Method for polymerization and copolymerization of alpha-olefin

Details Method for polymerization and copolymerization of alpha-olefin Method for polymerization and copolymerization of alpha-olefin

1999-12-06

2001-10-16

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...

C526S116000, C526S090000, C526S124500, C526S125300, C526S348000, C502S116000

Reexamination Certificate

active

06303715

ABSTRACT:

BACKGROUND OF INVENTION
The present invention relates to a method of producing olefin polymers or copolymers of high stereospecificity at a high rate of yields with a broad molecular weight distribution.
In general, polypropylene has characteristics of enhanced strength and heat-resistance at a broader molecular weight distribution and higher stereospecificity. As such, many attempts were made to broaden the molecular weight distribution and improve stereospecificity. Recently, Mitsui Petrochemical Industries, Ltd. and other well-known European companies have developed a polymerization method, by means of using specific silicon compounds, for polymers of high yields and stereospecificity (e.g., Korean Pat. Pub. No. 92-2488, U.S. Pat. No. 4,990,479, EP Laid-Open No. 350,170A, Chinese Pat. No. 1,040,379), as compared to those of the conventional methods. However, it was very difficult to produce polymers of the broad molecular weight and high MFR (Melt Flow Rate) due to the low hydrogen response. Further, in order to broaden the molecular weight distribution of the polymers, it was common to use a method of producing and then mixing olefin polymers of different molecular weight distributions from one another in a number of polymerization reactors. Yet, this method takes too much time and has disadvantages in that the products thereof are non-homogeneous.
In a recent report, from Mitsui Petrochemical of Japan(publication No. 93-665, of Korea Patent), a method has been proposed in which an olefin polymer with a wider distribution of molecular weights is produced by the use of two particular electron donors, from which homopolyolefins having the ratio of the melt flow rate (MFR) if greater than 31.6 are respectively polymerized in the same polymerization conditions. In this case, however, the catalyst's activity is reduced too low and the stereospecificity of polymer is too low for it to be commercially useful.
Meanwhile, many other techniques are known to produce polymers or copolymers of high stereospecificity by the use of solid complex titanium catalysts containing magnesium with electron donors, and also titanium and a halogen, as catalyst for polymerization or copolymerization of &agr;-olefin which contains more than three atoms of carbon (e.g. Japanese, Pts. Laid-Open Nos. S48-16986 and S48-16987, Ger. Pts. Laid-Open Nos. 2,153,520; 2,230,672; 2,230,728; 2,230,752; and 2,553,104)
These references reveal the use of mixture components of particular catalysts and the process for forming these catalysts. As is well known, the characteristics of these catalysts, containing solid complex titanium, vary from catalyst to catalyst, in accordance with the different mixtures of components, different combinations of processes for formation, and the different combinations of these conditions. Therefore, it is very difficult to predict what effects can be obtained from a catalyst produced under a given set of conditions. Often, a catalyst having undesirable effect is produced. It is also often true that such characteristics as the activity of the catalyst or the stereospecificity of the polymer do not turn out to be adequate even if the catalyst is made under proper conditions, if proper external electron donors are not used.
The solid complex titanium catalyst containing magnesium, titanium, and halogen is no exception. In polymerizing or copolymerizing &agr;-olefin containing more than three atoms of carbon, in the presence of hydrogen and with the use of a catalyst composed of titanium and an organometallic compound of metals belonging to Groups I through IV on the periodic table of elements, if a co-catalyst composed of titanium trichloride obtained by reducing titanium tetrachloride using metallic aluminum, hydrogen, or an organic aluminum compound is used, along with such electron donors as are known to restrain the formation of amorphous copolymer, the effects vary depending upon the electron donors used. The cause is accepted to be that the electron donors are not mere inert additives, rather, they combine with the magnesium and titanium compounds electronically and sterically, thereby fundamentally altering the structure of the solid complex catalyst.
SUMMARY OF INVENTION
In an embodiment, a method of producing olefin polymers and co-polymers of broad molecular weight distribution, to the extent of a high MFR, while maintaining high stereospecificity and activity of a catalyst is described.
In another embodiment, the present invention provides a method for producing a polypropylene and propylene copolymer adequate for use in production of film easily capable of being heat-sealed, transparent, and anti-blocking property, also adequate for impact resistance, fluidity and low temperature heat-sealable is described.
DETAILED DESCRIPTION OF INVENTION
The present invention provides a method for polymerizing or copolymerizing an &agr;-olefin using the catalyst system comprising:
(a) a solid complex titanium catalyst containing magnesium, a halogen-containing titanium compound, and, as internal electron donor, an ester polycarboxylate;
(b) an organometallic compound of a metal of Group I and III on the periodic table of elements;
(c) two of external electron donors comprising an external electron donor (1) and an external electron donor (2), wherein the ratio of the MFR (1) to the MFR (2) is 2~10, the MFR (1) being that of the homopolymer (1) obtained by using said external electron donor (1) with said solid complex titanium catalyst (a) and the organometallic compound (b), and the MFR (2) being that of the homopolymer (2) obtained by using said external electron donor (2) under the identical polymerization reaction conditions of said external electron donor (1), and wherein the NMR pentads of the homopolymer (1) and the homopolymer (2), respectively, are 95.5% or more.
The solid complex titanium catalyst (a) used for polymerization or copolymerization of an &agr;-olefin includes magnesium, a halogen-containing titanium compound, and, as internal electron donor, ester polycarboxylate. The solid complex titanium catalyst used in the present invention has an excellent level of catalytic activity, compared with existing titanium catalysts, and is capable of creating a polymer having a broad molecular weight distribution and a high stereospecificity. It has a halogen/titanium molar ratio more than about 4; it is also a solid complex with practically no titanium compound separating out when washed in hexane at room temperature. The chemical construction of this solid complex is not known but it is presumed that the atoms of magnesium, as well as those of titanium, are firmly linked by halogen. In an embodiment of the solid complex titanium used in the present invention, the halogen/titanium molar ratio is more than about 5, preferably more than about 8; a magnesium/titanium molar ratio over about 3, further preferably from about 5 to about 50, the electron donor/titanium molar ratio about 0.2 to about 6, preferably about 0.4 to about 3, even more preferably about 0.8 to about 2. The specific surface area is more than 10 m
2
/g, preferably more than about 50 m
2
/g, more preferably more than about 100 m
2
/g. The X-ray spectrum of the solid complex titanium catalyst preferably shows either amorphous characteristics in disregard of the starting magnesium, or characteristics more amorphous than ordinary magnesium dihalide on the market.
The solid complex titanium catalyst may be produced by many methods. As the most widely practiced method, contacting a non-reductive magnesium compound with a titanium compound which contains halogen(s), and treating the product thereof, if necessary, with an electron donor, and these methods can all be used in the present invention also. Some of these methods are revealed in Ger. Pts. Laid-Open Nos. 2,230,672; 2,504,036; 2,553,104; and 2,605,922; and Japanese Pat. Laid-Open Nos. S51-28189; S51-136625; and 52-87486. The conventional method for producing the solid complex titanium compound, beginning from a liquid magnesium solution and containing an electro

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