Process that produces polymers

Details Process that produces polymers Process that produces polymers

2001-01-31

2003-11-04

Choi, Ling-Siu (Department: 1713)

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

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S352000, C526S348000, C526S104000, C526S106000, C526S130000, C525S120000

Reexamination Certificate

active

06642324

ABSTRACT:

FIELD OF THE INVENTION
This invention is related to the field of processes that polymerize ethylene, or that polymerize ethylene and at least one other olefin, to produce a polymer.
BACKGROUND OF THE INVENTION
There are many processes that polymerize ethylene, or that polymerize ethylene and at least one other olefin, to produce a polymer. There are also many manufacturing processes that use these types of polymers to produce useful items. One of these manufacturing processes is called blow molding.
In general, blow molding is useful for producing hollow plastic products. A principle advantage of blow molding is its ability to produce hollow shapes without having to join two or more separately molded parts.
In order to produce a good quality blow molded product, one needs to start with a good quality polymer. However, producing such good quality polymers is difficult. It has been especially difficult to produce a good quality polymer that has a high environmental stress crack resistance (ESCR) and that is useful for blow molding applications.
Therefore, the inventors provide this invention so that such good quality polymers with high ESCR's are more readily obtainable, and readily useable in blow molding applications.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a process to polymerize ethylene, or ethylene and at least one other olefin to produce a polymer.
It is also an object of this invention to provide said polymer.
In accordance with this invention a process is provided. The process comprises (or optionally “consists essentially of”, or “consists of”) polymerizing ethylene, or polymerizing ethylene and at least one other olefin, to produce a polymer,
wherein said polymerizing is conducted in a polymerization zone, and
wherein said polymerizing is conducted using a catalyst and a cocatalyst, and
wherein said catalyst comprises chromium on a support, and
wherein the amount of said chromium on said support is from about 0.5 to 5 weight percent, and
wherein said support comprises silica, in major part, and
wherein the amount of titanium in said support is greater than about 3.5 to about 10 weight percent based on the weight of said support, and
wherein said support has a surface area from about 400 to about 800 square meters per gram, and
wherein said support has a pore volume from about 1.8 to about 4 cubic centimeters per gram, and
wherein said catalyst has been activated at a temperature in the range of about 600° F. to about 1100° F. in the presence of an oxidizing ambient, and
wherein said cocatalyst is an organoboron compound.
In accordance with this invention a polymer comprising the following properties: a density from about 0.94 to about 0.96, a high load melt index from about 5 to about 45 g/10 min., a shear ratio (high load melt index/melt index) from about 150 to about 400, a heterogeneity index from about 15 to about 55, an ESCR condition A greater than about 1000 hours, and ESCR Condition B greater than about 200 hours, a normalized die swell from about 0.8 to about 1.1, a weight swell from about 300 to about 500 percent, and an onset of melt fracture greater than about 2000 sec
−1
.
These and other objects will become more apparent with the following.
The terms “comprise”, “comprises” and “comprising” are open-ended and do not exclude the presence of other steps, elements, or materials that are not specifically mentioned in this specification.
The phrases “consists of” and “consisting of” are closed ended and do exclude the presence of other steps, elements, or materials that are not specifically mentioned in this specification, however, they do not exclude impurities normally associated with the elements and materials used.
The phrases “consists essentially of” and “consisting essentially of” do not exclude the presence of other steps, elements, or materials that are not specifically mentioned in this specification, as along as such steps, elements, or materials, do not affect the basic and novel characteristics of the invention, additionally, they do not exclude impurities normally associated with the elements and materials used.
The previous terms and phrases are intended for use in areas outside of U.S. jurisdiction. Within the U.S. jurisdiction the above terms and phrases are to be applied as they are construed by U.S. courts and the U.S. Patent Officeu.
DETAILED DESCRIPTION OF THE INVENTION
This polymerization can be carried out in any manner known in the art such as gas phase, solution or slurry polymerization conditions. A stirred reactor can be utilized for a batch process, or the reaction can be carried out continuously in a loop reactor.
This polymerization is conducted in a polymerization zone. It is preferred to conduct this polymerization in a loop reactor. It is more preferred when said polymerization is conducted in a loop reactor under slurry polymerization conditions. Currently, the preferred diluent for slurry polymerization is isobutane.
Loop reactors are known in the art, see, for example, U.S. Pat. Nos. 3,248,179; 4,424,341; 4,501,855; and 4,613,484; the entire disclosures of which are hereby incorporated by reference. Especially preferred processes are disclosed in U.S. Pat. Nos. 4,589,957; 4,737,280; 5,597,892; and 5,575,979 the entire disclosures of which are also hereby incorporated by reference.
A preferred polymerization technique is that which is referred to as a particle form, or slurry process, wherein the temperature is kept below the temperature at which polymer swells and fouls the reactor. Such polymerization techniques are well known in the art and are disclosed, for example, in Norwood, U.S. Pat. No. 3,248,179, the disclosure of which is hereby incorporated by reference.
Two preferred polymerization methods for the slurry process are those employing a loop reactor of the type disclosed in Norwood and those utilizing a plurality of stirred reactors either in series, parallel or combinations thereof wherein the reaction conditions are different in the different reactors.
The diluent, before it enters the reactor, comprises isobutane. Additionally, before the diluent enters the reactor, the majority of said diluent is isobutane. It is preferred when the diluent contains 60-100, more preferably, 70-100, and most preferably 80-100 weight percent isobutane based on the weight of the diluent before it enters the reactor.
The polymerization is conducted at a temperature from about 190° F. to about 230° F. However, it is preferred when said polymerizing is conducted at a temperature from about 195° F. to about 225° F. and it even more preferred when said polymerizing is conducted at a temperature from 200° F. to 220° F. At temperatures below about 190° F. the efficiency of the catalyst and the reactor is adversely affected. At temperatures above about 230° F. the reactor could foul due to the swelling of the polymer.
The pressure that the polymerization is conducted at is in the range of about 400 psia to about 800 psia, preferably about 500 psia to about 700 psia. The catalyst used in this invention comprises chromium on a support, preferably in the form of chromium oxide on a support. The amount of chromium on said support is in the range of about 0.5 to about 5 weight percent, preferably about 1 to about 4 weight percent, and most preferably from 1.5 to 3 weight percent, where such weight percents are based on the weight of the support.
The support comprises silica and titania. Additionally, such support has silica, as its major component by weight, and titania, as its minor component by weight. It is most preferred when said support consists essentially of silica and titania, with little, if any, impurities. It is even more preferred when the silica and titania are cogelled.
It is preferred when the amount of titanium in the support is from about 3.5 to about 10 weight percent, preferably about 4 to about 8 percent, and most preferably from 4 to 6 weight percent, where said weight percents are based on the weight of the support. When the amount of titanium is less than about 3.5 weight percen

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