Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-04-03
2003-02-11
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...
C526S352000, C526S095000, C526S089000, C502S232000, C502S240000, C502S254000, C502S152000, C502S104000
Reexamination Certificate
active
06518375
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a catalyst for the production of an ethylene polymer using a trivalent alkyl chromium compound and a process for producing an ethylene polymer using the catalyst. More particularly, the invention relates to a catalyst for the production of an ethylene polymer using a trivalent alkyl chromium compound, a catalyst for the production of an ethylene polymer using a trivalent alkyl chromium compound and a tetravalent alkyl chromium compound and a process for producing an ethylene polymer using those catalysts.
BACKGROUND OF THE INVENTION
It is well known that a catalyst for the production of an ethylene polymer obtained by supporting an organochromium compound on an inorganic oxide solid has inherent performances such that it is possible to adjust a molecular weight with hydrogen and an ethylene polymer obtained has a narrow molecular weight distribution, as being different from a so-called Phillips catalyst obtained by supporting a chromium compound on an inorganic oxide solid and then conducting activation in a non-reducing atmosphere such as air or oxygen.
Examples of such a catalyst include a so-called chromocene catalyst comprising bis(cyclopentadienyl)chromium(II) supported on silica or the like as disclosed in JP-A-50-68985, U.S. Pat. No. 3,879,368, U.S. Pat. No. 3,687,920, JP-B-50-68985, JP-B-52-31226, Canadian Patent 1,087,595, JP-B-58-25323, U.S. Pat. No. 4,101,445, U.S. Pat. No. 4,424,139 and Published Japanese Translation of International Patent Application Hei. 8-512339; a catalyst comprising dicumene chromium(0) supported on silica or the like as disclosed in JP-B-47-16647 and U.S. Pat. No. 4,364,841; a catalyst comprising bis(indenyl)chromium(II) or bis(fluorenyl)chromium(II) supported on silica or the like as disclosed in U.S. Pat. No. 4,015,059; a catalyst comprising (pentamethylcyclopentadienyl)(2-methylpentadienyl)chromium(II) supported on silica or the like as disclosed in U.S. Pat. No. 5,169,817; a catalyst comprising &pgr;-allyl chromium(II) supported on silica or the like as disclosed in JP-B-47-13002 and JP-B-47-26429; a catalyst comprising tetraneopentyl chromium(IV) supported on silica or the like as disclosed in U.S. Pat. No. 3,798,250; a catalyst comprising tetrakis(bicycloheptyl) chromium(IV) supported on silica or the like as disclosed in JP-A-47-16590; and a catalyst comprising octakis(alkylsilyl) tetrachromium(II) multinuclear complex supported on silica or the like as disclosed in U.S. Pat. No. 4,668,808. These catalysts use organochromium compounds in which the valency of the chromium atom is 0, 2 or 4, and there are only a few cases to use a trivalent organochromium compound.
Example of an ethylene polymer obtained by supporting a trivalent organochromium compound on an inorganic oxide solid is a catalyst comprising tris(bicycloheptyl)chromium(III) supported on silica as disclosed in, for example, JP-A-47-17753. In the case of this catalyst, tris(bicycloheptyl)chromium(III) which is a trivalent organochromium compound is unstable to heat and/or light and is liable to decompose. As a result, even if the compound is supported on silica to form a catalyst, the compound causes deterioration of activity with the passage of time and the catalyst cannot be stored. Thus it is difficult to obtain a catalyst having stable quality and an ethylene polymer. Further, a catalyst comprising a component comprising cyclopentadienyl chromium(III) hydrocarbyl compound supported on an inorganic carrier such as silica, and an alkyl aluminum compound is known as disclosed in U.S. Pat. No. 5,418,200, JP-A-7-502783, WO 96-27621 and WO 96-23006. In the case of this catalyst, deterioration with the passage of time is difficult to cause, but activity per catalyst and activity per chromium atom are very low. Thus, such a catalyst is poor economical property and is not suitable for industrial use. Further, since catalyst residue remains in the polymer obtained in a large amount, a product colors and deterioration is accelerated, thus giving adverse influence. Furthermore, since this catalyst is difficult to catalyze copolymerization with &agr;-olefin such as 1-butene and 1-hexene, it is difficult to control a density of an ethylene polymer. Thus, the catalyst has a great disadvantage that only a product having a very limited high density can be produced. As described above, there have been practical problems in the catalyst for the production of an ethylene polymer, obtained by supporting the trivalent organochromium compound on an inorganic oxide solid.
Therefore, a first object of the present invention is to provide a catalyst for the production of an ethylene polymer, which overcomes the problems of the catalyst using the trivalent organochromium compound, does not cause deterioration with the passage of time, is stable to heat and light, improves its activity, and is capable of catalyze copolymerization with &agr;-olefin, and a process for producing an ethylene polymer efficiently using the catalyst.
The ethylene polymer is generally widely used as a resin material for various molded articles, but the properties required in the ethylene polymer vary depending on the molding method and the purpose of use. For example, a product molded by an injection molding has a relatively low molecular weight, and use of a polymer having a narrow molecular weight distribution is suitable. On the other hand, a product molded by a blow molding or a film molding has a relatively high molecular weight, and use of a polymer having a broad molecular weight distribution is suitable. It has conventionally been known that an ethylene polymer having a broad molecular weight distribution suitable for a blow molding, a film molding and the like can be obtained using a Phillips catalyst prepared by supporting a chromium compound such as chromium trioxide, chromium acetate or tris(acetylacetonato)chromium on an inorganic oxide solid such as silica and activating the same in oxygen gas or air.
Further, an ethylene polymer having a broad molecular weight distribution suitable for a blow molding, a film molding and the like can also be obtained using a catalyst (silyl chromate catalyst) prepared by supporting bis (triphenylsilyl)chromate on an inorganic oxide solid such as silica and treating the same with an organoaluminum as disclosed in, for example, JP-B-44-2996, JP-B-44-3827 and JP-B-47-1766.
Thus, chromium catalysts have conventionally been used industrially as a catalyst for producing an ethylene polymer having high molecular weight, which is suitable for a blow molding or a film molding.
However, in the use of those catalysts, even if polymerization temperature is elevated as high as possible or a chain transfer agent such as hydrogen is used, in a process of a slurry polymerization in which the ethylene polymer does not dissolve in a polymerization solvent or a gas phase polymerization, it is still difficult to produce an ethylene polymer having low molecular weight suitable for an injection molding.
Improvement methods of Phillips catalyst for obtaining an ethylene polymer having low molecular weight have been proposed as disclosed in, for example, U.S. Pat. No. 4,248,735, U.S. Pat. No. 4,177,162, U.S. Pat. No. 4,151,122, U.S. Pat. No. 4,312,967, U.S. Pat. No. 4,397,765, U.S. Pat. No. 4,364,839 and U.S. Pat. No. 4,364,842. However, it cannot say that the molecular weigh can sufficiently be decreased by those methods. Thus, there has been a limit for the molecular weight of an ethylene polymer that can be produced by those catalysts.
On the other hand, according to the use of a chromocene catalyst comprising bis(cyclopentadienyl)chromium(II) supported on silica or the like as described before, an ethylene polymer having a very wide molecular weight range of from high molecular weight to low molecular weight can be obtained by using hydrogen as a chain transfer agent. However, use of the chromocene catalyst has a great disadvantage that since &agr;-olefin such as 1-butene or 1-hexene is not copolymerized, it is impossible to control a densi
Ikeda Haruhiko
Monoi Takashi
Torigoe Hidenobu
Choi Ling-Siu
Japan Polyolefins Co., Ltd.
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