Soft tissue products containing polysiloxane having a high z-directional gradient

Abstract

The present invention is a tissue product. The tissue product comprises at least one ply. Each ply comprises a first side and an opposing second side. At least one ply comprises a polysiloxane distributed non-uniformly in the z-direction within the ply such that the ply has a % z-directional polysiloxane gradient between the first side of the ply and the second side of the ply of about 20% or greater.

We claim:  
     
         1 . A tissue product comprising at least one ply, each ply comprises a first side and an opposing second side, wherein at least one ply comprises a polysiloxane distributed non-uniformly in the z-direction within the ply such that the ply has a % z-directional polysiloxane gradient between the first side of the ply and the second side of the ply of about 20% or greater.  
     
     
         2 . The tissue product of  claim 1 , wherein the polysiloxane in the ply or plies having the z-directional polysiloxane gradient is about 3 atomic % Si or greater on the side of the ply having the highest level of polysiloxane.  
     
     
         3 . The tissue product of  claim 1 , wherein the tissue product is a single ply tissue product.  
     
     
         4 . The tissue product of  claim 1 , wherein the tissue product is a multi-ply tissue product comprising at least two plies.  
     
     
         5 . The tissue product of  claim 1 , wherein the % z-directional gradient is about 30% or greater.  
     
     
         6 . The tissue product of  claim 1 , wherein the multi-ply tissue product comprises two plies, each ply comprising a z-directional gradient of polysiloxane wherein the sides of the plies having the higher level of polysiloxane are arranged so as to form the outer surfaces of the multi-ply tissue product.  
     
     
         7 . The tissue product of  claim 1 , wherein the multi-ply tissue product comprises at least three plies, each outer ply of the multi-ply tissue sheet comprises a % z-directional gradient of polysiloxane and wherein the sides of the two outer plies having the higher level of polysiloxane are arranged so as to form outer surfaces of the multi-ply tissue product.  
     
     
         8 . The tissue product of  claim 7 , wherein at least one of the inner plies does not contain a z-directional gradient of polysiloxane.  
     
     
         9 . The tissue product of  claim 1 , wherein the polysiloxane is delivered to the tissue product as a neat polysiloxane or as a mixture of neat polysiloxanes.  
     
     
         10 . The tissue product of  claim 1 , wherein the polysiloxane is topically applied to at least one ply of the tissue product thereby providing the z-directional polysiloxane gradient.  
     
     
         11 . The tissue product of  claim 1 , wherein the polysiloxane is delivered to the tissue product as polysiloxane pretreated pulp fibers.  
     
     
         12 . The tissue product of  claim 1 , wherein the polysiloxane is blended with a compatible binder and is topically applied to the tissue product.  
     
     
         13 . The tissue product of  claim 12 , wherein the compatible binder comprises a synthetic co-copolymer, the synthetic co-polymer having the general structure:  
       
         
           
           
               
               
           
         
       
       wherein: 
 each R 1 , R 2 , R 3  comprise independently a: H; C 1-4  alkyl radicals; or, mixtures thereof;  
 R 4  comprises a C 1 -C 8  alkyl radical or mixtures thereof;  
 Z 1  comprises a bridging radical attaching the R 4  functionality to the polymer backbone; and,  
 optionally Q 1  comprises a functional group comprising at least a cationic quaternary ammonium radical,  
 wherein w, x, y≧1, z≧0, and the mole ratio of z to x is from about 0:1 to about 4:1.  
 
     
     
         14 . The tissue product of  claim 13 , wherein Z 1  comprises a: —O—; —COO—; —OOC—; —CONH—; —NHCO—; or, mixtures thereof.  
     
     
         15 . The tissue product of  claim 13 , wherein Q 2  is derived from monomers selected from the group of: hydroxyalkyl acrylates; hydroxyalkyl methacrylates; hydroxyethyl acrylate; polyalkoxyl acrylates; polyalkoxyl methacrylates; diacetone acrylamide; N-vinylpyrrolidinone; N-vinylformamide; and, mixtures thereof.  
     
     
         16 . The tissue product of  claim 13 , wherein the mole ratio of (x+z):y is from about 0.98:0.02 to about 1:1.  
     
     
         17 . The tissue product of  claim 1 , wherein the polysiloxane has the general structure of:  
       
         
           
           
               
               
           
         
       
       wherein: 
 each R 1 -R 8  moiety comprises independently an organofunctional group or mixtures thereof; and,  
 y is an integer greater than 1.  
 
     
     
         18 . The tissue product of  claim 17 , wherein each R 1 -R 8  comprises independently a C 1  or higher of alkyl groups, aryl groups, ethers, polyethers, polyesters, amines, imines, amides, or mixtures thereof.  
     
     
         19 . The tissue product of  claim 1 , wherein the polysiloxane is an amino functional polysiloxane.  
     
     
         20 . The tissue product of  claim 19 , wherein the polysiloxane has the general structure:  
       
         
           
           
               
               
           
         
       
       wherein: 
 x and y are integers >0;  
 the mole ratio of x to (x+y) is from about 0.005 percent to about 25 percent;  
 each R 1 -R 9  moiety comprises independently an organofunctional group or mixtures thereof; and,  
 R 10  comprises an amino functional moiety or mixtures thereof.  
 
     
     
         21 . The tissue product of  claim 22 , wherein each R 1 -R 9  moiety comprises independently a C 1  or higher of alkyl groups, aryl groups, ethers, polyethers, polyesters, amides, or mixtures thereof.  
     
     
         22 . The tissue product of  claim 1 , wherein the polysiloxane has the general structure of:  
       
         
           
           
               
               
           
         
       
       wherein: 
 x and z are integers >0;  
 y is an integer ≧0;  
 the mole ratio of x to (x+y+z) is from about 0.05 percent to about 95 percent;  
 the mole ratio of y to (x+y+z) is from about 0 percent to about 25 percent;  
 each R 1 -R 9  comprises independently an organofunctional group or mixtures thereof;  
 R 10  comprises an amino functional moiety or mixtures thereof; and,  
 R 11  comprises a hydrophilic functionality or mixtures thereof.  
 
     
     
         23 . The tissue product of  claim 22 , wherein each R 0 -R 9  moiety comprises independently a C 1  or higher of alkyl groups, aryl groups, ethers, polyethers, polyesters, amines, imines, amides, substituted amides, or mixtures thereof.  
     
     
         24 . The tissue product of  claim 22 , wherein R 10  comprises an amino functional moiety selected from a primary amine, secondary amine, tertiary amine, quaternary amine, unsubstituted amide, and mixtures thereof.  
     
     
         25 . The tissue product of  claim 22 , wherein R 11  comprises a polyether functional group having the formula: —R 12 —(R 13 —O) a —(R 14 O) b —R 15  wherein: 
 each R 12 , R 13 , and R 14  comprises independently branched C 14 alkyl groups, linear C 14  alkyl groups, or mixtures thereof;  
 R 15  comprises H, C 1-30  alkyl group, or mixtures thereof; and,  
 a and b are integers of from about 1 to about 100.  
 
     
     
         26 . The tissue product of  claim 1 , wherein the tissue product comprises hardwood kraft pulp fibers, softwood kraft pulp fibers, mechanical pulp fibers, or mixtures thereof.  
     
     
         27 . The tissue product of  claim 1 , wherein at least one ply comprising the z-directional polysiloxane gradient is a blended tissue sheet having a homogeneous distribution of pulp fiber types within the z-direction of the ply.  
     
     
         28 . The tissue product of  claim 1 , wherein at least one ply comprising the z-directional polysiloxane gradient is a layered tissue sheet having a heterogeneous distribution of pulp fiber types within the z-direction of the ply.  
     
     
         29 . The tissue product of  claim 28 , wherein the side of at least one ply comprising the z-directional polysiloxane gradient having the higher polysiloxane content comprises hardwood kraft pulp fibers.  
     
     
         30 . The tissue product of  claim 29 , wherein the amount of the hardwood kraft pulp fibers in the ply is about 50 percent or greater.  
     
     
         31 . The tissue product of  claim 1 , wherein the polysiloxane content in at least one of the plies containing the z-directional polysiloxane gradient is from about 0.05% to about 5% by weight of pulp fibers within the ply.  
     
     
         32 . A method for making a tissue sheet comprising: 
 (a) forming at least one aqueous suspension of pulp fibers;    (b) depositing the aqueous suspension of pulp fibers onto a forming fabric to form a wet tissue sheet;    (c) dewatering the wet tissue sheet to form a dewatered tissue sheet;    (d) drying the dewatered tissue sheet to form a dried tissue sheet; and,    (e) optionally converting the tissue sheet to form a tissue product, wherein the tissue sheet comprises a first side and an opposing second side, the tissue sheet comprises a polysiloxane distributed non-uniformly in the z-direction within the tissue sheet such that the tissue sheet has a % z-directional polysiloxane gradient between the first side of the tissue sheet and the second side of the tissue sheet of about 20% or greater.    
     
     
         33 . The method of  claim 32 , wherein the tissue sheet is a blended tissue sheet having a homogeneous distribution of pulp fiber types in the z-direction of the tissue sheet.  
     
     
         34 . The method of  claim 32 , wherein the tissue sheet is a layered tissue sheet having a heterogeneous distribution of pulp fiber types in the z-direction of the tissue sheet.  
     
     
         35 . The method of  claim 32 , wherein the amount of polysiloxane on the side of the tissue sheet having the highest atomic % Si is about 3 atomic % Si or greater.  
     
     
         36 . The method of  claim 32 , wherein the tissue sheet is converted to form a single ply tissue product.  
     
     
         37 . The method of  claim 32 , wherein the tissue sheet is converted to form a multi-ply tissue product comprising at least two plies.  
     
     
         38 . The method of  claim 32 , wherein the % z-directional polysiloxane gradient within the tissue sheet is about 30% or greater.  
     
     
         39 . The method of  claim 37 , wherein the multi-ply tissue product comprises two plies, each ply comprising a z-directional gradient of polysiloxane wherein the sides of the plies having the higher level of polysiloxane are arranged so as to form outer surfaces of the multi-ply tissue product.  
     
     
         40 . The method of  claim 37 , wherein the multi-ply tissue product comprises at least three plies such that two plies form outer plies and at least one ply forms an inner ply, each outer ply of the multi-ply tissue sheet comprises a % z-directional gradient of polysiloxane and wherein the sides of the two outer plies having the higher level of polysiloxane are arranged so as to form outer surfaces of the multi-ply tissue product.  
     
     
         41 . The method of  claim 40 , wherein at least one inner ply of the multi-ply tissue product does not contain a z-directional polysiloxane gradient.  
     
     
         42 . The method of  claim 32 , wherein the polysiloxane is topically applied to the tissue sheet having a consistency of about 10% or greater as a neat polysiloxane or mixture of neat polysiloxanes.  
     
     
         43 . The method of  claim 42 , wherein the neat polysiloxane or mixture of neat polysiloxanes has a viscosity of about 25 centipoise or greater.  
     
     
         44 . The method of  claim 32 , wherein the polysiloxane is topically applied to the tissue sheet having a consistency of about 90% or greater as a neat polysiloxane or mixture of neat polysiloxanes.  
     
     
         45 . The method of  claim 32 , wherein the polysiloxane is topically applied to the tissue sheet during converting as a neat polysiloxane or mixture of neat polysiloxanes.  
     
     
         46 . The method of  claim 32 , wherein the polysiloxane is topically applied to the tissue sheet having a consistency of about 10% or greater as a blend of a polysiloxane and a compatible binder.  
     
     
         47 . The method of  claim 46 , wherein the polysiloxane is an emulsion and the compatible binder is delivered and blended with the polysiloxane emulsion as a solution or colloidal dispersion of the compatible binder in water.  
     
     
         48 . The method of  claim 46 , wherein the polysiloxane and compatible binder blend is topically applied to the tissue sheet having a consistency of about 90% or greater.  
     
     
         49 . The method of  claim 46 , wherein the polysiloxane and compatible binder blend is topically applied to the tissue product during converting.  
     
     
         50 . The method of  claim 46 , wherein the compatible binder comprises a synthetic co-copolymer, the synthetic co-polymer having the general structure:  
       
         
           
           
               
               
           
         
       
       wherein: 
 each R 1 , R 2 , R 3  comprise independently a: H; C 14  alkyl radicals; or, mixtures thereof;  
 R 4  comprises a C 1 -C 8  alkyl radical or mixtures thereof;  
 Z 1  comprises a bridging radical attaching the R 4  functionality to the polymer backbone; and,  
 optionally Q 1  comprises a functional group comprising at least a cationic quaternary ammonium radical,  
 wherein w, x, y>1, z>0, and the mole ratio of z to x is from about 0:1 to about 4:1.  
 
     
     
         51 . The method of  claim 50 , wherein Z 1  comprises a: —O—; —COO—; —OOC—; —CONH—; —NHCO—; or, mixtures thereof.  
     
     
         52 . The method of  claim 50 , wherein Q 2  is derived from monomers selected from the group of: hydroxyalkyl acrylates; hydroxyalkyl methacrylates; hydroxyethyl acrylate; 
 polyalkoxyl acrylates; polyalkoxyl methacrylates; diacetone acrylamide; N-vinylpyrrolidinone;    N-vinylformamide; and, mixtures thereof.    
     
     
         53 . The method of  claim 50 , wherein the mole ratio of (x+z):y is from about 0.98:0.02 to about 1:1.  
     
     
         54 . The method of  claim 32 , wherein the polysiloxane is delivered to the tissue sheet as polysiloxane pretreated pulp fibers.  
     
     
         55 . A method for making a tissue sheet, comprising: 
 a) forming at least a first aqueous suspension of pulp fibers comprising polysiloxane pretreated pulp fibers;    b) forming at least a second aqueous suspension of pulp fibers comprising non-treated pulp fibers;    c) depositing the first and the second aqueous suspensions of pulp fibers onto a forming fabric thereby forming a wet tissue sheet;    d) dewatering the wet tissue sheet thereby forming a dewatered tissue sheet;    e) drying the dewatered tissue sheet to form a dried layered tissue sheet; and,    f) optionally converting the tissue sheet to form a tissue product,    wherein the tissue sheet comprises a first side and an opposing second side, the tissue sheet comprises a polysiloxane distributed non-uniformly in the z-direction within the tissue sheet such that the tissue sheet has a % z-directional polysiloxane gradient between the first side of the tissue sheet and the second side of the tissue sheet of about 20% or greater.    
     
     
         56 . The method of  claim 55 , further comprising forwarding the first aqueous suspension of pulp fibers to a stratified headbox having at least two layers such that the first aqueous suspension of pulp fiber is directed to one of the outside layers of the stratified headbox.  
     
     
         57 . The method of  claim 56 , further comprising forwarding the second aqueous suspension of pulp fibers to the other outside layer of the stratified headbox thereby forming a layered wet tissue sheet comprising one outer layer comprising polysiloxane pretreated pulp fibers and the other outer layer comprising non-treated pulp fibers.  
     
     
         58 . The method of  claim 55 , wherein the amount of polysiloxane on the side of the tissue sheet having the highest atomic % Si is about 3 atomic % Si or greater.  
     
     
         59 . The method of  claim 55 , wherein the tissue sheet is converted to form a single ply tissue product.  
     
     
         60 . The method of  claim 55 , wherein the tissue sheet is converted to form a multi-ply tissue product comprising at least two plies.  
     
     
         61 . The method of  claim 55 , wherein the % z-directional polysiloxane gradient within the tissue sheet is about 30% or greater.  
     
     
         62 . The method of  claim 60 , wherein the multi-ply tissue product comprises two plies, each ply comprising a z-directional gradient of polysiloxane wherein the sides of the plies having the higher level of polysiloxane are arranged so as to form outer surfaces of the multi-ply tissue product.  
     
     
         63 . The method of  claim 60 , wherein the multi-ply tissue product comprises at least three plies such that two plies form outer plies and at least one ply forms an inner ply, each outer ply of the multi-ply tissue sheet comprises a % z-directional gradient of polysiloxane and wherein the sides of the two outer plies having the higher level of polysiloxane are arranged so as to form outer surfaces of the multi-ply tissue product.  
     
     
         64 . The method of  claim 63 , wherein at least one inner ply of the multi-ply tissue product does not contain a z-directional polysiloxane gradient.  
     
     
         65 . The method of  claim 55 , wherein the polysiloxane has the general structure of:  
       
         
           
           
               
               
           
         
       
       wherein: 
 each R 1 -R 8  moiety comprises independently an organofunctional group or mixtures thereof; and,  
 y is an integer greater than 1.  
 
     
     
         66 . The method of  claim 65 , wherein each R 1 -R 8  comprises independently a C, or higher of alkyl groups, aryl groups, ethers, polyethers, polyesters, amines, imines, amides, or mixtures thereof.  
     
     
         67 . The method of  claim 55 , wherein the polysiloxane is an amino functional polysiloxane.  
     
     
         68 . The method of  claim 55 , wherein the polysiloxane has the general structure:  
       
         
           
           
               
               
           
         
       
       wherein: 
 x and y are integers >0;  
 the mole ratio of x to (x+y) is from about 0.005 percent to about 25 percent;  
 each R 1 -R 9  moiety comprises independently an organofunctional group or mixtures thereof; and,  
 R 10  comprises an amino functional moiety or mixtures thereof.  
 
     
     
         69 . The method of  claim 68 , wherein each R 1 -R 9  moiety comprises independently a C 1  or higher of alkyl groups, aryl groups, ethers, polyethers, polyesters, amides, or mixtures thereof.  
     
     
         70 . The method of  claim 55 , wherein the polysiloxane has the general structure of:  
       
         
           
           
               
               
           
         
       
       wherein: 
 x and z are integers >0;  
 y is an integer ≧0;  
 the mole ratio of x to (x+y+z) is from about 0.05 percent to about 95 percent;  
 the mole ratio of y to (x+y+z) is from about 0 percent to about 25 percent;  
 each R 0 -R 9  comprises independently an organofunctional group or mixtures thereof;  
 R 10  comprises an amino functional moiety or mixtures thereof; and,  
 R″ comprises a hydrophilic functionality or mixtures thereof.  
 
     
     
         71 . The method of  claim 70 , wherein each R 0 -R 9  moiety comprises independently a C 1  or higher of alkyl groups, aryl groups, ethers, polyethers, polyesters, amines, imines, amides, substituted amides, or mixtures thereof.  
     
     
         72 . The method of  claim 70 , wherein R 10  comprises an amino functional moiety selected from a primary amine, secondary amine, tertiary amine, quaternary amine, unsubstituted amide, and mixtures thereof.  
     
     
         73 . The method of  claim 70 , wherein R″ comprises a polyether functional group having the formula: —R 12 —(R 13 —O) a —(R 14 O) b —R 15    
       wherein: 
 each R 12 , R 13 , and R 14  comprises independently branched C 1-4 alkyl groups, linear C 1-4  alkyl groups, or mixtures thereof;  
 R 15  comprises H, C 1-30  alkyl group, or mixtures thereof; and,  
 a and b are integers of from about 1 to about 100.