Boosting the cross-machine direction shrinkage and extensibility of a fiber product

Abstract

The present invention concerns a method for modifying a fiber network of a fiber web, typically made of a cellulose-based pulp, in order to increase the drying shrinkage as well as boost the cross-machine direction (CD) extensibility of the thus prepared fiber product. The method includes the steps of imposing a three-dimensional pattern in the wet fiber web, and drying the web using evaporative drying while allowing the web to shrink without major restraints. The pattern is imposed on the web in the forming section or after the forming section, before evaporative drying, while utilizing the wet elongation of the web for the shapes of the pattern, thereby not affecting the width of the wet web. The invention also concerns the formed fiber product having an increased CD extensibility.

1 - 15 . (canceled) 
     
     
         16 . A method of modifying the fiber network of a fiber web, the method comprising:
 imposing a three-dimensional pattern in a wet fiber web; and   drying the wet fiber web using evaporative drying while allowing the web to shrink;   wherein the imposing of the three-dimensional pattern on the wet fiber web is done before the evaporative drying, and   wherein the imposing of the three-dimensional pattern on the wet fiber web provides the three-dimensional pattern through the wet elongation of the wet fiber web without affecting at least the width of the wet fiber web.   
     
     
         17 . The method of  claim 16 , wherein the three-dimensional pattern is imposed on the web by pressing the web between two surfaces of which one or both surfaces are shaped. 
     
     
         18 . The method of  claim 16 , wherein the imposed three-dimensional pattern on the web is a machine-direction (MD) corrugation of the web, or another pattern that provides waves and ridges in the web in the machine-direction. 
     
     
         19 . The method of  claim 16 , wherein the dry matter content of the wet fiber web during the imposing of the pattern is 20-60% by weight. 
     
     
         20 . The method of  claim 16 , wherein the fiber web comprises mechanical, chemi-mechanical, thermochemimechanical, semi-chemical or chemical pulp, either bleached or unbleached, from wood or non-wood origin, from either virgin or recycled sources, or their mixture. 
     
     
         21 . The method of  claim 16 , wherein the fiber web has been formed from pulp into a web with a basis weight of >100 g/m 2 . 
     
     
         22 . The method of  claim 16 , wherein the fiber web has been formed from a fiber pulp that has been mechanically pretreated by one or more pretreatment steps selected from refining, kneading or other high consistency treatment, or by addition of cellulose microfibrils, nanofibrils or nanocrystals (CMF, CNF, CNC), or carboxymethyled cellulose (CMC), the pre-treatment steps comprising at least one treatment step that induces fiber deformations selected from curls, kinks, dislocations or microcompressions. 
     
     
         23 . The method of  claim 16 , further comprising one or more treatment steps, where one or more chemicals are added to a pulp suspension or applied on or impregnated in the wet fiber web, or applied as mixtures of multilayers, or as cellulose solvents, the one or more chemicals being selected from natural or modified polymeric materials with or without cross-linking agents, micro or nanofibrillated cellulosic material, hemicellulose or cellulose, carboxymethyl cellulose, starch, xyloglucan, alginate, gelatin, agar, chitosan, guargum, polyamideamine epichlorohydrin (PAE), polyurethane, polylactic acid (PLA), polyvinylacetate (PVAc), polyvinylamine (PVAm), polyethyleneimine (PEI), or polyacrylamide (PAM). 
     
     
         24 . The method of  claim 16 , further comprising a step of smoothing out the three-dimensional pattern at a dry matter content of 55-95% by weight. 
     
     
         25 . The method of  claim 24 , wherein the smoothing step takes place by crushing the three-dimensional pattern. 
     
     
         26 . The method of  claim 24 , wherein the smoothing step takes place by crushing using a machine-direction (MD) compacting step, said MD compacting step being a step, wherein the fiber web is placed in contact with a contracting surface. 
     
     
         27 . The method of  claim 16 , wherein the evaporative drying is carried out by cylinder drying, impingement drying, or air flotation drying, until a solids content of >80% by weight is achieved. 
     
     
         28 . The method according to  claim 16 , wherein drying induced shrinkage in the drying step is boosted by using contracting rollers. 
     
     
         29 . The method according to  claim 16 , wherein the fiber web has been formed from pulp into a web with a basis weight of 120-250 g/m 2 . 
     
     
         30 . A fiber product produced according to the method of  claim 16 , wherein the fiber product has a CD extensibility higher than 15%. 
     
     
         31 . The fiber product according to  claim 30 , wherein the fiber product has a basis weight of >100 g/m 2 .