Nonwoven webs with enhanced loft and process for forming such webs

Abstract

The present invention relates to a process of forming a soft bulky nonwoven web from a batt using thermobonding and to a soft bulky nonwoven web with a bond impression pattern and shape. The process comprises several steps including feeding a batt to a nip between first and second surface of first and second roller, where at least the first of the surfaces comprises spaced apart bonding protrusions surrounded by recessed areas. The bonding protrusions and the bond impression shape in the web exhibit a ratio of the greatest measurable width to the greatest measurable length of at least 1:2.5 and the perimeters thereof comprise a convex portion. The bonding protrusions are symmetric and/or have a certain angle to the machine direction.

1 . A process for the forming of a bonded nonwoven web from a batt characterized in that it comprises the steps of
 a. providing a batt comprising heat bondable individual fibers;   b. feeding said batt along a machine direction to a nip between a first and a second surface of a first and a second roller, respectively;   i. whereby at least the first of said surfaces comprises spaced apart bonding protrusions surrounded by recessed areas,   ii. the plurality of bond protrusions forms a regular pattern and   iii. said bonding protrusions exhibiting
 A. the ratio of the greatest measurable width W to the greatest measurable length L of at least 1:2.5, 
 B. while the perimeter of the shape of the surface of the bonding protrusions comprise a convexly formed portion, 
   c. feeding the batt into said nip,
 i. thereby compressing said batt in said nip between said first and said second roller, 
 ii. and thereby affecting the fiber positioning by said bonding protrusions which are either asymmetric or exhibit a shape tilt angle α T  of between 1° and 40° relative to the machine direction; 
   d. bonding said batt in said nip by contacting the web with said bonding protrusions of said first surface and said second surface thereby forming consolidating bonds;   e. removing said web from said nip.   
     
     
         2 . The process according to  claim 1 , wherein the batt comprises individual essentially endless fibres. 
     
     
         3 . The process according to  claim 1 , wherein the batt is spunlaid. 
     
     
         4 . The process according to  claim 1 , wherein the batt comprises monocomponent fibres. 
     
     
         5 . The process according to  claim 1 , wherein the batt comprises multicomponent, preferably bicomponent fibres. 
     
     
         6 . The process according to  claim 5 , wherein at least part of the bicomponent fibres have the core/sheath or side/side structure. 
     
     
         7 . The process according to  claim 1 , wherein at least a part of the fibres contain polyolefines. 
     
     
         8 . The process according to  claim 1 , wherein at least a part of the fibres comprise materials selected form the group consisting of polypropylene, polyethylene, copolymers, aliphatic polyesters, thermoplastic polysaccharides, other biopolymers, or mixtures thereof, dyes, or additives altering the surface properties of the material. 
     
     
         9 . The process according to  claim 1 , operated at machine direction speeds of at least 300 m/min, preferably at least 600 m/min and more preferably at least 800 m/min of the batt. 
     
     
         10 . The process according to  claim 1 , wherein the convexly formed portion of said bonding protrusions has various radii. 
     
     
         11 . The process according to  claim 1 , wherein said perimeter of the surface of said bonding protrusions comprises concave portions. 
     
     
         12 . The process according to  claim 1 , wherein the perimeter of the surface of said bonding protrusions contains several pairs of convex-concave parts. 
     
     
         13 . The process according to  claim 1 , wherein the width of individual bonding protrusions varies along their length direction. 
     
     
         14 . The process according to  claim 1 , wherein said bonding protrusions are not of mirror or rotational symmetric shape. 
     
     
         15 . The process according to  claim 1 , wherein said bonding protrusions are oriented so that the MD direction forms an angle with the shape line of the shape of the surface of said bonding protrusions form a shape tilt angle α T  of between 5° and 15°, more preferably between 8° and 12°. 
     
     
         16 . The process according to  claim 1 , wherein said bonding protrusions are arranged in a pattern so that on the surface of the roll there are lines which do not intersect any individual bonding protrusion, but intersect the axis in the CD direction perpendicular to MD. 
     
     
         17 . The process according to  claim 16 , wherein said lines which do not intersect any individual bonding protrusion and form an angle with the cross-machine direction CD, extending perpendicularly to the machine direction, β A  greater than 45°, preferably between 50° and 90°, even more preferably between 60° and 90°. 
     
     
         18 . The process according to  claim 1 , wherein said bonding protrusions are oriented so that the angle γ P  between the CD direction and the orientation of the shorter side of the bonding protrusion which smaller than 4°, preferably smaller than 3° and even more preferably smaller than 2.5°. 
     
     
         19 . The process according to  claim 1 , wherein the number of individual bonding protrusions per cm 2  on said surfaces is lower than 11. 
     
     
         20 . The process according to  claim 1 , wherein the ratio of the bonding protrusions on said surface relative to the total area of the surface is between 4% and 18%, more preferably between 6% and 16% and even more preferably between 8% and 14%. 
     
     
         21 . A nonwoven web comprising heat bondable fibres and comprising a plurality of bond impressions;
 a. wherein the plurality of bond impressions forms a regular pattern and   b. wherein the bond impressions have a bond shape
 i. with the bond shape perimeter comprising a convex portion and 
 ii. a greatest measurable length and a greatest measurable width,
 1. wherein an aspect ratio of the greatest measurable length to the greatest measurable width is at least 2.5; 
 
 iii. and wherein the bond shape is asymmetric or is oriented such that a line intersecting the bond shape perimeter along which the greatest measurable length exists and intersects an axis lying on the surface along the machine direction to form an angle α T  of between 1 degree and 40 degrees. 
   
     
     
         22 . The web according to  claim 21 , wherein the web comprises individual essentially endless fibres. 
     
     
         23 . The web according to  claim 21 , wherein the web is spunlaid. 
     
     
         24 . The web according to  claim 21 , wherein the web comprises monocomponent fibres. 
     
     
         25 . The web according to  claim 21 , wherein the web comprises multicomponent, preferably bicomponent fibres. 
     
     
         26 . The web according to  claim 25 , wherein at least part of the bicomponent fibres have the core/sheath or side/side structure. 
     
     
         27 . The web according to  claim 21 , wherein at least a part of the fibres contain polyolefines. 
     
     
         28 . The web according to  claim 21 , wherein at least a part of the fibres comprise materials selected form the group consisting of polypropylene, polyethylene, copolymers, aliphatic polyesters, thermoplastic polysaccharides, other biopolymers, or mixtures thereof, dyes, or additives altering the surface properties of the material. 
     
     
         29 . The web according to  claim 21 , wherein the convexly formed portion of said bond shape has various radii. 
     
     
         30 . The web according to  claim 21 , wherein said perimeter of the surface of said bond shape comprises concave portions. 
     
     
         31 . The web according to  claim 21 , wherein the perimeter of said bond shapes contains several pairs of convex-concave parts. 
     
     
         32 . The web according to  claim 21 , wherein the width of individual bond shapes varies along their length direction. 
     
     
         33 . The web according to  claim 21 , wherein said bond shapes are not of mirror or rotational symmetric shape. 
     
     
         34 . The web according to  claim 21 , wherein said bond shapes are oriented so that the MD direction forms an angle with the shape line of said bond shapes form a shape tilt angle α T  of between 5° and 15°, more preferably between 8° and 12°. 
     
     
         35 . The web according to  claim 21 , wherein said bond shapes are arranged in a pattern so that there are lines which do not intersect any individual bond shape, but intersect the axis in the CD direction perpendicular to MD. 
     
     
         36 . The web according to  claim 35 , wherein said lines which do not intersect any individual bond shape and form an angle with the cross-machine direction CD, extending perpendicularly to the machine direction, β A  greater than 45°, preferably between 50° and 90°, even more preferably between 60° and 90°. 
     
     
         37 . The web according to  claim 21 , wherein said bond shapes are oriented so that the angle γ P  between the CD direction and the orientation of the shorter side of the bond shapes which is smaller than 4°, preferably smaller than 3° and even more preferably smaller than 2.5°. 
     
     
         38 . The web according to  claim 21 , wherein the number of individual bond shapes per cm 2  is lower than 11. 
     
     
         39 . The web according to  claim 21 , wherein the ratio of the bond shapes on said surface relative to the total area of the surface is between 4% and 18%, more preferably between 6% and 16% and even more preferably between 8% and 14%. 
     
     
         40 . The web according to the  claim 21 , wherein the ratio of strength in the MD direction to the CD direction is less than 2.5. 
     
     
         41 . The web according to the  claim 21 , wherein the fabric is hydrophilic. 
     
     
         42 . The web according to the  claim 21 , wherein the basis weight of the web is less than 150 gsm, preferably less than 20 gsm more preferably between 12 gsm and 17 gsm. 
     
     
         43 . The web according to  claim 21 , wherein the bondshapes of at least some of mutually adjacent bonds identify venturi passageways between each other.