High-Tenacity Drawn Fibers of a Polypropylene Composition with Improved Elongational Properties and Nonwovens

Abstract

High-tenacity fibers with improved elongational properties particularly suitable for nonwovens such as geotextiles include a polypropylene composition. The polypropylene composition includes from 0.2 wt % to 7 wt % of a rubber in a dispersed phase. The fibers have a tensile strength of at least 45 cN/tex measured in accordance to ISO 2062-B. The fibers may be made by a process including melt-spinning and drawing.

1 - 15 . (canceled) 
     
     
         16 . Drawn fiber comprising:
 a polypropylene composition, said polypropylene composition comprising a heterophasic propylene copolymer such that the polypropylene composition comprises a propylene polymer in a matrix phase and a rubber in a dispersed phase;   wherein the propylene polymer comprises propylene and at most 1 wt %, relative to a total weight of the polypropylene composition, of one or more comonomers selected from the group consisting of ethylene and C 4 -C 10  alpha-olefins;   characterized in that the polypropylene composition comprises the rubber in an amount from at least 0.2 wt % to at most 7 wt % relative to the total weight of the polypropylene composition and in that the drawn fiber has a tensile strength of at least 45 cN/tex measured in accordance to ISO 2062-B.   
     
     
         17 . The drawn fiber according to  claim 16 , characterized in that the rubber has an intrinsic viscosity of at least 2.0 dl/g, and of at most 5.5 dl/g measured in tetralin at 135° C. following ISO 1628. 
     
     
         18 . The drawn fiber according to  claim 16 , characterized in that the rubber is ethylene propylene rubber (EPR). 
     
     
         19 . The drawn fiber according to  claim 16 , characterized in that the polypropylene composition has a melt flow index of at least 3.0 g/10 min, the melt flow index being measured according to ISO 1133. 
     
     
         20 . The drawn fiber according to  claim 16 , characterized in that the polypropylene composition has a melt flow index of at most 15 g/10 min, the melt flow index being measured according to ISO 1133. 
     
     
         21 . The drawn fiber according to  claim 16 , characterized in that the polypropylene composition has a melt flow index of at least 3.0 g/10 min and at most 15 g/10 min, the melt flow index being measured according to ISO 1133. 
     
     
         22 . The drawn fiber according to  claim 16 , characterized in that the polypropylene composition comprises the rubber in an amount from at least 0.3 wt % relative to the total weight of the polypropylene composition. 
     
     
         23 . The drawn fiber according to  claim 16 , characterized in that the polypropylene composition comprises the rubber in an amount of at most 6 wt % relative to the total weight of the polypropylene composition. 
     
     
         24 . The drawn fiber according to  claim 16 , characterized in that the polypropylene composition comprises the rubber in an amount from at least 0.3 wt % and at most 6 wt % relative to the total weight of the polypropylene composition. 
     
     
         25 . The drawn fiber according to  claim 16 , characterized in that the drawn fiber has a toughness modulus of at least 100 MPa. 
     
     
         26 . The drawn fiber according to  claim 16 , wherein the drawn fiber comprises multiple filaments of the polypropylene composition, said filaments having a titer of at least 2 dtex and of at most 100 dtex. 
     
     
         27 . The drawn fiber according to  claim 16 , characterized in that the drawn fiber is produced of a polymer blend comprising:
 from 50 to 98 wt % by weight of the polymer blend, of a first polymer which is a propylene polymer comprising propylene and at most 1 wt %, relative to a total weight of the first polymer, of one or more comonomers selected from the group consisting of ethylene and C 4 -C 10  alpha-olefins; and   from 2 to 50 wt % by weight of the polymer blend, of a second polymer which is a heterophasic propylene copolymer comprising a propylene polymer and a rubber, wherein the rubber is present in an amount from 5 to 25 wt % relative to a total weight of the heterophasic propylene copolymer.   
     
     
         28 . The drawn fiber according to  claim 27 , characterized in that the rubber is present in an amount from 8 to 18 wt % relative to the total weight of the heterophasic propylene copolymer. 
     
     
         29 . The drawn fiber according to  claim 27 , characterized in that the polymer blend comprises from 2 to 20 wt % by weight of the polymer blend of the second polymer. 
     
     
         30 . The drawn fiber according to  claim 27 , characterized in that the first polymer is a propylene homopolymer comprising at least two propylene homopolymer fractions of different melt flow index, wherein a ratio of the melt flow index of the fraction with the highest melt flow index and the melt flow index of the fraction with the lowest melt flow index is in the range from 3 to 400. 
     
     
         31 . The drawn fiber according to  claim 27 , characterized in that the first polymer has one or more of the following properties:
 i. a xylene soluble content in the range from 1.5 wt % to 3.5 wt %; and/or   ii. a melt flow index of at least 3.0 dg/min, measured according to ISO 1133, condition L, at 230° C. and 2.16 kg; and/or   iii. a polydispersity index in the range of 4.0 to 5.5.   
     
     
         32 . The drawn fiber according to  claim 16 , characterized in that the drawn fiber is drawn at a draw ratio of at least 3. 
     
     
         33 . Nonwoven comprising the drawn fiber according to  claim 16 . 
     
     
         34 . A process for the production of drawn fiber comprising subjecting a polypropylene composition to melt-spinning and drawing at a draw ratio of at least 3 to obtain drawn fibers having a tensile strength of at least 45 cN/tex tex measured in accordance to ISO 2062-B;
 wherein the polypropylene composition comprises a heterophasic propylene copolymer such that the polypropylene composition comprises a propylene polymer in a matrix phase and a rubber in a dispersed phase;   wherein the propylene polymer comprises propylene and at most 1 wt %, relative to a total weight of the polypropylene composition, of one or more comonomers selected from the group consisting of ethylene and C 4 -C 10  alpha-olefins;   characterized in that the polypropylene composition comprises the rubber in an amount from at least 0.2 wt % to at most 7 wt % relative to the total weight of the polypropylene composition.   
     
     
         35 . A process for the production of drawn fibers comprising:
 a) providing a polypropylene composition to an extruder;   b) melt-spinning the polypropylene composition from a number of openings, to form molten filaments;   c) cooling the molten filaments obtained by step (c) to obtain solidified fibers; and   d) drawing said solidified fibers at a temperature of at least 70° C. and at most 150° C. and at a draw ratio of at least 3 to obtain fibers having a tensile strength of at least 45 cN/tex measured in accordance to ISO 2062-B;   wherein the polypropylene composition comprises a heterophasic propylene copolymer such that the polypropylene composition comprises a propylene polymer in a matrix phase and a rubber in a dispersed phase;   wherein the propylene polymer comprises propylene and at most 1 wt %, relative to a total weight of the polypropylene composition, of one or more comonomers selected from the group consisting of ethylene and C 4 -C 10  alpha-olefins;   characterized in that the polypropylene composition comprises the rubber in an amount from at least 0.2 wt % to at most 7 wt % relative to the total weight of the polypropylene composition.