Note: Descriptions are shown in the official language in which they were submitted.
1~63~
MAGNESIUM REDUCING AGENT PREPARED IN ABSENCE OF
COMPLEXING DILUENT MILLED WITH ORGANOALUMINUM
Background of the Invention
This invention relates to magnesium reduced titanium tetrahalide
catalyst systems.
It is known to utilize true Grignard reagents of the formula RMgX
prepared in the presence of an ether to reduce titanium tetrahalide in the
production of catalysts. It is also known to produce what is termed in the
art a "solventless" Grignard, which is produced by reacting magnesium metal
with an organic halide in the presence of a solvent which is designated as
a non-solvating solvent (i.e., an inert non-complexing diluent) such as a
hydrocarbon as distinguished from an ether. This use of true Grignard rea-
gents presents serious difficulties, however, in the production of certain
catalysts, particularly in the production of olefin polymerization catalysts,
in view of the fact that the large amount of ether is difficult to remove and
the remaining complexed ether can reduce the effectiveness of olefin polymer
catalyst systems prepared with the thus treated Grignard reagents.
Because of greater process economics, it is desirable to carry out
olefin polymerization reactions, particularly polymerization reactions involvingethylene and predominantly ethylene copolymers, and an inert diluent at a
temperature at which the resulting polymer does not go into solution, with
the polymer being recovered without elaborate steps to remove the catalyst.
In order for this more economical method of manufacture to be feasible from
a practical standpoint, the catalyst must be capable of producing polymer in
high productivities in order to maintain the residual catalyst level in the
final polymer at a very low level.
Summary of the Invention
It is an object of this invention to provide a magnesium reducing
agent prepared in the absence of an ether;
It is a further object of this invention to provide a magnesium
reducing agent prepared in the absence of any extraneous diluent,
It is yet a further object of this invention to provide a catalyst
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1~9~3~t4
system capable of giving high productivity; and
It is yet a further object of this invention to provide an improved
catalyst for the polymerization of olefins such as ethylene without the
necessity for elaborate catalyst removal procedures from polymers thus
produced.
In accordance with this invention, an organic halide is added drop-
wise to magnesium metal in the absence of any complexing diluent to produce a
magnesium reducing agent which is milled with an organoaluminum compound, to
produce a cocatalyst which is thereafter contacted with a titanium tetrahalide.
Description of the Preferred Embodiments
The organic halide is a saturated or unsaturated hydrocarbyl halide
of formula RX in which X represents a halogen atom, preferably chlorine or
bromine, and R is selected from an alkynyl alkenyl, alkyl, aryl cycloalkenyl
and cycloalkyl radicals and combinations thereof such as aralkyl and the
like containing from 1 to about 12 carbon atoms per molecule. The organic
halide can also be a polyhalogenated hydrocarbyl halide of formula R'X2 where
X represents a halogen atom as before and R' is a saturated divalent aliphatic
hydrocarbyl radical containing from 2 to about 10 carbon atoms per molecule.
Exemplary organic halides include methyl chloride, n-butyl bromide, n-pentyl
chloride, n-dodecyl chloride, 1,2-dibromoethane, 1,4-dichlorobutane, 1,10-
dibromodecane, cyclohexyl chloride, bromobenzene and the like. A primary
alkyl halide such as n-pentyl chloride is a presently preferred compound.
The magnesium is in the form of the free metal, preferably in the
form of a powder.
The molar/gram atom ratio of organic halide to magnesium can vary
from 0.25:1 to 1:0.25, but is preferably about stoichiometric (l/l) moles
organic halide/gram atoms magnesium.
The organic halide is added dropwise to the magnesium metal, pref-
erably while the magnesium metal is being stirred with the addition taking
place slowly, preferably over a time of l to lO hours. It is preferred that
ld~9G3~
this be done in the absence of any extraneous diluent, the only liquid being
present being unreacted organic halide. It is also possible to utilize an
inert diluent such as an unreactive hydrocarbon in which case the magnesium
powder is dispersed in the hydrocarbon. Suitable hydrocarbons include
pentane, hexane, cyclohexane, heptane, and other hydrocarbons of the type
known in the art for use as diluents or solvents in olefin polymerization. In
either event, ether and other polar complexing diluents are avoided. Ether
is avoided, as noted hereinabove, because it is difficult to remove large
quantities of ether and ether complexes which can reduce the activity of the
catalyst system. In addition, the presence of the ether results in the
formation of a substantially different product and even the presence of an
inert hydrocarbon results in the formation of a different product than is
obtained without solvent. Generally this reaction is carried out at the
reflux temperature for the organic halide, which for pentyl chloride is 108C.
Temperatures of 80-110C are particularly suitable.
A typical analysis of the magnesium reducing agent of this inven-
tion using n-pentyl chloride added dropwise to magnesium in the absence of
any diluent is: `
Compound Weight Percent
Hydrocarbon Soluble Components
Di-n-pentylmagnesium 25.0
Decane 8.2
Di-n-decylmagnesium 1.1
Magnesium n-pentoxide 0.6
Hydrocarbon Insoluble Components
Magnesium chloride 55.2
Magnesium 4.9
Chloromagnesium hydride 2.3
n-Pentylmagnesium chloride 2.0
Magnesium n-pentoxide 0.7
This is shown for illustrated purposes and is not intended to limit
the scope of the invention. Substantial variation in the exact analysis from
that shown is obtained if a different halogen is used or if a different organo
radical is substituted for the n-pentyl. However, in all cases there is
i3~i~
present a substantial amount (at least 10 weight percent~ each of the diorgano-
magnesium and the magnesium halide. It is the reaction mixture that is the
magnesium reducing agent as defined herein.
The term "in the absence of any extraneous diluent" (i.e., added
diluent) as used throughout this specification and claims is meant to exclude
the introduction of any complexing solvent or any non-complexing or inert
diluent such as a hydrocarbon. Of course, the organic halide itself is a
liquid. Also after the reaction is essentially complete, an inert diluent or
solvent such as a hydrocarbon may be added to facilitate further handling.
The resulting magnesium reducing agent formed from the dropwise
addition of the organic halide onto the magnesium is then milled with an
organoaluminum compound to form a cocatalyst. Any conventional milling
technique known in the art can be utilized such as ball milling, rod milling,
pebble milling, and vibratory ball milling. The term milling as used herein
is also meant to encompass high speed sheer stirring, colloid milling or
passage through an orifice of a homogenizing value at high pressure, for
instance 1,000 psig or greater. All of these produce intensive milling con-
ditions wherein heat is generated and agglomerates are broken up. Milling
times will generally be in the range of 0.1 to 20, preferably 1 to 10, more
preferably 2 to 5 hours for conventional milling techniques. Use of vibratory
ball milling reduces the required times by a factor of about 10.
The milling process is generally carried out in a dry, inert atmos-
phere at ambient temperatures with cooling not normally required. If desired,
the milling can take place in the presence of a dry hydrocarbon diluent such
as hexane, heptane, cyclohexane, heptane, and the like which is inert, non-
solvating with respect to the magnesium reducing agent and nonreactive with
respect to the subsequent polymerization reaction. Alternatively, no diluent
at all can be used. It is frequently preferred, however, to utilize an inert
hydrocarbon diluent at this point even in the preferred embodiments of the
invention wherein no extraneous diluent of any kind is utilized during the
G36~.L
reaction of the organic halide and the magnesium. The presence of an inert
diluent at this point does not adversely affect the superior results obtained
by carrying out the reaction between the organic halide and the magnesium in
the absence of any extraneous diluent. The temperature during milling will
generally be 40-110C, preferably 50-70C. The resulting mixture can be con-
veniently stored in a dry vessel under an inert atmosphere until it or a
portion thereof is needed for use in a polymerization process.
A preferred organoaluminum compound is a hydrocarbylaluminum halide
compound of formula R"2AlX in which X is a halogen atom, preferably chlorine
or bromine, and each R" is the same or a different radical selected from alkyl
and aryl radicals having from 1 to about 12 carhon atoms. Exemplary compounds
include dimethylaluminum bromide, diethylaluminum chloride, diphenylaluminum
chloride, ethylphenylaluminum chloride, n-dodecylaluminum bromide and the like.
A presently preferred compound is diethylaluminum chloride.
The resulting milled product referred to herein as the cocatalyst is
then contacted with titanium tetrahalide wherein the halide is one of chlorine,
bromine, or iodine, preferably titanium tetrachloride. This may conveniently
be done by simply introducing the milled product and the titanium tetrahalide
in separate streams into the reactor.
It is within the scope of this invention to employ one or more
adjuvants, these being polar organic compounds, i.e., Lewis bases (electron
donor compounds) with the titanium tetrahalide component or the cocatalyst
component or both. Suitable compounds for this purpose are described in U. S.
Patent 3,642,746. They include alcoholates, aldehydes, amides, amines, arsines,
esters, ethers, ketones, nitriles, phosphines, phosphites, phosphoramides, sul-
fones, sulfoxides and stibines. Exemplary compounds include sodium ethoxide,
benzaldehyde, acetamide, triethylamine, trioctyl arsine, ethyl acetate, diethyl
ether, acetone, benzonitrile, triphenyl phosphine, triphenyl phosphite,
-5-
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hexamethyl phosphoric triamide, dimethyl sulfone, dibutyl sulfoxide, and
triethyl stibine triphenyl phosphite, triethylamine and dimethyl analine.
Preferred esters are the lower alkyl esters (i.e., 1 to 4 carbon
atoms per molecule) of benzoic acid which may be additionally substituted in
the para position to the carboxyl group with a monovalent radical selected
from the group consisting of -F, -Cl, -Br, -I, -OH, -OR"', -OOCR"', -SH, -NH,
-NR" ' 2 ~ -NHCOR" ', -N02, -CN, -CHO, -COR" ', -COOR" ', -CONH2, -CONR" ' 2 ~ -S02R" ',
and -CF3. The R" ' can also be an alkyl radical having 1-4 carbon atoms.
Exemplary compounds include ethyl anisate (ethyl-p-methoxybenzoate), methyl
benzoate, ethyl benzoate, ethyl p-dimethylaminobenzoate, ethyl p-fluoroben-
zoate, ethyl p-trifluoromethylbenzoate, methyl p-hydroxybenzoate, methyl p-
acetylbenzoate, methyl p-nitrobenzoate, ethyl p-mercaptobenzoate and mixtures
thereof. Particularly preferred compounds are ethyl anisate and ethyl
benzoate. Generally if an adjuvant is used at all, it is used in the poly-
merization of propylene. In the preferred embodiments of this invention
where ethylene is polymerized, an adjuvant is generally not used~
The molar ratio of organoaluminum compound(s) to adjuvant(s) is
generally in the range of about 1:1 to about 300:1. The atom ratio of
aluminum to magnesium can range from about 0.1:1 to about 4:1, more preferably
from about 0.5:1 to about 2:1. The molar ratio of titanium compound to
adjuvant(s) is generally in the range of about 1:1 to about 200:1. The atom
ratio of aluminum to titanium can range from about 20:1 to about 10,000:1,
more preferably from about 75:1 to about 5,000:1.
The catalyst component of this invention can be used unsupported or
supported on a particulate solid, i.e., silica, silica-alumina, magnesia~
magnesium carbonate, magnesium chloride, magnesium alkoxides such as magnesium
methoxide, and the like. The weight ratio of titanium tetrahalide to carrier
can vary from about 0.05:1 to about 1:1, more preferably from about 0.1:1 to
about 0.3:1.
The catalysts of this invention are useful in the polymerization of
3~
at least one mono-l-olefin having 2 to 8 carbon atoms per molecule and are of
particular utility in the polymerization of ethylene and copolymers containing
a predominant amount of ethylene. The catalysts are of particular utility in
the polymerization of ethylene or the copolymerization of ethylene and minor
amounts of propylene, butene-l or hexene-l, in an inert hydrocarbon diluent
at a temperature at which the resulting polymer is insoluble in the diluent.
Broadly, the polymerization conditions employed in this invention are
similar to other related processes in which a catalyst system comprising a
titanium tetrahalide and an organoaluminum compound are used. In the preferred
polymerization of ethylene in a particle form system wherein the resulting
polymer does not go into solution, the polymerization temperature generally
falls in the range of 0 to 150C, more preferably about 40 to 112C. Any
convenient partial pressure of ethylene can be used. The partial pressure
generally falls within the range of about 10 to 500 psig (69 to 3447 kPa).
The concentration of titanium compound per liter of diluent during the poly-
merization can vary within the range of about 0.0005 to 10, more preferably
from about 0.001 to 2 milliatoms titanium per liter of diluent.
The diluent used in the polymerization process is one which is
unreactive under the conditions employed. The diluent is preferably a hydro-
carbon such as isobutane, n-pentane, n-heptane, cyclohexane and the like.
As is known in the art, control of the molecular weight of the poly-
mer can be obtained by the presence of hydrogen in the reactor during poly-
merization.
In general, the charge order of the various components to the reactor
consists of adding the milled cocatalyst product, then the titanium compound
and finally the diluent. Hydrogen, if used, is then added. The reactor and
its contents are heated to the polymerization temperature, ethylene and
comonomer, if used, are admitted and polymerization begins. Run times can vary
from about 1/2 to 5 hours or longer.
The normally solid polymer produced utilizing the catalysts of this
invention can be subsequently converted into useful items such as fibers, film,
1~9~3~
molded articles, and the like, by means of conventional plastics fabrication
equipment.
Example I
In a dry flask equipped with dripping funnel, reflux condenser and
stirrer was placed 60 g (2.47 gram atoms) of 50 mesh magnesium powder. The
vessel was purged with dry nitrogen and while maintaining this atmosphere,
263.5 g (2.47 gram atoms) of dry n-pentyl chloride was slowly added through the
dropping funnel onto the gently stirred magnesium. The addition rate was
sufficient to keep unreacting alkyl halide gently refluxing with total addition
time of 4 hours. At the conclusion of the reaction, 300 ml of dry hexane were
added to the flask and the mixture was heated to boiling for 4 hours as the
contents were being stirred. Heating was then discontinued, the flask trans-
ferred to a dry box and the hexane diluent was removed under reduced pressure
leaving behind a gray solid as product.
Five gram portions of the powdered magnesium reducing agent were
individually charged in a dry nitrogen purge to 12 ounce (355 ml) glass
beverage bottles along with 50 g of ceramic balls, 25 ml of dry heptane
and 3.26 g of diethylaluminum chloride containined as a 25 weight percent
solution in dry heptane (amounting to 17 ml of solution). Each bottle was
capped and milled the length of time shown in the Table.
A one-gallon (3.87 liter) stirred reactor, purged with dry nitrogen,
was charged under an isobutane flush, with the milled cocatalyst mixture,
and then titanium tetrachloride sufficient to give a calculated weight of 0.4
mg titanium (0.008 milligram atoms), hydrogen and 2 liters of dry isobutane
as diluent. The reactor and its contents were heated to the chosen poly-
merization temperature, ethylene was admitted and a polymerization time of one
hour was allowed per run. Each polymer was recovered by flashing off diluent
and ethylene and the weight of polymer was determined.
The reaction temperatures used, amount of hydrogen used in each run,
calculated atom ratios of Al/Mg and Al/Ti, productivity determined as grams
1~9~36~
, . .
polyethylene made per gram titanium and melt index results are given in Table
I. Melt index is determined according to ASTM procedure D 1238-65T, condition
E. The same procedure, condition F, is used to determine high load melt index
(HLMI).
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--10--
1~963&4
At identical polymerization conditions, runs 1-4 indicate that
productivity is increased when the cocatalyst component is ball milled prior
to contact with the titanium tetrachloride. These data suggest that a ball
milling period of about 3 hours is necessary to achieve the optimum effect in
productivity in the inventive catalyst system. The improvement noted appears
to be leveling out or perhaps even decreasing slightly with longer ball mill-
ing times as productivity results of run 4 (10 hours ball milling) are some-
what lower than productivity results of run 3 (3 hours ball milling). At any
rate, substantially better results are obtained by ball milling the cocatalyst
mixture compared to a control run employing a portion of the same cocatalYst
mixture which is not ball milled. Runs 5-7 show that productivity is
directly related to the ethylene partial pressure with more polymer being
produced as the amount of ethylene charged to the reactor is increased. Runs
8-15 were conducted at a polymerization temperature of 105C compared to a
polymerization temperature of 60C for runs 1-7. At similar hydrogen concen-
trations, the results indicate that more polymer is made at the higher temper-
ature as run 10 (470,000 g polymer per g titanium) shows compared to control
run 1 (270,000 g/g Ti). Runs 8-11 are identical in process conditions, each .
using portions of the same cocatalyst mixture, but differ in the amount of
hydrogen present in the reactor. The results for runs 9-10, based on produc-
tivity and melt index values, appear to be about what is expected in this
invention. However, run 8 values appear to be out of line, and it is believed
the results should be ignored as being spurious; at least a partial cause of
this is the relatively high level of hydrogen. The beneficial effects of ball
milling to cocatalyst is demonstrated in run 12, all other conditions equal
to runs 1 and 10, as productivity jumped to 1,020,000 g/g Ti. Runs 13 and 14
are similar to run 12 except more hydrogen is present in the reactor. Run 13
results suggest that much of the hydrogen might have been lost in this run
since the productivity results and melt index results are fairly close to
those of Run 12. Run 14 results are more indicative of what is expected,
since with increased hydrogen present in the reactor, the melt index of the
polymer is expected to increase and productivity is expected to decrease
somewhat. This is also shown in Run 15. The depressing effect on produc-
tivity with increasing amount of hydrogen is also shown in the results of Runs
10 and 11.
The HLMI/MI values obtained indicate that the polymers made in this
invention have relatively narrow molecular weight distributions. As the value
increases, the molecular weight distribution also increases.
Example II
This example compares the catalyst preparation steps of the invention
10 wherein the cocatalyst is milled prior to contact with the titanium tetrahalide
with ~he alternative procedure of either milling all three together or first
milling the magnesium reducing agent and titanium tetrachloride, and thereafter
contacting same with the organoaluminum compound.
DEAC TiC14 Heptane Productivity
Run No. Mg, g m mmoles mmolesml g/g Ti
16 Invention 5 17 27 0.032(1) 25 125,000
(TiC14 added after
organomagnesium
cpd. reducing agent
& DEAC are milled)
17 Control 5 17(1) 27 0.032 25 49,000
(DEAC added after
magnesium reducing
agent and TiC14 are
milled)
18 Control 5 17 27 0.032 25 70,000
(All 3, DEAC,
organomagnesium cpd.
reducing agent &
TiC14, milled
together)
(1) Added after ball milling.
A duplicate run under slightly different conditions (0.53 mmoles
TiC14) gave an advantage of 29,000 g polyethylene per g titanium in produc-
tivity between the invention sequence (as in Run 16), and a control sequence
wherein the DEAC was added after ball milling (as in Run 17). The produc-
tivity in all of these runs was low, probably due to the use of an inferior
batch of magnesium reducing agent. However, the comparative results between
1~63~i~
Runs 16, 17 and 18 are meaningful since the same techniques and reagents were
used in these three runs. However, the results cannot properly be compared
to Runs 1 to 15 so far as the absolute va]ues for productivity are concerned.
These data show that the sequence steps of the invention are
critical. Run 17 shows that an inferior result is obtained if the organo-
aluminum compound is added after the magnesium reducing agent and titanium
have been contacted. Similarly, Run 18 shows that milling all three of the
ingredients together gives an inferior result as compared with milling only
the magnesium reducing agent and the cocatalyst thereafter contacting same
with the titanium tetrahalide. However, on a comparable basis, these data
show an advantage for the sequence of the invention for ethylene polymerization.
While this invention has been described in detail for purpose of
illustration, it is not to be construed as limited thereby but is intended to
cover all changes and modifications within the spirit and scope thereof. '
