초록 ▼

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,

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 [g/m2/24 hr] as film and a melting point Tm[째 C.] shows specific relationship.

대표청구항 ▼

The invention claimed is: 1. A polypropylene resin expanded particle comprising as a base resin a polypropylene polymer comprising: a structural unit containing 100 to 85 mole % derived from propylene and 0 to 15 mole % derived from ethylene and/or alpha-olefin having 4 to 20 carbons; and as measur

The invention claimed is: 1. A polypropylene resin expanded particle comprising as a base resin a polypropylene polymer comprising: a structural unit containing 100 to 85 mole % derived from propylene and 0 to 15 mole % derived from ethylene and/or alpha-olefin having 4 to 20 carbons; and as measured by 13C-NMR, the content of position irregularity units formed by 2,1-insertions of propylene monomer units with respect to all propylene insertions is 0.5% to 2.0% and the content of the position irregularity units formed by 1,3-insertion of propylene monomer units with respect to all propylene insertions is 0.005% to 0.4%. 2. The polypropylene resin expanded particle according to claim 1, wherein the propylene polymer further comprises: an isotactic triad fraction of propylene unit chains, linked head-to-tail, of 97% or more as measured by 13C-NMR. 3. The polypropylene resin expanded particle as in claim 1, wherein the propylene polymer has a melt flow rate of 0.5 g/10 minutes to 100 g/10 minutes. 4. The polypropylene resin expanded particle according to claim 1, wherein the polypropylene resin expanded particle further comprises a blowing agent having a critical temperature represented by Formula (2): description="In-line Formulae" end="lead"-90≦Tc≦400 Formula (2)description="In-line Formulae" end="tail" wherein Tc is the critical temperature measured in 째 C. 5. A molded article produced by the process comprising molding the polypropylene resin expanded particles according to claim 1 in a mold, wherein the molded article has a density of 0.008 g/cm3 to 0.5 g/cm3. 6. The molded article according to claim 5, wherein the molded article is a shock absorber. 7. The shock absorber according to claim 6, wherein a density of the shock absorber is 0.02 to 0.45 g/cm3. 8. The shock absorber according to claim 7, 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. 9. The shock absorber according to claim 7, further comprising a skin material provided on a surface thereof, wherein the skin material is laminated on the surface thereof. 10. An automobile bumper comprising the shock absorber according to claim 7 as a core material. 11. An automobile bumper comprising the shock absorber according to claim 8 as a core material. 12. A molded article according to claim 5, 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 200째 C. at a rate of 10째 C./minute by means of a differential scanning calorimeter. 13. A polypropylene resin expanded particle comprising: a core layer in an expanded state comprising the polypropylene resin expanded particle of claim 1; and a coat layer comprising a thermoplastic resin wherein the coat layer covers the core layer. 14. A polypropylene resin expanded particle according to claim 13, wherein the coat layer comprises an olefin polymer having a melting point that is less than the melting point of the polypropylene resin of the core layer, or an olefin polymer that exhibits substantially no melting point. 15. The polypropylene resin expanded particle according to claim 13, wherein the coat layer comprises a polypropylene resin identical to the polypropylene resin of the core layer blended in an amount of 1 to 100 parts by weight per 100 parts by weight of the thermoplastic resin. 16. The polypropylene resin expanded particle according to claim 13, wherein the polypropylene resin expanded particle further comprises a blowing agent having a critical temperature represented by Formula (2): description="In-line Formulae" end="lead"-90≦Tc≦400 Formula (2)description="In-line Formulae" end="tail" wherein Tc is the critical temperature measured in 째 C. 17. A molded article produced by a process comprising molding the polypropylene resin expanded particles according to claim 13 in a mold, wherein the molded article has a density of 0.008 g/cm3 to 0.5 g/cm3. 18. The molded article according to claim 17, wherein the molded article is a shock absorber. 19. The shock absorber according to claim 18, wherein the density of the shock absorber is 0.02 to 0.45 g/cm3. 20. The shock absorber according to claim 19, further comprising a skin layer disposed on a surface thereof, wherein the skin layer has a density that is greater than the density of an inner portion of the shock absorber. 21. A shock absorber according to claim 20, wherein the skin material is laminated on the surface thereof. 22. An automobile bumper comprising the shock absorber according to claim 19 as a core material. 23. An automobile bumper comprising the shock absorber according to claim 20 as a core material. 24. A molded article according to claim 17, 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 200째 C. at a rate of 10째 C./minute by means of a differential scanning calorimeter.