Polymerizations using adjuvant catalysts

Details Polymerizations using adjuvant catalysts Polymerizations using adjuvant catalysts

2002-12-19

2004-10-05

Rabago, Roberto (Department: 1713)

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

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S074000, C526S113000, C526S118000, C526S119000, C526S201000, C525S191000, C525S240000

Reexamination Certificate

active

06800700

ABSTRACT:

TECHNICAL FIELD
This invention relates generally to a method for producing low-crystallinity polyolefins. The invention relates more particularly to the production of sticky, substantially amorphous polyolefins that normally adhere to the walls of the reactor in which they are produced to such degree that such polyolefins are considered by those skilled in the art as being difficult to manufacture and process in conventional polyolefin manufacturing processes in commercially-significant quantities. The invention relates further to processes useful for rendering such sticky, substantially amorphous polyolefins processable using conventional polyolefin manufacturing equipment.
BACKGROUND INFORMATION
The polymerization of various olefins, including propylene, ethylene, and the like has been known in the chemical arts for some time. Generally speaking, in order to polymerize an olefin, one provides the olefin to be polymerized and contacts the olefin (monomer) with a catalytic material, which may include a co-catalyst, as the use of such is well-known in the art, under sufficient conditions of temperature and pressure to cause polymerization of the monomer to form a polymeric product. The conditions of temperature and pressure of the polymerization reaction may be varied, as well as the monomer(s) and catalyst(s) used and type of reaction vessel in which the polymerization is carried out. Also, hydrogen may be introduced during the polymerization to control the molecular weight of the polymer, and the use of hydrogen in this regard is well-known in the art.
One process for polymerization of olefins including, but not limited to propylene is known as the slurry process. In the slurry process, an inert organic solvent is fed into a closed reaction vessel and typically heated, with stirring. Then, a monomeric raw material is fed into the reaction vessel wherein some of the monomer dissolves in the solvent. Catalyst is fed to the stirred reactor and the monomer becomes polymerized. Polymer and solvent may be removed as a slurry (provided that the polymer, by its very nature, has no tendency to stick to the reactor walls) through a pipe in one of the sides or bottom of the reactor. The polymer is then separated from the solvent using means well known to those skilled in the polymer art, and the solvent is recycled. The process may be conducted as a batch process, and the monomer itself may function as the solvent, as in the case when propylene is employed under conditions in which it exists in the liquid state.
Another process useful for polymerizing olefins that is well-known to those skilled in the art is referred to as the “liquid pool” process, in which the solvent is an olefin which is to be polymerized in the polymerization. In such a process, the monomeric material (liquid propylene or other liquid alkene) and catalyst are fed into the reactor, which may be a stirred autoclave, and caused to polymerize by introducing catalyst (and co-catalyst if desired) under selected conditions of temperature, pressure, and added hydrogen.
Amorphous and low-crystallinity polyolefins are commercially important for their use in diverse products due to the unique combination of chemical and physical properties they possess, including chemical inertness, softness, flexibility, recyclability. Industrial interest in these materials has increased in recent times by the development of catalysts to produce them, as taught specifically in U.S. Pat. No. 5,948,720.
A number of patents disclose catalysts and processes to prepare amorphous or elastomeric polyolefins, including U.S. Pat. Nos. 4,524,195; 4,736,002; 4,971,936; 4,335,225; 5,118,768; 5,247,032; 5,539,056; 5,565,532; 5,608,018; 5,594,080; 5,948,720; 6,080,819; and 6,100,351, as well as European Patents EP 604908 and 693506, the entire contents of all aforesaid patents being herein incorporated by reference thereto. Several types of organometallic catalysts are useful to produce polyolefins and are conventionally referred to as “Ziegler-Natta” catalysts, metallocene catalysts and non-metallocene single-site catalysts. Catalysts known as “Ziegler-Natta” catalysts are well-known in the art to comprise a mixture of a base metal alkyl of the group I to III metals, and a transition metal salt of groups IV to VIII metals of the periodic table of the elements. A Ziegler-Natta catalyst is basically a complex derived from a halide of a transition metal, for example, titanium, chromium or vanadium with a metal metal alkyl that is typically an organoaluminum compound. The catalyst is usually comprised of a titanium halide supported on a magnesium compound. Metallocene catalysts are well-known to those skilled in the art to include in its structure two cyclopentadienyl ligands coordinated to a transition metal. Metallocene catalysts are known to be one type of “single-site” catalysts in which all the catalytically active sites are uniform in nature. Polymer produced by a single-site catalyst can have Mw/Mn value approaching 2, wherein Mw is the weight average molecular weight and Mn is the number average molecular weight of polymer. Non-metallocene single-site catalysts refer to all the single-site catalysts which do not have in their structure two cyclopentadienyl ligands coordinated to a transition metal. For purposes of this specification and the appended claims, the words “substantially amorphous” when referring to polyolefins means those having less than about 70 Joules per gram of crystallinity as measured using Differential Scanning Calorimetry according to ASTM method D-3417.
While the production of various amorphous and low-crystallinity polyolefins is possible owing to the relatively recent development of several catalysts therefor, it has been an ongoing problem in this art nevertheless that the harvest of these amorphous polyolefins from a reactor operated in liquid pool slurry processes has been thus far extremely difficult and in some cases even impossible to carry out on a commercial scale. This is because these sticky polymers typically tend to agglomerate on the walls and other portions of the reactor in which they are produced, thus fouling the reactor and other plant equipment. Among other complications caused by coatings of polymer on the walls of a reactor is that heat transfer capability between the walls of the vessel and the contents of the vessel is greatly reduced, which results in a reduced degree of control of the reaction conditions by the process operator. Such a loss of control of reaction temperature can have devastating consequences on the condition of the reactor, as well as the physical properties of the polymer products produced therein. Typically, to remove fouled material it is necessary to open the reactor and mechanically scrape the walls of the reaction vessel. Production of such “fouling” material is therefore viewed by those skilled in the art as being greatly undesirable, regardless of the properties of the polymeric materials so produced. This translates to a reduced overall potential for merchants of commerce to benefit the public by supplying polymers having hitherto unobserved and particularly useful physical properties. As used in this specification and the appended claims the words “fouling polymer” means a polyolefin polymer which adheres to the walls of the reactor in which it is produced to such an extent that commercial production of the polymer is hindered by reactor maintenance and cleansing requirements extraordinary with respect to those normally required for producing polymers which do not substantially adhere to the walls of the reactor in which they are produced, either in technique or frequency.
World Patents 96/11963 and 96/16996 describe solution processes for producing amorphous polyolefins. However, the processes therein set forth have the disadvantages of limitations on the viscosity and solids content, and include the use of one or more solvents, thus necessitating provisions for solvent recovery.
SUMMARY OF THE INVENTION
The present invention relates to a liquid pool process for polymerizin

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