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
1999-12-08
2001-10-09
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S210000, C525S221000, C525S222000, C525S227000, C525S228000, C525S232000, C525S240000, C525S241000, C524S443000, C524S445000, C524S451000, C524S493000, C524S499000, C524S500000
Reexamination Certificate
active
06300419
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to propylene polymer compositions comprising a high crystalline polypropylene and a polyolefin elastomer. This invention relates particularly to a propylene polymer composition comprising a high crystalline polypropylene and a substantially linear ethylene polymer or a linear ethylene polymer having improved processability with a good balance of stiffness and toughness which demonstrates improved scratch resistance in injection molded articles.
BACKGROUND OF THE INVENTION
Polypropylene, especially highly isotactic polypropylene, has been used in many applications in the form of molded 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. The use of polypropylene polymers is expanding at an increasing rate in the fields of exterior and interior automotive trims, in electrical and electrical equipment device housing and covers as well as other household and personal articles.
However, polypropylene is poor or inadequate in heat resistance, stiffness, scratch resistance and impact resistance. These deficiencies are obstacles to opening up new applications for polypropylene, particularly applications which have traditionally been injection molded. In order to overcome these shortcomings, especially inadequate impact resistance, polypropylene has been blended with a rubbery elastic material such as ethylene-propylene copolymer rubber, ethylene-propylene-diene copolymer rubber or ethylene-butene copolymer rubber. For examples, see U.S. Pat. No. 5,391,618 which discloses low crystalline polypropylene polymer compositions comprising an ethylene alpha-olefin copolymer, U.S. Pat. No. 5,576,374 which discloses polypropylene polymer compositions comprising a substantially linear ethylene polymer and U.S. Pat. No. 5,639,829 which discloses propylene polymer compositions comprising an ethylene and 1-buttene random copolymer. However, while impact properties are improved these propylene polymer compositions do not achieve a good balance of stiffness and toughness.
In view of the deficiencies of the conventional propylene polymers and blends thereof, it would be highly desirable to provide a propylene polymer composition which exhibits improved processability with a good balance of stiffness and toughness which demonstrates improved scratch resistance in injection molded articles.
SUMMARY OF THE INVENTION
The present invention is such a desirable propylene polymer composition. The composition possesses a desirable balance of improved processability with a good balance of stiffness and toughness which demonstrates improved scratch resistance in injection molded articles. The propylene polymer composition of the present invention comprises from about 55 to about 80 parts by weight of a high crystalline isotactic propylene polymer having a crystalline phase determined by differential scanning calorimetry equal to or greater than about 62 weight percent based on the weight of the high crystalline propylene polymer; from about 20 to about 45 parts by weight of a substantially linear ethylene polymer, a linear ethylene polymer or combinations thereof wherein the substantially linear ethylene polymer and linear ethylene polymer are characterized as having a density of less than about 0.93 g/cm3, a molecular weight distribution, Mw/Mn, of less than about 3.0, and a Composition Distribution Branch Index of greater than 30 percent; from 0 to about 50 parts by weight of a filler; and from 0 to about 15 parts by weight of an additional polymer, parts by weight based on the weight of the total composition.
In another aspect, the present invention is a process for preparing a propylene polymer composition described hereinabove which exhibits a desirable balance of improved processability with a good balance of stiffness and toughness which demonstrates improved scratch resistance in injection molded articles wherein a high crystalline propylene polymer is blended with an effective amount of a substantially linear ethylene polymer, a linear ethylene polymer or combinations thereof, optionally a filler and optionally an additional polymer.
In a further aspect, the present invention involves a method of molding or extruding a propylene polymer blend composition described hereinabove.
In yet a further aspect, the invention involves molded or extruded articles of a propylene polymer blend composition described hereinabove. The propylene polymer compositions of the present invention are especially useful in the preparation of molded objects notably articles having large surfaces prepared by injection molding techniques requiring a good balance ol strength and toughness and good scratch resistance. Such properties are particularly desired for exterior and interior automotive trims, for example, bumper beams, bumper fascia, pillars, instrument panels and the like; in electrical and electrical equipment device housing and covers; as well as other household and personal articles, including, for example, appliance housings, housewares, freezer containers, and crates; lawn and garden furniture; building & construction sheet, etc.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Component (a) in the propylene polymer compositions of this invention is a high crystalline polypropylene. The high crystalline polypropylene suitable for use in this invention is well known in the literature and can be prepared by known techniques. In general, the high crystalline polypropylene is in the isotactic form, although other forms can also be used (c.g., syndiotactic or atactic). The high crystalline polypropylene used for the present invention is preferably a homopolymer of polypropylene or a copolymer, for example, a random or block copolymer, of propylene and an alpha-olefin, preferably a C
2
or C
4
to C
20
alpha-olefin. The alpha-olefin is present in the high crystalline polypropylene of the present invention in an amount of not more than 20 percent by mole, preferably not more than 15 percent, even more preferably not more than 10 percent and most preferably not more than 5 percent by mole.
Examples of the C
2
and C
4
to C
20
alpha-olefins for constituting the propylene and alpha-olefin 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.
In the present invention, a propylene homopolymer is the preferred high crystalline polypropylene.
The high crystalline polypropylene of the present invention 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 trichloride which contains as essential components titanium, magnesium and a halogen; as an organometallic 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.
High crystall
Hare Marie L.
Hoenig Wendy D.
Newton John
Sehanobish Kalyan
Silvis Harry Craig
Nutter Nathan M.
The Dow Chemical Company
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