Olefin polymerization processes and products thereof

#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.

#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 (m2/g) and preferably within a range of about 200 to about 600 m2/g. Most preferably, the alumina will have a surface area within a range of about 250 to about 500 m2/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.