Polypropylene Processing with Reduced Cycle Time in Injection-Stretch-Blow Moulding
This invention discloses the use of metallocene-produced polypropylene to prepare single- or multi-layer articles by injection-stretch blow moulding with a reduced cycle time, said article having excellent optical properties and rigidity.
1 - 10 . (canceled)
11 . A method for the further production of a hollow article comprising:
(a) providing an isotatic propylene polymer having a melt flow index MFI within the range of 2-10 grams per 10 minutes produced by the polymerization of propylene in the presence of a metallocene catalyst system having C1 or C2 symmetry;
(b) subjecting said isotatic propylene polymer to an injection-stretch-blow molding operation to mold said polymer into a hollow article having an exterior wall formed of said polymer; and
(c) recovering said article from said injection-stretch-blow molding operation.
12 . The method of claim 11 wherein said isotatic propylene polymer is produced by polymerization of propylene in the presence of a metallocene catalyst system comprising a metallocene component of the formula:
R″ s (CpR′ k )(C′pR′ ″k )MQ 2 (I)
wherein:
(CpR′k) is a cyclopentadienyl or substituted cyclopentadienyl, each R′ is the same or different and is hydrogen or a hydrocarbyl radical comprising an alkyl, alkenyl, aryl, alkylaryl, or arylalkyl radical containing from 1 to 20 carbon atoms or two carbon atoms are joined together to form a C 4 -C 6 ring and k is from 0-4;
(C′pR′″ k ′) is a substituted or unsubstituted fluorenyl, each R′″ is the same or different and is hydrogen or a hydrocarbyl radical comprising an alkyl, alkeny, aryl, alkylaryl, or arylalkyl radical containing from 1 to 20 carbon atoms and k ′ is from 0-8;
the substituents R′ and R′″ rings 20 are selected to impart C1 or C2 symmetry to the compound;
R″ is a structural bridge between the cyclopentadienyl and the fluorenyl groups rings to impart stereorigidity and is a C 1 -C 4 alkylene radical, a dialkyl germanium or silicon or siloxane radical, or an alkyl phosphine or amine radical;
Q is a hydrocarbyl radical comprising aryl, alkyl, alkenyl, alkylaryl, or aryl alkyl radical having from 1-20 carbon atoms, a hydrocarboxy radical having from 1-20 carbon atoms or halogen and can be the same or different from each other; and
M is a transition metal from Group IVb of the Periodic Table.
13 . The method of claim 11 wherein said isotatic propylene polymer is an isotatic propylene homopolymer or an isotatic copolymer of propylene and ethylene having an ethylene content of 10 weight percent or less.
14 . The method of claim 13 wherein said isotatic propylene polymer is a copolymer of propylene and ethylene.
15 . The method of claim 14 wherein said copolymer has an ethylene content of 4 weight percent or less.
16 . The method of claim 12 wherein the transmission metal M is selected from a group consisting of zirconium, titanium, and hafnium.
17 . The method of claim 16 wherein C p R′ k is a substituted cyclopentadienyl group and C′ p R′″ k is an unsubstituted fluornyl group.
18 . The method of claim 17 wherein C p R′ k is a 3,5 disubstituted cyclopentadienyl group.
19 . The method of claim 18 wherein said metallocene catalyst component is isopropylidene-(3-tert-butyl-5-methyl-cyclopentadienyl)(fluorenyl) zirconium dichloride.
20 . The method of claim 11 wherein said article is produced by the operation of said injection-stretch-blow molding operation with a cycle time which is shorter than the cycle time achieved by the injection-stretch-blow molding of a corresponding propylene polymer produced by the polymerization of propylene in the presence of Ziegler Natta catalyst.
21 . The method of claim 11 wherein the article produced by the injection-stretch-blow molding operation has a rigidity which is greater than the rigidity of a corresponding propylene polymer produced by the polymerization of propylene in the presence of a Ziegler Natta catalyst.
22 . The method of claim 11 wherein said injection-stretch-blow molding operation is carried out in a multi phase process comprising;
(a) providing a preform of said propylene polymer by injection molding of said propylene polymer in a multi cavity mold and thereafter cooling the preform to room temperature;
(b) transporting said preform to a blow molding machine and reheating the preform in said blow molding machine by reflective radiant heat;