Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-09-01
2001-04-10
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S124700, C526S127000, C526S137000, C526S155000, C526S348600, C526S352000, C502S118000, C502S125000, C502S128000, C502S129000, C502S132000, C502S133000
Reexamination Certificate
active
06214950
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an olefin polymerization catalyst and a process for the preparation of a polyolefin using the catalyst component. More specifically, the present invention relates to an olefin polymerization catalyst which can control the molecular weight distribution more easily than the conventional known process, is less deteriorated in its efficiency even after a long-term storage, is free from the deposition of scales in a reactor even after long-term use and provides a polyolefin having excellent properties with good powder properties owing to its considerably high activity; and to a process for the preparation of a polyolefin by using the catalyst component.
BACKGROUND OF THE INVENTION
For a polyolefin, particularly, an ethylene polymer, its molecular weight distribution is a considerably important property which gives an influence on both the processability of its molten substance and final mechanical properties. The application of a polyolefin therefore changes depending on its molecular weight distribution. There is a tendency that polyolefins of a wider molecular weight distribution are used for molded articles such as pipe, those of a medium distribution are used for fibers, tapes and the like, and those of a narrow distribution are used for injection-molded articles such as bottle caps, buckets and the like. In general, the molecular weight distribution of the ethylene-polymer largely depends on the properties of a solid catalyst component employed upon polymerization and it is necessary to choose a proper solid catalyst component according to the intended molecular weight distribution. As a catalyst permitting a wide molecular weight distribution, known are catalysts comprising a large variety of transition metal compounds in combination and solid catalysts having a specific surface area or porosity, as described, for example, in JP-B-52-37037 and JP-B-53-8588 (“JP-B” as used herein means an examined published Japanese patent publication) and JP-A-6-220117 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”). For a narrow molecular weight distribution, on the other hand, a number of processes using a specific ether compound upon synthesis of a solid catalyst or upon polymerization are proposed, as described, for example, in JP-A-2-289604, JP-A-3-294302 and JP-A-3-294310. The above catalysts each serves to provide the intended molecular distribution, but has an unsatisfactory activity per transition metal because transition metals other than a titanium compound are used or an electron donor, such as an ether, which becomes a catalytic poison is added upon synthesis of a solid catalyst or upon polymerization. They are also insufficient from the viewpoint of the powder properties such as particle size and bulk density of the polymer. A solid catalyst component which contains an organomagnesium compound, Si—H bond-containing chlorosilane compound, alcohol and titanium compound as essential components is disclosed in JP-B-2-42366 in which, however, no suggestion is included concerning the controlling method of the molecular weight distribution of a polymer. In JP-B-5-7405, disclosed is a process for obtaining a polymer having a wide molecular weight distribution by using, as an olefin polymerization catalyst composed of a specific magnesium/titanium component, a catalyst in which a molar ratio of an alkoxy group/titanium in a reaction product is lower than a certain value. In the above process, however, activity per titanium metal is insufficient. In U.S. Pat. Nos. 4,159,965 and 4,471,066, disclosed is an olefin polymerization catalyst which can provide polymers having a molecular weight distribution over a wide range from narrow to wide molecular weight distribution. In this catalyst, the molecular weight distribution is controlled by using different transition metal components in combination. The activity per transition metal is however not enough for obtaining a polymer having a wide molecular weight distribution. Furthermore, upon preparation of a polyolefin, it is requested in recent years to properly prepare catalysts capable of providing different molecular weight distributions by using solid catalyst components prepared from the same raw materials and by the same preparation process with a view to reducing the manufacturing cost. Therefore, the above-described process using different transition metals in combination is disadvantageous from the viewpoint of the manufacturing cost.
As a process for preparing a polyolefin by polymerizing or copolymerizing an olefin in the presence of such a catalyst, commonly employed is so-called slurry polymerization in which polymerization is effected with a solid catalyst being suspended in a solution. In the case of slurry polymerization, however, a low-molecular weight polymer by-produced upon the polymerization reaction easily dissolves in a polymerization solvent and deposits on the wall of a reactor, which reduces the heat transfer coefficient and makes it difficult to stably carry out long-term continuous operation. Furthermore, the conventional solid catalyst component has a problem in its storage stability, more specifically, lowering in the polymerization activity when stored for a long period of time after preparation. Thus, the conventional solid catalyst component has a difficulty to be used in long-term continuous stable operation.
SUMMARY OF THE INVENTION
Taking into account the above-described problems in conventional art, the present invention has been completed.
The present invention relates to a technique to prepare catalysts each of which provides a different molecular weight distribution of a polymer product, respectively, using solid catalyst components prepared from raw materials and by a preparation process as same as possible.
The present invention further relates to provide an olefin polymerization catalyst, which is less deteriorated in its activity even after long-term storage, is free from the deposition of a polymer on the walls of a reactor upon slurry polymerization, and permits a long-term continuous stable operation, and provides a polyolefin with good powder properties owing to its considerably high activity, and to provide a process for the preparation of a polyolefin by using the catalyst component.
Other objects and effects of the present invention will become apparent from the following description.
The present inventors have conducted extensive research on a catalyst taking into account the above-described problems. As a result, it has been found that upon preparation of a solid catalyst component for olefin polymerization, which contains as essential components an organomagnesium compound, Si—H bond-containing chlorosilane compound, alcohol and titanium compound, polyolefins different in molecular weight distribution can be prepared easily by adjusting the alkoxy group/titanium molar ratio and the alkoxy group/magnesium molar ratio in the solid catalyst to 2.4 or lower and 0.15 to lower, respectively. It has also been found that by dispersing the solid catalyst component in an inert solvent to obtain a slurry and, upon dispersion, adjusting both the chlorine ion concentration and aluminum ion concentration in the supernatant of the slurry to 5 mmol/liter or lower, the solid catalyst component has excellent storage stability, is free from the deposition of the polymer onto the wall of a reactor even after a long-term continuous operation and provides the polymer with good powder properties owing to its considerably high activity. The present invention is based on these findings.
That is, the above-described objectives of the present invention have been achieved by providing:
an olefin polymerization catalyst comprising (A) a solid catalyst component and (B) an organometallic compound component, wherein the solid catalyst component (A) is prepared by a process comprising the steps of reacting:
(A-1) a solid obtained by reacting:
(i) 1 mol of an organomagnesium component which is soluble in a hydrocarbon solvent and w
Harlan R.
Pennie & Edmonds LLP
Wu David W.
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