Extrusion Blow-Molded Articles and Process for Their Production

Abstract

The present application relates to extrusion blow-molded articles comprising a polypropylene layer, said polypropylene layer consisting of a polypropylene composition comprising a specific random copolymer of propylene and at least one comonomer. The present application also relates to a process for the production of such extrusion blow-molded articles.

1 .- 15 . (canceled) 
     
     
         16 . A process for the production of an extrusion blow-molded article, said process comprising the steps of
 (a) polymerizing propylene and at least one comonomer with a metallocene-based polymerization catalyst to obtain a random copolymer of propylene and at least one comonomer, wherein the random copolymer has a molecular weight distribution, defined as Mw/Mn, of at most 4.0, a percentage of 2,1-insertions of at least 0.1%, relative to the total number of propylene molecules in the chain, and comprises at most 7.0 wt %, relative to the total weight of said random copolymer, of the at least one comonomer;   (b) melt-extruding a polypropylene composition comprising the random copolymer prepared in step (a) to form a parison of said molten polypropylene composition;   (c) clamping the parison into a mold so that the parison is closed off at both ends to form a clamped-off parison;   (d) injecting a gas under pressure into said clamped-off parison to obtain an expanded parison having the shape of the mold;   (e) finally cooling and ejecting the extrusion blow-molded article.   
     
     
         17 . The process according to  claim 16 , characterized in that in step (b) the polypropylene composition is melt-extruded at a temperature of the molten polypropylene composition of at least Tmelt+5° C., with Tmelt being the melting temperature of the polypropylene composition determined by DSC. 
     
     
         18 . The process according to  claim 16 , wherein in step (e) the polypropylene composition is extruded at a temperature of the molten polypropylene composition of at most Tmelt+50° C., provided that the temperature of the molten polypropylene composition is at most 180° C., with Tmelt being the melting temperature of the polypropylene composition determined by DSC. 
     
     
         19 . The process according to  claim 16 , wherein the extrusion blow-molded container and has a wall thickness of at least 300 μm and of at most 2000 μm 
     
     
         20 . The process according to  claim 16 , wherein the random copolymer of propylene and at least one comonomer comprises at least 0.5 wt % and at most 7.0 wt %, relative to the total weight of said random copolymer, of the at least one comonomer. 
     
     
         21 . The process according to  claim 16 , wherein the random copolymer of propylene and at least one comonomer is a random copolymer of propylene and at least one alpha-olefin different from propylene. 
     
     
         22 . The process according to  claim 21 , wherein the alpha-olefin is selected from the group consisting of ethylene, butene-1, pentene-1, hexene-1 and 4-methyl-pentene-1. 
     
     
         23 . The process according to  claim 16 , wherein the random copolymer of propylene and at least one comonomer has a melt flow rate of at least 3.0 dg/min, determined according to ISO 1133, condition L, at 230° C. and 2.16 kg. 
     
     
         24 . The process according to  claim 16 , wherein the random copolymer of propylene and at least one comonomer has a melt flow rate of at most 20 dg/min, determined according to ISO 1133, condition L, at 230° C. and 2.16 kg. 
     
     
         25 . The process according to  claim 16 , wherein the random copolymer of propylene and at least one comonomer has a content of mmmm pentads of at least 90%. 
     
     
         26 . The process according to  claim 16 , wherein the random copolymer of propylene and at least one comonomer has a melt flow rate of at least 8 dg/min and at most 20 dg/min, determined according to ISO 1133, condition L, at 230° C. and 2.16 kg. 
     
     
         27 . The process according to  claim 16 , wherein the random copolymer of propylene and at least one comonomer is a metallocene propylene random copolymer. 
     
     
         28 . The process according to  claim 27 , wherein the metallocene propylene random copolymer has at least two propylene polymer fractions. 
     
     
         29 . The process according to  claim 28 , wherein the at least two propylene polymer fractions differ in comonomer content, melt flow index, or both. 
     
     
         30 . The process according to  claim 27 , wherein the polypropylene composition comprises one or more thermoplastic polymers different from the metallocene propylene random copolymer. 
     
     
         21 . The process according to  claim 27 , wherein the polypropylene composition comprises at least 50 wt. %, relative to a total weight of the polypropylene composition, of the metallocene propylene random copolymer. 
     
     
         22 . The process according to  claim 16 , wherein the polypropylene composition comprises a nucleating agent.