Non-woven mat and method of producing same

Abstract

A mat having a highly uniform porosity distribution is produced by consolidating 15 or more layers of melt blown webs (or the like) having different orientations. Control over the porosity is provided by using webs that exhibit a narrow, unimodal distribution of fiber diameters over the bulk of its distribution, such as in the top 80%. A compliance of the mats can be chosen by selecting a number and orientation of the webs. It is thus possible to produce mats that are good candidates for vascular grafts, for example. The uniformity of the porosity within the range of 6 μm to 30 μm permits seeding of the vascular graft with endothelial and smooth muscle cells. The mats have the demonstrated ability to retain, and support growth of, smooth muscle cells and endothelial cells.

1 - 21 . (canceled) 
     
     
         22 . A vascular graft comprising a mat formed as a cylinder, wherein the mat has a compliance close to that of a blood vessel, and wherein the mat is formed from 15 to 50 web sections of a same web stacked and compressed together, wherein:
 the web is formed of oriented, extruded polymer strands contact-fused at tangle points, the strands in a given web section being parallel to one another thereby defining an orientation of the given web section, the orientations of at least two web sections differing by an angle between 3° and 90°; and   at least the smallest 80% of strands have a mean strand diameter between 2 and 4.5 μm with a standard deviation within 2 μm and strand diameters are unimodal with a regression coefficient measure of fit to a normal distribution of at least 0.96.   
     
     
         23 . The vascular graft according to  claim 22  wherein a luminal inner wall of the mat is seeded with endothelial cells, and/or an abluminal outer wall is seeded with smooth muscle cells. 
     
     
         24 . The vascular graft according to  claim 23  wherein the inner wall of the cylindrical mat is covered with ingrown endothelial cells that retain their characteristic cell phenotype, and/or the outer wall is covered with ingrown smooth muscle cells that retain their characteristic cell phenotype. 
     
     
         25 . The graft of  claim 22  wherein the mat is formed of a hollow cylinder having an average compliance between 7.4×10 −2 %/mmHg and 9.4×10 −2 %/mmHg. 
     
     
         26 . The graft of  claim 22  wherein the polymer comprises a polycondensation polymer. 
     
     
         27 . The graft of  claim 26  wherein the polycondensation polymer is one of: polyethylene terephthalate (PET), polycarbonate (PC), polytrimethylene terephthalate (PTT), and polylactic acid (PLLA), or a combination thereof. 
     
     
         28 . The graft of  claim 22  wherein the polycondensation polymer is a polyester, and the orientations of adjacent web sections are orthogonal. 
     
     
         29 . The graft of  claim 22  wherein the web is produced of PET strands and has a porosity network with about 90% of the pores having a dimension less than 20 μm. 
     
     
         30 . The graft of  claim 29  wherein at least 50% of the pores have a mean diameter between 5 and 17 μm. 
     
     
         31 . The graft of  claim 25  wherein:
 (a) the polymer comprises a polyester; 
 (b) the orientations of adjacent web sections are orthogonal; and, 
 (c) the web has a porosity network with about 90% of the pores having a dimension less than 20 μm. 
 
     
     
         32 . The graft of  claim 25  wherein:
 (a) the polymer comprises polyethylene terephthalate; 
 (b) the orientations of adjacent web sections are orthogonal; and, 
 (c) the web has a porosity network with about 90% of the pores having a dimension less than 20 μm, and wherein at least 50% of the pores have a mean diameter between 5 and 17 μm.