&agr;-olefin-based copolymer, process for the production...

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...

Reexamination Certificate

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C526S160000, C526S161000, C526S336000, C526S916000, C526S943000, C502S155000

Reexamination Certificate

active

06420506

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a copolymer suitable for a stretch film, a shrink film and a wrap film, a process for the production thereof, and a molded article comprising the same.
2. Description of the Related Arts
In general, an elastic recoverability, a transparency and a mechanical strength found in a polyvinyl chloride are required for a copolymer to be used as various films such as a stretch film, a shrink film, a wrap film and the like. However, the polyvinyl chloride comes in question concerning environmental pollution because of the possibility of generation of harmful substances at incineration, etc. Various kinds of polymers are presently considered as a replacement for the polyvinyl chloride, but it is the status quo that none of them have been obtained that are satisfactory from the viewpoints of viscoelastic properties and transparency.
Since copolymerization of an &agr;-olefin represented by propylene with an alkenyl aromatic hydrocarbon represented by styrene was carried out using a Solvay type titanium trichloride catalyst, studies using various solid catalysts have been carried out. For example, polymerization processes which use a solid catalyst prepared by using titanium tetrachloride and an electron donor are disclosed in Japanese Patent Publication (Kokai) Nos.60-26011 and 4-318006. However, in both of those processes, the polymerization activity is low and a homopolymer is formed as a by-product. Further, the obtained copolymer has a low amount of copolymerized styrene and a crystallinity, and is not adequate from the viewpoints of elastic recoverability, flexibility and transparency.
Japanese Patent Publication (Kokai) No.8-269134 discloses a process for producing a copolymer of propylene with styrene which has syndiotactic propylene sequences using a so-called homogeneous Ziegler-Natta catalyst which uses a specific transition metal compound and an organoaluminum compound. However, the copolymer obtained by the process, has also a low styrene content and a crystallinity, and is insufficient from the viewpoints of elastic recoverability, flexibility and transparency.
Further, because such copolymer has a tendency of which the molecular weight of the copolymer becomes lower with the increase of the styrene content, there is a problem that the copolymer of high styrene content is insufficient in mechanical strength.
SUMMARY OF THE INVENTION
The present invention was accomplished in view of the above-situations. Namely, the object of the present invention is to provide a copolymer of an &agr;-olefin, a mono-alkenyl aromatic hydrocarbon (herein-after, sometimes referred to simply as “alkenyl aromatic hydrocarbon”) and a diene, having an excellent elastic recoverability and flexibility, and being capable of taking a constitution in which a halogen is not contained.
Another object of the present invention is to provide a process for producing said copolymer at an extremely high polymerization activity.
Other objects of the present invention are to provide a molded article comprising said copolymer and being excellent in elastic recoverability, flexibility and mechanical strength, and the like.
In order to accomplish the objects described above, the present inventors have extensively studied regarding a copolymer of an &agr;-olefin, an alkenyl aromatic hydrocarbon and a diene based on a producing method using a transition metal compound represented by a metallocene as a catalyst component, and as the result, the present inventors have attained the present invention.
Namely, the present invention relates to a copolymer of an &agr;-olefin, an alkenyl aromatic hydrocarbon and a diene. Further, the present invention relates to a process for producing the fore-mentioned copolymer, which comprises copolymerizing an &agr;-olefin, a mono-alkenyl aromatic hydrocarbon and a diene in the presence of a catalyst prepared by using (A) and (B), (A) and (C), or (A), (B) and (C) described below, and a molded article comprising the copolymer.
(A): a transition metal complex represented by the following general formula [I], [II] or [III]:
wherein M
1
indicates a transition metal atom of the Group IV of the Periodic Table of the Elements, A indicates an atom of the Group XVI of the Periodic Table of the Elements, J indicates an atom of the Group XIV of the Periodic Table of the Elements, Cp
1
indicates a group having a cyclopentadiene type anion skeleton, each of X
1
, X
2
, R
1
, R
2
, R
3
, R
4
, R
5
and R
6
independently indicates a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, an aryl group, a substituted silyl group, an alkoxy group, an aralkyloxy group, an aryloxy group or a di-substituted amino group, X
3
indicates an atom of Group XVI of the Periodic Table of the Elements, R
1
, R
2
, R
3
, R
4
, R
5
and R
6
may be optionally combined with each other to form a ring; and in the general formula [II] or [III], two of M
1
, A, J, Cp
1
, X
1
, X
2
, X
3
, R
1
, R
2
, R
3
, R
4
, R
5
and R
6
may be respectively the same or different;
(B) one or more aluminum compounds selected from the following (B1) to (B3);
(B1) an organoaluminum compound represented by the general formula E
1
a
AlZ
3−a
,
(B2) a cyclic aluminoxane having a structure represented by the general formula {—Al(E
2
)—O—}
b
, and
(B3) a linear aluminoxane having a structure represented by the general formula E
3
{—Al(E
3
)—O—}
c
AlE
3
2
,
wherein E
1
, E
2
and E
3
respectively represent a hydrocarbon group, all of E
1
, all of E
2
and all of E
3
may be the same or different, Z represents a hydrogen atom or a halogen atom, and all of Z may be the same or different, “a” represents a number satisfying the expression 0<a ≦3, “b” represents an integer of 2 or more and “c” represents an integer of 1 or more; and
(C) a boron compound of any one of the following (C1) to (C3):
(C1) a boron compound represented by the general formula BQ
1
Q
2
Q
3
,
(C2) a boron compound represented by the general formula G
+
(BQ
1
Q
2
Q
3
Q
4
)

, and
(C3) a boron compound represented by the general formula (L—H)
+
(BQ
1
Q
2
Q
3
Q
4
)

,
wherein B represents a boron atom in the trivalent valence state, Q
1
to Q
4
may be the same or different and respectively represent a halogen atom, a hydrocarbon group, a halogenated hydrocarbon group, a substituted silyl group, an alkoxy group or a di-substituted amino group, G
+
represents an inorganic or organic cation, L represents a neutral Lewis base, and (L—H)
+
represents a Br&phgr;nsted acid.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is further illustrated in detail below.
The copolymer of an &agr;-olefin, a mono-alkenyl aromatic hydrocarbon and a diene in the present invention is a copolymer containing repeating units derived from the &agr;-olefin and repeating units derived from the alkenyl aromatic compound and repeating units derived from the diene (herein-after, respectively referred to simply as “&agr;-olefin unit”, “alkenyl aromatic hydrocarbon unit” and “diene unit”).
The &agr;-olefin used in the present invention includes preferably &agr;-olefins having 3 to 20 carbon atoms, and the specific examples thereof include linear olefins such as propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-eicocene and the like, branched olefins such as 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 5-methyl-1-hexene and the like, vinylcyclohexane, and the like. Among these, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1-pentene and vinylcyclohexane are more preferable, and propylene is particularly preferable.
The alkenyl aromatic hydrocarbon used in the present invention is preferably a mono-alkenyl hydrocarbon having an aromatic hydrocarbon group having 6 to 25 carbon atoms. Specific examples of the aromatic hydrocarbon group having 6 to 25 carbon a

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