Terpolymers

Details Terpolymers Terpolymers

2000-01-18

2003-01-21

Teskin, Fred (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S129000, C526S130000, C526S160000, C526S335000

Reexamination Certificate

active

06509431

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to terpolymers of ethylene, an alpha olefin of 3 to 10 carbon atoms, preferably 4 to 10 carbon atoms, and a diene which contains 7 to 10 carbon atoms. The presence of the diene coincides with long chain branching in the terpolymer; the copolymer free of the diene exhibits no long chain branching. Long chain branching is desirable as it increases the processability of the resulting polymerization product.
SUMMARY OF THE INVENTION
This invention discloses that in a linear copolymer comprising ethylene and an amount of an alpha olefin, which is free of long chain branching, exhibiting a numerical value of MFR (I
21
/I
2
, measured according to ASTM D-1238) of 16 to 20 and M
w
/M
n
value of 2.0 to 3.5, the modification comprises a terpolymer containing an amount of alpha olefin, ethylene and units of a diene containing 7 to 10 carbon atoms, wherein the diene is present in an amount effective to increase the numerical value of MFR. The terpolymer exhibits M
w
/M
n
which is substantially identical to that of the corresponding linear copolymer without diene. The diene is selected from the group consisting of 1,7-octadiene, 1,8-nonadiene and admixtures thereof.
Terpolymers of ethylene, an alpha olefin, and a diene have been produced using a supported activated metallocene catalyst. Use of the metallocene catalyst led to high comonomer incorporation of the substituted olefins. Very small amounts of diene cause a substantial change in resin MFR[I
21
/I
2
, measured according to ASTM D-1238, Conditions E and F] without a significant change in Mw/Mn [compared to the counterpart resin free of any diene]. This change in resin MFR with substantially constant Mw/Mn is indicative of the introduction of long chain branching into the resin.
DETAILED DESCRIPTION OF THE INVENTION
The invention relates to terpolymers which contain ethylene units, units of an alpha olefin and as the third component a diene containing 7 to 10, preferably 7 to 9, carbon atoms. These terpolymers contain at least 80, usually at least 90, wt. % of ethylene units. The terpolymers contain up to 20 wt. % of alpha mono-olefin of 3 to 10 carbon atoms and 0.1 to 20 wt. % of diene of 7 to 10 carbon atoms.
Monomers
The monomers used in addition to ethylene comprise C
3
-C
10
alpha-olefins. Preferably, the products contain at least 80 wt. % ethylene units. The alpha olefins, alpha-monolefins, used with the ethylene in the present invention preferably contain 3 to 8 carbon atoms. Suitable alpha olefins include propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1, heptene-1, octene-1 and admixtures thereof. Preferably, the alpha-olefin comonomer comprise 1-butene, 1-hexene, 1-octene and admixtures thereof. The most preferred alpha olefin is hexene-1. Particular examples of combinations of the ethylene and alpha olefin include ethylene/1-butene, ethylene/1-hexene, ethylene/4-methyl-1-pentene, ethylene/1-butene/1-hexene, ethylene/propylene/1-hexene and ethylene/propylene/1-butene. Hydrogen may be used as a chain transfer agent in the polymerization reaction of the present invention. Any gas inert to the catalyst and reactants can also be present in the gas stream.
The diene preferably contains 6 to 10 carbon atoms, preferably 7 to 9 carbon atoms. Examples of the diene include 1,6-heptadiene; 1,7-octadiene; 1,8-nonadiene, 1,5-hexadiene and 1,9-decadiene were also used in the invention, but with lesser effect, than dienes of 7 to 9 carbon atoms on the change in MFR.
These products are prepared in the presence of a catalyst, described below, preferably under either slurry or more preferably under fluid bed gas phase catalytic polymerization conditions described below.
The products contain 0.1 to 2 ppm of transition metal, e.g., zirconium. The products also contain 5 to 100 ppm, preferably 10-50 ppm, of aluminum. Transition metal, e.g., zirconium and aluminum content of the products, is attributable to catalyst residues. The catalysts used to make the products of the invention are metallocenes of zirconium activated by aluminoxane.
The products are characterized by a density as low as 0.88 and up to less than 0.965 and preferably less than 0.94 g/cc. For applications herein, the density is greater than about 0.88, generally greater than 0.900 up to less than 0.965, preferably ranging from about 0.90 to 0.93 g/cm
3
.
The products of the invention exhibit a MI which can range up to 150 and up to 300 e.g., ranging from 0.01 to 300.
The low density products of the invention exhibit a melt flow ratio (MFR) which is at least 16, preferably from 16 to 60, and most preferably from 16 to 45. MFR is the ratio I
21
/I
2
[wherein I
21
is measured at 190° C. in accordance with ASTM D-1238, Condition F and I
2
is measured at 190° C. in accordance with ASTM D-1238, Condition E].
The M
w
/M
n
of these products ranges from about 2.0 to about 3.5. M
w
is the weight average molecular weight and M
n
is the number average molecular weight, each of which is calculated from molecular weight distribution measured by GPC (gel permeation chromatography). Products have been produced with M
w
/M
n
lower than 2.5, in the range of 2.0 to 3.5, preferably in the range of 2 to 3.
The Catalyst
The catalyst compositions employed to produce resins of the present invention contain one transition metal provided as a metallocene. The catalysts comprise a carrier, an activator of cocatalysts and at least one metallocene.
The carrier material is a solid, particulate, porous, inorganic or organic materials, but preferably inorganic material, such as an oxide of silicon and/or of aluminum. The carrier material is used in the form of a dry powder having an average particle size of from about 1 micron to about 250 microns, preferably from about 10 microns to about 150 microns. If necessary, the treated carrier material may be sieved to insure that the particles have an average particle size of preferably less than 150 microns. This is highly desirable in forming narrow molecular weight LLDPE, to reduce gels. The surface area of the carrier is at least about 3 square meters per gram (m
2
/gm), and preferably at least about 50 m
2
/gm up to about 350 m
2
/gm. When the carrier is silica, it is heated to preferably about 100° C. to about 850° C. and most preferably at about 250° C. The carrier material must have at least some active hydroxyl (OH) groups to produce the catalyst composition of this invention.
In the most preferred embodiment, the carrier is silica which, prior to the use thereof in the first catalyst synthesis step, has been dehydrated by fluidizing it with nitrogen and heating at about 250° C. for about 4 hours to achieve a surface hydroxyl group concentration of about 1.8 millimoles per gram (mmols/gm). The silica of the most preferred embodiment is a high surface area, amorphous silica (surface area=300 m
2
/gm; pore volume of 1.65 cm
3
/gm), and it is a material marketed under the trade names of Davison 952-1836, Davison 952 or Davison 955 by the Davison Chemical Division of W. R. Grace and Company.
To form the catalysts, all catalyst precursor components can be dissolved with an activator or cocatalyst such as aluminoxane and reacted with a carrier. The carrier material is reacted with an aluminoxane solution, preferably methylaluminoxane, in a process described below. The class of aluminoxanes comprises oligomeric linear and/or cyclic alkylaluminoxanes represented by the formula:
R—(Al(R)—O)
n
—AlR
2
for oligomeric, linear aluminoxanes and
(—Al(R)—O—)
m
for oligomeric cyclic aluminoxane
wherein n is 1-40, preferably 10-20, m is 3-40, preferably 3-20 and R is a C
1
-C
8
alkyl group and preferably methyl. Methylaluminoxane (MAO) is a mixture of oligomers with a very wide distribution of molecular weights and usually with an average molecular weight of about 1000. MAO is typically kept in solution in toluene.
In one preferred embodiment of aluminoxane, incorporation into the carrier depends on the pore volume of the silica. In this embodiment, the process of impregna

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