Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-02-11
2002-06-25
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S158000, C526S160000, C526S943000, C526S351000, C502S152000
Reexamination Certificate
active
06410662
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for producing olefin polymers or copolymers capable of being controlled in molecular weight as well as novel olefin polymers or copolymers and applications thereof. More particularly, the present invention relates to a process for producing olefin polymers or copolymers of a high molecular weight wherein a polymerization time or an average retention time in a polymerization reactor is adjusted by the aid of a specific metallocene catalyst thereby enabling control of the molecular weight at the time of producing the olefin polymers or copolymers and adjustment of the molecular weight to a higher molecular weight range as well as novel olefin polymers or copolymers and injection moldings excellent in rigidity and heat-resistance, especially molded from polypropylene; films excellent in transparency in addition to the above characteristics; a composition comprising the aforesaid polypropylene and an &agr;-form nucleating agent; a modified composition which is comprised predominantly of the aforesaid polypropylene and a radical generator and has been subjected to melt-kneading treatment; and filaments or fibers or non-woven fabrics of the aforesaid propylene polymers or copolymers.
BACKGROUND ART
Olefin polymers or copolymers such as polypropylene or polyethylene are excellent in mechanical properties and chemicals-resistance and are very useful in balance to an economic aspect so that they are employed in the field of various moldings. From the past, these olefin polymers or copolymers were produced by polymerizing or copolymerizing olefins by the aid of a so-called Ziegler-Natta catalyst which is a combination of a transition metal catalytic component comprising titanium trichloride and/or tetrachloride carried on a support such as magnesium chloride with an organoaluminum compound.
In recent years, on the other hand, a process for producing olefin polymers or copolymers by polymerizing or copolymerizing olefins by the aid of a new catalyst different from the conventional catalyst system has widely been utilized, the new catalyst being comprised of a metallocene and an aluminoxane. Olefin polymers or copolymers produced by way of this metallocene catalyst system are distinguished themselves by their narrow molecular weight distribution and by the fact that in case of copolymers, the comonomer has homogeneously been copolymerized therein so that olefin polymers or copolymers which are more homogeneous than the conventional olefin polymers or copolymers can be obtained.
In the production of olefin polymers or copolymers by the aid of such metallocene catalyst system, however, there is a problem that the molecular weight of the resultant olefin polymers or copolymers are generally poor or that the molecular weight of olefin polymers or copolymers obtained at a practical but a higher polymerization temperature are too low to be used practically.
As is seen in Japanese Laid-open Patent Appln. No. Sho. 63-251405, It is known that the molecular weight of olefin polymers or copolymers can be increased by using a metallocene compound including hafnium as a transitions metal. In case of the hafnium compound, however, the polymerization activity is poor and not practical.
In Journal of Molecular Catalysis A: Chemical 102, 59-65 (1995), there is disclosed that the molecular weight of olefin polymers or copolymers can be increased by lowering the polymerization temperature. In case the polymerization temperature is lowered, however, the polymerization activity becomes extremely poor. Thus, such a method cannot be said to be practical, too.
It is disclosed in Japanese Laid-open Patent Appln. No. Hei. 6-100579 that the molecular weight of olefin polymers or copolymers can be increased by using a catalyst wherein the metallocene compound has a complicate structure. In this case, however, the synthetic route of such metallocene compound having a complicate structure becomes complicate so that cost for manufacturing the catalyst becomes too high to be practical. It is also disclosed in Macromol. Symp. 97, 205-216 (1995) that the molecular weight of olefin polymers or copolymers can be increased by increasing the monomer concentration in the polymerization system or raising the polymerization pressure. As is described in the aforesaid Journal of Molecular Catalysis A: Chemical 102, 59-65 (1995), the molecular weight of olefin polymers or copolymers becomes extremely lower by elevating the polymerization temperature up to a practical polymerization temperature. Accordingly, there is a limit for obtaining high molecular weight olefin polymers or copolymers only by increasing the monomer concentration, and it was difficult to obtain high molecular weight olefin polymers or copolymers aimed at especially in the case of using a metallocene compound having a simple structure. Hence, there is a demand for developing a means for increasing the molecular weight without such problem.
In general, crystalline propylene polymers are relatively cheap and possess excellent mechanical properties so that they are employed for manufacturing various moldings such as injection moldings.
According to the intended various concrete applications, however, the resultant polymer is sometimes insufficient in mechanical properties, especially rigidity and heat-resisting property so that there is a limitation in spreading concrete applications of the polymer.
Hence, there is a desire from the past for enhancing rigidity and heat-resisting property of moldings made of crystalline propylene polymers.
With respect to films as moldings, those disclosed in EP 0629631, Japanese Laid-open Patent Appln. No. Hei. 7-149833 and Japanese Laid-open Patent Appln. No. Hei. 8-73532 can be mentioned as examples of applications of isotactic polypropylene obtained by the aid of a metallocene catalyst system. In these examples, copolymerization is carried out to realize high transparency as one of the requisites of films.
Among a wide versatility of applications of polypropylene, a polypropylene composition excellent in rigidity, heat-resisting property and transparency is firstly demanded. For this purpose, a variety of nucleating agents are employed to improve rigidity and heat-resisting property of crystalline propylene polymers.
On the other hand, in Japanese Laid-open Patent Appln. No. Hei. 5-9225 and Japanese Laid-open Patent Appln. No. Hei. 5-32723 a resin of polypropylene type containing a propylene polymer is proposed wherein the position of a main elution peak (T
max
) according to the temperature rising elution chromatography is 117.0° C. or at least 118.0° C. for the purpose of improving rigidity and heat-resisting property. There is also disclosed that the resin may be incorporated at need with a nucleating agent.
In Japanese Laid-open Patent Appln. No. Hei. 7-10932, it is proposed propylene polymers wherein a percentage by weight of propylene polymers capable of being dissolved in o-dichlorobenzene at 120-135° C. is more than the value obtained by the formula:
(40−15 log MFR)×100 (I)
wherein MFR stands for a melt flow rate of the propylene polymers, in case of elevating the temperature of o-dichlorobenzene continuously or stepwise to given temperatures to measure the amount of polypropylene eluted at each temperature, for the purpose of improving rigidity and heat-resisting property.
In the applied field of polypropylene, a modified polypropylene composition is demanded which excels in heat-resisting property and in mold processing in the field of fibers on the basis of a narrow molecular weight distribution.
In WO94/28219, there is disclosed that a homopolypropylene of a low melting point obtained by the aid of a metallocene catalyst system is incorporated with a radical generator and the mixture is kneaded to lower the molecular weight of the polypropylene. However, there is neither description nor suggestion in connection with the merit that a specific polypropylene of the present invention having a high melting point can reduce its molecular weig
Adachi Minoru
Fujita Hiroyuki
Hirose Taketo
Kugimiya Youichi
Kuramochi Hitoshi
Chisso Corporation
Leydig , Voit & Mayer, Ltd.
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