Note: Descriptions are shown in the official language in which they were submitted.
WASHING MAGNESIUM REDUCING AGENT PREPARED
IN ABSENCE OF COMPLEXING DILUENT
Background of the Invention
l`his invention relates to magnesium reduced titanium tetrahalide
catalyst systems.
It is known to reduce titanium tetrahalides with Grignard reagents,
that is, RMgX compounds produced by reacting magnesium and an organic halide
in the presence of ether. It is also known to produce what is termed in the
art a "solvent]ess" Grignard, which is produced by reacting magnesium metal
with an organic halide in the presence of a solvent which is designated as a
nonsolvating solvent (i.e. an inert noncomplexing diluent) such as a non-
complexing hydrocarbon as distinguished from an ether. True Grignard reagents,
as a practical matter, present serious problems as reducing agents in the
production of catalysts in view of the difficulty in removing the large amount
of ether and the remaining complexed ether can reduce the effectiveness of
olefin polymerization catalyst systems prepared with the thus treated Grignard
reagent.
With olefin polymerizations, particularly the polymerization of
ethylene or predominantly ethylene-containing olefin mixtures, it has been
found to be more economical to carry out the polymerization at a temperature
low enough that the resulting polymer does not go into solution in the liquid
diluent used, and to recover the polymer without elaborate catalyst removal
steps. This results in residual catalyst remaining in the polymer and thus
requires high productivity rates in order to be practical.
Summary of the Invention
It is an object of this invention to provide a simplified method of
producing active titanium catalyst for olefin polymerization;
It is a further object of this invention to provide a catalyst system
capable of high productivities;
It is yet a further object of this invention to avoid the necessity
for removing ether from catalyst components; and
It is a further object of this invention in one aspect thereof to
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provide a magnesium reducing agent for the reduction of titanium tetrahalide
without the use of any extraneous diluent.
In accordance with this invention a magnesium reducing agent pre-
pared by the dropwise addition of an organic halide onto magnesium metal is
washed with an inert liquid hydrocarbon. Either before or after this washing
the magnesium reducing agent is contacted with an organoaluminum compound to
give a cocatalyst which is thereafter contacted with a titanium tetrahalide
to produce the catalyst.
Description of the Preferred Embodiments
The organic halide can be a saturated or unsaturated hydrocarbyl
halide of formula RX wherein R is an alkynyl, alkenyl, alkyl, aryl, cyclo-
alkenyl or cycloalkyl radical or combinations thereof such as aralkyl and the
like having 1 to about 12 carbon atoms per molecule and X represents a halogen
atom, preferably chlorine or bromine. The organic halide can also be a poly-
halogenated hydrvcarbyl halide of formula R'X2 in which R' is a saturated
divalent aliphatic hydrocarbyl radical containing from 2 to about 10 carbon
atoms per molecule and X is a halogen atom as set out hereinabove. Exemplary
organic halides include methyl chloride, n-butyl bromide, n-pentyl chloride,
n-dodecyl chloride, allyl bromide, 1,2-dibromoethane, 1,4-dichlorobutane,
l,10-dibromodecane, cyclohexyl chloride, bromobenzene, and the like. A
primary alkyl halide such as n-pentyl chloride is presently preferred.
The magnesium is in the form of the free metal, preferably in the
form of a powder.
Preferably the reaction between the organic halide and the magnesium
metal to form the magnesium reducing agent is carried out in the absence of
any extraneous diluent. This can be done by simply adding the organic halide
to magnesium metal powder in a container preferably with some stirring or
agitation over a relatively long period of time, for instance 1 to 10 hours.
It is also within the scope of the invention to carry out the reaction between
the organic halide and the magnesium metal in the presence of a noncomplexing
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diluent such as a noncomplexing hydrocarbon diluent. Suitable such diluents
include pentane, hexane, cyclohexane, methylcyclopentane, and the like, the
same types of inert hydrocarbons suitable for use as diluents or solvents in
the polymerization of l-olefins being suitable for use as diluents in the pro-
duction of the magnesium reducing agent. In all events, a complexing diluent
such as ether is avoided.
The organic halide can be added to the magnesium metal in an amount
within the range of 0.25:1 to 1:0.25 (moles organic halide/gram atoms Mg).
Preferably, however, about a stoichiometric amount (1/1) of halide is used.
The magnesium reducing agent is then washed with a dry nonreactive
(inert) normally liquid hydrocarbon 1 to 4 or more times. The hydrocarbon can
be selected from among paraffins, cycloparaffins and aromatics having 2 to
about 20, preferably 5 to 12 carbon atoms per molecule. Exemplary compounds
include n-pentane, n-hexane, n-heptane, isooctane, dodecane, cyclohexane,
benzene, toluene, xylenes and mixtures thereof. Preferably the wash liquid is
the same as that to be used as a diluent in the subsequent polymerization or
else is compatible therewith. The treating temperature is normally accomplished
at room temperature, i.e., about 25C although temperatures ranging from
about 0 to 100C or higher can be used depending upon the boiling point or
freezing point of the treating liquid. Generally, the wash treatment is
carried out on the magnesium reducing agent/organoaluminum compound cocatalyst
mixture since the mixture forms a friable mass. However, it is within the
scope of this invention to wash magnesium reducing agent prior to its contact
with the organoaluminum compound. It is speculated that the wash treatment
removes some material that has a deleterious effect on the amount of polymer
made. At any rate, the wash treatment is effective in substantially improving
productivity of the catalyst system prepared with the washed product.
The term "in the absence of any extraneous diluent" (i.e., added
diluent) as used throughout the specification and claims is meant to exclude
the introduction of any complexing solvent or any noncomplexing inert diluent
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such as a hydrocarbon. Of course the organic halide itself is a liquid.
If exhaustive washing of the cocatalyst mixture is practiced, it is
noted that it is possible to remove some or all of the organoaluminum compound.
When enough is lost to adversely affect the resulting catalyst, it is necessary
to replace it with additional material since in its absence an inactive
catalyst system results.
The magnesium reducing agent can be washed in any manner known in the
art. For instance the inert hydrocarbon can simply be added to the magnesium
reducing agent and the mixture agitated and thereafter allowed to settle and
the supernatant liquid decanted off. Alternatively the wash liquid can be
removed by filtration or by using a centrifuge. It is frequently desirable to
ball mill the magnesium reducing agent with the inert hydrocarbon wash liquid
in both embodiments wherein the organoaluminum compound is already present and
in the embodiments where it is not. In addition to ball milling, of course,
pebble milling, rod milling, colloid milling and the like can also be used.
A typical analysis of the magnesium reducing agent of this invention
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 illustrative 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
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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.
Obviously much of the soluble portion of the magnesium reducing agent
will be removed by this washing step, but the resulting insoluble portion has
different characteristics from simple Mg-C12 prepared directly.
Preferred organoaluminum compounds are hydrocarbyl aluminum compounds
of formula R"2AlZ in which R" is the same or different and is selected from
alkyl and aryl radicals containing from 1 to about 12 carbon atoms per molecule
and Z is a hydrogen atom or a halogen atom, preferably chlorine or bromine.
Exemplary compounds include dimethylaluminum bromide, diethylaluminum chloride,
diisobutylaluminum hydride, diphenylaluminum chloride, ethylphenylaluminum
chloride, di-n-dodecylaluminum bromide and the like. A presently preferred
compound is diethylaluminum chloride. As noted hereinabove, the organoaluminum
compound can be added either before or after the washing but in either event
is added before contact of the magnesium reducing agent with the titanium
tetrahalide. Compounds of the formula AlR"3, R"AlX2 and R"2AlOR" where R" is
as above and X is a halogen atom, preferably chlorine or bromine can also be
used. Exemplary compounds are triethylaluminum, ethylaluminum dichloride and
diethylaluminum ethoxide.
The titanium tetrahalide is either titanium tetrachloride, titanium
tetrabromide, or titanium tetraiodide, preferably titanium tetrachloride.
It is within the scope of this invention to use one or more adjuvants,
these being polar organic compounds, i.e., Lewis bases (electron donor compounds)
either premixed with the organoaluminum component or as a third entity along
with the magnesium reducing agent, organoaluminum compound and titanium tetra-
halide or both. Suitable compounds for this purpose are described in U. S.
Patent 3,642,746. They include alcoholates, aldehydes, amines, amides, arsines,
esters, ethers, ketones, nitriles, phosphines, phosphites, phosphoramides,
sulfones, sulfoxides,
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and stibines. Exemplary compounds include sodium ethoxide, benzaldehyde,
acetamide, triethylamine, trioctyl arsine, ethyl acetate, diethyl ether,
acetone, benzonitrile, triphenyl phosphine, triphenyl phosphite, hexamethyl
phosphoric triamide, dimethyl sulfone, dibutyl sulfoxide and triethyl stibine.
Triethylamine and triphenyl phosphite are particularly preferred.
Presently preferred adjuvants are the lower alkyl esters 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" ', -NO2, -CN, -CHO,
10 -COR" ', -COOR" ', -CONH2, -CONR"'2, -SO2R"', and CF3. The R" ' group is
an alkyl radical of 1 to 4 carbon atoms. Exemplary compounds include ethyl
anisate (ethyl p-methoxybenzoate), ethyl benzoate, methyl benzoate, ethyl
p-dimethylaminobenzoate, ethyl p-fluorobenzoate, isopropyl p-diethylamino-
benzoate, butyl p-fluorobenzoate, n-propyl p-cyanobenzoate, ethyl p-trifluoro-
methylbenzoate, methyl p-hydroxybenzoate, methyl p-acetylbenzoate, methyl
p-nitrobenzoate, ethyl p-mercaptobenzoate and mixtures thereof. Particularly
preferred esters are ethyl anisate and ethyl benzoate.
Generally when polymerizing ethylene, which is the preferred utility
for the catalysts of this invention, no adjuvant is used. Generally an
adjuvant is used in the less preferred embodiments of this invention where
the catalyst is used for propylene polymerization.
The molar ratio of organoaluminum compound(s) to adjuvant(s) is
usually 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 system of this invention can be used unsupported or
supported on a particulate material including silica, silica-alumina, magnesia,
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magnesium carbonate, magnesium chloride, magnesium alkoxides such as magnesium
methoxide, and the like. The weight ratio of titanium tetrahalide to support
can vary from about 0.05:1 to about 1:1, more preferably from about 0.1:1 to
about 0.3:1.
The catalyst system of this invention is useful for the polymeri-
zation of mono-l-olefins having 2 to 8 carbon atoms per molecule. It is of par-
ticular value in the polymerization of ethylene polymers and copolymers of
ethylene and a minor amount of another mono-l-olefin such as propylene,
butene-l or hexene-l. It is possible utilizing the catalyst system of this
invention which gives such high productivities to carry out such polymeri-
zations, particularly the polymerization of ethylene and predominantly ethylene-containing l-olefin mixtures in an inert diluent at a temperature as described
hereinbelow wherein the polymer formed is insoluble in the liquid diluent and
is simply separated therefrom and utilized with no elaborate catalyst removal
steps.
The polymerization conditions employed in the process are similar to
other related processes in which a catalyst system comprising a titanium
tetrahalide and an organoaluminum compound are used. The polymerization tem-
perature generally falls within the range of 0 to 150C, more preferably from
about 40 to about 112C. Any convenient partial pressure of ethylene is used.
It generally falls within the range of about 10 to 500 psig (69 to 3447 kPa).
The titanium concentration can vary between about 0.0005 to 10, preferably
between about 0.001 to 2 milligram atoms per liter of diluent.
As is known in the art, control of the molecular weight of the
polymer can be accomplished by the presence of hydrogen in the reactor during
polymerization.
In general, the charge order of the various components to the
reactor consists of adding the washed magnesium reducing agent/organoaluminum
compound cocatalyst mixture, then the titanium compound, the diluent and
finally hydrogen, if used. The diluent is a hydrocarbon unreactive under the
polymerization conditions used. Examples of suitable diluents include iso-
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butane, n-heptane, cyclohexane and the like. The reactor and its contents are
then heated to the desired polymerization temperature, monomer such as ethylene
and comonomer, if used, are added and polymerization begins. Polymerization
times can vary from about 0.1 to 5 hours or more.
The resulting polymers are useful for Eabrication by means of con-
ventional equipment into fibers, film, molded articles and the like.
Example
In a dry flask equipped with a dropping funnel, condenser and
stirrer was placed 60 g (2.47 gram atoms) of 50 mesh magnesium powder. While
gently stirring the magnesium metal under a nitrogen atmosphere, 263.5 g
(2.47 moles) of dry n-pentyl chloride was slowly added through the funnel at
a rate sufficient to keep unreacted alkyl halide gently refluxing. Addition
time was 4 hours. At the conclusion of the reaction, 300 ml of dry n-hexane
were added to the flask and the stirred mixture was heated to boiling and re-
fluxed for 4 hours. Following this treatment, the flask was transferred to a
dry box and the hexane was removed under reduced pressure leaving behind the
magnesium reducing reagent as a gray residue. Portions of the powdered
solid were individually slurried with a 25 weight percent solution of diethyl-
aluminum chloride (DEAC) dissolved in n-heptane using 3.4 ml of the DEAC solu-
tion per gram of magnesium reducing agent. In addition to this, 5 ml of dryn-heptane was used per gram of magnesium reducing agent. Eive gram portions
of the magnesium reducing agent were used in preparing each cocatalyst com-
ponent except in runs 4 and 5 in which a 3.7 g portion was employed. Each
mixture was placed in a 12 ounce (355 ml) glass beverage bottle along with 50
g of 1/2" (1.27 cm) ceramic balls, capped and ball milled for the time shown.
The washing treatment, when used, consisted of diluting the ball milled slurry
with 6 times its volume of n-hexane (unless otherwise specified) followed by
milling for 15 minutes, allowing the mixture to settle overnight and decanting
the liquid, generally the same volume as the added n-hexane. Portions of the
cocatalyst were used in subsequent runs in which ethylene was polymerized in
the absence of hydrogen.
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A one gallon (3.87 liter) stirred reactor, purged with dry nitrogen,
was charged under an isobutane flush with cocatalyst mixture, titanium tetra-
chloride and 2 liters of dry isobutane as diluent, in the order named. The
reactor and its contents were heated to 100C, ethylene was admitted to give
a partial pressure of 100 psig (689 kPa) and polymerization commenced. Follow-
ing each run, the polymer was recovered by flashing off diluent and ethylene
and the weight of recovered polymer determined.
The number of wash treatments used for each cocatalyst, weight of
titanium tetrachloride charged (as titanium), calculated atom ratios of Al/Mg
and Al/Ti, run length in minutes, and productivity as g polymer per g titanium
are presented in the table.
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As indicated by the groupings in the table, the source of the mag-
nesium reducing agent used in the preparation of the cocatalyst used in the
runs grouped together was the same. Identical preparative methods for the
production of each magnesium reducing agent prepared was employed, however.
Ihus, the results in each group are fairly compared with one another, i.e.,
runs 1-3 by themselves, runs 4-5 by themselves, runs 6-9 by themselves and
runs 10-11 by themselves.
Control runs 1 and 4 are representative of productivity results ob-
tained using a ball milled cocatalyst which is not washed with a hydrocarbon
following milling and at the metal atom ratios employed. Runs 2, 3, 5, 6, 7,
and 9 show increased production of polyethylene when the cocatalyst is washed
1 to 2 times with a suitable hydrocarbon. The catalyst systems of runs 6, 7
and 9 were so active that it was necessary to prematurely terminate each run
prior to 60 minutes because it was not possible to control the polymerization
temperature at or near 100C. Run 8 indicates that washing the cocatalyst 5
times with the volume of hydrocarbon used per wash (about 6 times the volume
of cocatalyst) has substantially removed all the DEAC initially present in the
cocatalyst. Since the cocatalyst is inactive in the absence of a suitable
organoaluminum compound it was necessary to replace it to obtain an active
system as exemplified by run 9. Runs lO and 11 show that when only the mag-
nesium reducing agent portion of the cocatalyst mixture is washed with a
hydrocarbon a very active cocatalyst is obtained when DEAC is added to the
treated magnesium reducing agent. Run 11 shows that washing with an aromatic
hydrocarbon followed by a wash with a paraffin gives results comparable to a
paraffin wash only.
While this invention has been described in detail for the 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.
