Sulfoxide 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, at least one sulfoxide of formula R-(S=O)-R', wherein R and R', which may be the same or different, are selected from the group consisting of CH3, C2H5 and C3H7, and optionally a base in a vessel to obtain a mixture; (b) heating the mixture obtained in (a) at a temperature ranging from 60°C to 180°C.

Description

Sulfoxide mediated dehydrochlorination of PVDCCross-reference to related application

[0001] This application claims priority to European application No. 24169442.1 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, at least one sulfoxide of formula R-(S=O)-R’, wherein R and R’, which may be the same or different, are selected from the group consisting of CH3, C2H5 and C3H7, and optionally a base in a vessel to obtain a mixture;(b) heating the mixture obtained in (a) at a temperature ranging from 60°C to 180°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 layer 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 contains 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] Besides, high rate and high yield of dehydrochlorination have to be obtained, before conducting pyrolysis or cracking.

[0018] Dehydrochlorination reaction of vic-hydrochlorinated polymers such as polyvinyl chloride (PVC) polymers and polyvinylidene chloride (PVDC) polymers results in different products.

[0019] Indeed, dehydrochlorination of PVC polymers is produced according to the following scheme 1 :scheme 1One mole of HCI is removed by mole of repeat units therefore giving a polyene sequence, when dehydrochlorination is complete.

[0020] 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 the poly-ene sequence of scheme 2, where the removal of a second HCI by repeat unit is not observed.

[0021] 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.

[0022] It is cost saving to conduct efficient dehydrochlorination at low temperature.

[0023] Therefore, in order to manage HCI release and to operate under smoother conditions a base is generally used during dehydrochlorination.

[0024] 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.

[0025] 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.

[0026] 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 medium during 3 hours at 80°C. The resulting product is poly(vinyl alcohol).

[0027] 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.

[0028] According to the above, there is a need for a process suitable for complete or substantially complete dehydrochlorination of PVDC contained in plastic material.

[0029] There is a need for a process suitable for complete or substantially complete dehydrochlorination of PVDC contained in plastic material performed at moderate temperatures.

[0030] There is a need for a process suitable for complete or substantially complete dehydrochlorination of PVDC contained in plastic material involving non-toxic solvents or reactants.Summary of the invention

[0031] 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.

[0032] 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, at least one sulfoxide of formula R-(S=O)-R’, wherein R and R’, which may be the same or different, are selected from the group consisting of CH3, C2H5 and C3H7, and optionally a base in a vessel to obtain a mixture; b) heating the mixture obtained in a) at a temperature ranging from 60°C to 180°C.

[0033] Without being bound to any theory, the sulfoxide of formula R-(S=O)-R’ is considered as catalyst for the thermal dehydrochlorination of PVDC in the process according to the invention.

[0034] Thus, in the presence of sulfoxide of formula R-(S=O)-R’, 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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 flow of materials to be recycled.

[0039] 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.

[0040] 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

[0041] The inventors have experienced that thermally induced dehydrochlorination of PVDC polymer present in a plastic material requires high temperature and long reaction times.

[0042] The inventors have experienced that thermally induced dehydrochlorination of PVDC polymer present in a plastic material at high temperature without any catalyst is incomplete.

[0043] For example, the inventors have experienced that, although thermally induced dehydrochlorination of PVDC polymer present in a plastic material is performed at temperature as high as 265°C, the reaction is incomplete.

[0044] The inventors have found that thermally induced dehydrochlorination of PVDC polymer present in a plastic material in the presence of DMSO can be accomplished at low temperature, in high yield and within a short reaction time.

[0045] The inventors have also found that thermally induced dehydrochlorination of PVDC polymer present in a plastic material in the presence of DMSO and a base can be accomplished at even lower temperature, still in high yield and within a short reaction time.

[0046] 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, at least one sulfoxide of formula R-(S=O)-R’, wherein R and R’, which may be the same or different, are selected from the group consisting of CH3, C2H5 and C3H7, and optionally a base in a vessel to obtain a mixture; b) heating the mixture obtained in a) at a temperature ranging from 60°C to 180°C.

[0047] The plastic material can be any polymer mixture comprising PVDC polymer.

[0048] 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.

[0049] In addition to PVDC polymer, the plastic material can comprise any polymer without limitation.

[0050] 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).

[0051] 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).

[0052] 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 %.

[0053] In some embodiments the plastic material is composed or essentially composed of PVDC polymer. By essentially composed is meant that the plastic material comprises at least 90 wt % of PVDC polymer, sometimes at least 95 wt % and often at least 98 wt % of PVDC polymer.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] The at least one sulfoxide of formula R-(S=O)-R’, wherein R and R’, which may be the same or different, are selected from the group consisting of CH3, C2H5 and C3H7. In some preferred embodiments, R = R’ = CH3 i.e. sulfoxide is dimethyl sulfoxide (DMSO). DMSO can be anhydrous or non-anhydrous DMSO. Non-anhydrous DMSO is preferred.

[0059] The process according to the invention comprises the step a) of providing a plastic material, at least one sulfoxide of formula R-(S=O)-R’ and optionally a base in a vessel to obtain a mixture.

[0060] The vessel used in the present invention is not limited and is generally a reactor equipped with stirring and heating devices.

[0061] 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 range required.

[0062] 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, 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 thecorrosion of the reaction medium. 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.

[0063] In the laboratory at small scale the process can be conducted in glass vessel.

[0064] Step a) is generally performed at room temperature and atmospheric pressure, under stirring and optionally under inert atmosphere of N2 or argon.

[0065] Plastic material and sulfoxide of formula R-(S=O)-R’ can be added in the vessel simultaneously or successively. Typically, plastic material is introduced first and then sulfoxide but the reverse is possible.

[0066] When a base is used it can be added in the vessel simultaneously with the plastic material and sulfoxide or successively. The order of addition has no major effect on the result. Typically, the plastic material is introduced first, then sulfoxide and finally the base.

[0067] Generally, PVDC represents from 0.1 wt % to 25 wt % of the total weight of PVDC and sulfoxide of formula R-(S=O)-R’. Preferably, PVDC represents from 0.5 wt % to 15 wt % of the total weight of PVDC and sulfoxide. Good results were obtained with PVDC representing 1 wt % of the total weight of PVDC and sulfoxide.

[0068] The base can be inorganic and, generally selected from the list consisting of NaOH, KOH, NH4OH, LiOH, Ca(OH)2, Ba(OH)2, CaCO3, Na2CO3, NaHCO3and mixtures thereof. Preferably, the base is selected from NaOH, KOH and NH4OH. Good results were obtained with KOH.

[0069] The base can be organic and, generally selected from the list consisting of is selected from the list consisting of 1 ,8-Diazabicyclo(5.4.0)undec-7-ene (DBU), 1 ,5-Diazabicyclo(4.3.0)non-5-ene (DBN), ethylenediamine (EDA), diethylenediamine (DEDA), triethylenediamine (TEDA) and mixtures thereof.

[0070] When a base is used, the molar ratio of base to -(CH2CCI2)- repeat unit present in PVDC polymer generally ranges from 0.1 to 5; preferably from 0.25 to 3; good results were obtained with a molar ratio of base to -(CH2CCI2)- repeat unitof 0.5. For the sake of clarity, in order to determine this ratio, the molecular weight of -(CH2CCI2)- repeat unit which is considered is equal to 97 g / mol.

[0071] In the step b) of the process according to the invention, the mixture obtained in a) is generally heated at a temperature ranging from 60°C to 180°C.

[0072] In some embodiments, the mixture obtained in a) is heated at a temperature ranging from 80°C to 160°C; preferably at a temperature ranging from 100°C to 140°C.

[0073] In the presence of a base, step b) can be conducted at a lower temperature. Without being bond to any theory, it seems that the base plays the role of cocatalyst in the dehydrochlorination of plastic material comprising PVDC polymer catalysed by sulfoxide of formula R-(S=O)-R’.

[0074] When a base is present, in the step b) of the process according to the invention, the mixture obtained in a) is preferably heated at a temperature ranging from 80°C to 160°C; preferably at a temperature ranging from 100°C to 140°C; more preferably at a temperature ranging from 100°C to 120°C.

[0075] 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. Good results were obtained at a pressure of 1 bar.

[0076] 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 3 hours; preferably ranging from 10 minutes to 2 hours; more preferably ranging from 15 minutes to 1 hour.

[0077] 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.

[0078] 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 sulfoxide offormula R-(S=O)-R’ by filtration, washed with water and dried. For the sake of 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.

[0079] 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.

[0080] 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 %.

[0081] 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 %.

[0082] 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.

[0083] 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.

[0084] The process according to the invention can be performed by batches or continuously.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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

[0089] Raw materials

[0090] Plastic material named W-PVDC (W for waste) was provided internally and consists of post-industrial waste of composite film for plastic packaging containing 17 wt. % of PVDC.

[0091] DMSO was provided from Sigma-Aldrich and used without further purification.

[0092] KOH was provided from Sigma-Aldrich and used without further purification.

[0093] Comparative example 1

[0094] Thermally induced dehydrochlorination of W-PVDC was performed in a round- bottomed glass reactor.

[0095] 1 ,00 g of W-PVDC (17% w / w) were placed in a round-bottomed glass reactor. The reactor was equipped with a heating mantle, 2 thermocouples, 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 to the desired temperature, respectively 256 °C, for 60 minutes and the pressureprofile measured. After 60 minutes the reactor was cooled to room temperature and opened. The content was recovered, placed on a Buchner funnel and washed extensively with distilled water. Finally the dehydrochlorinated product was dried in an oven at 80°C under reduced pressure until constant weight was obtained.

[0096] 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 .

[0097] Examples 1 and 21 ,00 g of W-PVDC (17% w / w) were placed in a round bottomed flask equipped with a reflux condenser, an internal thermocouple attached to a Nanodac™ digital programmable reader and a magnetic stir bar. Then 15 mL of non- anhydrous DMSO were added. Stirring was started (500 rpm) and the mixture was heated to the desired reaction temperature for 60 minutes. The mixture was then cooled to room temperature, poured in a stainless steel pressure filter equipped with a porous 5 pm PTFE filtering membrane and washed with 100 mL of distilled water. The washed product was dried in an oven at 80°C under reduced pressure until constant weight was obtained. Mol % of removed HCI by dehydrochlorination was determined by semi-quantitative X-ray fluorescence elemental analysis. Results are reported in table 1 .

[0098] Examples 3 to 81 ,00 g of W-PVDC (17% w / w) were placed in a round bottomed flask equipped with a reflux condenser, an internal thermocouple attached to a Nanodac™ digital programmable reader and a magnetic stir bar. Then 8,0 mL of non- anhydrous DMSO were added followed by the addition of 0,289 g of solid KOH (i.e. 1.47 equivalent vs stoichiometric amount needed to neutralize 2 HCI generated per -(CH2CCI2)-; or 2.94 equivalent per -(CH2CCI2)-). Stirring was started (500 rpm) and the mixture was heated to the desired reaction temperature for 60 minutes. The mixture was then cooled to room temperature, poured in a stainless steel pressure filter equipped with a porous 5 pm PTFEfiltering membrane and washed with 36 mL of distilled water in 3 distinct portions of 12 mL. The washed product was dried in an oven at 80°C under reduced pressure until constant weight was obtained. Mol % of removed HCI by dehydrochlorination was determined by semi-quantitative X-ray fluorescence elemental analysis. Results are reported in table 2.

[0099] Table 1 : Thermal dehydrochlorination of W-PVDC without or with DMSO

[0100] Results reported in table 1 show that surprisingly a sulfoxide, namely DMSO, acts as a catalyst in the dehydrochlorination of W-PVDC triggered by temperature. Indeed, the presence of DMSO ensures removal of 94 mol % of HCI from W-PVDC at 140°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.

[0101] Table 2: Thermal dehydrochlorination of W-PVDC with DMSO / KOH

[0102] Results reported in table 2 show that KOH associated to a sulfoxide, namely DMSO, acts as a co-catalyst in the dehydrochlorination of W-PVDC triggered by temperature. Indeed, the simultaneous presence of KOH and DMSOensures removal of 90.3 mol % of HCI from W-PVDC at 120°C in one hour (see example 8 in table 2), while in the presence of DMSO only, a similar removal of 94 mol % is obtained but at a temperature of 140°C (see example 1 in table 1 ).

[0103] In addition, results reported in table 2 show that the simultaneous presence of KOH and DMSO allows removal of 65.9 mol % to 80.1 mol % of HCI, depending on KOH content, from W-PVDC at 100°C only in one hour (see examples 5 and 6 in table 2), while a removal of 65 mol % is obtained for dehydrochlorination of W-PVDC alone at a temperature of 256°C (see comparative example 1 in table 1 ).

[0104] According to the results presented above, the Applicant has shown that thermally induced dehydrochlorination of W-PVDC is catalysed by a sulfoxide such as DMSO, and co-catalyzed by further addition of a base.

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, at least one sulfoxide of formula R-(S=O)-R’, wherein R and R’, which may be the same or different, are selected from the group consisting of CH3, C2H5 and C3H7, and optionally a base, selected from the list consisting of NaOH, KOH, NH4OH, LiOH, Ca(OH)2, Ba(OH)2, CaCO3, Na2CO3, NaHCOs and mixtures thereof or selected from the list consisting of 1 ,8- Diazabicyclo(5.4.0)undec-7-ene (DBU), 1 ,5-Diazabicyclo(4.3.0)non-5-ene (DBN), ethylenediamine (EDA), diethylenediamine (DEDA), triethylenediamine (TEDA) and mixtures thereof, in a vessel to obtain a mixture; b) heating the mixture obtained in a) at a temperature ranging from 60°C to 180°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 any one of the previous claims, wherein the molar ratio of base to -(CH2CCI2)- repeat units present in PVDC polymer ranges from 0.1 to 5.Claim 5. The process according to any one of the previous claims, wherein at least 85 mol % of -(CH2CCI2)- repeat units present in PVDC polymer are converted into -(C=C)- repeat units.Claim 6. 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 7. The process according to any one of the previous claims, wherein the plastic material comes from a flow of materials to be recycled.Claim 8. The process according to claim 7, 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 9. The process according to any one of the previous claims, wherein R = R’ = CH3 and the sulfoxide is dimethyl sulfoxide (DMSO)Claim 10. Dehydrochlorinated PVDC polymer obtained by the process according to any one of claims 1 to 6, 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.

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