Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-11-03
2003-10-14
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...
C526S130000, C526S160000, C526S348000
Reexamination Certificate
active
06632911
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to novel ethylene/&agr;-olefin copolymers. More particularly, it relates to ethylene/&agr;-olefin copolymers which are excellent in transparency and gloss, show high blocking resistance and exhibit well-balanced modulus and strength when processed into films by blown film extrusion.
2. Description of the Related Art
It has been a practice to produce copolymers of ethylene with &agr;-olefins by the polymerization mainly using Zeigler-Natta catalysts. Blown Films of these copolymers are excellent in mechanical characteristics (tensile strength, impact strength, etc.) and, therefore, used in a large amount for various purposes, for example, bags.
However, blown films of these ethylene/&agr;-olefin copolymers alone suffer from a problem of showing poor transparency.
Therefore, it has been a practice in the field with a need for high transparency to blend these ethylene/&agr;-olefin copolymers with low-density polyethylene produced by the high-pressure-process (hereinafter referred to simply as HPLD) which has an excellent effect of improving transparency to thereby ensure high transparency. However, this method brings about an increase in the production cost of the resin compositions. From the viewpoint of physical properties, moreover, there arise several problems, for example, a decrease in strength and worsening of blocking resistance in association with an increase in transparency.
Ethylene/&agr;-olefin copolymers produced by the polymerization using metallocene catalysts, which have been employed in recent years, are superior in transparency in the low density region (density; 0.918 or less) to the ethylene/&agr;-olefin copolymers obtained by using Ziegler-Natta catalysts. However, the transparency of the former ethylene/&agr;-olefin copolymers is worsened with an increase in density. Thus, the ethylene/&agr;-olefin copolymers having a density of 0.918 or more, which are commonly employed as packing films, cannot show any sufficient transparency. In the field with a need for high transparency, therefore, it is also needed to blend these copolymers with HPLD.
In addition, no sufficient transparency cannot be established even by elevating the molecular weight by performing the multi-stage polymerization as proposed by JP-A-3-23717 or by using two or more metallocene compounds as proposed by JP-A-5-155932 and JP-A-60-35006 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”).
Further, JP-A-10-168130 points out that the transparency can be improved by regulating the storage modulus and loss modulus each in a definite range. Even in this case, it is scarcely possible to establish such performance satisfying the requirement in the field with a need for high transparency.
Therefore, it has been urgently required to develop an ethylene/&agr;-olefin copolymer whereby these problems can be solved. However, it is impossible by the related art not only to obtain a ethylene/&agr;-olefin copolymer which can be processed into films with sufficient transparency but also to clarify the polymer structure for achieving this object.
SUMMARY OF THE INVENTION
This invention aims at providing ethylene/&agr;-olefin copolymers which show sufficient transparency and excellent mechanical properties (modulus, strength, etc.), processing properties, blocking resistance, heat sealing properties and heat sealing strength when processed into films by blown film extrusion.
The inventors have conducted extensive studies to solve the above problems. As a result, they have made it possible to uniformly form components of ethylene/&agr;-olefin copolymers for improving the transparency, compared with the related art.
Further, the inventors have clarified components worsening the transparency.
Furthermore, they have successfully found out that ethylene/&agr;-olefin copolymers with excellent transparency can be obtained by elevating the balance between the improving components and the worsening components to such an extent which cannot be achieved by the related art and regulating the contents of these components each within a definite range, thereby completing the invention.
Accordingly, the ethylene/&agr;-olefin copolymer of the invention is a copolymer of ethylene with an &agr;-olefin having 3 to 20 carbon atoms characterized by satisfying the following physical properties (a) to (d):
(a) having a density of 0.900 to 0.965 g/cm
3
;
(b) having a melt index (MI; 190° C., under a 2.16 kg load) of 0.01 to 100 g/10 min;
(c) in a chromatogram with the use of Rayleigh ratio obtained by extrapolating GPC-MALLS (Gel Permeation Chromatography-Multi Angle Laser Light Scattering detector) data at a scattering angle of 0°, showing an average of Mc: {overscore (Mc)} obtained by the “five-point measurement method” of 0.5% or more and a standard deviation <&sgr;> from the average of 35% or less, wherein Mc stands for the chromatographic area ratio of the components having molecular weight of 1,000,000 or more calculated on the basis of the above measurement; and
(d) having a W30 (weight fraction of the portion eluted from TREF column below) in CFC measurement of 1 (% by weight) or less.
The ethylene/&agr;-olefin copolymer according to the invention is characterized by satisfying the following requirement (e), in addition to the above-described requirements (a) to (d):
(e) having a flow ratio FR (=I
10kg
/I
2.16kg
) of 7.0 or less, wherein I
10kg
stands for the melt index measured at 190° C. under a 10 kg load and I
2.16kg
stands for the melt index measured at 190° C. under a 2.16 kg load.
The ethylene/&agr;-olefin copolymer according to the invention is characterized by satisfying the following requirements (f) or the requirements (e) and (f), in addition to the above-described requirements (a) to (d):
(f) having a ratio Mw/Mn of 1.5 to 3.5, wherein Mw stands for the weight-average molecular weight obtained by GPC measurement and Mn stands for the number-average molecular weight.
The ethylene/&agr;-olefin copolymer according to the invention is an ethylene/&agr;-olefin copolymer satisfying the above-described requirements (a) to (d), (a) to (e), (a) to (d) and (f), or (a) to (f), characterized by having a density of 0.918 (g/cm
3
) or less.
Further, the ethylene/&agr;-olefin copolymer according to the invention is an ethylene/&agr;-olefin copolymer satisfying the above-described requirements (a) to (d), (a) to (e), (a) to (d) and (f), or (a) to (f), characterized by having a density of 0.918 (g/cm
3
) or more and satisfying the following requirements (g):
(g) having Mc and W74 (weight fraction (% by weight) of the portion eluted from TREF column below 74° C.) in CFC measurement satisfying the following relationship (i):
W
74<5.5Log {
Mc
}+15 (i).
Furthermore, the ethylene/&agr;-olefin copolymer according to the invention is an ethylene/&agr;-olefin copolymer satisfying the following physical properties (a′) to (d′):
(a′) having a density of 0.900 to 0.955 g/cm
3
;
(b′) having a melt index (MI; 190° C., under a 2.16 kg load) of 0.01 to 100 g/10 min;
(c′) in a chromatogram with the use of Rayleigh ratio obtained by extrapolating GPC-MALLS data at a scattering angle of 0°, showing a chromatographic area ratio of the components having molecular weight of 1,000,000 or more, calculated on the basis of the above measurement, of 1% or more; and
(d′) having Mc and W74 (weight fraction (% by weight) of the portion eluted from TREF column below 74° C. ) in CFC measurement satisfying, the following relationship (ii):
W
74<5.5Log {
Mc
}+10 (ii).
The film according to the invention is processed by extruding the ethylene/&agr;-olefin copolymer as described above.
REFERENCES:
patent: 4632801 (1986-12-01), Dowd
patent: 4981760 (1991-01-01), Naito et al.
patent: 5258161 (1993-11-01), Ealer
patent: 5420220 (1995-05-01), Cheruvu et al.
patent: 5928982 (1999-07-01), Suga et al.
patent: 6034187 (2000-03-01), Maehama et al.
p
Akashige Etsushi
Ikehata Fumiyo
Ishihama Yoshiyuki
Kawase Mikio
Takahashi Kuninori
Japan Polychem Corporation
Lee Rip A
Wu David W.
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