Polypropylene fibres suitable for thermally bonded non-woven fabrics

Abstract

A fibre for thermal bonding comprising a propylene polymer composition having an MFR value from 4 to 50 g/10 min. The said composition is selected from (i) a crystalline propylene random copolymer or polymer composition containing at least 0.8% by weight of ethylene and optionally one or more C 4 -C 10 α-olefins and having a melting temperature of 155° C. or higher, a content of fraction soluble in xylene at room temperature lower than 5 wt %, a value of the ratio of the polymer fraction collected at the temperature range from 25° to 95° C. by TREF with xylene to the xylene soluble fraction, higher than 8; and (ii) a crystalline propylene polymer composition having a melting temperature of 153° C. or higher, a content of fraction soluble in xylene at room temperature lower than 10 wt % and containing at least 0.64 wt % of ethylene and/or C 4 -C 10 α-olefin recurring unit and comprising (I) 20-80 wt % of a crystalline propylene homopolymer and/or crystalline propylene random copolymer containing up to 1.5% by weight of ethylene and/or C 4 -C 10 α-olefin and (II) 20-80 wt % of a crystalline random copolymer of propylene with ethylene or a C 4 -C 10 α-olefin. A polymer composition having an MFR value from 4 to 50 g/10 min, an ethylene content of at least 0.64 wt % and comprising (A) 20-80 wt % of a crystalline propylene homopolymer or crystalline propylene random copolymer containing up to 1.5 wt % of ethylene and/or C 4 -C 10 α-olefin and (B) 20-80 wt % of a crystalline random copolymer of propylene with higher than 5 to 9 wt % of ethylene. Non-woven fabrics that are prepared with the said fibres are useful for hygienic applications.

1 . A fibre for thermal bonding comprising a propylene polymer composition (A) having an MFR value from 4 to 50 g/10 min, and being selected from: 
 i) a crystalline propylene random copolymer or a crystalline propylene polymer composition selected from: 
 a) a copolymer or polymer composition containing at least 0.8% by weight of ethylene and optionally at least one of C 4 -C 10  α-olefins and having a melting temperature of 155° C. or higher, a content of fraction soluble in xylene at room temperature lower than 5% by weight, a value of the ratio of the polymer fraction collected at the temperature range from 25° to 95° C. by temperature rising elution fractionation (TREF) with xylene to the xylene soluble fraction, higher than 8; and  
 b) a copolymer or polymer composition containing more than 2.5 wt % by weight of ethylene and optionally at least one of C 4 -C 10  α-olefins and having a melting temperature of 153° C. or higher, a content of fraction soluble in xylene at room temperature lower than 10% by weight and a value of the ratio of the polymer fraction collected at the temperature range from 25° to 95° C. by TREF with xylene to the xylene soluble fraction at room temperature, higher than 4; and  
   ii) a crystalline propylene polymer composition having a melting temperature of 153° C. or higher, a content of fraction soluble in xylene at room temperature lower than 10% by weight; the composition containing at least one of (1) at least 0.64 wt % of ethylene and (2) C 4 -C 10  α-olefin recurring unit and comprising (percent by weight): 
 I) 20-80% of at least one of a crystalline propylene homopolymer and a crystalline propylene random copolymer containing at least one of (i) up to 1.5% by weight of ethylene and (ii) C 4 -C 10  α-olefin; and  
 II) 20-80% of a crystalline random copolymer selected from: 
 IIa) a copolymer of propylene with 0.8 to 10% by weight of ethylene; provided that the difference in the ethylene content between polymer I) and polymer IIa) is at least 0.8 percentage unit with respect to the weight of the (co)polymer concerned; and  
 
 IIb) a copolymer of propylene with 1.5 to 18% by weight of a C 4 -C 10  α-olefin and optionally ethylene; provided that the difference in the comonomer content between polymer I) and polymer IIb) is at least 1.5 percentage units with respect to the weight of the (co)polymer concerned; and  
 IIc) a mixture of copolymer IIa) and copolymer IIb).  
   
   
   
       2 . The fibre of  claim 1  wherein the polymer composition ii) has a melting temperature of 155° C. or higher, a content of fraction soluble in xylene at room temperature lower than 5% by weight and a value of the ratio of the polymer fraction collected at the temperature range from 25° to 95° C. by TREF with xylene to the xylene soluble fraction higher than 8; the said composition containing at least one of (1) at least 0.64 wt % of ethylene and (2) C 4 -C 10  α-olefin recurring unit and comprising (percent by weight): 
 I) 20-80% of at least one of a crystalline propylene homopolymer and a crystalline propylene random copolymer containing at least one of (i) up to 1.5% by weight of ethylene and (ii) C 4 -C 10  α-olefin; and    II) 20-80% of a crystalline random copolymer selected from: 
 IIa) a copolymer of propylene with 0.8 to 5% by weight of ethylene; provided that the difference in the ethylene content between polymer I) and polymer IIa) is at least 0.8 percentage unit with respect to the weight of the (co)polymer concerned;  
 IIb) a copolymer of propylene with 1.5 to 12% by weight of a C 4 -C 10  α-olefin and optionally ethylene; provided that the difference in the comonomer content between polymer I) and polymer IIb) is at least 1.5 percentage units with respect to the weight of the (co)polymer concerned; and  
 IIc) a mixture of copolymer IIa) and copolymer IIb).  
   
   
   
       3 . The fibre of  claim 1  wherein the polymer composition has MFR values from 6 to 15 g/10 min.  
   
   
       4 . The fibre of  claim 1  wherein the difference in the ethylene content between polymer I) and polymer IIa) is at least 1 percentage unit with respect to the weight of the (co)polymer concerned.  
   
   
       5 . The fibre of  claim 1  having a value of bonding force at 150° C. of at least 300 cN.  
   
   
       6 . The fibre of  claim 5  obtained by a spinning process wherein the composition is subjected to an extrusion temperature of at most 275° C.  
   
   
       7 . The fibre of  claim 5  having a bonding force value of 300 to 800 cN and an MFR value of 50 g/10 min or less and being obtained by a spinning process wherein the composition is subjected to an extrusion temperature of at most 275° C.  
   
   
       8 . The fibre of  claim 6  wherein the extrusion temperature ranges from 260° to 275° C.  
   
   
       9 . A melt spin process for the production of a fibre for thermal bonding comprising a propylene polymer composition having an MFR value from 4 to 50 g/10 min and being selected from: 
 i) a crystalline propylene random copolymer or a crystalline propylene polymer composition selected from: 
 a) a copolymer or polymer composition containing at least 0.8% by weight of ethylene and optionally at least one of C 4 -C 10  α-olefins and having a melting temperature of 155° C. or higher, a content of fraction soluble in xylene at room temperature lower than 5% by weight, a value of the ratio of the polymer fraction collected at the temperature range from 250 to 95° C. by TREF with xylene to the xylene soluble fraction, higher than 8; and  
 b) a copolymer or polymer composition containing more than 2.5 wt % by weight of ethylene and optionally at least one of C 4 -C 10  α-olefins and having a melting temperature of 153° C. or higher, a content of fraction soluble in xylene at room temperature lower than 10% by weight and a value of the ratio of the polymer fraction collected at the temperature range from 25° to 95° C. by TREF with xylene to the xylene soluble fraction at room temperature, higher than 4; and  
   ii) a crystalline propylene polymer composition having a melting temperature of at least 153° C. or higher, a content of fraction soluble in xylene at room temperature lower than 9% by weight; the said composition containing at least one of (1) at least 0.64 wt % of ethylene and (2) C 4 -C 10  α-olefin recurring unit and comprising (percent by weight): 
 I) 20-80% of at least one of a crystalline propylene homopolymer and a crystalline propylene random copolymer containing at least one of (i) up to 1.5% by weight of ethylene and (ii) C 4 -C 10  α-olefin; and:  
 II) 20-80%, preferably from 30-70%, of a crystalline random copolymer selected from: 
 IIa) a copolymer of propylene with 0.8 to 10% by weight of ethylene; provided that the difference in the ethylene content between polymer I) and polymer IIa) is at least 0.8 percentage unit with respect to the weight of the (co)polymer concerned;  
 IIb) a copolymer of propylene with 1.5 to 18% by weight of a C 4 -C 10  α-olefin and optionally ethylene; provided that the difference in the comonomer content between polymer I) and polymer IIb) is at least 1.5 percentage units with respect to the weight of the (co)polymer concerned; and  
 IIc) a mixture of copolymer IIa) and copolymer IIb.  
 
   
   
   
       10 . The process of  claim 9  wherein polymer composition ii) has a melting temperature of 155° C. or higher, a content of fraction soluble in xylene at room temperature lower than 5% by weight, a value of the ratio of the polymer fraction collected at the temperature range from 25° to 95° C. by TREF with xylene to the xylene soluble fraction, higher than 8; the said composition containing at least one of (1) at least 0.64 wt % of ethylene and (2) C 4 -C 10  α-olefin recurring unit and comprising (percent by weight): 
 I) 20-80% of at least one of a crystalline propylene homopolymer and a crystalline propylene random copolymer containing at least one of (i) up to 1.5% by weight of ethylene and (ii) C 4 -C 10  α-olefin; and    II) 20-80% of a crystalline random copolymer selected from: 
 IIa) a copolymer of propylene with 0.8 to 5% by weight of ethylene; provided that the difference in the ethylene content between polymer I) and polymer IIa) is at least 0.8 percentage unit with respect to the weight of the (co)polymer concerned;  
 IIb) a copolymer of propylene with 1.5 to 12% by weight of a C 4 -C 10  α-olefin and optionally ethylene; provided that the difference in the comonomer content between polymer I) and polymer IIb) is at least 1.5 percentage units with respect to the weight of the (co)polymer concerned; and  
 IIc) a mixture of copolymer IIa) and copolymer IIb).  
   
   
   
       11 . The process of  claim 9  wherein the composition is extruded at a temperature of at most 275° C.  
   
   
       12 . The process of  claim 11  wherein the composition is extruded at a temperature ranging from 260° to 275° C.  
   
   
       13 . A thermally bonded non-woven fabric comprising fibres comprising a propylene polymer composition (A) having an MFR value from 4 to 50 g/10 min, and being selected from: 
 i) a crystalline propylene random copolymer or a crystalline propylene polymer composition selected from: 
 a) a copolymer or polymer composition containing at least 0.8% by weight of ethylene and optionally at least one of C 4 -C 10  α-olefins and having a melting temperature of 155° C. or higher, a content of fraction soluble in xylene at room temperature lower than 5% by weight, a value of the ratio of the polymer fraction collected at the temperature range from 25° to 95° C. by temperature rising elution fractionation (TREF) with xylene to the xylene soluble fraction, higher than 8; and  
 b) a copolymer or polymer composition containing more than 2.5 wt % by weight of ethylene and optionally at least one of C 4 -C 10  α-olefins and having a melting temperature of 153° C. or higher, a content of fraction soluble in xylene at room temperature lower than 10% by weight and a value of the ratio of the polymer fraction collected at the temperature range from 25° to 95° C. by TREF with xylene to the xylene soluble fraction at room temperature, higher than 4; and  
   ii) a crystalline propylene polymer composition having a melting temperature of at least 153° C., a content of fraction soluble in xylene at room temperature lower than 10% by weight: the composition containing at least one of (1) at least 0.64 wt % of ethylene and (2) C 4 -C 10  α-olefin recurring unit and comprising (percent by weight): 
 I) 20-80% of at least one of a crystalline propylene homopolymer and a crystalline propylene random copolymer containing at least one of (i) up to 1.5% by weight of ethylene and (ii) C 4 -C 10  α-olefin: and  
 II) 20-80% of a crystalline random copolymer selected from: 
 IIa) a copolymer of propylene with 0.8 to 10% by weight of ethylene; provided that the difference in the ethylene content between polymer I) and polymer IIa) is at least 0.8 percentage unit with respect to the weight of the (co)polymer concerned; and  
 IIb) a copolymer of propylene with 1.5 to 18% by weight of a C 4 -C 10  α-olefin and optionally ethylene; provided that the difference in the comonomer content between polymer I) and polymer IIb) is at least 1.5 percentage units with respect to the weight of the (co)polymer concerned: and  
 IIc) a mixture of copolymer IIa) and copolymer IIb).  
 
   
   
   
       14 . A composite non-woven fabric comprising two or more layers wherein at least one layer is made of thermally bonded non-woven fabric comprising fibres comprising a propylene polymer composition (A) having an MFR value from 4 to 50 g/10 min, and being selected from: 
 i) a crystalline propylene random copolymer or a crystalline propylene polymer composition selected from: 
 a) a copolymer or polymer composition containing at least 0.8% by weight of ethylene and optionally at least one of C 4 -C 10  α-olefins and having a melting temperature of 155° C. or higher, a content of fraction soluble in xylene at room temperature lower than 5% by weight a value of the ratio of the polymer fraction collected at the temperature range from 25° to 95° C. by temperature rising elution fractionation (TREF) with xylene to the xylene soluble fraction, higher than 8; and  
 b) a copolymer or polymer composition containing more than 2.5 wt % by weight of ethylene and optionally at least one of C 4 -C 10  α-olefins and having a melting temperature of 153° C. or higher, a content of fraction soluble in xylene at room temperature lower than 10% by weight and a value of the ratio of the polymer fraction collected at the temperature range from 25° to 95° C. by TREF with xylene to the xylene soluble fraction at room temperature, higher than 4; and  
   ii) a crystalline propylene polymer composition having a melting temperature of 153° C. or higher, a content of fraction soluble in xylene at room temperature lower than 10% by weight; the composition containing at least one of (1) at least 0.64 wt % of ethylene and (2) C 4 -C 10  α-olefin recurring unit and comprising (percent by weight): 
 I) 20-80% of at least one of a crystalline propylene homopolymer and a crystalline propylene random copolymer containing at least one of (i) up to 1.5% by weight of ethylene and (ii) C 4 -C 10  α-olefin; and  
 II) 20-80% of a crystalline random copolymer selected from: 
 IIa) a copolymer of propylene with 0.8 to 10% by weight of ethylene; provided that the difference in the ethylene content between polymer I) and polymer Ia) is at least 0.8 percentage unit with respect to the weight of the (co)polymer concerned; and  
 IIb) a copolymer of propylene with 1.5 to 18% by weight of a C 4 -C 10  α-olefin and optionally ethylene; provided that the difference in the comonomer content between polymer I) and polymer IIb) is at least 1.5 percentage units with respect to the weight of the (co)polymer concerned; and  
 
 IIc) a mixture of copolymer IIa) and copolymer IIb).  
   
   
   
       15 . A process for the production of non-woven fabric comprising thermalbonding fibres which comprises a propylene polymer composition (A) having an MFR value from 4 to 50 g/10 min, and being selected from: 
 i) a crystalline propylene random copolymer or a crystalline propylene polymer composition selected from: 
 a) a copolymer or polymer composition containing at least 0.8% by weight of ethylene and optionally at least one of C 4 -C 10  α-olefins and having a melting temperature of at least 155° C., a content of fraction soluble in xylene at room temperature lower than 5% by weight, a value of the ratio of the polymer fraction collected at the temperature range from 25° to 95° C. by temperature rising elution fractionation (TREF) with xylene to the xylene soluble fraction, higher than 8; and  
 b) a copolymer or polymer composition containing more than 2.5 wt % by weight of ethylene and optionally at least one of C 4 -C 10  α-olefins and having a melting temperature of 153° C. or higher, a content of fraction soluble in xylene at room temperature lower than 10% by weight and a value of the ratio of the polymer fraction collected at the temperature range from 25° to 95° C. by TREF with xylene to the xylene soluble fraction at room temperature, higher than 4; and  
   ii) a crystalline propylene polymer composition having a melting temperature of 153° C. or higher a content of fraction soluble in xylene at room temperature lower than 10% by weight: the composition containing at least one of (1) at least 0.64 wt % of ethylene and (2) C 4 -C 10  α-olefin recurring unit and comprising (percent by weight): 
 I) 20-80% of at least one of a crystalline propylene homopolymer and a crystalline propylene random copolymer containing at least one of (i) up to 1.5% by weight of ethylene and (ii) C 4 -C 10  α-olefin; and  
 II) 20-80% of a crystalline random copolymer selected from: 
 IIa) a copolymer of propylene with 0.8 to 10% by weight of ethylene; provided that the difference in the ethylene content between polymer I) and polymer IIa) is at least 0.8 percentage unit with respect to the weight of the (co)polymer concerned; and  
 
 IIb) a copolymer of propylene with 1.5 to 18% by weight of a C 4 -C 10  α-olefin and optionally ethylene; provided that the difference in the comonomer content between polymer I) and polymer IIb) is at least 1.5 percentage units with respect to the weight of the (co)polymer concerned; and  
 IIc) a mixture of copolymer Ia) and copolymer IIb).  
   
   
   
       16 . A crystalline propylene polymer composition having an MFR value from 4 to 50 g/10 and at least one of an ethylene and a C 4 -C 10  α-olefin content of at least 0.64 wt % and comprising (percent by weight): 
 I) 20-80% of a crystalline propylene homopolymer or crystalline propylene random copolymer containing at least one of (i) up to 1.5% by weight of ethylene and (ii) C 4 -C 10  α-olefin; and    II) 20-80% of a crystalline random copolymer of propylene with higher than 5 to 9% by weight of ethylene;    the composition having a melting temperature of at least 153° C. and a content of fraction soluble in xylene at room temperature lower than 9% by weight.    
   
   
       17 . The composition of  claim 16  having MFR values from 6 to 15 g/10 min.  
   
   
       18 . A process for the polymerisation preparing the crystalline propylene polymer composition having an MFR value from 4 to 50 g/10 and at least one of an ethylene and a C 4 -C 10  α-olefin content of at least 0.64 wt % and comprising (percent by weight): 
 I) 20-80% of a crystalline propylene homopolymer or crystalline propylene random copolymer containing at least one of (i) up to 1.5% by weight of ethylene and (ii) C 4 -C 10  α-olefin; and    II) 20-80% of a crystalline random copolymer of propylene with higher than 5 to 9% by weight of ethylene;    the composition having a melting temperature of 153° C. or higher and a content of fraction soluble in xylene at room temperature lower than 9% by weight; the process being carried out in at least two separate subsequent stages, wherein in at least two polymerisation stages the relevant monomers are polymerised to form polymer I) and in the other stage(s) the relevant monomers are polymerised to form polymer II), operating in each stage, except the first step, in the presence of the polymer formed and the catalyst used in the preceding stage.    
   
   
       19 . The fibre of  claim 7  wherein the extrusion temperature ranges from 260° to 275° C.