Method for degrading (co)polymers in an extruder and extruder for performing the method

Patent metadata

Field	Value
Publication number	US-9683065-B2
Application number	US-201514735284-A
Country	US
Kind code	B2
Filing date	Jun 10, 2015
Priority date	Dec 12, 2012
Publication date	Jun 20, 2017
Grant date	Jun 20, 2017

Abstract

The invention relates to a method for degrading (co)polymers in an extruder and an extruder suitable for performing said method.

First claim

The invention claimed is:

1. A method for degrading (co)polymers in an extruder ( 1 ), the method comprising the steps of:
a) supplying a (co)polymer by means of a charging opening ( 5 ) into a first extrusion section ( 21 ) of the extruder ( 1 );
b) degrading the (co)polymer under shear stress in the first extrusion section ( 21 ), in the presence of from 0.02 to 5 wt % of a compound containing peroxo or diazo group to produce a first degraded (co)polymer;
c) transferring the first degraded (co)polymer from the first extrusion section ( 21 ) into a second extrusion section ( 22 ) of the extruder ( 1 ), wherein the first extrusion section ( 21 ) is separated from the second extrusion section ( 22 ) by a sealing means ( 14 , 15 , 16 , 17 );
d) supplying oxygen gas into the second extrusion section ( 22 ) by means of a feed opening ( 12 ), wherein the feed opening ( 12 ) is arranged downstream of the sealing means ( 14 , 15 , 16 , 17 ) in the direction ( 27 ) of extrusion; and
e) further degrading the first degraded copolymer under shear stress in the second extrusion section ( 22 ), in the presence of an oxygen gas, in order to produce a second degraded (co)polymer,
with the provision that the sealing means ( 14 , 15 , 16 , 17 ) is suitable for preventing the escape of the oxygen gas from the charging opening ( 5 ).

2. The method according to claim 1 , characterized in that the (co)polymer is added under a protective gas atmosphere in the charging opening ( 5 ).

3. The method according to claim 2 , characterized in that the radical former is added in the first extrusion section ( 21 ) via the charging opening ( 5 ) and/or via a radical former adding means ( 11 ).

4. The method according to claim 3 , characterized in that the radical former is a peroxide.

5. The method according to claim 1 , characterized in that upon entry in the second extrusion section ( 22 ), the first degraded (co)polymer has a residual amount of radical formers that is less than 0.01 wt % with respect to the total amount of the first degraded (co)polymer.

6. The method according claim 1 , characterized in that the degradation of the (co)polymer in the first extrusion section ( 21 ) is carried out at a temperature of 100° C. to 320° C.

7. The method according to claim 6 , characterized in that the further degradation of the first degraded (co)polymer in the second extrusion section ( 22 ) is carried out at a temperature of 200° C. to 450° C.

8. The method according to claim 1 , characterized in that the supplied oxygen gas is pure oxygen or an oxygen-containing gas mixture, wherein said gas mixture comprises an oxygen content of at least 5 vol %.

9. The method according to claim 8 , characterized in that the supplied oxygen gas contains an ethylenically unsaturated carboxylic acid or derivatives.

10. The method according to claim 1 , characterized in that the oxygen gas prior to the addition has at least a temperature of 50° C.

11. The method according to claim 10 , characterized in that the oxygen gas is added at a pressure of at least 5 bar.

12. The method according to claim 1 , characterized in that the second degraded (co)polymer is transferred into another extrusion section ( 28 ), wherein the second extrusion section ( 22 ) is separated from the other extrusion section ( 28 ) by a sealing means ( 18 , 19 , 20 ) and the other extrusion section ( 28 ) comprises an additional charging opening ( 24 ) and/or feed opening ( 25 ).

13. The method according to claim 12 , characterized in that the sealing means ( 14 , 15 , 16 , 17 , 18 , 19 , 20 ) is formed by a return feeding element and/or a damming unit in the extruder screw ( 8 ).

14. The method according to claim 13 , characterized in that the second and/or other extrusion section ( 22 , 28 ) comprises a decomposition means ( 13 , 26 ) that is arranged downstream of the feed opening ( 5 , 25 ) in the direction ( 27 ) of extrusion in order to decompose the oxygen gas.

15. The method according to claim 14 , characterized in that after leaving the second or other extrusion section ( 22 , 28 ), the second degraded (co)polymer is transformed into a bulk material.

Assignees

• Henkel Ag & Co Kgaa

Inventors

• Kasper Dirk
• Brenger Andreas
• Thierbach Ilja

Classifications

• B29C48/40

  using two or more parallel screws {or at least two parallel non-intermeshing screws}, e.g. twin screw extruders · CPC title

• B29C48/53

  having a varying channel depth, e.g. varying the diameter of the longitudinal screw trunk · CPC title

• B29C48/268

  Throttling of the flow, e.g. for cooperating with plasticising elements or for degassing (flow control means B29C48/255) · CPC title

• B29C48/767

  through a degassing opening of a barrel · CPC title

• C08F8/50 Primary

  Partial depolymerisation · CPC title