Elastomeric polypropylene

Details Elastomeric polypropylene Elastomeric polypropylene

2001-05-08

2003-10-21

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...

C526S161000, C526S172000, C526S351000, C526S160000, C526S943000

Reexamination Certificate

active

06635733

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to an elastomeric polypropylene with excellent transparency. More particularly, the invention relates to an elastomeric polypropylene with excellent transparency, flexibility and elastic recovery.
BACKGROUND OF THE INVENTION
In general, it is thought that a crystalline polypropylene consists mostly of an isotactic or syndiotactic structure and an amorphous polypropylene consists mostly of an atactic structure.
U.S. Pat. No. 3,175,999 discloses a polypropylene prepared by fractionation from a polymer mixture containing an isotactic polypropylene and an atactic polypropylene as a major component and also discloses that the polypropylene is an elastomeric polypropylene with elastic properties due to a stereoblock structure wherein an isotactic block and an atactic block are arranged alternately.
As a process for producing such polypropylene having a stereoblock structure wherein an isotactic block and an atactic block are arranged alternately, the so-called stereoblock polypropylene at the polymerization reaction stage, German Patent 300,293 discloses a process using a catalyst comprising a supported titanium halide or vanadium halide, and U.S. Pat. No. 4,335,225 discloses a process using a catalyst comprising tetraalkylzirconium or tetraalkyl titanium supported on a metal oxide.
These heterogeneous catalysts have a plurality of different types of heterogeneously catalytic active sites, and therefore the product obtained with such catalyst is a mixture of plural heterogeneous polymers which can be fractionated by extraction fractionation with a solvent. Different fractions fractionated from said mixture have typically different molecular weight and molecular weight distribution, respectively and their physical properties are different from one another.
It is known that a metallocene catalyst can be used to produce selectively a polymer having an atactic, isotactic or syndiotactic structure. As disclosed by Ewen et al. in J. Am. Chem. Soc., 106, 6355-6364 (1984), a bridged metallocene catalyst of a racemic structure can be used to produce an isotactic polypropylene, and a bridged metallocene catalyst of a meso structure can be used to produce an atactic polypropylene.
Metallocene catalysts which can produce polypropylene with elastic properties include those reported by Chien, Linas et al in J. Am. Chem. Soc., 113, 8569-8570 (1991), those reported by Cheng, Babu et al in Macromolecules, 25, 6980-6987 (1992) and those reported by Linas, Dong et al in Maclomolecules, 25, 1242-1253 (1992).
However, the catalysts reported in these references have a polymerization activity as low as 3.5×10
5
(g-polymer/mol·Metal) and the molecular weight of the resulting polymer does not exceed 200,000. The composition of the resultant polypropylene was so homogeneous as to dissolve completely in diethyl ether, which did not achieve the elastic properties due to the stereoblock structure as mentioned above. Further reportedly, the polypropylene had a melting point of lower than 70° C., an elongation at break of 1300% at maximum and a tensile tension of 12.1 MPa.
In Japanese Patent Kohyo Hei 9-510745, Waymouth et al has proposed new metallocene catalyst containing a stereoblock structure wherein an isotactic structure and an atactic structure are arranged alternately, which can produce an elastic polypropylene with extensive elastic properties. The catalysts proposed therein are non-bridged metallolcene catalysts containing principally a substituted indenyl group as a ligand. These catalysts can contribute to the control of polymer molecule structure at a rate slower than the insertion of olefin, but faster than the average time required for forming a single polymer molecule chain, thus resulting in forming the stereoblock structure in the polypropylene molecule chain in the process of polymerization reaction.
Such elastic polypropylene is generally called “elastomeric polypropylene”. It is known that these prior elastomeric polypropylenes have a performance of the same level as a plasticized poly vinyl chloride in respect of the elastic recovery and also they have typically a performance of about 70-95 HDA in respect of a durometer hardness of type A measured in accordance with JIS K7215, which shows the performance level to replace part of the plasticized polyvinylchloride.
However, these prior elastomeric polypropylenes are inferior in transparency to a plasticized polyvinylchloride. In particular, this tendency is remarkable in the application for which relatively high durometer hardness of about 85-95 HDA is required. To use polypropylene as a substitute of the plasticized polyvinylchloride with which we are anxious about a bad influence to environment, the development of elastomeric polypropylene with high transparency has been demanded even in such application for which relatively high durometer hardness has been required.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an elastomeric polypropylene with excellent transparency. Another object of the invention is to provide an elastomeric polypropylene having high transparency even in relatively high durometer hardness. Further object of the invention is to provide an elastomeric polypropylene having high transparency and high elastic properties.
According to the present invention, there is provided an elastomeric polypropylene wherein (a) an isotactic pentad (I
5
) is 0.150-0.749, (b) a different bond due to a 2,1-insertion reaction is 0.11-20 mol %, (c) a different bond due to a 1,3-insertion reaction is 0-10 mol % and (d) a melting point (Tm) is 50-160° C., (a) to (c) being determined from
13
C NMR spectra, obtainable by the polymerization of propylene using any one of a metallocene catalyst (I) comprising a metallocene compound (A), an activating compound (B) and if desired, an organoaluminum compound (C); a supported metallocene catalyst (II) prepared by supporting the metallocene catalyst (I) on a finely particulate support (D); and a supported metallocene catalyst (III) prepared by adding an organoaluminum compound (E) to the supported metallocene catalyst (II).
DETAILED DESCRIPTION OF THE INVENTION
The elastomeric polypropylene of the present invention may have also an elongation at break of 100-2,000%, an ultimate tensile strength of 5-35 MPa, a permanent set of 3-75% and a compression set of 30-90% which were measured in accordance with JIS K6301 using said polypropylene.
Further, the elastomeric polypropylene of the invention may have a durometer hardness of type A (HDA) of 30-99 which was measured in accordance with JIS K7215 using said polypropylene.
Furthermore, the elastomeric polypropylene of the invention may have a weight average molecular weight (Mw) of 30,000-1,000,000.
In addition, the elastomeric polypropylene of the invention may have a haze of 1-55% which was measured in accordance with ASTM 1003 using a pressed sheet having a thickness of 1 mm prepared from said polypropylene.
Further, the elastomeric polypropylene of the invention may have a molecular weight distribution (ratio (Mw/Mn) of the weight average molecular weight (Mw) to a number average molecular weight (Mn)) of 1.5-4.0.
Of the requirements for characterizing the elastomeric polypropylenes of the present invention, those wherein (a) an isotactic pentad (I
5
) is 0.150-0.749, (b) a different bond due to a 2,1-insertion reaction is 0.11-20 mol %, (c) a different bond due to a 1,3-insertion reaction is 0-10 mol % are calculated from the
13
C NMR spectra determined in accordance with the following method.
More specifically, the polymer to be tested was dissolved in a mixed solution of o-dichlorobenzene/benzene bromide with 8/2 weight ratio so as to provide 20% by weight of a polymer concentration. This solution was determined for
13
C NMR spectrum under the condition of 67.20 MHz and 130° C. As a measuring device, a JEOL-GX270 (trade name) spectrometer manufactured by Nihon Densi K.K. in Japan can be used for example.
The term “isotactic pentad (I
5
)” as used herein refers to the is

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