Method for producing skin-covered polyolefin resin foamed molded article

Patent metadata

Field	Value
Publication number	US-10232534-B2
Application number	US-201414322257-A
Country	US
Kind code	B2
Filing date	Jul 2, 2014
Priority date	Jul 8, 2013
Publication date	Mar 19, 2019
Grant date	Mar 19, 2019

Abstract

A method for producing a skin-covered polyolefin-based resin foamed molded article, including blow-molding a polyolefin parison into a skin defining a hollow space; and placing multi-layered polyolefin expanded beads in the hollow space; and heating the expanded beads placed in the hollow space to fuse-bond the expanded beads together and to fuse-bond the expanded beads to the skin, wherein the expanded beads have specific apparent density, specific average diameter, specific endothermic peaks in their DSC curve and specific melting point characteristics.

First claim

What is claimed is:

1. A method for producing a skin-covered polyolefin-based resin foamed molded article, comprising the steps of:
extruding a melt comprising a polyolefin-based resin to form a parison in a softened state;
blow-molding the parison into a skin defining a hollow interior space;
filling multi-layered expanded beads comprising a polyolefin-based resin in the hollow interior space;
forming holes for introducing steam into the hollow interior space through steam pins by inserting steam pins through the skin; and
heating the multi-layered expanded beads filled in the hollow interior space to fuse-bond the multi-layered expanded beads to each other and to fuse-bond the multi-layered expanded beads to the skin by introducing steam into the hollow interior space through the steam pins inserted through the holes,
wherein the multi-layered expanded beads fulfill the following requirements (a) to (e):
(a) the multi-layered expanded beads have an apparent density of 0.03 to 0.2 g/cm 3 ;
(b) the multi-layered expanded beads have an average diameter of 1.5 to 3.0 mm and are formed by expanding multi-layer resin particles each having a weight of 0.2 to 0.7 mg;
(c) the multi-layered expanded beads, when measured by heat-flux differential scanning calorimetry in which a sample thereof is heated from 23° C. to 220° C. at a heating rate of 10° C/min, gives a DSC curve which has an endothermic peak A intrinsic to the polyolefin-based resin of the multi-layered expanded beads and at least one endothermic peak B on a high temperature side of the endothermic peak A, and in which a ratio of the heat of fusion of the endothermic peak B to the total heat of fusion of the endothermic peaks is 0.15:1 to 0.25:1 and the endothermic peak B of the multi-layered expanded beads has a heat of fusion of 15 to 24 J/g;
(d) the multi-layered expanded beads have a surface layer having a melting point lower than that of a region inside the surface layer; and
(e) the polyolefin-based resin of which the multi-layered expanded beads are comprised is a polypropylene-based resin.

2. The method for producing a skin-covered polyolefin-based resin foamed molded article according to claim 1 ,
wherein each of the multi-layered expanded beads has an expanded core layer that is covered with the surface layer,
wherein the expanded core layer comprises a first polyolefin-based resin having a melting point Tc and the surface layer comprises a second polyolefin-based resin having a melting point Ts, and
wherein the melting points Tc and Ts satisfy the following relationship (1):
Tc (° C.) > Ts (° C.)  (1).

3. The method for producing a skin-covered polyolefin-based resin foamed molded article according to claim 2 , wherein the melting points Tc and Ts satisfy the following relationship (2):
Tc (° C.) − Ts (° C.) >3 (° C.)  (2).

4. The method for producing a skin-covered polyolefin-based resin foamed molded article according to claim 2 , wherein the multi-layered expanded beads are obtained by expanding multi-layer resin particles each of which has a core layer comprising the first polyolefin-based resin and an outer layer comprising the second polyolefin-based resin and wherein a weight ratio of the first polyolefin-based resin to the second polyolefin-based resin is 99.5:0.5 to 80:20.

5. The method for producing a skin-covered polyolefin-based resin foamed molded article according to claim 2 , wherein the polyolefin-based resin of which the expanded core layer is constituted is a polypropylene-based resin having a bending elastic modulus of 700 MPa or higher.

6. The method for producing a skin-covered polyolefin-based resin foamed molded article according to claim 1 , wherein the polyolefin-based resin of which the skin is constituted is a polypropylene-based resin having a melt tension at 230° C. of 1 to 30 cN.

7. The method for producing a skin-covered polyolefin-based resin foamed molded article according to claim 1 , wherein the skin has a thickness of 1 to 5 mm.

Assignees

• Jsp Corp

Inventors

• Tokiwa Tomoo

Classifications

• B29C44/3461

  Making or treating expandable particles · CPC title

• B29K2105/048

  Expandable particles, beads or granules · CPC title

• B29C44/18

  Filling preformed cavities {(B29C44/1204 takes precedence)} · CPC title

• B29K2023/12

  PP, i.e. polypropylene · CPC title

• B29K2995/0063

  Density · CPC title