Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-04-05
2001-03-27
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
active
06207746
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to a process for producing a thermoplastic polymer composition comprising a specific olefin polymer.
(2) Description of Related Art
As a cross-linking rubber component for a thermoplastic olefin elastomer, there has heretofore been generally used an ethylene-propylene-diene rubber (EPDM). The diene component in the polymer chain of EPDM is necessary for enhancing the cross-linkability; however, the environmental deterioration resistance becomes insufficient owing to the presence of the above diene component, and an improvement in quality has been desired.
On the other hand, even in the case of an ethylene-propylene rubber (EPR) which does not contain the diene component, it is possible to cross-link the same with a radical initiator such as an organic peroxide or the like; a polyfunctional unsaturated compound; or the like. However, since EPDM and EPR which have been used in the conventional thermoplastic olefin elastomers as mentioned above are produced using a so-called “multisite catalyst” of the Ziegler type, many polymerizing active sites are present therein, the molecular weight distribution is broad, the ultra low molecular weight component is contained in a considerable amount, and hence, the balance between their own flexibility and mechanical strength is inferior.
Moreover, as to the Ziegler type EPR and EPDM, the polymer structure which can form pellets is limited and EPRs or EPDMs having the other structures are in the veil form and are complicated in handling, and hence, are not desirable. In addition, even EPR and EPDM which form pellets have a problem of blocking due to the ultra low molecular weight component, and hence, they are not desirable, either.
The present inventors have already presented, in JP-A-9-104,787, a thermoplastic composition prepared by cross-linking, with a radical initiator, a composition containing an olefin polymer produced using a metallocene type catalyst; however, it has been one which still leaves room for improvement in physical properties.
Furthermore, WO96/35,751 discloses a process for producing a vulcanized, thermoplastic, elastic composition by kneading, in the presence of a cross-linking agent, a composition containing an elastic ethylene copolymer produced using a metallocene type catalyst. However, the composition obtained still leaves room for improvement in physical properties.
SUMMARY OF THE INVENTION
An object of this invention is to improve the environmental deterioration resistance which has been a problem of conventional olefin elastomers and provide a process for producing a thermoplastic polymer composition excellent in mechanical characteristics and thermal resistance and the like.
The present inventors have earnestly repeated examination in view of the above-mentioned points, and as a result, have found that all the above-mentioned problems are solved by the process for producing a thermoplastic polymer composition stated below and have accomplished this invention.
That is to say, this invention is a process for producing a thermoplastic polymer composition comprising:
(1) 100 parts by weight of an olefin polymer which comprises ethylene and at least one &agr;-olefin having 3 to 10 carbon atoms and in which the density is in the range of 0.85 to 0.91 g/cm
3
and the molecular weight distribution (Mw/Mn) which is a ratio of weight average molecular weight (Mw) and number average molecular weight (Mn) as calculated by a gel permeation chromatography (GPC) is less than 3.0,
(2) 5 to 300 parts by weight of a propylene polymer,
(3) 5 to 250 parts by weight of an oil, and
(4) 0.02 to 3 parts by weight of a radical initiator,
which process comprises steps of previously mixing and heat-kneading the olefin polymer, the propylene polymer and the radical initiator; adding the oil in such a stage that cross-linking is in a proportion of 30 to 95% based on the cross-linking degree of the composition to be finally obtained; and further melt-kneading them to cross-link the same.
The process for producing a thermoplastic composition of this invention makes it possible to obtain a composition superior in thermal resistance such as compression set or the like and physical properties such as environmental deterioration resistance and the like as compared with the composition in which the conventional EPDM or the like is used, and its utilization value is very great.
The thermoplastic composition obtained by the process of this invention can be widely employed in uses including automobile parts, interior automotive trim materials, air bag covers, mechanical parts, electric parts, cables, horses, belts, toys, miscellaneous goods, daily necessaries, construction materials, sheets, films and the like.
PREFERRED EMBODIMENTS OF THE INVENTION
This invention is described below in detail.
Olefin polymer
The olefin polymer which is the main component constituting the thermoplastic polymer composition of this invention is a copolymer comprising ethylene and at least one &agr;-olefin having 3 to 10 carbon atoms, and has a specific density and a specific molecular weight distribution.
As the olefin having 3 to 10 carbon atoms, there are mentioned, for example, propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1, heptene-1, octene-1, nonene-l,1 decene-1 and the like. In particular, a copolymer consisting of ethylene and an a-olefin having 6 to 10 carbon atoms is preferable because it is excellent in balance between mechanical strength and radical cross-linkability.
The olefin polymer used in this invention can be produced with a known single site catalyst which has heretofore been used, particularly a metallocene type catalyst.
The metallocene type catalyst is a polymerization catalyst composed of a metallocene compound alone or a combination of a metallocene compound with a promotor. The metallocene compound is one having such a structure that a transition metal such as titanium, zirconium, hafnium or the like is coordinated with at least one unsaturated cyclic compound, and as the unsaturated cyclic compound, there are mainly used cyclopentadienyl derivatives having cyclopentadiene, indene or the like as a molecular skeleton. Moreover, as the promotor, there are used organoaluminum compounds such as alkyl aluminoxanes, alkylaluminum halides and the like; organoboron compounds; and the like.
The metallocene type catalyst is highly active as a polymerization catalyst, and in addition, characterized in that as compared with the conventional catalysts, for example, Ziegler catalysts, the molecular weight distribution of the polymer obtained is narrow and the distribution of an &agr;-olefin having 3 to 10 carbon atoms which is the comonomer in the copolymer is uniform, and the catalyst species is uniform.
The olefin polymer used in this invention is one produced using a polymerization catalyst different from the conventional Ziegler catalyst and the like, and the properties thereof are greatly different as compared with the conventional Ziegler type polymers.
The characteristic features of the olefin polymers produced using a metallocene type polymerization catalyst are listed as follows:
1. since the polymerization catalyst has an ultrahigh activity, it becomes possible to greatly heighten the composition of a-olefin, which is a comonomer, as compared with the conventional one, and an elastomeric polymer rich in flexibility is obtained even in the state that no plasticizer is contained;
2. the comonomer distribution is uniform as compared with the Ziegler type polymers;
3. the molecular weight distribution is extremely sharp as compared with the Ziegler type polymers, and the amount of the low molecular weight component is very small, the mechanical strength and processability are excellent, and the polymer has a high quality as compared with the Ziegler type polymers;
4. when a long chain branch is introduced, in spite of the molecular weight distribution being sharp, the value of ratio (I
10
/I
2
) of the melt index at 190° C./10 kgf (I
10
) to the melt index at
Shibayama Shinichi
Uchida Kensuke
Asahi Kasei Kogyo Kabushiki Kaisha
Birch & Stewart Kolasch & Birch, LLP
Michl Paul R.
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