Sealing member for a cap featuring excellent safety and environmental friendliness, and metal cap

Abstract

A sealing member for a cap featuring excellent cap performance as well as excellent safety and environmental friendliness, and a metallic cap. A foamed polyurethane elastomer having a JIS A hardness of from 15 to 65 and a foaming magnification of from 1.1 to 10 times is used as the sealing member so as to obtain excellent sealing performance, durability, safety and environmental friendliness. The sealing member is provided for a metallic cap shell that has a polyester film formed on the inner surface of the cap, thereby to obtain a cap featuring excellent sealing performance, durability, safety and environmental friendliness.

1 . A sealing member comprising a foamed polyurethane elastomer having a hardness (JIS A hardness) of from 15 to 65 and a foaming magnification of from 1.1 to 10 times.  
     
     
         2 . A sealing member according to  claim 1 , wherein said foamed polyurethane elastomer is the one that is formed by containing thermally expanding hollow particles in the polyurethane elastomer so as to be foamed.  
     
     
         3 . A sealing member according to  claim 1 , wherein said polyurethane elastomer is a two-part type polyurethane elastomer comprising a polyisocyanate and a polyol, and at least either the polyisocyanate or the polyol is blended with the thermally expanding hollow particles.  
     
     
         4 . A sealing member according to  claim 3 , wherein said two-part type polyurethane elastomer comprises: 
 (A) a polyisocyanate containing 5 to 38% by mass of isocyanate groups obtained by modifying an aliphatic isocyanate and/or an alicyclic isocyanate, and having functional groups in an average number of 2 to 3; and    (B) a polyol having a hydroxy value of from 20 to 350 (mgKOH/g) and functional groups in an average number of 2 to 3.