METHOD FOR THE DEPOLYMERISATION OF POLYSTYRENE IN THE PRESENCE OF FOREIGN POLYMERS

Abstract

The invention relates to a method for producing styrene monomers by the depolymerisation of polystyrene in the presence of foreign polymers, such as polyolefins. Said method comprises the following steps: a) introducing a polymer composition (A) containing: I) 10 to 99.5% by weight, based on the polymer composition (A), of polystyrene (I); and II) 0.1 to 89.9% by weight of polyolefin (II); and/or III) 0.1 to 4.9% by weight of acrylonitrile-based polymer (III); and/or IV) 0.1 to 4.9% by weight of polyester (IV), into the reaction zone (R) of a pyrolysis reactor (P); b) thermal cracking the polystyrene contained in the polymer composition (A) in the reaction zone (R) of the pyrolysis reactor (P) at a temperature of between 400-1000° C., c) removing the product mixture (G) obtained from the reaction zone (R), d) cooling of the product mixture (G), and e) separating the styrene monomers from the further components.

Claims

1-15. (canceled)

16. A process for the production of styrene monomers by depolymerization of a polystyrene-containing polymer composition, comprising the steps of: a) introducing a polymer composition (A) containing: I) 10% to 99.5% by weight of a polystyrene (I), based on the total weight of the polymer composition (A); and II) 0.1% to 89.9% by weight of a polyolefin (II), based on the total weight of the polymer composition (A); and/or III) 0.1% to 4.9% by weight of an acrylonitrile-based polymer (III), based on the total weight of the polymer composition (A); and/or IV) 0.1% to 4.9% by weight of a polyester (IV), based on the total weight of the polymer composition (A), into a reaction zone (R) of a pyrolysis reactor (P); b) thermally cleaving the polystyrene (I) present in the polymer composition (A) in the reaction zone (R) of the pyrolysis reactor (P) at a temperature of from 400° C. to 1000° C. to obtain a product mixture (G) containing styrene monomers and further components; c) withdrawing the product mixture (G) obtained in step b) from the reaction zone (R) of the pyrolysis reactor (P); d) cooling the product mixture (G) withdrawn in step c) to obtain a condensed product mixture (K) containing styrene monomers and further components; and e) separating the styrene monomers from the further components of the condensed product mixture (K) obtained in step d), wherein an average residence time (Z) of the polymer composition (A) in the reaction zone (R) of the pyrolysis reactor (P) is from 0.01 s to 10 s.

17. The process of claim 16, wherein the polyolefin (II) is polyethylene (PE) and/or polypropylene (PP), and/or the acrylonitrile-based polymer (Ill) is acrylonitrile-butadiene-styrene graft copolymer (ABS), and/or the polyester (IV) is polyethylene terephthalate (PET).

18. The process of claim 16, wherein the polymer composition (A) contains the polystyrene (I) in an amount of from 85% to 99.5% by weight, based on the total weight of the polymer composition (A), and the polyolefin (II) in an amount of from 0.1% to 15% by weight, based on the total weight of the polymer composition (A), and/or the acrylonitrile-based polymer (III) in an amount of from 0.1% to 2% by weight, based on the total weight of the polymer composition (A), and/or the polyester (IV) in an amount of from 0.1% to 2% by weight, based on the total weight of the polymer composition (A).

19. The process of claim 16, wherein the temperature in the reaction zone (R) of the pyrolysis reactor (P) is 580° C. to 630° C. and the average residence time (Z) of the polymer composition (A) in the reaction zone (R) of the pyrolysis reactor (P) is 0.4 s to 0.6 s.

20. The process of claim 16, wherein the condensed product mixture (K) obtained in step d) contains from 75% to 99% by weight of styrene and 1% to 25% by weight of the further components, based on the total weight of the condensed product mixture (K).

21. The process of claim 16, wherein the pyrolysis reactor (P) is a fluidized bed reactor.

22. The process of claim 16, wherein at least a portion of the further components obtained in step e) is recycled into the reaction zone (R) of the pyrolysis reactor (P).

23. The process of claim 22, wherein the further components obtained in step e) which are recycled into the reaction zone (R) of the pyrolysis reactor (P) consist essentially of styrene oligomers.

24. The process of claim 16, wherein the polystyrene (I) component in the polymer composition (A), which in step a) is introduced into the reaction zone (R) of the pyrolysis reactor (P), consists essentially of general purpose polystyrene (GPPS).

25. The process of claim 16, wherein in step d) the product mixture (G) that is withdrawn in step c) is cooled to a temperature of from 0° C. to 50° C.

26. The process of claim 16, wherein the separation of the styrene monomers in step e) comprises a step of fractional distillation.

27. The process of claim 21, wherein the fluidized bed reactor comprises a silicon carbide fluidized bed in the reaction zone (R).

28. The process of claim 22, wherein the recycling of the further components into the reaction zone (R) of the pyrolysis reactor (P) is continuous.

29. A process for the depolymerization of a polystyrene-containing polymer composition (A), comprising the use of a fluidized bed reactor with a temperature in a reaction zone (R) of the fluidized bed reactor of from 400° C. to 1000° C. and with an average residence time (Z) of the polystyrene-containing polymer composition (A) in the reaction zone (R) of from 0.01 s to 10 s, wherein the polystyrene-containing polymer composition (A) on entry into the reaction zone (R) of the reactor contains: I) 10% to 99.5% by weight of a polystyrene (I), based on the total weight of the polystyrene-containing polymer composition (A); and II) 0.1% to 89.9% by weight of a polyolefin (II), based on the total weight of the polystyrene-containing polymer composition (A); and/or III) 0.1% to 4.9% by weight of an acrylonitrile-based polymer (III), based on the total weight of the polystyrene-containing polymer composition (A); and/or IV) 0.1% to 4.9% by weight of a polyester (IV), based on the total weight of the polystyrene-containing polymer composition (A).

30. The process of claim 29, wherein the fluidized bed reactor comprises a silicon carbide fluidized bed.

31. An apparatus for conducting the process of claim 16, wherein the reaction zone (R) and the pyrolysis reactor (P) are configured such that gentle depolymerization of polystyrene is possible.

32. The apparatus of claim 31, wherein the pyrolysis reactor (P) is a fluidized bed reactor.

33. The apparatus of claim 32, wherein the fluidized bed reactor comprises a silicon carbide fluidized bed.

34. The process of claim 16, wherein the polymer composition (A) contains the polystyrene (I), the polyolefin (II), the acrylonitrile-based polymer (III), and the polyester (IV).

35. The process of claim 34, wherein the polyolefin (II) is polyethylene (PE) and/or polypropylene (PP), the acrylonitrile-based polymer (III) is acrylonitrile-butadiene-styrene graft copolymer (ABS), and the polyester (IV) is polyethylene terephthalate (PET).

Description

EXAMPLES

[0118] The polymer is metered from an inertized reservoir vessel (B101) via volumetric metering into a gas jet, which conveys the particles pneumatically into the reaction zone of a fluidized bed reactor (R101) containing SiC particles. The heat energy is input into the reaction zone via resistive heating conductors through the metallic reactor wall.

[0119] The steam for producing the fluidized bed is provided by an evaporator (D101) and is brought to the desired temperature via a steam superheater (E102).

[0120] In the reaction zone, the SiC fluidized bed is produced with the steam and the polymer particles conveyed in pneumatically are mixed in the fluidized bed and ultimately depolymerized.

[0121] The product mixture of the depolymerization process from (R101) is cooled to below 50° C. in the column (K101) in a water mist. In the process, the condensable constituents are condensed according to their vapor pressures and are collected with the water in the cooled bottom. Solid particles are also deposited with the mist according to their coalescence tendency. Floating, water-insoluble constituents are transferred into a buffer vessel via a skimmer system. Samples are filled of the concentrated, organic fraction of the condensed product mixture. These are measured by gas chromatography.

[0122] The water from the condensation process is cooled via a heat exchanger and then sent back into the cooling column (K101) using the pump. Solids are optionally removed via a solid-liquid filter.

Examples 1.1 and 1.2

[0123] A polymer composition consisting of 99% by weight of an amorphous polystyrene (GPPS) (INEOS Styrolution, Frankfurt) with a melt volume-flow rate (Melt Volume Rate 200/5 kg load, ISO 1133) of around 28 cm.sup.3/10 min and 1% by weight of acrylonitrile-butadiene-styrene graft polymer (ABS from INEOS Styrolution, Frankfurt) with a melt volume-flow rate (Melt Volume Rate 220/10 kg load, ISO 1133) of around 5.5 cm.sup.3/10 min was depolymerized in the apparatus described above under various conditions.

[0124] Here, the temperature in the reaction zone of the fluidized bed reactor (R101) was varied in the range from 550° C. to 650° C. The concentration of the polymer composition in the reaction zone was maintained at 5%, based on the total charge of the reactor, consisting of SiC particles and polymer particles. The yields of styrene monomers depending on the reaction conditions are presented in table 1. The compositions of the pyrolysis oil are presented in table 2.

Comparative Example 1

[0125] Example 1 was repeated with a polymer composition consisting of 95% by weight of an amorphous polystyrene (GPPS) (INEOS Styrolution, Frankfurt) with a melt volume-flow rate (Melt Volume Rate 200/5 kg load, ISO 1133) of around 28 cm.sup.3/10 min and 5% by weight of acrylonitrile-butadiene-styrene graft polymer (INEOS Styrolution, Frankfurt) with a melt volume-flow rate (Melt Volume Rate 220/10 kg load, ISO 1133) of around 5.5 cm.sup.3/10 min. The yield of styrene monomers is presented in table 1. The composition of the pyrolysis oil (condensate oil) is presented in table 2.

Comparative Example 2

[0126] Example 1 was repeated with a polymer composition consisting of 100% by weight of an amorphous polystyrene (GPPS) (INEOS Styrolution, Frankfurt) with a melt volume-flow rate (Melt Volume Rate 200/5 kg load, ISO 1133) of around 28 cm.sup.3/10 min. The yield of styrene monomers is presented in table 1. The composition of the pyrolysis oil is presented in table 2.

Example 2

[0127] Example 1 was repeated with a polymer composition consisting of 95% by weight of an amorphous polystyrene (GPPS) (INEOS Styrolution, Frankfurt) with a melt volume-flow rate (Melt Volume Rate 200/5 kg load, ISO 1133) of around 28 cm.sup.3/10 min and 5% by weight of polyethylene (LDPE, 2102 type, SABIC). The yield of styrene monomers is presented in table 1. The composition of the pyrolysis oil is presented in table 2.

Example 3

[0128] Example 1 was repeated with a polymer composition consisting of 90% by weight of an amorphous polystyrene (GPPS) (INEOS Styrolution, Frankfurt) with a melt volume-flow rate (Melt Volume Rate 200/5 kg load, ISO 1133) of around 28 cm.sup.3/10 min and 10% by weight of polyethylene (LDPE, 2102 type, SABIC).

[0129] The yield of styrene monomers is presented in table 1. The composition of the pyrolysis oil is presented in table 2.

Example 4

[0130] Example 1 was repeated with a polymer composition consisting of 95% by weight of an amorphous polystyrene (GPPS) (INEOS Styrolution, Frankfurt) with a melt volume-flow rate (Melt Volume Rate 200/5 kg load, ISO 1133) of around 28 cm.sup.3/10 min and 5% by weight of polypropylene (579s type, SABIC). The yield of styrene monomers is presented in table 1. The composition of the pyrolysis oil is presented in table 2.

Example 5

[0131] Example 1 was repeated with a polymer composition consisting of 90% by weight of an amorphous polystyrene (GPPS) (INEOS Styrolution, Frankfurt) with a melt volume-flow rate (Melt Volume Rate 200/5 kg load, ISO 1133) of around 28 cm.sup.3/10 min and 10% by weight of polypropylene (579s type, SABIC). The yield of styrene monomers is presented in table 1. The composition of the pyrolysis oil is presented in table 2.

Example 6

[0132] Example 1 was repeated with a polymer composition consisting of 95% by weight of an amorphous polystyrene (GPPS) (INEOS Styrolution, Frankfurt) with a melt volume-flow rate (Melt Volume Rate 200 /5 kg load, ISO 1133) of around 28 cm.sup.3/10 min and 5% by weight of titanium dioxide. The yield of styrene monomers is presented in table 1. The composition of the pyrolysis oil is presented in table 2.

Example 7

[0133] Example 1 was repeated with a polymer composition consisting of 98% by weight of an amorphous polystyrene (GPPS) (INEOS Styrolution, Frankfurt) with a melt volume-flow rate (Melt Volume Rate 200/5 kg load, ISO 1133) of around 28 cm.sup.3/10 min and 2% by weight of carbon black.

[0134] The yield of styrene monomers is presented in table 1. The composition of the pyrolysis oil is presented in table 2.

TABLE-US-00001 TABLE 1 Results of the pyrolysis of the polymer compositions Proportion Average by mass of the Styrene Temperature residence condensate oil concentration in the time in the based on in the reaction zone reaction zone the mass used condensate oil Example Polymer [° C.] [s] [% by weight] [% by weight] 1.1 99% GPPS/ 550 0.51 55.6 69.8 1% ABS 1.2 95% GPPS/ 600 0.51 56.7 71.6 5% ABS 2 95% GPPS/ 600 0.51 56.4 73.9 5% LDPE 3 90% GPPS/ 600 0.51 66.8 72.8 10% LDPE 4 95% GPPS/ 600 0.51 85.9 71.9 5% PP 5 90% GPPS/ 600 0.51 85.1 73.6 10% PP 6 95% GPPS/ 600 0.51 41.6 77.5 5% TiO.sub.2 7 98% GPPS/ 600 0.51 76.5 72.8 2% carbon black Comparative 95% GPPS/ 600 0.51 0.0 n/a example 1 5% ABS Comparative 100% GPPS 600 0.51 65.9 83.2 example 2

TABLE-US-00002 TABLE 2 Composition of the pyrolysis oil obtained Concentration Styrene Dimer Trimer of other concentration in concentration in concentration in compounds in condensate oil condensate oil condensate oil condensate oil Example [% by weight] [% by weight] [% by weight] [% by weight] 1.1 69.8 7.3 9.7 13.2 1.2 71.6 9.2 0.6 18.6 2 73.9 8.7 0.7 16.8 3 72.8 8.1 0.6 18.5 4 71.9 8.1 0.6 19.4 5 73.6 7.3 0.5 18.7 6 77.5 8.0 0.4 14.1 7 72.8 8.7 0.6 17.8 Comparative 1 No pyrolysis No pyrolysis No pyrolysis No pyrolysis oil formed oil formed oil formed oil formed Comparative 2 83.2 6.0 0.6 10.3

Explanation of the Figures

[0135] FIG. 1 shows a flow diagram of the pilot plant for producing styrene monomers by de-polymerization of polystyrene-containing polymer compositions

[0136] FIG. 2 shows an overview of the styrene concentration in the condensate oil.

[0137] FIG. 3 shows the dependence of the pyrolysis oil composition on the temperature for a polymer composition of 99% by weight GPPS and 1% by weight ABS.

[0138] FIG. 4 shows the dependence of the pyrolysis oil composition on the polymer composition for an ABS content of 0%, 1% and 5% by weight.

[0139] FIG. 5 shows the dependence of the pyrolysis oil composition on the polymer composition in the case of 0%, 5% and 10% by weight of LDPE and/or PP.

[0140] FIG. 6 shows the dependence of the pyrolysis oil composition on the polymer composition in the case of the addition of TiO.sub.2/carbon black.