Extruder for producing molten plastic materials

• US 20050047267A1
• Filed: 10/11/2002
• Published: 03/03/2005
• Est. Priority Date: 10/12/2001
• Status: Active Grant

• Current Assignee: SMS Siemag AG (Bernhard-Weiss-Stiftung), Gneuss Kunststofftechnik Gmbh
• Original Assignee: SMS Siemag AG (Bernhard-Weiss-Stiftung)
• Inventors: Gneuss, Detlef, Walach, Wieslaw
• Granted Patent: US 7,513,677 B2
• Time in Patent Office: Days
• US Class Current: 366/83
• CPC Class Codes: B29B 7/485 with three or more shafts provided with screws
• CPC Class Codes: B29B 7/86 for working at sub- or superatmospheric pressure B01F33/70 takes precedence
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29C 48/43 Ring extruders
• CPC Class Codes: B29C 48/435 Sub-screws
• CPC Class Codes: B29C 48/767 through a degassing opening of a barrel
• CPC Class Codes: B29C 67/246 Moulding high reactive monomers or prepolymers, e.g. by reaction injection moulding [RIM], liquid injection moulding [LIM] casting monomers B29C39/006, mixing construction B29B7/74

Abstract

The invention concerns an extruder for producing molted plastic materials from plastic granules available on the market, by heating and mixing granules, with heated single- or double-screw extruders, and for carrying out polycondensation or polymerization using part of a multiple-screw extruder and by means of vacuum chambers for removing the constituents of low molecular weight and/or foaming agents or the like, for obtaining larger molecules and hence a higher viscosity, and for increasing the mechanical strength of plastic materials produced from said molten material. The invention aims at designing said extruder such that the molten material can be processed in thin layers enabling exposure of large surfaces in contact with the vacuum, and hence a molten plastic material ensuring desired levels of degassing and polymerization using simple means. Therefor, the envelopes of the stems of the screws (7) are mutually spaced apart at least in the polycondensation zone of said extruder part with multiple screws (6), relative to the extruder screw (4) or its shaft section (10) and relative to cylindrical zones enclosing them, by a distance not less than zero (>0).

Claims

1. Extruder for producing melts from commercially available granulated plastics by heating and milling the granules by means of heated single-screw or twin-screw extruders, for carrying out condensation polymerization or polymerization by using a section (6) of the extruder that is designed as a multi-screw extruder, with the use of evacuated chambers for removing low-molecular-weight constituents and/or blowing agents or the like, for obtaining larger molecules and thus higher viscosities, and for increasing the mechanical strength of the plastic produced from the melt, wherein, at least in the polycondensation zone of the multi-screw extruder section (6), the envelopes of the screw shafts (7) are spaced apart from each other, from the extruder screw (4) and its shaft section (10), and from the cylindrical zones surrounding them by a distance that is greater than or equal to zero (³ 0).

2. Extruder in accordance with claim 1, wherein at least two screw shafts (7), which form the multi-screw extruder section (6) and are arranged parallel to the axis, move with rolling contact on the shaft section (10), such that each screw shaft (7) has at least one journal (8) designed as a gear wheel, which engages at least one ring gear (11), which is rigidly connected with the shaft section (10) of the central extruder screw (4) to prevent it from rotating.

3. Extruder in accordance with claim 2, wherein the screw shafts (7) are held in the clearances (14) of at least one guide (15), which is mounted on or supported in the casing (5) of the multi-screw extruder section (6).

4. Extruder in accordance with claim 1, wherein a guide (15′

) is rigidly mounted on the shaft section (10′

) to prevent it from rotating, and that the screw shafts (7′

) are supported in the clearances (14′

) of the guide (15′

) and have journals (8′

), which are designed as gear wheels and engage at least one gear rim (9′

), which is connected to the casing (5).

5. Extruder in accordance with claim 3, wherein the clearances (14, 14′

) are designed in such a way that the guide(s) (15, 15′

) surround the envelope of the screw shafts (7, 7′

) at a small distance.

6. Extruder in accordance with claim 2, wherein the screw shafts (7) are designed at both ends as toothed journals (8), and that each side of the toothed journals (8), together with the corresponding additional toothed journals (8), are surrounded by a gear rim (9) or similar support part, which provides the support.

7. Extruder in accordance with claim 4, wherein the gear rims (9, 9′

) are connected to the casing (5) of the multi-screw extruder section (6), or their teeth are incorporated in the casing (5).

8. Extruder in accordance with claim 2, wherein the journals (8, 8′

), which are designed as gear wheels, of different screw shafts (7, 7′

) engage different ring gears (11) and/or gear rims (9, 9′

).

9. Extruder in accordance with claim 8, wherein the different ring gears (11) and/or gear rims (9, 9′

) have different gear ratios with the journals (8, 8′

) designed as gear wheels.

10. Extruder in accordance with claim 8, wherein a different ring gear (11) and/or gear rim (9, 9′

) is provided for each screw shaft (7, 7′

).

11. Extruder in accordance with claim 8, wherein the different gear rims (9, 9′

) are rotatably supported in the casing (5) and can be driven by motors.

12. Extruder in accordance with claim 1, wherein the casing (5) of the multi-screw extruder section (6) is provided with a vacuum channel (12) for connection to a vacuum pump.

13. Extruder in accordance with claim 1, wherein the shaft section (10) is cylindrical in shape.

14. Extruder in accordance with claim 1, wherein the shaft section (10) has at least one helix, by which the melt can be axially conveyed in or against the direction of advance of the extruder screw (4).

15. Extruder in accordance with claim 14, wherein the ring gears (11) are formed by the helix.

16. Extruder in accordance with claim 2, wherein the teeth between the toothed journals (8) and the gear rims (9, 9′

) or the ring gears (11) are designed as straight and/or as oblique teeth.

17. Extruder in accordance with claim 2, wherein the screws of the screw shafts (7, 7′

) have different leads.