Device and method for producing physically expanded structural foams during an injection molding process involving the use of dynamic mixing elements

• US 20060034958A1
• Filed: 10/09/2003
• Published: 02/16/2006
• Est. Priority Date: 10/22/2002
• Status: Active Grant

• Current Assignee: Peguform GmbH (Samvardhana Motherson International Ltd.)
• Original Assignee: Peguform GmbH (Samvardhana Motherson International Ltd.)
• Inventors: Schlummer, Christian
• Granted Patent: US 7,293,982 B2
• Time in Patent Office: Days
• US Class Current: 425/4.C
• CPC Class Codes: B29C 44/3449 through the screw
• CPC Class Codes: B29C 45/60 Screws
• CPC Class Codes: B29C 48/397 using a single screw
• CPC Class Codes: B29C 48/475 using pistons, accumulators or press rams
• CPC Class Codes: B29C 48/51 with internal flow passages, e.g. for molten material
• CPC Class Codes: B29C 48/53 having a varying channel depth, e.g. varying the diameter of the longitudinal screw trunk
• CPC Class Codes: B29C 48/56 having grooves or cavities other than the thread or the channel
• CPC Class Codes: B29C 48/67 having incorporated mixing devices not provided for in groups B29C48/52 - B29C48/66

Abstract

Foamed molded articles can be produced during an injection molding process, among other things, by utilizing physical blowing agents. Existing technologies differ to the greatest possible extent in the manner how the blowing agent is introduced into the melt. One possibility is to supply the blowing agent via mixing elements (9) from porous or permeable material that are provided across the screw piston (1) and which by means of a suitable blowing agent input unit load and homogeneously charge the melt with blowing agent during the metering phase of the polymeric material. The resulting single phase polymer/blowing agent mixture, when injected in to an injection mold tool, produces due to a reduction in pressure, a foam-textured part.

Claims

1. Device for the production of foamed plastic molded parts with an injection molding method, preferably utilizing a physical blowing agent, wherein the injection molding machine includes at least one injection cylinder (2), which includes at least one screw piston extending at least through a draw-in zone (4), a compression zone (5) and a metering zone (6), wherein the blowing agent is supplied preferably into an area following a metering zone (6), characterized in that the blowing agent is supplied only in some locally defined areas, wherein at an end (8) of the metering zone (6), the diameter of the screw piston is reduced and wherein porous or permeable mixing elements are provided.

2. Device according to claim 1, characterized in that by means of the mixing elements (9), a physical blowing agent is supplied to the polymer melt.

3. Device according to claim 1, characterized in that the blowing agent input unit is provided with a bore (11).

4. Device according to claim 1, characterized in that the mixing elements (9) are from sintered-metal or ceramic.

5. Device according to claim 1, characterized in that at least one mixing element (9) is configured as a rotation-symmetrical pin.

6. Device according to claim 1, characterized in that each mixing element (9) is provided with a device for connecting with the screw piston.

7. Device according to claim 6, characterized in that the device for connection with the screw piston includes a threaded bore.

8. Device according to claim 1, characterized in that the mixing element (9) is provided with at least one stepped area.

9. Device according to claim 8, characterized in that the stepped area is capable to receive a seal.

10. Device according to claim 9, characterized in that the seal is from copper or a high heat-proof O-ring.

11. Device according to claim 1, characterized in that a mixing element (9) includes cylinders of varying diameters.

12. Device according to claim 1, characterized in that the mixing element (9) is configured as a cone or a truncated cone.

13. Device according to claim 1, characterized in that a mixing element (9) is configured with a rhomb-shaped or rectangular cross section.

14. Device according to claim 1, characterized in that a mixing element (9) is configured as a straight prism or an angular prism.