Paper articles exhibiting water resistance and method for making same

Abstract

This invention relates to a process for preparing sized paper and paperboard which incorporates in the paper and paperboard at the size press size a composition comprising one or more “hydrophobic polymers” wherein hydrophobic polymers, the amount of such polymers and the weight ratio of starch to such polymer in the composition are selected such that the paper and paper board exhibits a Cobb Value equal to or less than about 25 and to a sized paper or paperboard web formed by the process.

1 . A process of making a paper or paperboard, comprising contacting a paper or paperboard web at a size press with a composition comprising at least one hydrophobic polymer at an amount that is selected such that the paper or paper board exhibits a Cobb value that is equal to or less than about 25 and a contact angle equal to or greater than about 120°.  
   
   
       2 . The process of  claim 1 , wherein the contact angle is equal to or greater than 123°.  
   
   
       3 . The process of  claim 1 , wherein the amount of said polymer is at least about 0.4 wt % based on the dry weight of the paper or paperboard.  
   
   
       4 . The process of  claim 1 , wherein the amount of said polymer is from about 0.4 to about 3.0 wt % based on the dry weight of the paper or paperboard.  
   
   
       5 . The process of  claim 1 , wherein said composition comprises at least one sizing agent  
   
   
       6 . The process of  claim 1 , wherein said composition comprises starch.  
   
   
       7 . The process of  claim 6 , wherein a weight ratio of starch to hydrophobic polymer picked up by the paper or paperboard web is less than about 3 to about 1.  
   
   
       8 . The process of  claim 1 , wherein the hydrophobic polymer is selected from the group consisting of a styrene acrylic emulsion, styrene acrylic acid, styrene maleic anhydride, alkylated melamine wherein the alkyl moiety is branched or linear and has at least about 7 carbon atoms, paraffin wax, polyurethane, hydrophobically-modified starch polyethylene, polymethylmetharcylate, alkyl ketene dimer, alkenyl ketene dimer, and rosin.  
   
   
       9 . The process of  claim 1 , wherein the hydrophobic polymer is a combination of one or more alkylated melamines wherein the alkyl moiety is branched or linear and has at least about 7 carbon atoms and one or more paraffin waxes.  
   
   
       10 . The process of  claim 1 , further comprising contacting the paper or paperboard web with at least one microsphere.  
   
   
       11 . A paper or paperboard made by the process of  claim 10 .  
   
   
       12 . A paper or paperboard made by the process of  claim 1 .  
   
   
       13 . The process according to  claim 1 , comprising contacting the paper or paperboard web at a size press with a composition comprising at least one sizing agent and at least one hydrophobic polymer at a weight ratio of sizing agent to hydrophobic polymer picked up by the paper or paperboard web that is less than about 3 to about 1; and wherein the paper or paper board exhibits a Cobb value that is equal to or less than about 25.  
   
   
       14 . The process according to  claim 13 , wherein the sizing agent is starch.  
   
   
       15 . A paper or paperboard made by the process according to  claim 13 .  
   
   
       16 . The process according to  claim 13 , wherein the amount of said polymer is at least about 0.4 wt % based on the dry weight of the paper or paperboard.  
   
   
       17 . The process according to  claim 1 , comprising contacting the paper or paperboard web at a size press with a composition comprising starch and at least one hydrophobic polymer at a weight ratio of starch to hydrophobic polymer picked up by the paper or paperboard web that is less than about 3 to about 1; and wherein 
 the paper or paper board exhibits a Cobb value that is equal to or less than about 25; and    the paper or paper board exhibits a contact angle that equal to or greater than about 128°.    
   
   
       18 . The process according to  claim 17 , wherein the amount of said polymer is at least about 0.4 wt % based on the dry weight of the paper or paperboard.  
   
   
       19 . A paper or paperboard made by the process according to  claim 17 .  
   
   
       20 . The process according to  claim 1 , wherein the at least one hydrophobic polymer is a plurality of hydrophobic polymers.