METHOD FOR DOUBLE SHEET THERMOFORMING OF HOLLOW BODIES AND RESULTING HOLLOW BODIES - Patent application

Abstract

The present invention relates to the use of a sheet comprising at least one face of a quasi-amorphous composition based on polyaryletherketone for a double-sheet thermoforming process, to a corresponding method and to the hollow bodies obtained by this method.

Description

[Technical field]

[0001] The present invention relates to the field of twin-sheet thermoforming processes for hollow bodies.

[0002] More precisely, the invention relates to such a method using a sheet based on polyaryletherketone. [Background technology]

[0003] Polyaryletherketones are well-known high performance engineering polymers. They can be used for applications that are restrictive in terms of temperature and / or mechanical or even chemical constraints. They can also be used for applications that require good fire resistance and low smoke or toxic gas emissions. Finally, they have good biocompatibility. These polymers are found in diverse fields such as aerospace, offshore drilling, automotive, rail, marine, wind, sports, architecture, electronics or other medical implants.

[0004] Methods for twin-sheet thermoforming of thermoplastics are also known from the prior art. In particular, they allow the production of hollow rigid articles.

[0005] The twin sheet thermoforming process involves thermoforming two sheets to form two halves of an article and welding the halves together to form a hollow article.

[0006] Two methods are particularly known.

[0007] According to the first method, two thermoplastic polymer sheets are placed in a fixed frame and heated simultaneously. Once the sheets have reached the forming temperature, i.e., have softened sufficiently, air is pumped between the sheets and / or a vacuum is applied to the outer portions of the sheets, and they are forced into two mold halves that can be closed and pressed together, creating a pinching effect.

[0008] According to the second method, two sheets are thermoformed in succession in their respective mold halves, which are then closed and pressed together, creating a sandwich effect.

[0009] An example of implementation with thermoplastic polymers having high heat deflection temperature (HHDT) is described in US Patent No. 5,114,767 A2. HHDT polymers in the sense of the art include polyetherimides, polyamideimides, polyimides, polysulfones, polyethersulfones, polyphenylsulfones, polyetheretherketones, polyetherketoneketones, polyarylsulfones, aromatic polyamides, polyarylsulfones, and polyphenylether / polystyrene blends.

[0010] Two layers of thermoplastic HHDT polymer, such as those mentioned above, are first heated above their deflection temperature and placed between two half molds heated below said deflection temperature. A layer of low heat deflection temperature polymer (LHDT) is sandwiched between the two layers of thermoplastic HHDT polymer. The two half molds are then closed together and adhesion between the two layers of HHDT polymer is ensured by the presence of the LHDT polymer. Finally, the hollow body is formed by injecting gas into the mold.

[0011] This technique has the disadvantage of requiring the addition of an adhesive layer between the two layers intended primarily to form a hollow body.

[0012] At present, the use of polyaryletherketones in thermoforming processes is necessary to produce high performance crystallized hollow bodies. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] U.S. Patent No. 5,114,767 A2 Summary of the Invention [Problem to be solved by the invention]

[0014] The present invention provides a twin-sheet thermoforming process comprising at least two sheets of polyaryletherketone that can be crystallized without the need for an additional intermediate layer. [Means for solving the problem]

[0015] The present invention relates to a twin-sheet thermoforming method for producing hollow bodies, the method comprising the steps of: - providing two sheets, at least one surface of which comprises a polyaryletherketone-based pseudo-amorphous composition; - softening the two sheets at a softening temperature to form a softened sheet, the softening temperature being equal to or greater than the glass transition temperature of each of the quasi-amorphous compositions; - forming the softened sheet into a thermoformed sheet; - contacting and fusing at least one contact area of ​​said faces of the softened sheet and / or the sheet to be shaped or already shaped to form an intermediate body, the contact areas being heated to a contact temperature and each contact area remaining in an essentially amorphous state at least until contact; and - crystallizing the composition at a mold temperature to form a crystallized hollow body, the crystallization step being carried out essentially after the contacting and fusing steps, preferably essentially after the forming step.

[0016] Advantageously, the composition may have a viscosity at 380° C., 1 Hz, measured by a parallel plate rheometer, ranging from 200 Pa.s to 8000 Pa.s, preferably from 500 Pa.s to 5000 Pa.s, and more preferably from 750 Pa.s to 4500 Pa.s.

[0017] Advantageously, the composition may have an isothermal crystallization half-time at the contact temperature of at least 3 seconds, preferably at least 5 seconds, most preferably at least 8 seconds, and / or not more than 30 minutes, preferably not more than 10 minutes, more preferably not more than 5 minutes, most preferably not more than 2 minutes.

[0018] According to some embodiments, the polyaryletherketone may be a polyetherketoneketone, which preferably has at least one chemical formula

[0019] [ka]

[0020] and in the case of copolymers, the repeating unit (I) has the formula

[0021] [ka]

[0022] The copolymer may be a homopolymer or copolymer consisting essentially of or consisting of terephthalic acid repeat units (T) having the formula: The molar percentage of T units relative to the total of T units and I units is 0% to 5%, or 35% to 78%, preferably 45% to 75%, and most preferably 48% to 52%, or 65% to 74%.

[0023] According to some embodiments, the polyaryletherketone has the formula

[0024] [ka]

[0025] Repeating units of the formula

[0026] [ka]

[0027] It may be a copolymer consisting essentially of, or consisting of, the repeat unit The molar percentage of the unit (III) relative to the total of the unit (III) and the unit (IV) is 0% to 99%, preferably 5% to 95%, more preferably 10% to 50%, and most preferably 20% to 40%.

[0028] According to some embodiments, the polyaryletherketone has the formula

[0029] [ka]

[0030] and repeating units having the formula

[0031] [ka]

[0032] and the copolymer may be essentially or consist of repeat units having the following structure: The molar percentage of the unit (III) based on the total of the unit (III) and the unit (V) is from 0% to 99%, preferably from 0% to 95%.

[0033] According to some embodiments, the composition can include at least one other thermoplastic polymer different from the polyaryletherketone, and / or can include at least one filler, and / or can include at least one additive.

[0034] According to some embodiments, the composition may consist of polyaryletherketone, optionally one or more other thermoplastic polymers different from the polyaryletherketone, optionally one or more fillers, and optionally one or more additives.

[0035] According to some embodiments, each sheet, independently or not, may consist of a polyaryletherketone based pseudo-amorphous composition.

[0036] Advantageously, the two sheets, independent of each other or not, may have a thickness between 200 microns and 20 millimeters, preferably between 500 microns and 10 millimeters.

[0037] Advantageously, the crystallization step can be carried out to an average crystallinity in the thickness direction measured by WAXS during the crystallization step strictly greater than 7%, preferably to a crystallinity of 10% or more, or 15% or more, or 20% or more, or even 25% or more.

[0038] Advantageously, the softening step can be carried out at a softening temperature strictly above Tg and having a value up to (Tg+80)°C, preferably having a value ranging from (Tg+10)°C to (Tg+75)°C.

[0039] Advantageously, the crystallization step can be carried out at a mold temperature close to the temperature at which the composition exhibits a minimum isothermal crystallization half-time.

[0040] Advantageously, the difference between the mold temperature and the softening temperature is less than or equal to 50°C, preferably greater than or equal to 15°C.

[0041] According to some embodiments, the contacting and fusing step is carried out at a pinch pressure having a value ranging from 1 bar to 50 bar, preferably at a pinch pressure having a value ranging from 5 bar to 40 bar, more preferably at a pinch pressure having a value ranging from 7 bar to 30 bar.

[0042] The invention also relates to a hollow body comprising at least one internal surface made of a crystallized composition based on polyaryletherketone, obtainable by the process as described above.

[0043] The invention is based on the use by the inventors of a sheet comprising at least one face of a quasi-amorphous composition based on polyaryletherketone for a twin-sheet thermoforming process for producing hollow bodies. The use of such a sheet can be carried out in particular in the process as described above. These sheets make it possible to carry out a good quality heat seal in the contact area between the sheets, since the composition of each sheet remains essentially amorphous until the compositions are brought into contact and fused. The composition of each sheet is nevertheless crystallizable and crystallizes after the compositions are brought into contact and fused. Thus, the inventors have been able to use hollow bodies crystallized from a sheet of a quasi-amorphous composition based on polyaryletherketone, taking advantage of the particularly favorable crystallization kinetics of quasi-amorphous polyaryletherketone, without the need to use an adhesive interlayer. [Brief description of the drawings]

[0044] [Figure 1] 1 is a schematic diagram of a twin sheet thermoforming apparatus. [Diagram 2] FIG. 2 is a block diagram showing the main steps of a twin-sheet thermoforming method according to a first embodiment, for which the apparatus according to FIG. 1 is particularly suitable. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] definition T g The term "glass transition temperature", expressed as t, means the temperature at which an at least partially amorphous polymer changes from a rubbery to a glassy state or vice versa, measured by differential scanning calorimetry (DSC) according to standard NF ISO 11357-2:2020, using a heating rate of 20° C. / min, at the second heat.

[0046] In the present invention, when reference is made to the glass transition temperature, it relates more specifically to the glass transition temperature at half the height of the step as defined in this standard, unless otherwise stated. In the present invention, a composition based on PAEK(s) may optionally show several glass transition levels in the DSC analysis, in particular due to the presence of several different immiscible polymers, if necessary. In this case, the term "glass transition temperature" is understood to mean the highest glass transition temperature corresponding to the glass transition step of the PAEK or mixture of PAEKs.

[0047] T f The term "melting temperature", expressed as , means the temperature at which an at least partially crystallized polymer changes into a viscous liquid state, measured by differential scanning calorimetry (DSC) according to standard NF EN ISO 11357-3:2018, at the first heat, using a heating rate of 20 ° C. / min. In the present invention, when reference is made to the melting temperature, it is more specifically the peak melting temperature as defined in this standard, unless otherwise stated. In the present invention, the composition based on PAEK(s) may optionally show several melting peaks in the DSC analysis, in particular and / or due to the presence of different crystalline forms for a given polymer. In this case, melting temperature is understood to mean the melting temperature corresponding to the melting peak whose temperature is the highest.

[0048] The terms "pseudo-amorphous" polymer and "pseudo-amorphous" composition are understood to refer to a polymer, composition, respectively, that is essentially in amorphous form below its glass transition temperature. The polymer or composition is nevertheless capable of crystallization when heated above its glass transition temperature for a sufficient time. Within the meaning of the present invention, a "pseudo-amorphous" polymer or "pseudo-amorphous" composition, respectively, has a crystallinity of 0% to 7% at 25°C.

[0049] "Crystallization" can be measured by WAXS. For example, the analysis can be performed in wide-angle X-ray scattering (WAXS) on a Nano-inXider® instrument under the following conditions: - Wavelength: Mainly copper Kα1 line (1.54 angstroms) - Output: 50kV~0.6mA - Observation mode: Transmittance - Counting time: 10 minutes

[0050] This gives a spectrum of the scattering intensity as a function of the diffraction angle, which makes it possible to identify the presence of crystals if peaks are seen in the spectrum in addition to the amorphous halo.

[0051] In the spectrum, it is possible to measure the area of ​​the crystalline peak (designated CA) and the area of ​​the amorphous halo (designated AH). The mass fraction of crystalline PEKK in PEKK is then estimated using (CA) / (CA+AH).

[0052] The phrase "isothermal crystallization half-time", expressed as "t1 / 2" at the measured temperature, is understood to mean the time required to reach a relative crystallinity of 0.5 for isothermal crystallization at the measured temperature, as defined according to standard ISO 11357-7:2015.

[0053] According to this standard, isothermal crystallization conditions are carried out by a first step of melting the sample, followed by a step of cooling as quickly as possible to the selected measurement temperature, so that crystallization begins after the end of the cooling step. The time at which the isothermal step is completed, i.e. the time required to obtain a complete crystallization curve, depends on the crystallization rate. If the DSC curve is not clear, this time is determined to be five times the time required to reach the maximum crystallization rate.

[0054] The term "mixture of polymers" is understood to denote a macroscopically homogeneous composition of polymers. The term includes mixtures of compatible and / or miscible polymers, mixtures having intermediate glass transition temperatures relative to the glass transition temperatures of the polymers considered individually. The term also includes such compositions consisting of immiscible phases dispersed on a micrometer scale.

[0055] The term "copolymer" is intended to denote a polymer resulting from the copolymerization of at least two chemically distinct monomers, called comonomers. Thus, a copolymer is formed from at least two repeat units. It can also be formed from three or more repeat units.

[0056] The acronym "PAEK" stands for "polyaryletherketone", "PAEKs" stands for "polyaryletherketone(s)", and "PAEK(s)" stands for "polyaryletherketone or polyaryletherketone(s)".

[0057] In all ranges set out in this patent application, endpoints are included unless otherwise stated.

[0058] Pseudo-amorphous compositions based on polyaryletherketones The polyaryletherketone-based compositions in sheet form for the process according to the invention are quasi-amorphous.

[0059] The essentially amorphous nature of the composition allows for good fusion of the peripheral areas of the sheets that are brought into contact in the twin-sheet thermoforming process, which is why the at least one polyaryletherketone, or the composition comprising it, advantageously has a crystallinity of 5.0% or less, or 3.0% or less, or 1.0% or less, and ideally about 0%.

[0060] The composition has a T that is slow enough to allow the sheet to form in a quasi-amorphous state. f From T gIt is necessary to have a crystallization rate at a temperature between

[0061] The composition also has a T that is slow enough to remain essentially amorphous during the softening step and until the contacting step. f From T g It is necessary for the crystallization rate to be between 0.1 and 1.

[0062] On the other hand, the composition has a T fast enough to crystallize within a reasonable time scale after the contact and fusion step. f From T g It is necessary for the crystallization rate to be between 0.1 and 1.

[0063] Advantageously, the isothermal crystallization half time of the composition at the softening temperature and / or at the contact temperature may be at least 3 seconds and at most 30 minutes.

[0064] The isothermal crystallization half time of the composition at the softening temperature and / or contact temperature may preferably be at least 5 seconds, more preferably at least 8 seconds.

[0065] The isothermal crystallization half time of the composition at the softening temperature and / or contact temperature may preferably be at most 10 minutes, more preferably at most 5 minutes, and most preferably at most 2 minutes.

[0066] Advantageously, the viscosity of the composition at 380° C. and 1 Hz, measured with a parallel plate rheometer of 25 mm diameter under nitrogen purge, has a value of from 200 Pa.s to 8000 Pa.s, preferably from 500 Pa.s to 5000 Pa.s, more preferably from 750 Pa.s to 4500 Pa.s.

[0067] These viscosity ranges are particularly advantageous for obtaining a sheet with good strength and a substantially uniform thickness during extrusion of the sheet, adequate creep resistance during the process of forming the softened sheet, and finally allowing good fusing during the process of contacting and fusing the two sheets together.

[0068] In particular, the composition may have a viscosity having a value of from 750 Pa.s to 1200 Pa.s, or from 1200 Pa.s to 1600 Pa.s, or from 1600 Pa.s to 2000 Pa.s, or from 2000 Pa.s to 2400 Pa.s, or from 2400 Pa.s to 2800 Pa.s, or from 2800 Pa.s to 3200 Pa.s, or from 3200 Pa.s to 3600 Pa.s, or from 3600 Pa.s to 4000 Pa.s, or from 4000 Pa.s to 4250 Pa.s, or from 4250 Pa.s to 4500 Pa.s.

[0069] The composition preferably has a glass transition temperature T of 125° C. or more, more preferably 145° C. or more, and most preferably 150° C. or more. g has.

[0070] The composition preferably has a melting temperature T f The composition may in particular have a melting temperature of 280° C. or more, or 290° C. or more, or 300° C. or more, or 310° C. or more, or 320° C. or more, or even 330° C. or more.

[0071] The composition comprises at least 50% by weight of at least one polyaryletherketone, which is interchangeably referred to as a polyaryletherketone-based composition in other parts of this application.

[0072] Polyaryletherketone (PAEK) has the following formula: (-Ar-X-) and (-Ar1-Y-) (In the formula, each of Ar and Ar1 represents a divalent aromatic group; Ar and Ar1 may preferably be selected from 1,3-phenylene, 1,4-phenylene, 1,1'-biphenylene divalent in the 3,3' positions, 1,1'-biphenyl divalent in the 3,4' positions, 1,4-naphthylene, 1,5-naphthylene and 2,6-naphthylene; X represents an electron-withdrawing group, which may preferably be chosen from the carbonyl and sulfonyl groups, - Y represents an oxygen atom, a sulfur atom, an alkylene group, such as a group selected from -(CH)2- and isopropylidene. Includes units of.

[0073] In these X and Y units, at least 50%, preferably at least 70%, more particularly at least 80% of the X groups are carbonyl groups and at least 50%, preferably at least 70%, more particularly at least 80% of the Y groups represent oxygen atoms.

[0074] According to a preferred embodiment, 100% of the X groups represent a carbonyl group and 100% of the Y groups represent an oxygen atom.

[0075] The mass of the PAEK, or, where appropriate, the sum of the masses of the PAEKs of the composition, may represent at least 60%, or at least 70%, or at least 80%, or at least 85%, or at least 90%, or at least 92.5%, or at least 95%, or at least 99%, or at least 99.9%, or 100% of the total mass of the composition.

[0076] In certain embodiments, the composition consists essentially of PAEK(s), i.e., comprises PAEK(s) at 90% to 99.9% of the total weight of the composition.

[0077] In some embodiments, the composition consists of PAEK(s), ie, at least 99.9%, ideally 100%, of the total mass of the composition consists of PAEK(s).

[0078] Advantageously, the PAEK(s) is - polyetherketoneketone, also known as PEKK, which contains one or more units of the formula -Ph-O-Ph-C(O)-Ph-C(O)-, Polyetheretherketone, also known as PEEK, which contains one or more units of the formula -Ph-O-Ph-O-Ph-C(O)-, - polyetherketone, also known as PEK, which contains one or more units of the formula -Ph-O-Ph-C(O)-; - polyetheretherketoneketone, also known as PEEKK, which contains one or more units of the formula -Ph-O-Ph-O-Ph-C(O)-Ph-C(O)-, - polyetheretheretherketone, also known as PEEEK, which contains one or more units of the formula -Ph-O-Ph-O-Ph-O-Ph-C(O)-; - polyether diphenyl ether ketone, also known as PEDEK, which contains one or more units of the formula -Ph-O-Ph-Ph-O-Ph-C(O)-, - mixtures thereof, and - a copolymer comprising at least two of the abovementioned units (wherein Ph represents a phenylene group, -C(O)- represents a carbonyl group, and each phenylene can be independently ortho (1,2), meta (1,3) or para (1,4), and preferably meta or para.)

[0079] Additionally, defects, end groups and / or monomers may be incorporated into polymers such as those listed above in very small amounts, without affecting their performance.

[0080] According to some embodiments, the composition comprises, consists essentially of, or even consists of a polyetherketoneketone polymer comprising terephthalic units and isophthalic units, the terephthalic units being represented by the formula:

[0081] [ka]

[0082] and the isophthalic acid unit has the formula

[0083] [ka]

[0084] has.

[0085] For a polymer of a given family, for example the PEKK family, "comprising one or more units" means that this / these units have a total molar ratio of at least 50% in the polymer. This / these units can represent at least 60%, or at least 70%, or at least 80%, or at least 85%, or at least 90%, or at least 92.5%, or at least 95%, or at least 99%, or at least 99.9% in the polymer. The phrase "consisting essentially of units" means that the units represent a molar ratio of 95% to 99.9% in the copolymer. Finally, the term "consisting of units" is understood to mean that the units represent a molar ratio of at least 99.9% in the polymer.

[0086] Preferably, the polyetherketoneketone consists essentially of, or even consists of, isophthalic acid "I" units and terephthalic acid "T" units.

[0087] Preferably, the polyetherketoneketone is optionally a random copolymer.

[0088] Selection of the molar ratio of T units to the sum of T units and I units is one of the factors that allows for tuning of the crystallization kinetics properties of the polyetherketoneketone.

[0089] A given molar ratio of T units to the sum of T and I units can be obtained in a manner known per se by adjusting the respective concentrations of the reactants during the polymerization.

[0090] The molar ratio of T units to the sum of T and I units of the PEKK can in particular range from 0% to 5%, or 5% to 10%, or 10% to 15%, or 15% to 20%, or 20% to 25%, or 25% to 30%, or 30% to 35%, or 35% to 40%, or 40% to 45%, or 45% to 48%, or 48% to 51%, or 51% to 54%, or 54% to 58%, or 58% to 62%, or 62% to 65%, or 65% to 68%, or 68% to 73%, or 73% to 75%, or 75% to 78%, or 78% to 80%, or 80% to 85%.

[0091] According to a particular embodiment, the polyetherketoneketone essentially consists or even consists of "T" and "I" units, with a molar ratio of T units to the sum of T units and I units ranging from 0% to 5%, or from 35% to 78%. Indeed, for this range of molar ratios, the polyetherketoneketone has an adequate crystallization rate, on the one hand allowing it to be obtained in essentially amorphous form by sufficiently fast cooling, and to crystallize sufficiently fast when heated above its glass transition temperature. These molar ratios of units T to the sum of units T and I are therefore particularly suitable for compositions essentially consisting or even consisting of a single polyetherketoneketone. The molar ratio of T units to the sum of T units and I units can preferably be 0% to 5%, or 35% to 78%, preferably 45% to 75%, more preferably 48% to 52%, or 65% to 74%. The molar ratio of T units to the sum of T units and I units can in particular be about 50% or about 70%.

[0092] The composition preferably has the formula

[0093] [ka]

[0094] The polyether ketone ketone homopolymer does not consist of a single repeating unit of the above.

[0095] In fact, this polymer crystallizes very rapidly when heated above its Tg, making it very difficult to mold thick pseudo-amorphous sheets, and also very difficult to mold such sheets in an essentially amorphous state. Moreover, due to its very rapid crystallization, this polymer does not make it possible to obtain good fusion between the sheets, resulting in poor adhesion in the contact areas.

[0096] Based on this observation, it is nevertheless possible to consider reducing the crystallization rate of the homopolymers described above in various ways.

[0097] The first aspect is the introduction of a certain number of defects in the structure of the homopolymer consisting of units of formula (III), ie the modification of its chemical structure.

[0098] The composition has the formula

[0099] [ka]

[0100] Units and formulas

[0101] [ka]

[0102] The polymer may comprise, consist essentially of, or even consist of a polymer comprising units of

[0103] Preferentially, the polymer consists essentially of, or even actually consists of, units of formula (III) and units of formula (IV).

[0104] Preferentially, the polymer is optionally a random copolymer.

[0105] The molar ratio of units (III) to the sum of units (III) and units (IV) can range from 0% to 99%, preferably from 5% to 95%, more preferably from 10% to 50%, and most preferably from 20% to 40%.

[0106] According to some variations, the composition has the formula

[0107] [ka]

[0108] Units and formulas

[0109] [ka]

[0110] The polymer may comprise, consist essentially of, or even consist of a polymer comprising, consisting essentially of, or even consisting of units of:

[0111] Preferentially, the polymer consists essentially of, or even actually consists of, units of formula (III) and units of formula (IVa).

[0112] Preferentially, the polymer is optionally a random copolymer.

[0113] The molar ratio of units (III) to the sum of units (III) and units (IVa) can range from 0% to 99%, preferably from 5% to 95%.

[0114] The composition has the formula

[0115] [ka]

[0116] Units and formulas

[0117] [ka]

[0118] The polymer may comprise, consist essentially of, or even consist of a polymer comprising units of

[0119] Preferably, the polymer consists essentially of, or even consists of, units of formula (III) and units of formula (V).

[0120] Preferentially, the polymer is optionally a random copolymer.

[0121] The molar ratio of units (III) to the sum of units (III) and units (V) can range from 0% to 99%, preferably from 0% to 95%.

[0122] According to some variations, the composition has the formula

[0123] [ka]

[0124] Units and formulas

[0125] [ka]

[0126] The polymer may comprise, consist essentially of, or even consist of a polymer comprising, consisting essentially of, or even consisting of units of:

[0127] Preferably, the polymer consists essentially of, or even consists of, units of formula (III) and units of formula (Va).

[0128] Preferentially, the polymer is optionally a random copolymer.

[0129] The molar ratio of units (III) to the sum of units (III) and units (Va) can range from 0% to 99%, preferably from 0% to 95%.

[0130] A second way to reduce the crystallization of a homopolymer consisting of recurring units of formula (III) is to mix it with another PAEK that takes longer to crystallize, which may in particular be a PEKK consisting essentially, preferably consisting of, units I and / or T, or alternatively a copolymer comprising recurring units of formula (III), in particular those indicated above.

[0131] A third way to decrease the crystallization rate of a PEEK homopolymer consisting of repeating units of formula (III) is to mix it with another polymer different from PAEK, particularly an amorphous polymer. One amorphous polymer that is compatible with many PAEKs, particularly PEKK or PEEK, is, for example, polyetherimide.

[0132] A fourth aspect of reducing the crystallization of PEEK homopolymers consisting of repeating units of formula (III), which will not be developed in detail here, would be the addition of additives that act as agents for adjusting the crystallization rate.

[0133] According to some particular embodiments, the composition comprises, in particular: - PEKK consisting essentially of or consisting of I and T units, in particular as described above; - polymers consisting essentially of or consisting of units of formula (III) and units of formula (IV) as described above, - consisting essentially of or consisting of a single PAEK selected from polymers consisting essentially of or consisting of units of formula (III) and units of formula (V) as described above.

[0134] According to some embodiments, the composition comprises, consists essentially of, or consists of a single PAEK of substantially homogeneous composition and / or viscosity.

[0135] According to some embodiments, the composition comprises, consists essentially of, or consists of several different PAEKs, ie, particularly those having different chemical compositions and / or different viscosities.

[0136] According to some particular embodiments, the composition comprises at least two PAEKs of different chemical composition, more particularly: - PEKK which essentially consists of or consists of I and T units, in particular as described above, and in addition to said PEKK, - comprising at least one of the following polymers: PEK, PEEKEK, PEEK, in particular a polymer essentially consisting of or consisting of units of formula (III) and units of formula (V) as described above, PEEKK, PEKEKK, PEEEK, PEDEK or a polymer essentially consisting of or consisting of units of formula (III) and units of formula (IV) as described above, in a content of less than 50% by weight of the total weight of the composition, preferably less than or equal to 30% by weight of the composition.

[0137] According to some particular embodiments, the composition comprises a mixture of several PAEKs, which are copolymers of PAEKs with different molar ratios of repeating units. In particular, the composition can comprise a mixture of PEKK copolymers with different molar ratios of "T-type" units to the sum of "T-type" and "I-type" units.

[0138] According to some particular embodiments, the composition may also comprise a mixture of several PAEKs, the PAEKs being copolymers of PAEKs with different viscosities.

[0139] Finally, the composition may also include PAEKs, which are copolymers of PAEKs having different molar ratios of repeat units and viscosities.

[0140] According to some embodiments, the composition may also comprise one or more other polymers not belonging to the family of PAEKs, in particular other thermoplastic polymers.

[0141] According to some embodiments, the composition may comprise a mixture of at least one fluoropolymer, such as those described in EP 2767986 and US 9,543,058, and PAEK(s). The fluoropolymer may preferentially be selected from the list consisting of polytetrafluoroethylene (PTFE), poly(vinyl fluoride) (PVF), poly(vinylidene fluoride) (PVDF), polychlorotrifluoroethylene (PCTFE), perfluoroalkoxy polymers, perfluoroalkoxy-alkane copolymers (PFA), fluorinated ethylene-propylene copolymers (FEP), poly(ethylene-co-tetrafluoroethylene) (ETFE), polyethylene chlorotrifluoroethylene (ECTFE), perfluoroelastomers (FFKM), perfluoropolyethers (PFPE), and mixtures thereof.

[0142] Since fluoropolymers are normally immiscible with PAEKs, the composition in these embodiments is advantageously a dispersion of particles comprised of fluoropolymer in said at least one PAEK.

[0143] In some embodiments, the composition comprises a mixture of PAEK(s) and polyetherimide (PEI), a silicone-polyimide copolymer or alternatively a polysiloxane / polyimide (e.g., polyetherimide / polydimethylsiloxane (PEI / PDMS)) block copolymer, such as those polymers described in EP 0323142 and U.S. Pat. No. 8,013,251.

[0144] According to some embodiments, the composition may include, instead of or in addition to the thermoplastics mentioned above, polyphenylene sulfone (PPSU), polysulfone (PSU), polycarbonate (PC), polyphenylene ether (PPE), poly(phenylene sulfide) (PPS), poly(ethylene terephthalate) (PET), polyamide (PA), polybenzimidazole (PBI), poly(amide-imide) (PAI), poly(ether sulfone) (PES), poly(arylsulfone), poly(etherimide sulfone), polyphenylene, polybenzoxazole, polybenzothiazole, or mixtures thereof.

[0145] According to some particular embodiments, the composition comprises: - a PAEK selected in particular from a PEKK consisting essentially of or consisting of units I and units T as described above, a polymer consisting essentially of or consisting of units of formula (III) and units of formula (IV) as described above, and a polymer consisting essentially of or consisting of units of formula (III) and units of formula (V) as described above, - consisting essentially of or in a mixture with another polymer selected from the list consisting of FEP, PFA, FFKM, PEI, PEI / PDMS, PES, PSU, PPSU, PPS, PPE, and mixtures thereof.

[0146] In particular, the composition comprises: - PEKK consisting essentially of or consisting of I and T units, with a molar ratio of T units to the sum of T and I units ranging from 45% to 75%; - may consist essentially of or consist of a mixture with another polymer selected from the list consisting of FEP, PFA, FFKM, PEI, PEI / PDMS, PES, PSU, PPSU, PPS, PPE, and mixtures thereof.

[0147] According to some embodiments, the composition may further comprise fillers and / or additives.

[0148] Among the fillers, mention may be made of mainly reinforcing fillers, either fibrous or non-fibrous. The non-fibrous fillers may in particular be titanium dioxide, talc or calcium carbonate. The fibrous fillers may in particular be glass fibres and carbon fibres, which may be ground or not.

[0149] Among the fillers, mention may be made mainly of thermally conductive fillers, and in particular fillers which may be selected from the list consisting of ceramics, such as boron nitride or aluminium oxide, metals, such as copper, stainless steel, aluminium, gold, silver, carbon fillers, such as carbon black, carbon nanotubes, graphite, inorganic fillers, such as hematite, or mixtures thereof.

[0150] Thus, the composition may comprise less than 50% by weight of filler, preferably less than 40% by weight of filler, more preferably less than 25% by weight of filler, based on the total weight of the composition.

[0151] The additives include stabilizers (light, especially UV, and heat, e.g., phosphates), optical brighteners, dyes, pigments, flow agents, additives for adjusting the melt viscosity of the composition, additives for adjusting the crystallization rate of the composition, additives for adjusting the heat capacity of the composition, or combinations of these additives. Thus, the composition may contain less than 10% by weight, preferably less than 5% by weight, and even more preferably less than 1% by weight of additives, based on the total weight of the composition.

[0152] A sheet comprising a composition on at least one surface thereof A sheet is typically a flat or substantially planar, three-dimensional article having a thickness significantly less than both its length and its width. In particular, a sheet can have a thickness less than 10%, or less than 5%, of both its length and its width.

[0153] The sheets may be non-porous, porous, microporous, etc., depending on the intended application and use.

[0154] According to some embodiments, the sheet may be made of a polyaryletherketone based pseudo-amorphous composition.

[0155] According to some embodiments, the sheet can be formed with multiple layers, i.e. at least two layers, each layer possibly having a different chemical composition independently of the other, in this embodiment, the polyaryletherketone-based composition is then used to form a layer on the outer surface of the multiple layers, i.e. on at least one of the two faces of the sheet.

[0156] According to some embodiments, each sheet may consist of two layers: one advantageous example of a twin sheet is a sheet consisting of a first PEKK layer made of repeating T:I units with a T:I molar ratio of about 70:30, and a second PEKK layer made of repeating T:I units with a T:I molar ratio of about 60:40, with the PEKK being advantageously used to constitute the inner surface of the sheet.

[0157] The thickness of the sheet can be measured, for example, using a standard micrometer.

[0158] The sheet or, if desired, the layer of the polyaryletherketone-based composition may have a thickness ranging in particular from 200 microns to 20.00 millimeters. Preferably, the sheet has a thickness ranging from 500 microns to 10.00 millimeters.

[0159] According to a particular embodiment, the sheet or, optionally, the layer of the polyaryletherketone-based composition has a thickness equal to a value ranging from 500 microns to 1000 microns, or a value ranging from 1.00 millimeters to 2.00 millimeters, or a value ranging from 2.00 millimeters to 3.00 millimeters, or a value ranging from 3.00 millimeters to 4.00 millimeters, or a value ranging from 4.00 millimeters to 5.00 millimeters, or a value ranging from 6.00 millimeters to 7.00 millimeters, or a value ranging from 8.00 millimeters to 9.00 millimeters, or a value ranging from 9.00 millimeters to 10.00 millimeters.

[0160] Typically, the thickness of the sheet is substantially uniform, that is, the thickness can vary by no more than about 10%, preferably no more than about 5%, from one location on the sheet to another.

[0161] The sheet or, optionally, the layer made of the polyaryletherketone-based composition is - heating the polyaryletherketone-based composition to a suitable temperature above its melting temperature to obtain a molten resin composition; - forming the molten resin composition into a sheet; and It can be produced by a method known per se, which includes a step of cooling the sheet at a rate fast enough to obtain a sheet in a quasi-amorphous state.

[0162] In some embodiments, the sheet used in the present invention can be produced by melt extrusion. The extrusion temperature depends on the melt temperature of the polymer (in the case of PEKK, this is influenced by its T:I ratio) and also on its melt viscosity. For example, when the ratio of T:I isomers in PEKK is 70:30 or 50:50, the preferred extrusion temperature is between about 350°C and about 380°C. In general, an extrusion temperature that is about 5°C to about 70°C, or about 10°C to about 50°C higher than the melt temperature of the composition is suitable.

[0163] The extruded sheet is conveyed directly from the die to a smooth metal or textured cylinder, commonly known as a "cooling cylinder" because the surface temperature of these cylinders is maintained below the melting temperature of the polymer. A stream of air or other gas may also be directed at the extruded sheet to facilitate its cooling. The rate at which the sheet is cooled and solidified (called the cooling rate) is an important aspect in obtaining a quasi-amorphous sheet structure. The cooling rate is primarily determined by the temperature of the cooling cylinder, the thickness of the sheet, and the line speed. It must be fast enough to obtain the sheet in a quasi-amorphous state.

[0164] Twin Sheet Thermoforming Method FIG. 1 illustrates an apparatus 1 adapted for the twin-sheet thermoforming process according to the present invention, and in particular the process described in the block diagram of FIG.

[0165] 1, the device 1 comprises a frame 20 including fastening means 21 to which two sheets 10 can be fastened. The two sheets 10 are initially substantially parallel to each other and separated by a space 60 between the sheets.

[0166] Each sheet 10 includes an inner surface 11 made of a polyaryletherketone-based pseudo-amorphous composition. The inner surfaces 11 of the two sheets 10 face each other and can be brought into contact with each other at least partially in contact area 12 during the contacting and fusing process.

[0167] The apparatus 1 also comprises two mould halves 30, the shape of which includes walls 31 adapted to the desired final shape of the hollow body to be produced.

[0168] Each of the mold halves 30 may be flat, male or female in shape, independent of the other.

[0169] According to an advantageous embodiment, one of the two mould halves is female. The other mould halves may be flat, male or female. The other mould halves may in particular be flat or female.

[0170] The mold halves 30 are movable (in the direction of the arrows) from an open position (FIG. 1) spaced apart from one another to a closed position (not shown) such that the walls 31 form a cavity. It is this cavity that gives the manufactured article its "hollow body" character.

[0171] The outer surfaces 13 of the two sheets 10 face the respective mould halves 30. They are able to come into contact, in the clamping area 14, with the parts 32 of the mould halves 30 which are intended to be clamped together to secure closure.

[0172] The portions 32 of the mold halves 30 may be flat or, on the contrary, may have a shape making it possible to increase the contact surface of the pinch area 14 .

[0173] Each mold half 30 can include holes 33 that allow gas to escape during at least the forming process. These holes 33 can advantageously be connected to gas exhaust pipes 40 by which a vacuum can be drawn, allowing the sheet 10 to be at least partially formed. Alternatively and / or in addition, the sheet can be at least partially formed by injecting pressurized gas using gas injection pipes 50 that can be at least temporarily inserted into the spaces 60 between the sheets. The gas can optionally be heated, so that the sheet 10 maintains a temperature sufficiently close to its softening temperature during the forming process.

[0174] Each sheet can be heated on its outer side 13 and / or its inner side 11 using heating means by radiation, convection or conduction, making it possible to soften it. Heating can be carried out, for example, using infrared lamps and / or by blowing hot air and / or in an oven. The heating means are arranged so that each sheet softens as uniformly as possible.

[0175] According to one embodiment shown in Figure 1, heating means 70 can be arranged in the space 60 between the sheets, making it possible to heat the inner faces 11 of the two sheets 10 during the softening process. Furthermore (not shown in the schematic diagram of Figure 1), further heating means can be used, at least temporarily, to heat the outer faces of the sheets 10. This is particularly necessary if the sheets are very thick.

[0176] Still further (not shown in the schematic diagram of FIG. 1), additional heating means may be used to heat the contact area 12 of at least one or both sheets 10 in embodiments where the contact temperature is higher than the softening temperature. According to some embodiments, this complementary heating mode may be performed by conduction by contacting a mold half part 32 with the nip area 14 of one of the two sheets 10 for a sufficient time. These complementary heating means are provided such that the nip area 14 has as uniform a temperature as possible.

[0177] The apparatus according to FIG. 1 is particularly suitable for carrying out a twin-sheet thermoforming method 100 according to the method whose block diagram is shown in FIG.

[0178] Referring to FIG. 2, the method 100 includes providing two sheets 10 including at least one surface 11 comprised of a polyaryletherketone-based pseudo-amorphous composition.

[0179] The method 100 includes a step 105 of softening each of the sheets at a softening temperature to form a softened sheet 110 .

[0180] The softening temperature is sometimes otherwise called the "thermoforming temperature."

[0181] The softening temperature is equal to or greater than the glass transition temperature of each of the quasi-amorphous compositions.

[0182] In embodiments where the sheets have different compositions, the softening temperature may be different for each sheet, whereas in embodiments where the sheets have similar compositions, the softening temperature for each sheet may be similar.

[0183] The softening temperature can be measured using a thermocouple near the inner surface 11 of the sheet 10 (outside the contact area 12).

[0184] The softening temperature is usually strictly defined as T g Higher (T g The softening temperature preferably has a value of not more than (T g +10)℃~(T g +75) °C.

[0185] According to some embodiments, the softening temperature may be from (Tg+15)°C to (Tg+65)°C, or from (Tg+20)°C to (Tg+60)°C.

[0186] Advantageously, the softening temperature is substantially homogeneous over the entire inner surface 11 of each sheet 10, except possibly in the contact area 12 and adjacent areas, if a contact temperature different from the softening temperature is applied.

[0187] For example, for a PEKK consisting essentially of or consisting of repeat units T and I, with a molar ratio T:I equal to about 70%, the softening temperature can be between 175° C. and 225° C. If the softening temperature is equal to the contact temperature of the contact area, a temperature between 195° C. and 215° C. can be advantageously selected.

[0188] Once the sheets 10 have reached their softening temperature, the heating elements 70 can be withdrawn from the spaces 60 between the sheets.

[0189] The method 100 includes a step 115 of shaping the softened sheet 110. Shaping can be done, inter alia, by blowing pressurized gas onto the inner surface 11 and / or by sucking air from the outer surface 13.

[0190] For example, a pressure of 1 to 6 bar, preferably 1.2 to 5 bar, may be applied to the inner surface 11 and / or the outer surface 13 may be subjected to a vacuum of 0.001 to 0.9 bar, preferably 0.05 to 0.85 bar.

[0191] The method 100 includes a step 125 of contacting and fusing at least one contact area 12 of said faces 11 of the softened sheets to form an intermediate body 130. For the contacting and fusing step, the contact areas 12 are heated to a contact temperature, and each contact area 12 remains essentially in an amorphous state at least until contact. The contacting step is performed by joining the mold halves 30 so that the mold half portions 32 first contact the sheets 10 at the pinch area 14, and then bringing the two sheets 10 into contact at their contact areas 12. The fusing of the two sheets 10 is made possible by the fact that the composition of the inner faces 11 that constitute them is essentially in an amorphous state when the contact areas 12 are brought into contact.

[0192] The contact temperature can be measured using a thermocouple near the contact area 12 of the sheet 10 .

[0193] The contact temperature is usually equal to or higher than the softening temperature.

[0194] The contact temperature is usually below the mold temperature.

[0195] According to some embodiments, the contact temperature can be approximately equal to the softening temperature.

[0196] According to some embodiments, the contact temperature can be approximately equal to the mold temperature.

[0197] According to some embodiments, the contact temperature can be several degrees Celsius or even tens of degrees Celsius above the softening temperature.

[0198] The contact temperature may in particular be at least 5° C., or at least 10° C., or at least 15° C. above the softening temperature.

[0199] The contact temperature may in particular be at most 75°C, or at most 60°C, or at most 50°C, or at most 45°C, or at most 40°C, or at most 35°C, or at most 30°C, or at most 25°C, or at most 20°C higher than the softening temperature.

[0200] According to some embodiments, the contact temperature can be several degrees Celsius or even tens of degrees Celsius lower than the mold temperature. These embodiments are particularly practiced when portions 32 of mold halves 30 are brought into contact at pinch area 14 for a sufficient time prior to the contacting and fusing step of contact areas 12 of sheets 10.

[0201] The contact temperature may in particular be at most 5° C., or at most 10° C., or at most 15° C. lower than the mold temperature.

[0202] A clamping pressure can be applied to the two mould halves 30 to facilitate the fusion of the contact areas 12. According to some embodiments, the clamping pressure is between 1 bar and 50 bar. The clamping pressure can be preferably between 5 bar and 40 bar, even more preferably between 7 bar and 30 bar. The clamping pressure can be adapted by providing an air gap between the two mould halves.

[0203] Finally, the method 100 includes a step 135 of crystallizing the polyaryletherketone-based composition at a mold temperature to form a crystallized hollow body 140 after the contacting and fusing step 115 and the molding step 125 to form a crystallized hollow body.

[0204] The mold can be brought to as uniform a mold temperature as possible, preferably by using suitable mold heating means, for example an electric heating device.

[0205] The mold temperature may advantageously be close to the temperature at which the composition exhibits a minimum isothermal crystallization half-time.

[0206] According to some embodiments, the mold temperature (T g +T f The mold temperature can be close to (T g +Tf ) / 2 by 35° C. or by 25° C. or by 15° C. or by 10° C. or by less than (T g +T f ) / 2 by 45°C or more, or 35°C or more, or 25°C or more, or 20°C or more.

[0207] For example, for PEKK consisting essentially of or consisting of repeat units T and I, with a T:I molar ratio equal to about 70%, the mold temperature can be from 210°C to 270°C, preferably from 220°C to 260°C, and more preferably from 225°C to 255°C.

[0208] Advantageously, the difference between the softening temperature and the mold temperature may be less than or equal to 60° C. to avoid any sagging. The difference between the softening temperature and the mold temperature may in particular be less than or equal to 50° C., or less than or equal to 40° C.

[0209] Also advantageously, the difference between the softening temperature and the mould temperature may be 15° C. or more, or 20° C. or more, or even 25° C. or more.

[0210] The duration of the crystallization step may depend on the thickness of the sheet, the mold temperature, the shape of the mold, and the desired degree of crystallinity. For example, for a PEKK consisting essentially of or consisting of repeat units T and I, with a molar ratio T:I equal to about 70%, this duration may be from 1 to 30 minutes, preferably from 2 to 15 minutes, more preferably from 3 to 10 minutes.

[0211] According to some embodiments, a sufficiently long heating of the contact area makes it possible to achieve an average crystallinity measured by WAXS strictly greater than 7%. Preferably, it makes it possible to achieve a crystallinity of 10% or more, or 15% or more, or 20% or more, or even 25% or more.

[0212] Although the block diagram of FIG. 2 depicts sequential steps, some of these steps may in fact overlap and / or occur simultaneously or even in different orders.

[0213] According to some embodiments, the forming step 115 of the sheet 10 can begin before the contacting and fusing step 125 by starting the air blowing and / or vacuum before the contact areas 12 are brought into contact. According to these embodiments, the forming step 115 can be performed such that it is completed before, at the same time as, or after the contacting and fusing step.

[0214] According to certain embodiments, the forming step 115 can be completed before the contacting and fusing step 125. This is especially the case when the sheets are formed one by one and then brought into contact with each other.

[0215] According to some embodiments, the molding step 115 may be completed at about the same time as the contacting and fusing step 125 .

[0216] According to some embodiments (not shown in FIG. 2), a molding step can occur essentially after the contacting and fusing steps.

[0217] Although the crystallization step may begin to some extent prior to the end of the contacting step and / or prior to the end of the forming step, it is necessary for the practice of the invention that the composition be in an essentially amorphous state in order to contact and fuse the contact areas of the sheets. It is also advantageous for the forming step to be carried out with an essentially amorphous composition.

[0218] The hollow bodies which can be used according to the invention are numerous and may have more or less complex shapes. Among the possible hollow bodies, mention may be made in particular of "container" type objects or of the "casing" or "case" type objects. EXAMPLES

[0219] Example 1 A hollow body was manufactured using an apparatus as illustrated in FIG. 1 according to a method according to the block diagram of FIG.

[0220] Two amorphous sheets, 2.3 millimeters thick, of polyetherketoneketone consisting of T and I units in a molar ratio of 70:30 and having a viscosity of 3906 Pa.s at 380° C. and 1 Hz are used.

[0221] For the softening step, the inner surfaces of the sheets are heated to a softening temperature of 210° C. No additional heating means are used to heat the contact area between the sheets.

[0222] The two mould halves are closed with a clamping pressure of 10 bar.

[0223] The two sheets are thermoformed and maintained for about 5 minutes in a mold heated to a temperature of 240° C. The mold is then opened by removing one of the two mold halves and the hot hollow body is cooled by a jet of air.

[0224] The resulting hollow bodies are opaque in appearance, which means that they are crystallized.

[0225] Example 2 The same sheet as used in Example 1 was used to manufacture a hollow body.

[0226] In the softening process, the inner surface of the sheet is heated to a softening temperature of 200°C. The contact area is heated to a temperature of 220°C.

[0227] The two mould halves are closed with a clamping pressure of 10 bar.

[0228] The two sheets are thermoformed and maintained for about 5 minutes in a mold heated to a temperature of 240° C. The mold is then opened by removing one of the two mold halves and the hot hollow body is cooled by a jet of air.

[0229] The resulting hollow bodies are opaque in appearance, which means that they are crystallized. [Explanation of symbols]

[0230] 1 device 10 Sheets 11 Inner surface 12 Contact area 13 External surface 14 Pinching area 20 slots 21 Fixing means 30 half mold 31 Wall 32 parts 33 holes 40 Gas exhaust pipe 50 Gas injection pipe 60 Space between seats 70 Heating element 100 Twin Sheet Thermoforming Method 105 Softening process 110 Softening Sheet 115 Molding process 120 Thermoforming Sheet 125 Contact and Fusion Process 130 Intermediates 135 Crystallization process 140 Crystallized Hollow Body

Claims

1. A twin-sheet thermoforming method (100) for producing a hollow body (140), said method comprising: Providing two sheets (10) each having at least one surface (11) made of a polyaryletherketone-based pseudo-amorphous composition; Step (105) of softening the two sheets (10) at a softening temperature to form a softened sheet (110), the softening temperature being equal to or higher than the glass transition temperature of each of the pseudo-amorphous compositions; A step (115) of forming the softened sheet (110) to form a thermoformed sheet (120); a step (125) of contacting and fusing at least one contact area (12) of the softened sheet and / or the surface (11) of the to-be-formed or already-formed sheet to form an intermediate body (130), wherein the contact areas (12) are heated to a contact temperature and remain in an essentially amorphous state at least until the respective contact areas come into contact; and A step (135) of crystallizing the composition at a mold temperature to form a crystallized hollow body (140), A twin-sheet thermoforming process (100) wherein the crystallization step (135) occurs after the contacting and fusing step (125).

2. 10. The twin-sheet thermoforming process of claim 1, wherein the composition has a viscosity at 380°C, 1 Hz, measured by a parallel plate rheometer, ranging from 200 Pa.s to 8000 Pa.s.

3. 3. The thermoforming method according to claim 1 or 2, wherein the isothermal half-time at the contact temperature is at least 3 seconds and / or the isothermal half-time at the contact temperature is 30 minutes or less.

4. 10. The twin-sheet thermoforming method of claim 1, wherein the at least one polyaryletherketone is a polyetherketoneketone.

5. The at least one polyaryletherketone has the formula 【Chemical 1】 The repeating unit and chemical formula 【Chemistry 2】 is a copolymer consisting essentially of or consisting of repeat units of 2. The twin-sheet thermoforming method according to claim 1, wherein the molar percentage of the unit (III) relative to the total of the unit (III) and the unit (IV) is 0% to 99%.

6. The at least one polyaryletherketone is represented by the formula 【Chemistry 3】 and repeating units having the formula 【Chemistry 4】 and a copolymer consisting essentially of or consisting of repeat units having the formula:

2. The twin-sheet thermoforming method according to claim 1, wherein the molar percentage of the units (III) relative to the total of the units (III) and the units (V) is 0% to 99%.

7. 10. The twin-sheet thermoforming method of claim 1, wherein the composition comprises polyaryletherketone.

8. 2. The twin-sheet thermoforming method of claim 1, wherein each sheet, independently or independently, comprises a polyaryletherketone-based quasi-amorphous composition.

9. 10. The twin-sheet thermoforming method of claim 1, wherein the two sheets, independent or not, have a thickness of 200 microns to 20 millimeters.

10. 10. The twin-sheet thermoforming process of claim 1, wherein said crystallization step is carried out to an average crystallinity through thickness measured by WAXS during said crystallization step of strictly greater than 7%.

11. 2. The twin-sheet thermoforming method according to claim 1, wherein the softening step (105) is carried out at a softening temperature having a value strictly higher than Tg and not higher than (Tg+80)°C.

12. 10. The twin-sheet thermoforming method of claim 1, wherein the crystallization step is carried out at a mold temperature close to the temperature at which the composition exhibits a minimum isothermal crystallization half-time.

13. 2. The twin-sheet thermoforming method of claim 1, wherein the difference between the mold temperature and the softening temperature is 60°C or less and / or 15°C or more.

14. 2. The twin-sheet thermoforming method of claim 1, wherein the contacting and fusing step is carried out at a pinch pressure having a value ranging from 1 bar to 50 bar.

15. A method for producing a hollow body having at least one inner surface made of a crystallized composition based on polyaryletherketone, comprising a step of obtaining the hollow body by the method of claim 1.

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