Coal fly ash mediated dehydrochlorination of pvdc

Abstract

The present invention relates to a process for the dehydrochlorination of PVDC polymer present in a plastic material, wherein the plastic material comprises at least 5 wt % of PVDC polymer, comprising the steps of: (a) providing the plastic material, coal fly ash, water and optionally a solvent (S) liquid at 50°C, miscible with water and having a boiling point at atmospheric pressure of at least 150°C, in a vessel to obtain a mixture; (b) heating the mixture (M) obtained in (a) at a temperature ranging from 180°C to 260°C.

Description

SSPI 2024 / 010Coal Fly Ash mediated dehydrochlorination of PVDCCross-reference to related application

[0001] This application claims priority to European application No. 24169440.5 filed on April 10, 2024, the whole content of this application being incorporated herein by reference for all purposes.Technical field

[0002] The present invention relates to a process for the dehydrochlorination of PVDC polymer present in a plastic material, wherein the plastic material comprises at least 5 wt % of PVDC polymer, comprising the steps of: a) providing the plastic material, coal fly ash (CFA), water and optionally a solvent (S) liquid at 50°C, miscible with water and having a boiling point at atmospheric pressure of at least 150°C in a vessel to obtain a mixture; b) heating the mixture (M) obtained in a) at a temperature ranging from 180°C to 260°C.Background

[0003] Copolymers based on vinylidene chloride typically comprising vinyl chloride, alkyl acrylates, ethylene, acrylonitrile or mixtures thereof are often used as a coating onto plastic films in order to ensure to the later excellent barrier properties either against oxygen or against water vapor.

[0004] Such coated plastic films are used mainly in food or pharmaceutical packaging applications and more particularly to form blister packs for drugs.

[0005] In such applications, plastic films are generally made of polyvinyl chloride (PVC). Indeed, these rigid film with a thickness of e.g. 250 pm can be easily thermoformed to prepare the plastic part of the package.

[0006] Beforehand, plastics films are typically coated by polyvinylidene chloride (PVDC) copolymers latexes and the resulting coated substrate is further dried to obtain the film having the desired barrier properties.

[0007] For example, thermoformable duplex PVC / PVDC films for blisters made of PVC coated with PVDC, where PVDC gives the barrier effect, are available on the market.

[0008] Generally, in order to enhance the adhesion of the PVDC coating to the PVC substrate, PVC films are first coated with an anchor agent or primer that can be selected from polyacrylic acid resins, polyurethane resins, isocyanate resins, polyesters resins, oxazoline resins and carbodiimide resins. Therefore, PVC / PVDC coated films can be considered as multilayer films.

[0009] Another example of film for blister pack available on the market is thermoformable triplex PVC / PE / PVDC film, where PVDC gives the barrier effect.

[0010] Other plastic films such as polyethylene terephthalate (PET) films, or biaxially oriented polypropylene (BOPP) films can be coated by polyvinylidene chloride (PVDC) copolymers latexes and further dried to obtain the film having the desired barrier properties.

[0011] PVDC can also be extruded to films for packaging applications and even coextruded to produce thick multilayers structures. For example a five layer coextruded film can be produced having two PE (polyethylene) skin layers, or two PP (polypropylene) skin layers, and a centred PVDC layer bonded to the skin layers with tie layers generally consisting of ethylene vinyl acetate (EVA) copolymer.

[0012] The above mentioned multilayer films generally comprise up to 30 wt % of PVDC.

[0013] The recycling of blister package wastes or of coextruded multilayer wastes is complex due to the layered structure of plastic parts. Indeed, delamination between e.g. PVC films and coated layers such as PVDC layer is a difficult process and, generally, the entirety of the plastic part of the blister has to be recycled as a single material.

[0014] Moreover, the recycling of plastic material wastes that contain polymers bearing chlorine atoms, such as PVDC polymers, is usually considered aschallenging because of the presence of chlorine atoms and possible HCI release.

[0015] It is the case when plastic material wastes, end-of-life or post-industrial, are recycled to fuel or to new raw materials e.g. via pyrolysis or cracking processes.

[0016] Therefore, beforehand dehydrochlorination of polymers bearing chlorine atoms, more particularly PVDC polymers, contained in plastic material wastes is an option to reduce drastically the chlorine content before engaging those material e.g. in pyrolysis or cracking processes.

[0017] Dehydrochlorination reaction of vic-hydrochlorinated polymers such as polyvinyl chloride (PVC) polymers and polyvinylidene chloride (PVDC) polymers results in different products.

[0018] Indeed, dehydrochlorination of PVC polymers is produced according to the following scheme 1 :One mole of HCI is removed by mole of repeat units therefore giving a polyene sequence, when dehydrochlorination is complete.

[0019] While dehydrochlorination of PVDC polymers is produced according to the following scheme 2 and scheme 3:sc eme 3Two moles of HCI are removed by mole of repeat units therefore giving a polyyne sequence, when dehydrochlorination is complete. Partial dehydrochlorination of PVDC may result, for example, in a polymer having thepoly-ene sequence of scheme 2, where the removal of a second HCI by repeat unit is not observed.

[0020] Dehydrochlorination reaction of polyvinyl chloride (PVC) polymers and of polyvinylidene chloride (PVDC) polymers can be induced thermally. However, it generally requires high temperature and long reaction times to be completed.

[0021] It is cost saving to conduct efficient dehydrochlorination at low temperature.

[0022] Therefore, in order to manage HCI release and to operate under smoother conditions a base is generally used during dehydrochlorination.

[0023] J. Macromol. Sci.-Chem., A12(2), 249-260 (1978) relates to the kinetics of the alkaline dehydrochlorination of polyvinylchloride (PVC) in the presence of alcoholic KOH in THF solution at 9.5°C. Small amounts of DMSO in the solvent are found to increase the reaction rate. Material with poly-ene sequences is obtained. Conclusion is made that DMSO has a catalytic effect on the alkaline dehydrochlorination reaction of PVC. However, nothing is said about PVDC dehydrochlorination. Finally, dehydrochlorination reaction of PVC requires the presence of a solvent such as THF.

[0024] Makromol. Chem. 186, 1395 (1985) discloses the interface reaction of a THF solution of a VDC copolymer with an aqueous alkaline solution at room temperature in the presence of a quaternary ammonium halide as phase transfer catalyst which affords a dehydrochlorinated polymer film with conjugated poly-ene structure. Only partial removal of a second HCI from the repetitive unit was observed.

[0025] Polymer Degradation and Stability 86 (2004), 541-547, discloses the alkaline dehydrochlorination of PVC in organic solvents. More particularly, dechlorination of 98-99 % is obtained in DMSO, in the presence of water, using NaOH as the base through heating the reaction solvent during 3 hours at 80°C. The resulting product is poly(vinyl alcohol).

[0026] Procedia Engineering 152 (2016) 747-752, deals with dehydrochlorination of mechanically activated polyvinylchloride (PVC) in DMSO suspension at 20°C for 6 hours using potassium hydroxide. Resulting polyvinylene further treated at 400°C for 2 hours contains only 0.6 % by weight of chlorine.

[0027] Journal of Cleaner Production 260 (2020) 121085, relates to the dechlorination of PVC in low-temperature subcritical water enhanced by coal fly ash (CFA) and coal gangue. Although the process requires temperature below 250°C, it also requires high pressures to maintain water in its liquid state. With CFA, the process allows achieving 94.5 % of PVC dechlorination efficiency at 220°C to give polyene. However, nothing is said about PVDC dehydrochlorination.

[0028] International Journal of Polymer Analysis and Characterization 23 (2), 218, 170-180 relates to the thermal decomposition via dehydrochlorination of PVC / coal fly Ash (CFA) composites. Again, nothing is said about PVDC dehydrochlorination.

[0029] According to the above, there is a need for a process suitable for complete or substantially complete dehydrochlorination of PVDC contained in plastic material.

[0030] There is a need for a process suitable for complete or substantially complete dehydrochlorination of PVDC contained in plastic material performed at moderate temperatures.

[0031] There is a need for a process suitable for complete or substantially complete dehydrochlorination of PVDC contained in plastic material involving recycled reactants or catalysts.Summary of the invention

[0032] With the aim of fulfilling the above needs, the Applicant faced the problem of providing a new process suitable for complete or substantially complete dehydrochlorination of PVDC contained in plastic material.

[0033] Thus, in a first aspect, the present application relates to a process for the dehydrochlorination of PVDC polymer present in a plastic material, wherein the plastic material comprises at least 5 wt % of PVDC polymer, comprising the steps of: a) providing the plastic material, coal fly ash (CFA), water and optionally a solvent (S) liquid at 50°C, miscible with water and having a boiling point at atmospheric pressure of at least 150°C in a vessel to obtain a mixture;b) heating the mixture (M) obtained in a) at a temperature ranging from 180°C to 260°C.

[0034] Without being bound to any theory, CFA is considered as catalyst for the thermal dehydrochlorination of PVDC in the process according to the invention.

[0035] Coal fly ash (CFA), which is an industrial by-product of coal industry, can be advantageously valorized in the present invention.

[0036] Thus, in the presence of CFA, it is possible to perform complete or substantially complete dehydrochlorination of PVDC at relatively low temperature and high reaction rate according to scheme 2 and scheme 3.

[0037] This is advantageous because the process according to the invention allows performing the second step of dehydrochlorination of PVDC polymer as illustrated on scheme 3 above in high yield and in relatively mild operating conditions.

[0038] It is also advantageous because the process according to the invention allows preparing in high yield poly-yne conjugated polymers that can be used e.g. as electro conductive material owing to conjugated unsaturations along the backbone.

[0039] In another aspect the present invention relates to a dehydrochlorinated PVDC polymer, wherein at least 85 mol % , preferably at least 90 mol %, more preferably at least 94 mol %, and even more preferably at least 99 mol % of - (CH2CCI2)- repeat units present in PVDC polymer are converted into -(C=C)- repeat units.

[0040] Still in another aspect, the present application relates to a process for the dehydrochlorination of PVDC polymer present in a plastic material, wherein the plastic material comes from a flow of materials to be recycle.

[0041] This is advantageous because the process according to the invention can be used for recycling any plastic wastes i.e. end-of-life or post-industrial wastes containing PVDC polymer.

[0042] It is also advantageous because the process according to the invention can be easily implemented by a person of ordinary skill in the art without requiring very demanding conditions.Detailed description

[0043] The inventors have experienced that thermally induced dehydrochlorination of PVDC polymer present in a plastic material requires high temperatures and long reaction times.

[0044] The inventors have experienced that thermally induced dehydrochlorination of PVDC polymer present in a plastic material at high temperature may require high pressure.

[0045] The inventors have experienced that, although thermally induced dehydrochlorination of PVDC polymer present in a plastic material is performed at temperature as high as 256°C and optionally high pressure, the reaction is incomplete.

[0046] The inventors have found that thermally induced dehydrochlorination of PVDC polymer present in a plastic material in the presence of coal fly ash (CFA) can be accomplished at lower temperature, in higher yield and within a shorter reaction time.

[0047] The inventors have also found that thermally induced dehydrochlorination of PVDC polymer present in a plastic material in the presence of CFA and a solvent (S) liquid at 50°C, miscible with water and having a boiling point at atmospheric pressure of at least 150°C can be accomplished at lower pressure, still in high yield and within a short reaction time.

[0048] The present application relates to a process for the dehydrochlorination of PVDC polymer present in a plastic material, wherein the plastic material comprises at least 5 wt % of PVDC polymer, comprising the steps of: a) providing the plastic material, coal fly ash, water and optionally a solvent (S) liquid at 50°C, miscible with water and having a boiling point at atmospheric pressure of at least 150°C in a vessel to obtain a mixture; b) heating the mixture (M) obtained in a) at a temperature ranging from 180°C to 260°C.

[0049] The plastic material can be any polymer mixture comprising PVDC polymer.

[0050] The term PVDC polymer, encompasses PVDC homopolymers and copolymers based on vinylidene chloride, typically comprising vinyl chloride, acrylonitrile, acrylates, acrylic acid, ethylene or mixtures thereof as comonomers.

[0051] In addition to PVDC polymer, the plastic material can comprise any polymer without limitation.

[0052] For example, in addition to PVDC polymer, the plastic material can comprise at least one polymer selected from the list consisting of polyvinylchloride (PVC) and copolymers based on vinyl chloride, polyethylene (PE) and copolymers based on ethylene, polypropylene (PP) and copolymers based on propylene, polystyrene (PS) and copolymers based on styrene, polycarbonates, and polyesters such as polyethylene terephthalate (PET).

[0053] Often, in addition to PVDC polymer, the plastic material comprises at least one polymer selected from the list consisting of polyvinylchloride (PVC) and copolymers based on vinyl chloride, polyethylene (PE) and copolymers based on ethylene, polypropylene (PP) and copolymers based on propylene, and polyesters such as polyethylene terephthalate (PET).

[0054] Generally, the plastic material comprises at least 5 wt % of PVDC polymer. Sometimes, the plastic material comprises at least 10 wt % of PVDC polymer; often at least 15 wt %; typically at least 30 wt %.

[0055] In some embodiments the plastic material is composed or essentially composed of PVDC polymer. By essentially composed is meant that the plasticmaterial comprises at least 90 wt % of PVDC polymer, sometimes at least 95 wt % and often at least 98 wt % of PVDC polymer.

[0056] In some embodiments, the plastic material may contain some additives such as plasticizers, fillers, anchor agents, primers... When present the amount of the additives generally does not exceed 15 wt % of the total weight of the plastic material; sometimes does not exceed 10 wt %; often does not exceed 5 wt %; even more often does not exceed 2 wt % of the total weight of the plastic material.

[0057] The plastic material may have been submitted to a pre-treatment such as washing and shredding. Therefore, the plastic material may be under the form of objects resulting from shredding.

[0058] Often, the plastic material is under the form of a 3 dimensional objects having dimensions in 3 orthogonal directions, the 2 largest of these dimensions being 0.5 mm or more, the smallest third dimension being 10 mm or less.

[0059] Typically, the 2 largest dimensions range from 2 mm to 25 mm and the smallest third dimension ranges from 0.05 mm to 1 .5 mm.

[0060] Coal fly ash (CFA) is an industrial by-product of coal industry. It is the major component of coal combustion waste in thermal power plants.

[0061] Element analysis of CFA reveals the presence of SiO2 and AI2O3 as major products, as well as Fe2O3, CaO, Na2O, K2O and MgO. However, other compounds may be present in lower amounts such as C, TiO2, P2O5, MnO, SO3, S and heavy metal traces.

[0062] Any CFA can be used in the present invention, among which CFA of Class C and of Class F. It is generally admitted that Class C comprises more than 15 wt % of CaO, while Class F comprises less than 15 wt % of CaO.

[0063] Good results were obtained using Class F coal fly ash, namely NIST®SRM®- 2689.

[0064] Generally, CFA is under the form of a powder having particle size of less than 150 pm, preferably of less than 100pm, more preferably of less than 50 pm.

[0065] The process according to the invention comprises the step a) of providing a plastic material, coal fly ash, water and optionally a solvent (S) liquid at 50°C,miscible with water and having a boiling point at atmospheric pressure of at least 150°C in a vessel to obtain a mixture.

[0066] The vessel used in the present invention is not limited and is generally a reactor equipped with stirring and heating devices capable of working under pressure.

[0067] The nature of the materials composing the vessel used in the present invention is not limited. However, the steps of the process according to the invention are advantageously carried out in equipment capable of withstanding the conditions, especially due to the presence of HCI at the temperature and pressure ranges required.

[0068] For this purpose, materials are selected for the part in contact with the reaction mixture that are corrosion-resistant, such as the alloys based on molybdenum, chromium, cobalt, iron, copper, manganese, titanium, zirconium, aluminium, carbon and tungsten, sold under the Hastelloy® brands or the alloys of nickel, chromium, iron and manganese to which copper and / or molybdenum are added, sold under the name Inconel® or MonelTM, and more particularly the Hastelloy C276 or Inconel 600, 625 or 718 alloys. Use may also be made of equipment consisting of or coated with a polymeric compound resistant to the corrosion of the reaction solvent. Mention may in particular be made of materials such as PTFE (polytetrafluoroethylene or Teflon) or PFA (perfluoroalkyl resins). Further, corrosion-resistant SiC materials or even glass can be used.

[0069] In the laboratory at small scale the process can be conducted in glass vessel.

[0070] Step a) is generally performed at room temperature and atmospheric pressure, under stirring and optionally under inert atmosphere of N2 or argon.

[0071] Plastic material and CFA can be added in the vessel simultaneously or successively. Typically, plastic material is introduced first and then CFA but the reverse is possible. Then, water and optionally the solvent can be added in the vessel to obtain the mixture.

[0072] The order of addition has no major effect on the result, therefore water and optionally the solvent can be added in the vessel before the plastic material and CFA.

[0073] Typically, the plastic material is introduced first, then CFA, then water and, when present, the solvent.

[0074] Generally, CFA to PVDC weight ratio ranges from 0.1 to 10. Preferably, CFA to PVDC weight ratio ranges from 0.4 to 5. Good results were obtained with CFA to PVDC weight ratio equal to 0.47 and equal to 2.94.

[0075] Generally, water to PVDC weight ratio ranges from 5 to 200. Preferably, water to PVDC weight ratio ranges from 20 to 150. Good results were obtained with water to PVDC weight ratio equal to 58.8 and equal to 117.6.

[0076] The applicant has found that providing a solvent (S) liquid at 50°C, miscible with water and having a boiling point at atmospheric pressure of at least 150°C in the vessel in step a), allows conducting the process at lower pressure for a given temperature. Therefore, in some embodiments a solvent (S) is introduced in addition to water in step a).

[0077] Generally, the solvent (S) liquid at 50°C, miscible with water, has a boiling point at atmospheric pressure of at least 150°C; preferably of at least 180°C; more preferably of at least 200°C.

[0078] Suitable solvent (S) can be selected from the list consisting of N,N- dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylsulfoxide (DMSO), dimethylsulfone (DMSO2), sulfolane and mixtures thereof.

[0079] Good results were obtained using sulfolane.

[0080] When solvent is present in the process according to the invention, the solvent to water volume ratio ranges from 0.1 to 20; preferably from 0.5 to 10; more preferably from 1 to 5. Good results were obtained with a solvent to water volume ratio equal to 2.

[0081] In the step b) of the process according to the invention, the mixture (M) obtained in a) is generally heated at a temperature ranging from 180°C to 260°C.

[0082] In some embodiments, the mixture (M) obtained in a) is heated at a temperature ranging from 200°C to 260°C; preferably at a temperature ranging from 200°C to 240°C.

[0083] Generally, step b) of the process according to the invention is conducted at a pressure ranging from 1 bar to 50 bars; preferably ranging from 1 bar to 20 bars; more preferably ranging from 1 bar to 10 bars.

[0084] Generally, in step b) of the process according to the invention heating at the given temperature is performed during a period of time ranging from 5 minutes to 4 hours; preferably ranging from 10 minutes to 3 hours; more preferably ranging from 15 minutes to 2 hours.

[0085] The process according to the invention can further comprise a step (c) of recovering a dehydrochlorinated plastic material comprising less than 2 wt % of chlorine; preferably less than 1 wt % of chlorine; more preferably less than 0.5 wt % of chlorine. Chlorine content can be determined by semi-quantitative X-ray fluorescence elemental analysis.

[0086] The recovery of the dehydrochlorinated plastic material in step c) can be performed by any method well-known by the skilled person. For example, the dehydrochlorinated plastic material can be extracted from the water, or from water / solvent mixture when solvent is present, by filtration, washed with water and dried. For example, filtration and washing with water can be performed on a Buchner funnel and drying can be performed in an oven under vacuum until constant weight is obtained.

[0087] Dehydrochlorination can be determined by any technique well known by the skilled person for example by semi-quantitative X-ray fluorescence elemental analysis. For this purpose, quantitative Cl content in product resulting from the process is compared to Cl content in plastic material engaged in the process.

[0088] Mol % of removed HCI can be determined by semi-quantitative X-ray fluorescence as described above. Generally, in the process according to the invention at least 85 mol % of the equivalent HCI present in -(CH2CCI2)- repeat units is removed from the plastic material; preferably at least 90 mol %; more preferably at least 94 mol % and even more preferably at least 99 mol %.

[0089] Similarly, mol % of -(CH2CCI2)- repeat units converted into -(C=C)- repeat units can be determined by semi-quantitative X-ray fluorescence as described above. Generally, in the process according to the invention at least 85 mol %of the -(CH2CCI2)- repeat units are converted into -(C=C)- repeat units; preferably at least 90 mol %; more preferably at least 94 mol % and even more preferably at least 99 mol %.

[0090] Therefore, when the plastic material is composed or essentially composed of PVDC polymer, the process according to the invention allows preparing in high yield poly-yne conjugated polymers that can be used e.g. as electro conductive material owing to conjugated unsaturations along the backbone.

[0091] Thus, another aspect the present invention relates to a dehydrochlorinated PVDC polymer, wherein at least 85 mol % , preferably at least 90 mol %, more preferably at least 94 mol %, and even more preferably at least 99 mol % of - (CH2CCI2)- repeat units present in PVDC polymer are converted into -(C=C)- repeat units.

[0092] The process according to the invention can be performed by batches or continuously.

[0093] Advantageously, the process according to the invention can be performed for dehydrochlorination of plastic material which comes from a flow of materials to be recycled. Often, the flow of materials to be recycled comprises end-of-life or post-industrial pharmaceutical blister wastes, end-of-life or post-industrial food packaging wastes, end-of-life or post-industrial film wastes or mixtures thereof.

[0094] The flow of materials to be recycled may also comprise any other plastic material waste stream containing PVDC polymer such as scraps of production or post-industrial wastes.

[0095] The invention will be now described with reference to the following examples, whose purpose is merely illustrative and not intended to limit the scope of the invention.

[0096] Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.Experimental section

[0097] Raw materials

[0098] Plastic material named W-PVDC was provided internally and consists of postindustrial waste of composite film for plastic packaging containing 17 wt. % of PVDC.

[0099] CFA, NIST®SRM®-2689 was provided by Sigma-Aldrich.

[0100] Sulfolane was provided from Merk.

[0101] Comparative example 1

[0102] Thermally induced dehydrochlorination of W-PVC was performed in a stainless steel pressure reactor.

[0103] 1 ,00 g of W-PVDC (17% w / w) were placed in a stainless steel pressure reactor. The reactor was equipped with a heating mantle, 2 thermocouples, a pressure transducer all connected to a Nanodac™ digital, programmable reader and a magnetic stirring bar. The reactor was closed and cooled to -78°C (dry-ice). Then 5 cycles of N2 / vacuum were performed. The reactor was then heated and maintained to the desired temperature, respectively 256 °C, for 60 minutes and the pressure profile measured. After 60 minutes the reactor was cooled to room temperature and opened. The content was recovered, placed on a Buchner funnel equipped with a Whatman 41 filter paper and washed extensively with distilled water. Finally the dehydrochlorinated product was dried in an oven at 80°C under reduced pressure overnight.

[0104] Mol % of removed HCI by dehydrochlorination was determined by semi- quantitative X-ray fluorescence elemental analysis. For this purpose, quantitative Cl content in dehydrochlorinated product was compared to Cl content in W-PVDC engaged in the process. Results are reported in table 1 .

[0105] Example 11 ,00 g of W-PVDC (17% w / w) were placed in a stainless steel pressure reactor along with a weighed 80 mg quantity of CFA (coal fly ash) all in 10 mL of distilled H2O. The reactor was equipped with a heating mantle, 2 thermocouples, a pressure transducer all connected to a Nanodac™ digital, programmable reader and a magnetic stirring bar. The reactor was closed and cooled to -78°C (dry-ice). Then 5 cycles of N2 / vacuum were performed. The reactor was then heated and maintained to the desired temperature for 60 minand the pressure profile measured. After 60 min the reactor was cooled to room temperature and opened. The contents were first filtered on a PTFE pressure filter with a microporous 0,2 pm in order to separate CFA and the crude de-HCI polymer from H2O. The polymer was removed from the filter surface and placed on a Buchner funnel equipped with a Whatman 41 filter paper and washed extensively with distilled H2O. Finally the polymer was dried in an oven at 80°C under reduced pressure overnight. Mol % of removed HCI by dehydrochlorination was determined by semi-quantitative X-ray fluorescence elemental analysis. Results are reported in table 1 .

[0106] Example 2

[0107] 1 ,00 g of W-PVDC (17% w / w) were placed in a stainless steel pressure reactor along with 80 mg of CFA (coal fly ash) all in 10 mL of distilled H2O and 20 mL of sulfolane. The reactor was equipped with a heating mantle, 2 thermocouples, a pressure transducer all connected to a Nanodac™ digital, programmable reader and a magnetic stirring bar. The reactor was closed and cooled to -78°C (dry-ice). Then 5 cycles of N2 / vacuum were performed. The reactor was then heated and maintained to the desired temperature for 60 min and the pressure profile measured. After 60 min the reactor was cooled to room temperature and opened. The contents were first filtered on a PTFE pressure filter with a microporous 0,2 pm in order to separate CFA and the crude de-HCI polymer from H2O. The polymer was removed from the filter surface and placed on a Buchner funnel equipped with a Whatman 41 filter paper and washed extensively with distilled H2O. Finally the polymer was dried in an oven at 80°C under reduced pressure overnight. Mol % of removed HCI by dehydrochlorination was determined by semi-quantitative X-ray fluorescence elemental analysis. Results are reported in table 1 .

[0108] Table 1 : Thermal dehydrochlorination of W-PVDC without or with CFA

[0109] Results reported in table 1 show that surprisingly CFA acts as a catalyst in the dehydrochlorination of W-PVDC triggered by temperature. Indeed, the presence of CFA ensures removal of 82 mol % of HCI from W-PVDC at 220°C in one hour, while in the same duration thermal treatment at 256°C of W-PVDC alone promotes removal of 65 mol % of HCI only (compare example 1 with comparative example 1 ).

[0110] Increasing temperature allows reaching removal of 86 mol % of HCI from W- PVDC at 260°C (see example 2).

[0111] Adding sulfolane to the reaction mixture allows removal of 86 mol % of HCI from W-PVDC at 260°C with reducing the pressure in the reactor when compared to trial run with water only (compare example 2 with example 1 ).

[0112] According to the results presented above, the Applicant has shown that thermally induced dehydrochlorination of W-PVDC in the presence of water and optionally of a solvent different from water is catalysed by coal fly ash (CFA).

Claims

ClaimsClaim 1. A process for the dehydrochlorination of PVDC polymer present in a plastic material, wherein the plastic material comprises at least 5 wt % of PVDC polymer, comprising the steps of: a) providing the plastic material, water, coal fly ash and optionally a solvent (S) liquid at 50°C, miscible with water and having a boiling point at atmospheric pressure of at least 150°C, in a vessel to obtain a mixture (M); b) heating the mixture (M) obtained in a) at a temperature ranging from 200°C to 260°C.Claim 2. The process according to claim 1 , wherein step b) is conducted at a pressure ranging from 1 to 50 bars.Claim 3. The process according to claim 1 or 2, wherein step b) is conducted during a period of time ranging from 5 minutes to 3 hours.Claim 4. The process according to claims 1 to 3, wherein the solvent (S) is selected from the list consisting of N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylsulfoxide (DMSO), dimethylsulfone (DMSO2), sulfolane and mixtures thereof.Claim 5. The process according to claims 4, wherein the solvent (S) is sulfolane.Claim 6. The process according to any one of the previous claims, wherein at least85 mol % of -(CH2CCI2)- repeat units present in PVDC polymer are converted into -(C=C)- repeat units.Claim 7. The process according to any one of the previous claims further comprising a step (c) of recovering a dehydrochlorinated plastic material comprising less than 2 wt % of chlorine as determined by semi-quantitative X-ray fluorescence elemental analysis.Claim 8. The process according to any one of the previous claims, wherein the plastic material comes from a flow of materials to be recycled.Claim 9. The process according to claim 9, wherein the flow of materials to be recycled comprises end-of-life or post-industrial pharmaceutical blister wastes, end- of-life or post-industrial food packaging wastes, end-of-life or post-industrial film wastes or mixtures thereof.Claim 10. Dehydrochlorinated PVDC polymer obtained by the process according to any one of claims 1 to 7, wherein at least 85 mol % of -(CH2CCI2)- repeat units present in PVDC polymer are converted into -(C=C)- repeat units.

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