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
2002-09-03
2004-08-31
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S224000, C524S451000
Reexamination Certificate
active
06784252
ABSTRACT:
This invention relates to blow moldable propylene polymer compositions and fabricated articles thereof.
BACKGROUND OF THE INVENTION
Polypropylene has been used in many applications in the form of injection molded and extruded articles, film, sheet, etc., because it is excellent in molding processability, toughness, moisture resistance, gasoline resistance, chemical resistance, has a low specific gravity, and is inexpensive. Advances in impact modification have further expanded the versatility and uses of propylene polymers. The use of propylene polymers is expanding at an increasing rate in the fields of exterior and interior automotive trims, in electrical and electrical equipment device housings and covers as well as other household and personal articles.
Automotive articles are ordinarily processed by injection molding. However, there are many components of automobiles wherein such parts are hollow and to manufacture these by injection molding is very difficult and expensive. Many such parts, particularly large parts, can conceivably be made by blow molding provided the polymer has adequate processing properties such as high melt strength and end product properties such as toughness, especially low temperature toughness. It is known that commercially available propylene polymers for injection molding and extrusion have excellent properties, but lack a combination of good melt strength and toughness. Higher toughness and good melt strength are attributes of grades of propylene polymers with higher molecular weights, however, melt processing machine outputs tend to be inversely related to polymer molecular weights.
Attempts to modify the melt strength and toughness of propylene polymers include cross-linking or branching induced by non-selective chemistries involving free radicals using peroxides or high energy radiation. For the reaction of polypropylene with peroxides see Journal of Applied Polymer Science, Vol. 61, 1395-1404 (1996). However, this approach does not work well in actual practice as the rate of chain scission tends to dominate the limited amount of chain coupling that takes place. For radiation of polypropylene to produce long branches for producing polypropylene film see U.S. Pat. No. 5,414,027. Another method to improve melt strength of propylene polymers is taught in U.S. Pat. No. 3,336,268 wherein polypropylene is bridged with sulfonamide groups. However, no improvement was demonstrated in the ability to blow mold bridged and unbridged propylene polymers.
It would be desirable to have a tough propylene polymer composition with adequate melt strength suitable for blow molding, especially for blow molding large automotive parts.
SUMMARY OF THE INVENTION
It has now been found that propylene polymer compositions wherein the propylene polymer is coupled with the coupling agents according to the practice of the invention can be blow molded into automotive articles. Preferably the propylene polymer is an impact propylene copolymer. Preferably, the coupling agent is a bis(sufonyl azide). Further, the coupled propylene polymer composition optionally comprises one or more of a polyolefin elastomer, a thermoplastic polymer or a filler.
The invention further involves a process to blow mold automotive articles from a coupled propylene polymer composition.
Preferably the automotive article is a seat back, a head rest, a knee bolster, glove box door, an instrument panel, a bumper facia, a bumper beam, a center console, an intake manifold, a spoiler, a side molding, a pillar, a door trim, an airbag cover, a HVAC duct, a spare tire cover, a fluid reservoir, a rear window shelf, a resonator, a trunk board or an arm rest.
DETAILED DESCRIPTION OF THE INVENTION
The blow molded automotive articles of the present invention are produced from a coupled propylene polymer composition. The coupled propylene polymer composition involves coupling of a propylene polymer using a coupling agent. The propylene polymer is a propylene homopolymer, preferably a propylene copolymer or most preferably an impact propylene copolymer.
The propylene polymer suitable for use in this invention is well known in the literature and can be prepared by various processes, for example, in a single stage or multiple stages, by such polymerization method as slurry polymerization, gas phase polymerization, bulk polymerization, solution polymerization or a combination thereof using a metallocene catalyst or a so-called Ziegler-Natta catalyst, which usually is one comprising a solid transition metal component comprising titanium. Particularly a catalyst consisting of, as a transition metal/solid component, a solid composition of titanium trichoride which contains as essential components titanium, magnesium and a halogen; as an organometalic component an organoaluminum compound; and if desired an electron donor. Preferred electron donors are organic compounds containing a nitrogen atom, a phosphorous atom, a sulfur atom, a silicon atom or a boron atom, and preferred are silicon compounds, ester compounds or ether compounds containing these atoms.
Propylene polymers are commonly made by catalytically reacting propylene in a polymerization reactor with appropriate molecular weight control agents. Nucleating agent may be added after the reaction is completed in order to promote crystal formation. The polymerization catalyst should have high activity and be capable of generating highly tactic polymer. The reactor system must be capable of removing the heat of polymerization from the reaction mass, so the temperature and pressure of the reaction can be controlled appropriately.
A good discussion of various polypropylene polymers is contained in
Modern Plastics Encyclopedia
/89, mid October 1988 Issue, Volume 65, Number 11, pp. 86-92, the entire disclosure of which is incorporated herein by reference. In general, the propylene polymer is in the isotactic form, although other forms can also be used (e.g., syndiotactic or atactic). The propylene polymer used for the present invention is a propylene homopolymer or a propylene copolymer of propylene and an alpha-olefin, preferably a C
2
, or C
4
to C
20
alpha-olefin, for example, a random or block copolymer or preferably an impact propylene copolymer.
Examples of the C
2
, and C
4
to C
20
alpha-olefins for constituting the propylene copolymer include ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-hexadodecene, 4-methyl-1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 3,3-dimethyl-1-butene, diethyl-1-butene, trimethyl-1-butene, 3-methyl-1-pentene, ethyl-1-pentene, propyl-1-pentene, dimethyl-1-pentene, methylethyl-1-pentene, diethyl-1-hexene, trimethyl-1-pentene, 3-methyl-1-hexene, dimethyl-1-hexene, 3,5,5-trimethyl-1-hexene, methylethyl-1-heptene, trimethyl-1-heptene, dimethyloctene, ethyl-1-octene, methyl-1-nonene, vinylcyclopentene, vinylcyclohexene and vinylnorbornene, where alkyl branching position is not specified it is generally on position 3 or higher of the alkene.
For random or block propylene copolymers, the alpha-olefin is present in an amount of not more than 15 weight percent, preferably not more than 12 weight percent, even more preferably not more than 9 weight percent and most preferably not more than 7 weight percent.
Impact propylene copolymers are commercially available and are well known within the skill in the art, for instance, as described by E. P. Moore, Jr in
Polypropylene Handbook
, Hanser Publishers, 1996, page 220-221 and U.S. Pat. Nos. 3,893,989 and 4,113,802. The term “impact propylene copolymer” is used herein to refer to heterophasic propylene copolymers where polypropylene is the continuous phase and an elastomeric phase is dispersed therein. Those of skill in the art recognize that this elastomeric phase may also contain crystalline regions, which for purposes of the current invention are considered part of the elastomeric phase. The impact propylene copolymer may be polypropylene and an elastomer physically blended, preferably the impact propylene copolymers result from an in-reactor process. U
Finlayson Malcolm F.
Novak Leo R.
Ramanathan Ravi
Traugott Thomas D.
Dow Global Technologies Inc.
Lee Rip A.
Wu David W.
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