Container and method of mitigating metal-contact contamination of polysilicon

Abstract

The present disclosure concerns reduction or mitigation of metal-contamination of polycrystalline silicon when held or stored in containers at least partially constructed of metal and/or having polysilicon contact surfaces at least partially of metal. In particular, the disclosure relates to a method of mitigating metal contamination of polycrystalline silicon from contact with a metal surface of a container by providing the surface with a protective layer comprising a microcellular elastomeric polyurethane.

We claim: 
     
         1 . A method of reducing or eliminating contamination of granular polysilicon, during storage or transportation, from contact with an inner metal surface of a container, the method comprising placing granular polysilicon in a container provided with a protective liner comprising microcellular elastomeric polyurethane on at least a portion of an inner metal surface of the container, the liner being located such that the granular polysilicon is shielded from contact with the inner metal surface. 
     
     
         2 . The method of  claim 1  wherein the polyurethane has a Shore Hardness of from 65A to 90A and a bulk density of from 800 to 1150 kg/m 3 . 
     
     
         3 . The method of  claim 1  wherein the protective liner has an overall thickness of from 0.1 to 10 millimeters. 
     
     
         4 . The method of  claim 1  wherein the granular polysilicon is essentially spheroid in form with an average size in its largest dimension of from 0.01 micron to 15 millimeters and is devoid of sharp or acute edge structure. 
     
     
         5 . A container suitable for holding granular polysilicon, the container comprising:
 a container comprising an inner metal surface that defines a region to contain granular polysilicon; and   a protective liner comprising microcellular elastomeric polyurethane on at least a portion of the inner metal surface facing the region, wherein the granular polysilicon is in contact with the protective liner when the granular polysilicon is present in the region, and wherein the polyurethane has a Shore Hardness of from 65A to 90A and a bulk density of from 800 to 1150 kg/m 3 .   
     
     
         6 . The container of  claim 5  wherein the protective liner has an overall thickness of from 0.1 to 10 millimeters. 
     
     
         7 . The container of  claim 5  wherein the granular polysilicon is essentially spheroid in form with an average size in its largest dimension of from 0.01 micron to as large as 15 millimeters and is essentially devoid of sharp or acute edge structure. 
     
     
         8 . A method of making the container of  claim 5 , the method comprising placing a protective liner comprising microcellular elastomeric polyurethane within a container comprising an inner metal surface, thereby covering at least a portion of the inner metal surface with the protective liner. 
     
     
         9 . The method of  claim 8 , wherein placing the protective liner within the container comprises (a) spray coating polyurethane onto the portion of the inner surface, or (b) forming the protective liner by in situ casting. 
     
     
         10 . The method of  claim 8 , wherein placing the protective liner within the container further comprises:
 obtaining a sheet of elastomeric microcellular polyurethane;   cutting the sheet to form one or more elastomeric microcellular polyurethane parts shaped to conform to the interior size and geometry of the region defined by the inner metal surface of the container;   coating the inner metal surface of the container with an adhesive; and   bringing the one or more elastomeric microcellular polyurethane parts into contact with the adhesive, thereby forming a laminate structure of metal/adhesive/polyurethane.   
     
     
         11 . The method of  claim 8 , wherein placing the protective liner within the container further comprises:
 obtaining a sheet of elastomeric microcellular polyurethane;   cutting the sheet to form one or more elastomeric microcellular polyurethane parts shaped to conform to the interior size and geometry of the region defined by the inner metal surface of the container;   coating an outer surface of the one or more polyurethane parts with an adhesive to form one or more adhesive-coated polyurethane parts; and   bringing the one or more adhesive-coated polyurethane parts into contact with the inner metal surface of the container, thereby forming a laminate structure of metal/adhesive/polyurethane.   
     
     
         12 . An article comprising:
 a) a container suitable for holding polysilicon, wherein the container has an inner metal surface that defines a region to contain polysilicon, and at least a portion of the inner surface is provided with a protective liner comprising microcellular elastomeric polyurethane; and   b) granular polysilicon located within the container, wherein the polysilicon is shielded from contact with the inner metal surface by the protective liner.   
     
     
         13 . The article of  claim 12  wherein the granular polysilicon is essentially spheroid in form with an average size in its largest dimension of from 0.01 micron to as large as 15 millimeters and is essentially devoid of sharp or acute edge structure.