Polypropylene fibres suitable for spunbonded non-woven fabrics

Abstract

A fibre for spunbonded fabrics comprising a propylene polymer composition (A) having an MFR (1) value from 6 to 150 g/10 min and being selected from (i) a crystalline propylene random copolymer or crystalline propylene polymer composition en containing at least 0.8% by weight of ethylene 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. 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 said composition containing at least 0.64 wt % of ethylene or a C 4 -C 10 a-olefin recurring unit and comprising: (1) 20-80 wt % of a crystalline propylene polymer containing up to 1.5 wt % of ethylene and/or C 4 -C 10 a-olefin; and (II) 20-80 wt % of a crystalline propylene random copolymer selected from (IIa) a copolymer of propylene with 0.8 to 10 wt % of ethylene and/or (IIb) a copolymer of propylene with 1.5 to 18 wt % of a C4-CIO a-olefin. Said polymer composition (A) is obtainable by way of chemical degradation of a precursor polymer composition (A) having MFR values (MFR (2)) of from 0.5 to 50 g/10 min, provided that the ratio of MFR (1) to MFR (2) be from 1.5 to 60. Propylene polymer composition (ii) as described above and non-woven fabrics that are prepared with the said fibres. The said fabric is useful for coverstock and diapers.

1 . A fibre for spunbonded non-woven fabrics comprising a propylene polymer composition (A) having an MFR value (MFR (1)) from 6 to 150 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 4% by weight and 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 at room temperature 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 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 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 propylene 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) be 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).  
 
   
     
     
         2 . The fibre of  claim 1  wherein composition (A) is polymer composition ii) having 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 fractionation with xylene to the xylene soluble fraction at room temperature higher than 8; said composition ii) comprising (percent by weight): 
 I) 20-80% of a crystalline propylene homopolymer or 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) be 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 be 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 composition (A) is obtained by chemical degradation of a precursor polymer composition (B) having an MFR value (MFR (2)) of from 0.5 to 50 g/10 min, provided that the ratio of MFR (1) to MFR (2) is from 1.5 to 60.  
     
     
         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 . A melt spin process for the production of a fibre for spunbonded non-woven fabrics comprising a propylene polymer composition (A) having MFR (1) values from 6 to 150 g/10 min and being selected from: 
 i) a crystalline propylene random copolymer or a crystalline polymer 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 4% 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 8; and  
 b) a copolymer or polymer composition containing more than 2.5 to 4.5 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 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 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 propylene 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).  
 
   
     
     
         6 . A propylene polymer composition having MFR values (MFR (1)) from 6 to 150 g/10 min, the composition 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 having a melting temperature of 155° C. or higher, a content of fraction soluble in xylene at room temperature lower than 4% 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 8; and    II) 20-80% of a crystalline propylene 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);  
 said polymer composition being obtained by way of chemical degradation of a precursor polymer composition (B) having MFR (2) values of from 0.5 to 50 g/10 min, provided that the ratio of MFR (1) to MFR (2) is from 1.5 to 60.  
   
     
     
         7 . 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 4% 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 8; and    b) a copolymer or polymer composition containing more than 2.5 to 4.5 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, and a ratio of a 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;    said copolymer or composition having a MFR value (MFR (1)) and being obtained by way of chemical degradation of a precursor polymer composition (B) having MFR (2) values of from 0.5 to 50 g/10 min, provided that the ratio of MFR (1) to MFR (2) is from 1.5 to 60.    
     
     
         8 . A process for the preparation of a propylene polymer composition having MFR values (MFR (1)) from 6 to 150 g/10 min, the composition 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 having a melting temperature of 155° C. or higher, a content of fraction soluble in xylene at room temperature lower than 4% 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 8; and    II) 20-80% of a crystalline propylene 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) be 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);  
 said polymer composition being obtained by way of chemical degradation of a precursor polymer composition (B) having MFR (2) values of from 0.5 to 50 g/10 min, provided that the ratio of MFR (1) to MFR (2) is from 1.5 to 60;  
 the process  
 comprising the following stages:  
   1) preparing the precursor polymer composition (B) by polymerising the monomers in one or more sequential stages, operating in each stage in the presence of the polymer formed and the catalyst used in the preceding stage, and dosing a molecular weight regulator in such amounts as to obtain the MFR (2) value for the precursor polymer composition (B) of from 0.5 to 50 g/10 min; and    2) subjecting the precursor composition (B) obtained in stage (1) to a degradation treatment with a degradation ratio, in terms of ratio of MFR (1) to MFR (2), from 1.5 to 60.    
     
     
         9 . A spunbonded non-woven fabric comprising fibres comprising a propylene polymer composition (A) having an MFR value (MFR (1)) from 6 to 150 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 4% by weight and 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 at room temperature 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 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 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 propylene 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) be 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) be 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 . A process for the preparation of a crystalline propylene random copolymer or a crystalline propylene polymer composition having a MFR value (MFR (1)) 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 4% 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 8; and    b) a copolymer or polymer composition containing more than 2.5 to 4.5 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, and a ratio of a 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;    said copolymer or composition being obtained by way of chemical degradation of a precursor polymer composition (B) having MFR (2) values of from 0.5 to 50 g/10 min, provided that the ratio of MFR (1) to MFR (2) is from 1.5 to 60;    the process comprising the following stages:    1) preparing the precursor polymer composition (B) by polymerising the monomers in one or more sequential stages, operating in each stage in the presence of the polymer formed and the catalyst used in the preceding stage, and dosing a molecular weight regulator in such amounts as to obtain an MFR (2) value for the precursor polymer composition (B) of from 0.5 to 50 g/10 min; and    2) subjecting the precursor composition (B) obtained in stage (1) to a degradation treatment with a degradation ratio, in terms of ratio of MFR (1) to MFR (2), from 1.5 to 60.