Sizing paper by wet-end addition of water dispersibility polyester

Abstract

Water dispersible polyesters are used to treat and size paper by applying them at the wet-end of the paper process. The water dispersible polyesters can be used alone or with other chemicals typically used to treat or size paper in order to increase the paper's dry strength, wet strength, stiffness, water repellency, water resistance, and sizing properties. The water dispersible polyester is made with recycled polyethylene terephthalate or fresh glycol and polyacid or with virgin polyethylene terephthalate. The polyester sized paper is repulpable and recyclable. If the polyester size is used with traditional wet-strength resins, such as Kymene, the polyester-Kymene mixture will be repulpable and recyclable, whereas Kymene by itself is not easily repulpable nor recyclable in a paper mill process.

We claim:  
     
         1 . In a paper making process wherein dry paper is formed from a wet pulp slurry, the improvement comprising the steps of: 
 a) providing a water-dispersible polyester resin comprising a polyethylene terephthalate backbone, alkyl or aromatic group, and hydrophillic end groups; and    b) adding said polyester during the paper making process prior to the formation of the dry paper thereby enhancing the wet strength and repulpablity of the resulting paper product.    
     
     
         2 . The improved process of  claim 1  wherein said polyester is added to the pulp slurry at the wet end of the paper making process to provide internal sizing.  
     
     
         3 . The improved process of  claim 1  including the steps of: 
 c) providing an additional quantity of water-dispersible polyester and  
 d) applying said additional polyester as a surface size to wet paper formed during the paper making process.  
 
     
     
         4 . The improved process of  claim 1  wherein said water-dispersible polyester is made from a glycol and polyacid monomer.  
     
     
         5 . The improved process of  claim 3  whereas said water-dispersible polyester used as a surface size is made from a glycol and polyacid monomer.  
     
     
         6 . The improved process of  claim 1  wherein said water-dispersible polyester resin is made from recycled or virgin polyethylene terephthalate for the polyester portion of the polymer.  
     
     
         7 . The product of the process of  claim 1 .  
     
     
         8 . The paper making process of  claim 1  including the step of repulping a paper product made by said process.  
     
     
         9 . As an article of manufacture, a paper product having internal sizing which comprises a water dispersible polyester resin having a polyethylene terephthalate backbone, alkyl or aromatic groups, and hydrophilic end groups, said paper product exhibiting improved dry and wet strength properties.  
     
     
         10 . A paper product comprising: 
 a) cellulosic fibers and    b) an internal sizing comprising a water dispersible polyester.    
     
     
         11 . The product of  claim 10  wherein said cellulosic fibers are wood derived fibers. Cotton fiber and/or other non-wood fibers.  
     
     
         12 . The paper product of  claim 10  having an external sizing of a water dispersible polyester.  
     
     
         13 . The paper product of  claim 10  wherein the internal size of water dispersible polyester was present before dry paper formation in the range of 5 to 200 pounds of dry polyester per ton of dry fiber and the external size is present in the range of 163 pounds per thousand square feet of paper.  
     
     
         14 . An improvement of the paper making process comprising the steps of: 
 a) providing a cellulosic pulp fiber slurry prepared for forming paper;    b) providing a water dispersible polyester comprising the reaction production of 30%-70% by weight of a terephthalate polymer; 5%-40% by weight of a hydroxy functional compound having at least two hydroxyl groups; 1%-20% by weight of a carboxyl functional compound having at least two carboxyl groups and 10%-60% by weight of a hydrophic compound selected from the group consisting of C 6 -C 24  straight chain or branched fafty acid or treglyceride thereof; and,    c) adding said polyester in the ratio of 0.2 dry pound to 600 dry pounds of polyester per dry ton of fiber in the pulp slurry at the wet end of the paper making process.    
     
     
         15 . The improved process of  claim 14  wherein said polyester is added in the ratio of 5 to 200 dry pounds per dry ton of fiber.  
     
     
         16 . The improved process of  claim 14  including the additional step of applying said polyester resin to wet paper as a surface size.  
     
     
         17 . The improved process of  claim 14  including the step of adding alkyl ketone dimer or alkyl succinic anhydride to said polyester resin at the wet end as an internal size.  
     
     
         18 . The improved process of  claim 14  including the step of adding Kymene (or equivalent) to said polyester resin at the wet end as an internal size.  
     
     
         19 . The process of  claim 14  wherein said polyester size is added at more than one point in the paper making process.