Web smoothness improvement process

Abstract

The present invention provides a process for improving smoothness of a web surface by subjecting the web surface to an untreated smooth roll traveling at a different speed than the web and thereby producing heat generated by friction to plasticize the very top fibers in the mat. Surprisingly, the inventors found that no abrasive was needed to generate the amount of heat required to achieve the smoothness gain.

What is claimed is:  
     
         1 . A process for increasing the smoothness of the surface of a fibrous web surface of paper or paperboard comprising: 
 subjecting the web surface to a smooth untreated roll, wherein the difference between the rotating speed of said roll and the rotating speed of the web is sufficient enough so as to generate heat by friction and thereby plasticize the top fibers in the mat.    
     
     
         2 . The process according to  claim 1 , comprising reducing the roughness of the web surface by a maximum of 125 Sheffield units.  
     
     
         3 . The process according to  claim 1 , wherein the web has two opposite surfaces and the process comprises subjecting both web surfaces to the smooth roll.  
     
     
         4 . The process according to  claim 1 , wherein the smooth uncoated roll is a simple steel roll.  
     
     
         5 . The process according to  claim 1 , wherein the roll rotates in the same direction as the web.  
     
     
         6 . The process according to  claim 1 , wherein the roll rotates in a direction opposite from that of direction of the web.  
     
     
         7 . The process according to  claim 1 , wherein the paper or paperboard is for printing, packaging or wrapping.  
     
     
         9 . The process according to  claim 1 , wherein the web is subjected to the smooth uncoated roll before coating, size press or calendering.  
     
     
         10 . The process according to  claim 1 , which process uses a soft backing roll.  
     
     
         11 . The process according to  claim 11 , wherein the soft backing roll runs at the same speed and direction as the web.  
     
     
         12 . A process for treating a surface of a fibrous web of paper or board for printing, packaging or wrapping, without substantially increasing the density of the web comprising: 
 subjecting the web surface to a smooth untreated roll, wherein the difference between the rotating speed of said roll and the rotating speed of the web is sufficient enough so as to generate heat by friction and thereby plasticize the top fibers in the mat.    
     
     
         13 . The process according to  claim 12 , comprising reducing the roughness of the web surface by a maximum of 125 Sheffield units.  
     
     
         14 . The process according to  claim 12 , comprising contacting the web surface with a smooth roll moving with a sufficiently velocity relative to the web surface such that surface fibers on said web surface melts.  
     
     
         15 . The process according to  claim 12 , wherein the web has two opposite surfaces and the process comprises subjecting both web surfaces to the smooth roll.  
     
     
         16 . The process according to  claim 12 , wherein the smooth uncoated roll is a simple steel roll.  
     
     
         17 . The process according to  claim 12 , wherein the roll rotates in the same direction as the web.  
     
     
         18 . The process according to  claim 12 , wherein the roll rotates in a direction opposite from that of direction of the web.  
     
     
         19 . The process according to  claim 12 , wherein the web is subjected to the smooth uncoated roll before coating, size press or calendering.  
     
     
         20 . The process according to  claim 12 , which process uses a soft backing roll.  
     
     
         21 . The process according to  claim 20 , wherein the soft backing roll runs at the same speed and direction as the web.  
     
     
         22 . A process for increasing the smoothness of the surface of a fibrous web of paper or board without loss of bulk comprising: 
 subjecting the web surface to an untreated smooth roll in a dry state; and    bringing the web in contact with said roll, wherein the difference between the rotating speed of said roll and the rotating speed of the web is sufficient enough so as to generate heat by friction and thereby plasticize the top fibers in the mat.    
     
     
         23 . The process according to  claim 22 , comprising reducing the roughness of the web surface by a maximum of 125 Sheffield units.  
     
     
         24 . The process according to  claim 22 , comprising contacting the web surface with a smooth roll moving with a sufficiently velocity relative to the web surface such that surface fibers on said web surface melts.  
     
     
         25 . The process according to  claim 22 , wherein the web has two opposite surfaces and the process comprises subjecting both web surfaces to the smooth roll.  
     
     
         26 . The process according to  claim 22 , wherein the smooth uncoated roll is a simple steel roll.  
     
     
         27 . The process according to  claim 22 , wherein the roll rotates in the same direction as the web.  
     
     
         28 . The process according to  claim 22 , wherein the roll rotates in a direction opposite from that of direction of the web.  
     
     
         29 . The process according to  claim 22 , wherein the paper or paperboard is for printing, packaging or wrapping.  
     
     
         30 . The process according to  claim 29 , wherein the web is subjected to the smooth uncoated roll before coating, size press or calendering.