Packaging material and method for making the same

Abstract

A packaging material and method for making the same are disclosed. The packaging material includes a strength layer and image layer. The strength layer has two opposed surfaces. The strength layer includes softwood fibers having an average length ranging from about 1.5 mm to about 3.0 mm. The softwood fibers present in an amount ranging from about 70 wt % to about 100 wt % of a total wt % of the strength layer. The image layer includes hardwood fibers having an average length ranging from about 0.5 mm to about 1.5 mm. The hardwood fibers present in an amount ranging from about 70 wt % to about 100 wt % of a total wt % of the image layer. The image layer includes a water soluble di-valent or multi-valent salt present in an amount ranging from about 5 lb per ton of total fibers in the image layer to about 50 lb per ton of the total fibers in the image layer.

What is claimed is: 
     
         1 . A packaging material, comprising:
 a strength layer having two opposed surfaces, the strength layer including:
 softwood fibers having an average length ranging from about 1.5 mm to about 3.0 mm, the softwood fibers present in an amount ranging from about 70 wt % to about 100 wt % of a total wt % of the strength layer; and 
   an image layer positioned on at least one of the two opposed surfaces, the image layer including:
 hardwood fibers having an average length ranging from about 0.5 mm to about 1.5 mm, the hardwood fibers present in an amount ranging from about 70 wt % to about 100 wt % of a total wt % of the image layer; and 
 a water soluble di-valent or multi-valent salt present in an amount ranging from about 5 lb per ton of total fibers in the image layer to about 50 lb per ton of the total fibers in the image layer. 
   
     
     
         2 . The packaging material as defined in  claim 1  wherein:
 at least some of the water soluble di-valent or multi-valent salt is present in the strength layer; and 
 the amount of the di-valent or multi-valent salt present in the image layer is at least five times an amount of the di-valent or multi-valent salt present in the strength layer. 
 
     
     
         3 . The packaging material as defined in  claim 1  wherein the image layer is positioned on one of the two opposed surfaces, and the packaging material further comprises a second strength layer positioned on an other of the two opposed surfaces, the second strength layer including second softwood fibers having an average length ranging from about 1.5 mm to about 3.0 mm, the second softwood fibers present in an amount ranging from about 50 wt % to about 100 wt % of a total wt % of the second strength layer. 
     
     
         4 . The packaging material as defined in  claim 3  wherein when the second strength layer includes less than 100 wt % of the second softwood fibers, the second strength layer further includes up to 50 wt % of recycled fibers other than the second softwood fibers. 
     
     
         5 . The packaging material as defined in  claim 1  wherein the image layer is positioned on one of the two opposed surfaces, and the packaging material further comprises a second image layer on an other of the two opposed surfaces, the second image layer including:
 second hardwood fibers having an average length ranging from about 0.5 mm to about 1.5 mm, the second hardwood fibers present in an amount ranging from about 70 wt % to about 100 wt % of a total wt % of the second image layer; and 
 a second water soluble di-valent or multi-valent salt present in an amount ranging from about 5 lb per ton of total fibers in the second image layer to about 50 lb per ton of the total fibers in the second image layer. 
 
     
     
         6 . The packaging material as defined in  claim 1  wherein when the image layer includes less than 100 wt % of the hardwood fibers, the image layer further includes one of:
 up to 20 wt % of other fibers other than the hardwood fibers; 
 up to 10 wt % of an additive selected from a group consisting of a dry strength additive, a wet strength additive, a filler, a retention aid, a dye, an optical brightening agent, a sizing agent, a biocide, a defoamer, a surfactant, or a combination thereof; or 
 up to 20 wt % of other fibers other than the hardwood fibers and up to 10 wt % of an additive selected from a group consisting of a dry strength additive, a wet strength additive, a filler, a retention aid, a dye, an optical brightening agent, a sizing agent, a biocide, a defoamer, a surfactant, or a combination thereof. 
 
     
     
         7 . The packaging material as defined in  claim 1  wherein when the strength layer includes less than 100 wt % of the softwood fibers, the strength layer further includes up to 30 wt % of other fibers other than the softwood fibers. 
     
     
         8 . A method for making a packaging material, the method comprising:
 jetting, from a first headbox, a first pulp stock onto a wire to form a strength layer precursor, the first pulp stock including:
 water; and 
 softwood fibers having an average length ranging from about 1.5 mm to about 3.0 mm, the softwood fibers present in the water in an amount ranging from about 70 wt % to about 100 wt % of a total solids wt % of the first pulp stock; 
 the first pulp stock excluding a water soluble di-valent or multi-valent salt; 
   jetting, from a second headbox, a second pulp stock onto a second wire to form an image layer precursor, the second pulp stock including:
 water; 
 hardwood fibers having an average length ranging from about 0.5 mm to about 1.5 mm, the hardwood fibers present in the water an amount ranging from about 70 wt % to about 100 wt % of a total solids wt % of the second pulp stock; and 
 a water soluble di-valent or multi-valent salt present in an amount ranging from about 5 lb per ton of total fibers in the second pulp stock to about 50 lb per ton of the total fibers in the second pulp stock; 
   placing the image layer precursor and the strength layer precursor in contact;   removing water from the image layer precursor and the strength layer precursor; and   drying the image layer precursor and the strength layer precursor to form the packaging material including an image layer and a strength layer.   
     
     
         9 . The method as defined in  claim 8  wherein the first headbox and the second headbox are part of a paperboard duo Fourdrinier machine. 
     
     
         10 . The method as defined in  claim 8  wherein the method further comprises jetting, from a third headbox, a third pulp stock onto a third wire to form a second strength layer precursor, the third pulp stock including:
 water; and 
 second softwood fibers having an average length ranging from about 1.5 mm to about 3.0 mm, the second softwood fibers present in the water in an amount ranging from about 50 wt % to about 100 wt % of a total solids wt % of the third pulp stock; 
 the third pulp stock excluding a water soluble di-valent or multi-valent salt; 
 and wherein the image layer precursor, the strength layer precursor, and the second strength layer precursor are placed in contact to form a stack with the image layer precursor forming an outer layer of the stack and wherein the drying step involves drying the stack. 
 
     
     
         11 . The method as defined in  claim 10  wherein prior to placing the image layer precursor, the strength layer precursor, and the second strength layer precursor in contact to form the stack, the method further comprises altering a consistency of any of the strength layer precursor or the second strength layer precursor to a consistency level ranging from about 5% to about 30%. 
     
     
         12 . The method as defined in  claim 8  wherein the image layer precursor and the strength layer precursor in contact form a bi-precursor structure, and wherein the method further comprises:
 jetting, from a third headbox, a third pulp stock onto a third wire to form a second strength layer precursor, the third pulp stock including:
 water; and 
 second softwood fibers having an average length ranging from about 1.5 mm to about 3.0 mm, the second softwood fibers present in the water in an amount ranging from about 50 wt % to about 100 wt % of a total solids wt % of the third pulp stock; 
 the third pulp stock excluding a water soluble di-valent or multi-valent salt; 
 
 jetting, from a fourth headbox, a fourth pulp stock onto a fourth wire, to form a second image layer precursor, the fourth pulp stock including:
 water; 
 second hardwood fibers having an average length ranging from about 0.5 mm to about 1.5 mm, the hardwood fibers present in the water an amount ranging from about 70 wt % to about 100 wt % of a total solids wt % of the third pulp stock; and 
 a second water soluble di-valent or multi-valent salt present in an amount ranging from about 5 lb per ton of total fibers in the fourth pulp stock to about 50 lb per ton of the total fiber in the fourth pulp stock; and 
 
 placing the second image layer precursor and the second strength layer precursor in contact to form a second bi-precursor structure; 
 removing water from the second bi-precursor structure; 
 prior to the drying of the image layer precursor and the strength layer precursor, placing the bi-precursor structure and the second bi-precursor structure into contact to form a stack having the strength layer precursor of the bi-precursor structure and the second strength layer precursor of the second bi-precursor structure in contact with one another; and 
 drying the stack, thereby performing the step of drying the image layer precursor and the strength layer precursor. 
 
     
     
         13 . The method as defined in  claim 12  wherein prior to placing the image layer precursor and the strength layer precursor in contact to form the bi-precursor structure, the method further comprises altering a consistency of the strength layer precursor to a consistency level ranging from about 5% to about 30%. 
     
     
         14 . The method as defined in  claim 12  wherein prior to placing the second image layer precursor and the second strength layer precursor in contact to form the second bi-precursor structure, the method further comprises altering a consistency of the second strength layer precursor to a consistency level ranging from about 5% to about 30%. 
     
     
         15 . The method as defined in  claim 8  wherein prior to placing the image layer precursor and the strength layer precursor in contact, the method further comprises altering a consistency of the strength layer precursor to a consistency level ranging from about 5% to about 30%.