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
2001-05-17
2003-05-06
Seidleck, James J. (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...
C525S244000, C525S243000, C525S241000, C525S248000, C525S256000, C525S268000, C526S170000, C526S347000
Reexamination Certificate
active
06559234
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for producing an olefin/styrene/diene type cross-copolymer or cross-copolymerization product having excellent mechanical properties and high heat resistance and being excellent in processability and economical efficiency, and the obtained cross-copolymer or cross-copolymerization product, and further an excellent process for producing an olefin/diene type cross-copolymer or a cross-copolymerization product. Further, it relates to their applications.
BACKGROUND ART
Ethylene/styrene Copolymers
Some ethylene/styrene random copolymers obtainable by means of a so-called Ziegler-Natta catalyst system comprising a transition metal catalyst component and an organic aluminum compound, and processes for their production, are known.
JP-A-3-163088 and JP-A-7-53618 disclose ethylene/styrene copolymers containing no normal (i.e. head-to-tail) styrene chain, so-called pseudo-random copolymers, obtainable by means of a complex having a so-called constrained geometric structure.
JP-A-6-49132 and Polymer Preprints, Japan, 42, 2292 (1993) disclose processes for producing similar ethylene/styrene copolymers containing no normal styrene chain, i.e. pseudo-random copolymers, by means of a catalyst comprising a cross-linkeded metallocene type Zr complex and a cocatalyst. These copolymers have no stereoregularity derived from styrene units.
Further, recently, it has been reported to produce an ethylene/styrene copolymer having a stereoregularity of alternating copolymerization type by means of a certain specific cross-linkeded bisindenyl type Zr complex i.e. a racemic [ethylenebis(indenyl)zirconium dichloride] under an extremely low temperature (−25° C.) condition. (Macromol. Chem., Rapid Commun., 17, 745 (1996).) However, with the copolymer obtainable by this complex, the molecular weight is not yet practically sufficient, and the compositional distribution is also large.
The above copolymers have no styrene chain structures and thus have drawbacks that the compatibility with styrene type polymers is low, and they are not suitable for use as an alloy or a compatibilizing agent for styrene type polymers. Further, their mechanical properties such as the initial modulus of elasticity and high temperature characteristics (heat resistance) are also inadequate.
Further, JP-A-9-309925 and JP-A-11-130808 disclose novel ethylene/styrene copolymers which respectively have styrene contents of from 1 to 55 mol % and from 1 to 99 mol % and which have ethylene/styrene alternating structures and isotactic stereoregularity in their styrene chain structures and further have head-to-tail styrene chain structures, with the alternating degrees (&lgr; values in this specification) of the copolymers being at most 70. Further, these copolymers have high transparency. However, even with such ethylene/styrene copolymers, the content of styrene chains is not adequate, and they are not adequate for use as a compatibilizing agent or as a component of an alloy. Further, their mechanical properties such as the initial modulus of elasticity and high temperature characteristics (heat resistance) are not yet fully satisfactory.
Ethylene/&agr;-olefin Copolymers
Ethylene/&agr;-olefin copolymers having 1-hexene, 1-octene or the like co-polymerized to ethylene, i.e. so-called LLDPE, are flexible and transparent and have high strength, whereby they are widely used as e.g. films for general use, packaging materials or containers. However, as a nature of polyolefin type resins, their printability and coating properties are low, and special treatment such as corona treatment will be required for printing or coating. Further, they have poor affinity with an aromatic vinyl compound polymer such as a polystyrene or a polar polymer, and in order to obtain a composition with such a resin having good mechanical properties, it has been necessary to employ an expensive compatibilizing agent additionally. Further, they have also a problem that the surface hardness is low, and they are susceptible to scratching.
Grafted Ethylene/p-methylstyrene Copolymer
On the other hand, an attempt to synthesize a graft product of a p-methylethylene/styrene copolymer with other resin by means of a metallocene catalyst or CGCT catalyst, has been reported, for example, in WO/9616096A1, U.S. Pat. No. 5,543,484 or J. Polym. Sci. PartA, Polym. Chem., 36, 1017 (1998).
Such method is designed so that methyl groups of p-methylstyrene units of the copolymer are activated, e.g. lithio-modified, so that the graft polymerization is carried out using them as polymerization initiation points. However, it is necessary to chemically activate methyl groups after the copolymer is recovered and purified from the polymer solution. Further, to complete this process, a reaction for a long period of time is required, such being not practical. There is an additional problem that p-methylstyrene is expensive as compared with styrene. The graft copolymer thus obtained usually has graft chains independently branched from the polymer main chain, but when it is used as a compatibilizing agent or as a composition, the strength of the interface of the polymer microstructure can not be said to be adequate.
Common Graft Copolymers
As a method for obtaining a graft copolymer, a method has been heretofore known wherein a graft copolymer of an olefin type polymer or an olefin/styrene type copolymer is obtained during the polymerization or during the mold processing by a common known radical graft treatment. However, this method is disadvantageous from the viewpoint of costs. Further, the obtainable graft copolymer usually has a problem that it is non-uniform and partially gelled to be not soluble, whereby the moldability tends to be impaired. The graft copolymer thus obtained, usually has graft chains independently branched from the polymer main chain, but when such copolymer is employed as a composition or a compatibilizing agent, the strength of the interface of the polymer microstructure can not be said to be sufficient.
Grafted Syndiotactic Polystyrene
JP-A-11-124420 discloses a technique for improving toughness of a syndiotactic polystyrene by synthesizing an olefin/styrene/diene copolymer by means of a coordination polymerization catalyst containing a metallocene catalyst, followed by coordination polymerization to graft-copolymerize (cross-copolymerize in this invention) a syndiotactic polystyrene chain. However, there is no other disclosure than the production of a graft-copolymerized syndiotactic polystyrene. Besides, with the disclosed coordination polymerization catalyst, the ability to copolymerize a diene (divinylbenzene) is so low that a large amount of the diene has to be charged to the polymerization solution in the coordination polymerization step, and a large amount of an unreacted diene will consequently remain in the polymerization solution. If such a coordination polymerization solution is used as it is in the subsequent step, the crosslinking degree of the obtainable polymer tends to be extremely high due to the remaining diene, thus leading to gelation or substantial deterioration in the processability. Therefore, it will be required to separate and purify the polymer from the coordination polymerization solution before proceeding with the next graft copolymerization step. The separation and purification of the polymer from the polymer solution are very cumbersome and will bring about a substantial increase of costs.
Cross-copolymerization by Anionic Polymerization
JP-A-1-118510 discloses a technique to synthesize an olefin/divinylbenzene copolymer by coordination polymerization employing a Zieglar-Natta catalyst and then graft (the same meaning as cross-copolymerize in the present invention) polystyrene chains by anionic polymerization. In this technique, a Zieglar-Natta catalyst is employed in the coordination polymerization step, the diene content in the obtained copolymer is highly non-uniform, and accordingly, the copolymer obtainable by grafting is also non-uniform and is likely to undergo gelati
Arai Toru
Nakajima Masataka
Otsu Toshiaki
Asinovsky Olga
Denki Kagaku Kogyo Kabushiki Kaisha
Seidleck James J.
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