Granted Patent B2

US 12,240,956 · App. 17/591,725 · Granted Mar 4, 2025

Inventors: Takumi Sakamura (Tochigi, JP); Hajime Ohta (Tochigi, JP)

Assignee: JSP CORPORATION

C08J9/18B29C44/3461C08J9/0061C08J9/122B29K2023/12C08J2323/10C08J2423/12

Abstract

Claims (44)

1. An expanded bead having a tubular shape with a single through hole, comprising:

a foamed core layer comprising a polypropylene-based resin; and

a covering layer comprising a polyolefin-based resin, the covering layer covering the foamed core layer,

wherein the polyolefin-based resin of the covering layer has a melting point Tms that is lower than a melting point Tmc of the polypropylene-based resin of the foamed core layer,

wherein an average hole diameter d of the through hole of the expanded bead is less than 1 mm,

wherein a d/D ratio of the average hole diameter d to an average outer diameter D of the expanded bead is 0.3 or less,

wherein a t/D ratio of an average wall thickness t to the average outer diameter D is 0.35 or more and 0.5 or less,

wherein the polypropylene-based resin of the foamed core layer has a flexural modulus of 1,200 MPa or more, and

wherein the melting point Tmc of the polypropylene-based resin is 158° C. or lower.

2. The expanded bead of claim 1 , wherein the average outer diameter D of the expanded bead is 2 mm or more and 5 mm or less.

3. The expanded bead of claim 1 , having an average wall thickness t of 1.2 mm or more and 2 mm or less.

4. The expanded bead of claim 1 , wherein the d/D ratio is 0.25 or less.

5. The expanded bead of claim 1 , wherein the polypropylene-based resin of the foamed core layer is an ethylene-propylene random copolymer, and

wherein the ethylene-propylene random copolymer has 0.5 mass % or more and 2 mass % or less of ethylene component.

6. The expanded bead of claim 1 , wherein the melting point of the polypropylene-based resin of the foamed core layer is 145° C. or higher and 155° C. or lower.

7. The expanded bead of claim 1 , wherein a melt mass flow rate of the polypropylene-based resin of the foamed core layer is 6 g/10 min or more and 10 g/10 min or less.

8. The expanded bead of claim 1 , having an apparent density of 10 kg/m 3 or more and 100 kg/m 3 or less.

9. The expanded bead of claim 1 , wherein the foamed core layer comprises the polypropylene-based resin as a primary component by mass.

10. The expanded bead of claim 1 , wherein the foamed core layer further comprises a second polymer in an amount of 20 mass % or less.

11. The expanded bead of claim 1 , wherein the foamed core layer further comprises a second polymer in an amount of 10 mass % or less.

12. The expanded bead of claim 1 , wherein the foamed core layer further comprises a second polymer in an amount of 5 mass % or less.

13. The expanded bead of claim 1 , wherein a ratio of an apparent density of the expanded beads to a bulk density of the expanded beads is 1.7 or more and 2.3 or less.

14. The expanded bead of claim 1 , wherein the polypropylene-based resin comprises at least 98 mass % of propylene component.

15. The expanded bead of claim 1 , wherein the foamed core layer comprises the polypropylene-based resin as a first polypropylene-based resin, and further comprises a second polypropylene-based resin,

wherein the first and second polypropylene-based resins have different melting points,

wherein the first polypropylene-based resin has a flexural modulus of 1200 MPa or more, and

wherein the first polypropylene-based resin has a melting point of 158° C. or lower.

16. The expanded bead of claim 15 , wherein the first polypropylene-based resin is present in a range of from 70 to 97 wt. %, the first polypropylene-based resin having a melting point in a range of from more than 145 to 160° C., and

wherein the second polypropylene-based resin is present in a range of from 3 to 30 wt. %, the second polypropylene-based resin having a melting point in a range of more than 135 to 145° C.

17. The expanded bead of claim 15 , wherein the first and second polypropylene-based resins amount to 100 wt. % of the foamed core layer.

18. The expanded bead of claim 15 , wherein the first polypropylene-based resin is present in a range of from 75 to 95 wt. %, the first polypropylene-based resin having a melting point in a range of from more than 145 to 160° C., and

wherein the second polypropylene-based resin is present in a range of from 5 to 25 wt. %, the second polypropylene-based resin having a melting point in a range of more than 135 to 145° C.

19. The expanded bead of claim 15 , wherein the first polypropylene-based resin is present in a range of from 80 to 90 wt. %, the first polypropylene-based resin having a melting point in a range of from more than 150 to 155° C., and

wherein the second polypropylene-based resin is present in a range of from 10 to 20 wt. %, the second polypropylene-based resin having a melting point in a range of more than 140 to 145° C.

20. A method for producing the expanded bead of claim 1 , the method comprising:

expanding a multilayer resin particle having a tubular shape with a single through hole,

wherein the multilayer resin particle comprises a core layer comprising a polypropylene-based resin and a covering layer comprising a polyolefin-based resin,

wherein the covering layer covers the core layer,

wherein the polyolefin-based resin has a melting point Tmrs that is lower than a melting point Tmrc of the polypropylene-based resin of the core layer,

wherein an average hole diameter dr of the through hole of the multilayer resin particle is less than 0.25 mm,

wherein a dr/Dr ratio of the average hole diameter dr to an average outer diameter Dr of the multilayer resin particle is 0.4 or less,

wherein the polypropylene-based resin of the core layer has a flexural modulus of 1,200 MPa or more,

wherein the melting point Tmrc of the polypropylene-based resin is 158° C. or lower, and

wherein the expanded bead has an apparent density of 10 kg/m 3 or more and 100 kg/m 3 or less.

Assignments (1)

Priority Claims (1)

Continuity (1)

References Cited (26)