Patent Publication Number: US-2021170731-A1

Title: Laminate including sodium polyacrylate, and related systems and methods

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS AND INCORPORATION BY REFERENCE 
     This application claims priority from U.S. Provisional Patent Application 62/945,544 filed 9 Dec. 2019 and titled “PROCESS FOR MAKING SODIUM POLYACRYLATE INTO SHEET FORM, AND RELATED DEVICES AND SYSTEMS”. This application also incorporates by this reference the entirety of U.S. Provisional Patent Application 62/945,544. 
    
    
     BACKGROUND 
     Sodium Polyacrylate is a super absorbent polymer molecule. It is often used on movie and theater sets to create artificial snow by adding water to it. The conventional process for making Sodium Polyacrylate generates the molecule in powder form. In powder form, Sodium Polyacrylate is used to mimic snow falling on a set of a movie or theater, to absorb liquid in diapers, to absorb industrial spills, and to thicken hair gel and other products. 
     Unfortunately, because Sodium Polyacrylate typically exists in powder form and expands as much 40 times its original volume when exposed to water or other liquids, Sodium Polyacrylate is often used in situations where its expansion can occur uncontrolled. For example, the powder is often loosely contained in a pouch, such as a diaper, or not contained at all, such as when it is used to mimic snow falling on a movie set. When the Sodium Polyacrylate powder is held in a pouch, the powder inside the pouch may be moved around within the pouch, and when the powder is exposed to water or other liquid the powder expands uncontrollably within the pouch. When the Sodium Polyacrylate powder is used to mimic falling snow, the powder is loosely held in a bowl or trough, and when the powder is exposed to water the powder expands uncontrollably. Then, the water-expanded powder is poured over the movie set from a place high above the set. In these situations, the final form of the water-expanded Sodium Polyacrylate is simply an amorphous pile of highly expanded powder. 
     Thus, there is a need for a way to control the expansion Sodium Polyacrylate when it&#39;s exposed to water or other liquids, to allow one to control the final form of the expanded Sodium Polyacrylate. 
     SUMMARY 
     In one aspect of the invention, a laminate for forming objects that include Sodium Polyacrylate includes an adhesive substrate and a layer of Sodium Polyacrylate powder. The adhesive substrate includes a first surface facing a first direction away from the substrate, a second surface facing a second direction away from the substrate, and a thickness defined by the distance between the first surface and the second surface. The Sodium Polyacrylate is adhered to at least one of the first and second surfaces. 
     With Sodium Polyacrylate adhered to at least one of the substrate&#39;s surfaces, the expansion of the Sodium Polyacrylate powder is confined to the direction away from the surface; and, after expanding, the Sodium Polyacrylate remains attached to the substrate. This allows one to form an object from the laminate and then expand the Sodium Polyacrylate to give the appearance that the object is covered in snow. For example, one can form a two or three-dimensional snowflake out of the substrate, then adhere Sodium Polyacrylate to one or more of the substrate&#39;s surfaces. Then, when one adds water to the Sodium Polyacrylate, the Sodium Polyacrylate expands while remaining adhered to the substrate. In this manner, the snowflake may hang from a branch of a tree, such as a Christmas tree, without losing all of the expanded Sodium Polyacrylate, which makes the snowflake appear more real. 
     In another aspect of the invention, a method for forming objects that include Sodium Polyacrylate includes: a) forming a substrate by spreading an adhesive into a film, the substrate having a first surface facing a first direction away from the substrate, a second surface facing a second direction away from the substrate, and a thickness defined by the distance between the first surface and the second surface; b) placing Sodium Polyacrylate onto at least one of the first and second surfaces; and c) curing the adhesive to adhere the Sodium Polyacrylate to the at least one of the first and second surfaces. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a view of a laminate that includes a layer of Sodium Polyacrylate, according to an embodiment of the invention. 
         FIG. 2  shows a cross-sectional view of the laminate shown in  FIG. 1 , according to an embodiment of the invention. 
         FIG. 3  shows a view of another laminate that includes a layer of Sodium Polyacrylate, according to another embodiment of the invention. 
         FIG. 4  shows a cross-sectional view of the laminate shown in  FIG. 3 , according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a view of a laminate  10  that includes Sodium Polyacrylate and that one can use to form an object, according to an embodiment of the invention. The laminate  10  includes an adhesive substrate  12  and a layer  14  of Sodium Polyacrylate powder  16  (only four labeled for clarity) that is adhered to a surface of the substrate  12 . Once formed, the laminate  10  may be shaped into any desired object, such as a two or three-dimensional snowflake, and/or combined with any other object, such as a sheet of plywood, and will not lose the expanded Sodium Polyacrylate  16  when the Sodium Polyacrylate  16  is exposed to water or other liquids. 
     With Sodium Polyacrylate  16  adhered to the substrate  12 , the expansion of the Sodium Polyacrylate powder  16  is confined to the direction away from the substrate  12 ; and, after expanding, the Sodium Polyacrylate  16  remains attached to the substrate  12 . This allows one to form an object from the laminate  10  and then expand the Sodium Polyacrylate  16  to give the appearance that the object is covered in snow. For example, one can form a two or three-dimensional snowflake out of the substrate  12 , then adhere Sodium Polyacrylate  16  to one or more of the substrate&#39;s surfaces. Then, when one adds water to the Sodium Polyacrylate  16 , the Sodium Polyacrylate  16  expands while remaining adhered the substrate  12 . In this manner, the snowflake may hang from a branch of a tree, such as a Christmas tree, without losing all of the expanded Sodium Polyacrylate  16 , which makes the snowflake appear more real. For another example, one can form a sheet out of the substrate  12 , mount the substrate  12  to a sheet of plywood, then adhere Sodium Polyacrylate  16  to the exposed side of the substrate  12 . When one then adds water to the Sodium Polyacrylate  16 , the Sodium Polyacrylate  16  expands while remaining adhered the substrate  12 . In this manner, the laminate  10  and plywood can appear to be a patch or field of snow. 
     The laminate  10  is formed by first forming the adhesive substrate  12 . This is accomplished by spreading the adhesive into a film, or any other form such as a plate or curved object. Then, the adhesive substrate  12  may be partially cured before placing the Sodium Polyacrylate  16  onto the substrate  12 , or not (as discussed in greater detail in conjunction with  FIG. 2 ). After the Sodium Polyacrylate  16  is placed on the adhesive substrate  12 , the adhesive substrate  12  is cured some more to adhere the Sodium Polyacrylate  16  to the adhesive substrate  12 . 
     Other embodiments of the laminate  10  are possible. For example, the laminate  10  may include a third layer or carrier adhered to a portion of the adhesive substrate  12  that does have Sodium Polyacrylate adhered to it. 
       FIG. 2  shows a cross-sectional view of the laminate  10  shown in  FIG. 1 , according to an embodiment of the invention. The adhesive substrate  12  includes a first surface  18  facing a first direction  20  away from the substrate  12 , a second surface  22  facing a second direction  24  away from the substrate  12 , and a thickness  26  defined by the distance between the first surface  18  and the second surface  22 . The Sodium Polyacrylate  16  is then adhered to at least one of the first and second surfaces  18  and  22 . 
     The adhesive substrate  12  may be configured as desired. For example, in this and other embodiments the adhesive substrate  12  includes Polyvinyl Acetate and has a thickness  26  that is about 1.5 millimeters. More specifically, the film of Polyvinyl Acetate has a substantially uniform thickness, and the first and second surfaces  18  and  20  are substantially planar. In addition, the adhesive substrate  12  may be cured to any desired degree before, during, and/or after the application of the Sodium Polyacrylate powder  16  to provide the substrate  12  any desired degree of flexibility, and to provide any desired degree of constraint in the expansion of the Sodium Polyacrylate  16 . For Polyvinyl Acetate and other adhesives, the more complete the cure of the adhesive  12  is, the more rigid or stiff the film of the substrate  12  will be. During formation of the laminate  10 , a rigid or stiff adhesive  12  will prevent much of each of the individual kernels of Sodium Polyacrylate powder  16  from sinking into the adhesive substrate  12 . This can reduce the strength of the Sodium Polyacrylate&#39;s adherence to the substrate  12 . This can also reduce the ability of the adhesive substrate  12  to constrain the Sodium Polyacrylates expansion when it&#39;s exposed to water or other liquids. Whereas, a pliable or soft adhesive substrate  12  during the application of the Sodium Polyacrylate  16  will allow more of each of the individual kernels of Sodium Polyacrylate powder  16  to sink into or contact the adhesive substrate  12 . This can increase the strength of the Sodium Polyacrylate&#39;s adherence to the substrate  12 , and increase the ability of the adhesive substrate  12  to constrain the Sodium Polyacrylates expansion when it&#39;s exposed to water or other liquids. Likewise, after formation of the laminate  10 , a rigid or stiff adhesive  12  will confine the use of the laminate  10  to objects that will not experience much deformation. Whereas, a pliable or soft adhesive substrate  12  after formation of the laminate  10  will allow the use of the laminate  10  for objects that might experience much deformation. 
     In this and other embodiments, the adhesive substrate  12  is uncured when the Sodium Polyacrylate  16  is placed on the first surface  18  and then partially cured to form the laminate  10 . In other embodiments, the adhesive is fully cured to form the laminate  10 . And in still other embodiments the adhesive is partially cured when the Sodium Polyacrylate  16  is placed on the first surface  18 . 
     The Sodium Polyacrylate  16  may be distributed on the first and/or second surface  18  and/or  22  in any desired patter and concentration. For example, in this and other embodiments the Sodium Polyacrylate  16  is evenly distributed throughout the whole first surface  18 , and substantially covers all of the first surface  18 . In other embodiments, the Sodium Polyacrylate  16  may be distributed throughout the first surface  18  but may be distributed in a higher concentration in a region of the first surface  18 , and in a lower concentration in another region. In yet other embodiments, the Sodium Polyacrylate  16  may be distributed throughout a region of the first surface  18 , and absent in another region of the first surface  18 . 
     Each of  FIGS. 3 and 4  shows a view of another laminate  30  that includes a layer  32  of Sodium Polyacrylate  34 , according to another embodiment of the invention.  FIG. 3  shows a perspective view, and  FIG. 4  shows a cross-sectional view. The laminate  30  is similar to the laminate  10  shown in  FIGS. 1 and 2 , except that the adhesive substrate  32  does not have a uniform thickness throughout, but rather ridges  36  where the thickness of the adhesive substrate  32  is greater than the thickness of the substrate  32  elsewhere. Also, the distribution of the Sodium Polyacrylate  34  is more concentrated in the regions of the substrate&#39;s surface that includes the ridges  36 , than the regions of the substrate&#39;s surface that does not. When the Sodium Polyacrylate  34  is exposed to water and other liquid, the Sodium Polyacrylate  34  that is adhered to the ridges  36  expands and more fully covers the ridge  34  than the Sodium Polyacrylate  34  that is adhered to the other regions. This, in turn, provides the appears of a build of snow or a snow drift, or it may help give shape to the object that the laminate  30  is used to make. 
     The preceding discussion is presented to enable a person skilled in the art to make and use the invention. Various modifications to the embodiments will be readily apparent to those skilled in the art, and the generic principles herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.