Fire retarding polypropylene composition

Abstract

A fire retarding polypropylene composition comprising a copolymer of polypropylene in which ethylene/propylene rubber has been grafted onto the polypropylene chains, and at least about 50% by weight but not greater than 60% by weight of a magnesium hydroxide coated with an anionic surface active agent, the magnesium hydroxide having (i) a strain in the <101> direction of not more than 3.0×10 −3 , (ii) a crystallite size in the <101> direction of more than 800Å, and (iii) a specific surface area, determined by the BET method, of less than 20 mg 2 /g. The composition may be used in the formation of articles adapted to be used in a clean room, which pass the FMRC standards.

What is claimed is:  
     
         1 . A fire retarding polypropylene composition comprising: 
 (a) a copolymer of polypropylene resin in which ethylene/propylene rubber has been grafted onto the polypropylene chains; and    (b) at least about 50% but not greater than 60% by weight of a magnesium hydroxide coated with an anionic surface active agent, the magnesium hydroxide having: 
 (i) a strain in the <101> direction of not more than 3.0×10 −3 ,  
 (ii) a crystallite size in the <101> direction of more than 800Å, and  
 (iii) a specific surface area, determined by the BET method, of less than 20 mg 2 /g,  
   wherein the composition being adapted to meet FMRC standards for use in a clean room.    
     
     
         2 . The composition of  claim 1  wherein said copolymer contains between about 80% and about 85% polypropylene and between about 15% and about 20% ethylene/propylene rubber.  
     
     
         3 . The composition of  claim 1  wherein the melt flow index of said copolymer is less than about 1 gram per 10 minute interval.  
     
     
         4 . The composition of  claim 1  wherein said copolymer is halogen-free.