Blend comprising a polyarylene ether sulfone polymer and a phenoxy polymer, and films made from the blend

Abstract

The present invention relates to a blend comprising as components 85 to 68 wt.% of at least one polyarylene ether sulfone polymer (P1) with a viscosity number (VN) between 45 to 58 ml / g, and at least one phenoxy polymer (P2). Another aspect of the present invention is a film and a granulate made from the blend, and a sandwich panel comprising an upper top layer (UTL) comprising a polyarylene ether sulfone polymer and a fiber reinforcement, a foam core layer (FCL) comprising a polyarylene ether sulfone polymer, and a lower top layer (LTL) comprising a polyarylene ether sulfone polymer and a fiber reinforcement, wherein the upper top layer (UTL) is joined with the foam core layer (FCL) via a first film (F1) made from the blend, and wherein the lower top layer (LTL) is joined with the foam core layer (FCL) via a second film (F2) made from the blend. Another aspect of the present invention is a process to produce the sandwich panel, and the use of the sandwich panel as construction parts for aviation industry, or for the construction of rotor blades for wind turbines. Yet another aspect of the present invention is a process for the re-use of the sandwich panel, and the use of the blend as an adhesive layer.

Description

[0001] Blend comprising a polyarylene ether sulfone polymer and a phenoxy polymer, and films made from the blend

[0002] Description

[0003] The present invention relates to a blend comprising as components 85 to 68 wt.% of at least one polyarylene ether sulfone polymer (P1) with a viscosity number (VN) between 45 to 58 ml / g, and at least one phenoxy polymer (P2). Another aspect of the present invention is a film and a granulate made from the blend, and a sandwich panel comprising an upper top layer (UTL) comprising a polyarylene ether sulfone polymer and a fiber reinforcement, a foam core layer (FCL) comprising a polyarylene ether sulfone polymer, and a lower top layer (LTL) comprising a polyarylene ether sulfone polymer and a fiber reinforcement, wherein the upper top layer (UTL) is joined with the foam core layer (FCL) via a first film (F1) made from the blend, and wherein the lower top layer (LTL) is joined with the foam core layer (FCL) via a second film (F2) made from the blend. Another aspect of the present invention is a process to produce the sandwich panel, and the use of the sandwich panel as construction parts for aviation industry, or for the construction of rotor blades for wind turbines. Yet another aspect of the present invention is a process for the re-use of the sandwich panel, and the use of the blend as an adhesive layer.

[0004] For applications in various industries composite materials are used due to their unique combination of mechanical performance and low density. This allows lightweight constructions in many areas, particularly in the aviation industry or for the construction of rotor blades for wind turbines. The weight reduction generally contributes to the need for CO2-reduction in these applications.

[0005] To meet actual performance challenges, usually different types of materials are combined in one part, which is in contradiction to another society demand, the need for a circular economy. Thus, also for composite materials new end-of-life options are needed.

[0006] A segment where significant amounts of sandwich panels are consumed is the aircraft interior. Sandwich panels are intensively used to manufacture and customize different areas of the interior, like overhead storage compartments, floor panels, roof panels, side panels and cabin walls (E.A. Franco-Urquiza et.al. , Polymers 2021,13, 3258). The growth of air traffic and the continuous need to replace damaged parts or to complete refurbishment from time to time creates a high demand for such materials.

[0007] For the re-use of sandwich panels, it could be an option, to dismantle the whole part from the first application, grind the part and re-use the material in a molding composition together with other thermoplastic materials. Such a concept only works if thermoplastic polymers are used as matrix material in the composite. The potential to find high value applications for such regrinds would be further raised, if only one thermoplastic material is used for the different layers of the part, since it is generally known, that most mixtures of polymers are immiscible, which limits their mechanical performance (C. Koning et.al. , Progr. Polym Sci. 23, 707, 1998).

[0008] Actually, the largest share of sandwich panels for aircraft interior are based on Honeycomb core materials, made out of a polyaramide (Nomex® Honeycomb) which is covered by prepregs of different composition, but usually based on phenolic-resins or epoxy-resins. Since the resin forms a 3-dimensional network structure during the curing process, the final part cannot be molten again, which limits the re-use of such parts tremendously.

[0009] Hence, other options for the fabrication of sandwich panels are under discussion. For the production of sandwich panels usually a light core material is assembled with fiber reinforced layers, giving the panel the required bending strength. To replace the expensive Honeycomb structures, as core material thermoplastic foams with a density of 30 to 750 g / l can be used. Since the use in aircrafts requires high flame retardancy (low smoke and heat release), only high temperature resistant polymers like polyetherimide or polyarylene ether sulfones can be used as foam core.

[0010] Fiber reinforced outer layers with thermoplastic matrix materials can be produced by impregnating fibers or fabrics with the matrix polymer by means of solvent impregnation or pultrusion.

[0011] The main challenge for the production of thermoplastic sandwich panels is the lamination of the foam core and the fiber reinforced outer layers.

[0012] For the lamination of the different layers during the panel assembly special solventbased adhesives are necessary, which deteriorate the properties of the regrind significantly. Furthermore, the used solvents can create cracks in the foam core leading to reduced mechanical performance.

[0013] Thus, the objective of the invention was to provide a material that is capable to be used as an adhesive layer for the lamination of sandwich panels without using a solvent. The obtained sandwich panel should preferably fulfill the high flame retardancy requirements for the use in aircrafts. Moreover, the sandwich panel should preferably be re-usable after end of life.

[0014] This object is achieved by a blend comprising as components (P1) at least one polyarylene ether sulfone polymer with a viscosity number (VN) between 45 to 58 ml / g, measured according to ISO 1628, and

[0015] (P2) at least one phenoxy polymer, wherein the blend comprises component (P1) in an amount in the range of 85 to 68 wt.% and component (P2) in an amount in the range of 15 to 32 wt.%, wherein the wt.% values are in each case based on the total weight of the blend.

[0016] Surprisingly, it was found that the blend according to the invention can be used to assemble a sandwich panel solvent free. The sandwich panel produced by using films made from the inventive blend has good mechanical properties, good adhesion between the different layers and a good bending strength leading to a good adhesion of the different layers even after bending the sandwich panel.

[0017] Surprisingly, the sandwich panel according to the invention can be re-used. After grinding of the inventive sandwich panel, the ground material can be re-used for high value applications in various industries.

[0018] Polyarylene ether sulfone polymer

[0019] The inventive blend, the film as well as the granulate made from the blend comprise at least one polyarylene ether sulfone polymer.

[0020] The same holds true for the inventive sandwich panel. In the inventive sandwich panel, the top layer (UTL), the foam core layer (FCL), the lower top layer (LTL), the first film (F1), and the second film (F2) comprise each independently from each other at least one polyarylene ether sulfone polymer.

[0021] Polyarylene ether sulfone polymers are high-performance thermoplastics in that they feature high heat resistance, good mechanical properties, and inherent flame retardancy (E.M. Koch, H.-M. Walter, Kunststoffe 80 (1990) 1146; E. Ddring, Kunststoffe 80, (1990) 1149, N. Inchaurondo-Nehm, Kunststoffe 98, (2008) 190).

[0022] Polyarylene ether sulfone polymers can be formed inter alia either via the hydroxide method, wherein a salt is first formed from the dihydroxy component and the hydroxide, or via the carbonate method.

[0023] General information regarding the formation of polyarylene ether sulfone polymers by the hydroxide method is found inter alia in R.N. Johnson et.al., J.Polym. Sci. A-1 5 (1967) 2375, while the carbonate method is described in J.E. McGrath et.al., Polymer 25 (1984) 1827. Methods of forming polyarylene ether sulfone polymers from aromatic bishalogen compounds and aromatic bisphenols or salts thereof in an aprotic solvent in the presence of one or more alkali metal or ammonium carbonates or bicarbonates are known to a person skilled in the art and are described in EP-A 297 363 and EP-A 135 130 for example.

[0024] High-performance thermoplastics such as polyarylene ether sulfone polymers are formed by polycondensation reactions which are typically carried out at a high reaction temperature in dipolar aprotic solvents, for example DMF, DMAc, sulfolane, DMSO and NMP.

[0025] EP 0 412 499 describes a method of forming polyarylene ether sulfone polymers. The dihalogen component used in the method of EP 0412 499 is, for example, 4,4'-di- chlorodiphenyl sulfone or 4,4'-difluorodiphenyl sulfone. The dihydroxy components described in EP 0412 499 include bisphenol A, 4,4'-dihydroxydiphenyl sulfone and 4,4'-dihydroxybenzophenone. The polycondensation described in EP 0412 499 is carried out in the presence of sodium carbonate or sodium bicarbonate.

[0026] Preferred embodiments for the preparation of suitable polyarylene sulfone polymers, that are comprised in the inventive blend, the film made from the blend, and granulates made from the blend, as well as suitable polyarylene ether sulfone polymers comprised in the top layer (UTL), the foam core layer (FCL), the lower top layer (LTL), the first film (F1), and the second film (F2) of the inventive sandwich panel are described below.

[0027] In a preferred embodiment the polyarylene ether sulfone polymer is obtained by converting a reaction mixture (RG) comprising as components:

[0028] (A1) a dihalogen component comprising not less than 80 wt% of at least one dihalogen compound selected from the group consisting of 4,4‘-dichlorodiphenyl sulfone and 4,4'-difluorodiphenyl sulfone, based on the overall weight of component (A1) in reaction mixture (RG),

[0029] (B1) a dihydroxy component comprising not less than 80 wt% of at least one dihydroxy compound selected from the group consisting of 4,4'-dihydroxy- diphenyl sulfone, bisphenol A, 4,4'-dihydroxybiphenyl and hydroquinone, based on the overall weight of component (B1) in reaction mixture (RG).

[0030] Another object of the present invention, therefore, is a blend, wherein the at least one polyarylene ether sulfone polymer (component (P1)) is obtained by converting a reaction mixture (RG) comprising as components: (A1) a dihalogen component comprising not less than 80 wt% of at least one dihalogen compound selected from the group consisting of 4,4‘-dichlorodiphenyl sulfone and 4,4'-difluorodiphenyl sulfone, based on the overall weight of component (A1) in reaction mixture (RG),

[0031] (B1) a dihydroxy component comprising not less than 80 wt% of at least one dihydroxy compound selected from the group consisting of 4,4'-dihydroxy- diphenyl sulfone, bisphenol A, 4,4'-dihydroxybiphenyl and hydroquinone, based on the overall weight of component (B1) in reaction mixture (RG).

[0032] The polyarylene ether sulfone polymer is preferably formed by converting a reaction mixture (RG) comprising the above-described components (A1), (B1), and additionally components (C), and (D). Components (A1) and (B1) end up reacting with each other in a polycondensation reaction. Component (D) serves as solvent. Component (C) serves as base to deprotonate component (B1) during the condensation reaction.

[0033] The reaction mixture (RG) is the mixture which is preferably used for forming the polyarylene ether sulfone polymer. All particulars herein in relation to reaction mixture (RG) thus relate to the mixture which is present before the polycondensation. It is during the method of the present invention that the polycondensation takes place to convert reaction mixture (RG) into the target product, the polyarylene ether sulfone polymer, by polycondensation of components (A1) and (B1). The mixture which is obtained after the polycondensation and comprises the target product, the polyarylene ether sulfone polymer, is also referred to as product mixture (PG).

[0034] In general, the components of reaction mixture (RG) are reacted conjointly. The individual components may be mixed in a preceding step and then reacted. It is also possible to feed the individual components into a reactor, where they are mixed and subsequently reacted.

[0035] In the method of the present invention, the individual components of reaction mixture (RG) are generally converted conjointly. This conversion preferably takes place in a single stage. That is, the deprotonation of component (B1) and the condensation reaction between components (A1) and (B1) take place in a single reaction stage without isolation of intermediates, for example the deprotonated species of component (B1).

[0036] Component (A1)

[0037] Component (A1), which is also referred to as the dihalogen component, is present in reaction mixture (RG) in the form of at least one dihalogen compound. What is meant herein by "at least one dihalogen compound" is precisely one dihalogen compound and also mixtures of two or more dihalogen compounds.

[0038] So, component (A1) may comprise not only a single dihalogen compound but also a mixture of two or more dihalogen compounds.

[0039] Preferably component (A1) comprises not less than 50 wt% of at least one dihalogen compound selected from the group consisting of 4,4'-dichlorodiphenyl sulfone and 4,4'- difluorodiphenyl sulfone, based on the overall weight of component (A1) in reaction mixture (RG). The weight percentages here in relation to component (A1) further relate to the sum total of the 4,4'-dichlorodiphenyl sulfone used and of the 4,4'- difluorodiphenyl sulfone used. 4,4'-Dichlorodiphenyl sulfone is preferable to 4,4'- difluorodiphenyl sulfone. 4,4'-dichlorodiphenyl sulfone is especially preferred.

[0040] In one embodiment, component (A1) comprises not less than 80 wt%, preferably not less than 90 wt%, and more preferably not less than 95 wt% of at least one dihalogen compound selected from the group consisting of 4,4'-dichlorodiphenyl sulfone and 4,4'- difluorodiphenyl sulfone, based on the overall weight of component (A1) in reaction mixture (RG). The weight percentages here in relation to component (A1) further relate to the sum total of the 4,4'-dichlorodiphenyl sulfone used and of the 4,4'-difluoro- diphenyl sulfone used.

[0041] In one particularly preferred embodiment, component (A1) comprises not less than 50 wt%, preferably not less than 80 wt%, more preferably not less than 90 wt% and especially not less than 95 wt% of 4,4'-dichlorodiphenyl sulfone.

[0042] It is further particularly preferable for reaction mixture (RG) not to contain any further dihalogen compounds in addition to the dihalogen compounds of component (A1).

[0043] In a further particularly preferred embodiment, component (A1) consists of 4,4'- dichlorodiphenyl sulfone.

[0044] Component (B1)

[0045] Component (B1), which is also referred to as the dihydroxy component, is present in reaction mixture (RG) in the form of at least one dihydroxy compound. What is meant herein by "at least one dihydroxy compound" is precisely one dihydroxy compound and also mixtures of two or more dihydroxy compounds.

[0046] So, component (B1) may comprise not only a single dihydroxy compound but also mixtures of two or more dihydroxy compounds. In one embodiment component (B1) comprise not less than 50 wt% of at least one dihydroxy compound selected from the group consisting of 4,4'-dihydroxydiphenyl sulfone, bisphenol A (2,2-bis(4-hydroxyphenyl)propane), 4,4'-dihydroxybiphenyl and hydroquinone, based on the overall weight of component (B1) in reaction mixture (RG). The weight percentages here in relation to component (B1) further relate to the total sum of the 4,4'-dihydroxydiphenyl sulfone, bisphenol A (2,2-bis-(4- hydroxyphenyl)propane), 4,4'-dihydroxybenzophenone and hydroquinone used. Of the aforementioned dihydroxy compounds 4,4'-dihydroxydiphenyl sulfone, bisphenol A, and 4,4'-dihydroxybiphenyl are preferable, while 4,4'-dihydroxydiphenyl sulfone is particularly preferable.

[0047] In one embodiment, component (B1) comprises not less than 80 wt%, preferably not less than 90 wt% and more preferably not less than 95 wt% of at least one dihydroxy compound selected from the group consisting of 4,4'-dihydroxydiphenyl sulfone, bisphenol A (2,2-bis(4-hydroxyphenyl)propane), 4,4'-dihydroxybiphenyl and hydroquinone, based on the overall weight of component (B1) in reaction mixture (RG). The weight percentages here in relation to component (B1) further relate to the total sum of the 4,4'-dihydroxydiphenyl sulfone, bisphenol A (2,2-bis-(4-hydroxyphenyl)- propane), 4,4'-dihydroxybiphenyl and hydroquinone used.

[0048] In one particularly preferred embodiment, component (B1) comprises not less than 50 wt%, preferably not less than 80 wt%, more preferably not less than 90 wt% and especially not less than 95 wt% of bisphenol A.

[0049] In one particularly preferred embodiment, component (B1) comprises not less than 50 wt%, preferably not less than 80 wt%, more preferably not less than 90 wt% and especially not less than 95 wt% of 4,4'-dihydroxydiphenyl sulfone.

[0050] In one particularly preferred embodiment, component (B1) comprises not less than 50 wt%, preferably not less than 80 wt%, more preferably not less than 90 wt% and especially not less than 95 wt% of 4,4’-dihydroxybiphenyl.

[0051] It is further particularly preferable that the reaction mixture (RG) does not contain any further dihydroxy compounds in addition to the dihydroxy compound(s) of component (B1).

[0052] In a further particularly preferred embodiment, component (B1) consists of 4,4'- dihydroxydiphenyl sulfone.

[0053] Since reaction mixture (RG) comprises potassium carbonate as component (C), the hydroxyl groups of the dihydroxy compounds used as component (B1) may partly be present in reaction mixture (RG) in deprotonated form. Component (C)

[0054] Reaction mixture (RG) comprises potassium carbonate as component (C), which is also known as the carbonate component. The used potassium carbonate is preferably anhydrous.

[0055] In a preferred embodiment component (C) comprise not less than 90 wt% of potassium carbonate, based on the overall weight of component (C) in reaction mixture (RG).

[0056] In one embodiment, component (C) comprises not less than 80 wt%, preferably not less than 90 wt% and more preferably not less than 98 wt% of potassium carbonate having a volume-averaged particle size of < 50 pm, based on the overall weight of component (B1) in reaction mixture (RG).

[0057] In one particularly preferred embodiment, component (C) consists of potassium carbonate.

[0058] Component (D)

[0059] Reaction mixture (RG) preferably comprises at least one aprotic polar solvent as component (D). What is meant by "at least one aprotic polar solvent" in the present invention is exactly one aprotic polar solvent and mixtures of two or more aprotic polar solvents.

[0060] Useful aprotic polar solvents include for example, anisole, dimethylformamide, dimethyl sulfoxide, sulfolane, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and also mixtures thereof.

[0061] N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and also mixtures thereof are preferable for use as aprotic polar solvent. N-methyl-2-pyrrolidone is particularly preferable for use as aprotic polar solvent.

[0062] In one preferred embodiment, component (D) comprises not less than 90 wt% of at least one solvent selected from the group consisting of N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone, based on the overall weight of component (D) in reaction mixture (RG). N-methyl-2-pyrrolidone is particularly preferable for use as component (D).

[0063] In one preferred embodiment, component (D) consists of N-methyl-2-pyrrolidone. N-methyl-2-pyrrolidone is also known as NMP or N-methylpyrrolidone. In a further preferred embodiment, the reaction mixture does not contain any further aprotic polar solvents in addition to the aprotic polar solvents of component (D).

[0064] To form the polyarylene ether sulfone polymer the reaction mixture (RG) is preferably reacted under conditions of the carbonate method. The reaction involved is a polycondensation reaction and is generally carried out at temperatures in the range from 80 to 250°C and preferably at temperatures in the range from 100 to 220°C, the upper limit of the temperature being determined by the boiling point of the aprotic polar solvent (component D) at atmospheric pressure (1013.25 mbar). The reaction is preferably carried out at atmospheric pressure. The time interval for the reaction is preferably in the range from 0.5 to 12 hours, especially in the range from 2 to 10 hours.

[0065] The terminal groups of the polyarylene ether sulfone polymers depend on the reaction conditions and the molar ratios of components (A1) and (B1) and are generally either halogen groups, in particular chlorine groups, or etherified groups, in particular alkyl ether groups. Etherified end groups are obtainable by reacting the terminal OH / phenoxide groups with suitable etherifying agents.

[0066] Examples of suitable etherifying agents are monofunctional alkyl or aryl halides, for example C C6alkyl chlorides, bromides or iodides, preferably methyl chloride, or benzyl chloride, bromide or iodide, or mixtures thereof. The terminal groups of the polyarylene ether sulfone polymer according to the present invention are preferably halogen groups, in particular chlorine, and also alkoxy groups, in particular methoxy, aryloxy groups, in particular phenoxy, or benzyloxy.

[0067] The polyarylene ether sulfone polymer obtained according to the present invention may be isolated by precipitating the polymer solution in water or mixtures of water with further solvents, for example alcohols. The precipitated polyarylene ether sulfone polymer may subsequently be extracted with water and thereafter dried. In one embodiment of the invention, the precipitation may also take place in an acidic medium. Suitable acids include, for example, organic or inorganic acids, for example carboxylic acids such as acetic acid, propionic acid, succinic acid or citric acid, and also mineral acids such as, for example, hydrochloric acid, sulfuric acid or phosphoric acid.

[0068] Suitable methods of forming the aforementioned polyarylene ether sulfone polymers are known per se to a person skilled in the art and are described, for example, in Herman F. Mark, "Encyclopedia of Polymer Science and Technology", third edition, Volume 4, 2003, chapter "Polysulfones" on pages 2 to 8 and also in Hans R. Kricheldorf, "Aromatic Polyethers" in: Handbook of Polymer Synthesis, second edition, 2005 on pages 427 to 443. Preferred polyarylene ether sulfone polymers comprise at least one of the following building blocks la to Ic as structural repeat units:

[0069] It is also particularly preferable for the polyarylene ether sulfone polymer to be composed essentially of at least one variety of building blocks selected from the group consisting of la, lb and Ic.

[0070] Particular preference is further given to polyarylene ether sulfone polymers composed of repeat units of formula lb. Polyether sulfone (PESLI) is another appellation for these polyarylene ether sulfone polymers.

[0071] Abbreviations such as PESLI and PSU herein conform to DIN EN ISO 1043-1 (Plastics - Symbols and abbreviated terms - Part 1: Basic polymers and their special characteristics (ISO 1043-1 :2001); German version of EN ISO 1043-1 :2002).

[0072] Particular preference is further given to block or other copolymers constructed of repeat units of formulae la, lb and Ic.

[0073] The weight average molecular weight (Mw) of the polyarylene ether sulfone polymer obtainable by the above described method is generally in the range from 10 000 to 150 000 g / mol, preferably in the range from 15 000 to 120 000 g / mol and more preferably in the range from 18 000 to 100 000 g / mol. The weight average molecular weights (Mw) are measured using gel permeation chromatography (GPC). This measurement is carried out using gel permeation chromatography (GPC). Dimethylacetamide (DMAc) was used as solvent and narrowly distributed polymethyl methacrylate was used as standard in the measurement. Preferred are polyarylene ether sulfone polymers with a Viscosity number (V.N.) between 40 and 120 ml / g measured according to ISO 1628, preferably in N-methyl-2- pyrrolidone (NMP) at 25 °C

[0074] Blend

[0075] The blend according to the invention comprises as component (P1) at least one polyarylene ether sulfone polymer. What is meant herein by “at least one polyarylene ether sulfone polymer” is precisely one polyarylene ether sulfone polymer and also mixtures of two or more different polyarylene ether sulfone polymers. Preferably, the inventive blend comprises one polyarylene ether sulfone polymer.

[0076] For component (P1) comprised in the inventive blend the above description and preferences in view of the at least one polyarylene ether sulfone polymer holds true accordingly under the on condition that the at least one polyarylene ether sulfone polymer has a viscosity number (VN) in the range of 45 to 58 ml / g measured according to ISO 1628, preferably in N-methyl-2-pyrrolidone at 25 °C

[0077] The weight average molecular weight (Mw) of component (P1) comprised in the inventive blend is generally in the range from 40 000 to 57 000 g / mol, preferably in the range from 41 000 to 56 000 g / mol and more preferably in the range from 42 000 to 55 000 g / mol. The weight average molecular weights (Mw) are measured using gel permeation chromatography (GPC). This measurement is carried out using gel permeation chromatography (GPC). Dimethylacetamide (DMAc) was used as solvent and narrowly distributed polymethyl methacrylate was used as standard in the measurement.

[0078] In a preferred embodiment, the blend comprises as component (P1) at least one polyarylene ether sulfone polymer selected from the group consisting of polysulfone (PSU), polyether sulfone (PESLI) and polybiphenyl sulfone (PPSLI).

[0079] In an especially preferred embodiment, the polyarylene ether sulfone polymer (component (P1)) comprised in the blend is polyether sulfone (PESLI).

[0080] The blend according to the invention comprises as component (P2) at least one phenoxy polymer. What is meant herein by “at least one phenoxy polymer” is precisely one phenoxy polymer and also mixtures of two or more different phenoxy polymers. Preferably, the inventive blend comprises one phenoxy polymer. Phenoxy polymers are a commercially available polymers containing hydroxyl-groups available under the tradename Phenoxy®. A suitable phenoxy polymer is Phenoxy® PKHH. The structural formula is given below in formula II).

[0081] Formula II

[0082] In formula II n’ is preferably an integer in the range of 10 to 100, preferably in the range of 15 to 90, and more preferably in the range of 20 to 80.

[0083] Phenoxy polymers can be prepared by reacting bisphenol A with epichlorohydrin.

[0084] Preferably as a phenoxy polymer with a Tg in the range of 70 to 100 °C, more preferably in the range of 80 to 98 °C and especially preferred in the range of 85 to 98 °C is used. The glass transition temperature Tg is determined by DSC- measurements according to ISO 11357-1 , using a heating rate of 10 K / min.

[0085] Suitable phenoxy polymers have a number average molecular weight in the range of 2500 to 25 000 g / mol, preferably in the range of 5 000 to 20 000 g / mol. The number average molecular weight is determined as described below for the polyarylene ether sulfone polymers comprised in the upper top layer (UTL).

[0086] In a preferred embodiment, the blend comprises from 68 to 85 wt.-% of component (P1) and from 15 to 32 wt.-% of component (P2), based on the total weight of the blend.

[0087] In a more preferred embodiment, the blend comprises from 70 to 82 wt.-% of component (P1) and from 18 to 30 wt.-% of component (P2), based on the total weight of the blend.

[0088] In a particularly preferred embodiment, the blend comprises from 72 to 80 wt.-% of component (P1) and from 20 to 28 wt.-% of component (P2), based on the total weight of the blend. The blend according to the invention in a preferred embodiment comprises components (P1) and (P2) in a total amount of at least 80 wt.%, more preferably in a total of at least 90 wt.%, based on the total weight of the blend.

[0089] In another preferred embodiment the blend according to the invention comprises, based on the total weight of the blend equal or less than 20 wt.%, more preferably less than 10 wt.% of components different to components (P1) and (P2).

[0090] The inventive blend can be used as an adhesive layer for joining a foam core layer (FCL) with a fiber reinforced top layer (TL). Preferably the blend is then used in the form of a film.

[0091] Therefore, another object of the present invention is the use of a film comprising the blend as an adhesive layer for joining a foam core layer (FCL) with a fiber reinforced top layer (TL).

[0092] The blend, preferably in the form of a film, is preferably used to prepare a sandwich panel as described below. The sandwich panel preferably comprises an upper top layer (UTL) and a lower top layer (LTL) and a foam core layer (FCL) between the upper top layer (UTL) and a lower top layer (LTL).

[0093] Another object of the present invention is a film made from the blend.

[0094] The film made from the blend has preferably a thickness in the range of 15 to 80 pm, more preferred in the range of 15 to 50 pm and particularly preferred in the range of 20 to 40 pm.

[0095] Another object of the present invention is a film, wherein the at least one polyarylene ether sulfone polymer (component P1) is obtained by converting a reaction mixture (RG) comprising as components:

[0096] (A1) dihalogen component comprising not less than 80 wt.% of at least one dihalogen compound selected from the group consisting of 4,4’-dichlorodiphenyl sulfone and 4,4’-difluorodiphenyl sulfone, based on the total weight of component (A1) in the reaction mixture (RG),

[0097] (B1) dihydroxy component comprising not less than 80 wt.% of at least one dihydroxy compound selected from the group consisting of 4,4’-dihydroxy diphenyl sulfone, bisphenol A, 4,4’-dihydroxy biphenyl and hydroquinone, based on the total weight of component (B1) in the reaction mixture (RG).

[0098] Another object of the present invention is a granulate made from the blend according to the invention.

[0099] Upper top layer (UTL) / lower top layer (LTL)

[0100] The upper top layer (UTL) comprises at least one polyarylene ether sulfone and at least one fiber reinforcement. What is meant herein by “at least one polyarylene ether sulfone polymer” is precisely one polyarylene ether sulfone polymer and also mixtures of two or more different polyarylene ether sulfone polymers. Preferably, the upper top layer (UTL) comprises one polyarylene ether sulfone polymer.

[0101] In view of the at least one polyarylene ether sulfone polymer comprised in the upper top layer (UTL), the above made description, explanations, and preferences in view of the polyarylene ether sulfone polymer hold true accordingly.

[0102] The glass transition temperature Tg of the polyarylene ether sulfone polymer comprised in the upper top layer (UTL) is preferably in the range of 180 to 230 °C, more preferably in the range of from 185 to 228 °C, and most preferred in the range of from 185 to 226 °C. The glass transition temperature Tg is determined by DSC- measurements according to ISO 11357-1 , using a heating rate of 10 K / min.

[0103] The weight average molecular weight (Mw) of the polyarylene ether sulfone polymer comprised in the upper top layer (UTL) is generally in the range from 50 000 to150 000 g / mol, preferably in the range from 52 000 to 120 000 g / mol and more preferably in the range from 53 000 to 100 000 g / mol. The weight average molecular weights (Mw) are measured using gel permeation chromatography (GPC). This measurement is carried out using gel permeation chromatography (GPC). Dimethylacetamide (DMAc) was used as solvent and narrowly distributed polymethyl methacrylate was used as standard in the measurement. In a preferred embodiment the average molecular weight (Mw) of the polyarylene ether sulfone polymer comprised in the upper top layer (UTL) is higher than the average molecular weight (Mw) of the polyarylene ether sulfone polymer comprised in the blend.

[0104] In a preferred embodiment, the upper top layer (UTL) comprises at least one polyarylene ether sulfone polymer selected from the group consisting of polysulfone (PSU), polyether sulfone (PESU) and polybiphenyl sulfone (PPSU).

[0105] In an especially preferred embodiment, the polyarylene ether sulfone polymer comprised in the upper layer (UTL) is polyether sulfone (PESU). The upper top layer (UTL), moreover, comprises at least one fiber reinforcement. What is meant herein by “at least one fiber reinforcement” is precisely one fiber reinforcement and also mixtures of two or more fiber reinforcements.

[0106] Suitable fiber reinforcements are, for example, selected from the group consisting of glass fibers and carbon fibers. Usually reinforced thermoplastic laminates (RTLs) are used as upper top layer (UTL).

[0107] In a preferred embodiment, the upper top layer (UTL) comprises from 25 to 70 wt.-% of the at least one polyarylene ether sulfone polymer and 30 to 75 wt.-% of the at least one fiber reinforcement, based on the total weight of the upper top layer (UTL).

[0108] The preparation of the upper top layer (UTL) is known to the person skilled in the art. The upper top layer (UTL) can, for example, be prepared by impregnation of the at least one fiber reinforcement with the at least one polyarylene ether sulfone polymer in the molten state. Suitable procedures for the preparation of the upper top layer (UTL) are, for example melt pressing of layers of thermoplastic films with layers of fibers in a press to achieve a homogeneous distribution of the thermoplastic material in the RTL. The fiber orientation of the different fiber layers can be adapted to the needs of the particular application and can be 0 / 90 / +45 / -45. The consolidation in a press allows easy processing of the RTLs. RTLs can also be obtained by powder impregnation of fabrics. Details about these processes are given in Valente, M. polymers 2023, 15, 242.

[0109] The upper top layer (UTL), and the lower top layer (LTL) comprised in the sandwich panel preferably independently from each other have a thickness in the range of 0.1 to 0.5 mm. In a preferred embodiment the upper top layer (UTL), and the lower top layer (LTL) comprised in the sandwich panel preferably have the same thickness in the range of 0.1 to 0.5 mm.

[0110] Another object of the present invention, therefore, is a sandwich, wherein the upper top layer (UTL), and the lower top layer (LTL) independently from each other have a thickness in the range of 0.1 to 0.5 mm.

[0111] The upper top layer (UTL), and the lower top layer (LTL) comprised in the sandwich panel preferably independently from each other have an areal weight in the range of 150 to 600 g / m2. In a preferred embodiment the upper top layer (UTL), and the lower top layer (LTL) comprised in the sandwich panel preferably have the same areal weight in the range of 200 to 500 g / m2. In another preferred embodiment the upper top layer (UTL), and the lower top layer (LTL) comprised in the sandwich panel comprise the same polyarylene ether sulfone polymer.

[0112] In another preferred embodiment the upper top layer (UTL), and the lower top layer (LTL) comprised in the sandwich panel comprise the same polyarylene ether sulfone polymer and the same fiber reinforcement. In another preferred embodiment the upper top layer (UTL), and the lower top layer (LTL) comprised in the sandwich panel comprise the same polyarylene ether sulfone polymer, the same fiber reinforcement and have the same thickness. In another preferred embodiment the upper top layer (UTL), and the lower top layer (LTL) comprised in the sandwich panel comprise the same polyarylene ether sulfone polymer, the same fiber reinforcement, have the same thickness, and have the same areal weight.

[0113] In another preferred embodiment the upper top layer (UTL), and the lower top layer (LTL) comprised in the sandwich panel comprise the same polyarylene ether sulfone polymer, the same fiber reinforcement, have the same thickness, have the same areal weight and have the same glass transition temperature.

[0114] In an especially preferred embodiment the upper top layer (UTL), and the lower top layer (LTL) are identical.

[0115] In view of the lower top layer (LTL), the above made description, explanations, and preferences in view of the upper top layer (UTL) hold true accordingly.

[0116] The lower top layer (LTL) comprises at least one polyarylene ether sulfone and at least one fiber reinforcement. What is meant herein by “at least one polyarylene ether sulfone polymer” is precisely one polyarylene ether sulfone polymer and also mixtures of two or more different polyarylene ether sulfone polymers. Preferably, the lower top layer (LTL) comprises one polyarylene ether sulfone polymer.

[0117] In view of the at least one polyarylene ether sulfone polymer comprised in the lower top layer (LTL), the above made description, explanations, and preferences in view of the polyarylene ether sulfone polymer hold true accordingly.

[0118] The glass transition temperature Tg of the polyarylene ether sulfone polymer comprised in the lower top layer (LTL) is preferably in the range of 180 to 230 °C, more preferably in the range of from 185 to 228 °C, and most preferred in the range of from 185 to 226 °C. The glass transition temperature is determined as described above.

[0119] The weight average molecular weight (Mw) of the polyarylene ether sulfone polymer comprised in the lower top layer (LTL) is generally in the range from 50 000 to 150 000 g / mol, preferably in the range from 52 000 to 120 000 g / mol and more preferably in the range from 53 000 to 100 000 g / mol. The weight average molecular weights (Mw) are measured using gel permeation chromatography (GPC). This measurement is carried out using gel permeation chromatography (GPC). Dimethylacetamide (DMAc) was used as solvent and narrowly distributed polymethyl methacrylate was used as standard in the measurement. In a preferred embodiment the average molecular weight (Mw) of the polyarylene ether sulfone polymer comprised in the lower top layer (LTL) is higher than the average molecular weight (Mw) of the polyarylene ether sulfone polymer comprised in the blend.

[0120] In a preferred embodiment, the lower top layer (LTL) comprises at least one polyarylene ether sulfone polymer selected from the group consisting of polysulfone (PSU), polyether sulfone (PESU) and polybiphenyl sulfone (PPSU).

[0121] In an especially preferred embodiment, the polyarylene ether sulfone polymer comprised in the lower layer (LTL) is polyether sulfone (PESU).

[0122] The lower top layer (LTL), moreover, comprises at least one fiber reinforcement. What is meant herein by “at least one fiber reinforcement” is precisely one fiber reinforcement and also mixtures of two or more fiber reinforcements.

[0123] Suitable fiber reinforcements are, for example, selected from the group consisting of glass fibers and carbon fibers. Usually reinforced thermoplastic laminates (RTLs) are used as lower top layer (LTL).

[0124] In a preferred embodiment, the lower top layer (LTL) comprises from 25 to 70 wt.-% of the at least one polyarylene ether sulfone polymer and 30 to 75 wt.-% of the at least one fiber reinforcement, based on the total weight of the lower top layer (LTL).

[0125] The preparation of the lower top layer (LTL) is known to the person skilled in the art. The lower top layer (LTL) can, for example, be prepared by impregnation of the at least one fiber reinforcement with the at least one polyarylene ether sulfone polymer in the molten state. Suitable procedures for the preparation of the lower top layer (LTL) are, those described above for the upper top layer (UTL).

[0126] Foam core layer (FCL)

[0127] The foam core layer (FCL) comprises at least one polyarylene ether sulfone. What is meant herein by “at least one polyarylene ether sulfone polymer” is precisely one polyarylene ether sulfone polymer and also mixtures of two or more different polyarylene ether sulfone polymers. Preferably, the foam core layer (FCL) comprises one polyarylene ether sulfone polymer. In view of the at least one polyarylene ether sulfone polymer comprised in the foam core layer (FCL), the above made description, explanations, and preferences in view of the polyarylene ether sulfone polymer hold true accordingly.

[0128] The glass transition temperature Tg of the polyarylene ether sulfone polymer comprised in the foam core layer (FCL) is preferably in the range of 180 to 230 °C, more preferably in the range of from 185 to 228 °C, and most preferred in the range of from 185 to 226 °C. The glass transition temperature is determined as described above.

[0129] The weight average molecular weight (Mw) of the polyarylene ether sulfone polymer comprised in the foam core layer (FCL) is generally in the range from 50 000 to 150 000 g / mol, preferably in the range from 52 000 to 120 000 g / mol and more preferably in the range from 53 000 to 100 000 g / mol. The weight average molecular weights (Mw) are measured using gel permeation chromatography (GPC). This measurement is carried out using gel permeation chromatography (GPC). Dimethylacetamide (DMAc) was used as solvent and narrowly distributed polymethyl methacrylate was used as standard in the measurement. In a preferred embodiment the average molecular weight (Mw) of the polyarylene ether sulfone polymer comprised in the foam core layer (FCL) is higher than the average molecular weight (Mw) of the polyarylene ether sulfone polymer comprised in the blend.

[0130] In a preferred embodiment, the foam core layer (FCL) comprises at least one polyarylene ether sulfone polymer selected from the group consisting of polysulfone (PSU), polyether sulfone (PESU) and polybiphenyl sulfone (PPSU).

[0131] In an especially preferred embodiment, the polyarylene ether sulfone polymer comprised in the foam core layer (FCL) is polyether sulfone (PESU).

[0132] The preparation of the foam core layer (FCL) is known to the person skilled in the art. The foam core layer (FCL) can, for example, be prepared by extrusion using solvents as foaming agents and special process parameters as described in DE 4207057. Water based mixtures as foaming agents for the preparation of foam core layers (FCL) are described in EP 1333051. If PESU-mixtures with broad molecular weight distribution are used, foaming with water is possible.

[0133] The foam core layer (FCL) comprised in the sandwich panel preferably has a thickness in the range of 0.76 to 50 mm.

[0134] Another object of the present invention, therefore, is a sandwich panel, wherein the foam core layer (FCL) has a thickness in the range of 0.76 to 50 mm. The foam core layer (FCL) comprised in the sandwich panel has a density in the range of 25 to 200 kg / m3, preferably in the range of 35 to 155 kg / m3.

[0135] Another object of the present invention therefor is a sandwich panel, wherein the foam core layer (FCL) has a density in the range of 25 to 200 kg / m3.

[0136] In another preferred embodiment the foam core layer (FCL), the upper top layer (UTL), and the lower top layer (LTL) comprised in the sandwich panel comprise the same polyarylene ether sulfone polymer.

[0137] First film (F1) / second film (F2)

[0138] The first film (F1) comprises the blend as described above. In view of the first film (F1) the above made description, explanations, and preferences in view of the blend hold true accordingly.

[0139] The preparation of the first film (F1) is known to the person skilled in the art. The first film (F1) can, for example, be prepared by film extrusion of the blend as described above. Details about film extrusion are known in the art, e.g. from C. Rauwendaal, “Polymer Extrusion” Hanser, 5thEdition 2014.

[0140] The first film (F1), and the second film (F2) comprised in the sandwich panel preferably independently from each other have a thickness in the range of 0.02 to 0.15 mm. In a preferred embodiment the first film (F1), and second film (F2) comprised in the sandwich panel preferably have the same thickness in the range of 0.02 to 0.15 mm.

[0141] The first film (F1), and the second film (F2) comprised in the sandwich panel preferably independently from each other have a density in the range of 1.15 to 1.36 g / cm3. In a preferred embodiment the first film (F1), and the second film (F2) comprised in the sandwich panel preferably have the same density in the range of 1.16 to 1.35 g / cm3.

[0142] In another preferred embodiment the first film (F1), and the second film (F2) contained in the sandwich panel comprise the same polyarylene ether sulfone polymer.

[0143] In another preferred embodiment the first film (F1), and the second film (F2) contained in the sandwich panel comprise the same polyarylene ether sulfone polymer and the same phenoxy polymer. In another preferred embodiment the first film (F1), and the second film (F2) contained in the sandwich panel comprise the same polyarylene ether sulfone polymer, the same phenoxy polymer and have the same thickness. In another preferred embodiment the first film (F1), and the second film (F2) contained in the sandwich panel comprise the same polyarylene ether sulfone polymer, the same phenoxy polymer, have the same thickness, and have the same density.

[0144] In another preferred embodiment the blend contained in the first film (F1), and the blend contained in the second film (F2) utilized in the sandwich panel comprise the same polyarylene ether sulfone polymer, the same phenoxy polymer, have the same thickness, have the same density and have the same glass transition temperature Tg.

[0145] In an especially preferred embodiment the first film (F1), and the second film (F2) are identical.

[0146] Preferably the blend comprised in the first film (F1) has a glass transition temperature Tg at least 5K below the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the upper top layer (UTL) and the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the foam core layer (FCL). The glass transition temperature Tg is determined as described above.

[0147] Therefore, another object of the present invention is a sandwich panel, wherein the blend comprised in the first film (F1) has a glass transition temperature Tg at least 5K below the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the upper top layer (UTL) and the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the foam core layer (FCL).

[0148] More preferably the blend comprised in the first film (F1) has a glass transition temperature Tg at least 5K below the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the upper top layer (UTL) and the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the foam core layer (FCL) and the glass transition temperature Tg of the lower top layer (LTL).

[0149] In case the blend comprised in the first film (F1) has more than one glass transition temperature Tg, reference is made to the upper glass transition temperature Tg.

[0150] The first film (F1) according to the invention in a preferred embodiment comprises the blend in a total amount of at least 80 wt.%, more preferably in a total of at least 90 wt.%, based on the total weight of the first film (F1).

[0151] In another preferred embodiment the first film (F1) according to the invention comprises, based on the total weight of first film (F1) equal or less than 20 wt.%, more preferably less than 10 wt.% of components different from the blend. In view of the second film (F2), the above made description, explanations, and preferences in view of the first film (F1) hold true accordingly.

[0152] The second film (F2) comprises the blend as described above. In view of second film (F2) the above made description, explanations, and preferences in view of the blend hold true accordingly.

[0153] Preferably the blend comprised in the second film (F2) has a glass transition temperature Tg at least 5K below the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the upper top layer (UTL) and the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the foam core layer (FCL). The glass transition temperature Tg is determined as described above.

[0154] Therefore, another object of the present invention is a sandwich panel, wherein the blend comprised in the second film (F2) has a glass transition temperature Tg at least 5K below the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the lower top layer (LTL) and the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the foam core layer (FCL).

[0155] More preferably the blend comprised in the second film (F2) has a glass transition temperature Tg at least 5K below the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the upper top layer (UTL) and the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the foam core layer (FCL) and the glass transition temperature of the lower top layer (LTL).

[0156] In case the blend comprised in the second film (F2) has more than one glass transition temperature Tg, reference is made to the upper glass transition temperature Tg.

[0157] Sandwich panel

[0158] The sandwich panel preferably has a thickness in the range of 1.0 to 51.3 mm.

[0159] Therefore, another object of the present invention is a sandwich panel, wherein the sandwich panel has a thickness in the range of 1.0 to 51.3 mm.

[0160] The sandwich panel comprises starting from the upper top layer (UTL) layers in the following order: upper top layer (UTL), first film (F1), foam core layer (FCL), second film (F2), and lower top layer (LTL). The sandwich panel in a preferred embodiment comprises at least 80 wt.-%, more preferably at least 85 wt.-% and particularly preferred at least 90 wt.-% of the at least one polyarylene ether sulfone polymer, based on the total weight of polymers in the sandwich panel.

[0161] In another preferred embodiment the sandwich panel comprises only one kind of polyarylene ether sulfone polymer. In a more preferred embodiment, the sandwich panel comprises only one kind of polyarylene ether sulfone polymer, wherein the polyarylene ether sulfone polymer is selected from the group consisting of polysulfone (PSU), polyether sulfone (PESLI) and polybiphenyl sulfone (PPSLI).

[0162] In an especially preferred embodiment, the sandwich panel comprises only one kind of polyarylene ether sulfone polymer, wherein the polyarylene ether sulfone polymer is polyether sulfone (PESLI).

[0163] Therefore, another object of the present invention is a sandwich panel, wherein the at least one polyarylene ether sulfone polymer comprised in the upper top layer (UTL), the at least one polyarylene ether sulfone polymer comprised in the foam core layer (FCL), the at least one polyarylene ether sulfone polymer comprised in the lower top layer (LTL), the at least one polyarylene ether sulfone polymer comprised in the first film (F1), and the at least one polyarylene ether sulfone polymer comprised in the second film (F2) are each independently from each other at least one polymer selected from the group consisting of polysulfone (PSU), polyethersulfone (PESU) and polybiphenyl sulfone (PPSU).

[0164] Therefore, another object of the present invention is a sandwich panel, wherein the upper top layer (UTL), the foam core layer (FCL), the lower top layer (LTL), the first film (F1), and the second film (F2) each comprise the same polyarylene ether sulfone polymer.

[0165] Process to produce the sandwich panel

[0166] Another object of the present invention is a process for the production of a sandwich panel according to the invention comprising the steps: i) providing the upper top layer (UTL) comprising at least one polyarylene ether sulfone polymer and at least one fiber reinforcement, the foam core layer (FCL) comprising at least one polyarylene ether sulfone polymer, the lower top layer (LTL) comprising at least one polyarylene ether sulfone polymer and at least one fiber reinforcement, ii) placing the first film (F1) of the blend between the upper top layer (UTL) and the foam core layer (FLC), iii) placing the second film (F2) of the blend between the lower top layer (LTL) and the foam core layer (FLC), to obtain a sandwich comprising starting from the upper top layer (UTL) layers in the following order: upper top layer (UTL), first film (F1) foam core layer (FCL), second film (F2), and lower top layer (LTL), and iv) heating the sandwich obtained step in iii) to a temperature at most 1K below the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the upper top layer (UTL) and the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the foam core layer (FCL) and the glass transition temperature Tg of the lower top layer (LTL).

[0167] Steps i) to iii) can be carried out in any order. Preferably steps i) to iii) are carried out concurrently. Heating of individual layers by means of IR-radiation before assembly to the panel is also possible.

[0168] In a preferred embodiment in step iv) the sandwich obtained in step iii) is heated to a temperature in the range of 1 to 30 K, more preferably 5 to 25 K and especially preferred 10 to 20 K below the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the upper top layer (UTL) and the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the foam core layer (FCL) and the glass transition temperature Tg of the lower top layer (LTL).

[0169] In another preferred embodiment in step iv) to the upper top layer (UTL) and the lower top layer (LTL) of the sandwich obtained step iii) a pressure in the range of 0.05 to 6 MPa is applied.

[0170] The sandwich panel according to the invention in a preferred embodiment is used as construction part for aviation industry, or for the construction of rotor blades for wind turbines.

[0171] In an especially preferred embodiment, the sandwich panel according to the invention is used as an interior trim for aircraft cabins.

[0172] In another preferred embodiment, the sandwich panel according to the invention is used in aircrafts as parts of the interior, preferably overhead storage compartments, floor panels, roof panels, side panels and cabin walls. The sandwich panel according to the invention at the end of its first application can be re-used. Therefore, another object of the present application is a process for the re-use of the sandwich panel according to the invention at the end of its first application comprising the steps: a) crushing the sandwich panel to obtain a ground material b) using the ground material obtained in step a) to produce new products.

[0173] The crushing in step a) can be done be grinding and / or milling. The product produced in step b) is preferably a fiber reinforced polyarylene ether sulfone polymer compound.

[0174] The present invention is more particularly elucidated by the examples which follow without being restricted thereto.

[0175] Components used:

[0176] Foam core layer (FCL):

[0177] As foam core layer (FCL) a polyethersulfone (PESU)-based foam Divinycell F50 with a thickness of 20 mm was used. Tg of the foam is 225°C, as measured by DSC (as described above).

[0178] Upper top layer (UTL) / lower top layer (LTL):

[0179] As inventive upper top layer (UTL) and lower top layer (LTL) a polyethersulfone(PESU)-coated glass fiber fabric with an area weight of 460 g / m2and a polymer content of 155 g / m2was used (UTL / LTLJnv).

[0180] First film (F1) / second film (F2)

[0181] For the preparation of the first film (F1) and the second film (F2) the following polymers were used:

[0182] Component (P1)

[0183] PESU 1 : Polyethersulfone with a V.N. of 45 ml / g (ISO 1628, NMP, 25°C); Tg = 224°C

[0184] PESU 2: Polyethersulfone with a V.N. of 48 ml / g (ISO 1628, NMP, 25°C); Tg = 225°C

[0185] PESU 3: Polyethersulfone with a V.N. of 56 ml / g (ISO 1628, NMP, 25°C); Tg = 225°C

[0186] PESU 4: Polyethersulfone with a V.N. of 66 ml / g (ISO 1628, NMP, 25°C); Tg = 226°C

[0187] PESU-Copolymer 1: with a V.N. of 55 ml / g (ISO 1628, Phenol / ODCB 1 / 1, 25°C) and a

[0188] Tg of 215 °C The PESU-Copolymer 1 was prepared as follows:

[0189] In a 4-liter glass reactor fitted with a thermometer, a gas inlet tube and a Dean-Stark- trap, 574.32 g (2.00 mol) of DCDPS, 475.49 g (1.90 mol) DHDPS, 22.83 g (0.1 mol) Bisphenol A and 304.04 g (2.20 mol) of potassium carbonate with a volume average particle size of 32.6 pm were suspended in 950 ml NMP in a nitrogen atmosphere. The mixture was heated to 190°C within one hour. In the following, the reaction time shall be understood to be the time during which the reaction mixture was maintained at 190°C. The water that was formed in the reaction was continuously removed by distillation, losses in NMP were replenished. After a reaction time of 5 hours, the reaction was stopped by the addition of 1500 ml NMP and cooling down to 130°C. Then methylchloride was added for 45 minutes, then the suspension was stripped with Nitrogen. After cooling down to room temperature, the potassium chloride formed in the reaction was removed by filtration. The obtained polymer solution was precipitated in water, the resulting polymer precipitate was separated and then extracted with hot water (85°C) for 20 h. Then the precipitate was dried at 120°C for 24 h at reduced pressure (< 100 mbar). The obtained beads were then granulated by melting in an ZSK 16 extruder at a barrel temperature of 350°C and 3 kg / h throughput. The V.N. of the PESLI Copolymer 1 was 55 ml / g, the Tg 215°C.

[0190] Component (P2)

[0191] Phenoxy PKHH: Polyether based on Bisphenol A and Epichlorohydrin, Tg = 92°C (Huntsman)

[0192] The blends of components (P1) and (P2) were prepared on a ZSK 25 twin screw extruder operating at a barrel temperature of 320 to 330°C, a throughput of 10 kg / h at 300 rpm. The composition and properties of the compounds are summarized in table 1.

[0193] The blends were then extruded into films using a single screw extruder operating at a melt temperature of 325°C up to 360°C, depending on the melt viscosity of the samples, feeding a slit-die. During the trials, the film thickness was monitored and continuously decreased from 100 pm until no stable operation was possible.

[0194] Table 1

[0195] The sandwich panels were prepared by laminating the foam core layer (FCL) in between two film layers (F1 and F2) and the upper top layer (UTL) and the lower top layer (LTL) in a heated press at 222°C for 10 minutes.

[0196] The obtained sandwich panels were then evaluated visually and sandwich panels without adhesion between the top layers and the foam core were sorted out.

[0197] The remaining sandwich panels were tested in a 3-point bending test. The fractured sandwich panels were evaluated regarding the adhesion between the layers (adhesive fracture / cohesive fracture). The results are summarized in table 2.

[0198] Table 2 o: weak adhesion no adhesion good adhesion

Claims

Claims1. Blend comprising as components(P1) at least one polyarylene ether sulfone polymer with a viscosity number (VN) between 45 to 58 ml / g, measured according to ISO 1628, and(P2) at least one phenoxy polymer, wherein the blend comprises component (P1) in an amount in the range of 85 to68 wt.% and component (P2) in an amount in the range of 15 to 32 wt.%, wherein the wt.% values are in each case based on the total weight of the blend.

2. Film made from the blend according to claim 1.

3. Film according to claim 2, wherein the film has a thickness in the range of 15 to80 pm.

4. Film according to claim 2 or 3, wherein the at least one polyarylene ether sulfone polymer (component P1) is obtained by converting a reaction mixture (RG) comprising as components:(A1) dihalogen component comprising not less than 80 wt.% of at least one dihalogen compound selected from the group consisting of 4,4’-dichlorodiphenyl sulfone and 4,4’-difluorodiphenyl sulfone, based on the total weight of component (A1) in the reaction mixture (RG),(B1) dihydroxy component comprising not less than 80 wt.% of at least one dihydroxy compound selected from the group consisting of 4,4’-dihydroxy diphenyl sulfone, bisphenol A, 4,4’-dihydroxy biphenyl and hydroquinone, based on the total weight of component (B1) in the reaction mixture (RG).

5. Use of a film according to any of claims 2 to 4 as an adhesive layer for joining a foam core layer (FCL) with a fiber reinforced top layer (TL).

6. Sandwich panel comprising an upper top layer (UTL) comprising at least one polyarylene ether sulfone polymer and at least one fiber reinforcement,a foam core layer (FCL) comprising at least one polyarylene ether sulfone polymer, and a lower top layer (LTL) comprising at least one polyarylene ether sulfone polymer and at least one fiber reinforcement, wherein the upper top layer (UTL) is joined with the foam core layer (FCL) via a first film (F1), wherein the first film (F1) is a film according to any of claims 2 to 4, the lower top layer (LTL) is joined with the foam core layer (FCL) via a second film (F2), wherein the second film (F2) is a film according to any of claims 2 to 4.

7. The sandwich panel according to claim 6, wherein the blend comprised in the first film (F1) has a glass transition temperature Tg at least 5K below the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the upper top layer (UTL) and the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the foam core layer (FCL).

8. The sandwich panel according to claim 6 or 7, wherein the blend comprised in the second film (F2) has a glass transition temperature Tg at least 5K below the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the lower top layer (LTL) and the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the foam core layer (FCL).

9. The sandwich panel according to any of claims 6 to 8, wherein the at least one polyarylene ether sulfone polymer comprised in the upper top layer (UTL), the at least one polyarylene ether sulfone polymer comprised in the foam core layer (FCL), the at least one polyarylene ether sulfone polymer comprised in the lower top layer (LTL), the at least one polyarylene ether sulfone polymer comprised in the first film (F1), and the at least one polyarylene ether sulfone polymer comprised in the second film (F2) are each independently from each other at least one polymer selected from the group consisting of polysulfone (PSU), polyethersulfone (PESU) and polybiphenyl sulfone (PPSU).

10. The sandwich panel according to any of claims 6 to 9, wherein the upper top layer (UTL), the foam core layer (FCL), the lower top layer (LTL), the first film (F1), and the second film (F2) each comprise the same polyarylene ether sulfone polymer.

11. The sandwich panel according to any of claims 6 to 10, wherein the foam core layer (FCL) has a density in the range of 25 to 200 kg / m3.

12. A process for the production of a sandwich panel according to any of claims 6 to 11 comprising the steps: i) providing the upper top layer (UTL) comprising at least one polyarylene ether sulfone polymer and at least one fiber reinforcement, the foam core layer (FCL) comprising at least one polyarylene ether sulfone polymer, the lower top layer (LTL) comprising at least one polyarylene ether sulfone polymer and at least one fiber reinforcement, ii) placing the first film (F1), wherein the first film (F1) is a film according to any of claims 2 to 4, between the upper top layer (UTL) and the foam core layer (FCL), iii) placing the second film (F2), wherein the second film (F2) is a film according to any of claims 2 to 4, between the lower top layer (LTL) and the foam core layer (FCL), to obtain a sandwich comprising starting from the upper top layer (UTL) layers in the following order: upper top layer (UTL), first film (F1) foam core layer (FCL), second film (F2), and lower top layer (LTL), and iv) heating the sandwich obtained in step iii) to a temperature at most 1K below the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the upper top layer (UTL) and the glass transition temperature Tg of the at least one polyarylene ether sulfone polymer comprised in the foam core layer (FCL) and the glass transition temperature Tg of the lower top layer (LTL).

13. The sandwich panel obtained by process according to claim 12.

14. The use of the sandwich panel, according to any of claims 6 to 11 and 13 as construction part for aviation industry, or for the construction of rotor blades for wind turbines.

15. Process for the re-use of the sandwich panel according to any of claims 6 to 11 and 13 at the end of its first application comprising the steps: a) crushing the sandwich panel to obtain a ground material b) using the ground material obtained in step a) to produce new products.

16. Granulate made from the blend according to claim 1.

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