Polyolefins and uses thereof

Details Polyolefins and uses thereof Polyolefins and uses thereof

1999-01-20

2002-02-19

Resan, Stevan A. (Department: 1773)

Stock material or miscellaneous articles

Composite

Of addition polymer from unsaturated monomers

C428S035100, C428S034900, C428S515000, C428S523000, C428S910000, C525S240000, C526S348100, C526S351000, C526S943000

Reexamination Certificate

active

06348272

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to polyolefins, especially polypropylenes and their uses.
DESCRIPTION OF THE PRIOR ART
As known in the art, syndiotactic polymers have a unique stereochemical structure in which monomeric units having enantiomorphic configuration of the asymmetrical carbon atoms follow each other alternately and regularly in the macromolecular main chain. Syndiotactic polypropylene was first disclosed by Natta et al. in U.S. Pat. No. 3,258,455. The Natta group obtained syndiotactic polypropylene by using a catalyst prepared from titanium trichloride and diethyl aluminum monochloride. A later patent to Natta et al., U.S. Pat. No. 3,305,538, discloses the use of vanadium triacetylacetonate or halogenated vanadium compounds in combination with organic aluminum compounds for producing syndiotactic polypropylene.
U.S. Pat. No. 3,364,190 to Emrick discloses a catalyst system composed of finely divided titanium or vanadium trichloride, aluminum chloride, a trialkyl aluminum and a phosphorus-containing Lewis base as producing syndiotactic polypropylene. U.S. Pat. No. 4,892,851 disclosed a metallocene catalyst for producing highly crystalline syndiotactic polyolefins.
As disclosed in these patent references and as known in the art, the structure and properties of syndiotactic polypropylene differ significantly from those of isotactic polypropylene. The isotactic structure is typically described as having the methyl groups attached to the tertiary carbon atoms of successive monomeric units on the same side of a hypothetical plane through the main chain of the polymer, e.g., the methyl groups are all above or below the plane. Using the Fischer projection formula, the stereochemical sequence of isotactic polypropylene is described as follows:
Another way of describing the structure is through the use of NMR. Bovey's NMR nomenclature for an isotactic pentad is . . . mmmm . . . with each “m” representing a “meso” dyad or successive methyl groups on the same side in the plane. As known in the art, any deviation or inversion in the structure of the chain lowers the degree of isotacticity and crystallinity of the polymer.
In contrast to the isotactic structure, syndiotactic polymers are those in which the methyl groups attached to the tertiary carbon atoms of successive monomeric units in the chain lie on alternate sides of the plane of the polymer. Using the Fischer projection formula, the structure of a syndiotactic polymer is designated as:
In NMR nomenclature, this pentad is described as . . . rrrr . . . in which each “r” represents a “racemic” dyad, i.e., successive methyl groups on alternate sides of the plane.
The percentage of r dyads in the chain determines the degree of syndiotacticity of the polymer. Syndiotactic polymers are crystalline and, like the isotactic polymers, are insoluble in xylene.
This crystallinity distinguishes both syndiotactic and isotactic polymers from an atactic polymer that is soluble in xylene. Atactic polymer exhibits no regular order of repeating unit configurations in the polymer chain and forms essentially a waxy product. While it is possible for a catalyst to produce all three types of polymer, it is desirable for a catalyst to produce predominantly syndiotactic or isotactic polymer with some atactic block fractions.
PCT/EP97/03649 (filed on 10th July 1997) of the present applicants describes a new syndiotactic/atactic block homopolyolefin and particularly a new syndiotactic/atactic block homopolypropylene. PCT/EP97/03649 also describes a catalyst and process for preparing syndiotactic/atactic block polyolefins, and more particularly syndiotactic/atactic block polypropylene. The catalyst and process can each be adapted to produce a polymer with differing syndio-/atactic block ratios.
SUMMARY OF THE INVENTION
The present invention provides use of syndiotactic/atactic block polypropylene whereby the properties thereof, especially the mechanical properties, are exploited. The syndiotactic/atactic block polypropylene has a combination of plastic properties conferred by the syndiotactic block and elastomeric properties conferred by the atactic block and may be regarded as a member of the “thermoplastic elastomer” family of polymers.
In one aspect, the present invention provides use of syndiotactic/atactic block polypropylene as a modifier of a polyolefin, such as isotactic and/or copolymeric polypropylene and/or other polyolefins. The modified polyolefin or polypropylene formed thereby may be capable of moulding, for example by extrusion, injection or compression and can be used, for example, in high impact resistance applications such as automobile parts, electronic appliances, packaging and sports goods. Accordingly, there is further provided a high impact resistance polyolefin such as a polypropylene, comprising a dispersion of syndiotactic/atactic block polypropylene in a continuous phase comprising isotactic and/or copolymeric polypropylene. Preferably, the amount of syndiotactic/atactic block polypropylene is in the range 3 to 50%, preferably 5 to 15% by weight of the polypropylene. It is thought that the syndiotactic/atactic block polypropylene forms discrete dispersed particles in the continuous phase. In this way, the syndiotactic/atactic block polypropylene functions in the same way as rubber or elastomers in high impact polystyrene or as EPDM (ethylene propylene diene monomer such as a 1,4-hexadiene, or dicyclopentadiene or 5-ethylidene norbornene) particles in polypropylene.
In a further aspect, the present invention provides use of syndiotactic/atactic block polypropylene as a component in an adhesive composition. There is further provided an adhesive composition comprising a syndiotactic/atactic block polypropylene and at least one component selected from a wax, and a tackifying and/or reinforcing resin such as HERCOTAC 205 or MBG 212 (both from Hercules). Such adhesive compositions may be used, for example, in book binding applications. In such applications it is preferred that the components of the adhesive are selected so as to give a storage modulus G′ in the range 3×10
6
to 5×10
7
and a soft phase glass transition temperature in the range 5 to 30° C.
In a further aspect the present invention provides use of a syndiotactic/atactic block polypropylene as a component in a shock absorber. There is further provided a shock absorber comprising syndiotactic/atactic block polypropylene. In this application, the syndiotactic/atactic block polypropylene exhibits elasticity without rebound. It is found that rebound decreases as the molecular weight of the polypropylene increases. The syndiotactic/atactic block polypropylene appears to act in an analogous way to butyl rubber and could therefore be used in its place, wherever mechanical properties are concerned. The chemical properties of syndiotactic/atactic block polypropylene differ from those of butyl rubber. In particular, syndiotactic/atactic block polypropylene requires no further vulcanization during processing.
The shock absorber may further comprise other components known by those skilled in this art for use therein, such as carbon black, oils, inorganic fillers, organic fillers, other polymers and foaming and processing agents. Typical applications of such shock absorbers include footwear soles, silent-block (noise absorber or damper) and any absorber or damper required between vibrating parts.
Preferably, the shock absorber is for use at room temperature, for example 20° C., and above.
In a further aspect, the present invention provides use of a syndiotactic/atactic block polypropylene as a component in a waterproof membrane. There is further provided a waterproof membrane comprising a sheet of syndiotactic/atactic block polypropylene modified with carbon black and/or a UV absorber and/or an antioxidant, and/or a weather resistance improver. Preferably, the amount of carbon black in the waterproof membrane is in the range 0.5% to 50%, more preferably 3% to 30%, depending on the grade of carbon black. It is found that carbon blac

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