Polypropylene resin pre-expanded particles and in-mold foamed articles prepared therefrom

• US 8,569,390 B2
• Filed: 12/21/2005
• Issued: 10/29/2013
• Est. Priority Date: 01/12/2005
• Status: Active Grant

• Current Assignee: Kaneka Corporation
• Original Assignee: Kaneka Corporation
• Inventors: Kiguchi, Taro, Iwamoto, Tomonori
• Primary Examiner(s): Buttner, David
• Assistant Examiner(s): BOYLE, KARA BRADY
• Application Number:
  US11/795,067
• Publication Number:
  US 20080153933A1
• Time in Patent Office: 2,869 Days
• Field of Search: 521/56, 521/59, 521/80, 525/240
• US Class Current: 521/59
• CPC Class Codes: B29C 44/3426 Heating by introducing steam in the mould
• CPC Class Codes: B29C 44/445 in the form of expandable granules, particles or beads
• CPC Class Codes: C08J 2323/10 Homopolymers or copolymers of propene
• CPC Class Codes: C08J 9/232 by sintering expandable particles

Abstract

An object of the present invention is to provide an in-mold foamed article having good surface appearances and high rigidity produced by using a common molding machine that withstands a pressure of up to 0.4 MPa. The present invention provides polypropylene resin pre-expanded particles containing a base resin which is a resin having a melt flow rate of 5 g/10 min or more and 20 g/10 min or less and a melting point of 140° C. or higher and 155° C. or lower and satisfying the conditional formula below, and an in-mold foamed article produced from molding the pre-expanded particles:
[Heat of crystal fusion (J/g)]≧1.2×[Melting point (° C.)]−96.

Claims

1. A polypropylene resin pre-expanded particle comprising a base resin that has a MFR of 5 g/10 min or more and 20 g/10 min or less and a melting point of 140°

C. or higher and 155°

C. or lower,

wherein the base resin is a mixture containing;

70 percent or more and 95 percent or less by weight of a polypropylene resin (A) having a MFR of 10 g/10 min or more and 30 g/10 min or less and a molecular weight distribution Mw/Mn of 6 or less, and containing 1-butene as a comonomer; and

5 percent or more and 30 percent or less by weight of a polypropylene resin (B) having a MFR of 0.1 g/10 min or more and 3 g/10 min or less, and

the base resin exhibits a relationship between a heat of crystal fusion and the resin melting point determined with a differential scanning calorimeter satisfying conditional formula (1);

[Heat of crystal fusion (J/g)]≧

1.2×

[Melting point (°

C.)]−

96 

 

(1).

2. The polypropylene resin pre-expanded particle according to claim 1, wherein a ratio {Qh/(Ql+Qh)}×

100 of the heat at the high-temperature-side fusion peak calculated from heat of a low-temperature-side fusion peak Ql and heat of a high-temperature-side fusion peak Qh is 15% or more and 50% or less, the two fusion peaks being observed by differential scanning calorimetry.

3. An in-mold foamed article produced from the polypropylene resin pre-expanded particle according to claim 1, wherein the article has a density of 10 kg/m³ or more and 300 kg/m³ or less.

4. The polypropylene resin pre-expanded particle according to claim 1, wherein the MFR of the polypropylene resin, the polypropylene resin (A) and polypropylene resin (B) are measured with a MFR meter described in JIS-K7210, with an orifice diameter of 2.0959±

0.005 mm, an orifice length of 8.000±

0.025 mm, a load of 2,160 g, and a temperature of 230°

C.±

0.2°

C.

5. The polypropylene resin pre-expanded particle according to claim 1, wherein the polypropylene resin (B) has a MFR of 0.2 g/10 min or more and 2 g/10 min or less.