Paper products and methods for applying chemical additives to fibers in the manufacture of paper

Abstract

In the manufacture of tissue products from cellulose fibers, it is often desirable to enhance physical properties by the addition of chemical additives, including for example debonding agents. These additives serve to prevent or disrupt interfiber or intrafiber hydrogen bonding. Depending upon the nature of the chemical additive, debonding agents may also act as softening agents. During the papermaking process, chemical additives of this type can be added to fiber slurries in the wet end of a papermaking machine. Alternately, such additives may be sprayed upon tissue layers during manufacture, prior to assembly into multi-ply tissue structures. The chemical additives may include quaternary ammonium salts or organofunctional polysiloxanes. The chemical additives may include quaternary ammonium salts or organofunctional polysiloxanes or polysiloxanes. Some of the quaternary salts which may be used include salts comprised in part of imidazoline heterocyclic nitrogen ring structures.

What is claimed:  
     
         1 . A tissue product, comprising: 
 (a) cellulosic fibers, and    (b) an adsorbable chemical debonding additive, wherein the additive comprises at least two quaternary ammonium salts, the quaternary ammonium salts comprising a first imidazoline quaternary ammonium salt having a first charge density and a second imidazoline ammonium salt having a second charge density, the first charge density being greater than about 0.9 meq/g and the second charge density being less than about 0.7 meq/g when the ammonium salts are in a neat form, and wherein the quaternary ammonium salts comprise between about 10% and 60% by weight of the additive when water is not present.    
     
     
         2 . The tissue product of  claim 1 , wherein the quaternary ammonium salts comprise between about 40% and about 60% by weight of the additive when water is not present.  
     
     
         3 . The tissue product of  claim 1 , in which the debonding additive comprises by weight, 
 (i) about 19-24% of the first imidazoline quaternary ammonium salt; and    (ii) about 15-20% of the second imidazoline quaternary ammonium salt.    
     
     
         4 . The tissue product of  claim 1 , in which the additive further comprises of between about 12-19% lubricant by weight.  
     
     
         5 . The tissue product of  claim 1 , in which the additive further comprises about 20-70% by weight nonionic surfactants.  
     
     
         6 . The tissue product of  claim 1 , in which the additive comprises between about 34% and about 44% by weight of the imidazoline quaternary ammonium salts.  
     
     
         7 . The tissue product of  claim 1 , in which the tissue product is multi-layered.  
     
     
         8 . The tissue product of  claim 7 , in which the tissue product includes a middle layer positioned in between a first outer layer and a second outer layer of fibers, the first and second outer layers comprising hardwood fibers, the middle layer comprising softwood fibers.  
     
     
         9 . The tissue product of  claim 8 , in which the debonding additive is applied to the tissue product such that the additive is substantially only present in the first and second outer layers.  
     
     
         10 . The tissue product of  claim 1 , wherein the debonding additive has been applied to at least one surface of the tissue product.  
     
     
         11 . The tissue product of  claim 10 , in which the debonding additive has been applied to both sides of the tissue product.  
     
     
         12 . The tissue product of  claim 1 , wherein the first charge density is from about 1.22 meq/g to about 1.23 meq/g.  
     
     
         13 . The tissue product of  claim 1 , wherein the second charge density is from about 0.35 meq/g to about 0.42 meq/g.  
     
     
         14 . A method of making a tissue product, comprising: 
 (a) providing a fiber furnish of water and cellulosic fibers,    (b) forming the fiber furnish into a tissue layer, and    (c) applying to the surface of the tissue layer an adsorbable chemical additive, the chemical additive comprising a mixture of quaternary ammonium salts, the mixture comprising a first imidazoline quaternary ammonium salt, and a second imidazoline quaternary ammonium salt.    
     
     
         15 . The method of  claim 14  further comprising the step of: 
 (d) combining the tissue layer with additional tissue layers to form a layered tissue product.  
 
     
     
         16 . The method of  claim 14  further comprising the steps of: 
 (d) providing a second fiber furnish to form a second tissue layer,  
 (e) spraying upon the surface of the second tissue layer the adsorbable chemical additive, and  
 (f) forming the tissue product using the tissue layers as outer plies.  
 
     
     
         17 . The method of  claim 14 , wherein the first imidazoline quaternary ammonium salt has a first charge density and the second imidazoline quaternary ammonium salt has a second charge density, the first charge density being greater than about 0.9 meq/g, the second charge density being less than about 0.7 meq/g.  
     
     
         18 . The method of  claim 17 , wherein the first charge density is from about 1.22 meq/g to about 1.23 meq/g.  
     
     
         19 . The method of  claim 17 , wherein the second charge density is from about 0.35 meq/g to about 0.42 meq/g.  
     
     
         20 . The method of  claim 14 , wherein the additive is applied to the tissue layer when the tissue layer has a consistency of greater than about 20%.  
     
     
         21 . The method of  claim 14 , wherein the additive is applied to the tissue layer when the tissue layer has a consistency of greater than about 25% and less than about 80%.  
     
     
         22 . The method of  claim 14 , wherein the additive is applied to the tissue layer in between a rush transfer operation and a through-air drying operation.  
     
     
         23 . The method of  claim 14 , wherein the additive is applied to the tissue layer in between a first through-air drying operation and a second through-air drying operation.  
     
     
         24 . The method of  claim 14 , wherein the tissue layer comprises a stratified fiber furnish including a first layer and a second layer, the first layer comprising hardwood fibers, the second layer comprising softwood fibers.  
     
     
         25 . The method of  claim 24 , wherein the additive is applied to the first layer containing hardwood fibers, the additive being applied in a manner such that substantially all of the additive is contained within the first layer containing the hardwood fibers.  
     
     
         26 . The method of  claim 14 , wherein the tissue layer comprises a stratified fiber furnish including a middle layer positioned between a first outer layer and a second outer layer, the first and second outer layers comprising hardwood fibers, the middle layer comprising softwood fibers.  
     
     
         27 . The method of  claim 26 , wherein the additive is applied to the first outer layer and the second outer layer, the additive being applied in a manner such that the additive remains substantially within the first and second outer layers without migrating to the middle layer.  
     
     
         28 . The method of  claim 14 , wherein the additive further comprises a lubricant and a surfactant.  
     
     
         29 . The method of  claim 28 , wherein the lubricant comprises a lanolin derivative.  
     
     
         30 . The method of  claim 28 , wherein the surfactant comprises a polyethylene glycol ester, a polypropylene glycol ester, or mixtures thereof.  
     
     
         31 . A tissue product comprising: 
 a paper web comprising cellulosic fibers; and    an adsorbable chemical debonding additive topically applied to the paper web, the debonding additive being present in the web in an amount of from about 0.01% to about 10% by weight, the debonding additive comprising an aminofunctional siloxane or a nonionic siloxane, the debonding additive being applied to the paper web while the web has a consistency of less than about 80%.    
     
     
         32 . A tissue product as defined in  claim 31 , wherein the non-ionic silicone comprises polydimethylsiloxane.  
     
     
         33 . A tissue product as defined in  claim 31 , wherein the debonding additive is applied to the paper web when the paper web is at a consistency of less than about 60%.  
     
     
         34 . A tissue product as defined in  claim 31 , wherein the debonding additive is applied to the paper web when the paper web is at a consistency of less than about 40%.