Patent ID: 7402638

Claim:
A propylene random copolymer particle having a trilayer structure consisting of a first skin layer [L 1 ] that is present at the outermost crust, a second skin layer [L 2 ] that is internally contacting with the first skin layer, and a core [L 3 ] that is present inner to the second skin layer, wherein, in the transmission electron microscope (TEM) photograph (magnification×4000) of an ultrathin section of the core [L 3 ] after metal oxide staining, no stained component which has a particle diameter of 3 μm or greater is observed, and wherein the propylene random copolymer satisfies the following requirements [1] to [4]: [1] the concentration (Pa, % by mole) of a constituent of the copolymer derived from propylene (a), and the concentration (Px, % by mole) of a constituent of the copolymer derived from at least one olefin selected from ethylene (b) and α-olefins having 4 to 20 carbon atoms (c), each of which is contained in the propylene random copolymer, satisfy the following relational expressions (Eq-1) to (Eq-3): 85 ≦Pa <100 (Eq-1) 0 <Px ≦15 (Eq-2) Pa+Px =100 (Eq-3); [2] the concentration (Pa, % by mole) of the constituent of the copolymer derived from propylene (a) contained in the propylene random copolymer, and the melting point (Tm) measured with a differential scanning calorimeter satisfy the following relational expression (Eq-4): 135−4×(100 −Pa )< Tm <165−4×(100 −Pa ) (Eq-4); [3] the total amount of 2,1-bonded and 1,3-bonded non-stereoregular fractions is less than or equal to 0.2% by mole; and [4] the amount of the n-decane (nC 10 )-soluble fraction is less than or equal to 2.0% by weight.