Process for de-polymerization of styrenic monomer-containing polymers and for retrieval of styrenic monomers

Patent metadata

Field	Value
Publication number	US-11999686-B2
Application number	US-202017419063-A
Country	US
Kind code	B2
Filing date	Jan 7, 2020
Priority date	Jan 7, 2019
Publication date	Jun 4, 2024
Grant date	Jun 4, 2024

Abstract

The invention relates to an improved process for providing purified styrenic monomers, such as styrene, from styrene-containing polymer waste. Styrene-containing waste is depolymerized in a suitable reactor, and the depolymerization products are condensed and separated in a three-step distillation process.

First claim

The invention claimed is:

1. A process for retrieving styrenic monomer from a polymer mixture (P),
the polymer mixture (P) comprising:
(A) 1 wt-% to 99.8 wt-%, related to the total weight of polymer mixture (P),
of a styrenic polymer comprising:
i. 70 wt-% to 100 wt-%, related to the total weight of (A), of repeating units derived from a styrenic monomer selected from styrene and alpha-methylstyrene;
ii. 0 wt-% to 30 wt-%, related to the total weight of (A), of repeating units derived from dienes;
iii. 0 wt-% to 2 wt-%, related to the total weight of (A), of repeating units derived from other radically co-polymerizable monomers;

(B) 0.1 wt-% to 98.9 wt-%, related to the total weight of polymer mixture (P), of a mixture of polymers other than polymer (A);
(C) 0.1 wt-% to 30 wt-%, related to the total weight of polymer mixture (P), of organic or inorganic polymer additives and auxiliaries; and optionally
(D) 0 wt-% to 50 wt-%, related to the total weight of polymer mixture (P), of impurities such as, but not limited to, food waste, dirt, packaging residues or moisture,
the process comprising the steps of:
I) feeding the polymer mixture (P) into a pyrolysis zone of a pyrolysis reactor and subjecting it to a temperature of 300° C. to 650° C., measured as the average temperature of the polymer mixture (P) at the inner surface of the reactor wall during the reaction runtime, during which at least partial decomposition of the component (A) to styrenic monomers takes place, and a gas containing said styrenic monomers is formed;
II) condensing the condensable substances including styrenic monomers from the gas formed in step I) at a cooling rate of more than 500° C./min (500 K/min);
III) fractionating the condensed substances from step II) in a distillation column (X),
wherein in step III),
a fraction (a1) comprising styrenic monomers is withdrawn through a side outlet from the distillation column (X), at a position above 65% to 95% and below 35% to 5% of the total number of theoretical stages;
a fraction (a2) comprising heavy boilers is collected at the bottom of the distillation column (X);
a fraction (a3) comprising light boilers is collected at the head of the distillation column (X); and
the distillation column (X) is operated at a bottom pressure of 200 hPa (150 mmHg) to 533 hPa (400 mmHg), a head pressure of 133 hPa (100 mmHg) to 400 hPa (300 mmHg), a bottom temperature of 200° C. to 300° C., and a head temperature of 40° C. to 80° C.

2. The process according to claim 1 , wherein the polymer mixture (P) comprises 80 wt-% to 99.8 wt-%, related to the total weight of polymer mixture (P), of the styrenic polymer (A) and 0.1 wt-% to 19.9 wt-%, related to the total weight of polymer mixture (P) of the mixture of polymers (B).

3. The process according to claim 1 , wherein a stabilizer or radical scavenger is added to the condensable substances in step II).

4. The process according to claim 1 , further comprising the step
IV) fractionating fraction (a1) obtained in step III) in a distillation column (Y).

5. The process according to claim 4 , wherein in step IV) a fraction (b1) comprising styrenic monomers and components with a higher boiling point than the styrenic monomers is withdrawn from the bottom of the distillation column (Y) and a fraction (b2), comprising components with a lower boiling point than the styrenic monomers is withdrawn from the head of the distillation column (Y).

6. The process according to claim 4 , wherein the distillation column (Y) is operated at a bottom pressure of 160 hPa (120 mmHg) to 347 hPa (260 mmHg), a head pressure of 40 hPa (30 mmHg) to 147 hPa (110 mmHg), a bottom temperature of 80° C. to 120° C., and a head temperature of 50° C. to 80° C.

7. The process according to claim 4 , further comprising the step of:
V) separating the fraction comprising styrenic monomers obtained in step IV) in a distillation column (Z), wherein
a fraction (c1) comprising styrenic monomers is withdrawn from the head of the distillation column (Z); and
a fraction (c2), comprising components with a higher boiling point than the styrenic monomers, is collected at the bottom of the distillation column (Z); wherein
the distillation column (Z) is operated at a bottom pressure of 133 hPa (100 mmHg) to 467 hPa (350 mmHg), a head pressure of 13 hPa (10 mmHg) to 133 hPa (100 mmHg), a bottom temperature of 80° C. to 150° C., and a head temperature of 45° C. to 100° C.

8. The process according to claim 4 , wherein the distillation column (Y) in step IV) comprises at least 50 theoretical stages.

9. The process according to claim 1 , wherein the component (B) is a mixture of polymers selected from the group consisting of polyolefins; hydrogenated or non-hydrogenated ethylene-propylene-diene-rubber (EPDM); polyvinyl chloride (PVC); chlorinated polyvinyl chloride (c-PVC); polycarbonates; polyamides; and polyesters.

10. The process according to claim 1 , wherein the component (B) contains
iv. 0 wt-% to 1 wt-%, related to the total weight of polymer mixture (P), of PVC or c-PVC;
v. 0 wt-% to 35 wt-%, related to the total weight of polymer mixture (P), of polyolefins, hydrogenated EPDM or non-hydrogenated EPDM;
vi. 0 wt-% to 10 wt-%, related to the total weight of polymer mixture (P), of hydrogenated or non-hydrogenated styrene-butadiene copolymers comprising at least 15 wt-% butadiene based on the total weight of styrene-butadiene copolymer; and
vii. 0 wt-% to 5 wt-%, related to the total weight of polymer mixture (P), of polyesters, polycarbonates or polyamides,
provided that the amount of components selected from groups iv., v., vi. and vii. sums up to at least 0.1 wt-%, related to the total weight of polymer mixture (P).

11. The process according to claim 1 , wherein the component (C) contains
viii. 0 wt-% to 10 wt-%, related to the total weight of polymer mixture (P), of water;
ix. 0 wt-% to 1 wt-%, related to the total weight of polymer mixture (P), of halogenated substances;
x. 0 wt-% to 10 wt-%, related to the total weight of polymer mixture (P), of inorganic or organic dyes or pigments;
xi. 0 wt-% to 10 wt-%, related to the total weight of polymer mixture (P), of lubricants, waxes or amides of long chain organic acids;
xii. 0 wt-% to 5 wt-%, related to the total weight of polymer mixture (P), of emulsifiers or soaps;
xiii. 0 wt-% to 5 wt-%, related to the total weight of polymer mixture (P), of paper or cardboard;
xiv. 0 wt-% to 1 wt-%, related to the total weight of polymer mixture (P), of metals, metal oxides or metal salts;
xv. 0 wt-% to 10 wt-%, related to the total weight of polymer mixture (P), of further fillers; and
xvi. 0 wt-% to 2 wt-%, related to the total weight of polymer mixture (P), of other additives such as UV stabilizers, HALS, hindered phenols, disulfite stabilizers, quenchers or absorbers,
provided that the amount of components selected from groups viii., ix., x., xi., xii., xiii., xiv., xv., and xvi. sums up to at least 0.1 wt-%, related to the total weight of polymer mixture (P).

12. The process according to claim 1 , wherein shear force and/or pressure are additionally applied to the polymer mixture (P) in the pyrolysis reactor in step I).

13. The process according to claim 1 , wherein at least 3 theoretical stages are located below the position at which the condensed substances from step II) are introduced into the distillation column (X) in step III) and at least 17 theoretical stages are located above the position at which the condensed substances from step II) are introduced into the distillation column (X) in step III).

14. The process according to claim 1 , where

Assignees

• Ineos Styrolution Group Gmbh

Inventors

• Niessner Norbert
• Wilhelmus Bianca
• Kerschbaumer Hannes
• Verswyvel Michiel
• Inghelbrecht Petra
• Cochran Thomas W
• Shon Kyungho
• Abboud Mohammed
• Cuetos Ricardo
• Schwaben Hans-Dieter
• Kathmann Jens
• Urquhart Thad
• Brown Timothy A
• Wong Tim
• De Vet Walter
• Schmidt Hans-Werner
• Schedl Andreas
• Kolb Tristan

Classifications

• C07C4/22 Primary

  by depolymerisation to the original monomer, e.g. dicyclopentadiene to cyclopentadiene · CPC title

• B01D3/143

  by two or more of a fractionation, separation or rectification step · CPC title

• B01D3/4227

  Head- and bottom stream · CPC title

• C07C7/04

  by distillation · CPC title

• C08J11/12

  by dry-heat treatment only · CPC title