Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Plural component system comprising a - group i to iv metal...
Reexamination Certificate
2001-03-30
2003-11-11
Choi, Ling-Siu (Department: 1713)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
C502S103000, C502S115000, C502S116000, C502S125000, C526S125100, C526S124300, C526S901000, C526S908000, C526S909000, C526S348000
Reexamination Certificate
active
06645901
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a prepolymerization catalyst for use in a gas phase polymerization of olefins. More particularly, the invention relates to a prepolymerization catalyst for use in a gas phase polymerization of olefins showing a high activity in gas phase polymerization, not causing a formation of aggregates and coarse polymer particles markedly during the prepolymerization, having high bulk density and excellent fluidity, not causing an entraining of the prepolymerization catalyst and a product powder out of a fluidized bed markedly and nearly completely free from a formation of polymer aggregates at the time of the gas phase polymerization, and capable of giving an olefin polymer low in the content of cold xylene-soluble fraction, and a process for producing the same.
BACKGROUND OF THE INVENTION
Since olefin polymers have high mechanical property such as strength, good appearance such as transparency, and excellent moldability or handling property such as film-forming property, olefin polymers are extensively used as a material for films and molded articles. Among the olefin polymers, polyethylenes such as ethylene homopolymers and linear low-density polyethylenes (LLDPE), which are ethylene-&agr;-olefin copolymers, are especially suitable for use as film-forming materials.
High-activity catalysts for production of olefin polymers have a very high industrial value, because they can be used in the gas phase olefin polymerization process in which the de-ashing step is simplified. However, when an olefin is polymerized by a gas phase polymerization process using a high-activity catalyst, the polymerization is accompanied by generation of a large quantity of heat, and thereby fusion and aggregation of the resulting olefin polymer may take place and it may become difficult to continue the polymerization of olefin or produce olefin polymer.
As a method for preventing the above-mentioned aggregation of polymer generated in olefin polymerization, there is known a method of using, as a catalyst for gas phase polymerization of olefin, a prepolymerization catalyst obtained by prepolymerizing ethylene and/or an &agr;-olefin on an olefin-polymerizing catalyst.
For instance, JP-A-59-30806, JP-A-7-196720 and JP-A-8-337611 disclose a prepolymerization catalyst which is a powder of an &agr;-olefin prepolymer having such a particle dimension distribution that the mass-average diameter (Dm) is 80-300 &mgr;m and the ratio of number-average diameter (Dn) to the mass-average diameter (Dm) is smaller than or equal to 3, and also disclose that olefin polymers such as ethylene homopolymer or ethylene-butene-1 copolymer can be obtained by continuously effecting an olefin polymerization by using the above-mentioned powdery prepolymer in a gas phase polymerization.
SUMMARY OF THE INVENTION
However, if a catalyst having higher activity such as those described in JP-A-11-322833 is subjected to a prepolymerization in a suspension polymerization system, in some cases the prepolymerization catalyst is not smoothly drawn out of the suspension polymerization reactor because coarse granules or aggregates of polymer are formed and fluidity of the prepolymerization catalyst is extremely insufficient due to its low bulk density. Furthermore, there was a problem that when fluidity of the prepolymerization catalyst is insufficient, the quantity of prepolymerization catalyst fed cannot be kept constant at the time of the feeding of the prepolymerization catalyst to a gas phase fluidized bed type gas phase polymerization reactor together with a gas stream, which causes fluctuation of olefin polymerization temperature or formation of olefin polymer aggregates in the gas phase fluidized bed type gas phase polymerization reactor and thereby makes it difficult to polymerize the olefin steadily.
Under the above-mentioned circumstances, it is desired to develop a prepolymerization catalyst for use in the gas phase polymerization of olefins high in the activity in gas phase polymerization, not causing formation of aggregates and coarse granules markedly at the time of prepolymerization, high in bulk density, excellent in fluidity, causing no remarkable entraining of the prepolymerization catalyst and the resulting powdery olefin polymer out of the fluidized bed at the time of gas phase polymerization, nearly completely free from formation of polymer aggregates, and giving an olefin polymer low in the content of cold xylene-soluble fraction.
It is an object of the present invention to provide a prepolymerization catalyst for use in the gas phase polymerization of olefins high in the activity in gas phase polymerization, not causing formation of aggregates and coarse granules markedly at the time of prepolymerization, high in bulk density, excellent in fluidity, causing no remarkable entraining of the prepolymerization catalyst and the resulting powdery olefin polymer out of the fluidized bed at the time of gas phase polymerization, nearly completely free from formation of polymer aggregates, and giving an olefin polymer low in the content of cold xylene-soluble fraction, and a process for producing the same.
In view of the above, the present inventors have conducted extensive studies to find that the problem mentioned above can be solved by a prepolymerization catalyst comprising a solid catalyst component having a specified weight-average particle diameter, an organoaluminum compound and a prepolymer of ethylene and/or at least one &agr;-olefin and having a specified aluminum-titanium ratio, a specified weight ratio of prepolymerization catalyst/solid catalyst component, a specified volatile material content and a specified intrinsic viscosity. Based on this finding, the present invention has been accomplished.
Thus, the present invention relates to a prepolymerization catalyst for use in a gas phase polymerization of olefins which comprises (A) a solid catalyst component comprising magnesium, halogen, titanium and an electron donor and having a weight-average particle diameter of 15-45 &mgr;m, (B) at least one organoaluminum compound and (C) a prepolymer of an ethylene and/or at least one &agr;-olefin, wherein the molar ratio of aluminum to titanium (Al/Ti ratio) contained in said prepolymerization catalyst is 3 to 11 (mol/mol), the weight ratio of the prepolymerization catalyst to the solid catalyst component (prepolymerization catalyst/solid catalyst component ratio) is 2 to 35 (g/g), the content of volatile materials (VM) in the prepolymerization catalyst is 2.0% by weight or less, and the intrinsic viscosity [&eegr;] of the prepolymerization catalyst measured in tetralin at 135° C. is 2.0 dl/g or less, and a process for a production of the prepolymerization catalyst.
The present invention further relates to a process for producing an olefin polymer which comprises polymerizing olefins by means of a gas phase fluidized bed using the above-mentioned prepolymerization catalyst for gas phase polymerization.
Next, details of the present invention will be described below.
DETAILED DESCRIPTION OF THE INVENTION
As used in the present invention, the term “polymerization” means not only a homopolymerization, but also inclusively means a copolymerization; and the term “polymer” means not only a homopolymer but also means a copolymer inclusively.
As used in the present invention, the term “olefin” means an olefin having 2 or more carbon atoms which include, for instance, ethylene, propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, decene-1,3-methylpentene-1,4-methylpentene-1, and the like, and it means preferably ethylene, propylene, butene-1, hexene-1, octene-1 and 4-methylpentene-1, and further preferably ethylene, propylene, butene-1 and hexene-1.
The term “gas phase polymerization” used in the present invention means a polymerization process used for polymerizing olefins in a gas phase. It is known that a gas phase polymerization process requires only a smaller investment and a lower energy cost as compared with other polymer-producing processes such as a suspension
Goto Tomoaki
Kumamoto Shin-ichi
Wakamatsu Kazuki
Choi Ling-Siu
Sumitomo Chemical Company Limited
LandOfFree
Prepolymerization catalyst for use in gas phase... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Prepolymerization catalyst for use in gas phase..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Prepolymerization catalyst for use in gas phase... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3129850