CHEMICAL RECYCLING METHOD FOR POLYESTER BASED TEXTILE AND/OR PACKAGING WASTE

Abstract

Chemical recycling method for polyester based textile and/or packaging waste. In the method, colorless bis hydroxyethyl terephthalate (BHET) is obtained from packaging waste containing polyester and/or textile produced from at least 50% polyester, having at most 50,000 ppm coloring agent or filler material, to be used in the production of packaging materials and/or textile materials such as yarns based on recycled colorless polyethylene terephthalate (PET), fabric, nonwoven (nonwoven fabric). The method also enables the re-production of PET from the BHET.

Claims

1. A chemical recycling method that enables to obtain colorless bis hydroxyethyl terephthalate (BHET) from packaging waste containing polyester and/or textiles produced from at least 50% polyester, comprising at most 50,000 ppm coloring agent or filler material, to be used in the production of packaging materials and/or textile materials such as yarns based on recycled colorless polyethylene terephthalate (PET), fabric, nonwoven (nonwoven fabric), the method comprising the following process steps: a) monoethylene glycol (MEG) at the ratio of 2:1-7:1 and said packaging waste is transferred into a depolymerization reactor, b) preferably zinc acetate or sodium hydroxide is added into the reactor as a catalyst and the reaction is kept for 5 hours at a temperature of 180-270° C. and following this the BHET-MEG mixture containing a coloring agent is obtained, c) feeding the BHET-MEG mixture cooled below a temperature of 50° C. in order to separate BHET from MEG into the decanter separator that has a G force adjusted to a range of 1000-9000×g or into a horizontal vacuum belt filter or filter press, characterized in that during the steps of b and c, the following process steps are carried out: in the case that BHET-MEG mixture contains cotton, the mixture is passed through a filter at a temperature within the range of 50-190° C. and the cotton is removed from the medium, feeding said mixture into a disk type centrifuge having a two phase separation system, that has a G force value adjusted at a range of 1000-12000 xg, having an exit temperature of 120±60° C., in order to ensure maximum separation of the coloring agent from the mixture, separating from the centrifuge separator the BHET and MEG mixture as the liquid phase and an amount of BHET and dye as the solid phase, mixing the BHET-MEG mixture in the heating tank at a temperature of 120±60° C. for 30 minutes in order to dissolve the partially recrystallized BHET inside MEG following centrifuge, mixing the mixture for 45 minutes at a temperature within the range of 120±60° C. by adding powdered activated carbon at a range of 1-10× of the dye to the mixture or passing the mixture through an activated carbon column, feeding said mixture into a disk type centrifuge, that has a G force value adjusted at a range of 1000-12000 xg, having an exit temperature of 120±60° C., in order to ensure maximum separation of the activated carbon as the solid phase from the BHET-MEG mixture, and passing the BHET-MEG mixture that is separated as the liquid phase through a filter and delivering it into the cooling tank.

2. A method according to claim 1, wherein said coloring agent has a maximum ratio of 50,000 ppm.

3. A method according to claim 1, wherein said coloring agent is a pigment, solvent dye or disperse dye.

4. A method according to claim 3, wherein the molecular weight of the solvent dye is at least 300 g/mol.

5. A method according to claim 3, wherein the molecular weight of the disperse dye is at least 300 g/mol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0037] In this detailed description the chemical recycling method for polyester based textile and/or packaging waste is described with examples that shall not limit the scope of the invention and which have been intended to only clarify the subject matter of the invention.

[0038] The invention is related to a chemical recycling method that enables to obtain colorless bis hydroxyethyl terephthalate (BHET) from packaging waste containing polyester and/or textile produced from at least 50% polyester, comprising at most 50,000 ppm coloring agent or filler material, to be used in the production of packaging materials and/or textile materials such as yarns based on recycled colorless polyethylene terephthalate (PET), fabric, nonwoven (nonwoven fabric).

[0039] In the method subject to the invention, recyclable textile products can contain a maximum of 50% cotton or other cellulosic fibers. The ratios of the coloring agent within the polyester based packaging are around 100 ppm while this ratio varies between 1000 ppm and 50,000 ppm in textile products. The waste materials that are mentioned can comprise pigments as coloring agents, a solvent dye dissolved in polymer or dispersed dye.

[0040] Solvent dyes and disperse dyes are high solubility dyes in polyester and monoethylene glycol, and they generally remain as significantly dissolved rather than particles inside the polymers to which they are added to. In order to carry out the method subject to the invention, the highly soluble solvent and disperse dyes must have a molecular size of 300 g/mol and above. The pigments and filler materials however, are available inside the polymer as particles.

[0041] In the preferred embodiment of the invention, the waste materials that can be used to produce recycled colorless polyethylene terephthalate (PET) based yarns and/or packaging materials, can comprise solvent blue 122, solvent blue 104, solvent brown 53, solvent green 3, pigment black 7, pigment blue 15:1, pigment blue 15:3 or pigment green 7 as coloring agents.

[0042] The Chemical Recycling Method Subject to the Invention is as Follows; [0043] Monoethylene glycol (MEG) at the ratio of 2:1-7:1 and textile and/or polyester based packaging waste , made of at least 50% polyester material is transferred into a depolymerization reactor, [0044] Preferably zinc acetate or sodium hydroxide is added into the reactor as a catalyst and the reaction is kept for 5 hours at a temperature of 180-270° C. and the depolymerization process is completed,

[0045] (In this process step depolymerization reaction can be carried out without using a catalyst) [0046] At the end of the depolymerization process a mixture formed of bishydroxyethylterephthalate (BHET), MEG and a coloring agent is obtained,

[0047] (At the end of this process BHET monomer that has a melting point between 90-120° C. and BHET dimer, trimer and oligomer having a melting point within the range of 120-170° C. at maximum 10% is obtained). [0048] The BHET-MEG mixture is filtered at a temperature between 50-190° C. and cotton sourced from the textile product is removed, [0049] The remaining mixture is fed into a disk type centrifuge having a two phase separation system, that has a G force value adjusted at a range of 1000-12000×g, having an exit temperature of 120±60° C., in order to ensure maximum separation of the coloring agent, [0050] BHET and MEG mixture as the liquid phase and the coloring agent and an amount of BHET as the solid phase are separated from the centrifuge separator. [0051] Mixing the BHET-MEG mixture in the heating tank at a temperature of 120±60° C. for 30 minutes in order to dissolve the partially re-crystallized BHET inside MEG following centrifuge, [0052] Powdered activated carbon at a range of 1-10× of the dye is added into the mixture. This mixture is mixed for 45 minutes at a temperature within the range of 120±60° C. or it is passed through the activated carbon column, [0053] The mixture is re-fed into a disk type centrifugal separator and the activated carbon is separated from the BHET-MEG mixture a solid phase by applying 1000-9000×g G force at an exit temperature of 120±60° C., and the BHET-MEG mixture is passed through a filter and is delivered into a cooling tank, [0054] The BHET-MEG mixture is fed into a decanter separator and it is separated from BHET-MEG by applying 1000-6000×g G force at a temperature of 50° C.

[0055] In the chemical recycling method of the invention, Alfa Laval type HCHPX 513SGD-35CGRXT or Haus IBA 4021-K40 models can be used as disk type centrifuge and Haus DDI 2342 can be used as a decanter separator. However the disk type centrifuge and decanter separator models are not limited to these.

[0056] In a preferred embodiment of the invention AquaSorb™ MP25 can be used as powdered activated carbon.

[0057] In a preferred embodiment of the invention, a horizontal vacuum belt filter or filter press can also be used to separate BHET from the BHET-MEG mixture that has been cooled below 10° C.

[0058] While the invention enables maximum separation of the dye from the BHET-MEG mixture that is obtained by depolymerizing polyester-based packaging waste and/or textiles that are produced from at least 50% polyester material, with monoethylene glycol, the obtained

[0059] BHET-MEG mixture is fed into the centrifugal separator that is utilized for sold-liquid phase separation in order to ensure minimum precipitation of BHET. While the liquid phase consisting of the BHET-MEG mixture exits the liquid phase outlet of the centrifugal separator, the dye is received from the solid phase outlet as the solid phase.

[0060] In the chemical recycling method subject to the invention, the exit temperature and G force value of the centrifugal separator having a two-phase separation system are the parameters that provide efficient separation. These parameters allow the dye to be separated from the BHET-MEG mixture at a maximum rate and they also enable minimum precipitation of BHET during this separation process. The exit temperature of the centrifugal separator having a two-phase separation system is set to 120±60° C. before the separation process begins, and the G force value is adjusted to the range of 1000-12000×g.

[0061] The mixture that is fed into the centrifugal separator having a two-phase separation system consists of 20% BHET monomer, 78.5% MEG and 0.3% dye. At the end of the centrifuge process, the BHET-MEG mixture that is separated as liquid phase is formed of 20.4% BHET monomer and 79.6% MEG. The part that is separated as the solid phase can vary between 2-5%. 5-10% of the part separated as solid phase consists of coloring agents, 70% is MEG and 20-25% is BHET monomers, dimers, trimers and oligomers.

[0062] In a preferred embodiment of the invention a centrifugal separator system having a three phase separation system that can separate three phases at the same time (solid-liquid-liquid) can also be used. In this system, it must be noted that the exit temperature should be minimum 115° C. By means of this system BHET, MEG and the coloring agent is separated in one step. BHET and MEG are separated as liquid phase by density difference and the dye is separated as the solid phase. BHET and MEG are separated as liquid-liquid due to their density differences.

[0063] The BHET-MEG mixture obtained as a result of depolymerization reaction is fed into the disc-type three-phase centrifugal separator whose exit temperature is adjusted to 160±40° C., and the G force value is adjusted between the ranges of 1000-12000×g. BH ET and MEG as the liquid phase the coloring agent and an amount of BHET as the solid phase are separately separated from the centrifuge separator. At the last step, powdered activated carbon is added into the dye at a range of 1-10× to the BHET phase and the mixture is mixed for 45 minutes at 120±60° C. or the BHET phase is passed through an activated carbon column.

EXAMPLE 1

[0064] Fabric features; 100% polyester based fabric comprising 1.5% pigment

[0065] Glycolysis Reaction (Depolymerization)

[0066] First of all 21875 gr monoethylene was placed into the reactor and following this 3125 gr polyester fabric has been added into the reactor.

[0067] 15.6 g sodium hydroxide was fed. The temperature was set to 230° C. The pressure is between 3.0-3.5 bars at this temperature. The mixture was kept for 5 hours under these conditions. Following this the pressure was made atmospheric and glycol was collected. The pressure dropped and therefore the temperature dropped down to 195° C. Due to the glycol collected from the last mixture, the % amount of bishydroxyterephthalate increased to 20%.

[0068] As a result of the glycolysis reaction 97% mono BHET, 3% dimer, timer and oligomer was obtained. The obtained BHE had a melting point of 110° C.

[0069] Color Separation by Means of Centrifuge

[0070] Sigma 2-6 compact centrifuge has been used as a centrifuge. The 21 kg BHET-MEG dye mixture produced during the depolymerization step, has been fed into the centrifuge under different conditions. The conditions mentioned are given in detail below.

[0071] Examination of the G Force Value Effect on Color Separation Performance

[0072] The sample prepared in Example 1 was heated and was subjected to a centrifuge process at different revolutions for 3 minutes by keeping the final sample temperature in the range of 70-130° C. Under these conditions, % amount remaining at the bottom of the tube and the amount of BHET that has precipitated in this section was measured. At the same time the color intensity of the supernatant was measured. The color intensity has been measured with the datacolor SF 600 X device. As reference 500 ppm Pigment Red 214 has been prepared inside monoethylene glycol. The sample was heated to 80° C. and the % color intensities of the supernatants of the sample are measured according to temperature reference, and the effect of the G force parameter on color separation is given in table-1.

TABLE-US-00001 TABLE-1 Affect of the G force parameter on color separation Exit Unprecipitated Speed Temperature section G force (xg) (rpm) (° C.) % BHET Loss % Color Intensity 1459 3000 116 3.6 16.27 648 2000 120 — 30.3 1459 3000 118 3.63 15.4 2594 4000 115 5.76 10.2

[0073] As it can be understood from the information given in Table 1, as G force increases the color of the supernatant decreases.

[0074] Examination of the Centrifuge Exit Temperature Effect on Color Separation Performance

[0075] The samples were centrifuged at different temperatures by leaving them to wait for 3 minutes at 3000 rpm speed (1459 xg G force). The effect of the exit temperature of the centrifuge to color separation has been given in table-2.

TABLE-US-00002 TABLE-2 Effect of the exit temperature of the centrifuge to color separation % Color Intensity at Temperature the Un-precipitated section (° C.) % BHET Loss (according to 500 ppm Red 214) 120 4.25 16.27 90 6.42 18.73 80 7.44 66.58 70 6.17 62.60 60 6.42 95.64 50 5.64 97.05

[0076] As it can be understood from the information given in Table-1, as the temperature falls, the precipitation rate of the coloring agents is reduced. Moreover it has been observed that more amounts of BH ET crystallizes and precipitates as the temperature falls.

[0077] Conditioning

[0078] As a result of the centrifuge separation process, the mixture separated from the dye and impurities was mixed for 30 minutes at 120° C. in a mixer beaker and it has been enabled for BHET to be completely re-dissolved in MEG.

[0079] Color Separation with Activated Carbon

[0080] 1.2% powdered activated carbon called Aquasorb MP 25 was added to the conditioned mixture. The mixture was mixed for 45 minutes at 120° C. Following this, the mixture was centrifuged at 3000 revolutions for 3 minutes at a G force of 1459 such that the exit temperature is 90° C. The activated carbon has been separated from the mixture. The activated carbon particles at ppm level that have not been separated are passed through a 1 micron filter and were separated at 90° C.

[0081] Separation of the BHET-MEG Mixture

[0082] The BHET-MEG mixture has been cooled to 10° C. and colorless solid form BHET was obtained from a 3000 rpm (1459×g G force) centrifuge.

EXAMPLE 2

[0083] Fabric features; 70% polyester and 30% cotton based fabric comprising 1.5% pigment Red 214

[0084] Glycolysis Reaction (Depolymerization)

[0085] First of all 21875 gr monoethylene was placed into the reactor and following this 3125 gr fabric has been added into the reactor. 15.6 g sodium hydroxide was fed. The temperature was set to 230° C. The pressure is between 3.0-3.5 bars at this temperature. The mixture was kept for 5 hours under these conditions and following this the pressure was made atmospheric and glycol was collected. The pressure dropped and therefore the temperature dropped down to 195° C. Due to the glycol collected from the last mixture, the % amount of bishydroxyterephthalate increased to 14%.

[0086] The mixture was passed through a 1000 micron metal filter and cotton was separated and the other processes were carried as in example 1.

EXAMPLE 3 (INDUSTRIAL SIZE TRIAL)

[0087] Fabric features; 100% polyester based fabric comprising 1.5% pigment Red 214

[0088] Glycolysis Reaction (Depolymerization)

[0089] First of all 4375 kg monoethylene glycol was placed into the reactor and following this 625 kg polyester fabric has been added into the reactor. 3.125 kg sodium hydroxide was fed. The temperature was set to 230° C. The pressure is between 3.0-3.5 bars at this temperature. The mixture was kept for 5 hours under these conditions and following this the pressure was made atmospheric and glycol was collected. The pressure dropped and therefore the temperature dropped down to 185° C. Due to the glycol collected from the last mixture, the % amount of bishydroxyterephthalate increased to 19%.

[0090] Color Separation by Means of Centrifuge

[0091] The product cooled in the reactor to 90-95° C. was pressed into a disk type centrifuge called IBA 4021-K40. The BHET-MEG dye mixture produced at the depolymerization phase was fed. The centrifuge was operated at 9000 G force. The time the mixture was kept in the centrifuge was calculated to be approximately 30 seconds. The color intensity of the obtained BHET MEG mixture was measured as 16.5%.

[0092] Conditioning

[0093] As a result of the centrifuge separation process, the mixture separated from the dye and impurities was mixed for 30 minutes at 120° C. by being re-fed into the reactor, and it has been enabled for BHET to be completely re-dissolved in MEG.

[0094] Color Separation with Activated Carbon

[0095] 1.2% powdered activated carbon called Aquasorb MP 25 was added to the conditioned mixture. The mixture was mixed for 45 minutes at 120° C. Following this, the mixture was fed at 95° C. into a Haus IBA 4021-K40 centrifugal separator separation at 9000 xg G force from the activated carbon was performed. The trace amount of activated carbon particles suspended was passed through a 1 micron filter and was separated at 90° C.

[0096] Separation of the BHET-MEG Mixture

[0097] The BHET-MEG mixture was cooled to 10° C. The mixture was taken from the reactor and placed into a Haus DDI 2342 decanter type separator. 6000 xg G force was applied and BHET-MEG was separated and colorless solid form of BHET was obtained.

[0098] BHET Monomer Polymerization

[0099] 17.4 kg from the obtained BHET monomer was taken and it has been loaded into a 40 lt volume pilot reactor. The reactor temperature was adjusted to 240° C. and the mixing speed was adjusted as 10 hz. After 30 minutes the mixing speed was adjusted to 50 hz value. When the temperature reached 135° C., 4.4 gr antimony in 600 gr MEG and 0.84 gr H.sub.3PO.sub.4 was fed into the reactor. After 50 minutes the reactor temperature was adjusted to 270° C. When the reactor temperature reached 260° C. after 1 hour, the vacuum that was adjusted to decrease to 1 mbar in 77 minutes was started. The final temperature was applied as 288° C. The IV value of the PET obtained was measured as 0.672 dl/g; and the amount of % DEG was measured as 0.78 and the number of carboxyl end groups were measured as 17.70 eq/ton. The L color of the obtained polymer was measured as 61.77, color a as −1.16 and color b as 10.6.

[0100] The polymer that was produced was tested in a Collin FT E20T-MP-IS test device, according to the EN 13900-5 standards. The filter test result measured 0.117 bar/g in a 5 micron filter.

[0101] The produced polymer was dried under vacuum of 13 mbars at 160° C. for 4 hours, and using this polymer, 3.5 denier yarn was produced at 285° C. in the pilot yarn machine called Busschaert B-8540. The L color of the produced yarn was measured as 91.75, color “a” was −0.39 and color “b” was 2.89.

[0102] In present applications, whereas only colorless PET yarn from polyester materials can be obtained comprising ppm levels of pigments as coloring agents from only clear PET bottles by means of chemical recycling; by using the method of the invention, colorless BHET has been able to be produced in order to obtain colorless PET yarn and/or packaging material via chemical recycling from textile products and/or polyester based packaging waste made of at least 50% polyester material.

[0103] By means of the centrifuge parameters determined in the method of the invention, the coloring agents inside the textile products and polyester based packaging waste can be separated at a maximum amount at the solid phase. Besides this, by means of a filtering process, cotton can be separated which is available in the medium as an impurity and which is sourced by the textile product.

[0104] During the use of an activated carbon column in the method of the present invention, unlike the existing applications, BHET is fully dissolved inside MEG in a conditioning tank to ensure that BHET is re-dissolved after the centrifugation process and to prevent BHET from adhering to the activated carbon column. In the preferred embodiment, powdered activated carbon can be included in the system instead of the activated carbon column. Following this process, the activated carbon can be separated by a centrifugal separator.