WO2024100411A1

WO2024100411A1 - Improvements relating to the extrusion of polymeric material

Info

Publication number: WO2024100411A1
Application number: PCT/GB2023/052939
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: GB202216867D0

Abstract

The invention relates to an extruded product, particularly an insulated conductor assembly, comprising a conductor wire, a first extruded layer and a second extruded layer. The first layer comprises a polymeric material (A) having a repeat unit of formula (I) (Formula I) wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2. The second layer comprises a polymeric material (B) having a repeat unit of formula (I) (Formula I) wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2, together with a filler material. The second layer is located between the wire and the first layer.

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 insulated conductor assembly.

Background

Elongate products with a specific cross section profile (referred to herein as extruded products), for example insulated conductors, 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 to 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 die drool from the die during the process is often difficult or impossible without impacting on the extruded product being formed. 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 typically involves dismantling the extrusion apparatus, resulting in 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 production runs; this is inefficient and economically unfavourable.

Die drool can often increase when the polymeric material comprises a filler material, for example a particulate filler such as talc. Talc is known to be particularly advantageous for insulated conductors as described in WO2022/175515 as it helps to improve the adhesion of the polymer to the conductor wire. Therefore, it would be desirable to reduce die drool when making such conductors so that the efficiency of the process and the quality of the extruded product can be improved.

Die drool may also be exacerbated when the extrusion apparatus is operating at an increased line speed. Typically, when line speed is increased, pressure in the die increases due to the faster extrusion screw speed. This can lead to more swelling of the melt on exit from the die thus increasing die drool. As such, it would be desirable to reduce die drool in the production of extruded products to allow for faster line speeds.

It is one aim of the present invention, amongst others, to provide an insulated conductor assembly, together with a 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 insulated conductor which has a lower tendency for producing die drool during extrusion than comparable extruded products.

According to a first aspect of the present invention, there is provided an insulated conductor assembly comprising a conductor wire, a first extruded layer and a second extruded layer; said first layer comprising: a polymeric material (A) having a repeat unit of formula I

wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2; and said second layer comprising: a polymeric material (B) having a repeat unit of formula I

wherein t1 and wl independently represent 0 or 1 and v1 represents 0, 1 or 2, together with a filler material, wherein said second layer is located between the wire and the first layer.

Preferably the first layer comprises at least 50 wt% of the polymeric material (A), more preferably at least 75 wt%, more preferably at least 85 wt%, most preferably greater than 95wt%, for example 99wt%. Most preferably, the first layer consists essentially or consists of the polymeric material (A).

Preferably, the_polymeric material (A) comprises at least 40 wt% of PAEK polymer preferably at least 70 wt%, preferably at least 80 wt%. In a preferred embodiment, the polymeric material (A) is substantially at least 99wt% PAEK. Preferably the second layer comprises at least 50 wt% of the polymeric material (B), more preferably at least 75 wt%, more preferably at least 85 wt%, most preferably greater than 95wt%, for example 99wt%. Most preferably, the second layer consists essentially or consists of the polymeric material (B).

A preferred polymeric material (A) and/or (B) is polyether ether ketone (PEEK), wherein the repeat units are t1 =1 , v1 =0 and w1=0.

Alternatively, the polymer material may be a PAES polymer, for example, a polyphenylsulphone (PPSU) or polysulphone (PSU).

In a most preferred embodiment, the first layer consists essentially of PAEK, preferably PEEK, and the second layer consists essentially of polymeric material (B) being PAEK and filler material, preferably PEEK and filler material.

PAEK polymers or copolymers, unlike many conventional polymers, can be obtained in either amorphous or crystalline form as a direct result of the way that the polymer is treated. A glassy or amorphous state is achieved by rapidly quenching the polymer from the melt to below Tg, whereas slow-cooling the polymer from the melt will allow crystallinity to develop in the sample (melt crystallisation). The crystalline form of the polymer can also be obtained from the polymer in its amorphous state, for instance at room temperature, by heating it to a temperature higher than Tg but less than Tm (cold crystallisation) prior to cooling back to room temperature, or by holding the polymer at a constant temperature between Tg and Tm for a length of time (isothermal crystallisation) prior to cooling back to room temperature.

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. In an embodiment of the present invention, polymeric material (A) and/or polymeric material (B) may be a PAEK manufactured in accordance with EP3049457.

Preferably the or each polymeric material (A) and/or polymeric material (B) has a crystallinity of at least 10%, more preferably at least 20%, for example greater than 25%. However, for some applications a lower crystallinity such as less than 25% or less than 22% may be advantageous. Crystallinity is measured by a DSC to determine the onset of Tg by the intersection of the lines drawn along the pre-transition baseline and a line drawn along the greatest slope obtained during the transition. The Tn is measured as the temperature at which the main peak of the cold crystallisation exotherm reaches a maximum. The Tm is the temperature at which the main peak of the melting endotherm reached a maximum. The heat of fusion for melting (AHm) is obtained by connecting the two points at which the melting endotherm deviates from the relatively straight baseline. The integrated area under the endotherm as a function of time yields the enthalpy (mJ) of the melting transition: the mass normalised heat of fusion is calculated by dividing the enthalpy by the mass of the specimen (J/g). The level of crystallisation (X(%)) is determined by dividing the heat of fusion of the specimen by the heat of fusion of a totally crystalline polymer, which for polyether ether ketone is 130J/g. ISO 11357-1 to ISO 11357-4 describes the test methodology used to determine said measurements.

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 a preferred embodiment, the filler material is a particulate filler material. Suitable particulate (or non-fibrous) filler materials may be selected calcium sulphate, chromium oxide, glass fibre, iron oxide, magnesium carbonate, magnesium oxide, mica, silica, silicon carbide, silicon dioxide (quartz), silicon nitride, sodium silicate, titanium dioxide, talc (e.g. Jetfine™ including Jetfine 3CA), zinc oxide, zirconia, barium sulphate and boron nitride.

The filler material may comprise at least 5 wt% of the polymeric material (B) material, suitably at least 10 wt% or at least 15wt% thereof. The filler material may provide up to 50wt%, up to 40 wt% or up to 30 wt% of the polymeric material (B). Suitably the filler material provides from 5 to 50 wt% of the polymeric material (B), from 10 to 40wt% or from 15 to 35 wt% of the total composition of the polymeric material (B). For example, 15wt%, or 20wt% or 25wt% or 30wt% of filler material, for example talc or zinc oxide, may be present in the polymeric material (B). Most preferably, the polymeric material (B) comprises PEEK and talc or zinc oxide as preferred optional filler materials. Preferably, the filler material has a D50 between 0.001 to 50 m, 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 (ISO 13320-1).

The polymer material (B) comprising a filler material may be prepared by any suitable method known in the art. For example, said material may be prepared by single or twin-screw extrusion compounding, preferably by twin-screw extrusion compounding.

Suitably the filler material provides improved properties such as improved strength, ductility, heat resistance, chemical resistance. However, for insulated conductors, filler material provides improved electrical resistance to the assembly. For example, the filler material may provide an improvement in dielectric properties and/or electrical breakdown performance.

In a most preferred arrangement, the first extruded layer is located adjacent the die of the extruder assembly. Advantageously, provision of the first extruded layer, substantially free from filler material, minimises the risk of die drool forming at the die exit. As such, the first layer acts to provide a blanket or shield to the second layer. The second layer is therefore protected from the die on exit from the extrusion apparatus. As a result, the insulated conductor of this first aspect suitably has fewer defects caused by die drool. Additionally, the extrusion process is less prone to blockages and so there is less requirement for the process to be stopped for cleaning. This suitably provides a more efficient overall process. The process is equally suitable for the production of other extruded products, such as films, cable outers, filaments and pipes.

Preferably, the second layer is adjacent the wire. Preferably, the second layer is deposited directly on the wire.

Preferably, the first layer is an outer layer. Preferably, the second layer is an inner layer closest to the wire. Preferably, the first extruded layer is located adjacent the second layer.

Furthermore, the present 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 insulated wire coater assembly runs at approximately 10 metres per minute. Advantageously, the present invention provides for line speeds of approximately 50 metres per minute. The line speed may be greater than 50 metres per minute, for example up to 100 metres per minute, preferably between 30 and 80 metres per minute, preferably between 40 and 60 meters per minute.

The present invention may also 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.

Such co-extrusion with an unfilled PAEK material adjacent a filled PAEK material allows for higher weight content of fillers to be used, with the added potential to operate coextrusion manufacturing lines at higher line speeds thus enabling higher production rates.

If highly filled compounds could be coated onto wire (without the process issues indicated above) it is believed that a thinner coating with higher levels of filler could achieve the same level of electrical performance as a thicker coating where only low amounts of filler material were previously possible.

Reducing the total thickness an insulating layer around a conductor (whilst maintaining electrical and mechanical performance) will allow design engineers to save space and/or increase the amount of conductor within the stator of an electric motor. A reduced coating thickness may also help with heat dissipation from the motor.

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 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 typically 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, preferably the second layer is arranged between the first layer and the third layer. A plurality of material layers may be provided in a multi coextrusion process.

The first layer and the second layer of the extruded product may have a combined thickness of at least 100pm, for example between 150 and 190 pm. The combined thickness may be up to 300 pm.

The thickness of the first layer is suitably less 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 at least one additional extruded layer may be provided. Such layer may comprise an enamel material, or a release agent which may be selected from metal stearates, erucamide, oleamide or a fluoropolymer.

Preferably, the or each additional layer may be located between the second layer and the wire. Preferably, the or each additional layer may comprise an additive to promote adhesion to the wire. The additive may, for example, be a copolymer of PAEK, for example a PEEK/PEDEK as described in EP 3013888. Advantageously, provision of such additional layer/s negates the need for pre-treatment of the wire. For example, wire would typically require plasma pretreatment.

In an alternative embodiment, the insulated electrical conductor comprises a first outer layer of polymeric material (A), an inner layer of polymeric material (B) as the second layer and a further outer layer of polymeric material (A) as a 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 sheath. The wire sheath may be extruded directly onto a wire to form the insulated conductor assembly. Advantageously, due to the second layer comprising the filler material, increased electrical insulation to the second layer is achieved and therefore to the assembly as a whole. 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.

The electrical conductor is preferably essentially copper or aluminium, although the present invention is applicable to a wide range of electrical conductor materials. When the conductor is copper it is preferably a low oxygen copper with an oxygen content of less than 30 ppm, more preferably less than 20 ppm.

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

wherein t1 and wl independently represent 0 or 1 and v1 represents 0, 1 or 2, together with a filler material, wherein said second layer is located between the core and the first layer.

According to a further aspect of the present invention, there is provided a method of producing extruded product assembly 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 I:

wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2; b) providing a source of a second polymeric material (B) having a repeat unit of formula I;

wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2, together with a filler material; c) delivering the polymeric material (A) and the second polymeric material (B) to an extruding station comprising a die; d) extruding the polymeric material (A) and the second polymeric material (B) through the die, such that the polymeric material (A) contacts an exit of the die during extrusion and the second polymeric material (B) does not contact the die during extrusion, to form the extruded product assembly.

Most preferably, the extruded product assembly is an insulated conductor assembly.

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 (B) are arranged such that the second polymeric material (B) 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 any one of the aforementioned aspects.

The method of this aspect suitably causes a reduced amount of die drool compared with a comparable process wherein the second polymeric material (B) 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.

The method of this 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 (B) in molten form to the extrusion die such that the second polymeric material (B) 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 (B) 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.

Preferably, the first layer is introduced at a first position in the die assembly, preferably said first position is remote from the exit end of the die. Preferably, the second layer is introduced at a second position. Preferably, the second position is located downstream of the first position. Preferably, the third layer is introduced at a third position in the die assembly. Preferably, the third position is different to the first or the second position. Preferably, the third position is downstream of the second position. Preferably, the third position is located towards the exit end of the die. Preferably, each subsequent layer is introduced in an equidistantly spaced location on the die assembly.

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 further 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 at least a second polymeric material (B); wherein the polymeric material (A) has a repeat unit of formula I:

and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2 (Formula I); and the second polymeric material (B) has a repeat unit of formula 1 :

and wl independently represent 0 or 1 and vl represents 0, 1 or 2, together with a filler material. According to a further aspect of the present invention, there is provided an insulated conductor assembly comprising: a conductor wire; a first extruded layer and a second extruded layer; said first layer comprising a polymeric material (D) 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; and said second layer comprising: a polymeric material (B) having a repeat unit of Formula I

wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2, together with a filler material, wherein said second layer is located between the wire and the first layer.

By extruded layer we mean a layer 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 polymeric material (D) is a polyaryletherketone (PAEK) polymer. More specifically, the polymeric material (D) 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 (D) may be referred to as a PEEK/PEDEK copolymer. Suitable polymeric materials of formula (D) (PEEK/PEDEK copolymers) are as described in US4717761 , WO2014/207458A1 and WO2015/124903A1 , the contents of which are incorporated herein by reference.

WO 2014/207458A1 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 Il 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.

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 1a is a schematic of an extrusion die for producing an insulated conductor assembly of the present invention;

Figure 1 b is a schematic cross section of an insulated conductor assembly produced by the extrusion process of Figure 1a;

Figure 2a is a schematic of an alternative extrusion die for producing an insulated conductor assembly of the present invention;

Figure 2b is a schematic cross section of an alternative embodiment of an insulated conductor assembly produced by the extrusion process of Figure2a;

Figure 3a is a schematic of an alternative extrusion die for producing an insulated conductor assembly of the present invention;

Figure 3b is a schematic cross section of an insulated conductor assembly produced by the extrusion process of Figure 3a;

Figure 4a is a schematic of an extrusion die for producing an extruded product of an embodiment 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 an alternative aspect of the present invention in the form of a film using a method according to an 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 according to an aspect of the present invention in the form of a filament using a method according to an aspect of the present invention; and

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 insulated conductor assembly 120 in a “pressure on” extrusion process. The extrusion die 100 comprises a die body 1 and a die mandrel 2.

The die 100 comprises a first channel 101 for delivering a first extruded layer, a second channel 102 for delivering a second extruded layer, a wire 103, a die exit 110, and a die entrance 111. The first channel 101 is located at a first position 122 downstream of the die entrance 111. The first channel 101 is configured to deliver the first polymer material (A) in molten form into the die 100, such that the polymer material (A) flows through the die in a direction substantially parallel to the direction of the wire 103, to provide an extruded first jacket 126 of PAEK material. The second channel 102 is located at a second position 124 upstream of the first position 122 and nearest to the die entrance 111. The second channel 102 is configured to deliver the molten second polymer material (B) into the die 100, such that the polymer material (B) flows through the die in a direction substantially parallel to the direction of the wire 103. In use, the second polymer (B) enters the die and coats the wire 103, forming an extruded second jacket 128 of PAEK plus filler material. The extruded first jacket 126 is coextruded over the said second jacket 128 as shown most clearly in Figure 1 b.

The formation of this extruded insulated conductor assembly 120 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, due to polymer material A being substantially free from filler material. The first jacket 126 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, 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 comprising a die body 1 and die mandrel 2. The die 200 having a first channel 201 , a second channel 202, a third channel 233, and a die exit 210. A wire 203 is fed through the die 200 to form a core of the insulated conductor assembly. In this embodiment, the third channel 233 is located between the first and second channels 201 , 202. The third channel 233 is configured to deliver a further material into the die assembly. The third material is preferably a molten polymer material. Specifically, 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 extruded jackets 228, 236, 226 arranged coaxially around wire 3 as shown in Figure 2b.

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 filler which 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 203 than would otherwise be achieved if polymeric material C contacted the wire 203 directly.

Alternatively, channel 202 may deliver a material that has adhesive characteristics that negate the need for the wire to undergo a pre-treatment. For example, channel 202 may deliver a copolymer of PAEK.

As described above in relation to Figure 1a, 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, 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 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 for example, a wire 303. A first outer layer of polymer material A is introduced through a first channel 301 (i.e. the first layer), a polymer material B is introduced through a second channel 302 (i.e. the second layer), and a further outer layer comprising polymer material A is introduced through a further channel 313 (i.e. the third layer). The coating of the wire or cable 303 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), comprising 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 to demonstrate the reduction in die drool obtainable according to 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 PEEK/PEDEK copolymer material, herein referred to under the trade mark 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 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 6x the 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 marked difference in production of die drool between a filled PEEK (Example 1.1) and unfilled PEEK or PEEK/PEDEK material. There is 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 unfilled PEEK material. 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 - Insulated Wire Single Layer

Coated wires suitable as insulated conductor wire, were formed by extruding the polymeric materials described in Table 2 above, as a 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

The coated wires suitable as insulated conductor wire 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 crosssection. 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 unfilled PEEK on a wire more readily prevents die drool formation when compared to filled PEEK. 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 PEEK material shows die drool forms more quickly.. Therefore, the use of unfilled PEEK, or 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.

There is a drive in the field of insulated conductors to use filled, for example talc filled, PAEK solutions in order to achieve, for example, the desired breakdown voltage. Therefore, the following example, demonstrates an embodiment of the present invention that addresses die drool while also taking into account the desire for filled PAEK material in the field of high voltage wire applications. Example 3 - Insulated Wire Multiple Layer

Example 3 is an example of an extruded wire suitable as an insulated conductor assembly according to the present invention. In particular, such wire is particularly advantageous in high voltage application. Such wire is particularly favourable in e-motor type applications.

The conductor assembly, having an inner layer and outer layer coating of polymeric material as illustrated in Figures 1a and 1 b, was formed by extruding the polymeric materials noted in Table 4 below as the outer and inner layers onto a copper wire. 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 wires were extruded through a clean extrusion die, as described above in relation to Figures 1a 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

Example 5.2 having an outer layer of unfilled PEEK in contact with the die, and a PEEK plus talc filled inner layer shows a significant improvement in die drool when compared against Example 5.1 having both layers of PEEK plus filler.

Example 5.3 having an outer layer of PEEK/PEDEK copolymer contacting 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 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 an outer layer of unfilled PAEK or alternatively 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.

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 insulated conductor assembly comprising a conductor wire, a first extruded layer and a second extruded layer; said first layer comprising: a polymeric material (A) having a repeat unit of formula I

(Formula I) wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2; and said second layer comprising: a polymeric material (B) having a repeat unit of formula I

(Formula I) wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2, togetherwith a filler material, wherein said second layer is located between the wire and the first layer.

2. An assembly as claimed in claim 1 , wherein thejDolymeric material (A) comprises at least at least 80 wt% of PAEK polymer.

3. An assembly as claimed in claim 2, wherein the polymeric material (A) is substantially at least 99wt% PAEK.

4. An assembly as claimed in any one of the preceding claims, wherein the second layer comprises at least 50 wt% of the polymeric material (B).

5. An assembly as claimed in any one of the preceding claims wherein polymeric material (A) and/or (B) is polyether ether ketone (PEEK).

6. An assembly as claimed in any one of the preceding claims, wherein the first layer consists essentially of PEEK, and the second layer consists essentially of polymeric material (B) being PEEK and filler material.

7. An assembly as claimed in any one of the preceding claims, wherein the polymeric material (A) and/or polymeric material (B) has a crystallinity of at least 20%.

8. An assembly as claimed in any one of the preceding claims, wherein the filler material is a particulate filler material.

9. An assembly as claimed in claim 8, wherein the filler material is either talc or zinc oxide.

10. An assembly as claimed in any one of the preceding claims, wherein the filler material comprises at least 15wt% of polymeric material (B).

11. An assembly as claimed in any one of the preceding claims, wherein the filler material has a D50 between 1 and 5 pm as measured by laser Mastersizer laser diffraction, Mie theory (ISO 13320-1).

12. An assembly as claimed in any one of the preceding claims wherein the first extruded layer is located adjacent the die of the extruder assembly.

13. An assembly as claimed in any one of the preceding claims, wherein the second layer is adjacent the wire.

14. An assembly as claimed in any one of the preceding claims, wherein the first extruded layer is located adjacent the second layer.

15. An assembly as claimed in any one of the preceding claims wherein an additional layer is provided, the additional layer comprising an enamel layer and/or a further polymer layer, e.g. a thermoset polymer layer e.g. a fluoropolymer or polyimide layer.

16. An assembly as claimed in any one of the preceding claims wherein the first layer and the second layer of the extruded product have a combined thickness of up to 300 pm.

17. An extruded product assembly comprising a core, a first extruded layer and a second extruded layer; said first layer comprising: a polymeric material (A) having a repeat unit of formula I

wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or2, togetherwith a filler material, wherein said second layer is located between the core and the first layer.

18. An insulated conductor assembly comprising a conductor wire, a first extruded layer and a second extruded layer; said first layer comprising: a polymeric material (D) 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, and said second layer comprising: a polymeric material (B) having a repeat unit of formula

wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2, togetherwith a filler material, wherein said second layer is located between the wire and the first layer.

19. A method of producing extruded product assembly 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 I:

wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or2, togetherwith a filler material; c) delivering the polymeric material (A) and the second polymeric material (B) to an extruding station comprising a die; d) extruding the polymeric material (A) and the second polymeric material (B) through the die, such that the polymeric material (A) contacts an exit of the die during extrusion and the second polymeric material (B) does not contact the die during extrusion, to form the extruded product assembly.

20. A method as claimed in claim 19, wherein the extruded product assembly is an insulated conductor assembly.

21. A method as claimed in claims 19 or 20, wherein the inputs and extrusion of the polymeric material (A) and the second polymeric material (B) are arranged such that the second polymeric material (B) 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.

22. A method as claimed in any one of claims 19 to 21 , wherein the first layer is introduced at a first position in the die assembly, said first position being remote from the exit end of the die.

23. A method as claimed in any of claims 19 to 22, wherein the second layer is introduced at a second position, the second position being located downstream of the first position.

24. Use of a polymeric material (A) or (D) for reducing the formation of deposits on a die of an extrusion apparatus during extrusion of at least a second polymeric material (B); wherein the polymeric material (A) has a repeat unit of formula I:

t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2; or a polymeric material (D) having a repeat unit of formula:

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

-O-Ph-Ph-O-Ph-CO-Ph- II wherein Ph represents a phenylene moiety; and the second polymeric material (B) has a repeat unit of formula 1 :

t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2, together with a filler material.

25. An electrical device comprising the insulated conductor according to any one of claims 1 to 18.

26. A motor or stator coil having the insulated conductor according to any one of claims 1 to 18.