Bulk Enhancement For Airlaid Material

Abstract

An airlaid substrate may have a positive increase in thickness through the addition of thermally expandable microspheres into the substrate. In one application, the substrate may be converted to sheets used as wet or dry wipes.

1 . A sheet comprising:
 an airlaid material having a thickness and comprising fibers;   a plurality of thermally expandable microspheres distributed at least partially through the material thickness; and a binder material applied to the sheet.   
     
     
         2 . The sheet of  claim 1  wherein the microspheres have an initial state and an expanded state, wherein the microspheres have an average diameter of about 80 micrometers when in the expanded state. 
     
     
         3 . The sheet of  claim 1  wherein the total adhesive binder material within the sheet is about 15 to 20 percent by weight. 
     
     
         4 . The sheet of  claim 3  wherein the thermally expandable microspheres content in the sheet is about 1 to about 10 percent by weight. 
     
     
         5 . The sheet of  claim 4  wherein the sheet is a thermally-bonded airlaid in the form of a wet wipe, the sheet having about a 46 to about 58 percent increase in sheet bulk as determined by the caliper measurement and bone-dry basis-weight test methods as described herein. 
     
     
         6 . The sheet of  claim 5  wherein the sheet is a multi-bonded airlaid material in the form of a wet wipe, wherein the wet wipe has about 80 to about 132 percent increase in sheet bulk as determined by the caliper measurement and bone-dry basis-weight test methods as described herein, and wherein the multi-bonded airlaid further comprises a thermal binder of about 16 percent by weight. 
     
     
         7 . The sheet of  claim 5  wherein the sheet is an adhesively-bonded airlaid in the form of a dispersible wet wipe, the sheet with 1 to 5% thermally expandable micropsheres by weight, and having about 10 to about 110 percent increase in sheet bulk as determined by the caliper measurement and bone-dry basis-weight test methods as described herein. 
     
     
         8 . The sheet of  claim 1  wherein the sheet is an adhesively-bonded airlaid in the form of a non-dispersible wet wipe, the sheet with 1 to 5% thermally expandable microspheres by weight and having about a 35 to about 120 percent increase in sheet bulk as determined by the caliper measurement and bone-dry basis-weight test methods as described herein. 
     
     
         9 . The sheet of  claim 1  wherein the binder is salt responsive. 
     
     
         10 . The sheet of  claim 1  wherein the binder is water dispersible. 
     
     
         11 . A method of making an airlaid sheet having a thickness, the method comprising the steps of:
 (a) spraying an airlaid sheet with a bonding material; and   (b) spraying the thermally expandable microspheres onto the airlaid sheet.   
     
     
         12 . The method of  claim 11  further comprising the step of applying a vacuum to the sheet so that the microspheres are distributed at least partially through the sheet thickness. 
     
     
         13 . The method of  claim 11  wherein step (b) is performed before step (a). 
     
     
         14 . The method of  claim 11  wherein steps (a) and (b) are accomplished simultaneously by mixing the bonding material with the thermally expandable microspheres prior to the spraying step. 
     
     
         15 . A method of making an airlaid sheet comprising the step of disposing the thermally expandable microspheres and fibers for airlaying into a forming station so that the airlaid sheet has thermally expandable microspheres distributed throughout the sheet thickness prior to spraying the sheet with a binder. 
     
     
         16 . The method of  claim 15  wherein the thermally expandable microspheres have an average diameter of about 80 micrometers when in an expanded state. 
     
     
         17 . The method of  claim 16  comprising the step of heating the sheet after distributing the thermally expandable microspheres into the sheet so that the microspheres expand to the average diameter.