Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1994-01-18
2001-07-03
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S160000, C526S348200, C526S348300, C526S348400, C526S348500, C526S348600, C526S916000, C428S035500, C428S035700, C428S036920, C428S220000
Reexamination Certificate
active
06255425
ABSTRACT:
BACKGROUND OF THE INVENTION
(i) Field of the Invention
The present invention relates to a syndiotactic polypropylene copolymer. More specifically, the present invention relates to a copolymer having high syndiotacticity of propylene and another olefin.
The present invention further relates to novel extruded polypropylene articles. Specifically, the present invention is concerned with extruded articles, especially films and sheets and blown films, of a high-syndiotacticity propylene homopolymer or a high-syndiotacticity copolymer of propylene and another olefin.
(ii) Description of the Prior Art
A syndiotactic polypropylene has been known for a long time. Such a conventional polypropylene can be prepared by a low temperature polymerization in the presence of a conventional catalyst comprising a vanadium compound, an ether and an organic aluminum, but this kind of polypropylene is poor in syndiotacticity and scarcely exhibits characteristics of syndiotactic polypropylene. In addition, a copolymer of an &agr;-olefin and propylene is hardly considered to be a crystalline polypropylene. On the other hand, a polypropylene having good tacticity, i.e., a syndiotactic pentad fraction of more than 0.7 as measured by
13
C-NMR has been discovered for the first time by J. A. Ewen et al. which can be obtained by polymerizing propylene in the presence of a catalyst comprising a transition metal (Hf and Zr) compound having an asymmetric ligand and aluminoxane (J. Am. Chem. Soc., 110, 6255-6256, 1988).
The above-mentioned method which has been suggested by J. A. Ewen et al. exhibits high catalytic activity per unit amount of the transition metal, and can provide a polymer having a high tacticity and relatively properly balanced physical properties, but molded articles of this kind of polymer are inconveniently poor in transparency and unsatisfactory in impact resistance.
Isotactic polypropylene has a wide range of utility as molded or otherwise formed articles. As a major application field, it can be used for the production of extruded articles such as sheets and blown films. These sheets and blown films have relatively good physical properties but involve the problem that they are insufficient in transparency. There has hence been a long-standing demand for extruded polypropylene articles, especially sheets and blown films, having better transparency.
SUMMARY OF THE INVENTION
The present inventors have intensively conducted research on a syndiotactic polypropylene having excellent impact resistance balance and good transparency by which the above-mentioned problems can be solved, and as a result, they have achieved the present invention. The present invention is directed to a syndiotactic polypropylene copolymer comprising 70 to 99.9 mole % of propylene and 0.1 to 30 mole % of an olefin other than propylene; in the
13
C-NMR spectrum of the syndiotactic polypropylene copolymer, a ratio of the intensity of a peak at about 20.2 ppm to the sum of the intensities of the total peaks attributable to methyl groups in propylene units at about 19-22 ppm being 0.3 or more.
The
13
C-NMR spectrum can be obtained by measuring in a 1,2,4-trichlorobenzene solution of the copolymer on the basis of tetramethylsilane, and the ratio of the intensity of the peak at about 20.2 ppm to the sum of the intensities of the total peaks attributable to the methyl groups in the propylene units at about 19-22 ppm is a measure for indicating the syndiotacticity of the copolymer. It is known that the syndiotacticity can be defined as a syndiotactic pentad fraction obtained by analyzing the
13
C-NMR spectrum of the homopolymer of propylene (A. Zambelli et al., Macromolecules, Vol. 6, 687, 1973, and the same, Vol. 8, 925, 1975). On the contrary, in the present invention, the above ratio denotes a degree of the syndiotacticity of the propylene chain in the copolymer, and the larger the ratio is, the higher the syndiotacticity of the copolymer.
Molded articles manufactured from the copolymer of the present invention are excellent in transparency and impact resistance as compared with molded products obtained from a conventional syndiotactic polypropylene.
An object of the present invention is to provide novel extruded polypropylene articles having extremely good transparency. Another object of the present invention is to provide novel extruded polypropylene films and sheets and novel blown polypropylene films, which have extremely good transparency and relatively good strength.
Other objects of the present invention will become apparent from the following description.
In one aspect of the present invention, there is thus provided an extruded article formed by the extrusion of a polypropylene substantially having a syndiotactic structure.
The polypropylene substantially having the syndiotactic structure may preferably be a propylene copolymer whose peak intensity observed at about 20.2 ppm on a
13
C-NMR absorption spectrum as measured in the form of a 1,2,4-trichlorobenzene solution while using tetramethylsilane as a standard is at least 0.5 of the sum of all peak intensities corresponding to the respective methyl groups of propylene.
The extruded article of the polypropylene substantially having the syndiotactic structure may preferably be a film or sheet having a thickness of 0.005-5 mm or a blown film having a thickness of 0.001-1 mm.
DETAILED DESCRIPTION OF THE INVENTION
One example of a catalyst used to manufacture a propylene copolymer of the present invention is a catalyst comprising a transition metal compound having an asymmetric ligand and aluminoxane described in the aforesaid literature. In addition, another catalyst can also be used, so long as it can provide the homopolymer of propylene having a relatively high tacticity, i.e., a syndiotactic pentad fraction of about 0.7 or more.
Examples of the catalyst which can be used to manufacture the copolymer of the present invention include transition metal compounds mentioned in the aforesaid literature, i.e., isopropyl(cyclopentadienyl-1-fluorenyl)hafnium dihalogenides and isopropyl(cyclopentadienyl-1-fluorenyl)zirconium dihalogenides as well as these transition metal compounds in which at least one of halogen atoms is substituted with alkyl group. Furthermore, examples of the aluminoxane include compounds represented by the general formula
wherein R is a hydrocarbon residue having 1 to 3 carbon atoms. In particular, a methylaluminoxane is suitably used in which R is a methyl group and n is 5 or more, preferably 10 or more. The amount of the aluminoxane is 10 to 1,000,000 mole times, usually 50 to 5000 mole times as much as that of the transition metal compound. In addition to the above-mentioned catalysts, other catalysts can also be used which comprise combinations of boron compounds shown in, for example, Japanese Laid-open Patent Publication Nos. 1-501950 and 1-502036 and the transition metal compounds in which at least one of the halogen atoms is substituted with an alkyl group.
The employment of the above-mentioned catalysts permits copolymerizing propylene and another olefin at an extremely high random level, whereby the copolymer of the present invention can be characterized.
Examples of olefins other than propylene in the present invention include &agr;-olefins having 2 and 4 to 25 carbon atoms which are ethylene and &agr;-olefins represented by the general formula
H
2
C═CH—(CH
2
)
n
CH
3
(n is a value of 1 to 22)
and &agr;-olefins represented by a formula where the —(CH
2
)
n
CH
3
group in the above-mentioned formula is replaced with a branched alkyl group, for example, branched &agr;-olefins such as 3-methylbutene-1,4-methylpentene-1 and 4,4-dimethyl-pentene-1. They may be used in combination of two or more thereof on the condition that the total of these olefins is in the range of 0.1 to 30 mole % of all the constitutional monomers.
Preferable examples of the olefins other than propylene include ethylene, butene, 4-methylpentene-1, hexene-1, a combination of ethylene and butene, and a combination of ethylene and an &agr;-olefin having 6 carbon at
Asanuma Tadashi
Inoue Takeo
Iwatani Tutomu
Kimura Shigeru
Sasaki Tateyo
Burns Doane Swecker & Mathis L.L.P.
Mitsui Chemicals Inc.
Teskin Fred
LandOfFree
Syndiotactic polypropylene copolymer and extruded... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Syndiotactic polypropylene copolymer and extruded..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Syndiotactic polypropylene copolymer and extruded... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2449927