Process for the processing of a thermoplastic polycondensation polymer

• US 5,102,594 A
• Filed: 01/10/1990
• Issued: 04/07/1992
• Est. Priority Date: 04/08/1988
• Status: Expired due to Fees

• Current Assignee: Dsm Nv
• Original Assignee: Stamicarbon B.V. (MAIRE)
• Inventors: Burlet, Rudolf J. H., Lemmens, Jozef M. H.
• Primary Examiner(s): Thurlow, Jeffrey
• Application Number:
  US07/637,258
• Time in Patent Office: 818 Days
• Field of Search: 264/102, 264/101, 264/37, 264/236, 264/347, 264/211.24, 264/DIG. 69, 425/203, 425/204, 425/205, 159/2.3
• US Class Current: 264/101
• CPC Class Codes: B29B 17/00 Recovery of plastics or other constituents of waste material containing plastics; volume reduction of waste plastics, e.g. by mechanical compacting or melting disposal of solid waste B09B; chemical recovery C08J11/00
• CPC Class Codes: B29B 7/38 rotary B29B7/52 takes precedence
• CPC Class Codes: B29B 7/426 with consecutive casings or screws, e.g. for charging, discharging, mixing
• CPC Class Codes: B29B 7/487 with consecutive casings or screws, e.g. for feeding, discharging, mixing
• CPC Class Codes: B29B 7/60 for feeding, e.g. end guides for the incoming material B29B7/7615 takes precedence; feeding predetermined amounts for mixing in general B01F35/714
• CPC Class Codes: B29B 7/726 Measuring properties of mixture, e.g. temperature or density B29B7/724 takes precedence
• CPC Class Codes: B29B 7/748 Plants B29B7/7433, B29B7/7485, B29B7/7495 take precedence
• CPC Class Codes: B29B 7/7485 with consecutive mixers, e.g. with premixing some of the components
• CPC Class Codes: B29B 7/84 Venting or degassing ; Removing liquids, e.g. by evaporating components
• CPC Class Codes: B29B 7/845 Venting, degassing or removing evaporated components in devices with rotary stirrers
• CPC Class Codes: B29B 7/86 for working at sub- or superatmospheric pressure B01F33/70 takes precedence
• CPC Class Codes: B29C 48/00 Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor extrusion blow-moulding B29C49/04
• CPC Class Codes: B29C 48/04 Particle-shaped making granules B29B9/00
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29C 48/285 Feeding the extrusion material to the extruder
• CPC Class Codes: B29C 48/2886 of fibrous, filamentary or filling materials, e.g. thin fibrous reinforcements or fillers
• CPC Class Codes: B29C 48/385 using two or more serially arranged screws in separate barrels
• CPC Class Codes: B29C 48/395 using screws surrounded by a cooperating barrel, e.g. single screw extruders
• 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 48/76 Venting , drying means; Degassing means
• CPC Class Codes: B29C 48/766 : in screw extruders
• CPC Class Codes: B29K 2067/003 : PET, i.e. poylethylene terephthalate
• CPC Class Codes: B29K 2105/12 : of short lengths, e.g. chopped filaments, staple fibres or bristles
• CPC Class Codes: Y02W 30/62 : Plastics recycling; Rubber recycling
• CPC Class Codes: Y10S 264/918 : From hollow- or container-type articles, e.g. tubes, bottles, cups

Abstract

The invention relates to a process for the processing of a thermoplastic polycondensation polymer by supplying the polymer in finely distributed form to a first vented extruder in which the polymer is devolatilized at a temperature below its melting temperature. The polymer is then placed in a second extruder where the polymer is transported below the melting temperature of the polymer over a first length of the screw from the inlet of the extruder, with constant evacuation of volatile components by means of a vacuum exhausting device at a vacuum of less than 10 mbar and the polymer is compressed and melted over a second length of the screw and then leaves the extruder as an end product of a semimanufacture.

Claims

1. A process for the processing of a thermoplastic polycondensation polymer, said process comprising:

(a) supplying polymer particles with a size of less than 2,000 μ

m to a first vented extruder in which said polymer is devolatilized and homogenized by means of transporting said polymer through said extruder at a temperature below the melting temperature of said polymer with constant evacuation of volatile components at a vacuum of less than 10 mbar;

(b) supplying said polymer to a second vented extruder in which said polymer is devolatilized by means of transporting said polymer over a first length of a screw at a temperature below the melting temperature of said polymer with constant evacuation of volatile components at a vacuum of less than 10 mbar; and

(c) compressing and melting said polymer over a second length of said screw of said second extruder, with said polymer exiting said second extruder as an end product or semi-manufacture,

wherein, said second screw length of said second extruder is equal to 1-10 times the diameter and wherein the total length of said first and second extruders screw path is equal to 20-45 times the diameter.

2. Process according to claim 1, characterized in that the total length of the screw path is larger than 25 times the diameter.

3. Process according to claim 1, characterized in that the remaining part of the screw length on which the polymer is compressed and melted is equal to 2 to 6 times the diameter of the screw.

4. Process according to claim 1, characterized in that the remaining part of the screw length on which the polymer is compressed and melted is equal to 3 to 4 times the diameter of the screw.

5. Process according to claim 1, characterized in that the constant evacuation of volatile components takes place at a vacuum of less than 5 mbar.

6. Process according to claim 1, characterized in that a twin-screw extruder is used as vented extruder.

7. Process according to claim 1, characterized in that the thermoplastic polycondensation polymer is polyethylene terephthalate.

8. Process according to claim 1, characterized in that the thermoplastic polycondensation polymer is obtained from waste polyethylene terphthalate bottles that have been comminuted.

9. Process according to claim 1, characterized in that the particle size is less than 1000 μ

m.

10. Process according to claim 1, characterized in that the particle size is less than 500 μ

m.