Propylene-Based Spunbond Fabrics With Faster Crystallization Time

Abstract

A method of forming filaments can include: extruding a polymer composition to form a plurality of filaments, wherein the polymer composition comprises 75 wt % to 99 wt % of a propylene-ethylene copolymer, 0.5 wt % to 15 wt % of a propylene-based thermoplastic polymer, and 0.005 wt % to 1 wt % of a nucleator; and forming a spunbond material from the plurality of filaments.

The invention claimed is: 
     
         1 . A method comprising:
 extruding a polymer composition to form a plurality of filaments, wherein the polymer composition comprises 75 wt % to 99 wt % of a propylene-ethylene copolymer, 0.5 wt % to 15 wt % of a propylene-based thermoplastic polymer, and 0.005 wt % to 1 wt % of a nucleator; and   forming a spunbond material from the plurality of filaments.   
     
     
         2 . The method of  claim 1 , wherein the propylene-ethylene copolymer has an ethylene content of 1.5 wt % to 20 wt % and a propylene content of 80 wt % to 98.5 wt % based upon the total weight of the propylene-ethylene copolymer. 
     
     
         3 . The method of  claim 1 , wherein the propylene-ethylene copolymer has a melt flow rate (MFR) (ASTM D-1238, 2.16 kg weight @ 230° C.) of 10 g/10 min to 120 g/10 min. 
     
     
         4 . The method of  claim 1 , wherein the propylene-based thermoplastic polymer is a homopolymer of propylene. 
     
     
         5 . The method of  claim 1 , wherein the propylene-based thermoplastic polymer is a random propylene copolymer having a comonomer content of 4 wt % or less based upon the total weight of the random propylene copolymer. 
     
     
         6 . The method of  claim 1 , wherein the polymer composition consists of the propylene-ethylene copolymer, the propylene-based thermoplastic polymer, and the nucleator. 
     
     
         7 . The method of  claim 1 , wherein the polymer composition consists of the propylene-ethylene copolymer, the propylene-based thermoplastic polymer, the nucleator, and a slip aid. 
     
     
         8 . The method of  claim 1 , wherein the polymer composition further comprises one or more additives selected from the group consisting of a stabilizer, an antioxidant, a filler, a slip aid, a colorant, a mold release agent, a wax, and a processing oil. 
     
     
         9 . The method of  claim 1 , wherein the polymer composition is extruded through a spinneret at a melt temperature of 270° C. or less, thereby forming the plurality of filaments. 
     
     
         10 . A spunbond fabric made by the method of  claim 1 . 
     
     
         11 . A spunbond fabric having a machine direction (MD) and a cross direction (CD) comprising a polymer composition that comprises 75 wt % to 99 wt % of a propylene-ethylene copolymer, 0.5 wt % to 15 wt % of a propylene-based thermoplastic polymer, and 0.005 wt % to 1 wt % of a nucleator. 
     
     
         12 . The spunbond fabric of  claim 11 , wherein the propylene-ethylene copolymer has an ethylene content of 1.5 wt % to 20 wt % and a propylene content of 80 wt % to 98.5 wt % based upon the total weight of the propylene-ethylene copolymer. 
     
     
         13 . The spunbond fabric of  claim 11 , wherein the propylene-ethylene copolymer has a melt flow rate (MFR) (ASTM D-1238, 2.16 kg weight @ 230° C.) of 10 g/10 min to 120 g/10 min. 
     
     
         14 . The spunbond fabric of  claim 11 , wherein the propylene-based thermoplastic polymer is a homopolymer of propylene. 
     
     
         15 . The spunbond fabric of  claim 11 , wherein the propylene-based thermoplastic polymer is a random propylene copolymer having a comonomer content of 4 wt % or less based upon the total weight of the random propylene copolymer. 
     
     
         16 . The spunbond fabric of  claim 11 , wherein the polymer composition consists of the propylene-ethylene copolymer, the propylene-based thermoplastic polymer, and the nucleator. 
     
     
         17 . The spunbond fabric of  claim 11 , wherein the polymer composition consists of the propylene-ethylene copolymer, the propylene-based thermoplastic polymer, the nucleator, and a slip aid. 
     
     
         18 . The spunbond fabric of  claim 11 , wherein the polymer composition further comprises one or more additives selected from the group consisting of a stabilizer, an antioxidant, a filler, a slip aid, a colorant, a mold release agent, a wax, and a processing oil. 
     
     
         19 . The spunbond fabric of  claim 11 , wherein the spunbond fabric exhibits a permanent set of 20% or less in either or both of the MD and the CD, said permanent set being determined on the basis of said spunbond fabric having a basis weight of greater than 10 gsm. 
     
     
         20 . The spunbond fabric of  claim 11 , wherein the spunbond fabric exhibits either or both of (i) a 50% unloading force in the MD less than or equal to 2.5 N/5 cm, and (ii) a 50% unloading force in the CD less than or equal to 0.9 N/5 cm, said 50% unloading force determined on the basis of said spunbond fabric having a basis weight of 10 gsm or greater. 
     
     
         21 . The spunbond fabric of  claim 11 , wherein the spunbond fabric exhibits a hysteresis of 45% or less in either or both of the MD and the CD of the spunbond fabric, said hysteresis being determined on the basis of said spunbond fabric having a basis weight of 10 gsm or greater. 
     
     
         22 . The spunbond fabric of  claim 11 , wherein the spunbond fabric exhibits either or both of (i) a peak load of 20 N or less in the MD, and (ii) a peak load of 10 N or less in the CD, said peak loads being determined on the basis of said spunbond fabric having a basis weight of 10 gsm or greater. 
     
     
         23 . An article formed from the spunbond fabric of  claim 11 . 
     
     
         24 . The article of  claim 23 , wherein the article is selected from the group consisting of diaper tabs, side panels, leg cuffs, top sheet, back sheet, tapes, feminine hygiene articles, swim pants, infant pull up pants, incontinence wear components, and bandages.