Ethylene copolymer composition and uses thereof

Details Ethylene copolymer composition and uses thereof Ethylene copolymer composition and uses thereof

1999-11-08

2001-12-11

Nutter, Nathan M. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S240000

Reexamination Certificate

active

06329465

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an ethylene copolymer composition and uses thereof. The invention further relates to uses of the ethylene copolymer composition.
BACKGROUND OF THE INVENTION
Ethylene copolymers are molded by various molding methods and used in many fields. The properties required for the ethylene copolymers differ from each other according to the molding methods and the uses of the copolymers. For example, in molding of an inflation film at a high-speed, an ethylene copolymer having high melt tension for its molecular weight must be selected in order to stably perform high-speed molding free from occurrence of bubble swing or bubble break. The similar properties are required to prevent sag or break in a blow molding method or to lower reduction of width to the minimum in a T-die molding method.
In Japanese Patent Laid-Open Publication No. 90810/1981 or No. 106806/1985, a method of increasing melt tension or swell ratio (die swell ratio) of ethylene polymers obtained by the use of Ziegler catalysts, particularly titanium catalysts, to improve moldability of the polymers is reported. In general, the ethylene polymers obtained by the use of the titanium catalysts, particularly low-density ethylene copolymers, however, have a wide composition distribution and contain components which cause tackiness when the polymers are used as molded products such as films. Therefore, more decrease of the components causing tackiness has been demanded.
Of the ethylene polymers produced by the use of Ziegler catalysts, those obtained by the use of chromium catalysts have relatively high melt tension, but further improvement in the heat stability has been demanded.
A great number of ethylene copolymers obtained by the use of olefin polymerization catalysts containing transition metal metallocene compounds have high melt tension and excellent heat stability, so that they are expected as copolymers satisfying the above demands. In the ethylene copolymers obtained by the use of the metallocene catalysts, however, the melt tension (MT) is generally proportional to the flow activation energy (Ea).
Polymers having high melt tension have excellent moldability because they have excellent bubble stability as mentioned above. They, however, have high flow activation energy (Ea), and this means that the molding conditions thereof have great dependence on the temperature. Therefore, if the molding conditions are not controlled very strictly and uniformly, the resulting molded products suffer unevenness. For example, films may have low transparency.
When the flow activation energy (Ea) is low, occurrence of unevenness in the molded products can be inhibited, but because of low melt tension, unstable bubble is produced and hence moldability is lowered.
The present invention has been made under such circumstances as described above, and it is an object of the invention to provide an ethylene copolymer composition having excellent moldability and capable of producing films and molded products of excellent transparency and mechanical strength. It is another object of the invention to provide uses of this ethylene copolymer composition.
DISCLOSURE OF THE INVENTION
The ethylene copolymer composition (A) according to the invention comprises
(A) an ethylene/&agr;-olefin copolymer and (E) high-pressure radical process low-density polyethylene,
wherein the ethylene/&agr;-olefin copolymer (A) is a copolymer of ethylene and an &agr;-olefin of 6 to 8 carbon atoms and has the following properties:
(A-i) the melt tension (MT) at 190° C. and the melt flow rate (MFR) satisfy the following relation
9.0×MFR
−0.65
>MT>2.2×MFR
−0.84
,
(A-ii) the activation energy ((E
a
)×10
−4
J/molK) of flow determined from a shift factor of time-temperature superposition of the flow curve, the carbon atom number (C) of the &agr;-olefin in the copolymer and the &agr;-olefin content (x mol %) in the copolymer satisfy the following relation
(0.039 Ln (C−2)+0.0096)×
x+
2.87<Ea×10
−4
<(0.039 Ln (C−2)+0.1660)×
x+
2.87,
and
(A-iii) the haze of a film having a thickness of 30 &mgr;m produced by inflation molding of the copolymer satisfies the following relation,
when the flow index (FI), which is defined by a shear rate at which the shear stress at 190° C. reaches 2.4×10
6
dyne/cm
2
, and the melt flow rate (MFR) satisfy the relation FI≧100×MFR,
in the case of the carbon atom number (C) of the &agr;-olefin being 6,
Haze<0.45/(1−d)×log(3×MT
1.4
)×(C−3)
0.1
,
in the case of the carbon atom number (C) of the &agr;-olefin being 7 or 8,
 Haze<0.50/(1−d)×log(3×MT
1.4
),
and
when the flow index (FI) defined by a shear rate at which the shear stress at 190° C. reaches 2.4×10
6
dyne/cm
2
and the melt flow rate (MFR) satisfy the relation FI<100×MFR,
in the case of the carbon atom number (C) of the &agr;-olefin being 6,
Haze<0.25/(1−d)×log(3×MT
1.4
)×(C−3)
0.1
,
in the case of the carbon atom number (C) of the &agr;-olefin being 7 or 8,
Haze<0.50/(1−d)×log(3×MT
1.4
);
wherein d represents a density (g/cm
3
) and MT represents a melt tension (g), and
the high-pressure radical process low-density polyethylene (E) has the following properties:
(E-i) the melt flow rate, as measured at 190° C. under a load of 2.16 kg, is in the range of 0.1 to 50 g/10 min, and
(E-ii) the molecular weight distribution (Mw/Mn, Mw: weight-average molecular weight, Mn: number-average molecular weight), as measured by gel permeation chromatography, and the melt flow rate (MFR) satisfy the following relation
7.5×log(MFR)−1.2≦Mw/Mn≦7.5×log(MFR)+12.5.
The ethylene/&agr;-olefin copolymer (A) is obtained by copolymerizing ethylene and an &agr;-olefin of 6 to 8 carbon atoms in the presence of, for example, an olefin polymerization catalyst comprising:
(a) an organoaluminum oxy-compound,
(b-1) at least one transition metal compound selected from transition metal compounds represented by the following formula (I):
ML
1
x
  (I)
 wherein M is a transition metal atom selected from Group 4 of the periodic table; L
1
is a ligand coordinated to the transition metal atom M, at least two ligands L
1
are each a substituted cyclopentadienyl group having at least one group selected from hydrocarbon groups of 3 to 10 carbon atoms and the ligand L
1
other than the substituted cyclopentadienyl group is a hydrocarbon group of 1 to 12 carbon atoms, an alkoxy group, an aryloxy group, a trialkylsilyl group, a halogen atom or a hydrogen atom; and x is a valence of the transition metal atom M, and
(b-II) at least one transition metal compound selected from transition metal compounds represented by the following formula (II):
ML
2
x
  (II)
 wherein M is a transition metal atom selected from Group 4 of the periodic table; L
2
is a ligand coordinated to the transition metal atom M, at least two ligands L
2
are each a methylcyclopentadienyl group or an ethylcyclopentadienyl group and the ligand L
2
other than the methylcyclopentadienyl group or the ethylcyclopentadienyl group is a hydrocarbon group of 1 to 12 carbon atoms, an alkoxy group, an aryloxy group, a trialkylsilyl group, a halogen atom or a hydrogen atom; and x is a valence of the transition metal atom M.
In the olefin polymerization catalyst, the organoaluminum oxy-compound (a), the transition metal compound (b-I) and the transition metal compound (b-II) are preferably supported on a carrier (c).
Another embodiment of the present invention is an ethylene copolymer composition (A′) comprising (B) an ethylene/&agr;-olefin copolymer, (C) an ethylene/&agr;-olefin copolymer and (E) high-pressure radical process low-density polyethylene,
wherein the ethylene/&agr;-olefin copolymer (B) is a copolymer of ethylene and an &agr;-olefin of 6 to 8 carbon atoms and has the following properties:
(B-i) the density is in th

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