NL2032662B1 - Method and apparatus for recycling of polyvinylchloride (PVC). - Google Patents
Method and apparatus for recycling of polyvinylchloride (PVC). Download PDFInfo
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- NL2032662B1 NL2032662B1 NL2032662A NL2032662A NL2032662B1 NL 2032662 B1 NL2032662 B1 NL 2032662B1 NL 2032662 A NL2032662 A NL 2032662A NL 2032662 A NL2032662 A NL 2032662A NL 2032662 B1 NL2032662 B1 NL 2032662B1
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- Prior art keywords
- pvc
- waste
- feed stream
- range
- extruder
- Prior art date
Links
- 238000000034 method Methods 0.000 title claims abstract description 31
- 238000004064 recycling Methods 0.000 title claims abstract description 16
- 239000004800 polyvinyl chloride Substances 0.000 title claims description 80
- 239000002699 waste material Substances 0.000 claims abstract description 32
- 238000001914 filtration Methods 0.000 claims abstract description 25
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000000155 melt Substances 0.000 claims abstract description 17
- 229920000642 polymer Polymers 0.000 claims abstract description 16
- 229920001971 elastomer Polymers 0.000 claims abstract description 14
- 239000005060 rubber Substances 0.000 claims abstract description 13
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 11
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 7
- 229910052751 metal Inorganic materials 0.000 claims abstract description 5
- 239000002184 metal Substances 0.000 claims abstract description 5
- 229920000915 polyvinyl chloride Polymers 0.000 claims description 76
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 18
- 239000004014 plasticizer Substances 0.000 claims description 17
- 229910052742 iron Inorganic materials 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 9
- -1 polyethylene Polymers 0.000 claims description 9
- 229910001385 heavy metal Inorganic materials 0.000 claims description 7
- 239000002738 chelating agent Substances 0.000 claims description 6
- 239000004698 Polyethylene Substances 0.000 claims description 5
- 239000004743 Polypropylene Substances 0.000 claims description 5
- XNGIFLGASWRNHJ-UHFFFAOYSA-L phthalate(2-) Chemical compound [O-]C(=O)C1=CC=CC=C1C([O-])=O XNGIFLGASWRNHJ-UHFFFAOYSA-L 0.000 claims description 5
- 229920003023 plastic Polymers 0.000 claims description 5
- 239000004033 plastic Substances 0.000 claims description 5
- 229920000573 polyethylene Polymers 0.000 claims description 5
- 229920001155 polypropylene Polymers 0.000 claims description 5
- 238000009413 insulation Methods 0.000 claims description 3
- 125000005498 phthalate group Chemical class 0.000 claims description 3
- 229910001220 stainless steel Inorganic materials 0.000 claims description 3
- 239000010935 stainless steel Substances 0.000 claims description 3
- 229910001111 Fine metal Inorganic materials 0.000 claims description 2
- 238000002347 injection Methods 0.000 claims description 2
- 239000007924 injection Substances 0.000 claims description 2
- 229920000098 polyolefin Polymers 0.000 claims description 2
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 claims description 2
- 229920002554 vinyl polymer Polymers 0.000 claims description 2
- 239000007787 solid Substances 0.000 abstract description 15
- 238000000926 separation method Methods 0.000 abstract description 9
- 239000002245 particle Substances 0.000 abstract description 8
- 239000000654 additive Substances 0.000 abstract description 3
- 239000012535 impurity Substances 0.000 abstract description 3
- 238000000605 extraction Methods 0.000 description 26
- 239000003381 stabilizer Substances 0.000 description 8
- 239000000463 material Substances 0.000 description 7
- 238000001125 extrusion Methods 0.000 description 6
- 238000009864 tensile test Methods 0.000 description 5
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 4
- WNLRTRBMVRJNCN-UHFFFAOYSA-L adipate(2-) Chemical compound [O-]C(=O)CCCCC([O-])=O WNLRTRBMVRJNCN-UHFFFAOYSA-L 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 4
- 238000009472 formulation Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 238000010276 construction Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 238000011084 recovery Methods 0.000 description 3
- 238000000194 supercritical-fluid extraction Methods 0.000 description 3
- 231100000331 toxic Toxicity 0.000 description 3
- 230000002588 toxic effect Effects 0.000 description 3
- 239000004135 Bone phosphate Substances 0.000 description 2
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- KUYLHALFMPOMKK-UHFFFAOYSA-N hydroxy-sulfanylidene-bis(2,4,4-trimethylpentyl)-$l^{5}-phosphane Chemical compound CC(C)(C)CC(C)CP(O)(=S)CC(C)CC(C)(C)C KUYLHALFMPOMKK-UHFFFAOYSA-N 0.000 description 2
- UMKARVFXJJITLN-UHFFFAOYSA-N lead;phosphorous acid Chemical compound [Pb].OP(O)O UMKARVFXJJITLN-UHFFFAOYSA-N 0.000 description 2
- SJOCPYUKFOTDAN-ZSOIEALJSA-N methyl (4z)-4-hydroxyimino-6,6-dimethyl-3-methylsulfanyl-5,7-dihydro-2-benzothiophene-1-carboxylate Chemical compound C1C(C)(C)C\C(=N\O)C=2C1=C(C(=O)OC)SC=2SC SJOCPYUKFOTDAN-ZSOIEALJSA-N 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 229910021653 sulphate ion Inorganic materials 0.000 description 2
- MFEVGQHCNVXMER-UHFFFAOYSA-L 1,3,2$l^{2}-dioxaplumbetan-4-one Chemical compound [Pb+2].[O-]C([O-])=O MFEVGQHCNVXMER-UHFFFAOYSA-L 0.000 description 1
- DHGBAFGZLVRESL-UHFFFAOYSA-N 14-methylpentadecyl 16-methylheptadecanoate Chemical compound CC(C)CCCCCCCCCCCCCCC(=O)OCCCCCCCCCCCCCC(C)C DHGBAFGZLVRESL-UHFFFAOYSA-N 0.000 description 1
- 239000004808 2-ethylhexylester Substances 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- MQIUGAXCHLFZKX-UHFFFAOYSA-N Di-n-octyl phthalate Natural products CCCCCCCCOC(=O)C1=CC=CC=C1C(=O)OCCCCCCCC MQIUGAXCHLFZKX-UHFFFAOYSA-N 0.000 description 1
- 101000588145 Homo sapiens Microtubule-associated tumor suppressor 1 Proteins 0.000 description 1
- 101000588157 Homo sapiens Microtubule-associated tumor suppressor candidate 2 Proteins 0.000 description 1
- 229910000003 Lead carbonate Inorganic materials 0.000 description 1
- 102100031549 Microtubule-associated tumor suppressor candidate 2 Human genes 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- KRADHMIOFJQKEZ-UHFFFAOYSA-N Tri-2-ethylhexyl trimellitate Chemical compound CCCCC(CC)COC(=O)C1=CC=C(C(=O)OCC(CC)CCCC)C(C(=O)OCC(CC)CCCC)=C1 KRADHMIOFJQKEZ-UHFFFAOYSA-N 0.000 description 1
- 238000002835 absorbance Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- BJQHLKABXJIVAM-UHFFFAOYSA-N bis(2-ethylhexyl) phthalate Chemical compound CCCCC(CC)COC(=O)C1=CC=CC=C1C(=O)OCC(CC)CCCC BJQHLKABXJIVAM-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000000748 compression moulding Methods 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 239000000806 elastomer Substances 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 238000004442 gravimetric analysis Methods 0.000 description 1
- 239000012760 heat stabilizer Substances 0.000 description 1
- 229960001545 hydrotalcite Drugs 0.000 description 1
- 229910001701 hydrotalcite Inorganic materials 0.000 description 1
- 150000002611 lead compounds Chemical class 0.000 description 1
- OCWMFVJKFWXKNZ-UHFFFAOYSA-L lead(2+);oxygen(2-);sulfate Chemical compound [O-2].[O-2].[O-2].[Pb+2].[Pb+2].[Pb+2].[Pb+2].[O-]S([O-])(=O)=O OCWMFVJKFWXKNZ-UHFFFAOYSA-L 0.000 description 1
- YJOMWQQKPKLUBO-UHFFFAOYSA-L lead(2+);phthalate Chemical compound [Pb+2].[O-]C(=O)C1=CC=CC=C1C([O-])=O YJOMWQQKPKLUBO-UHFFFAOYSA-L 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- UEZVMMHDMIWARA-UHFFFAOYSA-M phosphonate Chemical group [O-]P(=O)=O UEZVMMHDMIWARA-UHFFFAOYSA-M 0.000 description 1
- 238000002203 pretreatment Methods 0.000 description 1
- 125000002924 primary amino group Chemical group [H]N([H])* 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000011541 reaction mixture Substances 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 238000007655 standard test method Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- ZMBHCYHQLYEYDV-UHFFFAOYSA-N trioctylphosphine oxide Chemical compound CCCCCCCCP(=O)(CCCCCCCC)CCCCCCCC ZMBHCYHQLYEYDV-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J11/00—Recovery or working-up of waste materials
- C08J11/04—Recovery or working-up of waste materials of polymers
- C08J11/06—Recovery or working-up of waste materials of polymers without chemical reactions
- C08J11/08—Recovery or working-up of waste materials of polymers without chemical reactions using selective solvents for polymer components
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D11/00—Solvent extraction
- B01D11/02—Solvent extraction of solids
- B01D11/0203—Solvent extraction of solids with a supercritical fluid
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D11/00—Solvent extraction
- B01D11/02—Solvent extraction of solids
- B01D11/0215—Solid material in other stationary receptacles
- B01D11/0223—Moving bed of solid material
- B01D11/0226—Moving bed of solid material with the general transport direction of the solids parallel to the rotation axis of the conveyor, e.g. worm
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
- B29B17/02—Separating plastics from other materials
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
- B29B17/02—Separating plastics from other materials
- B29B2017/0213—Specific separating techniques
- B29B2017/0217—Mechanical separating techniques; devices therefor
- B29B2017/0224—Screens, sieves
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
- B29B17/02—Separating plastics from other materials
- B29B2017/0213—Specific separating techniques
- B29B2017/0293—Dissolving the materials in gases or liquids
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2027/00—Use of polyvinylhalogenides or derivatives thereof as moulding material
- B29K2027/06—PVC, i.e. polyvinylchloride
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
- B29K2105/0005—Condition, form or state of moulded material or of the material to be shaped containing compounding ingredients
- B29K2105/0038—Plasticisers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
- B29K2105/0005—Condition, form or state of moulded material or of the material to be shaped containing compounding ingredients
- B29K2105/0044—Stabilisers, e.g. against oxydation, light or heat
Abstract
The invention relates to the field of recycling waste products, more in particular to a method and apparatus for the upgrading of waste PVC, including the removal of additives therefrom and the separation from other solid impurities such as metal, rubber and/or polymer particles. Provided is a method for recycling PVC, comprising contacting a feed stream comprising waste PVC with supercritical carbon dioxide (scC02), followed by subjecting the feed stream to a melt filtration process.
Description
P133390NL00
Title: Method and apparatus for recycling of polyvinylchloride (PVC).
The invention relates to the field of recycling waste products.
More in particular, it relates to a method and apparatus for the upgrading of waste PVC, including the removal of additives therefrom and the separation from other solid impurities such as metal, rubber and/or polymer particles.
Polyvinyl chloride (PVC) is a popular plastic due its long lifespan and good mechanical, electrical, chemical, thermal resistance properties.
PVC is used in building and construction, automotive, piping and cable industries including many household goods. The PVC material is strong, durable, lightweight and versatile; it makes a perfect material for many applications. More than 75% of the total PVC is used in industrial applications and especially the building and construction sector where PVC products have long life span of over 10-years.
In 2017-2018, 5.5 million tons were produced globally per year including 5.5 million tons in Europe. The worldwide volume production of
PVC is estimated to grow to approximately 60 million metric tons in 2025.
This makes PVC the third largest polymer produced worldwide, after polyethylene and polypropylene respectively. Although the production was estimated and expected to increase in 2018, the situation in 2021 is different. According to the webpage of ICIS is there a “tight availability” in the first quarter of this year (2021). This can be attributed to several causes, including a growing demand and production issues. Furthermore, a change of consumption is present from flexible “soft PVC” to “hard PVC”, which is mainly used in construction. These developments stimulate the recycling of waste PVC to high quality PVC, in order to meet the demand and reduce the carbon foot print of this fossil fuel based material.
Besides the growing demand and the enhanced, health concerns are another driving force to promote the recycling of PVC. For example, lead based heat stabilizers were added until 2015 to allow shaping and processing of PVC. However, lead is a heavy metal and is known to be highly toxic to humans and to the environment. Also, the presence of plasticizers, most often phthalates, in PVC feeds health concerns. They might migrate to the surface and leach out of the material and their toxic effects get exposed to humans and to the environment.
It has been shown in the art that phthalates can be removed from
PVC in the solid state using supercritical CO: (scCO2) as a pre-treatment step, which is followed by the subsequent removal of lead based compounds.
In solid state extraction, the PVC is present as solid granules and it takes several hours to extract any components. Finally, if the original PVC is formulated with other polymer(s), metal or rubber particles, a third step comprising the separation of such solids from the PVC has to be carried out.
However, for process intensification purposes it is highly desirable to speed up and simplify this three-step approach into a process that allows for extraction of plasticizers at the same time as other compounds and possibly the separation from solid particles. The present inventors sought to address these issues and aimed at providing an improved process to efficiently extract plasticizers and lead stabilizers from waste PVC, and to yield a safe and high quality recycled product.
This was accomplished by the surprising finding that supercritical fluid extraction (SFE) using scCO2 is advantageously performed during a melt filtration / extrusion process in a semi-continuous extraction setup.
Thus, rather than contacting (waste) PVC in the solid state with scCOZ2, it is introduced into an extruder containing a scCO2 flow which can in turn also be continuously recycled.
Despite the relatively short residence time in the extruder (less than 1 minute), this treatment unexpectedly allowed for the removal of plastizers as well as other contaminants e.g. rubber particles. Plasticizer extraction efficiencies in the range of about 80-90% can be obtained.
Additionally, the use of scCO2 allows to work at relatively low temperature, thereby avoiding HCI elimination which is an unwanted side reaction of
PVC during conventional extrusion.
Moreover, the inclusion of a chelating agent in the PVC feed stream, like an organophosphonate or an aminopolycarboxylate, allows for the simultaneous removal of toxic heavy metals such as lead based compounds.
Accordingly, the invention provides a method for recycling poly(vinylchloride) (PVC), comprising contacting a feed stream comprising waste PVC with supercritical carbon dioxide (scCO2), followed by subjecting the feed stream to a melt filtration process. Hence, the melt filtration is carried out in the presence of scCO2. The melt filtration process is ideally performed under conditions allowing for the filtration of all solid components through the filter. In particular, all materials solid under the employed experimental conditions are separated from PVC through melt filtration. In fact, the inventors observed that scCO2 has a plasticizing effect on most polymers, thus decreasing the softening temperature. This effect is different for different polymers. If the process of the invention is performed under experimental conditions where PVC flows as a melt while other polymer remain solid, the desired separation can be achieved.
Also provided is a method for removing plasticizers and/or heavy metals from a feed stream comprising waste PVC, wherein a feed stream comprising waste PVC is contacted with supercritical carbon dioxide
(scCO2), followed by subjecting the feed stream to a melt filtration, under conditions allowing for the removal of plasticizers and/or heavy metals.
The feed stream can contain from less than one percent PVC to more than ninety nine percent PVC. The feed stream may comprise up to about 30 wt%, preferably up to about 20 wt, more preferably up to about 10 wt% of polymers other than PVC. For example, the other polymers comprise one or more selected from the group of elastomer type polymer (rubber), polyethylene (PE) and polypropylene (PP).
A method of the invention is a particularly suitable for recycling and/or upgrading a feed stream comprising waste of a PVC product that was originally formulated with polyolefins and/or rubbers, such as waste insulation cable parts. A preferred plastic material contains a mixture of
PVC and rubber particles, for example up to 10wt% of ground tire rubber (GTR).
A method as provided herein is suitably used to remove heavy metals and/or plasticizers from a feed stream comprising PVC. For example, tribasic lead sulfate 1s one of the most frequently used lead stabilizer, while dibasic lead phosphite and phthalate, dibasic lead carbonate (DBLC), dibasic lead stearate (DBLS) were also commonly used. The desired lead stabilizer is chosen for each specific PVC application. For example, lead phosphite is used to increase light stability or weatherability. Combinations of different lead stabilizers are also possible to achieve the desired properties.
Generally, lead stabilizers are present in low amounts up to 6 to 12 weight percent with respect to the net amount of PVC (phr, parts per hundred resin).
Exemplary plasticizers comprise phthalate and adipate plasticizers such as dioctyl phthalate/adipate, dusooctyl phthalate/adipate and dialkyl (C7 -C9)- phthalate/adipate. 5 A person skilled in the art will be able to optimize supercritical fluid extraction (SFE) conditions, including pressure, temperature, scCO2 mass flowrate and extraction time. These may depend among others on the extraction set-up, waste stream characteristics as well as the type and amount of additives present.
Good results can be obtained if the contacting of waste PVC with scCO2 is performed under one or more of the following conditions: (a) temperature in the range of 80-180°C, preferably 80-160 °C (bb) Injection Pressure in the range of 70-200 bar, preferably 70-100 bar (Cc) Gas to polymer ratio (GTP; ratio of CO2 flow rate divided by polymer flow rate) flowrate in the range of 0.1-1.0 (d) residence time of 10 to 300 seconds, preferably 10 to 60 seconds
A method of the invention may further comprise contacting said PVC feed stream with scCO2 in the presence of a chelating agent, in particular a chelating agent that is soluble in scCO2 under the employed (temperature and pressure) conditions. In one embodiment, the chelating agent is a phosphonate or amino-containing compound which is soluble in the scCO2 phase under the employed experimental conditions. For example, it is an organophosphonate or an aminopolycarboxylate.
In a method according to the invention, the melt filtration process is typically performed using a filter unit equipped with a set of filters. In general, a person skilled in the art will appreciate and recognize that the mesh size of the filter depends on the dimensions of the solid impurities that are present and to be removed. However, the finer the filter mesh, the higher the pressure drop and the more energy is required for the melt filtration process. Thus, the choice of the optimal filter is a trade-off; it must be fine enough to remove the unwanted solids yet not too fine to control the energy costs.
It was found that very good results were obtained when using a fine iron (steel) mesh filter that supported by (sandwiched in between) two coarse iron mesh filters. For example, the fine filter preferably has a mesh size in the range of 180 to 350 um. The coarse filter preferably has a mesh size in the range of 1000 to 1300 pm, such as 1100, 1200 or 1300 pm. In a specific aspect, the filter unit comprises a filter in the range 190-300 pm supported by two filters of about 1100 um filters.
The invention also relates to a reaction mixture comprising a PVC waste stream in admixture with scCO2. Furthermore, it provides a purified or semi-purified PVC composition obtainable by a method as herein disclosed, preferably wherein said PVC composition is characterized by a Pb-content up to 5 wt% and / or a phthalate content up to 30 wt%.
A still further aspect relates to an apparatus that is specifically designed for performing a method for recycling waste PVC as taught herein. Provided is an apparatus for recycling/upgrading waste PVC, comprising an extruder provided with a melt filtration unit for receiving a plastic melt issuing from the extruder, and wherein the extruder 1s equipped with a pressure vessel containing supercritical carbon dioxide. See Figure 1 showing a schematic drawing of an exemplary PVC recycling apparatus comprising a co-rotating twin screw extruder module, operably connected to a module comprising a filtration unit and extrusion head. The heating of each module can be controlled independently with a heating system. The extruder is modified with scCO2 vessel supplying scCO2 into the extruder. Also indicated is a feed hopper for the direct feeding of a PVC feed stream into the modified extruder.
Co-rotating twin screw extruder comprise with two symmetrical screws driven by motor either directly or indirectly in the barrel casing. The two screws can rotate synchronously in the same direction, either clockwise or counterclockwise. The screw surface set with alternating screw flight. This kind of co-rotating twin-screw have been widely used in the food industry and in feed manufacturing.
As described herein above, the melt filtration unit preferably comprises a fine metal (iron; stainless steel) wire mesh supported on each side by (sandwiched in between) two coarse metal wire mesh filters, preferably a 190-300 um filter supported by about 1100 um filters. See Figure 2.
Good results are obtained with an apparatus comprising a twin-screw extruder with a screw length-to-diameter ratio (L/D) in the range of 25-35, preferably about 30.
The invention also relates to the use of the apparatus in a PVC recycling/upgrading method as herein disclosed.
LEGEND TO THE FIGURES
Figure 1: Schematic set-up of an exemplary extruder provided with a CO2 supply and a filtration unit.
Figure 2: close-up of a representative filtration unit showing a fine mesh filter sandwiched between two coarse supporting filters and stainless steel rings.
Figure 3: dimensions of the specimens used in the tensile tests.
Figure 4: representative FTIR (Fourier Transform Infrared) analysis of PVC formulated with about 30wt% of di-octylphtalate. The grey curve shows the typical string absorption of the plasticizers at about 1730 cm-1. After melt extrusion in the presence of scCO2 (black curve), the peak at 1730 cm-1 (see arrow) clearly decreases in intensity with respect to others typical of PVC, e.g. at 1430 cm-1.
EXPERIMENTAL SECTION
Materials
Waste PVC was delivered by nearby companies and originated from different sources, including wire insulation cable (TRH Recycling B.V,
Emmen) and waste LP vinyl records (Deepgrooves, Leeuwarden).
Organophosphonates trioctylphosphine oxide 99% (TOPO), bis(2,4,4- trimethylpentyl) monothiophosphinic acid 85% (Cyanex 302) and
Ethylenediaminetetraacetic acid (EDTA) were purchased from Sigma
Aldrich and used as delivered. PVC producer Shin-Etsu supplied two PVC formulations with known concentrations of lead compounds and plasticizer.
The formulations are given below.
Table 1: Hard PVC formulation K67.
LV
PVC K67 © 97.09
Heat Tri-basic lead 1.94 stabilizer sulphate
Co- Hydrotalcite 0.49
Stabilizer
Lubricant Honeywell AC 316 0.49
Table 2: Soft PVC formulation K70
PVC K70 55.87
Heat Tri-basic lead 5.04 stabilizer sulphate
Plasticizer TOTM (stab Ir 1010) 28.01
Filler Omya EXH-1 11.20
ScCO2 Extraction
Supercritical fluid extraction (SFE) experiments were conducted in an
ExtrateX extraction setup containing a CO: flow which is continuously recycled. This experimental scale setup was equipped with a 100 mL extraction vessel and a 300 mL separation vessel. The pressure, temperature, scCO2 mass flowrate and extraction time could be set to the desired level in a wide range, e.g. up to 700 bar, 150 °C and 100 gram/min scCO2. The temperature inside the separation vessel could be set to the desired value in a small range (approximately 30 to 70 °C), while the pressure was fixed and similar to the pressure in the CO2 vessel.
Organophosphorus chelating agent was added together with the waste PVC in the extraction vessel and collected in the separation vessel. Either a solely dynamic extractions or a static extraction followed by dynamic extractions were performed. In case of static extraction, the inlet and outlet of the reactor are closed as soon as the desired pressure is reached. In dynamic extraction, all lines are open and CO2 is continuously circulated.
The extraction period was started as soon as pressure and mass flow were stabilized (in case of dynamic extraction), while temperature was increased during the first 5 to 10 minutes of the experiment to reach the set level. The extraction vessel was filled up to about 90 Vol.% and contained initially about 45 gram waste PVC particles of a few millimeters in size.
Relatively large amounts of waste PVC were used to minimize deviations between the samples and to increase the accuracy of extraction and recovery efficiencies. The PVC residues were mixed in a Brabender high shear mixer at 150 to 160 °C for 5 minutes at 50 rpm. The extract and the mixed PVC residues were analyzed by XRF to estimate the Pb content.
Melt Filtration
In order to successfully separate PVC from any solid particles present, a melt filtration unit was added to an Three-Tec ZE 12 twin-screw extruder with a screw length-to-diameter ration (L/D) of 30. See Figure 1 for a schematic drawing of the equipment used.
The extruder was equipped with a scCO: supply. The extruder contains five independently controlled heating zones, a feed hopper and a pressure indicator. A tube with a screwable head comprising a set of selected iron meshes served as a filtration unit. This filtration head was heated using a temperature adjustable heat gun.
Figure 2 shows a close-up of the filtration unit. Typically, three different iron mesh filters are used: 1100 pm, 300 um and 190 um. Two supporting filters with a large size opening (1100 pm) were used to “sandwich” one finer filter (e.g. 300 or 190 um).
By using this modified extruder, above a series of experiments was carried out on a PVC feed containing 4 wt % of GTR (ground tire rubber). The experimental conditions were as follows:
Temperature: 150°C scCO2 flow: 60 g/hr
Screw speed: 50 rpm
Under these conditions and employing an extrusion time of about 30 minutes, the rubber was efficiently separated from the PVC. The rubber content in the extrudate was 1.1 wt % as opposed to the initial 4 wt %.
Tensile Test
The maximum stress (yield stress) and elongation at break of several PVC feeds were determined by using a tensile test. The machine used was a
Tinius Olsen H25KT, operated by Horizon software. For each tensile test, maximally 8 specimens were produced by compression molding, and each specimen was tested. The dimensions of these specimens are illustrated in
Figure 3.
All tensile tests were carried out with a pulling speed of 50 mm/min and at room temperature. Note, the dimensions of the specimens are not in accordance with ASTM D638 standards for Standard Test Method for Tensile Properties of Plastics.
Extraction efficiency
The results of the phthalate extraction experiments are mainly shown as the efficiency of the process, based on gravimetric analysis. The extraction and recovery efficiencies are determined as follows:
Mass solid residue in extraction vessel
E, extraction [%] — mm * 100%
Total initial mass waste PVC
Mass collected from separation vessel
E, recovery [%] ree % 100%
Total initial mass waste PVC
Figure 4 shows a representative FTIR (Fourier Transform Infrared) analysis. A PVC formulated with about 30wt% of di-octylphtalate plasticizer (grey curve) shows the typical string absorption of the plasticizers at about 1730 em-1. After extrusion (black curve), the peak at 1730 cm-1 clearly decreases in intensity with respect to others typical of PVC, for example the one at 1430 cm-1. Based on the peak absorbance, the extraction efficiency (i.e. the fraction of plasticizer extracted) was estimated to be around 80-90%.
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| US20090056742A1 (en) * | 2006-02-24 | 2009-03-05 | Bruno Fournel | Process for Decontaminating an Organic Solid Substrate Contaminated by Solid Radioactive Particulate Inorganic Contaminants, Using Dense Pressurized CO2 |
| JP4685728B2 (en) * | 2005-08-31 | 2011-05-18 | 日機装株式会社 | Raw material recovery method for lead-containing soft polyvinyl chloride material |
| ES2796956A1 (en) * | 2019-05-29 | 2020-11-30 | Asociacion De Investigacion De Mat Plasticos Y Conexas | PROCESS FOR THE REMOVAL OF PAINT FROM THERMOPLASTIC MATERIALS (Machine-translation by Google Translate, not legally binding) |
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| US5739270A (en) * | 1995-08-01 | 1998-04-14 | Farmer; Peter H. | Method and apparatus for separating polymer from a plastic, and the resulting separated polymer |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP4685728B2 (en) * | 2005-08-31 | 2011-05-18 | 日機装株式会社 | Raw material recovery method for lead-containing soft polyvinyl chloride material |
| US20090056742A1 (en) * | 2006-02-24 | 2009-03-05 | Bruno Fournel | Process for Decontaminating an Organic Solid Substrate Contaminated by Solid Radioactive Particulate Inorganic Contaminants, Using Dense Pressurized CO2 |
| ES2796956A1 (en) * | 2019-05-29 | 2020-11-30 | Asociacion De Investigacion De Mat Plasticos Y Conexas | PROCESS FOR THE REMOVAL OF PAINT FROM THERMOPLASTIC MATERIALS (Machine-translation by Google Translate, not legally binding) |
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| WAI C M ET AL: "Supercritical fluid extraction: metals as complexes", JOURNAL OF CHROMATOGRAPHY A, ELSEVIER, AMSTERDAM, NL, vol. 785, no. 1-2, 17 October 1997 (1997-10-17), pages 369 - 383, XP004097580, ISSN: 0021-9673, DOI: 10.1016/S0021-9673(97)00679-1 * |
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