Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1997-02-12
2001-02-06
Wilson, Donald R. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C526S943000
Reexamination Certificate
active
06184297
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an ethylene copolymer composition. More particularly, the invention relates to an ethylene copolymer composition comprising an ethylene/&agr;-olefin copolymer and other polyolefins, and to an ethylene copolymer composition comprising two kinds of ethylene/&agr;-olefin copolymers and other polyolefins.
BACKGROUND OF THE INVENTION
Ethylene copolymers have heretofore been molded by various molding methods, and used in many fields. The requirement for the characteristics of the ethylene copolymers differs depending on the molding methods and uses. For example, when an inflation film is molded at a high speed, it is necessary to select an ethylene copolymer having a high melt tension compared with its molecular weight in order to stably conduct high speed molding without fluctuation or tearing of bubbles. An ethylene copolymer is required to have similar characteristics in order to prevent sag or tearing in blow molding, or to suppress width shortage to the minimum range in T-die molding.
By the way, low density polyethylene obtained by high pressure radical method is applyed to the use of films and hollow containers due to the high melt tension thereof compared with ethylene copolymers produced by using Ziegler type catalyst. However, the low density polyethylene obtained by the high pressure radical method is poor in mechanical properties such as tensile strength, tear strength and impact strength, and further is low in heat resistance and stress cracking resistance.
In contrast, Japanese Patent L-O-P Nos. 90810/1981 and 106806/1985 propose a method for improving moldability by improving the melt tension and die swell ratio of ethylene polymers obtained by using Ziegler type catalysts, especially a titanium type catalyst.
The ethylene polymers obtained by using a titanium catalyst, however, especially the low density ethylene polymers generally have problems such as their broad composition distribution and stickiness of their molded articles such as films.
Of the ethylene polymers prepared by using the Ziegler type catalysts, those obtained by using chromium type catalysts are relatively excellent in melt tension but has a defect of poor heat stability. This is thought to be caused by that the chain terminals of the ethylene polymers prepared by using the chromium type catalysts tend to become unsaturated bonds.
It is known that the ethylene polymers obtained by using a metallocene catalyst from among the Ziegler type catalysts have merits such as a narrow composition distribution and a low stickiness of their molded articles such as films. However, it is described in, for example Japanese Patent L-O-P. No. 35007/1985, that an ethylene polymer obtained by using a zirconocene compound formed from a cyclopentadienyl derivative contains one terminal unsaturated bond per molecule, and hence this ethylene polymer is presumably poor in heat stability similarly to the above-mentioned ethylene polymer obtained by using the chromium type catalyst.
Accordingly, it will industrially be of great value to provide an ethylene copolymer having good heat stability, high mechanical strength and a narrow composition distribution.
By the way, ethylene copolymers generally have no polar group in the molecule and inherently non-polar, so that they are insufficient in adhesion strength to highly polar materials such as metals and polar resins. For these reasons, when such ethylene copolymers are used by bonding them with the highly polar materials, it is necessary to subject the surface of the ethylene copolymer to a flame treatment, a corona discharge treatment, a primer treatment or the like, and hence resulting in a problem of complicated operation.
Accordingly, it will also industrially be of great value to provide an ethylene copolymer composition, which has high melt tension, good heat stability and high mechanical strength and shows sufficient adhesion strength to highly polar materials.
OBJECT OF THE INVENTION
It is, therefore, an object of the present invention to provide an ethylene copolymer composition of good moldability which is capable for giving a film having higher transparency and mechanical strength, and to provide an ethylene copolymer composition having good moldability and excellent transparency which is capable for giving a film having high adhesion strength to highly polar materials.
SUMMARY OF THE INVENTION
The first ethylene copolymer composition according to the present invention is characterized by comprising:
[A1] an ethylene/&agr;-olefin copolymer, which is obtained by copolymerizing ethylene with an &agr;-olefin of 3 to 20 carbon atoms in the presence of a catalyst for olefin polymerization comprising (a) an organoaluminum oxy-compound and (b) at least two kinds of compounds of Group IV transition metals of the periodic table containing a ligand having a cyclopentadienyl skeleton, and which has such properties that:
(i) the density is in the range of 0.850 to 0.980 g/cm
3
,
(ii) the melt flow rate (MFR) at 190° C. under a load of 2.16 kg is in the range of 0.01 to 200 g/10 min,
(iii) the melt tension (MT (g)) at 190° C. and the melt flow rate (MFR) satisfy the relation
MT>
2.2
×MFR
−0.84
, and
(iv) the flow index (FI (l/sec)) defined by a shear rate which is given when a shear stress of molten copolymer at 190° C. reaches 2.4×10
6
dyne/cm
2
and the melt flow rate (MFR) satisfy the relation
FI<
150
×MFR
; and
[B1] a high-pressure radical polymerization low-density polyethylene having the melt flow rate (MFR) of 0.01 to 100 g/10 min;
wherein a weight ratio ([A1]:[B1]) between said ethylene/&agr;-olefin copolymer [A1] and said high-pressure radical polymerization low-density polyethylene [B1] is in the range of 99:1 to 60:40.
In the invention, the above-mentioned at least two kinds of compounds (b) of Group IVB transition metals of the periodic table containing a ligand having a cyclopentadienyl skeleton are preferably:
at least one kind of a transition metal compound represented by the following formula [b-I]:
ML
1
x
[b-I]
wherein M is a transition metal atom selected from Group IVB of the periodic table, L
1
is a ligand coordinating to the transition metal atom M, at least two of L
1
are groups selected from a cyclopentadienyl group, a methylcyclopentadienyl group, an ethylcyclopentadienyl group and a substituted cyclopentadienyl group having at least one substituent group selected from a hydrocarbon group of 3 to 10 carbon atoms, 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
at least one kind of a transition metal compound represented by the following formula [b-II]:
ML
2
x
[b-II]
wherein M is a transition metal atom selected from Group IVB of the periodic table, L
2
is a ligand coordinating to the transition metal atom, at least two of L
2
are substituted cyclopentadienyl groups having 2-5 substituent groups selected from a methyl group and an ethyl group, L
2
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.
The ethylene copolymer composition is excellent in moldability. From this composition, a film having high transparency and high mechanical strength can be produced.
The second ethylene copolymer composition according to the present invention is characterized by comprising:
the above mentioned ethylene/&agr;-olefin copolymer [A1] in an amount of 60 to 99% by weight, and
[B2] at least one crystalline polyolefin in an amount of 1 to 40% by weight, said crystalline polyolefin being selected from the group consisting of:
(B-I) an ethylene homo
Ikeyama Seiichi
Inagaki Hajime
Ohta Seiji
Takahashi Mamoru
Todo Akira
Mitsui Chemicals Inc
Wilson Donald R.
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