WO2024100410A1

WO2024100410A1 - Improvements relating to the extrusion of polymeric material

Info

Publication number: WO2024100410A1
Application number: PCT/GB2023/052938
Authority: WO
Inventors: Kyri CHRISTODOULOU
Original assignee: Victrex Manufacturing Limited
Priority date: 2022-11-11
Filing date: 2023-11-10
Publication date: 2024-05-16
Also published as: GB202216862D0

Abstract

Improvements Relating to the Extrusion of Polymeric Material An extruded product comprising a first layer and a second layer, such as film, pipe or cable / wire sheath. The first layer comprises a polymeric material (A) having a repeat unit of formula: -O-Ph-O-Ph-CO-Ph- I and a repeat unit of formula: -O-Ph-Ph-O-Ph-CO-Ph- II wherein Ph represents a phenylene moiety. The second layer may be a polyaryletherketone (PAEK) such as a polyetheretherketone (PEEK). The first layer is intended to reduce the formation of deposits on a die of an extrusion apparatus during extrusion of the product. A method of producing a product comprising a first layer and a second layer and a use of a polymeric material (A) for reducing the formation of deposits on a die of an extrusion apparatus during extrusion of a second polymeric material are also described.

Description

Improvements Relating to the Extrusion of Polymeric Material

Field

The present invention relates to an extruded product, a method of producing an extruded product and the use of a polymeric material. In particular the present invention relates to an extruded product which reduces the formation of deposits on a die of an extrusion apparatus during extrusion.

Background

Elongate products with a specific, consistent cross section profile (referred to herein as extruded products), for example films or pipes, may be formed using extrusion processes. Typical extrusion processes involve forcing one or more flowable polymeric materials through an extrusion die. Such dies comprise an exit for the polymeric material which is shaped to impart the desired cross section profile on the product. Some polymeric materials have a tendency to adhere of the edges of the die exit and gradually form significant deposits on the die exit. These deposits may be referred to as “die drool” (also known as “die build-up”, “die drip”, “die peel”, “die bleed”, or “plate out”) and adversely affect the quality of the product and process, for example by marking the surface of the extruded product or by breaking off at random intervals and contaminating the product.

Manually removing such die drool from the die during the process is often difficult or impossible without impacting on the extruded product being formed. Therefore, when such die drool forms and starts to negatively impact the quality of the product, the process may have to be stopped and the extrusion apparatus, in particular the die, cleaned. This may involve dismantling the extrusion apparatus and therefore a significant amount of down time for the production process.

For these reasons, polymeric materials which have a relatively high tendency to form die drool may only be used to produce extruded products in relatively short product runs, which is inefficient and therefore more costly than processes using polymeric material with a lower tendency to form die drool.

This problem may be exacerbated when the polymeric material comprises a filler material, for example a particulate filler such as talc. Such filler materials often cause an increase in the formation of die drool. Such filler materials can provide benefits to extruded products formed from polymeric materials, such as improved strength, rigidity, impact resistance, heat resistance, electrical insulation and chemical stability. The benefits offered by such filler materials may outweigh the difficulties caused by the increased die drool. However, it would be desirable to reduce die drool in the production of extruded products using such polymeric materials comprising fillers so that the efficiency of the process and the quality of the extruded products can be improved. This problem may also be exacerbated when the extrusion apparatus is operating at an increased line speed. When line speed is increased, the pressure in the die increases from the faster extrusion screw speed and this may result in more swelling of the melt on exit from the die thus increasing die drool. It would be desirable to reduce die drool in the production of extruded products to enable to use of faster line speeds.

Summary of the Invention

Polyaryletherketones (PAEKs) such as poly etheretherketone (PEEK) and polyetherketone (PEK) are well known high performance thermoplastic polymers which have excellent mechanical and chemical resistance properties, in general. Filler materials such as glass fibres, carbon fibres and particulates such as talc may further improve certain properties of these polymers. However, the inventors have found that filler materials present in such polymers increase the tendency for die drool formation and therefore adversely affect extruded products formed from such filled PAEK polymers and reduce the efficiency of their production process.

It is one aim of the present invention, amongst others, to provide an extruded product, method or use that addresses at least one disadvantage of the prior art, whether identified here or elsewhere, or to provide an alternative to existing extruded products, methods and uses. For instance, it may be an aim of the present invention to provide an extruded product which has a lower tendency for producing die drool during extrusion than comparable extruded products.

According to aspects of the present invention, there is provided an extruded product, a method and a use as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and from the description which follows.

According to a first aspect of the present invention, there is provided an extruded product comprising a first layer and a second layer; wherein the first layer comprises a polymeric material (A) having a repeat unit of formula:

-O-Ph-O-Ph-CO-Ph- I and a repeat unit of formula:

-O-Ph-Ph-O-Ph-CO-Ph- II wherein Ph represents a phenylene moiety.

By extruded product we mean an elongate product with a cross section which has been formed by an extrusion process, suitably by extrusion through a die which imparts a specific, preferably consistent, cross section profile onto the product. The extruded product of this first aspect may be alternatively referred to as an elongate product, suitably having a consistent cross section. Examples of such extruded products I elongate products include films, cable outers, including but not limited to wire and cable insulation, pipes and filaments.

The polymeric material (A) is a polyaryletherketone (PAEK) polymer. More specifically, the polymeric material (A) is a copolymer of poly(ether ether ketone) (PEEK) and poly(ether diphenyl ether ketone) (PEDEK), the repeat units of formula I (which may be referred to as EEK) providing the PEEK polymer component and the repeat units of formula II (which may be referred to as EDEK) providing the PEDEK. Therefore, the polymeric material of formula (A) may be referred to as a PEEK/PEDEK copolymer.

The inventors have found that the polymeric material (A) has a low tendency for forming die drool when extruded through a die at elevated temperatures. Therefore, extruded products can be formed from the polymeric material (A) without the adverse effects on the product quality and process efficiency caused by die drool, as discussed above, which may be suffered when extruding similar polymers such as PEEK homopolymers. In the extruded product of this first aspect, the polymeric material (A) provides a first layer which is an outer layer with a reduced tendency for die drool which can in-effect protect the second layer, which is an inner layer, from the die on exit from the extrusion apparatus used to produce the extruded product so that the second layer does not produce the die drool which could adversely affect the quality of the product or the efficiency of the process. This is of course particularly advantageous when the material of the second layer, suitably a second polymeric material, has a much higher tendency for producing die drool than the polymeric material (A). As a result, the extruded product of this first aspect suitably has fewer defects caused by die drool than a comparable extruded product which does not comprise an outer layer of polymeric material (A). Also, the extrusion process used to form the extruded product may have a significantly longer run time than a comparable process which does not include the use of an outer layer of polymeric material (A), before the process needs to be stopped for cleaning the extrusion apparatus. This suitably provides a more efficient overall process for the production of such extruded products, such as films, cable outers, filaments and pipes.

As described in more detail below, the present invention may also allow higher levels of filler to be included in a polymeric material of the inner layer of the extruded product than would otherwise be possible without the filler adversely affecting the extrusion process. Such higher levels of filler may be desirable for improving the properties of the extruded product, for example the electrical corona discharge resistance.

Furthermore, the present invention may also allow for higher line speeds to be used in the production of the extruded product. Increasing line speed can cause die drool, which makes it impractical to increase line speed above a certain limit. However, as the present invention reduces die drool it is possible to achieve faster line speeds, increasing manufacturing output and efficiency. The use of the polymeric material (A) in the first layer as the outer layer in the extruded product may also provide other advantages in the reduction of other surface defects or strain-related phenomena which may occur on extrusion of some polymeric materials, for example crazing of the surface of the extruded material. The polymeric material (A) suitably has a much lower tendency to suffer such defects.

The first layer is an outer layer of the extruded product. The term “outer layer” is used herein to denote the layer or layers of the extruded product which contact the die used to form the product as the product exits the die. In some embodiments, the extruded product is formed by a process which involves only one surface of the product contacting the die on exit. In such embodiments, the first layer is suitably the only outer layer of the extruded product, typically the outermost layer or surface of the extruded product. The second layer is an inner layer of the extruded product. In some embodiments, the extruded product is formed by process in which two surfaces of the product contact the die on exit. In such embodiments, the extruded product comprises a third layer and the second layer is arranged between the first layer and the third layer. In this embodiment, the extruded product suitably has only two outer layers, typically the first layer is a first outer later being the outermost layer or surface of the extruded product and the third layer is a second outer layer being the innermost layer or surface of the extruded product.

The terms “outer layer” or “first outer layer” may be used interchangeably with the term “first layer”. The term “inner layer” may be used interchangeably with the term “second layer”. The term “second outer layer” may be used interchangeably with the term “third layer”.

Typically, the polymeric material (A) will have end units of the polymer which may be the same as the repeat units, but with a terminal OH or F group. However, the process for forming the polymer may include a separate end-capping step at completion of polymerisation, in which case separate a monomer or reagent may be added as an end-capping agent so that the end units may differ from the repeat units of the polymer. Such end-capping is well known in the field of nucleophilic polycondensation reactions.

The polymers preferably contain repeat units I and II in the molar proportions l:ll of from 95:5 to 50:50 or from 90:10 to 60:40.

The polymeric material (A) is suitably semi-crystalline and generally has a crystalline melting point which is below that of the homopolymer of repeating unit I or the homopolymer of repeating unit II. However, the glass transition temperature of the polymeric material (A) is generally the same as, or slightly higher than, the glass transition temperature of the homopolymer of repeating unit I. More specifically, the polymeric material (A) suitably has a glass transition temperature of greater than 143°C and up to 160°C, and a crystalline melting temperature of 300°C and up to 330°C. In particular, a polymer containing repeating units I and II in the relative proportions of 80:20 has a glass transition temperature of about 149°C and a crystalline melting temperature of about 309°C. The phenylene moieties (Ph) in each repeat unit may independently have 1 ,4- para linkages to atoms to which they are bonded or 1 ,3- meta linkages. Where a phenylene moiety includes 1 ,3- linkages, the moiety will be in the amorphous phase of the polymer. Crystalline phases will include phenylene moieties with 1 ,4- linkages. In many applications it is preferred for the polymeric material to be highly crystalline and, accordingly, the polymeric material preferably includes high levels of phenylene moieties with 1 ,4- linkages.

Suitably at least 95% or at least 99%, of the number of phenylene moieties (Ph) in the repeat unit of formula I have 1 ,4-linkages to moieties to which they are bonded. It is especially preferred that each phenylene moiety in the repeat unit of formula I has 1 ,4- linkages to moieties to which it is bonded.

Suitably at least 95% or at least 99%, of the number of phenylene moieties (Ph) in the repeat unit of formula II have 1 ,4-linkages to moieties to which they are bonded. It is especially preferred that each phenylene moiety in the repeat unit of formula II has 1 ,4- linkages to moieties to which it is bonded.

Preferably, the phenylene moieties in repeat unit of formula I are unsubstituted. Preferably, the phenylene moieties in repeat unit of formula II are unsubstituted.

The repeat unit of formula I suitably has the structure la:

The repeat unit of formula II suitably has the structure Ila:

The polymeric material (A) may include at least 68 mol%, preferably at least 71 mol% of repeat units of formula I. Particular advantageous polymeric materials (A) may include at least 72 mol%, or, especially, at least 74 mol% of repeat units of formula I. The polymeric material (A) may include less than 90 mol%, suitably 82 mol% or less of repeat units of formula I. The polymeric material (A) may include 68 to 82 mol%, preferably 70 to 80 mol%, more preferably 72 to 77 mol% of units of formula I.

The polymeric material (A) may include at least 10 mol%, preferably at least 18 mol%, of repeat units of formula II. The polymeric material (A) may include less than 32 mol%, preferably less than 29 mol% of repeat units of formula II. Particularly advantageous polymeric materials (A) may include 28 mol% or less; or 26 mol% or less of repeat units of formula II. The polymeric material (A) may include 18 to 32 mol%, preferably 20 to 30 mol%, more preferably 23 to 28 mol% of units of formula II. The sum of the mol% of units of formula I and II in the polymeric material (A) is suitably at least 95 mol%, is preferably at least 98 mol%, is more preferably at least 99 mol% and, especially, is about 100 mol%.

The ratio defined as the mol% of units of formula I divided by the mol% of units of formula II may be in the range 1 to 10, may be 1 .8 to 5.6, is suitably in the range 2.3 to 4 and is preferably in the range 2.6 to 3.3.

The polymeric material (A) suitably has a lower melting temperature (Tm) than the material of the inner layer, as determined by differential scanning calorimetry (DSC). The polymeric material (A) may have a melting temperature at least 10°C, such as at least 20°C, for example at least 30°C lower than the material of the inner layer.

Further suitable polymeric materials of formula (A) (PEEK/PEDEK copolymers) are as described in US 4717761 , WO 2014/207458 A1 and WO 2015/124903 A1 , the contents of which are incorporated herein by reference.

WO 2014/207458 A1 discloses PEEK/PEDEK copolymers, which have repeat units of formula I and II in a molar proportion from 55:45 to 95:5 and with melt viscosity (MV) measured at 340°C and 1000s^-1 shear rate of at least 0.25 and less than 1 .2 kNsm^-2.

WO 2015/124903 A1 discloses PEEK/PEDEK copolymers which have repeat units of formula I and II in a molar ratio from 55:45 to 95:5 and an MV of at least 0.25 and less than 1 .2 measured at 340°C and at 1000s^-1 shear rate.

In some embodiments, the polymeric material (A) may be as described in WO 2022013520 A1 , the contents of which are incorporated herein by reference. In such embodiments, the polymeric material (A) may consist essentially of repeat units of formula I:

-O-Ph-O-Ph-CO-Ph- I; repeat units of formula Ila:

and end units; wherein the molar ratio of repeat units of formula I to repeat units of formula Ila is from 50:50 to 95:5; and wherein the repeat units of formula I consist essentially of 50 to 90 molar % of repeat units of formula la:

and 10 to 50% molar % of repeat units which are of formula lb, of formula Ic or of a mixture thereof; wherein the repeat unit of formula lb is:

lb; and the repeat unit of formula Ic is:

Ic.

Preferably, the molar ratio of repeat units of formula I to repeat units of formula II is from 50:50 to 95:5, preferably from 60:40 to 90:10, more preferably from 70:30 to 90:10.

The repeat units of formula I consist essentially of, or preferably consist of, 50 to 90 molar% of repeat units of formula la in combination with 10 to 50 molar% of repeat units of formula lb and/or formula Ic. Preferably the repeat units of formula I consist essentially of, or preferably consist of, 65 to 90% molar% of repeat units of formula la in combination with 10 to 35 molar% of repeat units which are of formula lb, of formula Ic, or of a mixture thereof. More preferably, the repeat units of formula I consist essentially of, or preferably consist of, 80 to 90% molar% of repeat units of formula la in combination with 10 to 20 molar% of repeat units which are of formula lb, of formula Ic, or of a mixture thereof.

The repeat units la are referred to as RPEEK, the repeat units lb are referred to as RmPEEK and the repeat units Ic are referred to as ROPEEK.

So, in other words, the repeat units of formula I have, expressed as molar proportions: RPEEK:( RmPEEK + ROPEEK) from 90:10 to 50:50, preferably from 90:10 to 65:35, more preferably from 90:10 to 70:30, more preferably 90:10 to 80:20.

In a particularly preferred embodiment, the polymeric material (A) is a copolymer as described above wherein the molar ratio of repeat units of formula I to repeat units of formula II is from 90:10 to 70:30 and wherein the repeat units of formula I consist essentially of, or preferably consist of, 80 to 90 molar% of repeat units of formula la in combination with 10 to 20 molar% of repeat units which are of formula lib, of formula Ic, or of a mixture thereof.

It will be understood that formula I: -O-Ph-O-Ph-CO-Ph- provides no information concerning whether the ether linkages on the -O-Ph-O- moiety are arranged in para-, meta- or ortho- configuration, whereas this is specified for formulae la, lb and Ic, as are all other configurations within the repeat units.

In one embodiment, the copolymer according to the first aspect of the invention may be a copolymer which does not include repeat units of formula lb.

In another embodiment, the copolymer according to the first aspect of the invention may be a copolymer which does not include repeat units of formula Ic.

Suitably the polymeric material (A) provides up to 100 wt% of the outer layer, suitably up to 95 wt% or up to 90 wt% of the outer layer. The polymeric material (A) may provide at least 70 wt%, at least 80 wt% or at least 85 wt% of the outer layer. Suitably the polymeric material (A) provides from 70 to 100 wt% of the outer layer, from 80 to 95 wt% or from 85 to 95 wt% of the outer layer.

Suitably the first layer consists essentially or consists of the polymeric material (A) as defined above.

The first layer and the second layer of the extruded product may have a combined thickness of up to 5 mm, suitably up to 3 mm or up to 2 mm. Suitably the first layer and the second layer of the extruded product may have a combined thickness of at least 10 pm, suitably at least 50 pm or at least 100 pm.

The thickness of the first layer is suitably lower than the thickness of the second layer. The second layer may provide from 50 to 95% of the combined thickness of the first and second layers. The first layer suitably provides from 5 to 50% of the combined thickness of the first and second layers.

Suitably the extruded product of this first aspect comprises a third layer. The third layer is a second outer layer. In such embodiments, the first layer referred to above may be considered to be a first outer layer. Suitably the second layer is arranged between the first layer and the third layer. Therefore the extruded product suitably has an A-B-A sandwich type structure, with the A layers being the first and second outer layers and the B layer being the inner layer. Suitably the third layer comprises a polymeric material (A) as described above, i.e. a polymeric material (A) having a repeat unit of formula:

-O-Ph-O-Ph-CO-Ph- I and a repeat unit of formula:

-O-Ph-Ph-O-Ph-CO-Ph- II wherein Ph represents a phenylene moiety.

Suitably the third layer consists essentially or consists of the polymeric material (A) as defined above. Suitably the third layer is the same as the first layer.

The first layer and/or third layer may comprise a release agent. Suitably the first layer comprises a release agent. Suitable release agents are known in the art and may be selected from metal stearates, erucamide, oleamide or a fluoropolymer.

The second layer of the extruded product of this first aspect may comprise a polymeric material, which may be referred to as a second polymeric material. Suitably the second layer comprises a polyaryletherketone (PAEK). Suitably the second layer comprises a PEEK polymer, i.e. a polymeric material (B) having a repeat unit of formula:

-O-Ph-O-Ph-CO-Ph- I wherein Ph represents a phenylene moiety.

Suitably at least 95%, or at least 99%, of the number of phenylene moieties (Ph) in polymeric material (B) have 1 ,4-linkages to moieties to which they are bonded. It is especially preferred that each phenylene moiety in polymeric material (B) has 1 ,4- linkages to moieties to which it is bonded.

Suitably the phenylene moieties in repeat unit of formula I are unsubstituted.

The polymeric material (B) may include at least 68 mol%, preferably at least 71 mol%, of repeat units of formula la:

Suitably the polymeric material (B) includes at least 80 mol%, preferably at least 90 mol%, more preferably at least 95 mol%, especially at least 99 mol% of repeat units of formula I, especially those of formula la. Therefore, the polymeric material (B) is preferably a homopolymer, which is preferably a polyetheretherketone (PEEK).

Suitable PEEK polymeric materials are available from Victrex Manufacturing Ltd., for example VICTREX PEEK 150G, 151 G, 381 G, 450G, 650G (all of which are examples of a PEEK polymeric material). VICTREX AE™ 250 is an example of a PEEK-PEDEK polymeric material.

PAEKs, particularly including PEEK, can be manufactured by nucleophilic polycondensation of bisphenols with organic dihalide compounds in a suitable solvent in the presence of alkali metal carbonates and/or bicarbonates or alkaline earth metal carbonates and/or bicarbonates. Such processes are set out, for example, in EP0001879A, EP0182648A, EP0244167A and EP3049457A. PAEKs may be manufactured according to WO2018055384 which is incorporated herein by reference.

Such polyaryletherketones may have relatively high melting temperatures and may be susceptible to oxidation and other degradative processes during extrusion processes which may cause die drool as discussed above.

Suitably the second layer of the extruded product of this aspect comprises a filler material. The filler material may comprise at least 5 wt% of the second layer material, suitably at least 10 wt% or at least 15 wt% of the second layer. The filler material may provide up to 50 wt%, up to 40 wt% or up to 30 wt% of the second layer. Suitably the filler material provides from 5 to 50 wt% of the second layer, from 10 to 40 wt% or from 15 to 35 wt% of the second layer. The present invention may allow higher levels of filler, for example greater than 20 wt%, preferably 25wt%, or 30wt% or 40wt%, to be included in a polymeric material of an inner layer of an extruded product than would otherwise be possible without the filler adversely affecting the extrusion process. Such higher levels of filler may be desirable for improving the properties of the extruded product, for example the electrical corona discharge resistance.

In such embodiments, the second polymeric material, such as the polymeric material (B), suitably provides up to 95 wt% of the second layer material, suitably up to 90 wt% or up to 85 wt% of the second layer. The second polymeric material may provide at least 50 wt%, at least 60 wt% or at least 70 wt% of the second layer. Suitably the second polymeric material provides from 50 to 95 wt% of the second layer, from 60 to 90 wt% or from 65 to 85 wt% of the second layer.

The filler material may be a fibrous filler material or a particulate filler material.

Fibrous filler materials suitably have a longest dimension of 300 pm or less. Suitable fibrous filler materials may be selected from inorganic fibrous materials, organic fibrous materials, such as aramid fibres, and carbon fibre. Preferably, the melting temperature for the fibrous filler should be at least 450°C. Suitable fibrous filler materials may be selected from glass fibre, carbon fibre, asbestos fibre, silica fibre, alumina fibre, zirconia fibre, boron nitride fibre, silicon nitride fibre, boron fibre, fluorocarbon resin fibre and potassium titanate fibre, or mixtures thereof. Preferred fibrous fillers are glass fibre and carbon fibre.

In some embodiments, the filler material is a particulate filler material. Suitable particulate (or non- fibrous) filler materials may be selected from mica, silica, talc, alumina, kaolin, calcium sulfate, calcium carbonate, titanium oxide, ferrite, clay, glass powder, zinc oxide, nickel carbonate, iron oxide, quartz powder, boron nitride powder, magnesium carbonate, fluorocarbon resin, graphite, graphene, graphene oxide, carbon powder, ceramic powder, metal powder, flame retardant powder, nanotubes and barium sulfate, or mixtures thereof. Particulate filler materials may be introduced in the form of powder or flake particles. Suitably the particulate filler material is talc.

The particle size of the filler material is suitably in the range of from 1 to 10 pm, suitably from 2 to 5 pm. In some embodiments the filler material is in the form of platelets.

Preferably, the filler material has a D50 between 0.001 to 50 pm, more preferably from 0.005 to 15 pm. A preferred filler material has a D50 of less than 10 pm. Preferably, the filler material has a D50 of between 1 and 5 pm, for example between 3 and 5 pm. D50 is measured by laser Mastersizer laser diffraction, Mie theory (in accordance with ISO 13320-1).

Suitably the filler material provides the second layer material, for example a polymeric material (B) as defined above, with improved properties such as improved strength, ductility, heat resistance, chemical resistance or electrical resistance. For example, the filler material may provide an improvement in dielectric properties and/or electrical breakdown performance. In embodiments wherein the filler material is talc and the extruded product is a coating or sheath for a wire, the talc filler suitably improves the electrical breakdown properties of the wire coating at relatively high voltages, for example 800 V. Such a wire may be particularly suitable for use in electronic motors where a high voltage may be advantageous in reducing power losses.

As discussed above, the inclusion of such filler materials may lead to an increase in die drool and therefore detract from the quality of the extruded product and the efficiency of the production process. Therefore the extruded product of this first aspect may be particularly advantageous when the second layer, such as a polymeric material (B) as defined above, comprises such filler materials. In such embodiments, the extruded product suitably provides the beneficial properties of having the filler material in the bulk of the product (in the inner layer) whilst avoiding the associated tendency to form die drool on extrusion due by having the outer layer of polymeric material (A) covering the second layer.

The second layer material comprising a filler material may be prepared by any suitable method known in the art. Suitably the second layer material comprising the filler material is prepared by single or twin-screw extrusion compounding, preferably by twin-screw extrusion compounding. Suitably the second layer of the extruded product of this first aspect consists or consists essentially of the second polymeric material as defined above and any filler material which is present.

The first and/or second and/or third layers may comprise one or more pigments in order to alter the colour of the material. This can be useful in identification of the material during the manufacturing process. Optionally, the pigment may be TiO2 or carbon black.

In some embodiments of the extruded product of this first aspect, the extruded product is in the form of a film. Suitably the film comprises a first outer layer of polymeric material (A) as the first layer, an inner layer of polymeric material (B) as the second layer; and a second outer layer of polymeric material (A) as the third layer, wherein the second layer is arranged between the first and third layers (in an A-B-A arrangement). Suitably the second layer comprises the polymeric material (B) and a filler material as defined above. Suitably the first layer of polymeric material (A), the third layer of polymeric material (A) and the second layer of polymeric material (B) are arranged coaxially to form the film.

The film may have a total thickness of from 3 to 1 ,000 mm. The second layer suitably provides from 40 to 90% of the total thickness of the film. The first and/or third layers suitably provide from 5 to 30% of the total thickness of the film.

For end applications using films as a coating layer, for example, on wire for insulated conductors, then typical ranges would be in the region of sub-micron. To that end then the film may have a total thickness of from 3 to 1 ,000 pm. The second layer suitably provides from 40 to 90% of the total thickness of the film. The first and/or third layers suitably provide from 5 to 30% of the total thickness of the film.

In some embodiments of the extruded product of this first aspect, the extruded product is in the form of a pipe. Suitably the pipe comprises a first outer layer of polymeric material (A) as the first layer, an inner layer of polymeric material (B) as the second layer and a second outer layer of polymeric material (A) as the third layer, wherein the second layer is arranged between the first and third layers (in an A-B-A arrangement). Suitably the second layer comprises the polymeric material (B) and a filler material as defined above.

In such embodiments, the pipe may have a wall thickness of from 0.5 to 10 mm. The second layer suitably provides from 40 to 90% of the wall thickness of the pipe. The first and/or third layers suitably provide from 5 to 30% of the wall thickness of the pipe.

In such embodiments, the inclusion of polymeric material (A) may advantageously improve the physical properties of the pipe by reducing the adverse effects of die drool, particularly in pipes comprising a filler such as talc in the second (inner) layer which may otherwise have an increased tendency to form die drool. This may allow longer lengths of pipe to be produced than would otherwise be possible if die drool was produced to a greater extent. Also longer and faster run times may be possible by the reduction of die drool, providing an increase in manufacturing efficiency.

The pipe may have a length of at least 5 m, at least 10 m, at least 50 m or at least 100 m, suitably having a substantially constant cross-section along its entire length, suitably formed in a single continuous extrusion. In some embodiments, the pipe may have a length of at least 500 m, at least 1 km or at least 2.5 km.

The pipe may have an outside diameter of at least 0.5 cm, at least 2.5 cm. at least 10 cm or at least 15 cm. The pipe may have an outside diameter of less than 50 cm of less than 40 cm or less than 30 cm. In some embodiments the pipe has an outside diameter in the range from 0.5 cm to 50 cm. In some embodiment the pipe has an outside diameter in the range from 2.5 cm to 30 cm.

The outside diameter of a pipe may be defined as “d” cm and the thickness of the pipe wall may be defined as “t” cm. Accordingly the diameter to thickness ratio (d/t) can be defined for a pipe. In some embodiments the diameter to thickness ratio of the pipe is at least 6. The diameter to thickness ratio of the pipe may be in the range from 6 to 40 or from 15 to 40.

In some embodiments of the extruded product of this first aspect, the extruded product is in the form of a wire or cable sheath. Suitably the wire or cable sheath comprises an outer layer of polymeric material (A) as the first layer and an inner layer of polymeric material (B) as the second layer. Suitably the first layer of polymeric material (A) and the second layer of polymeric material (B) are arranged coaxially to form the wire or cable sheath. The wire or cable sheath may be extruded directly onto a wire or cable, to surround the cable or wire. Therefore, the extruded product may be considered to be a cable or wire assembly comprising an inner cable or wire and a sheath, wherein the sheath surrounds the wire or cable, the sheath comprising the first layer of polymeric material (A) and the second layer of polymeric material (B), as described above. In such embodiments, the second layer suitably comprises a filler material, suitably a particulate filler material, which provides increased electrical insulation to the second layer and therefore to the sheath as a whole. In such embodiments, the A-B arrangement of layers may be particularly suitable for the production of wires or cables wherein the wire or cable sheath exits an extruder in contact with the wire or cable being coated. The first layer of polymeric material (A) suitably reduces or prevents die drool formation from the upper surface of the second layer of polymeric material (B), which may otherwise be formed on the die as the polymeric material (B) exits the die of the extruder if the first layer of polymeric material (A) was not present. Die drool formation from the lower surface of the second layer of polymeric material (B) is suitably prevented by the second layer coming into direct contact with the wire or cable as it exits the extruder.

In some embodiments of the wire or cable sheath, the wire or cable sheath may comprise a first outer layer of polymeric material (A) as the first layer, an inner layer of polymeric material (B) as the second layer and a second outer layer of polymeric material (A) as the third layer, wherein the second layer is arranged between the first and third layers (in an A-B-A arrangement). Suitably the first layer of polymeric material (A), the third layer of polymeric material (A) and the second layer of polymeric material (B) are arranged coaxially to form the wire or cable sheath. The wire or cable sheath may be extruded directly onto a wire or cable. Therefore the extruded product may be considered to be a cable or wire assembly comprising an inner cable or wire and a sheath, the sheath comprising the first layer of polymeric material (A), the third layer of polymeric material (A) and the second layer of polymeric material (B), as described above. In such embodiments, the second layer suitably comprises a filler material, suitably a particulate filler material, which provides increased electrical insulation to the second layer and therefore to the sheath as a whole. In such embodiments, the A- B-A arrangement of layers may be particularly suitable for the production of wires or cables wherein the wire or cable sheath exits an extruder whilst not in contact with the wire or cable, and is subsequently brought into contact with the wire or cable. The two outer layers of polymeric material (A) suitably reduce or prevent die drool formation from both the upper and lower surfaces of the second (inner) layer of polymeric material (B), which may otherwise be formed as the polymeric material (B) exits the extruder if the two outer layers of polymeric material (A) were not present.

Suitably the second layer comprises talc, suitably platelets of talc having a particle size in the range of from 1 to 10 pm or from 2 to 5 pm.

As discussed above, such filler material may provide an improvement in dielectric properties and/or electrical breakdown performance, in particular an improvement in the electrical breakdown properties of the wire sheath at relatively high voltages, for example 800 V. In addition, such filler material may provide an improvement in resistance to corona discharge. in electrical machines. Such a wire may be particularly suitable for use in electronic motors where a high voltage may be advantageous in reducing power losses.

In such embodiments, the first layer and the second layer of the wire or cable sheath may have a combined thickness in the range from 50 to 300 pm, suitably in the range of from 100 to 200 pm. The first layer, second layer and third layer may have the same combined thickness.

The wire or cable within the wire or cable sheath may have a circular cross-section. In some embodiments, the wire or cable may have a rectangular, square, hexagonal or stranded crosssection. The cross-section of the wire or cable may have an area of from 1 mm² to 100 mm², suitably from 2 mm² to 80 mm² or from 2 mm² to 10 mm².

The thickness of the first and/or third layer is suitably lower than the thickness of the second layer of the wire or cable sheath. The second layer may provide from 50 to 95% of the combined thickness of the first and second layer or of the first, second and third layers. The first layer and/or third layer suitably provides from 5 to 50% of the combined thickness of the first and second layers or of the first, second and third layers. The wire or cable assembly may comprise a fourth layer arranged between the cable or wire and the second layer. The fourth layer may be an adhesive layer which suitably improves the adhesion of the sheath to the cable or wire.

In some embodiments of the extruded product of this first aspect, the extruded product is in the form of a filament. Such a filament may be useful as an input material for additive manufacturing. Suitably the filament comprises a first layer of polymeric material (A) and a second layer of polymeric material (B), wherein the second layer forms a core of the filament and the first layer surrounds the core. Suitably the first layer of polymeric material (A) and the second layer of polymeric material (B) are arranged coaxially to form the filament.

In such embodiments, the filament may have a thickness of from 0.2 to 5 mm, suitably from 1 .0 mm to 3.0 mm or from 1 . 5 to 2.0 mm. The second layer suitably provides from 50 to 95% of the thickness of the filament. The first layer suitably provides from 5 to 50% of the thickness of the filament.

Such a filament may advantageously include a filler as defined above in the core (i.e. second layer), for example electrically conductive fillers, which may otherwise cause die drool on extrusion in the absence of the outer (first) layer of polymeric material (A) which prevents the core contacting the surfaces of the die exit on extrusion from the die.

According to a second aspect of the present invention, there is provided a method of producing a product comprising a first layer and a second layer, the method comprising the steps of: a) providing a source of a polymeric material (A) having a repeat unit of formula:

-O-Ph-O-Ph-CO-Ph- I and a repeat unit of formula:

-O-Ph-Ph-O-Ph-CO-Ph- II wherein Ph represents a phenylene moiety; b) providing a source of a second polymeric material; c) delivering the polymeric material (A) and the second polymeric material to an extruding station comprising a die; d) extruding the polymeric material (A) and the second polymeric material through the die, such that the polymeric material (A) contacts an exit of the die during extrusion and the second polymeric material does not contact the die during extrusion, to form the extruded product. Suitably the steps of the method are carried out in the order steps a) and b) (suitably simultaneously) followed by step c) followed by step d).

Suitably the inputs and extrusion of the polymeric material (A) and the second polymeric material are arranged such that the second polymeric material is covered by the polymeric material (A) at the exit of the die so that the second polymeric material does not contact the exit of the die. Suitably the polymeric material (A) forms an outer layer surrounding the second polymeric material which forms an inner layer of the extruded product at or just prior to the exit of the die. Therefore, the polymeric material (A) prevents the second polymeric material from contacting the surface of the die at or near the exit of the die, in order to provide a reduction in die drool as described herein.

The polymeric material (A) may have any of the suitable features and advantages described above in relation to the first aspect.

The product produced by the method of this second aspect may have any of the suitable features or advantages of the extruded product described above in relation to the first aspect. The polymeric material (A) provided in step a) suitably provides the first layer of the extruded product described in relation to the first aspect. The second polymeric material provided in step b) suitably provides the second layer of the extruded product described in relation to the first aspect.

The second polymeric material provided in step b) may have any of the suitable features and advantages of the second layer material, i.e. the second polymeric material is suitably a polymeric material (B) as described in relation to the first aspect.

The method of this second aspect suitably causes a reduced amount of die drool compared with a comparable process wherein the second polymeric material is extruded through the die without the polymeric material (A) and therefore wherein the second polymeric material contacts the die, specifically the die exit, during extrusion. This method is therefore particularly advantageous when it is desired to produce an extruded product from a second polymeric material, for example a polymeric material (B) as described above which may comprise a filler material, which despite having advantageous properties causes die drool which adversely affects the quality of the product and lowers the efficiency of the production process due to the need for regularly stopping the process and removing the die drool deposits.

Furthermore, the method of the invention provides for higher line speeds to be used in the production of the extruded product. Increasing line speed can cause die drool, which makes it impractical to increase line speed above a certain limit. However, as the present invention reduces die drool it is possible to achieve faster line speeds, increasing manufacturing output and efficiency. Typically, an extrusion assembly may run at approximately 10 metres per minute. Advantageously, the present invention provides for line speeds of approximately 50 metres per minute or above. Preferably, line speeds may be less than 100 metres per minute, preferably between 30 and 80 metres per minute, preferably between 40 and 60 meters per minute,

Suitably the second polymeric material comprises a filler as described in relation to the first aspect. As discussed above, the presence of a filler material in a polymeric material may cause an increased formation of die drool.

The method of this second aspect may be carried out on a suitable extrusion apparatus comprising a first supply arrangement for feeding the polymeric material (A) in molten form to the extrusion die and a second supply arrangement for feeding the second polymeric material in molten form to the extrusion die such that the second polymeric material is extruded as an inner layer and the polymeric material (A) is extruded as an outer layer in the product (i.e. the first and second layers described herein).

Suitably step c) of the method involves delivering the polymeric material (A) to the extruding station comprising the die to provide a first outer layer of the product and a second outer layer of the product, the second polymeric material forming an inner layer arranged between the first and second outer layers (i.e. the first, second and third layers as described herein). This suitably involves an extrusion apparatus comprising a third supply arrangement for feeding a second stream of polymeric material (A) in molten form to the extrusion die, to provide the second outer layer of the product.

Suitably step d) is carried out at a temperature of at least 300°C, at least 320°C or at least 350°C. Suitably step d) is carried out at a temperature of up to 430°C, up to 400°C or up to 380°C.

Preferably when the polymeric material (B) is PEEK or PEEK and filler (for example, 30% talc filled PEEK) then suitably step (d) is carried out at a temperature greater than the melt temperature of the polymer material (B) and preferably at least 350 degrees Celsius.

Preferably step (d) is carried out at a temperature greater than the melt temperature of the polymer material (A) and preferably at least 325 degrees Celsius.

Suitably said temperatures are the temperature of the die during the method, suitably the temperature of the die exit during the method.

Suitably the method is carried out continuously for at least 1 hour, for at least 5 hours, for at least 10 hours, for at least 15 hours or for at least 24 hours. The reduction in die drool provided by the use of the polymeric material (A) suitably allows the run time of the method of producing the product by extrusion to be increased compared to a similar method wherein the polymeric material (A) is not used as a layer contacting the die exit. According to a third aspect of the present invention, there is provided a use of a polymeric material (A) for reducing the formation of deposits on a die of an extrusion apparatus during extrusion of a second polymeric material; wherein the polymeric material (A) has a repeat unit of formula:

-O-Ph-O-Ph-CO-Ph- I and a repeat unit of formula:

-O-Ph-Ph-O-Ph-CO-Ph- II wherein Ph represents a phenylene moiety.

The polymeric material (A) and the second polymeric material may have any of the suitable features and advantages described above in relation to the first and second aspects.

Suitably the reduction in the formation of deposits on a die of an extrusion apparatus during extrusion (die drool) provided by the use of this third aspect is as compared to a similar process whereby the same second polymeric material is extruded without the polymeric material (A). Suitably the use of this third aspect reduces the defects in the extruded product caused by die drool and I or lengthens the time the extrusion process can run before the process needs to be stopped and deposits on the die removed.

Typically, die drool deposits are carbonaceous and as such are electrically conductive which is a major disadvantage in the field of electrical insulation.

Suitably, in the use of this third aspect, the polymeric material (A) is arranged as an outer layer on the second polymeric material.

Brief Description Of The Drawings

For a better understanding of the invention, and to show how example embodiments may be carried into effect, reference will now be made to the accompanying drawings in which:

Figure 1 a is a schematic of an extrusion die for producing an extruded product of the first aspect of the present invention in the form of a cable or wire assembly using a method according to the second aspect of the present invention.

Figure 1 b is a cross section of extruded product produced by the extrusion process of Figure 1 a.

Figure 2a is a schematic of an alternative extrusion die for producing an extruded product of the first aspect of the present invention in the form of a cable or wire assembly using a method according to the second aspect of the present invention. Figure 2b is a cross section of extruded wire or cable sheath produced by the extrusion process of Figure 2a.

Figure 3a is a schematic of an alternative extrusion die for producing an extruded product of the first aspect of the present invention in the form of a cable or wire assembly using a method according to the second aspect of the present invention.

Figure 3b is a cross section of extruded wire or cable sheath produced by the extrusion process of Figure 3a.

Figure 4a is a schematic of an extrusion die for producing an extruded product of the first aspect of the present invention in the form of a pipe using a method according to the second aspect of the present invention.

Figure 4b is a cross section of extruded pipe produced by the extrusion process of Figure 4a.

Figure 5a is a schematic of an extrusion die for producing an extruded product of the first aspect of the present invention in the form of a film using a method according to the second aspect of the present invention.

Figure 5b is a cross section of extruded film produced by the extrusion process of Figure 5a.

Figure 6a is a schematic of an extrusion die for producing an extruded product of the first aspect of the present invention in the form of a filament using a method according to the second aspect of the present invention.

Figure 6b is a cross section of extruded filament produced by the extrusion process of Figure 6a.

Detailed Description Of The Example Embodiments

Figure 1 a shows a pressure extrusion die 100 used to produce an extruded wire or cable assembly in a “pressure on” extrusion process wherein the sheath contacts the wire or cable within the die. The extrusion die comprises a die body 1 and die mandrel 2. The die 100 comprises a first channel 101 , a second channel 102, a third channel 103 and a die exit 110. The first and second channels in use are supplied with molten polymeric materials A and B under pressure. The molten polymeric material A forms the first (outer) layer of the extruded product having the composition described above for polymeric material (A). The molten polymeric material B forms the second (inner) layer of the extruded product and is suitably a polymeric material (B) as described above.

Through the third channel is passed a wire or cable 3 for coating with a sheath of polymers A and B. A, B and 3 are fed through the die 100 to the die exit 110 wherein the polymeric material B contacts and coats the wire or cable 3 inside the die and then polymeric material A contacts and coats the polymeric material B, also inside the die body, to continuously produce an extruded product comprising the wire or cable 3 surrounded by a sheath having a first (outer) layer of A 111 and a second (inner) layer of B 112. This structure is shown in the cross section of Figure 1 b. The formation of this extruded wire or cable assembly is carried out with a reduced amount of die deposit formation (die drool) on the die exit 110 due to the polymeric material A having a lower tendency for forming such deposits than the second polymeric material B, which may advantageously contain a filler material. Such a filler material suitably improves the electrical breakdown resistance of the polymeric material B and therefore improves the electrical breakdown resistance of the wire or cable sheath. The outer layer of A in-effect insulates the polymeric material B from the hot exposed surfaces of the die 100, particularly at the die exit 110, which would otherwise cause the polymeric material B to produce die drool. Therefore, in this arrangement, the extrusion method and the extruded product suitably provide an advantageous reduction in die drool compared to similar processes and products.

Figure 2a shows an extrusion die 200 formed from die body 1 and die mandrel 2. The die 200 comprises comprising a first channel 201 , a second channel 202, a third channel 203, a fourth channel 204 and a die exit 210, used to produce an extruded wire or cable assembly in a “pressure on” extrusion process wherein the sheath contacts the wire or cable within the die. The first, second and third channels in use are supplied with molten polymeric materials A, B and C, respectively. These polymeric materials are fed under pressure through the die 200 to the die exit 210 to continuously produce an extruded product comprising three layers 211 , 212 and 213 arranged coaxially around wire 3 as shown in Figure 2b, the layers corresponding to polymeric material supplied to the channels 201 , 202 and 203, respectively.

As with the embodiment of Figure 1 a described above, through the third channel is passed a wire or cable 3 for coating with a sheath of polymers A, B and C. A, B, C and 3 are fed through the die 200 to the die exit 210 wherein the polymeric material B contacts and coats the wire or cable 3 inside the die, polymeric material C contacts and coats the polymeric material B and then polymeric material A contacts and coats the polymeric material C, also inside the die body, to continuously produce an extruded product comprising the wire or cable 3 surrounded by a sheath having an outer layer of A and inner layers of B and C.

The molten polymeric material A forms the outer layer of the extruded product and has the composition described above for polymeric material (A) i.e. the first layer as described herein. The molten polymeric material B forms an inner layer of the extruded product and is suitably a polymeric material (B) as described above for the second layer. The molten polymeric material C forms a second inner layer of the extruded product and may be a polymeric material (B) as described above. The polymeric material C suitably contains a fillerwhich improves the electrical breakdown resistance of the polymeric material C and therefore improves the electrical breakdown resistance of the wire or cable sheath. Suitably the polymeric material B provides an improved bonding between the polymeric material C and the wire 3 than would otherwise be achieved if polymeric material C contacted the wire 3 directly.

As described above in relation to Figure 1 a, the outer layer of A in-effect insulates the polymeric materials B and C from the hot exposed surfaces of the die 200, particularly at the die exit 210, which would otherwise cause the polymeric material B or C to produce die drool. Therefore this arrangement, the extrusion method and the extruded product suitably provide an advantageous reduction in die drool compared to similar processes and products.

Figure 3a shows die 300 formed from die body 1 and die mandrel 2. The die 300 has a similar arrangement of inputs to die 200 but is set up as a “tube-on” die to coat a wire or cable 3 with a sheath having a first outer layer of A 311 (i.e. the first layer), an inner layer of B 312 (i.e. the second layer) and a second outer layer of A 313 (i.e. the third layer). The coating of the wire or cable 3 with the sheath occurs outside the die body 300, after the sheath has exited the die through the die exit 310. Therefore in such a tube on process, both the outermost and innermost surfaces of the sheath contact the hot exposed surfaces of the die 300 at the die exit 310 and may therefore risk producing die drool. The wire or cable produced in this manner comprises three layers 311 , 312 and 313 arranged coaxially around wire 3 as shown in Figure 3b, the layers corresponding to polymeric material supplied to the channels 301 , 302 and 303, respectively. The formation of the sheath from polymeric materials A and B occurs inside the die body as shown so that the first and second outer layers of A in-effect insulate the polymeric material B from the hot exposed surfaces of the die 300, as discussed above, to reduce or eliminate die drool as the sheath exits the die. As with the embodiments described in relation to Figures 1 and 2, molten polymeric material A has the composition described above for polymeric material (A). The molten polymeric material B forms the inner layer of the extruded product and is suitably a polymeric material (B) as described above. The polymeric material B suitably contains a filler which imparts electrical breakdown resistance to the polymeric material (B).

Figure 4a shows an extrusion die 400 for the formation of a pipe, the die formed from die body 1 and die mandrel 2. The die 400 comprises a first channel 401 , a second channel 402, a third channel 403, a fourth channel 404 and a die exit 410. The first, second and third channels in use are supplied with molten polymeric material under pressure which are fed through the die 400 to the die exit 410 to continuously produce an extruded pipe product comprising three layers 411 , 412 and 413 as shown in Figure 4b, the layers corresponding to polymeric material supplied to the channels 401 , 402 and 403, respectively. The fourth channel 404 comprises a pin 3 to produce a hollow centre 414 of the pipe. The molten polymeric material supplied to the first channel 401 is a polymeric material (A) as described above. The molten polymeric material supplied to the second channel 402 is a second polymeric material as described above, for example a polymeric material (B) as described above. The molten polymeric material supplied to the third channel 403 is a polymeric material (A) as described above. Therefore the die 400 in use produces an extruded product comprising an inner layer of a second polymeric material (i.e. the second layer) arranged between two outer layers of polymeric material (A) (i.e. the first and third layers). The formation of this extruded product is carried out with a reduced amount of die deposit formation (die drool) on the die exit 410 due the polymeric material (A) having a lower tendency for forming such deposits than the second polymeric material, which may contain a filler material. The two outer layers of polymeric material (A) in-effect insulate the second polymeric material from the hot exposed surfaces of the die 400, particularly at the die exit 410, which would otherwise cause the second polymeric material to produce die drool. Therefore this arrangement, the extrusion method and the extruded product suitably provide an advantageous reduction in die drool compared to similar processes and products.

Figure 5a shows an extrusion apparatus 500 for producing an extruded film. The apparatus comprises a die body 1 and a co-extrusion feed block 2. The co-extrusion feed block 2 is provided with a first channel 501 , a second channel 502 and a third channel 503. The first and second channels in use are supplied with molten polymeric material A and the third channel is supplied with polymeric material B, under pressure. These polymeric materials are co-extruded through the co- extrusion feed block and then passed to the die 1 for shaping into a film with a desired thickness. The molten polymeric material A from channel 501 forms the first outer layer 511 of the film, the molten polymeric material A from channel 502 forms the second outer layer 512 and the molten polymeric material B from channel 503 forms the inner layer 513, as shown in Figure 5b.

As with the embodiments described above, only the outer layers of polymeric material A of the film contact the co-extrusion feed block 1 and the die 2 and therefore reduce die drool formation due to reduced tendency of polymeric material (A) to produce die drool.

Figure 6a shows a die 600 for producing a filament extruded product. The die 600 die is formed from die body 1 and die mandrel 2. The die 600 comprises a first channel 601 , a second channel 602 and a die exit 610. The first and second channels in use are supplied with molten polymeric materials A and B under pressure. The molten polymeric material A forms the outer layer 611 of the filament having the composition described above for polymeric material (A), and the molten polymeric material B forms the inner layer or core 612 of the filament, as shown in Figure 6b. The molten polymeric material B is suitably a polymeric material (B) as described above, and suitably comprises a filler material.

As with the embodiments described above, only the outer layer of polymeric material A of the filament contacts the hot exposed surfaces of the die 600 and therefore die drool formation is reduced due to lower tendency of polymeric material (A) to produce die drool than a polymeric material of composition (B), in particular when polymeric material B comprises a filler material. The filament produced in this manner may be useful as a feedstock material in additive manufacture. Examples

The following extruded products were produced in order to demonstrate the reduction in die drool which may be obtained by the present invention.

The methods involve process steps of polymer drying, followed by extrusion into solid form during which the die drool onset is compared for various polymers and configurations. The solid form examples include polymer filament, flat wire with a polymer coating, and coextruded round wire with multi-layer polymer coatings.

Polymer drying

Prior to extrusion, powder I pellets of each of the polymeric materials described below and used in the following methods were dried to less than 0.05% w/w moisture (dew point of -40°) by placing the material in an air circulating oven for a minimum of 3 hours at 150°C or for 2 hours at 160°C. For LMPAEK™ material, the preferred drying time was 2-3 hours at 120°C. To ensure the material is sufficiently dry, the moisture content may be measured according to ISO 15512 method (B) in accordance with ISO 1133. This drying is to prevent moisture causing voids in the extrudates following extrusion, due to the hygroscopicity of the polymeric materials in powder or pellet form.

It will be understood that reference to unfilled PEEK (Victrex 381 G) in any one of the examples below includes but is not limited to PEEK manufactured in accordance with WO2018055384.

Example Set 1 - Filament

Filaments formed of polymeric material were produced by continuous extrusion of the molten polymeric materials in order to assess the relative rates of die drool formation of these polymeric materials.

Example 1.1 - PEEK polymeric material manufactured by Victrex Manufacturing Limited under the name 381TL30 as defined herein comprising 30 wt% of a talc (JETFINE™ 3CA) filled material.

Example 1.2 - Unfilled PEEK material manufactured by Victrex Manufacturing Limited under the name 381 G.

Example 1.3 - PEEK/PEDEK copolymer manufactured by Victrex Manufacturing Limited as LMPAEK™ material in accordance with EP3013888.

Method of producing a filament

Filaments were produced by introducing the pre-dried polymeric material into a typical single screw extrusion line consisting of a heated extruder barrel having a screw with a number of zones: a feed zone, a compression zone, a metering zone, and a die zone, each having temperatures of between 300 and 390°C (see Table 1). The polymeric material was fed through the zones to produce a molten filament at the die zone exit. The molten filament was drawn away from the die and cooled below the melting point of the polymeric material to freeze the filament into its final form.

Table 1 : Zone Temperature (°C)

The extruder barrel internal diameter was between 15 mm and 50 mm with a screw having a length to diameter ratio (L/D) between 16:1 and 28:1 and preferably between 18:1 and 24:1 . The line speed was set from 8 to 8.5 m/min.

Typically, the screw speed was set to between 15 and 25 rpm. The screw speed may be varied within the range 3 to 50 rpm, preferably from 4 to 30 rpm and most preferably from 5 to 30 rpm. The line speed may be varied from 1 to 30 m/min, preferably 3 to 25 m/min and most preferably from 4 to 20 m/min.

The melt pressure during the extrusion was measured with a pressure transducer which can be placed at the end of the screw or within the die. The melt pressure may vary according to material type and speed but is typically within the range of 2 bar up to 500 bar.

The molten polymeric material passed through the extrusion line to flow through a die having a circular opening with a diameter of approx.4 mm. The molten material was drawn away from the die, cooled in air at ambient temperature until below the melting point of said material. The frozen filament was drawn to the desired thickness using a caterpillar type haul-off. A filament of approx. 1 .5 to 2mm, typically 1 ,7mm, was produced by this process.

The die opening may be varied in size and shape, for example the opening may have a diameter of from 0.2 to 8 mm and may have a square, rectangular or lobed profile, depending on the desired cross-section shape of the extruded product. The length of the die opening is suitably in the range of 0.1 to 6xthe diameter of the extruded filament, where the lead-in section is preferably smooth with a consistent change in diameter, but a stepped diameter change is also possible. Filaments were extruded through the extrusion line until die drool was visible around the die opening and said die drool began to adversely affect the quality of the extruded product. Such adverse effects on the quality of the extruded product include visible marks and defects in the surface of the extruded product. A thinning of the diameter of the extrudate material and a reduction in diameter or thickness of typically greater than 15% is detrimental to the product quality. An amount less than 15% is understood to be acceptable to those skilled in the field. In addition, carbonaceous die drool which detaches from the die and attaches to the extrudate likely has a detrimental impact on the quality of the final product. The time elapsed from the start of the extrusion until the point of detrimental die drool formation, is detailed in Table 2 for different polymeric materials.

Table 2

The results in Table 2 show the PEEK/PEDEK material provides a significant improvement in the time elapsed before die drool formation caused visible defects along the length of the extrudate compared to the use of the filled PEEK material, or PEEK alone. In so doing, the extrusion process of the present invention may be run for a prolonged period before the process must be stopped and the extrusion equipment cleaned. Advantageously, the process leads to a more efficient production process and subsequently a longer product length.

Example 2 - Coated copper wire

Coated wires were formed by extruding the polymeric materials described in Table 2 above as single layer onto a copper wire. Again, the process used a continuous extrusion of the molten polymeric material onto the wire to assess the relative rates of die drool formation of the polymeric materials.

The coated wires were extruded through a clean extrusion die until significant die drool was visible around the die opening and said die drool began to adversely affect the quality of the extruded product. Such adverse effects on the quality of the extruded product include visible marks and defects in the surface of the extruded product. The time elapsed from the start of the extrusion until the point of die drool formation, was recorded and is provided in Table 3 for the different polymeric materials. The coated wires were produced using the method and equipment described below. Method - coated wire

The coated wires were produced using an extrusion line with the barrel diameter ratios and line speeds as described above for Example 1. Typically, the screw speed was set to between 2 and 10rpm. In order to produce a coated wire, the extrusion line was configured with a crosshead die in which the polymeric molten material enters from a side of the line. Such a configuration allows the polymeric material to contact and form a sheath on a wire within the die. This type of extrusion process may be referred to as a “pressure on” or “pressure die” system. In this example, the wire was a copper wire having a rectangular cross-section. The wire is continually fed through the extrusion line and the polymeric material is extruded onto the wire in a continual process. The line speed was set from 8 to 8.5 m/min.

The cross-section shape of the wire may be varied, for example a square or rectangular shape. The rectangular wire may have an aspect ratio of up to 4:1 .

A gap between the uncoated wire and the die opening is typically between 50 micron and 300 micron. The final coated wire had a thickness of between 100-200 micron.

Table 3 below shows the results for the time to die drool.

Table 3

The results in Table 3 show that the use of the PEEK/PEDEK material as a single polymer layer on a wire, which contacts an extrusion die during an extrusion process, increases the time until significant die drool is produced and begins to adversely affect the quality of the extruded product. In contrast, filled and unfilled PEEK material show die drool forms more quickly than PEEK/PEDEK material. Therefore the use of PEEK/PEDEK enables the extrusion process to be continued for a longer period of time before needing to be stopped and the extrusion equipment cleaned. This may provide a more efficient production process and a longer extruded product.

Example 3 - Coextrusion on wire

Wires having an inner layer and outer layer coating of polymeric material as illustrated in Figures 1 a and 1 b were formed by extruding the polymeric materials noted in Table 4 below as the outer and inner layers onto a copper wire. Again, the process used a continuous extrusion of the molten polymeric material onto the wire in order to assess the relative rates of die drool formation of these polymeric materials.

Table 4

The coated wires were again extruded through a clean extrusion die, as described above in relation to Figures 1 a and 1 b, until die drool was visible around the die opening and said die drool began to adversely affect the quality of the extruded product. Such adverse effects on the quality of the extruded product include visible marks and defects in the surface of the extruded product. The time elapsed from the start of the extrusion until the point of die drool formation, causing quality defects as described above, was recorded, and is provided in Table 5 for the different polymeric materials. The coated wires were produced using the method and equipment described below.

The coated wires were produced using an extrusion line as described above with a second heated extruder barrel for the second polymeric material. The extrusion die used was of the type shown in Figure 1a configured for a “pressure on” extrusion process wherein the polymeric materials of the outer and inner layers forms a sheath on the wire within the die, with the outer layer contacting the die as the product exits and the inner layer contacts the wire in the product. The polymeric materials noted in Table 4 were extruded through the first and second channels 101 , 102 as previously described and as shown in the figures to form said outer and inner layers on the wire, respectively.

Table 5

The results in Table 5 show that a multilayer extruded product having a polymeric material (A) being a PEEK/PEDEK copolymer as claimed in the present invention as an outer layer coating which contacts a surface of an extrusion die on exit from said die, can significantly increase the time until die drool is produced and begins to adversely affect the quality of the extruded product, compared to a similar a filled or an unfilled PEEK material. Use of the PEEK/PEDEK material as the outer layer provided an approximately 12-fold improvement in the time elapsed before significant die drool formation compared to the use of the filled PEEK material as the outer layer.

Advantageously, the extrusion process for forming products comprising PEEK/PEDEK can be continued for a longer period of time before the process needs to be stopped and the extrusion equipment cleaned, which may provide a more efficient production process. Additionally, the process may be run at higher outputs or line speeds which would normally exacerbate die drool. Consequently, productivity is improved in addition to product quality. . Such extruded products can therefore be formed having an inner layer comprising a PEEK polymer and a filler material, without said polymer and filler material adversely affecting the process and product by the formation of excessive die drool.

It will be apparent to one skilled in the art that the benefits seen in the above Examples can also be applied to other wire coating embodiments and also to embodiments of multilayer films and pipes, as described herein and as illustrated in the Figures.

Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of other components. The term “consisting essentially of’ or “consists essentially of’ means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention. Typically, when referring to compositions, a composition consisting essentially of a set of components will comprise less than 5% by weight, typically less than 3% by weight, more typically less than 1 % by weight of non-specified components.

The term “consisting of’ or “consists of’ means including the components specified but excluding addition of other components.

Whenever appropriate, depending upon the context, the use of the term “comprises” or “comprising” may also be taken to encompass or include the meaning “consists essentially of’ or “consisting essentially of’, and may also be taken to include the meaning “consists of’ or “consisting of’.

For the avoidance of doubt, wherein amounts of components in a composition are described in wt%, this means the weight percentage of the specified component in relation to the whole composition referred to. For example, “the polymeric material (A) provides from 70 to 100 wt% of the outer layer’ means that 70 to 100 wt% of the outer layer is provided by polymeric material (A).

The optional features set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional features for each aspect or exemplary embodiment of the invention as set out herein are also to be read as applicable to any other aspect or exemplary embodiments of the invention, where appropriate. In other words, the skilled person reading this specification should consider the optional features for each exemplary embodiment of the invention as interchangeable and combinable between different exemplary embodiments.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1 . An extruded product comprising a first layer and a second layer; wherein the first layer comprises a polymeric material (A) having a repeat unit of formula:

-O-Ph-O-Ph-CO-Ph- I and a repeat unit of formula:

-O-Ph-Ph-O-Ph-CO-Ph- II wherein Ph represents a phenylene moiety.

2. The extruded product according to claim 1 , wherein the first layer is an outer layer and the second layer is an inner layer.

3. The extruded product according to claim 1 or 2, wherein the second layer comprises a filler material.

4. The extruded product according to any one of the preceding claims, wherein the filler material is a particulate filler material.

5. The extruded product according to any one of the preceding claims, wherein the second layer comprises a polymeric material (B) having a repeat unit of formula:

-O-Ph-O-Ph-CO-Ph- I wherein Ph represents a phenylene moiety.

6. The extruded product according to any one of the preceding claims, comprising a third layer; wherein the second layer is arranged between the first layer and the third layer; and wherein the third layer comprises a polymeric material (A) having a repeat unit of formula:

-O-Ph-O-Ph-CO-Ph- I and a repeat unit of formula:

-O-Ph-Ph-O-Ph-CO-Ph- II wherein Ph represents a phenylene moiety.

7. The extruded product according to any one of the preceding claims, wherein the first and/or third layers comprise a release agent.

8. The extruded product according to any one of the preceding claims, wherein the extruded product is in the form of a film.

9. The extruded product according to of claims 1 to 7, wherein the extruded product is in the form of a pipe or a cable outer/sheath.

10. The extruded product according to of claims 1 to 7, wherein the extruded product is in the form of a filament.

11 . The extruded product according to any one of the preceding claims, wherein the polymeric material (A) has repeat units of formula la:

la; and repeat units of formula Ila:

wherein at least 95 mol% of the repeat units are repeat units of formula la and of formula Ila; wherein the repeat units la and Ila have a molar ratio la: I la from 50:50 to 95:5.

12. The extruded product according to any one of claims 1 to 10, wherein the polymeric material (A) consists essentially of repeat units of formula I:

-O-Ph-O-Ph-CO-Ph- repeat units of formula Ila:

lb; and the repeat unit of formula Ic is:

13. A method of producing a product comprising a first layer and a second layer, the method comprising the steps of: a) providing a source of a polymeric material (A) having a repeat unit of formula:

-O-Ph-O-Ph-CO-Ph- I and a repeat unit of formula:

-O-Ph-Ph-O-Ph-CO-Ph- II wherein Ph represents a phenylene moiety; b) providing a source of a second polymeric material; c) delivering the polymeric material (A) and the second polymeric material to an extruding station comprising a die; d) extruding the polymeric material (A) and the second polymeric material through the die, such that the polymeric material (A) contacts the die during extrusion and the second polymeric material does not contact the die during extrusion, to form the extruded product.

14. The method according to claim 13, wherein the second polymeric material comprises a filler.

15. The method according to claim 13 or claim 14, wherein the method is carried out continuously for at least 5 hours, preferably for at least 10 hours.

16. Use of a polymeric material (A) for reducing the formation of deposits on a die of an extrusion apparatus during extrusion of a second polymeric material; wherein the polymeric material (A) has a repeat unit of formula:

-O-Ph-O-Ph-CO-Ph- I and a repeat unit of formula:

-O-Ph-Ph-O-Ph-CO-Ph- II wherein Ph represents a phenylene moiety.

17. The use of claim 16, wherein the polymeric material (A) is arranged as an outer layer on the second polymeric material.