Process for producing polyvinyl alcohol articles

Abstract

The present invention provides a process for modifying the surface of a polyvinyl alcohol film or fabric by applying heat and pressure to the film or fabric to increase the moisture on the surface which is held by the fabric and to coalesce the surface fibers and reduce the porosity of the surface.

1 .- 13 . (canceled) 
     
     
         14 . A polyvinyl alcohol film or fabric comprising:
 a first outer surface; and   a second outer surface opposite the first outer surface, wherein the first outer surface and the second outer surface are an integral one-piece construction formed from a starting polyvinyl alcohol material;   wherein the first outer surface has been treated to have a reduced surface porosity relative to a surface porosity of the second outer surface.   
     
     
         15 . The polyvinyl alcohol film or fabric as recited in  claim 14 , wherein the reduced surface porosity is uniform and extends continuously along the first outer surface. 
     
     
         16 . The polyvinyl alcohol film or fabric as recited in  claim 14 , wherein the first outer surface has a reduced surface porosity relative to the starting polyvinyl alcohol material. 
     
     
         17 . The polyvinyl alcohol film or fabric as recited in  claim 16 , wherein the second outer surface has a surface porosity that is the same as the starting polyvinyl alcohol material. 
     
     
         18 . The polyvinyl alcohol film or fabric as recited in  claim 14  that is prepared by passing the starting polyvinyl alcohol material through a pair of opposed calendar rollers under conditions of heat and pressure. 
     
     
         19 . The polyvinyl alcohol film or fabric as recited in  claim 18 , wherein one of the pair of calendar rollers is heated and the other of the pair of calendar rollers is unheated. 
     
     
         20 . The polyvinyl alcohol film or fabric as recited in  claim 18 , wherein one of the pair of calendar rollers comprises surface coating of a high melting polymer film. 
     
     
         21 . The polyvinyl alcohol film or fabric as recited in  claim 18 , wherein after the step of passing, cooling by passing the polyvinyl alcohol material through a pair of opposed cooled calendar rollers. 
     
     
         22 . The polyvinyl alcohol film or fabric as recited in  claim 14 , wherein the first outer surface comprises an additive disposed thereon. 
     
     
         23 . The polyvinyl alcohol film or fabric as recited in  claim 22 , wherein the additive is selected from the group consisting of antimicrobial agents, anti-static agents, water repellants, dyes, and combinations thereof. 
     
     
         24 . The polyvinyl alcohol film or fabric as recited in  claim 14 , wherein the starting polyvinyl alcohol material has a water content of 5 to 15 percent by weight. 
     
     
         25 . A method of making a polyvinyl alcohol film or fabric comprising:
 subjecting a starting polyvinyl alcohol material to heat and pressure by passing the material through a pair of opposed calendar rollers to reduce a surface porosity of only one of two surfaces of the material; and   cooling the material after the step of subjecting, wherein the reduced surface porosity of the only one surface of the material is retained during the step of cooling.   
     
     
         26 . The method as recited in  claim 25 , wherein the surface of the material opposite the reduced surface porosity surface has a surface porosity that is similar to a surface porosity of the starting polyvinyl alcohol material before the step of subjecting. 
     
     
         27 . The method as recited in  claim 25 , wherein before the step of subjecting, the starting polyvinyl alcohol material has a water content of up to 15 percent by weight water. 
     
     
         28 . The method as recited in  claim 25 , wherein during the step of subjecting, one of the pair of calendar rollers is heated and the other of the pair of calendar rollers is unheated. 
     
     
         29 . The method as recited in  claim 25 , wherein during the step of subjecting, one of the pair of calendar rollers comprises a surface that is relatively softer than the other one of the pair of calendar rollers. 
     
     
         30 . The method as recited in  claim 29 , wherein the relatively softer calendar roller has a surface comprising a high melting polymer film. 
     
     
         31 . The method as recited in  claim 25 , wherein the polyvinyl alcohol film or fabric surfaces are an integral construction of the starting material and comprise an interface therebetween of the reduced surface porosity surface and the non-reduced surface porosity surface relative to the starting material. 
     
     
         32 . The method as recited in  claim 25 , wherein during the step of cooling, at least one of the opposed calendar rollers has a temperature below ambient temperature. 
     
     
         33 . The method as recited in  claim 25 , wherein the reduced surface porosity of the one polyvinyl alcohol film or fabric surface is uniform and extends continuously along the one surface.