Extruded films comprising PEEK with low extractables content

Abstract

The present invention relates to use of a PEEK polymer to manufacture films by extrusion, wherein the PEEK polymer is characterised by a total amount of extractables of no more than 3000 µg / g and by an amount of Oligomer (1) of no more than 70 µg / g.

Description

DescriptionExtruded films comprising PEEK with low extractables contentReference To Related ApplicationsThis application claims priority from US provisional application Nr. 63 / 550390 filed on February 6, 2024, the whole content of which being incorporated herein by reference for all purposes.Technical Field

[0001] The present invention relates to extruded articles, such as films, comprising PEEK with low extractables content.Background Art

[0002] Polyaryletherketone polymers, including in particular poly(etheretherketone) (PEEK) polymers are well known for their exceptional balance of technical properties, such as excellent heat resistance, mechanical properties and wear resistance. They are widely used in many applications including films for speaker diaphragms, thrust washers, connectors, printed circuit boards, wrapping films for electric wires, heat-insulating bags, insulating tapes, RFID covers, battery protective films, spacer films, slot liners for electrical motors, membrane switches, and release films.

[0003] However, because of its high melting temperature (340-345°C), the processing of polyaryletherketone polymers requires a very high temperature (above 360°C). Under these high temperature conditions, in extrusion long running times, some low molecular weight compounds can be vaporized off the polymer and form a deposit on the extruder die. This deposit is usually solid and creates defects on the extruded article as the deposit gets loose. This is oftentimes referred to as “die lip build-up”. This phenomenon negatively impacts the productivity in film extrusion processes, as the deposit creates defects in the film.

[0004] The vapours released by the extruder can also be a problem in some applications requiring high purity environment. These phenomena may sometimes be referred to as “off-gassing”.

[0005] The low molecular weight compounds present in these deposits are mostly residual diphenyl sulfone solvent, residual 4,4’-difluorobenzophenone monomer and oligomers. The oligomers are difficult to remove by standard extraction processes using solvents of limited solvent power (acetone, ethanol). This makes it difficult to implement an industrially viable process for reducing the presence of the oligomers at the end of the polymerization process. Hence limiting their formation during the polymerization reaction allows for the production of polyarylethereketone polymers with limited level of low molecular weight compounds which are associated with die lip build-up and off-gassing.

[0006] These low molecular weight compounds can be quantified by Soxhlet extraction with acetone and It has now been found that it is possible to manufacture polyarylethereketone polymers, in particular PEEK polymers, having a total amount of extractables of no more than 3000 pg / g and which contain no more than 70 pg / g of Oligomer 1 as defined hereafter. The use of such polyarylethereketone polymers in the manufacture of articles by melt processing, in particular thin articles, such as films, allows for a significant reduction in low molecular weight compounds associated with die lip build-up reducing the loss of productivity during extrusion processes which are caused by this phenomenon.Summary of invention

[0007] Facing the problem of providing a PEEK polymer for the manufacture extruded films, the Applicant surprisingly found that the use of a PEEK polymer powder characterised by a total amount of extractables of no more than 3000 pg / g of polymer powder and no more than 70 pg / g of Oligomer 1 as defined hereafter allows manufacturing articles by extrusion with reduced level of die lip build-up and hence reduced risk of defects in the obtained articles.

[0008] The PEEK polymer when in the form of pellets is advantageously characterised by a total amount of extractables of no more than 3000 pg / g, preferably no more than 2000 pg / g, and an amount of Oligomer 1 of no more than 70 pg / g.

[0009] The PEEK polymer is also advantageously characterised by a crystallization temperature, Tc, measured using differential scanning calorimetry (DSC) as detailed in the examples, of at least 278°C.

[0010] Films and articles obtained from the PEEK polymer powder or pellets are also characterised by an amount of extractable of no more than 3000 pg / g, preferably no more than 2000 pg / g, and an amount of Oligomer 1 of no more than 70 pg / g.

[0011] The invention further provides for methods for the preparation of a PEEK polymer characterised by a total amount of extractables of no more than 3000 pg / g and an amount of Oligomer 1 of no more than 70 pg / g.Description of the invention

[0012] Definitions

[0010] For the purposes of the present description:- the use of parentheses before and after symbols or numbers identifying compounds, chemical formulae or parts of formulae has the mere purpose of better distinguishing those symbols or numbers from the rest of the text and hence said parentheses can also be omitted;- the expression “comprising a” should be understood as meaning “comprising at least one”. The expression “a” or “an” should be understood as meaning “at least one”;- the expression such as “Object P comprises at least the elements p1 , p2... pi” should also be understood as encompassing explicitly the embodiment wherein Object P consists essentially of the elements p1 , p2 ... pi;-“essentially” in this context means that some impurities, undesired species, unintentional compounds or the like could be present in Object P without impacting its targeted function and effect in the framework of the present invention;-the expression “comprised between ... and ...” or “ranging from... to...” and the like should be understood as including the limits;- “crystallization temperature (Tc)” or “melting temperature (Tm)” are intended to indicate the crystallization temperature or the meltingtemperature measured by differential scanning calorimetry (DSC) according to ASTM D3418 at 20°C / min cooling rate.

[0013] A first object of the present invention is the use of a PEEK polymer powder, hereinafter referred to as “PEEK Polymer Powder”, to manufacture films by extrusion, wherein the PEEK Polymer Powder is characterised by a total amount of extractables of no more than 3000 pg / g and by an amount of Oligomer 1 of no more than 70 pg / g[Oligomer 1 ], and wherein the amount of extractables and of Oligomer 1 are determined by Soxhlet extraction with acetone for 48 hours followed by liquid chromatography.

[0014] The PEEK Polymer Powder is characterised by a total amount of extractables of no more than 3000 pg / g and by an amount of Oligomer 1 of no more than 70 pg / g. The expression “pg / g” when referred to the amount of extractables and of Oligomer 1 is relative to the amount in grams of the PEEK polymer.

[0015] For the avoidance of doubts, the total amount of extractables includes Oligomer 1 .

[0016] The total amount of extractables is determined by subjecting a sample of the PEEK Polymer Powder which has been processed to have a median particle size dso in the range of 200 to 300 microns to a Soxhlet extraction process in acetone for 48 hours. At the end of the 48 hours, the extract is concentrated and dried to constant weight at room temperature under vacuum. The weight of the extract represents the total weight of extractables / g polymer.

[0017] The particle size of the PEEK Polymer Powder to be used for the determination of the amount of extractables is determined by laser scattering from a dispersion of the particles in 2-propanol. The expression “median particle size” or the notation “dso” have the usual meaning used in the field of particle size distributions. For the sake of clarity, dncorresponds to the diameter of the particles for which n% of the particleson a volume basis have a diameter which is less than dn. Hence, dso (median) is defined as the size value corresponding to the cumulative distribution at 50%, the distribution being a volume distribution.

[0018] The amount of Oligomer 1 in the extract can be determined using known chromatographic techniques. The retention times of the main components in the extract can be identified by LC-MS or by preparing actual standards. Oligomer 1 can be prepared according to Fukawa et al, Journal of Polymer Science : Part A : Polymer Chemistry, 1993, Vol. 31 , P 535-546 and used to determine the retention time under the testing conditions used for the analysis of the extract.

[0019] A detailed protocol for the determination of the total amount of extractables and of Oligomer 1 is detailed in the Experimental Section under the heading “Extractables Determination”.

[0020] The expression “PEEK Polymer” is used herein to refer to a polyaryletherether ketone polymer which comprises at least 80 mol%, preferably at least 85 mol%, preferably at least 90 mol%, more preferably at least 95 mol%, even more preferably at least 98 mol%, at least 99 mol% and even 100 mol% of recurring units of formula (RPEEK):

[0021] Preferably, when the PEEK Polymer comprises less than 100 mol% of recurring units of formula (RPEEK) as represented above, it comprises up to 1 mol%, up to 2 mol%, up to 5 mol%, up to 10 mol%, up to 15 mol% or up to 20 mol% of at least one recurring unit selected from the ones having formula (K-A) to (K-P) below:wherein each R’ is independently selected from halogen, an alkyl, an alkenyl, an alkynyl, an aryl, an ether, a thioether, a carboxylic acid, an ester, an amide, an imide, an alkali or an alkaline earth metal sulfonate, an alkyl sulfonate, an alkali or alkaline earth metal phosphonate, an alkyl phosphonate, an amine and a quaternary ammonium; and each j’ is independently 0 or an integer from 1 to 4. Typically, each j’ is 0.

[0022] Advantageously, the PEEK Polymer comprises at least 98 mol%, at least 99 mol% and even more preferably 100 mol% of recurring units of formula (RPEEK).

[0023] The PEEK Polymer is also advantageously characterised by a crystallization temperature, Tc, measured using differential scanning calorimetry (DSC), of at least 278°C. The PEEK Polymer may advantageously have a crystallization temperature, Tc, of at least 279°C, even at least 280°C, preferably at least 281 °C.

[0024] The PEEK Polymer is characterised by a number average molecular weight (Mn) and / or weight average molecular weight (Mw) in a range which allows to compromise between melt strength, ductility and low viscosity for ease of processing.

[0025] Mn and Mw are measured by gel permeation chromatography (GPC) at 160 °C in 1 ,2,4-trichlorobenzene:phenol (50:50) using polystyrene (PS) standards.

[0026] The PEEK Polymer generally has a Mn in the range from 29,000 to 58,000. The PEEK Polymer generally has a Mw in the range from 60,000 to 125,000.

[0027] The PEEK Polymer Powder may be prepared according to a process which comprises: reacting hydroquinone, 4,4’-difluorobenzophenone and optionally the other monomers, in a solvent comprising more than 80 wt% diphenyl sulfone, using alkali metal carbonate as base; and- isolating the polymer by extraction with an organic solvent using at least 50 L organic solvent / kg of polymer followed by extraction with water, and in which the molecular weight of the polymer and its end groups are controlled by one of the following methods:- use of low boiling mono-functional end capping agent, such as phenol, 4-phenoxyphenol, 4-fluorobenzophenone, preferably at the start of the reaction; or- use of an excess of 4,4’-difluorobenzophenone of 1.5-2.5 mol% based on hydroquinone with no end capping; or- use of an excess of 4,4’-difluorobenzophenone in one or more termination step in which the amount of 4,4’-difluorobenzophenone used in all of the termination steps is less than 5 mol% based on hydroquinone; or- use of a difluorinated ketone with at least 3 aromatic rings, such as 1 ,4-(bis-4’-fluorobenzoyl)benzene or 1 ,3-(bis-4’- fluorobenzoyl)benzene.

[0028] The excess of 4,4’-difluorobenzophenone is calculated based on the moles of hydroquinone or based on the total amount of diol monomers in the reaction when the PEEK Polymer does not consist of 100 mol% of recurring units of formula (RPEEK).

[0029] The termination agent can be added as a powder or in liquid form.

[0030] The PEEK Polymer Powder may alternatively be prepared according to a process which comprises:- reacting hydroquinone, 4,4’-difluorobenzophenone and optionally other monomers, in a solvent comprising more than 80 wt% diphenyl sulfone, using alkali metal carbonate as base, isolating the polymer by extraction with an organic solvent followed by extraction with water to reduce the organic solvent content to less than 100 ppm, in which the organic solvent is a dipolar aprotic solvent with a dielectric constant of at least 30.

[0031] Dipolar aprotic solvents with a dielectric constant of at least 30 suitable for the process are dimethylacetamide, dimethylformamide or dimethylsulfoxide.

[0032] The concentration of the PEEK Polymer at the end of the polymerization is preferably below 45% solids, calculated as the ratio between the (wt theroretical polymer) / (theoretical polymer wt + wt solvent) expressed in %. The alkali metal carbonate is preferably sodium and / or potassium carbonate, preferably a mixture of sodium and potassium carbonate.

[0033] In general, the process comprises more than one termination steps. It comprises adding the termination agent in more than one step, typically two or more steps. A process for the preparation of PEEK comprising the addition of the termination agent in more than one step is disclosed for instance in EP2178946B1 , the whole content of which is incorporated herein by reference for all purposes.

[0034] The first termination step is conducted with less than 0.5 mol% of any lithium, or alkaline earth metal salt present in the reaction mixture at that stage, this in order to ensure full reactivity of end groups to be end capped. Without wishing to be bound by any theory, the Applicant believes that this ensures a good crystallization rate of the PEEK Polymer, that is a high crystallization temperature. The time between the addition of the first termination agent and lithium, or alkaline earth metal salt is at least 3 minutes to ensure efficient end capping before adding a reagent (lithium or alkaline earth salt) which reduces the reactivity of the end groups.

[0035] The PEEK Polymer Powder is used to manufacture films by extrusion.

[0036] A further object of the invention is therefore a process for the manufacture of films the process comprising a step of melt processing the PEEK Polymer Powder. Melt processing typically takes place in an extruder.

[0037] The process may comprise one step in which the PEEK Polymer Powder is extruded directly into the form of a film.

[0038] Alternatively, the process may comprise a first step in which the PEEK Polymer Powder is melt processed by means of an extruder into pellets which are then further processed into the film. The process accordingly comprises the steps of:(a) providing the PEEK Polymer Powder as defined above;(b) melt processing said PEEK Polymer Powder to provide PEEK Polymer pellets; and(c) extruding said PEEK Polymer pellets into a film.

[0039] The PEEK Polymer is typically selected from polymer having a Mn higher than 42,000, preferably higher than 43,000, more preferably higher than 44,000, and a Mn lower than 58,000, preferably lower than 57,000, more preferably lower than 56,000. The PEEK Polymer then typically has a Mw higher than 90,000, more preferably higher than 95,000, even more preferably higher than 97,000 and a Mw lower than 125,000, more preferably lower than 120,000, even more preferably lower than 115,000, and still more preferably lower than 110,000.

[0040] Without being bound by any theory, the selection of the above mentioned ranges of Mn and Mw allows for good melt strength and high ductility, which are both critical in this application, while minimising viscosity for ease of processing.

[0041] In an embodiment of the process a lubricant is added to the PEEK Polymer pellets before they are extruded into a film.

[0042] Accordingly, the process further comprises a step of adding a lubricant to the PEEK Polymer pellets either before or during step (c).

[0043] The lubricant may be any of the lubricants commonly used in the processing of PEEK polymers. Preferably, the lubricant is a low melting hydrocarbon-based lubricant, more preferably a hydrocarbon-based lubricant having a melting point below 250 °C, even more preferably having a melting point below 200 °C.

[0044] Preferably, said lubricant is based on a saturated hydrocarbon. More preferably the lubricant is selected from fatty acid salts, even more preferably from salts of saturated fatty acids with 10-20 carbon atoms.

[0045] Preferably, said lubricant is selected from calcium stearate, calcium palmitate, magnesium stearate, magnesium palmitate, zinc stearate or zinc palmitate. More preferably, the lubricant is selected from calcium stearate, calcium palmitate, zinc stearate or zinc palmitate; even more preferably from calcium stearate or calcium palmitate. The most preferred lubricant is calcium stearate.

[0046] The amount of lubricant is such that the residual amount of cations deriving from the lubricant, namely Ca, Mg or Zn, is in the range from 6 to 18 ppm, as measured in the PEEK Polymer in the film by ICP-OES (inductively coupled plasma coupled with optical emission spectroscopy) after mineralization by ashing in a platinum crucible.

[0047] The expression “the amount of cations of Ca, Mg or Zn” refers to the total amount of cations of one or more of the metals Ca, Mg or Zn measured in the PEEK Polymer in the film.

[0048] In an alternative embodiment of the process, no lubricant is added to the PEEK Polymer pellets before they are formed into the film. In such an embodiment, the amount of cations of Ca, Mg or Zn in the PEEK Polymer in the article is advantageously no more than 5 ppm, as measured by ICP- OES (inductively coupled plasma coupled with optical emission spectroscopy) after mineralization by ashing in a platinum crucible.

[0049] Advantageously the amount of cations of Ca, Mg or Zn in the PEEK Polymer in the article is less than 4 ppm, even as low as 1 ppm or even as low as 0.5 ppm.

[0050] In this embodiment, melt processing is preferably performed using so- called barrier screws. The expression “barrier screw” is used herein to refer to a screw which comprises a secondary flight starting at the beginning of the screw transition zone and ending at the start of the final metering zone, so that the channel of the screw is divided into two and the melted polymer is separated from the unmolten pellets.

[0051] The extrusion process may be performed using a T-die film-molding device by melting the resin composition, ejecting the molten composition into a film shape through a die, and then taking up the film using a cooling roll.

[0052] The cylinder temperature of the T-die film-molding device may be appropriately set to a temperature within the range where the PEEK Polymer is molten, for example, at 340°C to 400°C. The cooling roll may be set to any temperature, and the temperature is preferably within a range of 150°C to 270°C, more preferably within a range of 180°C to 220°C. If the cooling roll temperature is lower than 150°C or higher than 270°C, the crystallinity of the PEEK Polymer in the film may not increase.The time during which the molten film ejected from the die is in contact with the cooling roll may be adjusted within a range of 1 to 30 seconds.

[0053] In order to further crystallize the film, the production method may also preferably include heating (annealing) the film. In order to progress the crystallization, the heating temperature is preferably within a range of 150°C to 270°C, more preferably within a range of 180°C to 220°C. The heating time may be 0.05 to 100 hours, for example.

[0054] Film molding and optional heating under the above conditions enable production of a film in which the crystallinity of the PEEK Polymer is 10% or higher.

[0055] Melt processing the PEEK Polymer Powder may lead to a reduction of the amount of total extractables due to a certain level of volatilization that takes place during the processing. Accordingly the total amount of extractables in the melt processed pellets of the PEEK Polymer or in the film may be lower than in the powder.

[0056] A further object of the present invention is a film comprising a PEEK Polymer characterised by a total amount of extractables of no more than 3000 pg / g and by an amount of Oligomer 1 of no more than 70 pg / g,the amount of extractables and of Oligomer 1 being determined by Soxhlet extraction with acetone for 48 hours followed by liquid chromatography as detailed in the experimental Section under the heading “Extractables determination”.The total amount of extractables is determined on a sample of the PEEK Polymer which conveniently has a median particle size, dso, in the range of 200 to 300 microns, measured using laser scattering on a dispersion of the particles in 2-propanol. The sample of the PEEK Polymer with the appropriate particle size is obtained from the film by taking an amount of the PEEK Polymer from the article and milling or grinding it to the desired particle size using techniques known to the person skilled in the art.

[0057] The film comprises, essentially consists of, preferably consists of, the PEEK Polymer.

[0058] Preferably, the film is characterised by a total amount of extractables of no more than 2500 pg / g, even no more than 2000 pg / g, and by an amount of Oligomer 1 of no more than 70 pg / g.

[0059] The film generally has a thickness lower than 1.00 mm, even lower than 0.70 mm, even preferably lower than 0.50 mm, more preferably lower than 0.30 mm. The thickness of the film is usually at least 1 pm, typically at least 5 pm.

[0060] Advantageously, the PEEK Polymer in the film has a crystallinity as measured by DSC on the first heat scan of at least 15%, preferably at least 20%, preferably at least 25% with respect to the theoretical crystallinity of PEEK. The level of crystallinity is determined by measuring the heat of fusion on the first heat scan of the PEEK Polymer as detailed in the experimental section.

[0061] The inventive film’s high performance makes it suitable for a wide range of applications that require high temperature performance, lightweight, durability. It can be used in a broad range of markets including electronics, acoustics, aerospace, automotive, industrial, oil and gas, alternative energy and e-mobility.

[0062] The inventive film may be used in electronics applications as circuit board substrate, solder mask tape or in high energy capacitors.

[0063] The inventive film may be used as oil and gas cable wrap, to make RFID tags, as a magnet wire insulation tape, in pressure sensors.

[0064] In particular, the film of the present invention may be used as a slot liner, that is a film used as an electrical insulation barrier in the slots of a stator of an electric motor or generator.

[0065] As the slot liner needs to be cut and shaped to fit within the slots of the stator, it generally has a thickness lower than 0.50 mm, even more preferably lower than 0.20 mm. The thickness of the slot liner is usually at least 0.02 mm. The thickness of the slot liner may be between 0.02 and 0.18 mm, more particularly between 0.05 and 0.15 mm.

[0066] The film of the present invention may be used as a diaphragm (vibrating membrane) of speakers, headphones or earphones.

[0067] Still, the film of the present invention may be used in aerospace applications as an insulating film, for instance in cabin interior components, as fuel pipe protecting materials, as backing for adhesive tapes or as component in composite materials.

[0068] Other objects of the present invention are devices comprising the film comprising the PEEK Polymer. Among devices notable non-limiting examples are electric motors, electric generators, speakerphones, headphones, earphones.

[0069] 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.

[0070] The disclosure is now described in more detail with reference to the following examples, whose purpose is merely illustrative and not intended to limit the scope of the disclosure.Experimental Section

[0071] Raw Materials

[0072] Hydroquinone (HQ), photographic grade, was procured from Eastman, USA, containing 0.38 wt% moisture, which amount was used to adapt the charge weights. All weights indicated include moisture.

[0073] 4,4’-Difluorobenzophenone (DFBP), polymer grade (99.8%+), was procured from Malwa, India and was shown to contain oxidising species in a concentration less than 3.0 pmol TiCh / g as measured by redox titration as described in WO2012 / 001131 .

[0074] Diphenyl sulfone (DPS) (polymer grade) was procured from Proviron (99.8% pure).

[0075] Sodium carbonate, light soda ash, was procured from Solvay S.A., France.

[0076] Potassium carbonate with a doo < 45 pm was procured from Armand products.

[0077] Lithium chloride (anhydrous grade) was procured from Acres.

[0078] Determination of Mn and Mw by Gel Permeation Chromatography (GPC)

[0079] Molecular weights of the sample were determined by PL 220 high temperature GPC system using conditions described in Table 1 below.Table 1

[0080] The sample concentration was ~0.20% wt. / vol. in mobile phase. The sample was dissolved by heating at about 190°C under magnetic stirring until complete dissolution. GPC method used was similar to ASTM D5296 but modified due to the need of different solvent, GPC column and conditions. Calibration was carried out using 11 narrow calibration standards of Polystyrene (standards purchased from Agilent Technologies having peak molecular weight range: 1210000 to 580)

[0081] Determination of the melting temperature (Tm ), crystallization temperature (Tc) and heat of fusion

[0082] The heat of fusion was determined on the melting endotherm of the first heat scan in differential scanning calorimeter (DSC) according to ASTM D3418-03, E1356-03, E793-06, E794-06.

[0083] Details of the procedure as used herein are as follows: a TA Instruments DSC Q20 was used with nitrogen as carrier gas (99.998% purity, 50 mL / min). Temperature and heat flow calibrations were done using indium. Sample size was 5 to 7 mg. The weight was recorded ±0.01 mg. The heat cycles were:1st heat cycle: 30.00°C to 400.00°C at 20.00°C / min, isothermal at 400.00°C for 1 min;1st cool cycle: 400.00°C to 30.00°C at 20.00°C / min, isothermal for 1 min; 2nd heat cycle: 30.00°C to 400.00°C at 20.00°C / min, isothermal at 400.00°C for 1 min.

[0084] The melting temperature of the composition was taken as the area over a linear baseline drawn from 220°C to a temperature above the last endotherm. Any exotherm associated with cold crystallisation is taken intoaccount for the total heat of fusion measured on the 1 st heat scan. The % crystallinity is defined as 100 x heat of fusion (J / g) 1 130 (J / g).

[0085] The crystallization temperature Tc was determined as the peak temperature of the crystallization exotherm on the 1stcool cycle.

[0086] Extractables Determination

[0087] The total amount of extractable was quantified by Soxhlet extraction. The analysis was performed on PEEK powder having a median particle size (dso determined by laser scattering in wet mode in 2-propanol) in the range of 200 to 300 pm. Grinding and / or sieving was performed on the sample to adjust the particle size to obtain a median diameter in the 200-300 pm range.

[0088] 8.000 g of PEEK powder were introduced in a cellulose extraction thimble (25 mm internal diameter x 80 mm height) and placed in a 50 mL Soxhlet extractor with cotton wool (rinsed with acetone before use) on top of the powder to avoid powder overflowing. The extractor, with a reflux condenser refrigerated with chilled water (4 °C), was fitted on a 500 mL 3- neck jacketed round bottom flask, along with a thermocouple and a nitrogen inlet line. 250 mL acetone with distillation beads were added and heat was applied via the reactor jacket to reflux the acetone. The reflux rate was adapted to have the Soxhlet extractor fill and empty once every 3 to 5 minutes. After 48h, the heat source was removed and the acetone extract cooled down to room temperature. The extract was concentrated on a Rotavapor and dried to constant weight at room temperature under vacuum.

[0089] The weight of extract represents the total amount of extractables / g polymer.

[0090] The extract was analyzed by HPLC under the following conditions.

[0091] The sample was prepared by dissolution of 15-40 mg in 100 mL dimethylformamide.

[0092] The equipment was an Alliance 2695 Liquid Chromatograph with 2996 PDA detector or equivalent and the column was Supelco Discovery C-18, 250mm x 4.6mm; 5mm particle size.

[0093] The mobile phase contained acetonitrile and water according to the following gradient program:Flow Rate: 1.00 mL / minuteRun Time: 30 minutesPDA Detector: 254 nm

[0094] Under these conditions, diphenyl sulfone eluted at 5.7 minutes and 4,4’- difluorobenzophenone at 7.1 minutes. These two compounds could be quantified in the extract and consequently in the polymer using external standards.

[0095] Other species present in the total extractable, mainly oligomers of different structures, were detected at 9.5, 10.4, 12.1 , 13.2, 16.0 and 19.7 minutes.

[0096] The compounds peak retention times can be identified by LC-MS or by preparing actual standards. Oligomer 1 was prepared according to Fukawa et al, Journal of Polymer Science : Part A : Polymer Chemistry, 1993, Vol 31 , P 535-546.

[0097] Using the standard the peak at 10.4 minutes was attributed to Oligomer 1. The concentration of Oligomer 1 was determined using 4,4’- difluorobenzophenone as external standard.

[0098] Determination of metals such as calcium and magnesium in PEEK polymer by ICP-OES

[0099] A clean, dry platinum crucible was placed onto an analytical balance, and the balance was zeroed. One half to 3 grams of polymer sample was weighed into a boat and its weight was recorded to 0.0001 g. The crucible with sample was placed in a muffle furnace (Thermo Scientific Thermolyne F6000 Programmable Furnace). The furnace was gradually heated to 525°C and held at that temperature for 10 hours to dry ash the sample. Following ashing, the furnace was cooled down to room temperature, and the crucible was taken out of the furnace and placed in a fume hood. The ash was dissolved in diluted hydrochloric acid. The solution wastransferred to a 25 mL volumetric flask, using a polyethylene pipette. The crucible was rinsed twice with approximately 5 mL of ultrapure water (R<18 MQcm) and the washes were added to a volumetric flask to effect a quantitative transfer. Ultrapure water was added to total 25 mL in the flask. A stopper was put on the top of the flask and the contents were shaken well to mix.

[0100] ICP-OES analysis was performed using an inductively-coupled plasma emission spectrometer Perkin-Elmer Optima 8300 dual view. The spectrometer was calibrated using a set of NIST traceable multi-element mixed standards with analyte concentrations between 0.0 and 10.0 mg / L. A linear calibration curve was obtained in a range of concentrations with a correlation coefficient better than 0.9999 for each of 48 analytes. The standards were run before and after every ten samples to ensure instrument stability. The results were reported as an average of three replicates. The concentration of elemental metals in the sample was calculated with the following equation:A = (B * C) / (D) where:A = concentration of element in the sample in mg / kg (=wt.ppm) B = element in the solution analysed by ICP-OES in mg / L C = volume of the solution analysed by ICP-OES in mL D = sample weight in grams used in the procedure.

[0101] Comparative Example 1 : PEEK with total amount of extractables > 3000 pq / g and an amount of Oligomer 1 > 70 pq / g

[0102] In a 500 mL 4-neck reaction flask fitted with a stirrer, a N2 inlet tube, a Claisen adapter with a thermocouple plunging in the reaction medium, and a Dean-Stark trap with a condenser and a dry ice trap were introduced 127.82 g of diphenyl sulfone, 28.685 g of hydroquinone and 57.213 g of 4,4’-difluorobenzophenone. The flask content was evacuated under vacuum and then filled with high purity nitrogen (containing less than 10 ppm O2). The reaction mixture was then placed under a constant nitrogen purge (60 mL / min).

[0103] The reaction mixture was heated slowly to 150 °C. At 150 °C, a mixture of 28.619 g of Na2COs and 0.180 g of K2CO3 was added via a powderdispenser to the reaction mixture over 30 minutes. At the end of the addition, the reaction mixture was heated to 320 °C at 1 °C / minute. The mixture was held at 320 °C until the target viscosity was reached, in this case for 34 minutes, then the reaction was terminated in 3 stages : 6.817 g of 4,4’-difluorobenzophenone were added to the reaction mixture while keeping a nitrogen purge on the reactor. After 5 minutes, 0.444 g of lithium chloride were added to the reaction mixture. 10 minutes later, another 2.227 g of 4,4’-difluorobenzophenone were added to the reactor and the reaction mixture was kept at temperature for 15 minutes.

[0104] The reactor content was then poured from the reactor into a SS pan and cooled. The solid was broken up and ground in an attrition mill through a 2 mm screen. Diphenyl sulfone and salts were extracted from the mixture by extracting successively with 6 times 1 .2 L of acetone and 7 times with 1 ,2L of DM water at room temperature. The powder was then dried at 120 °C under vacuum for 12 hours yielding 67 g of a white powder and its properties are detailed in Table 1 .

[0105] Example 1 : PEEK with total amount of extractables < 3000 pq / g and an amount of Oligomer 1 < 70 pq / g

[0106] In a 500 mL 4-neck reaction flask fitted with a stirrer, a N2 inlet tube, a Claisen adapter with a thermocouple plunging in the reaction medium, and a Dean-Stark trap with a condenser and a dry ice trap were introduced 127.82 g of diphenyl sulfone, 28.685 g of hydroquinone, 57.402 g of 4,4’- difluorobenzophenone and 0.485 g of 4-phenoxyphenol. The flask content was evacuated under vacuum and then filled with high purity nitrogen (containing less than 10 ppm O2). The reaction mixture was then placed under a constant nitrogen purge (60 mL / min).

[0107] The reaction mixture was heated slowly to 150 °C. At 150 °C, a mixture of 27.598 g of Na2COs and 0.720 g of K2CO3 was added via a powder dispenser to the reaction mixture over 30 minutes. At the end of the addition, the reaction mixture was heated to 200 °C and held for 1 h at that temperature, then heated up to 250 °C and held at 250 °C for 1 h. Finally, the reaction mixture was heated to 315 °C and held at 315 °C until the target viscosity was reached, in this case for 57 minutes.

[0108] The reactor content was then poured from the reactor into a SS pan and cooled. The solid was broken up and ground in an attrition mill through a 2 mm screen. Diphenyl sulfone and salts were extracted from the mixture by extracting successively with 6 times 1 ,2L of acetone and 7 times with 1 ,2L of DM water at room temperature. The powder was then dried at 120 °C under vacuum for 12 hours yielding 67 g of a white powder and its properties are detailed in Table 1 .

[0109] Example 2: PEEK with total amount of extractables < 3000 pq / g and an amount of Oligomer 1 < 70 pq / g

[0110] In a 500 mL 4-neck reaction flask fitted with a stirrer, a N2 inlet tube, a Claisen adapter with a thermocouple plunging in the reaction medium, and a Dean-Stark trap with a condenser and a dry ice trap were introduced 127.82 g of diphenyl sulfone, 28.685 g of hydroquinone, 57.402 g of 4,4’- difluorobenzophenone and 0.490 g of phenol. The flask content was evacuated under vacuum and then filled with high purity nitrogen (containing less than 10 ppm O2). The reaction mixture was then placed under a constant nitrogen purge (60 mL / min).

[0111] The reaction mixture was heated slowly to 150 °C. At 150 °C, a mixture of 27.598 g of Na2COs and 0.720 g of foCC was added via a powder dispenser to the reaction mixture over 30 minutes. At the end of the addition, the reaction mixture was heated to 200 °C and held for 1 h at that temperature, then heated up to 250 °C and held at 250 °C for 1 h. Finally, the reaction mixture was heated to 315 °C and held at 315 °C until the target viscosity was reached, in this case for 1 hi 1 minutes.

[0112] The reactor content was then poured from the reactor into a SS pan and cooled. The solid was broken up and ground in an attrition mill through a 2 mm screen. Diphenyl sulfone and salts were extracted from the mixture by extracting successively with 6 times 1 ,2L of acetone and 7 times with 1 ,2L of DM water at room temperature. The powder was then dried at 120 °C under vacuum for 12 hours yielding 67 g of a white powder and its properties are detailed in Table 1 .

[0113] Example 3: PEEK with total amount of extractables < 3000 pq / g and an amount of Oligomer 1 < 70 pq / g

[0114] In a 500 mL 4-neck reaction flask fitted with a stirrer, a N2 inlet tube, a Claisen adapter with a thermocouple plunging in the reaction medium, and a Dean-Stark trap with a condenser and a dry ice trap were introduced 127.82 g of diphenyl sulfone, 28.685 g of hydroquinone and 57.213 g of 4,4’-difluorobenzophenone. The flask content was evacuated under vacuum and then filled with high purity nitrogen (containing less than 10 ppm O2). The reaction mixture was then placed under a constant nitrogen purge (60 mL / min).

[0115] The reaction mixture was heated slowly to 150 °C. At 150 °C, a mixture of 28.619 g of Na2COs and 0.180 g of K2CO3 was added via a powder dispenser to the reaction mixture over 30 minutes. At the end of the addition, the reaction mixture was heated to 320 °C at 1 °C / minute. The mixture was held at 320 °C until the target viscosity was reached, in this case for 14 minutes, then the reaction was terminated in 2 stages : 0.839 g of 1 ,4-bis(4’-fluorobenzoyl)benzene were added to the reaction mixture while keeping a nitrogen purge on the reactor. After 5 minutes, 0.444 g of lithium chloride were added to the reaction mixture. The reactor content was then poured from the reactor into a SS pan and cooled. The solid was broken up and ground in an attrition mill through a 2 mm screen. Diphenyl sulfone and salts were extracted from the mixture by extracting successively with 6 times 1 .2 L of acetone and 7 times with 1 ,2L of DM water at room temperature. The powder was then dried at 120 °C under vacuum for 12 hours yielding 67 g of a white powder and its properties are detailed in Table 1 .

[0116] Example 4: PEEK with total amount of extractables < 3000 pq / g and an amount of Oligomer 1 < 70 pq / g

[0117] The same procedure as for CE1 was followed except that the polymer was washed with 6 times 1 .2 L of dimethylformamide and 8 times with 1 ,2L of DM water at room temperature. The polymer properties are detailed in Table 1 .

[0118] Example 5: PEEK with total amount of extractables < 3000 pq / g and an amount of Oligomer 1 < 70 pq / g

[0119] In a 500 mL 4-neck reaction flask fitted with a stirrer, a N2 inlet tube, a Claisen adapter with a thermocouple plunging in the reaction medium, anda Dean-Stark trap with a condenser and a dry ice trap were introduced 127.82 g of diphenyl sulfone, 28.685 g of hydroquinone and 57.213 g of 4,4’-difluorobenzophenone. The flask content was evacuated under vacuum and then filled with high purity nitrogen (containing less than 10 ppm O2). The reaction mixture was then placed under a constant nitrogen purge (60 mL / min).

[0120] The reaction mixture was heated slowly to 150 °C. At 150 °C, a mixture of 28.619 g of Na2COs and 0.180 g of K2CO3 was added via a powder dispenser to the reaction mixture over 30 minutes. At the end of the addition, the reaction mixture was heated to 320 °C at 1 °C / minute. The mixture was held at 320 °C until the target viscosity was reached, in this case for 14 minutes, then the reaction was terminated in 2 stages : 1 .136 g of 4,4’-difluorobenzophenone were added to the reaction mixture while keeping a nitrogen purge on the reactor. After 7 minutes, 0.444 g of lithium chloride were added to the reaction mixture. The reactor content was then poured from the reactor into a SS pan and cooled. The solid was broken up and ground in an attrition mill through a 2 mm screen. Diphenyl sulfone and salts were extracted from the mixture by extracting successively with 6 times 1 .2 L of acetone and 7 times with 1 ,2L of DM water at room temperature. The powder was then dried at 120 °C under vacuum for 12 hours yielding 67 g of a white powder and its properties are detailed in Table 1 .

[0121] Example 6: PEEK with total amount of extractables < 3000 pq / g and an amount of Oligomer 1 < 70 pq / g

[0122] In a 500 mL 4-neck reaction flask fitted with a stirrer, a N2 inlet tube, a Claisen adapter with a thermocouple plunging in the reaction medium, and a Dean-Stark trap with a condenser and a dry ice trap were introduced 127.82 g of diphenyl sulfone, 28.685 g of hydroquinone and 57.213 g of 4,4’-difluorobenzophenone. The flask content was evacuated under vacuum and then filled with high purity nitrogen (containing less than 10 ppm O2). The reaction mixture was then placed under a constant nitrogen purge (60 mL / min).

[0123] The reaction mixture was heated slowly to 150 °C. At 150 °C, a mixture of 28.619 g of Na2COs and 0.180 g of K2CO3 was added via a powderdispenser to the reaction mixture over 30 minutes. At the end of the addition, the reaction mixture was heated to 320 °C at 1 °C / minute. The mixture was held at 320 °C until the target viscosity was reached, in this case for 15 minutes, then the reaction was terminated in 3 stages : 6.256 g of 4-fluorobenzophenone were added to the reaction mixture while keeping a nitrogen purge on the reactor. After 5 minutes, 0.444 g of lithium chloride were added to the reaction mixture. 10 minutes later, another 2.085 g of 4-fluorobenzophenone were added to the reactor and the reaction mixture was kept at temperature for 15 minutes.

[0124] The reactor content was then poured from the reactor into a SS pan and cooled. The solid was broken up and ground in an attrition mill through a 2 mm screen. Diphenyl sulfone and salts were extracted from the mixture by extracting successively with 6 times 1 .2 L of acetone and 7 times with 1 ,2L of DM water at room temperature. The powder was then dried at 120 °C under vacuum for 12 hours yielding 67 g of a white powder and its properties are detailed in Table 1 .Table 1

[0125] The analysis of the Soxhlet extracts by liquid chromatography shows that the polymer produced according to the invention contains reduced amounts of extractable compounds.

[0126] General procedure for the pelletization of PEEK powder

[0127] PEEK powder prepared under the conditions detailed above (but at a larger scale) was pelletized by melt processing on a 26 mm diameterCoperion® co-rotating partially intermeshing twin screw extruder having an L / D ratio of 48:1 . The extruder was equipped with 12 barrel sections, with barrel sections 2 through 12 being temperature controlled. The extruder was fitted with a 3-mm diameter single-hole die. The resin feeder fed into the feed hopper (barrel section 1 ). Vacuum venting with a vacuum level > 25 in Hg was applied at barrel section 10 during the compounding to strip off moisture and any possible residual volatiles from the compounds. The extrudate from each of the compositions was stranded and the strands were cooled in a water trough and then pelletized using a Maag Primo 60 E pelletizer into pellets. See Table 2 for extrusion conditions.Table 2 : Pelletization conditions for PEEK

[0128] Example 7 - Analysis of Pellets of the PEEK polymers of Comparative Example 1, Examples 2 and 5

[0129] The extrusion of PEEK lots was made according to the general procedure. No white residue was observed on the die during the preparation of pellets using the PEEK polymers of Examples 2 and 5, while a white residue was observed for the polymer of CE1 .

[0130] Hence PEEK polymers with less than 70 pq / g of Oligomer 1 and a total amount of extractables below 3000 pq / g were shown to successfully solve the issue of die lip build-up during melt processing.

Claims

Claims1 . Use of a PEEK polymer powder to manufacture films by extrusion, wherein the PEEK polymer powder is characterised by a total amount of extractables of no more than 3000 pg / g and by an amount of Oligomer 1 of no more than 70 pg / g[Oligomer 1], and wherein the amount of extractables and of Oligomer 1 are determined by Soxhlet extraction with acetone for 48 hours followed by liquid chromatography.

2. The use of claim 1 wherein the PEEK polymer comprises at least 80 mol%, 85 mol%, more preferably at least 90 mol%, even more preferably at least 95 mol%, at least 98 mol%, at least 99 mol% or 100 mol% of units of formula (RPEEK):and up to 1 mol%, up to 2 mol%, up to 5 mol%, up to 10 mol%, up to 15 mol% or up to 20 mol% of at least one unit having formula (K-A) to (K-P):wherein each R’ is independently selected from halogen, an alkyl, an alkenyl, an alkynyl, an aryl, an ether, a thioether, a carboxylic acid, an ester, an amide, an imide, an alkali or an alkaline earth metal sulfonate, an alkyl sulfonate, an alkali or alkaline earth metal phosphonate, an alkyl phosphonate, an amine and a quaternary ammonium; and each j’ is independently 0 or an integer from 1 to 4.

3. A process for the manufacture of the PEEK polymer powder as defined in claim 1 or 2 which comprises: reacting hydroquinone, 4,4’- difluorobenzophenone and optionally the other monomers, in a solvent comprising more than 80 wt% diphenyl sulfone, using alkali metal carbonate as base; and isolating the polymer by extraction with an organic solvent using at least 50 L organic solvent / kg of polymer followed by extraction with water, characterized in that the molecular weight of the polymer and its end groups are controlled by one of the following methods:- use of low boiling mono-functional end capping agent, such as phenol, 4-phenoxyphenol, 4-fluorobenzophenone, preferably at the start of the reaction; or- use of an excess of 4,4’-difluorobenzophenone of 1 .5-2.5 mol% based on the moles of hydroquinone with no end capping; or- use of an excess of 4,4’-difluorobenzophenone in one or more termination step in which the amount of 4,4’-difluorobenzophenone used in all of the termination steps included is less than 5 mol% based on the moles of hydroquinone; or- use of a difluorinated ketone with at least 3 aromatic rings, such as 1 ,4- (bis-4’-fluorobenzoyl)benzene or 1 ,3-(bis-4’-fluorobenzoyl)benzene.

4. A process for the manufacture of the PEEK polymer powder as defined in claim 1 or 2 which comprises reacting hydroquinone, 4,4’-difluorobenzophenone and optionally other monomers, in a solvent comprising more than 80 wt% diphenyl sulfone, using alkali metal carbonate as base, isolating the polymer by extraction with an organic solvent followed by extraction with water to reduce the organic solvent content to less than 100 ppm, in which the organic solvent is a dipolar aprotic solvent with a dielectric constant of at least 30.

5. Process for the manufacture of films comprising a step of melt processing the PEEK polymer powder as defined in claim 1 or 2.

6. The process of claim 5 wherein the PEEK polymer powder as defined in claim 1 or 2 is melt processed by means of an extruder directly into the form of a film.

7. The process of claim 5 which comprises the steps of:(a) providing the PEEK polymer powder as defined in claim 1 or 2;(b) melt processing said PEEK polymer powder to provide PEEK polymer pellets; and(c) extruding said PEEK polymer pellets into a film.

8. The process according to claim 7 wherein the PEEK polymer pellets in step (c) do not contain any lubricant.

9. The process according to claim 7 which comprises the further step of adding a lubricant to the PEEK polymer pellets either before or during step (c).

10. The process according to any one of claims 5 to 9, in which the PEEK polymer has:- a number average molecular weight (Mn) higher than 42,000, preferably higher than 43,000, more preferably higher than 44,000, as measured by GPC at 160 °C in 1 , 2, 4-trichlorobenzene: Phenol (50:50) using PS standards, and / or lower than 58,000, preferably lower than 57,000, more preferably lower than 56,000, as measured by GPC at 160 °C in 1 ,2,4- trichlorobenzene: phenol (50:50) using PS standards; and / or- a weight average molecular weight (Mw) higher than 90,000, more preferably higher than 95,000, even more preferably higher than 97,000, as measured by GPC at 160 °C in 1 ,2,4-trichlorobenzene:phenol (50:50) using PS standards, and / or lower than 125,000, more preferably lower than 120,000, even more preferably lower than 115,000, and still morepreferably lower than 110,000, as measured by GPC at 160 °C in 1 ,2,4- trichloro- benzene:phenol (50:50) using PS standards.11 . Pellets comprising a PEEK polymer characterised by a total amount of extractables of no more than 3000 pg / g and by an amount of Oligomer 1 of no more than 70 pg / g,[Oligomer 1], the amount of extractables and of Oligomer 1 being determined by Soxhlet extraction with acetone for 48 hours followed by liquid chromatography.

12. The pellets of claim 11 that do not contain any lubricant and / or in which the amount of cations of Ca, Mg or Zn is no more than 5 ppm, as measured by ICP-OES (inductively coupled plasma coupled with optical emission spectroscopy) after mineralization by ashing in a platinum crucible.

13. The pellets of claim 11 that contain a lubricant and / or in which the amount of cations of Ca, Mg or Zn is in the range of 6 to 18 ppm, as measured by ICP-OES (inductively coupled plasma coupled with optical emission spectroscopy) after mineralization by ashing in a platinum crucible.

14. The process of claim 9 or the pellets of claim 13 wherein the lubricant is selected from the group consisting of calcium stearate, calcium palmitate, magnesium stearate, magnesium palmitate, zinc stearate or zinc palmitate; preferably from calcium stearate, calcium palmitate, zinc stearate or zinc palmitate; more preferably from calcium stearate or calcium palmitate.

15. A film comprising a PEEK polymer characterised by a total amount of extractables of no more than 3000 pg / g and by an amount of Oligomer 1 of no more than 70 pg / g,[Oligomer 1], the amount of extractables and of Oligomer 1 being determined by Soxhlet extraction with acetone for 48 hours followed by liquid chromatography.

16. The film according to claim 15 wherein the total amount of extractables is no more than 2000 pg / g.

17. The film according to claim 15 or 16 which has a thickness of less than 1.00 mm, even less than 0.70 mm, preferably less than 0.50 mm, more preferably less than 0.30 mm and / or at least 1 pm, typically at least 5 pm.

18. The film according to any one of claims 15 to 17 in which the amount of cations of Ca, Mg or Zn is no more than 5 ppm, as measured by ICP-OES (inductively coupled plasma coupled with optical emission spectroscopy) after mineralization by ashing in a platinum crucible.

19. The film according to any one of claims 15 to 17 in which the amount of cations of Ca, Mg or Zn is from 6 to 18 ppm, as measured by ICP-OES (inductively coupled plasma coupled with optical emission spectroscopy) after mineralization by ashing in a platinum crucible.

20. The film according to any one of claims 15 to 19 which consists of the PEEK polymer.21 . The film according to any one of claims 15 to 20 which has a crystallinity, measured by DSC on the first heat scan, of at least 15%, preferably at least 20%, preferably at least 25% with respect to the theoretical crystallinity of PEEK.

22. The film of any one of claims 15 to 21 which is a circuit board substrate, solder mask tape, cable wrap, RFID tags backing, a magnet wire insulation tape, slot liner, a diaphragm (vibrating membrane) in speakers, headphones or earphones; an insulating film in aircraft cabin interior components, fuel pipe protecting materials, backing for adhesive tapes or a component in composite materials.

23. The film of anyone of claims 15 to 22 which is a slot liner a diaphragm or an insulating material.

24. A device comprising the film of any one of claims 15 to 23.

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