Plant comprising a twin-screw extruder for the continuous production of rolls of plastic stretch film

• US 20190329472A1
• Filed: 06/27/2016
• Published: 10/31/2019
• Est. Priority Date: 06/27/2016
• Status: Active Application

• Current Assignee: Colines Air Bubble S.R.L.
• Original Assignee: Colines Air Bubble S.R.L.
• Inventors: Mencarelli, Maurizio
• Application Number:
  US16/310,425
• Publication Number:
  US 20190329472A1
• Time in Patent Office: Days
• CPC Class Codes: B29C 2791/008 Using vibrations during moulding
• CPC Class Codes: B29C 2948/92152 Thickness
• CPC Class Codes: B29C 2948/92447 Moulded article
• CPC Class Codes: B29C 2948/92647 Thickness
• CPC Class Codes: B29C 48/0018 combined with shaping by orienting, stretching or shrinking, e.g. film blowing B29C48/0017 takes precedence
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29C 48/1476 at a conveyor
• CPC Class Codes: B29C 48/1478 at a storing zone
• CPC Class Codes: B29C 48/21 the layers being joined at their surfaces
• CPC Class Codes: B29C 48/265 Support structures or bases for apparatus, e.g. frames
• CPC Class Codes: B29C 48/28 Storing of extruded material, e.g. by winding up or stacking
• CPC Class Codes: B29C 48/355 Conveyors for extruded articles
• CPC Class Codes: B29C 48/387 using a screw extruder and a gear pump
• CPC Class Codes: B29C 48/40 using two or more parallel screws or at least two parallel non-intermeshing screws, e.g. twin screw extruders
• CPC Class Codes: B29C 48/402 the screws having intermeshing parts
• CPC Class Codes: B29C 48/495 Feed-blocks extrusion moulding of multi-component articles B29C48/16
• 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 48/535 with thread pitch varying along the longitudinal axis
• CPC Class Codes: B29C 48/57 provided with kneading disc-like elements, e.g. with oval-shaped elements
• CPC Class Codes: B29C 48/705 in the die zone, e.g. to create flow homogeneity
• CPC Class Codes: B29C 48/914 : cooling drums
• CPC Class Codes: B29C 48/92 : Measuring, controlling or regulating
• CPC Class Codes: B29C 55/06 : parallel with the direction of feed
• CPC Class Codes: B29C 55/18 : by squeezing between surfaces, e.g. rollers

Abstract

A twin-screw extruder is configured to produce rolls of plastic stretch film on a continuous basis, starting from the extrusion of granules of one or more polymers an using cast extrusion.

Claims

1. A plant (100) for continuous production of rolls of plastic stretch film (50) starting from granules of one or more polymeric plastic materials, said plant comprising:

an extrusion unit (80) that is a cast extrusion unit, in monoextrusion or in coextrusion, and that comprises a flat extrusion die (6) and one or more extruders (2,3) positioned upstream of said flat extrusion die (6), to form a melt of said one or more polymeric plastic materials;

a solidification unit of said melt comprising at least one chill-roll (7) with a continuous surface, positioned immediately downstream of said flat extrusion die (6) so as to solidify said melt, by cooling, to obtain said plastic stretch film (50); and

one or more winding units of the plastic stretch film into rolls, adapted to discharge said rolls after said rolls are produced,

wherein at least one of the extruders (2,3) of said one or more polymeric plastic materials is a twin-screw extruder (2), and

wherein said twin-screw extruder (2) supplies a respective amount of the melt of the one or more polymeric plastic materials with a pressure, at an outlet mouth, so as to fill parts of said plant positioned immediately downstream of said twin-screw extruder (2).

2. The plant according to claim 1, wherein said twin-screw extruder (2) is provided with a final metering section (L) of the respective amount of the melt, and wherein a free volume between a cylinder and a profile of screws of said twin-screw extruder (2) that occupy said section (L) decreases towards the outlet mouth of said twin-screw extruder (2) so as to generate the pressure at the outlet mouth of said twin-screw extruder (2) which is such as to fill said parts of the plant positioned immediately downstream of said twin-screw extruder (2).

3. The plant according to claim 1, wherein, when the plastic stretch film (50) is multilayer, a feed-block distributing device is provided upstream of said flat extrusion die (6), adapted to divide melts of said one or more polymeric plastic materials leaving said extruders (2,3) into a same number of streams as a layers forming the stretch film (50).

4. The plant according to claim 1, wherein the extrusion unit (80) comprises at least one gravimetric dosing system (1) configured to feed granules of the one or more polymeric plastic materials to the one or more extruders (2,3).

5. The plant according to claim 1, further comprising a measuring unit of a thickness of the plastic stretch film (50) after solidification, positioned downstream of a solidification station.

6. The plant according claim 1, further comprising an oscillation unit, positioned immediately upstream of said one or more winding units of the plastic stretch film (50) into rolls.

9. The plant according to claim 1, wherein the pressure is such to continuously feed one or both of said flat extrusion die (6) or a respective gear pump (5), if present, positioned downstream of said twin-screw extruder (2) and upstream of said extrusion die (6).

7. A process for continuous production of rolls of plastic stretch film (50) starting from extrusion of granules of one or more polymeric plastic materials, said process comprising:

extruding by cast extrusion said stretch film (50) through a flat extrusion die (6) fed by one or more extruders (2,3) of said granules, wherein at least one of the extruders (2,3) is a twin-screw extruder (2) which supplies the one or more polymeric plastic materials in molten state, with a pressure, at an outlet mouth, which is such as to fill parts of equipment positioned immediately downstream of said twin-screw extruder (2);

cooling and solidifying said molten plastic film with at least one chill-roll (7) so as to obtain a solidified plastic stretch film (50);

optionally, controlling a thickness of the solidified stretch film (50) to keep said thickness constant with respect to a width of the stretch film (50); and

optionally, treating the stretch film (50) by oscillation, in order to improve an aesthetical appearance of the rolls of the plastic stretch film (50).

8. (canceled)