of about 2) that is deemed the 
more important in identifying a single active catalyst species. On the 
other hand, other catalysts gave copolymer with an Inter-CD greater than 
.+-.10% about the average and multi-modal MWD often with M.sub.w /M.sub.n 
greater than 10. These other catalysts are deemed to have more than one 
active species. 
Catalyst systems to be used in carrying out processes in accordance with 
the present invention may be Ziegler catalysts, which may typically 
include: 
(a) a compound of a transition metal, i.e., a metal of Groups I-B, III-B, 
IVB, VB, VIB, VIIB and VIII of the Periodic Table, and (b) an organometal 
compound of a metal of Groups I-A, II-A, II-B and III-A of the Periodic 
Table. 
The preferred catalyst system in practicing processes in accordance with 
the present invention comprises hydrocarbon-soluble vanadium compound in 
which the vanadium valence is 3 to 5 and organo-aluminum compound, with 
the proviso that the catalyst system yields essentially one active 
catalyst species as described above. At least one of the vanadium 
compound/organoaluminum pair selected must also contain a valence-bonded 
halogen. 
In terms of formulas, vanadium compounds useful in practicing processes in 
accordance with the present invention could be: 
##STR3## 
where x=0-3 and R=a hydrocarbon radical; 
EQU VCl.sub.4 ; 
VO(AcAc).sub.2, 
where AcAc=acetyl acetonate; 
EQU V(AcAc).sub.3 ; 
EQU VOCl.sub.x (AcAc).sub. 3-x, 
where x=1 or 2; and 
EQU VCl.sub.3.nB, 
Where n=2-3 and B=lewis base capable of making hydrocarbon-soluble 
complexes with VCl.sub.3, such as tetrahydrofuran, 
2-methyl-tetrahydrofuran and dimethyl pyridine. 
In formula 1 above, R preferably represents a C.sub.1 to C.sub.10 
aliphatic, alicyclic or aromatic hydrocarbon radical such as ethyl (Et), 
phenyl, isopropyl, butyl, propyl, n-butyl, i-butyl, t-butyl, hexyl, 
cyclohexyl, octyl, napthyl, etc. Non-limiting, illustrative examples of 
formula (1) and (2) compounds are vanadyl trihalides, alkoxy halides and 
alkoxides such as VOCl.sub.3, VOCl.sub.2 (OBu) where Bu =butyl, and 
VO(OC.sub.2 H.sub.5).sub. 3. The most preferred vanadium compounds are 
VCl.sub.4, VOCl.sub.3, and VOCl.sub.2 (OR). 
As already noted, the co-catalyst is preferably organo-aluminum compound. 
In terms of chemical formulas, these compounds could be as follows: 
______________________________________ 
AlR.sub.3, Al(OR')R.sub.2 
Al R.sub.2 Cl, R.sub.2 Al--O--AlR.sub.2 
AlR'RCl AlR.sub.2 I 
Al.sub.2 R.sub.3 Cl.sub.3, 
and 
AlRCl.sub.2, 
______________________________________ 
where R and R? represent hydrocarbon radicals, the same or different, as 
described above with respect to the vanadium compound formula. The most 
preferred organoaluminum compound is an aluminum alkyl sesquichloride such 
as Al.sub.2 Et.sub.3 Cl.sub.3 or Al.sub.2 (iBu).sub.3 Cl.sub.3. 
In terms of performance, a catalyst system comprised of VCl.sub.4 and 
Al.sub.2 R.sub.3 Cl.sub.3, preferably where R is ethyl, has been shown to 
be particularly effective. For best catalyst performance, the molar 
amounts of catalyst components added to the reaction mixture should 
provide a molar ratio of aluminum/vanadium (Al/V) of at least about 2. The 
preferred minimum Al/V is about 4. The maximum Al/V is based primarily on 
the considerations of catalyst expense and the desire to minimize the 
amount of chain transfer that may be caused by the organo-aluminum 
compound (as explained in detail below). Since, as is known certain 
organo-aluminum compounds act as chain transfer agents, if too much is 
present in the reaction mixture the M.sub.w /M.sub.n of the copolymer may 
rise above 2. Based on these considerations, the maximum Al/V could be 
about 25, however, a maximum of about 17 is more preferred. The most 
preferred maximum is about 15. 
Chain transfer agents for the Ziegler-catalyzed polymerization of 
alpha-olefins are well known and are illustrated, by way of example, by 
hydrogen or diethyl zinc for the production of EPM and EPDM. Such agents 
are very commonly used to control the molecular weight of EPM and EPDM 
produced in continuous flow stirred reactors. For the essentially single 
active species Ziegler catalyst systems used in accordance with the 
present invention, addition of chain transfer agents to a CFSTR reduces 
the polymer molecular weight but does not effect the molecular weight 
distribution. On the other hand, chain transfer reactions during tubular 
reactor polymerization in accordance with the present invention broaden 
polymer molecular weight distribution and Inter-CD. Thus the presence of 
chain transfer agents in the reaction mixture should be minimized or 
omitted altogether. Although difficult to generalize for all possible 
reactions, the amount of chain transfer agent used should be limited to 
those amounts that provide copolymer product in accordance with the 
desired limits as regards MWD and compositional dispersity. It is believed 
that the maximum amount of chain transfer agent present in the reaction 
mixture could be as high as about 0.2 mol/mol of transition metal, e.g., 
vanadium, again provided that the resulting copolymer product is in 
accordance with the desired limits as regards MWD and compositional 
dispersity. Even in the absence of added chain transfer agent, chain 
transfer reactions can occur because propylene and the organo-aluminum 
cocatalyst can also act as chain transfer agents. In general, among the 
organo-aluminum compounds that in combination with the vanadium compound 
yield just one active species, the organoaluminum compound that gives the 
highest copolymer molecular weight at acceptable catalyst activity should 
be chosen. Furthermore, if the Al/V ratio has an effect on the molecular 
weight of copolymer product, that Al/V should be used which gives the 
highest molecular weight also at acceptable catalyst activity. Chain 
transfer with propylene can best be limited by avoiding excessive 
temperature during the polymerization as described below. 
Molecular weight distribution and Inter-CD are also broadened by catalyst 
deactivation during the course of the polymerization which leads to 
termination of growing chains. It is well known that the vanadiumbased 
Ziegler catalyst used in accordance with the present invention are subject 
to such deactivation reactions which depend to an extent upon the 
composition of the catalyst. Although the relationship between active 
catalyst lifetime and catalyst system composition is not known at present, 
for any given catalyst, deactivation can be reduced by using the shortest 
residence time and lowest temperature in the reactor that will produce the 
desired monomer conversions. 
Polymerizations in accordance with the present invention should be 
conducted in such a manner and under conditions sufficient to initiate 
propagation of essentially all copolymer chains for each particular 
M.sub.w mode simultaneously. This can be accomplished by utilizing the 
process steps and conditions described below. 
The catalyst components are preferably premixed, that is, reacted to form 
active catalyst outside of the reactor, to ensure rapid chain initiation. 
Aging of the premixed catalyst system, that is, the time spent by the 
catalyst components (e.g., vanadium compound and organoaluminum) in each 
other's presence outside of the reactor, should preferably be kept within 
the limits. If not aged for a sufficient period of time, the components 
will not have reacted with each other sufficiently to yield an adequate 
quantity of active catalyst species, with the result of non-simultaneous 
chain initiation. Also, it is known that the activity of the catalyst 
species will decrease with time so that the aging must be kept below a 
maximum limit. It is believed that the minimum aging period, depending on 
such factors as concentration of catalyst components, temperature and 
mixing equipment, could be as low as about 0.1 second. The preferred 
minimum aging period is about 0.5 second, while the most preferred minimum 
aging period is about 1 second. While the maximum aging period could be 
higher, for the preferred vanadium/organo-aluminum catalyst system the 
preferred maximum is about 200 seconds. A more preferred maximum is about 
100 seconds. The most preferred maximum aging period is about 50 seconds. 
The premixing could be performed at low temperature such as 40.degree. C. 
or below. It is preferred that the premixing be performed at 25.degree. C. 
or below, with 15.degree. C. or below being most preferred. 
Where more than one catalyst species is utilized each catalyst and 
cocatalyst should be premixed separately. The several premixed streams of 
catalysts species are then mixed immediately prior to mixing the catalyst 
species with the monomer feed. Alternately, the several pre-mixed catalyst 
feed streams can be fed to the same mixer where they are simultaneously 
blended with a solvent/monomer stream. 
The temperature of the reaction mixture should also be kept with certain 
limits. The temperature at the reactor inlet should be high enough to 
provide complete, rapid chain initiation at the start of the 
polymerization reaction. The length of time the reaction mixture spends at 
high temperature must be short enough to minimize the amount of 
undesirable chain transfer and catalyst deactivation reactions. 
Temperature control of the reaction mixture is complicated somewhat by the 
fact that the polymerization reaction generates large quantities of heat. 
This problem is, preferably, taken care of by using prechilled feed to the 
reactor to absorb the heat of polymerization. With this technique, the 
reactor is operated adiabatically and the temperature is allowed to 
increase during the course of polymerization. As an alternative to feed 
prechill, heat can be removed from the reaction mixture, for example, by a 
heat exchanger surrounding at least a portion of the reactor or by 
well-known autorefrigeration techniques in the case of batch reactors or 
multiple stirred reactors in series. 
An adiabatic reactor operation is used, the inlet temperature of the 
reactor feed could be about from -50.degree.; C. to 50.degree. C. It is 
believed that the outlet temperature of the reaction mixture could be as 
high as about 200.degree. C. The preferred maximum outlet temperature is 
about 70.degree. C. The most preferred maximum is about 50.degree. C. In 
the absence of reactor cooling, such as by a cooling jacket, to remove the 
heat of polymerization, it has been determined that the temperature of the 
reaction mixture will increase from reactor inlet to outlet by about 
13.degree. C. per weight percent of copolymer in the reaction mixture 
(weight of copolymer per weight of solvent). 
Having the benefit of the above disclosure, it would be well within the 
skill of the art to determine the operating temperature conditions for 
making copolymer in accordance with the present invention. For example, 
assume an adiabatic reactor and an outlet temperature of 35.degree. C. are 
desired for a reaction mixture containing 5% copolymer. The reaction 
mixture will increase in temperature by about 13.degree. C. for each 
weight percent copolymer or 5 weight percent x 13.degree. C./wt. 
%=65.degree. C. To maintain an outlet temperature of 35.degree. C., it 
will thus require a feed that has been prechilled to 35.degree. 
C.-65.degree. C.=30.degree. C. In this instance that external cooling is 
used to absorb the heat of polymerization, the feed inlet temperature 
could be higher with the other temperature constraints described above 
otherwise being applicable. 
Because of heat removal and reactor temperature limitations, the preferred 
maximum copolymer concentration at the reactor outlet is 25 wt./100 wt. 
diluent. The most preferred maximum concentration is 15 wt/100 wt. There 
is no lower limits to concentration due to reactor operability, but for 
economic reasons it is preferred to have a copolymer concentration of at 
least 2 wt/100 wt. Most preferred is a concentration of at least 3 wt/100 
wt. 
The rate of flow of the reaction mixture through the reactor should be high 
enough to provide good mixing of the reactants in the radial direction and 
minimize mixing in the axial direction. Good radial mixing is beneficial 
not only to both the Intra-and Inter-CD of the copolymer chains but also 
to minimize radial temperature gradients due to the heat generated by the 
polymerization reaction. Radial temperature gradients will tend to broaden 
the molecular weight distribution of the copolymer since the 
polymerization rate is faster in the high temperature regions resulting 
from poor heat dissipation. The artisan will recognize that achievement of 
these objectives is difficult in the case of highly viscous solutions. 
This problem can be overcome to some extent through the use of radial 
mixing devices such as static mixers (e.g., those produced by the Kenics 
Corporation). 
It is believed that residence time of the reaction mixture in the mix-free 
reactor can vary over a wide range. It is believed that the minimum could 
be as low as about 1 second. A preferred minimum is about 10 seconds. The 
most preferred minimum is about 15 seconds. It is believed that the 
maximum could be as high as about 3600 seconds. A preferred maximum is 
about 1800 seconds. The most preferred maximum is about 900 seconds. 
With reference to the accompanying drawings, particularly FIG. 1, reference 
numeral 1 generally refers to a premixing device for premixing the 
catalyst components. For purposes of illustration, it is assumed that a 
copolymer of ethylene and propylene (EPM) is to be produced using as 
catalyst components vanadium tetrachloride and ethyl aluminum sesqui 
chloride. The polymerization is an adiabatic, solution polymerization 
process using hexane solvent for both the catalyst system and the reaction 
mixture. 
The premixing device 1 comprises a temperature control bath 2, a fluid flow 
conduit 3 and mixing device 4 (e.g., a mixing tee). To mixing device 4 are 
fed hexane solvent, vanadium tetrachloride and ethyl aluminum sesqui 
chloride through feed conduits 5, 6 and 7, respectively. Upon being mixed 
in mixing device 4, the resulting catalyst mixture is caused to flow 
within conduit 3, optionally in the form of a coiled tube, for a time long 
enough to produce the active catalyst species at the temperature set by 
the temperature bath. The temperature of the bath is set to give the 
desired catalyst solution temperature in conduit 3 at the outlet of the 
bath. 
Upon leaving the premixing device, the catalyst solution flows through 
conduit 8 into mixing zone 9 to provide an intimate mixing with hexane 
solvent and reactants (ethylene and propylene) which are fed through 
conduit 10. Any suitable mixing device can be used, such as a mechanical 
mixer, orifice mixer or mixing tee. For economic reasons, the mixing tee 
is preferred. The residence time of the reaction mixture in mixing zone 9 
is kept short enough to prevent significant polymer formation therein 
before being fed through conduit 11 to tubular reactor 12. Alternatively, 
streams 8 and 10 can be fed directly to the inlet of reactor 12 if the 
flow rates are high enough to accomplish the desired level of intimate 
mixing. The hexane with dissolved monomers may be cooled upstream of 
mixing zone 9 to provide the desired feed temperature at the reactor 
inlet. 
The tubular reactor is shown with optional feed and take off points. Where 
the catalyst comprises only a single polymer species one or more take off 
points, 13, are used to withdraw polymer fractions at different points 
along the polymerization path. In order to maintain constant flow, 
additional solvent may be added to make up the volume of material 
withdrawn. Additional catalyst and monomer can be introduced through line, 
14, or line, 15. The polymer withdrawn through line, 13, is combined with 
all other fractions withdrawn and collected with the reactor effluent for 
deashing and finishing. 
Where more than one catalyst species is used, multiple premixing devices, 
1, are used. The mixed catalyst can be directed to mixing zone, 9, for 
mixing with additional catalyst species and monomer or the effluent form 
the premixing devices can be combined prior to the mixing zone. 
Where VCL.sub.4 and VOCl.sub.3 are used as the catalyst species in 
conjunction with ethylaluminum sesquichloride (EASC), the molar ratio of 
VCl.sub.4 /VOCl.sub.3 can be about 0.10 to about 0.005, more preferably 
about 0.5 to about 0.02, most preferably about 3 to about 0.05. The amount 
of the total polymer and the molecular weight of each component will be 
determined by the ratio, and the feed locations and take off points along 
the reactor. 
The molar ratio of alkyl aluminum sesquihalide to vanadium components 
(VCl.sub.4 plus VOCl.sub.3) can be about 1 to about 40, preferably about 2 
to about 20, more preferably about 3 to about 10, e.g., about 5 to about 
10. The alkyl group of the sesquihalide is preferably a C.sub.1 -C.sub.6 
alkyl group, preferably ethyl. The halide can be bromine, chlorine or 
iodine, preferably chlorine. The preferred aluminum co-catalyst is 
ethylaluminum sesquichloride (EASC). In this system the two independent, 
non-interacting, mutually compatible catalyst systems are VCl.sub.4 /EASC 
and VOCl.sub.3 /EASC. 
In a preferred embodiment a Lewis base moderator is incorporated into the 
catalyst system. The molar ratio of VCl.sub.4 to base can be about 0 to 
about 2/1, preferably about 1/1 to about 1.5/1, more preferably about 1/1 
to about 1.2/1. Illustrative, non-limiting examples of lewis bases 
suitable for use in the practice of this invention are NH.sub.3, phenol, 
cyclohexanone, tetrahydrofuran, acetylacetone and tri-n-butyl-phospine. 
The lewis base decreases the catalyst activity, and suppresses some long 
chain branching reactions. 
The polymer derived from the process of this invention is deashed and 
finished using conventional methods. Where the polymodal MWD is achieved 
by withdrawing product and different points or times from the reactor, the 
polymer streams are preferably blended and a single deashing and finishing 
process used. The result is a thoroughly mixed polymer blend which is 
uniform with respect to its MWD. Alternately, each process stream can be 
finished independently and combined by mechanical mixing. 
Having thus described the above illustrative reactor system, it will 
readily occur to the artisan that many variations can be made within the 
scope of the present invention. For example, the placement and number of 
multiple feed sites, the choice of temperature profile during 
polymerization and the concentrations of reactants can be varied to suit 
the end-use application. 
By practicing processes in accordance with the present invention, 
alpha-olefin copolymers having polymodal MWD with each molecular weight 
fraction having very narrow MWD can be made by direct polymerization. 
Although narrow MWD copolymers can be made using other known techniques, 
such as by fractionation or mechanical degradation, these techniques are 
considered to be impractical to the extent of being unsuitable for 
commercial-scale operation. As regards EPDM made in accordance with the 
present invention, the products have enhanced cure properties at a given 
Mooney Viscosity. 
A lubricating oil composition in accordance with the present invention 
comprises a major amount of basestock lubricating oil (lube oil) of 
lubricating viscosity which contains an effective amount of viscosity 
index improved being a copolymer of ethylene and at least one other 
alpha-olefin as described in detail above. More specifically, the 
copolymer should have a MWD characterized by at least one of a ratio of 
M.sub.w /M.sub.n of less than 2 and a ratio of M.sub.z /M.sub.w of less 
than 1.8. The preferred ration of M.sub.w /M.sub.n is less than about 1.6, 
with less than about 1.4 being preferred. The preferred M.sub.z /M.sub.w 
is less than about 1.5, with less than about 1.3 being most preferred. 
In a preferred embodiment of this invention, the Intra-CD of the copolymer 
is such that at least two portions of an individual intra-molecularly 
heterogeneous chain, each portion comprising at least 5 wt % of said 
chain, differ in composition from one another by at least 5 wt % ethylene. 
The Intra-CD can be such that at least two portions of copolymer chain 
differ by at least 10 wt % ethylene. Differences of at least 20 wt %, as 
well as 40 wt %, ethylene are also considered to be in accordance with the 
present invention. 
In such an embodiment, it is preferred that th Inter-CD of the copolymer is 
such that 95 wt % of the copolymer chains have an ethylene composition 
that differs from the copolymer average wt % ethylene composition by 15 wt 
% or less. The preferred Inter-CD is about 13% or less, with the most 
preferred being about 10% or less. 
With reference to processes for making copolymer in accordance with the 
present invention, it is well known that certain combinations of vanadium 
and aluminum compounds that can comprise the catalyst system can cause 
branching and gelation during the polymerization for polymers containing 
high levels of diene. To prevent this from happening Lewis bases such as 
ammonia, tetrahydrofuran, pyridine, tributylamine, tetrahydrothiophene, 
etc., can be added to the polymerization system using techniques well 
known to those skilled in the art. 
Where the polymodal molecular weight distribution is achieved by 
withdrawing polymer fractions from the reactor, it will be evident from 
reference to this disclosure that whether a tubular reactor or batch 
reactor is used, that time is the critical parameter for determining when 
or where to withdraw polymer from the reaction zone and can be determined 
without undue experimentation. For example, a pilot plant scale tubular 
reactor can be equipped with a multiplicity of take off points. By running 
the reactor with withdrawing polymer from the system the base case is 
determined to fix the molecular weight of the polymer for the full 
reaction time to be used. 
A series of runs can then be made, withdrawing polymer from the tubular 
reactor, a different point along the tube for each run. By converting the 
distance along the tube to time of reaction after introduction of 
catalyst, a plot can be made of molecular weight as a function of reaction 
time for a given catalyst/monomer/solvent system. In sealing up the 
reactor for commercial operations, there will be a 1 to 1 relationship in 
scale up as to time. Hence, although the reactor will be longer, the total 
reaction time will be the same; only the stream volume and velocity will 
be different. The molecular weight/reaction time plot can be used to 
position take off points. For flexibility in selecting the product 
characteristics of a particular polymodal MWD product, a multiplicity of 
take off points can be installed, not all of which will be used in 
preparing a particular product with predetermined specifications. 
Similarly, inlet ports can be located at different locations for the 
introduction of additional monomer or catalyst streams. By introducing 
fresh monomer downstream of the inlet, the MWD of the polymer will be 
modified. So long as the polymerization is carried out in this manner the 
polymer will be a polymodal MWD polymer of narrow MWD fractions. Similar 
results are achieved by introducing fresh premixed catalyst with the 
additional monomer feed. 
The advantages of the instant invention may be more readily appreciated by 
reference to the following examples. 
It will be evident from this disclosure to those skilled in the art that 
the polymodal MWD polymers of this invention can be prepared by blending 
the product of runs prepared under different conditions or using different 
catalyst. For example, one polymerization can be conducted using VCl.sub.4 
/EASC as the catalyst and another conducted using VOCl.sub.3 /EASC as the 
catalyst. The product of the two runs can then be blended to form a 
bimodal MWD polymer blend. Other variations can be used to generate 
polymer species of different M.sub.w to prepare polymodal MWD 
compositions. EXAMPLE I 
This example illustrates the method of this invention for preparing an EPM 
wherein polymer product is removed from the reactor at a point 
intermediate between the reactor inlet and outlet. The polymerization 
reactor was a one-inch diameter pipe equipped with Keniis static mixer 
elements along its length. The polymerization was conducted so that the 
residence time in the reactor was 56 seconds. A take off port was located 
downstream of the inlet at a distance equivalent to 20 seconds residence 
time. 
Hexane was used as the solvent, VCl.sub.4 as the catalyst, and Al.sub.2 
Et.sub.3 Cl.sub.3 as the cocatalyst. Hexane is purified prior to use by 
passing over 4A molecular sieves (Union Carbide, Linde Div. 4A 1/16" 
pellets) and silica gel (W. R. Grace Co., Davidson Chemical Div., PA-400 
20-4 mesh) to remove polar impurities which act as catalyst poisons. 
Gaseous, ethylene and propylene is passed over hot (270.degree. C.) CuO 
(Harshaw Chemical Co., CO1900 1/4"' spheres) to remove oxygen followed by 
mal sieve treatment for water removal and then combined with hexane 
upstream of the reactor and passed through a chiller which provided a low 
enough temperature to completely dissolve the monomers in the hexane. 
A catalyst solution is prepared by dissolving 18.5 g of vanadium 
tetrachloride, VCl.sub.4, in 5.0 1. of purified n-hexane. The cocatalyst 
consists of 142 g of ethylaluminum sesquichloride, Al.sub.2 Et.sub.3 
Cl.sub.3, in 5.0 1. of purified hexane. The two solutions are premixed at 
0.degree. C. for ten seconds. Typical feed rates and reacting conditions 
are shown in Table I. 
TABLE I 
______________________________________ 
Reactor Inlet Temperature (.degree.C.) 
-10 
Reactor Outlet Temperature (.degree.C.) 
0 
Reactor Feed Rates 
Hexane (Kg/hr) 60.3 
Ethylene (kg/hr) 0.22 
Porpylene (kg/hr) 2.0 
VCl.sub.4 (g/hr) 2.22 
Al.sub.2 Et.sub.3 Cl.sub.3 (g/hr) 
17 
Catalyst Premixing Temperature (.degree.C.) 
0 
Catalyst Premixing Time (sec) 
10 
Reactor Residence Time (sec) 
56* 
______________________________________ 
*Steady state residence time with no take off is 50 seconds. 
The reactor is allowed to reach steady state and a product stream is then 
withdrawn from the take off port at about 17 kg/hr. The system is again 
allowed to reach steady state and effluent from the take off port (ca. 
1.71 kg/hr) is collected and blended with effluent from the reactor outlet 
(ca. 6.83 kg/hr). The product is deashed and stripped. The resulting 
polymer is an EPM with a bimodal MWD. EXAMPLE II 
Example I is repeated except that no effluent is taken from the take off 
port and VOCl.sub.3 /EASC is used as an additional catalyst. 
The second catalyst solution is prepared by dissolving 18.5 g of VOCl.sub.3 
in 5.0 1. of purified hexane. The cocatalyst consists of 142 g of Al.sub.2 
Et.sub.3 Cl.sub.3 in 5.0 1. of purified hexane. The VCl.sub.4 and 
VOCl.sub.3 are blended with cocatalysts in separate premixing units. The 
two premixed catalyst streams are then mixed with the monomer/hexane 
stream and fed into the reactor. Reactor residence time is 50 seconds. 
Otherwise all conditions are the same as in Example I. After steady state 
is achieved, the reactor effluent is deashed, washed and stripped of 
solvent. The resulting polymer is a bimodal MWD EPM. 
EXAMPLE III 
Example I is repeated except that no take off port effluent is collected 
and the catalyst and feed streams are split. About 2/3 of the 
monomer/hexane stream and 2/3 of the premixed catalyst are mixed and fed 
to the reactor inlet and the remaining 1/3 of the monomer/hexane feed is 
mixed with the remaining catalyst stream and fed into the reactor at a 
point midway between the reactor inlet and outlet. The EPM product is a 
polymodal MWD polymer.