| Blow molding polyethylene resins -> Monitor Keywords |
|
|
  Blow molding polyethylene resinsThe Patent Description & Claims data below is from USPTO Patent Application 20070027276. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND [0001] 1. Field of Inventions [0002] This patent is related to polyethylene resins and continuous fluidized-bed gas-phase polymerization processes for making polyethylene resins. [0003] 2. Description of Related Art [0004] As evidenced by the many earlier patents in the field of fluidized-bed gas phase polymerization, which include some of the patents listed on the face of this patent, the manufacture of polyethylene resins in a fluidized-bed gas phase process has been the subject of a great deal of development effort and expense. [0005] One of the problems in using a fluidized-bed gas phase process to form polyethylene resins is making a resin with desirable properties, particularly properties appropriate for blow molding purposes, while still having a high productivity and avoiding production problems, e.g., sheeting and the like. Therefore, it would be desirable to obtain a resin product with desirable properties, e.g., sufficiently high Environmental Stress Crack Resistance (ESCR) and proper die swell, while also achieving high catalyst productivities, using a fluidized-bed gas phase process. [0006] U.S. Pat. No. 5,166,279 refers to processes for the gas phase co-polymerization of ethylene, in which polyethylene resins are formed. However, the processes disclosed in that patent are said to provide products with reduced die swell, in contrast with the processes herein, which provide polyethylene resins with increased die swell. Also, the disclosed ESCR levels are low in relation to the densities of the resins. That is, the ESCR Index (described below) is below 1.0. Further still, the disclosed catalyst productivities for low reactor temperatures are low. [0007] Processes for gas phase polymerization of ethylene are disclosed in WO 01/77191 but neither ESCR nor die swell is discussed. Further, the processes involve low productivities. SUMMARY [0008] Disclosed herein are various processes, including continuous fluidized-bed gas-phase polymerization processes for making a high strength, high density polyethylene copolymer, comprising (including): contacting monomers that include ethylene and optionally at least one non-ethylene monomer with fluidized catalyst particles in a gas phase in the presence of hydrogen gas at an ethylene partial pressure of 100 psi or more and a polymerization temperature of 105.degree. C. or less to produce a polyethylene copolymer having a density of 0.945 g/cc or more and an ESCR Index of 1.0 or more wherein the catalyst particles are prepared at an activation temperature of 700.degree. C. or less, and include silica, chromium, and titanium. [0009] Also disclosed herein are continuous fluidized-bed gas-phase polymerization processes for making a high strength, high density polyethylene copolymer, comprising: contacting monomers that include ethylene and optionally at least one non-ethylene monomer with fluidized catalyst particles in a gas phase in the presence of hydrogen gas at an ethylene partial pressure of 100 psi or more and a polymerization temperature of 105.degree. C. or less to produce a polyethylene copolymer having a density of 0.945 g/cc or more, an ESCR of 45 hours (10% Igepal) or more, and a Die Swell of from 80% to 100%, wherein the catalyst particles are prepared at an activation temperature of 700.degree. C. or less, and include silica, chromium, and titanium. [0010] Also disclosed is a continuous gas-phase polymerization process for making a high strength, high density polyethylene copolymer, comprising: contacting monomers that include ethylene and optionally at least one non-ethylene olefin with fluidized catalyst particles in a gas-phase fluidized-bed reactor in the presence of hydrogen gas at an ethylene partial pressure of 100 psi or more and a polymerization temperature of 105.degree. C. or less to produce a polyethylene copolymer having a density of from 0.945 to 0.960 g/cc and an ESCR Index of 1.0 or more, wherein: [0011] (a) the catalyst particles include a silica support that is porous and has a surface area of less than 400 square meters per gram; [0012] (b) the catalyst particles have been prepared by contacting the silica support with a chromium compound in a vessel; raising the internal temperature of the vessel containing the dried particles and dry air to a final activation temperature of 650.degree. C. or below; maintaining the activation temperature for a period of from 4 to 8 hours to form activated catalyst particles; lowering the internal temperature of the vessel containing the activated catalyst particles; removing air from the vessel using dry nitrogen; and [0013] (c) the polyethylene resin is formed at a polymerization temperature of 105.degree. C. or less; [0014] (d) the polyethylene resin is formed with a bulk density of 20 lb/ft3 or more; [0015] (e) the polyethylene resin has an ESCR Index of 1.0 or more; [0016] (f) the polyethylene resin has a density of from 0.945 to 0.960 g/cc; [0017] (g) the polyethylene resin has a Molecular Weight Distribution of from 15 to 30. BRIEF DESCRIPTION OF DRAWINGS [0018] FIG. 1 is a flow diagram of a process for making polyethylene resin. DETAILED DESCRIPTION [0019] A detailed description now follows, for purposes of enabling a person having ordinary skill in the art of making polyethylene to make and use the claimed invention, without undue experimentation. Various terms as used herein are defined below. To the extent a term used in a claim is not defined below, or elsewhere herein, it is given the broadest definition persons in the pertinent art have given that term based on any definition or usage of the term in one or more printed publications or issued patents, including any dictionary definitions. [0020] In specific embodiments, some of which are described below, polyethylene resins are obtained by particular polymerization processes in which specific ingredients and processing conditions are used. For example, a polyethylene resin having improved properties (e.g., high Environmental Stress Crack Resistance (ESCR) and desirable Die Swell) can be obtained by directly contacting monomers that include ethylene and other comonomers (e.g., hexene) in a fluidized bed reactor, in the presence of oxygen and hydrogen, at a high ethylene partial pressure (e.g., 100 psi and preferably higher) using a low polymerization temperature (e.g., less than 105.degree. C. and preferably less than 100.degree. C.) with a particular catalyst that (a) includes titanium together with a low amount of chromium (less than 1.0 wt% and preferably 0.50 wt % or lower), (b) is supported by a porous support particle that consists essentially of silica, (c) has a low surface area (less than 400 square meters per gram) and (d) is activated in a specific way that includes careful control of activation temperature, which includes using an activation temperature within a particular range, e.g., greater than 450.degree. C. but less than 700.degree. C. or 650.degree. C. and preferably a narrower range, as specified below. A polyethylene resin can be produced having superior properties, particularly a polyethylene useful for blow molding purposes. At least one of the superior properties is an ESCR Index that is substantially higher than when certain elements are not utilized, as demonstrated in the examples below. Furthermore, the polyethylene resin is produced at high productivities, e.g., 5000 lb/lb and greater (i.e., pounds of polymer per pound of catalyst). Continue reading... Full patent description for Blow molding polyethylene resins Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Blow molding polyethylene resins patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Blow molding polyethylene resins or other areas of interest. ### Previous Patent Application: Self limiting catalyst composition and propylene polymerization process Next Patent Application: Method of preparing phosphonium compound for cyclic olefin polymerization Industry Class: Synthetic resins or natural rubbers -- part of the class 520 series ### FreshPatents.com Support Thank you for viewing the Blow molding polyethylene resins patent info. IP-related news and info Results in 2.50949 seconds Other interesting Feshpatents.com categories: Computers: Graphics , I/O , Processors , Dyn. Storage , Static Storage , Printers |
||
