Polypropylene resin expanded particle and molded article using it

Abstract

A specific relationship must be met in case of: (a) a structural unit derived from propylene is present in 100 to 85 mole %, and a structural unit derived from ethylene and/or alpha-olefin with 4 to 20 carbons is present in 0 to 15 mole %; (b) a content of a position irregularity unit based on 2,1-insertion of a propylene monomer unit in all propylene insertions, which is measured by 13C-NMR, is 0.5% to 2.0% and a content of a position irregularity unit based on 1,3-insertion of propylene monomer unit in all propylene insertions, which is measured by 13C-NMR, is 0.005% to 0.4%; and (c) a water vapor transmission rate is Y [9/M 2 /24 hr] as film and a melting point Tm[° C.] shows specific relationship.

1 - 77 . (canceled)  
   
   
       78 . A polypropylene resin composition, comprising: 
 5% by weight to 95% by weight of a propylene polymer [A]; and    95% by weight to 5% by weight of a propylene polymer [B]   wherein the total amount of propylene polymers [A] and [B] is 100% by weight, the propylene polymer [A] has    (a) 100 to 85 mole % of a structural unit derived from propylene and 0 to 15 mole % of a structural unit derived from ethylene and/or alpha-olefin having 4 to 20 carbons wherein the total amount of the structural unit derived from propylene and the structural unit derived from ethylene and/or alpha-olefin having 4 to 20 carbons is 100 mole %;    (b) 0.5% to 2.0% of a position irregularity unit based on 2,1-insertion of a propylene monomer unit in all propylene insertions, and 0.005% to 0.4% of a position irregularity unit based on 1,3-insertion of propylene monomer unit in all propylene insertions, as measured by 13 C-NMR; and    the propylene polymer [B] has    100 to 85 mole % of a structural unit derived from propylene, and 0 to 15 mole % of a structural unit derived from ethylene and/or alpha-olefin having 4 to 20 carbons wherein the total amount of the structural unit derived from propylene and the structural unit derived from ethylene and/or alpha-olefin having 4 to 20 carbons is 100 mole %.    
   
   
       79 . The polypropylene resin composition as claimed in  claim 78 , wherein the polypropylene resin composition exhibits a substantially single melting peak as measured by a differential scanning calorimeter.  
   
   
       80 . The polypropylene resin composition as in  claim 78  wherein the polypropylene polymer [A] has an isotactic triad fraction of the propylene unit chains linked head to tail of 97% or more as measured by 13C-NMR.  
   
   
       81 . A polypropylene resin expanded particle comprising the polypropylene resin composition as claimed in  claim 78  as a base resin.  
   
   
       82 . A polypropylene resin expanded particle comprising: 
 a core layer in an expanded state comprising the polypropylene resin expanded particle of  claim 80;  and    a coat layer covering the core layer wherein the coat layer comprises a thermoplastic resin.    
   
   
       83 . The polypropylene resin expanded particle as in  claim 82 , wherein the coat layer comprises an olefin polymer having a melting point lower than either of the propylene polymers [A] and [B] forming the core layer or an olefin polymer that exhibits substantially no melting point.  
   
   
       84 . The polypropylene resin expanded particle as in  claim 82 , wherein the resin composition of the core layer exhibits a substantially single melting peak when measured using a differential scanning calorimeter.  
   
   
       85 . The polypropylene resin expanded particle as in  claim 82 , wherein the coat layer comprises the propylene polymer [A] and/or the propylene polymer [B] of the core layer blended with an olefin polymer in the amount of 1 to 100 parts by weight of the propylene polymer [A] and/or the propylene polymer [B] per 100 parts by weight of the olefin polymer.  
   
   
       86 . The polypropylene resin expanded particle as in  claim 81  wherein the polypropylene polymer [A] has an isotactic triad fraction of the propylene unit chains linked head to tail of 97% or more as measured by 13C-NMR.  
   
   
       87 . The polypropylene resin expanded particle as in  claim 81  wherein the propylene polymer [A] has a melt flow rate of 0.5 g/10 minutes to 100 g/10 minutes.  
   
   
       88 . The polypropylene resin expanded particle as in  claim 81 , wherein the polypropylene resin expanded particle further comprises a blowing agent having a critical temperature (Tc) represented by Formula (2):  
       −90° C.≦Tc≦400° C.   Formula (2).  
   
   
       89 . A molded article produced by the process comprising molding the polypropylene resin expanded particles according to  claim 81  in a mold, wherein the molded article has a density of 0.008 g/cm 3  to 0.5 g/cm 3 .  
   
   
       90 . The molded article according to  claim 89 , wherein the molded article is a shock absorber.  
   
   
       91 . The shock absorber according to  claim 90 , wherein a density of the shock absorber is 0.02 to 0.45 g/cm 3 .  
   
   
       92 . The shock absorber according to  claim 90 , further comprising 
 a skin layer disposed on a surface thereof, wherein the skin layer has a density greater than a density of an inner portion of the shock absorber.    
   
   
       93 . An automobile bumper comprising the shock absorber according to  claim 90  as a core material.  
   
   
       94 . An automobile bumper comprising the shock absorber according to  claim 91  as a core material.  
   
   
       95 . An automobile bumper comprising the shock absorber according to  claim 92  as a core material.  
   
   
       96 . A molded article according to  claim 89 , comprising a crystalline structure in which a peak inherent to the base resin and a peak at higher temperature than that of the inherent peak appear as endothermic peaks on a first DSC curve obtained when 2 mg to 4 mg of test specimens cut out from the molded article are heated up to 200° C. at a rate of 10° C./minute by means of a differential scanning calorimeter.