Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymerizing in tubular or loop reactor
Reexamination Certificate
2001-08-07
2003-09-30
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymerizing in tubular or loop reactor
C526S352000, C526S154000, C526S158000, C526S908000
Reexamination Certificate
active
06627707
ABSTRACT:
BACKGROUND
This invention relates to olefin polymerization processes and the resultant polymer products.
Ultra-high molecular weight olefin polymers, such as polyethylene, are useful in many demanding and extremely critical applications, such as human joint replacements, gears, bullet proof vests, skis, and other applications. Since ultra-high molecular weight polymers cannot be pelletized after leaving the reactor, the polymer must be sold as a fluff or a powder. Therefore, particle size and toughness of the resultant polymer is critical.
Many commercial methods are available to produce olefin polymers, such as polyethylene. One of the most economical routes to most commercial grades of olefin polymers is a continuous loop/slurry process with a paraffin diluent wherein the polymerization process carried out at a temperature low enough that the resulting polymer is largely insoluble in the diluent. Unfortunately, most commercially acceptable ultra-high molecular weight polyethylenes traditionally are made using a stirred tank, i.e., batch process, in a heavy hydrocarbon diluent.
SUMMARY OF THE INVENTION
Therefore, it is an object of this invention to provide a novel catalyst system which can produce polyethylene.
It is another object of this invention to provide a novel catalyst system which can produce very tough, ultra-high molecular weight polyethylene.
It is still another object of this invention to provide a very tough, ultra-high molecular weight polyethylene.
It is a further object of this invention to provide an improved olefin polymerization process.
It is yet another object of this invention to provide an improved polymerization process for preparing ultra-high molecular weight polyethylene.
In accordance with this invention, a process is provided to polymerize ethylene in a loop/slurry process using a zirconium-containing catalyst system to produce a very tough, ultra-high molecular weight polyethylene.
In accordance with another embodiment of this invention, a very tough, ultra-high molecular weight polyethylene is provided.
In accordance with another embodiment of this invention an exceptionally broad molecular weight distribution polyethylene is provided.
In accordance with still another embodiment of this invention a polymerization process to produce an exceptionally broad molecular weight distribution polyethylene is provided.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Catalyst System Supports
Supports of the catalyst system of this invention must be alumina-containing material. As used in this disclosure, the term “support” refers to a carrier for another catalytic component. However, a support is not necessarily an inert material; a support can contribute to catalytic activity and/or catalytic productivity. Furthermore, a support can have an effect on the properties of the resultant polymer produced.
The alumina-containing material used in this invention can contain other ingredients which are present to produce some unrelated result and/or which do adversely affect the quality of the final catalyst system. For example, other metal oxides, such as boria, magnesia, silica, thoria, titania, zirconia, and mixtures thereof, can be present without adverse affects. Preferably, the support is at least 75 weight percent alumina, preferably 85 weight percent alumina, based on the weight of the alumina-containing material, in order to achieve optimum catalyst system quality, as well as improved polymer characteristics. Often, the alumina will comprise some silica.
The alumina-containing material, hereinafter also referred to as “alumina” or “base alumina”, must have a high surface area, large pore volume, and must be calcined prior to use. Usually, the surface area of the alumina, after one hour of calcination at 600° C., will be greater than about 200 square meters per gram (m
2
/g) and preferably within a range of about 200 to about 600 m
2
/g. Most preferably, the alumina will have a surface area within a range of about 250 to about 500 m
2
/g for easier catalyst loading, improved productivity, and greater durability. Usually, the pore volume of the alumina will be greater than about 0.5 milliliters per gram (ml/g) and preferably within a range of about 1.0 to about 2.5 ml/g. Most preferably, the alumina will have a pore volume within a range of 1 to 2 ml/g for greater durability.
Exemplary aluminas are commercially available. Preferred commercially available aluminas are commonly referred to as Ketjen B or Ketjen L aluminas. Typical Ketjen B or Ketjen L aluminas, as used in the present invention, will have typical analyses as given in Table A, below.
TABLE A
Ketjen B
Ketjen L
Loss on ignition (1hr., 1000° C., wt. % base)
25
25
Chemical Composition (wt. % cure base)
Alumina, Al
2
O
3
Balance
Balance
Sodium oxide, Na
2
O
0.1
0.15
Sulfate, SO
4
1.5
2.0
Silicon dioxide, SiO
2
1.0
5.0
Iron, Fe
0.03
0.03
Physical Properties
Surface Area, m
2
/g (1 hr., 600° C.)
340
380
Apparent bulk density, g/ml
0.3
0.3
Pore Size Distribution (radius)
<37.5 Å, ml/g
0.20
0.20
37.5-100 Å, ml/g
0.18
0.18
100-1000 Å, ml/g
0.74
0.74
1000-10,000 Å ml/g
0.51
0.71
10,000-75,000 Å ml/g
0.15
0.17
Total pore volume, ml/g
1.78
2.00
Particle Size Distribution (wt %)
<149 micron
98
95
<105 micron
65
60
< 74 micron
39
30
< 40 micron
19
15
Average particle size, micron
85
95
Prior to treatment with or contacting any additional support components or the active catalytic component, the alumina must be calcined. The alumina is calcined under conditions of temperature and time sufficient to convert substantially all of the alumina hydrate to gamma-alumina and to remove substantially all water. Generally, temperatures within a range of about 300° to about 900° C., for times within a range of about 1 minute to about 48 hours are sufficient. Temperatures under about 300° C. and times of less than about one minute can be insufficient to covert substantially all of the alumina to gamma-alumina. Temperatures of greater than about 900° C. and times of greater than about 48 hours do not convert a significantly greater portion of the alumina to gamma-alumina. Preferably, calcination temperatures within a range of about 500° to about 800° C. and times within a range of about 30 minutes to about 24 hours are employed. Most preferably, temperatures within a range of about 500° to about 700° C. and times within a range of about 1 hour to about 6 hours are employed. The calcining can be carried out under an oxidizing, reducing, or inert atmosphere; the principal purpose of the atmosphere is to sweep away moisture. However, for ease of use air is the preferred calcination atmosphere. As used in this disclosure, the terms “gamma-alumina”, “calcined alumina”, and “calcined, gamma-alumina” are used interchangeably and refer to the calcined alumina, described above.
Optionally, the alumina can be fluorided wherein the alumina support is treated with fluorine-containing compound. Exemplary fluoriding treatments can be found in U.S. Pat. No. 5,171,798 (McDaniel et al.), herein incorporated by reference. The alumina also can be treated with a phosphating agent to provide a phosphated-alumina. Exemplary phosphating methods are described in U.S. Pat. No. 5,001,204 (Klendworth et al.), herein incorporated by reference.
According to one embodiment of this invention, the particle size of the ultra high molecular weight polymer fluff is critical. It has been found that a correct selection of particle size of the catalyst system support particles can control the particle size of the resultant polymer fluff. Usually, catalyst system support particles are within a range of about 1 to about 40 microns, preferably within a range of about 2 to about 20 microns. Most preferably, in order to have an optimally sized polymer product, catalyst support particles are kept within a size range of 4 to 16 microns.
Catalyst System
Novel catalyst systems used in the present invention must contain zirconium. Zirconium can be combined with the catalyst system support in accordance with any method know in the a
Benham Elizabeth A.
McDaniel Max P.
Choi Ling-Siu
Kilpatrick & Stockton LLP
Wu David W.
LandOfFree
Olefin polymerization processes and products thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Olefin polymerization processes and products thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Olefin polymerization processes and products thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3096872