Method for treating the surface of a web

Abstract

In the method for treating the surface of the web, liquid is added on the surface of a paper or paperboard web (W), possibly with other constituents. The absorbency of the surface of the paper or paperboard web is increased before liquid is brought on the surface of the web or simultaneously with bringing the liquid on the surface of the web. The method is used for wetting the surface of the web before calendering, or for coating the web in surface sizing or pigmenting. The absorbency of the surface is increased before bringing the liquid for example by means of a corona treatment, a flame treatment, an ozonization or by adding steam.

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         11 . A method for treating the surface of a paper web containing cellulosic fibers, the web traveling in a paper machine or a finishing machine for paper in a running direction and being of a type showing web surface hydrophobicity after it has been formed and at least partially dried, said method comprising the steps of: 
 reducing said web surface hydrophobicity and increasing an absorbency of the surface of the web when the web has already been formed and at least partially dried;    subsequently to or simultaneously with reducing said web surface hydrophobicity and increasing the absorbency, applying liquid to the surface of the web, and    subsequently to applying liquid to the surface of the web, effecting finishing on the web.    
     
     
         12 . A method according to  claim 11 , wherein said step of reducing web surface hydrophobicity and increasing the absorbency comprises an energy treatment, with which new polar groups are produced in material on the surface of the web, and the step of applying liquid to the surface of the web takes place subsequently to the energy treatment.  
     
     
         13 . A method according to  claim 12 , wherein said energy treatment is a corona treatment.  
     
     
         14 . A method according to  claim 12 , wherein said energy treatment is a flame treatment.  
     
     
         15 . A method according to  claim 12 , wherein said energy treatment is ozonization.  
     
     
         16 . A method according to  claim 12 , wherein said energy treatment comprises subjecting the surface of the web to at least two different types of treatments selected from the group consisting of corona treatment, flame treatment and ozonization.  
     
     
         17 . A method according to  claim 11 , wherein said step of reducing web surface hydrophobicity and increasing the absorbency comprises directing steam on said surface of said web, and the step of applying liquid to the surface of the web takes place subsequently to directing steam on the surface of the web.  
     
     
         18 . A method according to  claim 17 , wherein in the step of applying liquid to the surface of the web the web is wetted by adding liquid on the surface of the web in a spray wetting underneath the web, and the step of effecting finishing on the web is calendering the web.  
     
     
         19 . A method according to  claim 18 , wherein calendering the web comprises heating said surface of the web by means of a heated smooth calender surface.  
     
     
         20 . A method according to  claim 12 , wherein in the step of applying liquid to the surface of the web the web is wetted, and the step of effecting finishing on the web is calendering the web.  
     
     
         21 . A method according to  claim 20 , wherein in the step of applying liquid to the surface of the web the liquid is added on the surface of the web in a spray wetting underneath the web.  
     
     
         22 . A method according to  claim 20 , wherein calendering the web comprises heating said surface of the web by means of a heated smooth calender surface.  
     
     
         23 . A method according to  claim 12 , wherein in the step of applying liquid to the surface of the web the liquid is added on the surface of the web along with other constituents intended as a coating of the web, and the step of effecting finishing on the web is drying and calendering the web.  
     
     
         24 . A method according to  claim 17 , wherein in the step of applying liquid to the surface of the web the liquid is added on the surface of the web along with other constituents intended as a coating of the web, and the step of effecting finishing on the web is drying and calendering the web.  
     
     
         25 . A method according to  claim 21 , wherein said step of reducing web surface hydrophobicity and increasing the absorbency comprises using underpressure affecting the surface, which underpressure is effected through the web from an opposite side of the web simultaneously with applying liquid to the surface of the web.  
     
     
         26 . A method according to  claim 25 , wherein the underpressure is effected at least with an underpressure impulse, which is produced by means of a position and/or shape of a member placed against or in the vicinity of the web.  
     
     
         27 . A method according to  claim 26 , wherein said step of reducing web surface hydrophobicity and increasing the absorbency comprises using successive underpressure and overpressure impulses.  
     
     
         28 . A method according to  claim 25 , wherein in the step of applying liquid to the surface of the web the web is wetted, and the step of effecting finishing on the web is calendering the web.  
     
     
         29 . A method according to  claim 28 , wherein in the step of applying liquid to the surface of the web the liquid is added on the surface of the web in a spray wetting underneath the web.  
     
     
         30 . A method according to  claim 28 , wherein calendering the web comprises heating said surface of the web by means of a heated smooth calender surface.  
     
     
         31 . A method according to  claim 21 , wherein said step of reducing web surface hydrophobicity and increasing the absorbency comprises increasing the absorbency of the surface in a profiled manner in the transverse direction of the web  
     
     
         32 . A method according to  claim 12 , wherein the energy treatment comprises profiling the effect of the energy treatment.  
     
     
         33 . A method according to  claim 21 , wherein in said step of reducing web surface hydrophobicity and increasing the absorbency, the fibres are exposed or surface sized on the surface of the web.  
     
     
         34 . A method according to  claim 12 , wherein in said energy treatment, the fibres are exposed or surface sized on the surface of the web.